Publications by authors named "Angela Rosa"

37 Publications

Bis(CBT)palladium(II) Derivatives (CBT = -carborane-1-thiolate): Synthesis, Molecular Structure, and Physicochemical Properties of -[(bipy)Pd(CBT)] and -[(py)Pd(CBT)].

Inorg Chem 2021 Jul 6;60(14):10478-10491. Epub 2021 Jul 6.

Dipartimento di Scienze, Università della Basilicata, Viale dell'Ateneo Lucano 10, I-85100 Potenza, Italy.

The new synthesized Pd complex -[(bipy)Pd(CBT)] (bipy = 2,2'-bipyridyl; CBT = -carborane-1-thiolate anion), which is a potential BNCT (boron neutron capture therapy) agent and of structure elucidated by single-crystal X-ray work, has been studied by infrared (IR) and ultraviolet-visible light (UV-vis) spectra and its properties compared with those of the previously reported and also the structurally characterized analogue -[(py)Pd(CBT)]. This species, prepared via a direct method, was previously isolated from a pyridine solution, consequent to the occurring releasing of the external Pd(CBT) moieties of the porphyrazine macrocycle [{Pd(CBT)}LZn]·HO (L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato anion), which is an active photosensitizer in photodynamic therapy (PDT) and a potential bimodal PDT/BNCT agent. The UV-vis spectral behavior of both and species in CHCl solution and in the gas phase has been examined in detail by density functional theory (DFT) and time-dependent density functional theory (TDDFT) studies devoted to explain their distinct behavior observed in the region of 400-500 nm, as determined by the presence in the structure of a vicinal arrangement of the two CBT groups, an ensemble of results closely similar to those observed for the macrocycles [{Pd(CBT)}LM]·HO (M = Mg(HO), Zn, Pd). It has also been experimentally proved the tendency of the isomer in CHCl/pyridine solution to be changed to the respective analogue, with conversion occurring in two steps, as interpreted by detailed DFT studies.
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http://dx.doi.org/10.1021/acs.inorgchem.1c01092DOI Listing
July 2021

Towards Selection Charts for Epoxy Resin, Unsaturated Polyester Resin and Their Fibre-Fabric Composites with Flame Retardants.

Materials (Basel) 2021 Mar 3;14(5). Epub 2021 Mar 3.

Design and Production Engineering Department, Ain Shams University, Abbassia, Cairo 11517, Egypt.

Epoxy and unsaturated polyester resins are the most used thermosetting polymers. They are commonly used in electronics, construction, marine, automotive and aircraft industries. Moreover, reinforcing both epoxy and unsaturated polyester resins with carbon or glass fibre in a fabric form has enabled them to be used in high-performance applications. However, their organic nature as any other polymeric materials made them highly flammable materials. Enhancing the flame retardancy performance of thermosetting polymers and their composites can be improved by the addition of flame-retardant materials, but this comes at the expense of their mechanical properties. In this regard, a comprehensive review on the recent research articles that studied the flame retardancy of epoxy resin, unsaturated polyester resin and their composites were covered. Flame retardancy performance of different flame retardant/polymer systems was evaluated in terms of Flame Retardancy index (FRI) that was calculated based on the data extracted from the cone calorimeter test. Furthermore, flame retardant selection charts that relate between the flame retardancy level with mechanical properties in the aspects of tensile and flexural strength were presented. This review paper is also dedicated to providing the reader with a brief overview on the combustion mechanism of polymeric materials, their flammability behaviour and the commonly used flammability testing techniques and the mechanism of action of flame retardants.
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http://dx.doi.org/10.3390/ma14051181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7959149PMC
March 2021

Origin of the Enhanced Binding Capability toward Axial Nitrogen Bases of Ni(II) Porphyrins Bearing Electron-Withdrawing Substituents: An Electronic Structure and Bond Energy Analysis.

Inorg Chem 2020 Aug 29;59(16):11528-11541. Epub 2020 Jul 29.

Università della Basilicata, Dipartimento di Scienze, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.

Axial coordination to metalloporphyrins is important in many biological and catalytic processes. Experiments found the axial coordination of nitrogenous bases to nickel(II) porphyrins to be strongly favored by electron-withdrawing substituents such as perfluorophenyls at the meso carbon positions. Careful analysis of the electronic structure reveals that the natural explanation in terms of density change of the nickel(II) porphyrin system (in particular the metal), does not apply. Electron density changes, by the assumed inductive or polarizing effects on the metal or on the porphyrin ring system, are slight. The effect is caused by a remarkable through-space electric field effect on the metalloporphyrin system, originating from the charge distribution inside the perfluorphenyl groups (mostly the C-F dipoles).
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http://dx.doi.org/10.1021/acs.inorgchem.0c01327DOI Listing
August 2020

Evaluation of left ventricular dimension and systolic function by standard transthoracic echocardiography before and 24-hours after percutaneous closure of patent ductus arteriosus in 120 dogs.

PLoS One 2019 9;14(10):e0223676. Epub 2019 Oct 9.

Clinica Veterinaria Gran Sasso, Milano, Italy.

One hundred and twenty dogs were enrolled to value the effect of loading condition changes on left ventricular volumes before and 24-hours after the patent ductus arteriosus (PDA) occlusion by Amplatzer Canine Duct Occluder (ACDO) using standard echocardiography. The animals were divided in pure breed (n. 94) and mixed breed (n. 26); subsequently, the pure breed dogs were divided on the basis of the size of the breed of belonging in 3 groups (small size n. 36; medium size n. 8; large size n. 50). Moreover, the animals were divided in three classes based on their age: until 6 months; 6-12 months; over 12 months. A significant reduction of all the examined parameters (left ventricle internal diameter at end-diastole-LVIDd; left ventricle internal diameter at end-systole-LVIDs; end-diastolic volume-EDV; end-systolic volume-ESV; end-diastolic volume index-EDVI; end-systolic volume index-ESVI; fractional shortening-FS) was observed after ductal closure. Twenty-four hours after the closure, the evaluation of the relative percentage difference (RPD) of the echocardiographic parameters showed a significant reduction, higher in small size breed than in large size breed dogs. No significant difference related to breed size was observed only for RPD_FS variable. A significant interaction effect, between breed size and age classes, was observed only for RPD_EDVI (F = 3.39; p = 0.039). Until six months of age there was no significant difference in RPD_EDVI reduction, but over 6 months a significant reduction between small size and large size breed dogs at 24-hours from the occlusion was observed. In conclusion, our data seem to indicate that small breed dogs show a greater tolerance to congenital volume overload than large breed dogs, and this finding could be justify a delay of PDA closure in order to simplify the interventional procedure.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223676PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6785069PMC
March 2020

Innovative Chemical Process for Recycling Thermosets Cured with Recyclamines by Converting Bio-Epoxy Composites in Reusable Thermoplastic-An LCA Study.

Materials (Basel) 2018 Feb 28;11(3). Epub 2018 Feb 28.

