Publications by authors named "Timothy Clark"

498 Publications

An electrically conducting three-dimensional iron-catecholate porous framework.

Angew Chem Int Ed Engl 2021 Mar 29. Epub 2021 Mar 29.

Ludwig-Maximilians-Universitat Munchen, Chemistry, Butenandtstrasse 11, 81377, München, GERMANY.

Here, we report the synthesis of a unique cubic metal-organic framework (MOF), the Fe-HHTP-MOF, comprising hexahydroxytriphenylene (HHTP) supertetrahedral units and FeIII ions, arranged in a diamond topology. The MOF is synthesized under solvothermal conditions, yielding a highly crystalline, deep black powder, with crystallites of 300-500 nm size and tetrahedral morphology. Nitrogen sorption analysis indicates a highly porous material with a surface area exceeding 1400 m2 g-1. Furthermore, Fe-HHTP-MOF shows broadband absorption from 475 nm up to 1900 nm with excellent absorption capability of 98.5% of the incoming light over the visible spectral region. Electrical conductivity measurements of pressed pellets reveal a high intrinsic electrical conductivity of up to 10-3 S cm-1. Quantum mechanical calculations predict Fe-HHTP-MOF to be an efficient electron conductor, exhibiting continuous charge-carrier pathways throughout the structure. This report expands the paradigm of intrinsically electroactive MOFs, serving as a solid basis for the development of highly porous, ordered frameworks with enhanced electrical conductivity.
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http://dx.doi.org/10.1002/anie.202102670DOI Listing
March 2021

Developing and employing ideal teams for optimal global health outcomes.

J Glob Health 2021 Jan 30;11:02001. Epub 2021 Jan 30.

Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.

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http://dx.doi.org/10.7189/jogh.11.02001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7919232PMC
January 2021

Dibenzodiazepinone-type muscarinic receptor antagonists conjugated to basic peptides: Impact of the linker moiety and unnatural amino acids on MR selectivity.

Eur J Med Chem 2021 Mar 13;213:113159. Epub 2021 Jan 13.

Institute of Pharmacy, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany. Electronic address:

The family of human muscarinic acetylcholine receptors (MRs) is characterized by a high sequence homology among the five subtypes (MR-MR), being the reason for a lack of subtype selective MR ligands. In continuation of our work on dualsteric dibenzodiazepinone-type MR antagonists, a series of MR ligands containing a dibenzodiazepinone pharmacophore linked to small basic peptides was synthesized (64 compounds). The linker moiety was varied with respect to length, number of basic nitrogens (0-2) and flexibility. Besides proteinogenic basic amino acids (Lys, Arg), shorter homologues of Lys and Arg, containing three and two methylene groups, respectively, as well as D-configured amino acids were incorporated. The type of linker had a marked impact on MR affinity and also effected MR selectivity. In contrast, the structure of the basic peptide rather determined MR selectivity than MR affinity. For example, the most MR selective compound (UR-CG188, 89) with picomolar MR affinity (pK 9.60), exhibited a higher MR selectivity (ratio of K MR/MR/MR/MR/MR: 110:1:5200:55:2300) compared to the vast majority of reported MR preferring MR ligands. For selected ligands, MR antagonism was confirmed in a MR miniG protein recruitment assay.
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http://dx.doi.org/10.1016/j.ejmech.2021.113159DOI Listing
March 2021

Pre-Planarized Triphenylamine-Based Linear Mixed-Valence Charge-Transfer Systems.

Angew Chem Int Ed Engl 2021 Mar 3;60(12):6771-6777. Epub 2021 Feb 3.

Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058, Erlangen, Germany.

Three linear dimers with two redox-active planarized triphenylamines were synthesized and their structures verified by X-ray crystallography. Their radical cations, which exhibit electron self-exchange between the two redox centers, are of great interest. This process was thoroughly investigated by means of electron paramagnetic resonance spectroscopy, absorption spectroscopy, and (time-dependent) density functional theory calculations. A comparison of the key parameters of electron transfer with non-planarized nitrogen-centered building blocks emphasizes the impact of using redox centers with low internal reorganization energies. However, the distance-dependence attenuation factor of the super-exchange mechanisms remains similar.
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http://dx.doi.org/10.1002/anie.202014567DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7986061PMC
March 2021

Response to Letter to the Editor.

J Vasc Interv Radiol 2020 12;31(12):2160

Section of Interventional Radiology, Department of Radiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania.

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http://dx.doi.org/10.1016/j.jvir.2020.08.016DOI Listing
December 2020

Modulating the dynamics of Förster resonance energy transfer and singlet fission by variable molecular spacers.

Nanoscale 2020 Nov;12(45):23061-23068

Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-University Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany.