Department of Civil Engineering and Architecture and INSTM UdR, University of Catania, Viale A. Doria 6, 95125 Catania, Italy.

An innovative recycling process for thermoset polymer composites developed by Connora Technologies (Hayward, CA, USA) was studied. The process efficacy has already been tested, and it is currently working at the plant level. The main aspect investigated in the present paper was the environmental impact by means of the Life Cycle Assessment (LCA) method. Because of the need to recycle and recover materials at their end of life, the Connora process creates a great innovation in the market of epoxy composites, as they are notoriously not recyclable. Connora Technologies developed a relatively gentle chemical recycling process that induces the conversion of thermosets into thermoplastics. The LCA demonstrated that low environmental burdens are associated with the process itself and, furthermore, impacts are avoided due to the recovery of the epoxy-composite constituents (fibres and matrix). A carbon fibre (CF) epoxy-composite panel was produced through Vacuum Resin Transfer Moulding (VRTM) and afterwards treated using the Connora recycling process. The LCA results of both the production and the recycling phases are reported.
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http://dx.doi.org/10.3390/ma11030353DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872932PMC
February 2018

Green Composites Based on Blends of Polypropylene with Liquid Wood Reinforced with Hemp Fibers: Thermomechanical Properties and the Effect of Recycling Cycles.

Materials (Basel) 2017 Aug 26;10(9). Epub 2017 Aug 26.

Institute of Polymer Materials and Plastics Engineering, Clausthal University of Technology, Agricolastr. 6, Clausthal-Zellerfeld 38678, Germany.

Green composites from polypropylene and lignin-based natural material were manufactured using a melt extrusion process. The lignin-based material used was the so called "liquid wood". The PP/"Liquid Wood" blends were extruded with "liquid wood" content varying from 20 wt % to 80 wt %. The blends were thoroughly characterized by flexural, impact, and dynamic mechanical testing. The addition of the Liquid Wood resulted in a great improvement in terms of both the flexural modulus and strength but, on the other hand, a reduction of the impact strength was observed. For one blend composition, the composites reinforced with hemp fibers were also studied. The addition of hemp allowed us to further improve the mechanical properties. The composite with 20 wt % of hemp, subjected to up to three recycling cycles, showed good mechanical property retention and thermal stability after recycling.
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http://dx.doi.org/10.3390/ma10090998DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615653PMC
August 2017

Efficacy of a polyvalent mastitis vaccine against Staphylococcus aureus on a dairy Mediterranean buffalo farm: results of two clinical field trials.

BMC Vet Res 2017 Jan 19;13(1):29. Epub 2017 Jan 19.

Department of Veterinary Medicine and Animal Productions, University of Napoli "Federico II", Via Delpino 1, 80137, Naples, Italy.

Background: In the last years the knowledges on Mediterranean Buffalo (MB) mastitis is remarkably improving, nevertheless the attention has been never focused on vaccination as preventive strategy for the control of mastitis in these ruminates. The aim of the current study was to assess clinical efficacy over time of two different preventive vaccination protocols against S. aureus mastitis, in primiparous MB.Vaccinated (VG) and not-vaccinated (N-VG) groups, of 30 MB each one, were selected from two different herds (herd A: VG1 and N-VG1; herd B: VG2 and N-VG2) of the same farm. Herd A received a double vaccination (Startvac®, 45 and 10 days before calving, protocol A), while in herd B an additional administration was performed (52 days after calving, protocol B). Bacteriological milk culture and assessment of somatic cell count (SCC) were performed at 10, 30, 60 and 90 days in milk (DIM) from composite milk samples. After 90 DIM, daily milk yields and SCC values were monthly detected until dry-off.

Results: The overall incidence of positive MB for S. aureus was 40.8% (49/120) in VG1 and 43.3% (52/120) in N-VG1 (Protocol A), while 45.8% (55/120) and 50.8% (61/120) in VG2 and N-VG2 (Protocol B). The latter was associated with a significant decreased in prevalence (at 90 DIM) and incidence of mastitis (animals positive for S. aureus, SCC > 200^10, with or without clinical signs) in the vaccinated MB, while no difference occurred in protocol A. Moreover, herd B showed a significant reduction in prevalence of intramammary infection (animals positive for S. aureus, SCC < 200^10, no clinical signs) in the vaccinated MB at 60 DIM while no differences were detected in herd A, at any sampling time; N-VG2 had significantly higher overall SCC values than VG2 (4.97 ± 4.75 and 4.84 ± 4.60 Log10 cells/mL ± standard deviation, respectively), while no differences were recorded in herd A.

Conclusions: The current investigation explores for the first time the clinical efficacy of vaccinations against S. aureus infections in MB, showing encouraging results regarding reduction in mastitis and somatic cell count; the polyvalent mastitis vaccine may be considered an additional tool for in-herd S aureus infection and should be associated to other control procedures to maximize its properties.
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http://dx.doi.org/10.1186/s12917-017-0944-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5248485PMC
January 2017

Serum biochemistry profile, inflammatory cytokines, adipokines and cardiovascular findings in obese dogs.

Vet J 2016 Oct 5;216:72-8. Epub 2016 Jul 5.

Department of Veterinary Medicine and Animal Productions, University of Naples 'Federico II', via F. Delpino 1, 80137 Naples, Italy.

The aim of this study was to evaluate the serum biochemistry profile, inflammatory cytokines, adipokines and cardiovascular findings in obese dogs. Twenty obese and 20 normal weight healthy pet dogs were recruited into the study, where they underwent blood testing and assessment of cardiovascular function (blood pressure analysis, electrocardiography and echocardiography). Higher concentrations of total cholesterol, triglycerides, lactate dehydrogenase, total serum proteins, α-globulins, total bilirubin, insulin, insulin:glucose ratio, alkaline phosphate and alanine aminotransferase were observed in obese dogs than dogs of normal weight. There were no differences in concentrations of tumour necrosis factor (TNF)-α or interleukin (IL)-6 between the two groups. Obese dogs had higher serum leptin but lower adiponectin concentrations than dogs of normal weight. Systolic arterial blood pressure was higher in obese dogs than dogs of normal weight. The values for the thickness of the free wall of the left ventricle and interventricular septal thickness were greater at end-diastole in obese dogs compared to dogs of normal weight. Four of 20 obese dogs were determined to have obesity-related metabolic dysfunction (ORMD). The findings indicate that a chronic inflammatory state is not necessarily evident in obese dogs, as has been described in human beings, and the criteria used for ORMD can be used to define this syndrome in dogs. In this study, canine obesity was associated with cardiac and vascular dysfunction.
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http://dx.doi.org/10.1016/j.tvjl.2016.07.002DOI Listing
October 2016

Assessment of foot health and animal welfare: clinical findings in 229 dairy Mediterranean Buffaloes (Bubalus bubalis) affected by foot disorders.

BMC Vet Res 2016 Jun 14;12(1):107. Epub 2016 Jun 14.

Clinic for Ruminants, Department of Clinical Veterinary Medicine, Vetsuisse-Faculty, University of Berne, 3012, Bern, Switzerland.

Background: Lameness represents the third most important health-related cause of economic loss in the dairy industry after fertility and mastitis. Although, dairy Mediterranean Buffaloes (MB) and dairy cows share similar breeding systems predisposing to similar herd problems, published studies exploring its relevance and role in these ruminants are still rare and incomplete. The aims of this study were to describe the clinical findings of foot disorders (FDs) in dairy MB and their influence on animal welfare, determined by assessment of locomotion score (LS), body condition score (BCS) and cleanliness score (CS).

Results: Of 1297 multiparous MB submitted to routine trimming procedures, 229 buffaloes showed at least one FD. The prevalence of buffaloes affected by FDs was 17.7 %, while motility and lameness indexes were 84.1 % (1091/1297) and 15.9 % (206/1297), respectively. Overgrowth was present in 17.0 % (220/1297), corkscrew claw in 15.8 % (205/1297), interdigital phlegmon in 0.9 % (12/1297), white line abscess in 0.8 % (11/1297), digital dermatitis in 0.1 % (1/1297) and interdigital hyperplasia in 0.1 % (1/1297). Simultaneous presence of FDs was recorded in 17.0 % of MB (221/1297): overgrowth and corkscrew claw occurred together in 15.8 % of cases (205/1297), overgrowth and interdigital phlegmon in 0.3 % (4/1297), overgrowth and white line abscess in 0.8 % (11/1297), digital dermatitis and interdigital hyperplasia in 0.1 % (1/1297). The presence of FDs was always associated with lameness (LS > 2), except from 23 MB with simultaneous overgrowth and interdigital phlegmon occurrence. The majority of MB within the under-conditioned group (95.5 %, 43/45) and all those with CS > 2 (122/122) had a locomotion score above the threshold of normality (LS > 2). Furthermore, foot diseases such as interdigital hyperplasia, white line abscess and digital dermatitis or interdigital hyperplasia seemed to occur more frequently associated with decreased BCS and increased CS scores.

Conclusions: This study describes for the first time the involvement of white line disease, interdigital phlegmona, digital dermatitis and interdigital hyperplasia in foot disorders of dairy Mediterranean buffalo and shows their association with an impairment of animal welfare.
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http://dx.doi.org/10.1186/s12917-016-0726-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4906600PMC
June 2016

Water-soluble carboranyl-phthalocyanines for BNCT. Synthesis, characterization, and in vitro tests of the Zn(II)-nido-carboranyl-hexylthiophthalocyanine.

Dalton Trans 2015 Jun 21;44(24):11021-8. Epub 2015 May 21.

Dipartimento di Scienze, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.

The zinc(II) complex of the octa-anionic 2,3,9,10,16,17,23,24-octakis-(7-methyl-7,8-dicarba-nido-undeca-boran-8-yl)hexyl-thio-6,13,20,27-phthalocyanine (nido-[ZnMCHESPc]Cs8, 7) has been obtained in the form of caesium salt through mild deboronation of the neutral precursor, the closo-[ZnMCHESPc] complex, 6, with CsF. 6 has been synthesized, in turn, by heating a finely ground mixture of the appropriate phthalonitrile and zinc(II) acetate at 180.0 °C. The complexes have been characterized by elemental analyses, FT-IR, UV-visible absorption and fluorescence emission spectroscopy, and their structures were assessed by (1)H, (13)C, (11)B, and two-dimensional homo- and hetero-correlated NMR spectroscopy experiments. 7 showed appreciable solubility in water solution, together with a marked tendency to aggregate. Aggregation of 7 in the hydrotropic medium resulted in significant fluorescence quenching. Instead, fluorescence quantum yields (Φ(F)) of 0.14 and 0.08, and singlet oxygen quantum yields (Φ(Δ)) of 0.63 and 0.24 were obtained for 6 and 7, respectively, in a DMF solution. In vitro boron neutron capture therapy (BNCT) experiments, employing boron imaging techniques as implemented in qualitative and quantitative neutron autoradiography methods, showed that 7 is capable of increasing the boron concentration of two selected cancerous cell lines, the DHD/K12/TRb of rat colon adenocarcinoma and UMR-106 of rat osteosarcoma, with the large-size Cs(+) counter-ions used to neutralize the negatively charged carborane polyhedra not presenting a significant obstacle to the process. Taken together, BNCT and photophysical measurement results indicated that 7 is potentially suitable for bimodal or multimodal anticancer therapy.
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http://dx.doi.org/10.1039/c5dt00394fDOI Listing
June 2015

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 15. Effects of the pyridyl substituents and fused exocyclic rings on the UV-visible spectroscopic properties of Mg(II)-porphyrazines: a combined experimental and DFT/TDDFT study.

Inorg Chem 2014 Aug 24;53(15):8009-19. Epub 2014 Jul 24.

Dipartimento di Chimica, Università di Roma Sapienza , Piazzale A. Moro 5, I-00185 Roma, Italy.

Two new Mg(II) porphyrazine macrocycles, the octakis(2-pyridyl)porphyrazinato-magnesium(II), [Py8PzMg(H2O)], and the tetrakis-[6,7-di(2-pyridyl)quinoxalino]porphyrazinato-magnesium(II), [Py8QxPzMg(H2O)], were prepared by Mg-template macrocyclization processes, and their general physicochemical properties were examined. The previously reported porphyrazine analog, the tetrakis-2,3-[5,6-di(2-pyridyl)-pyrazino]porphyrazinato-magnesium(II), [Py8PyzPzMg(H2O)], has been also considered in the present work. The UV-visible solution spectra in nonaqueous solvents of this triad of externally octapyridinated Mg(II) complexes exhibit the usual profile observed for phthalocyanine and porphyrazine macrocycles, with intense absorptions in the Soret (300-450 nm) and Q band (600-800 nm) regions. It is observed that the Q band maximum sensibly shifts toward the red with peak values at 635 → 658 → 759 nm along the series [Py8PzMg(H2O)], [Py8PyzPzMg(H2O)], and [Py8QxPzMg(H2O)], as the extension of the macrocycle π-system increases. TDDFT calculations of the electronic absorption spectra were performed for the related water-free model compounds [Py8PzMg], [Py8PyzPzMg], and [Py8QxPzMg] to provide an interpretation of the UV-visible spectral changes occurring upon introduction of the pyrazine and quinoxaline rings at the periphery of the Pz macrocycle. To discriminate the electronic effects of the fused exocyclic rings from those of the appended 2-pyridyl rings, the UV-visible spectra of [PzMg] and [PyzPzMg] were also theoretically investigated. The theoretical results prove to agree very well with the experimental data, providing an accurate description of the UV-visible spectra. The observed spectral changes are interpreted on the basis of the electronic structure changes occurring along the series.
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http://dx.doi.org/10.1021/ic500880mDOI Listing
August 2014

Phenyl derivative of iron 5,10,15-tritolylcorrole.