In contrast to previous work, the synergy between panchromatic absorption and molecular singlet fission (SF) is exploited to optimize solar energy conversion through evaluation of the distance dependence of intramolecular Förster Resonance Energy Transfer (i-FRET) in a series of subphthalocyanines (SubPcs) linked to pentacene dimers (Pnc2s). To provide control over i-FRET, the molecular spacer rather than the energy donating SubPc is tailored in the corresponding SubPc-Pnc2 conjugates in terms of length (i.e., the number of aryl units) and flexibility (i.e., presence or absence of a CH2 group). AM1-CIS calculations support the experiments, which underline the importance of the molecular spacer to impact not only the i-FRET dynamics, but also the dynamics of intramolecular singlet fission (i-SF). For example, an additional phenyl group slows down both i-FRET and i-SF by a factor of ∼3.8 and ∼1.6, respectively, by a quinone-like conjugation pattern that affords a pentacene acceptor orbital that is fairly delocalized over both pentacenes and the bridging phenyl.
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http://dx.doi.org/10.1039/d0nr06285eDOI Listing
November 2020

Reply to: Methods matter in repeating ocean acidification studies.

Nature 2020 Oct;586(7830):E25-E27

Department of Aquatic Resources, Swedish University of Agricultural Sciences, Drottningholm, Sweden.

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http://dx.doi.org/10.1038/s41586-020-2804-9DOI Listing
October 2020

Resonance-Enhanced Charge Delocalization in Carbazole-Oligoyne-Oxadiazole Conjugates.

J Am Chem Soc 2020 11 21;142(44):18769-18781. Epub 2020 Oct 21.

Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen 91058, Germany.

There are notably few literature reports of electron donor-acceptor oligoynes, even though they offer unique opportunities for studying charge transport through "all-carbon" molecular bridges. In this context, the current study focuses on a series of carbazole-(C≡C)-2,5-diphenyl-1,3,4-oxadiazoles ( = 1-4) as conjugated π-systems in general and explores their photophysical properties in particular. Contrary to the behavior of typical electron donor-acceptor systems, for these oligoynes, the rates of charge recombination after photoexcitation increase with increasing electron donor-acceptor distance. To elucidate this unusual performance, we conducted detailed photophysical and time-dependent density functional theory investigations. Significant delocalization of the molecular orbitals along the bridge indicates that the bridging states come into resonance with either the electron donor or acceptor, thereby accelerating the charge transfer. Moreover, the calculated bond lengths reveal a reduction in bond-length alternation upon photoexcitation, indicating significant cumulenic character of the bridge in the excited state. In short, strong vibronic coupling between the electron-donating -arylcarbazoles and the electron-accepting 1,3,4-oxadiazoles accelerates the charge recombination as the oligoyne becomes longer.
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http://dx.doi.org/10.1021/jacs.0c04003DOI Listing
November 2020

Energy Efficient Ultrahigh Flux Separation of Oily Pollutants from Water with Superhydrophilic Nanoscale Metal-Organic Framework Architectures.

Angew Chem Int Ed Engl 2021 Mar 18;60(10):5519-5526. Epub 2021 Jan 18.

Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität (LMU), Butenandtstr. 5-13, 81377, Munich, Germany.

The rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar-like Co-CAT-1 metal-organic framework (MOF) crystallites on gold-coated woven stainless steel meshes with large, 50 μm apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity-driven, highly efficient oil-water separation featuring water fluxes of up to nearly one million L m  h . Water physisorption experiments reveal the hydrophilic nature of Co-CAT-1 with a total water vapor uptake at room temperature of 470 cm  g . Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF-based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on-surface extreme wetting properties, yielding energy-efficient water-selective large-aperture membranes.
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http://dx.doi.org/10.1002/anie.202012428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7986099PMC
March 2021

Retrospective Analysis of 77 Hemodialysis Patients Shows No Cases of Steal Syndrome from Graft Taper Reduction.

J Vasc Interv Radiol 2020 11 18;31(11):1831-1835. Epub 2020 Sep 18.

Department of Radiology, Division of Interventional Radiology, Perelman School of Medicine at the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA, 19104. Electronic address:

Purpose: To review the immediate flow response and incidence of steal syndrome after taper reduction of tapered dialysis grafts.

Material And Methods: This was a retrospective review of a quality assurance database of all hemodialysis access interventions performed between 2005 and 2017. It identified 77 patients who underwent a taper reduction procedure, involving angioplasty of the arterial limb of the graft and the arterial anastomosis for graft thrombosis/poor flow. A subset of patients underwent 5-, 6-, or 7-mm balloon taper reduction angioplasty coupled with intravascular direct flow measurement (n = 15 with 16 dialysis grafts). A two-tailed Wilcoxon matched-pairs signed-rank test was used to compare pre- and post-taper reduction flows. Mean duration of follow-up was 3.5 years (range, 0-12.5 years).

Results: Mean access survival after taper reduction was 20.2 months (range, 0.10-94.4 months). Pre- and post-taper reduction access flows (mean Qb ± standard deviation) were 574 ± 315 ml/min and 929 ± 352 ml/min, respectively (P < .0001). The mean ratio of post- to pre-taper reduction flows was 1.6 (range, 1.1-10.2). No patients developed steal syndrome within 6 months after taper reduction.

Conclusions: Dialysis graft arterial anastomotic taper reduction did not result in the development of steal syndrome within 6 months. In the subset of patients who underwent flow measurements, taper reduction was associated with nearly a 2-fold improvement in access flow, which is a key predictor of access function.
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http://dx.doi.org/10.1016/j.jvir.2020.04.006DOI Listing
November 2020

Phosphine-Directed sp C-H, C-O, and C-N Borylation.

J Org Chem 2020 11 2;85(22):14795-14801. Epub 2020 Oct 2.

Department of Chemistry and Biochemistry, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States.

Benzylic C-H borylation reactions are limited, requiring new approaches to exploit their reactivity for efficient selective functionalization. The recent development of phosphine-directed C-H borylation of arenes has now been extended to benzylic substrates, providing high yield of the mono- and geminal bis-borylation products. Attempts to borylate the C-H bond α to a benzylic ether or amine resulted in C-O and C-N borylation, followed by C-H borylation to provide geminal bis-borylated products.
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http://dx.doi.org/10.1021/acs.joc.0c01706DOI Listing
November 2020

The Cascade Reactions of Indigo with Propargyl Substrates for Heterocyclic and Photophysical Diversity.

Chemistry 2021 Feb 12;27(11):3708-3721. Epub 2021 Feb 12.

School of Chemistry & Molecular Bioscience, Molecular Horizons, Illawarra Health & Medical Research Institute, University of Wollongong, Northfields Avenue, 2522, Wollongong, NSW, Australia.

The synthesis of structurally diverse heterocycles for chemical space exploration was achieved via the cascade reactions of indigo with propargylic electrophiles. New pyrazinodiindolodione, naphthyridinedione, azepinodiindolone, oxazinoindolone and pyrrolodione products were prepared in one pot reactions by varying the leaving group (-Cl, -Br, -OMs, -OTs) or propargyl terminal functionality (-H, -Me, -Ph, -Ar). Mechanistic and density functional theory studies revealed that the unsaturated propargyl moiety can behave as an electrophile when aromatic terminal substitutions are made, and therefore competes with leaving group substitution for new outcomes. Selected products from the cascade reactions were investigated for their absorption and fluorescence properties, including transient absorption spectroscopy. This revealed polarity dependent excited state relaxation pathways, fluorescence, and triplet formation, thus highlighting these reactions as a means to access diverse functional materials rapidly.
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http://dx.doi.org/10.1002/chem.202003662DOI Listing
February 2021

Neoureter Creation to Bypass Distal Ureter Obstruction into Neobladder Using Radiofrequency Guide-Wire Technique.

J Vasc Interv Radiol 2020 09 14;31(9):1503-1505. Epub 2020 Aug 14.

Section of Interventional Radiology, Department of Radiology, University of Pennsylvania Perelman School of Medicine, Penn Presbyterian Medical Center, 51 N. 39th St., Philadelphia, PA 19104.

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http://dx.doi.org/10.1016/j.jvir.2020.04.012DOI Listing
September 2020

Models of necessity.

Beilstein J Org Chem 2020 13;16:1649-1661. Epub 2020 Jul 13.

Beilstein-Institut, Trakehner Str. 7-9, 60487 Frankfurt am Main, Germany.

The way chemists represent chemical structures as two-dimensional sketches made up of atoms and bonds, simplifying the complex three-dimensional molecules comprising nuclei and electrons of the quantum mechanical description, is the everyday language of chemistry. This language uses models, particularly of bonding, that are not contained in the quantum mechanical description of chemical systems, but has been used to derive machine-readable formats for storing and manipulating chemical structures in digital computers. This language is fuzzy and varies from chemist to chemist but has been astonishingly successful and perhaps contributes with its fuzziness to the success of chemistry. It is this creative imagination of chemical structures that has been fundamental to the cognition of chemistry and has allowed thought experiments to take place. Within the everyday language, the model nature of these concepts is not always clear to practicing chemists, so that controversial discussions about the merits of alternative models often arise. However, the extensive use of artificial intelligence (AI) and machine learning (ML) in chemistry, with the aim of being able to make reliable predictions, will require that these models be extended to cover all relevant properties and characteristics of chemical systems. This, in turn, imposes conditions such as completeness, compactness, computational efficiency and non-redundancy on the extensions to the almost universal Lewis and VSEPR bonding models. Thus, AI and ML are likely to be important in rationalizing, extending and standardizing chemical bonding models. This will not affect the everyday language of chemistry but may help to understand the unique basis of chemical language.
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http://dx.doi.org/10.3762/bjoc.16.137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7372249PMC
July 2020

Safety and Efficacy of Arterial Closure Devices Following Antegrade Femoral Access: A Case-Control Study.