Inorg Chem 2014 Apr 3;53(8):4215-27. Epub 2014 Apr 3.

Department of Chemical Science and Technologies, Università di Roma Tor Vergata , 00133 Roma, Italy.

The phenyl-iron complex of 5,10,15-tritolylcorrole was prepared by reaction of the starting chloro-iron complex with phenylmagnesium bromide in dichloromethane. The organometallic complex was fully characterized by a combination of spectroscopic methods, X-ray crystallography, and density functional theory (DFT) calculations. All of these techniques support the description of the electronic structure of this phenyl-iron derivative as a low-spin iron(IV) coordinated to a closed-shell corrolate trianion and to a phenyl monoanion. Complete assignments of the (1)H and (13)C NMR spectra of the phenyl-iron derivative and the starting chloro-iron complex were performed on the basis of the NMR spectra of the regioselectively β-substituted bromo derivatives and the DFT calculations.
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http://dx.doi.org/10.1021/ic5003572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4002138PMC
April 2014

Pyrazinoporphyrazines with externally appended pyridine rings. 13. Structure, UV-visible spectral features, and noncovalent interaction with DNA of a positively charged binuclear (Zn(II)/Pt(II)) macrocycle with multimodal anticancer potentialities.

Inorg Chem 2013 Jan 17;52(1):321-8. Epub 2012 Dec 17.

Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, via Gobetti 101, I-40129 Bologna, Italy.

We investigated with spectroscopic techniques the noncovalent interaction of a bimetallic water-soluble (Zn(II)/Pt(II)) porphyrazine hexacation, [(PtCl(2))(CH(3))(6)LZn](6+), and its octacationic analogue [(CH(3))(8)LZn](8+), lacking the cis-platin-like functionality, with a 21-mer double strand (ds) 5'-d[GGG(TTAGGG)(3)]-3'/3'-d[CCC(AATCCC)(3)]-5', as model for B-DNA. Both hexacation and octacation tend to aggregate in water. The structure as well as the ground and excited-state electronic properties of the Zn(II)/Pt(II) hexacation [(PtCl(2))(CH(3))(6)LZn](6+) in water solution were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. TDDFT calculations of the lowest excited states of [(PtCl(2))(CH(3))(6)LZn](6+) in water provided an accurate description of the Q-band spectral region. In particular, the calculated optical spectra were in agreement with the experimental ones, obtained in the presence of micelles favoring complete disruption of the aggregates. The model for dsDNA binding that emerges from the analysis of UV-vis absorption and time-resolved fluorescence data shows the presence of complexes of 1 dsDNA molecule with 1, 2, and 4 macrocycles. Comparing the results for the hexacation [(PtCl(2))(CH(3))(6)LZn](6+) with those for the [(CH(3))(8)LZn](8+)octacation, we observed a higher degree of monomerization for the [(PtCl(2))(CH(3))(6)LZn](6+) derivative.
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http://dx.doi.org/10.1021/ic3020755DOI Listing
January 2013

Reactivity of compound II: electronic structure analysis of methane hydroxylation by oxoiron(IV) porphyrin complexes.

Inorg Chem 2012 Sep 4;51(18):9833-45. Epub 2012 Sep 4.

Dipartimento di Chimica, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.

The methane hydroxylation reaction by a Compound II (Cpd II) mimic PorFe(IV)=O and its hydrosulfide-ligated derivative [Por(SH)Fe(IV)=O](-) is investigated by density functional theory (DFT) calculations on the ground triplet and excited quintet spin-state surfaces. On each spin surface both the σ- and π-channels are explored. H-abstraction is invariably the rate-determining step. In the case of PorFe(IV)=O the H-abstraction reaction can proceed either through the classic π-channel or through the nonclassical σ-channel on the triplet surface, but only through the classic σ-mechanism on the quintet surface. The barrier on the quintet σ-pathway is much lower than on the triplet channels so the quintet surface cuts through the triplet surfaces and a two state reactivity (TSR) mechanism with crossover from the triplet to the quintet surface becomes a plausible scenario for C-H bond activation by PorFe(IV)=O. In the case of the hydrosulfide-ligated complex the H-abstraction follows a π-mechanism on the triplet surface: the σ* is too high in energy to make a σ-attack of the substrate favorable. The σ- and π-channels are both feasible on the quintet surface. As the quintet surface lies above the triplet surface in the entrance channel of the oxidative process and is highly destabilized on both the σ- and π-pathways, the reaction can only proceed on the triplet surface. Insights into the electron transfer process accompanying the H-abstraction reaction are achieved through a detailed electronic structure analysis of the transition state species and the reactant complexes en route to the transition state. It is found that the electron transfer from the substrate σ(CH) into the acceptor orbital of the catalyst, the Fe-O σ* or π*, occurs through a rather complex mechanism that is initiated by a two-orbital four-electron interaction between the σ(CH) and the low-lying, oxygen-rich Fe-O σ-bonding and/or Fe-O π-bonding orbitals of the catalyst.
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http://dx.doi.org/10.1021/ic301232rDOI Listing
September 2012

β-Nitro-5,10,15-tritolylcorroles.

Inorg Chem 2012 Jun 5;51(12):6928-42. Epub 2012 Jun 5.

Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, 00133 Roma, Italy.

Functionalization of the β-pyrrolic positions of the corrole macrocycle with -NO(2) groups is limited at present to metallocorrolates due to the instability exhibited by corrole free bases under oxidizing conditions. A careful choice of the oxidant can limit the transformation of corroles into decomposition products or isocorrole species, preserving the corrole aromaticity, and thus allowing the insertion of nitro groups onto the corrole framework. Here we report results obtained by reacting 5,10,15-tritolylcorrole (TTCorrH(3)) with the AgNO(2)/NaNO(2) system, to give mono- and dinitrocorrole derivatives when stoichiometry is carefully controlled. Reactions were found to be regioselective, affording the 3-NO(2)TTCorrH(3) and 3,17-(NO(2))(2)TTCorrH(3) isomers as the main products in the case of mono- and disubstitution, in 53 and 20% yields, respectively. In both cases, traces of other mono- and disubstituted isomers were detected, which were structurally characterized by X-ray crystallography. The influence of the β-nitro substituents on the corrole properties is studied in detail by UV-visible, electrochemical, and spectroelectrochemical characterization of these functionalized corroles. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of the ground and excited state properties of these β-nitrocorrole derivatives also afforded significant information, closely matching the experimental observations. It is found that the β-NO(2) substituents conjugate with the π-aromatic system of the macrocycle, which initiates significant changes in both the spectroscopic and redox properties of the so functionalized corroles. This effect is more pronounced when the nitro group is introduced at the 2-position, because in this case the conjugation is, for steric reasons, more efficient than in the 3-nitro isomer.
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http://dx.doi.org/10.1021/ic3007926DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3381796PMC
June 2012

Symmetrically substituted nido-carboranylphthalocyanines: facile synthesis, characterization, and solution properties. Evidence for intra- and intermolecular H+/K+ exchange.

Inorg Chem 2011 Jun 3;50(11):4680-2. Epub 2011 May 3.

Dipartimento di Chimica, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.

The direct, non ex post synthesis of a novel phthalocyanine decorated with eight thiohexyl-nido-carborane functions, nido-[H(2)MCHESPc]K(8), where the anionic polyhedra are in the form of K(+) salt, is reported and discussed. The solution properties of this compound, including the unprecedented exchange between the pyrrolic protons and the peripheral alkali-metal ions, are also analyzed.
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http://dx.doi.org/10.1021/ic200458kDOI Listing
June 2011

Near-infrared-emitting phthalocyanines. A combined experimental and density functional theory study of the structural, optical, and photophysical properties of Pd(II) and Pt(II) α-butoxyphthalocyanines.

Inorg Chem 2011 Feb 28;50(3):1135-49. Epub 2010 Dec 28.

Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.

The structural, optical, and photophysical properties of 1,4,8,11,15,18,22,25-octabutoxyphthalocyaninato-palladium(II), PdPc(OBu)(8), and the newly synthesized platinum analogue PtPc(OBu)(8) are investigated combining X-ray crystallography, static and transient absorption spectroscopy, and relativistic zeroth-order regular approximation (ZORA) Density Functional Theory (DFT)/Time Dependent DFT (TDDFT) calculations where spin-orbit coupling (SOC) effects are explicitly considered. The results are compared to those previously reported for NiPc(OBu)(8) (J. Phys. Chem. A 2005, 109, 2078) in an effort to highlight the effect of the central metal on the structural and photophysical properties of the group 10 transition metal octabutoxyphthalocyanines. Different from the nickel analogue, PdPc(OBu)(8) and PtPc(OBu)(8) show a modest and irregular saddling distortion of the macrocycle, but share with the first member of the group similar UV-vis spectra, with the deep red and intense Q-band absorption experiencing a blue shift down the group, as observed in virtually all tetrapyrrolic complexes of this triad. The blue shift of the Q-band along the MPc(OBu)(8) (M = Ni, Pd, Pt) series is interpreted on the basis of the metal-induced electronic structure changes. Besides the intense deep red absorption, the title complexes exhibit a distinct near-infrared (NIR) absorption due to a transition to the double-group 1E (π,π*) state, which is dominated by the lowest single-group (3)E (π,π*) state. Unlike NiPc(OBu)(8), which is nonluminescent, PdPc(OBu)(8) and PtPc(OBu)(8) show both deep red fluorescence emission and NIR phosphorescence emission. Transient absorption experiments and relativistic spin-orbit TDDFT calculations consistently indicate that fluorescence and phosphorescence emissions occur from the S(1)(π,π*) and T(1)(π,π*) states, respectively, the latter being directly populated from the former, and the triplet state decays directly to the S(0) surface (the triplet lifetime in deaerated benzene solution was 3.04 μs for Pd and 0.55 μs for Pt). Owing to their triplet properties, PdPc(OBu)(8) and PtPc(OBu)(8) have potential for use in photodynamic therapy (PDT) and are potential candidates for NIR light emitting diodes or NIR emitting probes.
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http://dx.doi.org/10.1021/ic102209qDOI Listing
February 2011

Is [FeO](2+) the active center also in iron containing zeolites? A density functional theory study of methane hydroxylation catalysis by Fe-ZSM-5 zeolite.

Inorg Chem 2010 Apr;49(8):3866-80

Dipartimento di Chimica, Università della Basilica, Via N. Sauro 85, 85100 Potenza, Italy.

Arguments are put forward that the active alpha-oxygen site in the Fe-ZSM-5 catalyst consists of the FeO(2+) moiety. It is demonstrated that this zeolite site for FeO(2+) indeed obeys the design principles for high reactivity of the FeO(2+) moiety proposed earlier: a ligand environment consisting of weak equatorial donors (rather oxygen based than nitrogen based) and very weak or absent trans axial donor. The alpha-oxygen site would then owe its high reactivity to the same electronic structure features that lends FeO(2+) its high activity in biological systems, as well as in the classical Fenton chemistry.
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http://dx.doi.org/10.1021/ic1000073DOI Listing
April 2010

Effect of timing and method of post space preparation on sealing ability of remaining root filling material: in vitro microbiological study.

J Can Dent Assoc 2009 Oct;75(8):583

Universidade Federal do Rio Grande do Sul, Faculdade de Odontologia, Rua Ramiro Barcelos, 2492, Centro, 90035-003 Porto Alegre, RS, Brazil.

Objective: To evaluate the effect of timing (immediate versus delayed) and technique of post space preparation on the ability of the residual root canal obturation to prevent coronal bacterial leakage.

Materials And Methods: Sixty-six single-rooted teeth were decoronated at the cementoenamel junction. The canals were prepared according to a step-back technique and were filled with thermoplasticized gutta-percha and AH Plus endodontic sealer (Dentsply De Trey). The root segments were randomly assigned to 8 groups. The positive controls (n = 3) were instrumented but not obturated. The negative controls (n = 3) were instrumented, obturated and sealed with Cavit (3M ESPE). In the other 6 groups (n = 10 each), the post space was prepared either immediately after obturation or 7 days later using LA Axxess burs (SybronEndo) (groups 1 and 2), heated pluggers (groups 3 and 4) or solvent delivered with a hand file (groups 5 and 6). The external surface of all roots was rendered waterproof with nail varnish. Custom-made dual-chamber devices were used to evaluate leakage. The coronal third of the prepared root canal was kept in contact with artificial saliva contaminated with Enterococcus faecalis, and the root apex was submerged in tryptic soy agar medium. The root assemblies were stored at 37 degrees C and were monitored daily over a 90-day period. The occurrence of turbidity in the medium was deemed to indicate bacterial leakage, from which failure of the seal was inferred.

Results: Throughout the experimental period, there was no significant difference (p = 0.094) among the preparation techniques, either immediate or delayed, in terms of bacterial leakage.

Conclusions: Immediate and delayed post space preparation yielded similar outcomes in terms of the canal seal. Regardless of the timing and the technique of post space preparation, coronal bacterial leakage occurred over time.
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October 2009

Tetrakis(thiadiazole)porphyrazines. 6. Spectroelectrochemical and density functional theory studies of the anions [TTDPzM](n-) (n = 1-4; M = Zn(II), Mg(II)(H(2)O), Cu(II), 2H(I)).

Inorg Chem 2009 Oct;48(20):9890-903

Dipartimento di Chimica, Università degli Studi di Roma La Sapienza, P.le A. Moro 5, Roma, I-00185, Italy.