Vasc Endovascular Surg 2020 Oct 28;54(7):612-617. Epub 2020 Jul 28.

Section of Interventional Radiology, Department of Radiology, Perelman School of Medicine of the University of Pennsylvania, Philadelphia, PA, USA.

Purpose: Vascular closure device (VCD) use following antegrade femoral access may present unique challenges relative to retrograde access. We retrospectively compared safety and efficacy of these devices between antegrade and retrograde patient cohorts undergoing percutaneous intervention.

Materials And Methods: Over a 5-year period, a consecutive series of 107 limbs in 84 patients underwent VCD arteriotomy closure following percutaneous revascularization using an antegrade approach (VCD-A). Device deployment success rates, time to ambulation, and complication rates were compared to a contemporaneous control group of 401 limbs in 305 patients who underwent closure following retrograde access (VCD-R) during revascularization or embolization procedures.

Results: Closure was attempted in VCD-A using 53 StarClose, 35 Perclose, and 19 Angio-Seal devices. Hemostasis (without supplemental manual compression) was achieved in 86/107 (80.4%) limbs. Closure was attempted in VCD-R using 215 StarClose, 119 Perclose, and 67 Angio-Seal devices with hemostasis in 357/401 (89.0%) limbs. Device deployment failure occurred in 7/107 (6.5%) of VCD-A and 20/401 (5.0%) of VCD-R ( .52), independent of specific device type. Femoral pseudoaneurysm developed in 1/107 and 1/401 of VCD-A and VCD-R ( = .31), and minor hematoma developed in 3/107 and 8/401 of the VCD-A and VCD-R ( = .61). Mean time to ambulation was 204.1 minutes in VCD-A and 204.8 minutes in VCD-R ( = .97).

Conclusion: Antegrade femoral closure was associated with high rates of technical success and low complications, similar to retrograde closure. Time to ambulation was the same in both groups despite higher heparin doses in the antegrade patients.
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http://dx.doi.org/10.1177/1538574420941298DOI Listing
October 2020

β-Silyloxy Allylboronate Esters through an Aldehyde Borylation/Homologation Sequence.

Tetrahedron Lett 2020 Jul 29;61(28). Epub 2020 May 29.

Department of Chemistry and Biochemistry, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, United States.

The areas of carbonyl borylation and the homologation of carbon-boron bonds have provided a number of fruitful methods in organic synthesis. Combining these approaches, the homologation of α-oxyboronate esters, provides pathways to access complex organoboronate esters stereoselectively. To this end, the homologation of α-silyloxyboronate esters with lithiated allyl chlorides to form β-silyloxy allylboronate esters is reported. Direct oxidation of the homologation products provides β-silyloxy allyl alcohols in good yield. The homologation provides a range of allylic alcohols, albeit with low diastereoselectivity.
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http://dx.doi.org/10.1016/j.tetlet.2020.152082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7351078PMC
July 2020

Synergy of Electrostatic and π-π Interactions in the Realization of Nanoscale Artificial Photosynthetic Model Systems.

Angew Chem Int Ed Engl 2020 10 2;59(42):18786-18794. Epub 2020 Sep 2.

Department of Organic Chemistry, Universidad Autónoma de Madrid (UAM), c/ Francisco Tomás y Valiente 7, Cantoblanco, 28049, Madrid, Spain.

In the scientific race to build up photoactive electron donor-acceptor systems with increasing efficiencies, little is known about the interplay of their building blocks when integrated into supramolecular nanoscale arrays, particularly in aqueous environments. Here, we describe an aqueous donor-acceptor ensemble whose emergence as a nanoscale material renders it remarkably stable and efficient. We have focused on a tetracationic zinc phthalocyanine (ZnPc) featuring pyrenes, which shows an unprecedented mode of aggregation, driven by subtle cooperation between electrostatic and π-π interactions. Our studies demonstrate monocrystalline growth in solution and a symmetry-breaking intermolecular charge transfer between adjacent ZnPcs upon photoexcitation. Immobilizing a negatively charged fullerene (C ) as electron acceptor onto the monocrystalline ZnPc assemblies was found to enhance the overall stability, and to suppress the energy-wasting charge recombination found in the absence of C . Overall, the resulting artificial photosynthetic model system exhibits a high degree of preorganization, which facilitates efficient charge separation and subsequent charge transport.
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http://dx.doi.org/10.1002/anie.202006014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7590087PMC
October 2020

Arylphosphonate-Directed Ortho C-H Borylation: Rapid Entry into Highly-Substituted Phosphoarenes.

J Am Chem Soc 2020 07 2;142(28):11988-11992. Epub 2020 Jul 2.

Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.

Phosphonate-directed ortho C-H borylation of aromatic phosphonates is reported. Using simple starting materials and commercially accessible catalysts, this method provides steady access to -phosphonate arylboronic esters bearing pendant functionality and flexible substitution patterns. These products serve as flexible precursors for a variety of highly substituted phosphoarenes, and in situ downstream functionalization of the products is described.
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http://dx.doi.org/10.1021/jacs.0c04159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7405988PMC
July 2020

A combined activation mechanism for the glucagon receptor.

Proc Natl Acad Sci U S A 2020 07 22;117(27):15414-15422. Epub 2020 Jun 22.

Department of Chemistry, University College London, London WC1E 6BT, United Kingdom;

We report on a combined activation mechanism for a class B G-protein-coupled receptor (GPCR), the glucagon receptor. By computing the conformational free-energy landscape associated with the activation of the receptor-agonist complex and comparing it with that obtained with the ternary complex (receptor-agonist-G protein) we show that the agonist stabilizes the receptor in a preactivated complex, which is then fully activated upon binding of the G protein. The proposed mechanism contrasts with the generally assumed GPCR activation mechanism, which proceeds through an opening of the intracellular region allosterically elicited by the binding of the agonist. The mechanism found here is consistent with electron cryo-microscopy structural data and might be general for class B GPCRs. It also helps us to understand the mode of action of the numerous allosteric antagonists of this important drug target.
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http://dx.doi.org/10.1073/pnas.1921851117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355025PMC
July 2020

Perylene-Monoimides: Singlet Fission Down-Conversion Competes with Up-Conversion by Geminate Triplet-Triplet Recombination.

J Phys Chem A 2020 Jul 7;124(28):5727-5736. Epub 2020 Jul 7.

Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Egerlandstrasse 3, 91058 Erlangen, Germany.

Triplet-excited-state energies of perylene-monoimides (PMIs) lie in the range 1.12 eV ± 2 meV when compared to singlet-excited-state energies of about 2.39 eV ± 2 meV; therefore, the corresponding naphthalene-linked was investigated as a novel singlet-fission (SF) material. Ultrafast transient absorption measurements demonstrated the (SS)-to-(TT) transformation and the involvement of a mediating step in the overall (TT) formation. The intermediate is a charge-transfer state that links the initial (SS) with the final (TT), and imposes charge-transfer character on both, which are thus denoted (SS) and (TT). At room temperature, the decorrelation and stability of (TT) is affected by the geminate triplet-triplet recombination (G-TTR) of the two triplets. Independent confirmation for G-TTR to afford up-converted (SS) in fsTA and nsTA measurements with , came from probing (T)s in triplet-triplet annihilation up-conversion (TTA-UC). The G-TTR channel, active in the at room temperature, is suppressed by working at either low temperatures (∼140 K) or in polar solvents (benzonitrile): Both scenarios assist in stabilizing (TT). As a consequence, the triplet quantum yields are 4.2% and 14.9% at room temperature and 140 K, respectively, in 2-methyltetrahydrofuran.
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http://dx.doi.org/10.1021/acs.jpca.0c04091DOI Listing
July 2020

Comparison of Clinical Performance of VectorFlow and Palindrome Symmetric-Tip Dialysis Catheters: A Multicenter, Randomized Trial.

J Vasc Interv Radiol 2020 07 10;31(7):1148-1155. Epub 2020 Jun 10.

Department of Radiology, University of Pennsylvania Perelman School of Medicine, 3400 Spruce St., 1 Silverstein, Philadelphia, PA 19104.

Purpose: To compare clinical performance of 2 widely used symmetric-tip hemodialysis catheters.

Materials And Methods: Patients with end-stage renal disease initiating or resuming hemodialysis were randomized to receive an Arrow-Clark VectorFlow (n = 50) or Palindrome catheter (n = 50). Primary outcome was 90-d primary unassisted catheter patency. Secondary outcomes were Kt/V ([dialyzer urea clearance × total treatment time]/total volume of urea distribution), urea reduction ratio (URR), and effective blood flow (Q).

Results: Primary unassisted patency rates with the VectorFlow catheter at 30, 60, and 90 d were 95.5% ± 3.3, 87.2% ± 7.3, and 80.6% ± 9.8, respectively, compared with 89.1% ± 6.2, 79.4% ± 10.0, and 71.5% ± 12.6 with the Palindrome catheter (P = .20). Patients with VectorFlow catheters had a mean Kt/V of 1.5 at 30-, 60-, and 90-day time points, significantly higher than the mean Kt/V of 1.3 among those with Palindrome catheters (P = .0003). URRs were not significantly different between catheters. Catheter Q rates exceeded National Kidney Foundation-recommended thresholds of 300 mL/min at all time points for both catheters and were similar for both catheters (median, 373 mL/min). Catheter failure, ie, poor flow rate requiring guide-wire exchange or removal, within the 90-day primary outcome occurred in 3 VectorFlow subjects and 5 Palindrome subjects (P = .72). Infection rates were similar, with 0.98 infections per 1,000 catheter days for VectorFlow catheters compared with 2.62 per 1,000 catheter days for Palindrome catheters (P = .44).