Following previous cyclic voltammetric studies of tetrakis(thiadiazole)porphyrazines [TTDPzM] where M = Zn(II), Mg(II)(H(2)O), Cu(II), or 2H(I) in nonaqueous media, a thin-layer spectroelectrochemical investigation was carried out in pyridine to characterize each stepwise one-electron reduction of the electrogenerated [TTDPzM](n-) complexes where n = 1-4. A similar UV-visible spectrum was observed for each form of the anion, independent of the central metal ion and detailed theoretical calculations by density functional theory (DFT) and time-dependent DFT (TDDFT) methods were applied to interpret the spectral features of [TTDPzZn](n-) (n = 1-4) which was selected as representative for describing the ground and excited-state electronic structures of the entire [TTDPzM](n-) series. The use of two exchange-correlation functionals, the pure, asymptotically correct statistical average of orbital potentials (SAOP) and the hybrid B3LYP functionals, proved to be essential for attaining a correct assignment of the key spectral features. The nature and intensity of the main spectral features are highlighted and interpreted on the basis of the ground-state electronic structure of the complexes.
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http://dx.doi.org/10.1021/ic9014288DOI Listing
October 2009

Sitting-Atop metallo-porphyrin complexes: experimental and theoretical investigations on such elusive species.

Inorg Chem 2009 Sep;48(17):8493-507

Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, and C.I.R.C.M.S.B., Salita Sperone 31, Vill. S. Agata, Messina, Italy.

The interaction between the sodium cation and two meso-aryl porphyrins (tetraphenylporphyrin, TPP, and tetra(4-methoxyphenyl)porphyrin, TMPP) leads to the formation of new species that have been identified as Sitting-Atop (SAT) complexes, where the metal ion interacts with the N atoms of the porphyrin core without the concomitant deprotonation of the N-H groups. These species have been attained in low polarity solvent through the interaction of the porphyrin free bases with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), and investigated in situ through a combination of spectroscopic techniques, such as UV/vis absorption and fluorescence (static and time-resolved), resonance light scattering, FT-IR, and (1)H NMR. All spectroscopic evidence points to the occurrence of a single equilibrium between each parent compound and its SAT complex, ruling out the presence of other metallo-, protonated, or aggregated porphyrins in solution. The 1:1 stoichiometry of the adducts has been determined via continuous variation method (Job's plot), and an estimate of the corresponding association constants in CH(2)Cl(2) at 298 K have been obtained by UV/vis titration (K(eq) = (9 +/- 4) x 10(5) L mol(-1) and (5 +/- 2) x 10(6) L mol(-1) for TPP and TMPP, respectively). Density-functional theory (DFT) calculations on SAT model complexes, [NaTPP(PF(6))] and [NaTMPP(PF(6))], have provided information on the molecular structure of these elusive species and on the nature and strength of the sodium-porphyrin interaction. It is found that the sodium ion is bound to the four nitrogen atoms of the porphyrin core. The involvement of the pyrrolic N atoms results in a modest but not negligible elongation of the N-H bonds, pyramidalization of the hydrogen atoms, and blue shift of the N-H stretching frequencies. Electronic structure and energy decomposition analysis reveal that covalent interactions, mainly consisting of porphyrin to sodium charge transfer interactions, are an important component of the sodium-porphyrin bond. Time-dependent DFT (TDDFT) calculations of the lowest excited states of the model systems provide an unambiguous interpretation of the absorption and emission properties of the experimentally identified SAT complexes.
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http://dx.doi.org/10.1021/ic9012153DOI Listing
September 2009

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 6. Chemical and redox properties and highly effective photosensitizing activity for singlet oxygen production of penta- and monopalladated complexes in dimethylformamide solution.

Inorg Chem 2008 Oct 10;47(19):8757-66. Epub 2008 Sep 10.

Dipartimento di Chimica, Universita degli Studi di Roma La Sapienza, P.le A. Moro 5, I-00185, Roma, Italy.

Tetrakis-2,3-[5,6-di-(2-pyridyl)pyrazino]porphyrazinatopalladium(II) [Py 8TPyzPzPd] ( 1) and the corresponding pentapalladated species [(PdCl 2) 4Py 8TPyzPzPd] ( 2), dissolved (c approximately 10 (-5)-10 (-6) M) in preacidified dimethylformamide ([HCl] approximately 10 (-4) M), behave as potent photosensitizing agents for the production of singlet oxygen, (1)O 2, with Phi Delta values of 0.89 +/- 0.04 and 0.78 +/- 0.05, respectively. The related octacation [(2-Mepy) 8TPyzPzPd] (8+) ( 3), examined under similar experimental conditions, exhibits lower Phi Delta values, that is, 0.29 +/- 0.02 (as an iodide salt) and 0.32 +/- 0.02 (as a chloride salt). In view of the very high values of Phi Delta, the photophysics of complexes 1 and 2 has been studied by means of pump and probe experiments using ns laser pulses at 532 nm as excitation source. Both complexes behave like reverse saturable absorbers at 440 nm because of triplet excited-state absorption. The lifetimes of the triplet excited states are 65 and 96 ns for the penta- and mononuclear species, respectively. Fluorescence quantum yields (Phi f) are approximately 0.1% for both 1 and 2. Such low Phi f values for the two complexes are consistent with the high efficiency of triplet excited-state formation and the measured high yields of (1)O 2. Time-dependent density-functional theory (TDDFT) calculations of the lowest singlet and triplet excited states of the mono- and pentapalladated species help to rationalize the photophysical behavior and the relevant activity of the complexes as photosensitizers for the (1)O 2 ( (1)Delta g) generation.
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http://dx.doi.org/10.1021/ic800678mDOI Listing
October 2008

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 5. Synthesis, physicochemical and theoretical studies of a novel pentanuclear palladium(II) complex and related mononuclear species.

Inorg Chem 2008 May;47(9):3903-19

Dipartimento di Chimica, Università degli Studi di Roma La Sapienza, Piazzale A. Moro 5, Rome, Italy.