Conclusions: The 90-day primary patency rates of Palindrome and VectorFlow catheters were not significantly different, and both achieved sustained high Q through 90 day follow-up. However, dialysis adequacy based on Kt/V was consistently better with the VectorFlow catheter versus the Palindrome.
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http://dx.doi.org/10.1016/j.jvir.2020.02.001DOI Listing
July 2020

How To Make Nitroaromatic Compounds Glow: Next-Generation Large X-Shaped, Centrosymmetric Diketopyrrolopyrroles.

Angew Chem Int Ed Engl 2020 Sep 10;59(37):16104-16113. Epub 2020 Jul 10.

Institute of Organic Chemistry, PAS. 44/52 Kasprzaka, 01-224, Warsaw, Poland.

Red-emissive π-expanded diketopyrrolopyrroles (DPPs) with fluorescence reaching λ=750 nm can be easily synthesized by a three-step strategy involving the preparation of diketopyrrolopyrrole followed by N-arylation and subsequent intramolecular palladium-catalyzed direct arylation. Comprehensive spectroscopic assays combined with first-principles calculations corroborated that both N-arylated and fused DPPs reach a locally excited (S ) state after excitation, followed by internal conversion to states with solvent and structural relaxation, before eventually undergoing intersystem crossing. Only the structurally relaxed state is fluorescent, with lifetimes in the range of several nanoseconds and tens of picoseconds in nonpolar and polar solvents, respectively. The lifetimes correlate with the fluorescence quantum yields, which range from 6 % to 88 % in nonpolar solvents and from 0.4 % and 3.2 % in polar solvents. A very inefficient (T ) population is responsible for fluorescence quantum yields as high as 88 % for the fully fused DPP in polar solvents.
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http://dx.doi.org/10.1002/anie.202005244DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7689858PMC
September 2020

Impact of PTFE-covered stent position and extension on TIPS patency.

Abdom Radiol (NY) 2020 11;45(11):3915-3922

Perelman School of Medicine - University of Pennsylvania, 3400 Civic Center Blvd, Philadelphia, PA, 19104, USA.

Purpose: The objectives of this study were to determine the effects of expanded polytetrafluoroethylene (PTFE)-covered stent location and TIPS extension on primary patency.

Methods: This retrospective cohort study examined patients with PTFE-covered TIPS creation between 07/2002 and 06/2016. Clinical information and patency outcomes at 24 months were extracted. At TIPS creation, extension was performed at the discretion of the operator. Kaplan-Meier curves of primary patency were generated with conditional variables of HVO-HCJ distance, extension status, and covered versus uncovered extensions. Additional logistic regression analyses of distances were performed.

Results: Of 393 patients, 115 patients (29%) underwent stent extension, 79 (20% of total cohort) of which were at the HVO end alone. Primary patency for all TIPS was 75%, 68%, and 54% at 3, 6, and 12 months. The data endpoint were transplant or death in 92 (23%) and 116 (30%). Kaplan-Meier curves showed no statistically significant difference between the variables and primary patency at 12 and 24 months: distance up to versus greater than 10 mm (p = 0.32, 0.81); extension versus no extension (p = 0.83, 0.85); uncovered versus covered extensions (p = 0.58, 0.70). Logistic regression analyses showed a trend toward statistical significance.

Conclusion: In the setting of PTFE-covered TIPS creation, extended TIPSs and unextended well-positioned TIPSs have no difference in primary patency rates. Stent position and extension length may have an effect on primary patency, but were likely obscured by "user recognition" effects.
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http://dx.doi.org/10.1007/s00261-020-02566-8DOI Listing
November 2020

Diagnosis and Treatment of Nonmaturing Fistulae for Hemodialysis Access via Transradial Approach: A Case-Control Study.

J Vasc Interv Radiol 2020 Jun 4;31(6):993-999.e1. Epub 2020 May 4.

Department of Radiology, Section of Interventional Radiology, University of Pennsylvania Perelman School of Medicine, 51 N 39th St., Philadelphia, PA, 19104. Electronic address:

Purpose: To compare outcomes of transradial access for endovascular treatment of nonmaturing hemodialysis fistulae compared to brachial arteriography followed by unidirectional or bidirectional fistula access for intervention.

Materials And Methods: In this institutional review board-approved, retrospective, case-control study, 56 consecutive patients with nonmaturing arteriovenous fistulae underwent percutaneous intervention between 2015 and 2018. The transradial group (n = 28) underwent radial artery access for diagnostic fistulography and intervention. The control group (n = 28) underwent retrograde brachial artery access for fistulography followed by unidirectional/bidirectional fistula access for intervention. Both groups had similar demographics, fistula characteristics, and stenosis locations.