New palladium(II) complexes of the free-base tetrakis[2,3-(5,6-di-2-pyridylpyrazino)porphyrazine], [Py 8TPyzPzH 2], have been prepared and their physicochemical properties examined. The investigated compounds are the pentanuclear species [(PdCl 2) 4Py 8TPyzPzPd], the monopalladated complex [Py 8TPyzPzPd], and its corresponding octaiodide salt [(2-Mepy) 8TPyzPzPd](I) 8. All three Pd (II) complexes have a common central pyrazinoporphyrazine core and differ only at the periphery of the macrocycle, where the simple dipyridinopyrazine fragments present in [Py 8TPyzPzPd] bear four PdCl 2 units coordinated at the pyridine N atoms in the pentanuclear complex, [(PdCl 2) 4Py 8TPyzPzPd], or carry pyridine-N(CH 3) (+) moieties in the iodide of the octacation [(2-Mepy) 8TPyzPzPd] (8+). The structural features of the pentanuclear complex [(PdCl 2) 4Py 8TPyzPzPd], partly supported by X-ray data and solution (1)H NMR spectra of the [(CN) 2Py 2PyzPdCl 2] precursor, were elucidated through one- and two-dimensional (1)H NMR spectra in solution and density functional theory (DFT) calculations. Structural information on the monopalladated complex [Py 8TPyzPzPd] was also obtained from DFT calculations. It was found that in the complex [(PdCl 2) 4Py 8TPyzPzPd] the peripheral PdCl 2 units adopt a py-py coordination mode and the generated N 2PdCl 2 moieties are directed nearly perpendicular to the plane of the pyrazinoporphyrazine ring, strictly recalling the arrangement found for the palladated precursor [(CN) 2Py 2PyzPdCl 2]. NMR and DFT results consistently indicate that of the four structural isomers predictable for [(PdCl 2) 4Py 8TPyzPzPd], one having all four N 2PdCl 2 moieties pointing on the same side of the macrocyclic framework (i.e., isomer 4:0, plus the 3:1 and the 2:2-cis and 2:2-trans isomers), the 4:0 isomer ( C 4 v symmetry) is the predominant form present. According to cyclic voltammetry and spectroelectrochemical results in pyridine, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF), the monopalladated complex [Py 8TPyzPzPd] undergoes four reversible or quasi-reversible one-electron ligand-centered reductions, similar to the behavior also observed for the pentanuclear complex [(PdCl 2) 4Py 8TPyzPzPd], which shows an additional reduction peak attributable to the presence of PdCl 2. Owing to the electron-withdrawing properties of the PdCl 2 units, the pentanuclear complex is easier to reduce than the mononuclear complex [Py 8TPyzPzPd], some related [Py 8TPyzPzM] complexes, and their porphyrin or porphyrazine analogues, so much so that the corresponding monoanion radical is generated at potentials close to 0.0 V vs SCE in DMSO or DMF. In turn, the monoanion of [(2-Mepy) 8TPyzPzPd](I) 8 is also extremely easy to generate electrochemically. Indeed, because of the eight positively charged N-CH 3 (+) groups in this complex the first reduction occurs at potentials close to +0.10 V in DMSO or DMF. The redox behavior of the mono- and pentapalladated complexes has been rationalized on the basis of a detailed DFT analysis of their ground-state electronic structure.
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http://dx.doi.org/10.1021/ic702430jDOI Listing
May 2008

Photophysical behavior of open-shell first-row transition-metal octabutoxynaphthalocyanines: CoNc(OBu)8 and CuNc(OBu)8 as case studies.

Inorg Chem 2008 May 12;47(10):4275-89. Epub 2008 Apr 12.

Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.

Ultrafast photodynamics and density functional theory/time-dependent density functional theory (DFT/TDDFT) results for complexes of Co and Cu with 5,9,14,18,23,27,32,36-octabutoxynaphthalocyanine [CoNc(OBu)8 and CuNc(OBu)8] are reported. As a basis for this work, details concerning the syntheses of these complexes and the corresponding Zn complex (used as a reference) are given. Transient absorption spectrometry with femtosecond time resolution combined with a detailed DFT/TDDFT analysis has been employed to construct a complete picture of the excited-state dynamics after Q-band excitation of the Co and Cu complexes and to gain an understanding of the relationship between the nature of the metal center and the excited-state lifetime. The Co complex was shown to return to its ground state via two competing channels: a (2)T1(pi, pi*) state that decayed with a lifetime of 1 ps and a low-lying (2)(d, d) state that repopulated the ground-state surface with a lifetime of 15 ps. CuNc(OBu)8 showed ground-state repopulation from the (2)T1(pi, pi*) state via a lower-lying ligand-to-metal charge-transfer (LMCT) state that was completed within a few nanoseconds. The photophysical behavior of the cobalt and copper complexes was compared to that previously reported for the nickel analog in an effort to highlight the effect of the central metal on the nature and rates of the deactivation pathways. The results described in this work provide basic knowledge that is relevant to the use of these compounds as photothermal sensitizers in cancer therapy.
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http://dx.doi.org/10.1021/ic7023204DOI Listing
May 2008

On the photophysics of metallophthalocyanine-based photothermal sensitizers: synergism between theory and experiment.

J Inorg Biochem 2008 Mar 28;102(3):406-13. Epub 2007 Nov 28.

Dipartimento di Chimica, Università della Basilicata, Via N. Sauro 85, 85100 Potenza, Italy.

A comprehensive understanding of the factors governing the efficiency of metallophthalocyanine-based photothermal sensitizers requires the knowledge of their excited-state dynamics. This can only be properly gained when the nature and energy of the excited states (often spectroscopically silent) lying between the photogenerated state and the ground state are known. Here the excited state deactivation mechanism of two very promising metallophthalocyanine-based photothermal sensitizers, NiPc(OBu)(8) and NiNc(OBu)(8), is reviewed. It is shown that time dependent density functional theory (TDDFT) methods are capable to provide reliable information on the nature and energies of the low-lying excited states along the relaxation pathways. TDDFT calculations and ultrafast experiments consistently show that benzoannulation of the Pc ring modifies the photodeactivation mechanism of the photogenerated S(1)(pi,pi*) state by inducing substantial changes in the relative energies of the excited states lying between the S(1)(pi,pi*) state and the ground state.
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http://dx.doi.org/10.1016/j.jinorgbio.2007.10.029DOI Listing
March 2008

Evidence for tetraphenylporphyrin monoacids.

Inorg Chem 2007 Jul 23;46(15):5979-88. Epub 2007 Jun 23.

Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina and C.I.R.C.M.S.B., Messina, Italy.

Upon dilution from a concentrated solution in dichloromethane, the diacid form of tetraphenylporphyrin {H(4)TPP(X)(2)} (X = Cl, PF(6) and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, TFPB) affords eventually the unprotonated free base species H(2)TPP. At a difference of chloride, in the case of PF(6)(-) and TFPB(-) anions the conversion occurs with the intermediacy of a species, which has been assigned to a monoacid derivative on the basis of UV/vis absorption, fluorescence emission (static and dynamic), and resonance light scattering. Ground-state gas-phase geometries have been calculated both for the diacid {H(4)TPP(PF(6))(2)} and monoacid {H(4)TPP(PF(6))(2)} and {H(3)TPP(Cl)} species at the DFT/BP86 level of theory. TDDFT calculations using different functionals (BP86, SAOP, and B3LYP) have been exploited to provide electronic vertical excitation energies and oscillator strengths, yielding a remarkably good description of the optical spectra for these compounds and supporting the identification of the monoacid species. Gas-phase thermodynamic calculations on the chloride species provide an estimate of the Gibbs free energy changes associated with the two protonation steps, supporting the observed different behavior of this anion with respect to PF(6)(-) and TFPB(-).
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http://dx.doi.org/10.1021/ic0703373DOI Listing
July 2007

Tetrakis(thiadiazole)porphyrazines. 5. Electrochemical and DFT/TDDFT studies of the free-base macrocycle and its MgII, ZnII, and CuII complexes.