Results: Fewer punctures were required in the transradial group compared to controls (1.2 vs 2.4, P < .0001), and procedure time was shorter (64.9 vs 91.3 minutes, P = .0016). Anatomic, technical, and clinical success rates trended higher in the transradial group compared to controls (93% vs 86%, 96% vs 89%, and 82% vs 64%, respectively). Nonmaturation resulting in fistula abandonment was lower in the transradial group (3.7% vs 25%, P = .025). Primary unassisted patency at 3, 6, and 12 months was 77.1% ± 8.2%, 73.1% ± 8.7%, and 53.3% ± 10.6% in the transradial group, respectively, and 63.0% ± 9.3%, 55.6% ± 9.6%, and 48.1% ± 9.6% in the control group, respectively (P = .76). Primary assisted patency at 12 months was 92.3% ± 5.3% in the transradial group compared to 61.8% ± 9.6% at 12 months in the control group (P = .021). No major complications occurred. Minor complications were lower in the transradial group than in the control group (14% vs 39%, P = .068).

Conclusions: Treatment of nonmaturing fistulae via a transradial approach was safe, improved midterm patency, and was associated with lower rates of fistula abandonment.
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http://dx.doi.org/10.1016/j.jvir.2020.01.023DOI Listing
June 2020

Randomized Trial of Radial Hemostasis Using Focused vs Balloon Compression Devices.

J Invasive Cardiol 2020 May 24;32(5):169-174. Epub 2020 Apr 24.

Gagnon Cardiovascular Institute, Morristown Medical Center, 100 Madison Ave, Morristown, NJ 07960 USA.

Background: Radial artery hemostasis devices differ in compression mechanisms, which may influence time to hemostasis and hand perfusion.

Methods: Subjects (n = 52) undergoing transradial diagnostic coronary catheterization or percutaneous coronary intervention (PCI) were randomized 1:1 to either focused compression (VasoStat; Forge Medical) or balloon compression device (TR Band; Terumo Medical) for radial artery hemostasis. Time to complete hemostasis enabling device removal was measured in each subject. Hand perfusion was quantitated using the perfusion index (PI) with oximetry (1) before; (2) during device use; (3) during device use with ulnar artery compression; and (4) following device removal.

Results: Focused compression resulted in a significantly shorter time to complete hemostasis vs balloon compression (208 min [IQR, 115-320 min] vs 242 min [IQR, 120-439 min], respectively; P=.04). This difference was greatest among the subset undergoing PCI, where the VasoStat resulted in a 43-minute reduction until complete hemostasis (P=.04). Baseline PI was similar between the focused and balloon compression groups (4.9 vs 3.9, respectively; P=.09). Focused compression resulted in a similar reduction in median PI from baseline to during device use compared with balloon compression (-27% vs -18%, respectively; P=.26). Both devices decreased PI over 50% from baseline during simultaneous ulnar artery compression (P<.01), and increased PI over 50% from baseline following device removal (P=.02). No radial artery occlusion occurred, and rates of device manipulation and access-site bleeds were low in both groups.

Conclusion: Complete hemostasis was achieved earlier with the VasoStat focused compression device compared with the TR Band balloon compression device. Both devices transiently reduced hand perfusion, particularly during ulnar compression, which increased from baseline following device removal. Larger trials comparing these radial hemostasis devices and outcomes are warranted.
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May 2020

Reframing conservation physiology to be more inclusive, integrative, relevant and forward-looking: reflections and a horizon scan.

Conserv Physiol 2020 4;8(1):coaa016. Epub 2020 Apr 4.

Department of Animal Science, University of California Davis, One Shields Ave. Davis, CA, 95616, USA.

Applying physiological tools, knowledge and concepts to understand conservation problems (i.e. conservation physiology) has become commonplace and confers an ability to understand mechanistic processes, develop predictive models and identify cause-and-effect relationships. Conservation physiology is making contributions to conservation solutions; the number of 'success stories' is growing, but there remain unexplored opportunities for which conservation physiology shows immense promise and has the potential to contribute to major advances in protecting and restoring biodiversity. Here, we consider how conservation physiology has evolved with a focus on reframing the discipline to be more inclusive and integrative. Using a 'horizon scan', we further explore ways in which conservation physiology can be more relevant to pressing conservation issues of today (e.g. addressing the Sustainable Development Goals; delivering science to support the UN Decade on Ecosystem Restoration), as well as more forward-looking to inform emerging issues and policies for tomorrow. Our horizon scan provides evidence that, as the discipline of conservation physiology continues to mature, it provides a wealth of opportunities to promote integration, inclusivity and forward-thinking goals that contribute to achieving conservation gains. To advance environmental management and ecosystem restoration, we need to ensure that the underlying science (such as that generated by conservation physiology) is relevant with accompanying messaging that is straightforward and accessible to end users.
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http://dx.doi.org/10.1093/conphys/coaa016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7125050PMC
April 2020

Best practices for non-lethal blood sampling of fish via the caudal vasculature.

J Fish Biol 2020 Jul 29;97(1):4-15. Epub 2020 May 29.

Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental and Interdisciplinary Sciences, Carleton University, Ottawa, Ontario, Canada.