Inorg Chem 2007 May 20;46(10):4145-57. Epub 2007 Apr 20.

Dipartimento di Chimica, Università degli Studi di Roma La Sapienza, P.le A. Moro 5, Roma I-00185, Italy.

The redox properties of the phthalocyanine-like tetrakis(thiadiazole)porphyrazines, [TTDPzM] (M = MgII(H2O), ZnII, CuII, 2HI), were investigated by cyclic voltammetry, and their ground- and excited-state electronic properties were studied in detail by density functional theory (DFT) and time-dependent DFT (TDDFT) methods. Bulk and specific (axial ligation) solvent effects on the molecular and electronic structure were also taken into account. The title compounds show stepwise reversible ligand-centered one-electron reductions in the range 0 to -2.0 V vs SCE, with E1/2 values being systematically less negative than corresponding reduction potentials for the same processes of the phthalocyanine (Pc) analogues. No electroxidations were observed at positive potentials. The observed redox behavior is rationalized on the basis of the ground-state electronic structures which reveal that replacement of the benzo rings of the Pc macrocycle by electron-withdrawing thiadiazole rings induces a large stabilization of both the HOMO and LUMOs in the investigated macrocycles. An excellent correlation is found between the first one-electron reduction potentials and the gas-phase LUMO energies along the series. The same sequence in the first reduction potentials is theoretically reproduced in pyridine, even if the ZnII and MgII complexes are assumed to be in the axially ligated form, [TTDPzM(py)]. TDDFT calculations of the lowest excited states of the ZnII, MgII, and CuII complexes in pyridine provide an accurate description of their UV-visible spectra. The calculated optical spectra for the free-base macrocycle in chlorobenzene and pyridine confirm previous data in that the thiadiazoleporphyrazine [TTDPzH2] is mostly present in pyridine in its deprotonated form [TTDPz]2-. DFT results, in keeping with electrochemical data, indicate, however, that in pyridine it is the neutral species [TTDPzH2] being reduced instead of its deprotonated form [TTDPz]2-.
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http://dx.doi.org/10.1021/ic070038dDOI Listing
May 2007

Effects of benzoannulation and alpha-octabutoxy substitution on the photophysical behavior of nickel phthalocyanines: a combined experimental and DFT/TDDFT study.

Inorg Chem 2007 Mar 15;46(6):2080-93. Epub 2007 Feb 15.

Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.

The photophysical properties of a group of Ni(II)-centered tetrapyrroles have been investigated by ultrafast transient absorption spectrometry and DFT/TDDFT methods in order to characterize the impacts of alpha-octabutoxy substitution and benzoannulation on the deactivation pathways of the S1(pi,pi*) state. The compounds examined were NiPc, NiNc, NiPc(OBu)8, and NiNc(OBu)8, where Pc = phthalocyanine and Nc = naphthalocyanine. It was found that the S1(pi,pi*) state of NiNc(OBu)8 deactivated within the time resolution of the instrument (200 fs) to a vibrationally hot T1(pi,pi*) state. The quasidegeneracy of the S1(pi,pi*) and 3(dz2,dx2-y2) states allowed for fast intersystem crossing (ISC) to occur. After vibrational relaxation (ca. 2.5 ps), the T1(pi,pi*) converted rapidly (ca. 19 ps lifetime) and reversibly into the 3LMCT(pi,dx2-y2) state. The equilibrium state, so generated, decayed to the ground state with a lifetime of ca. 500 ps. Peripheral substitution of the Pc ring significantly modified the photodeactivation mechanism of the S1(pi,pi*) by inducing substantial changes in the relative energies of the S1(pi,pi*), 3(dpi,dx2-y2), 3(dz2,dx2-y2), T1(pi,pi*), and 1,3LMCT(pi,dx2-y2) excited states. The location of the Gouterman LUMOs and the unoccupied metal level (dx2-y2) with respect to the HOMO is crucial for the actual position of these states. In NiPc, the S1(pi,pi*) state underwent ultrafast (200 fs) ISC into a hot (d,d) state. Vibrational cooling (ca. 20 ps lifetime) resulted in a cold (dz2,dx2-y2) state, which repopulated the ground state with a 300 ps lifetime. In NiPc(OBu)8, the S1(pi,pi*) state deactivated through the 3(dz2,dx2-y2), which in turn converted to the 3LMCT(pi,dx2-y2) state, which finally repopulated the ground state with a lifetime of 640 ps. Insufficient solubility of NiNc in noncoordinating solvents prevented transient absorption data from being obtained for this compound. However, the TDDFT calculations were used to make speculations about the photoproperties.
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http://dx.doi.org/10.1021/ic061524oDOI Listing
March 2007

Synthesis and liposome insertion of a new poly(carboranylalkylthio)porphyrazine to improve potentiality in multiple-approach cancer therapy.

J Am Chem Soc 2007 Mar 14;129(10):2728-9. Epub 2007 Feb 14.

Department of Chemistry, University of Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy.

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http://dx.doi.org/10.1021/ja0661459DOI Listing
March 2007

Photophysics of octabutoxy phthalocyaninato-Ni(II) in toluene: ultrafast experiments and DFT/TDDFT studies.

J Phys Chem A 2005 Mar;109(10):2078-89

Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.

Reported herein is a combination of experimental and DFT/TDDFT theoretical investigations of the ground and excited states of 1,4,8,11,15,18,22,25-Octabutoxyphthalocyaninato-nickel(II), NiPc(BuO)(8), and the dynamics of its deactivation after excitation into the S(1)(pi,pi) state in toluene solution. According to X-ray crystallographic analysis NiPc(BuO)(8) has a highly saddled structure in the solid state. However, DFT studies suggest that in solution the complex is likely to flap from one D(2)(d)-saddled conformation to the opposite one through a D(4)(h)-planar structure. The spectral and kinetic changes for the complex in toluene are understood in terms of the 730 nm excitation light generating a primarily excited S(1) (pi,pi) state that transforms initially into a vibrationally hot (3)(d(z)2,d(x)2(-)(y)2) state. Cooling to the zeroth state is complete after ca. 8 ps. The cold (d,d) state converted to its daughter state, the (3)LMCT (pi,d(x)2(-)(y)2), which itself decays to the ground state with a lifetime of 640 ps. The proposed deactivation mechanism applies to the D(2)(d)-saddled and the D(4)(h)-planar structure as well. The results presented here for NiPc(BuO)(8) suggest that in nickel phthalocyanines the (1,3)LMCT (pi,d(x)2(-)(y)2) states may provide effective routes for radiationless deactivation of the (1,3)(pi,pi) states.
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http://dx.doi.org/10.1021/jp0457444DOI Listing
March 2005
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