Blood sampling through the caudal vasculature is a widely used technique in fish biology for investigating organismal health and physiology. In live fishes, it can provide a quick, easy and relatively non-invasive method for obtaining a blood sample (cf. cannulation and cardiac puncture). Here, a general set of recommendations are provided for optimizing the blood sampling protocol that reflects best practices in animal welfare and sample integrity. This includes selecting appropriate use of anaesthetics for blood sampling as well as restraint techniques for situations where sedation is not used. In addition, ideal sampling environments where the fish can freely ventilate and strategies for minimizing handling time are discussed. This study summarizes the techniques used for extracting blood from the caudal vasculature in live fishes, highlighting the phlebotomy itself, the timing of sampling events and acceptable blood sample volumes. This study further discuss considerations for selecting appropriate physiological metrics when sampling in the caudal region and the potential benefits that this technique provides with respect to long-term biological assessments. Although general guidelines for blood sampling are provided here, it should be recognized that contextual considerations (e.g., taxonomic diversity, legal matters, environmental constraints) may influence the approach to blood sampling. Overall, it can be concluded that when done properly, blood sampling live fishes through the caudal vasculature is quick, efficient and minimally invasive, thus promoting conditions where live release of focal animals is possible.
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http://dx.doi.org/10.1111/jfb.14339DOI Listing
July 2020

Influence of the heavy-atom effect on singlet fission: a study of platinum-bridged pentacene dimers.

Chem Sci 2019 Dec 21;10(48):11130-11140. Epub 2019 Oct 21.

Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM) , Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , Egerlandstrasse 3 , 91058 Erlangen , Germany . Email:

The process of singlet fission (SF) produces two triplet excited states (T + T) from one singlet excited exciton (S) and a molecule in its ground state (S). It, thus, possesses the potential to boost the solar cell efficiency above the thermodynamic Shockley-Queisser limit of 33%. A key intermediate in the SF mechanism is the singlet correlated triplet pair state (TT). This state is of great relevance, as its formation is spin-allowed and, therefore, very fast and efficient. Three fundamentally different pathways to formation of (TT) have been documented so far. The factors that influence which mechanism is associated with which chromophore, however, remain largely unknown. In order to harvest both triplet excitons independently, a decorrelation of the correlated triplet pair state to two individual triplets is required. This second step of the SF process implies a change in the total spin quantum number. In the case of a dimer, this is usually only possible if the coupling between the two pentacenes is sufficiently weak. In this study, we present two platinum-bridged pentacene dimers in which the pentacenes are coupled strongly, so that spin-decorrelation yielding (T + T) was initially expected to be outcompeted by triplet-triplet annihilation (TTA) to the ground state. Both platinum-bridged pentacene dimers undergo quantitative formation of the (TT) state on a picosecond timescale that is unaffected by the internal heavy-atom effect of the platinum. Instead of TTA of (TT) to the ground state, the internal heavy-atom effect allows for (TT)-(TT) and (TT)-(TT) mixing and, thus, triggers subsequent TTA to the (TS) state and minor formation of (T + T). A combination of transient absorption and transient IR spectroscopy is applied to investigate the mechanism of the (TT) formation in both dimers. Using a combination of experiment and quantum chemical calculations, we are able to observe a transition from the CT-mediated to the direct SF mechanism and identify relevant factors that influence the mechanism that dominates SF in pentacene. Moreover, a combination of time-resolved optical and electron paramagnetic resonance spectroscopic data allows us to develop a kinetic model that describes the effect of enhanced spin-orbit couplings on the correlated triplet pair state.
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http://dx.doi.org/10.1039/c9sc04410hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7069226PMC
December 2019

Understanding and Controlling Short- and Long-Range Electron/Charge-Transfer Processes in Electron Donor-Acceptor Conjugates.

J Am Chem Soc 2020 04 16;142(17):7898-7911. Epub 2020 Apr 16.

Interdisciplinary Center for Molecular Materials, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nuremberg, Egerlandstrasse 3, 91058 Erlangen, Germany.

We probed a series of multicomponent electron donor-donor-acceptor conjugates both experimentally and computationally. The conjugates are based on the light harvester and primary electron-donor zinc-porphyrin (ZnP, donor) to whose β positions a secondary electron-donor ferrocene (Fc, donor) and the primary electron-acceptor C-fullerene (C, acceptor) are attached. Linking all of them via -phenylene-acetylene/acetylene bridges of different lengths to gain full control over shuttling electrons and holes between C, ZnP, and Fc is novel. Different charge-separation, charge-transfer, and charge-recombination routes have been demonstrated, both by transient absorption spectroscopy measurements on the femto, pico-, nano-, and microsecond time scales and by multiwavelength and target analyses. The molecular wire-like nature of the -phenylene-acetylene bridges as a function of C-ZnP and ZnP-Fc distances is decisive in the context of generating distant and long-lived C-ZnP-Fc charge-separated states. For the first time, we confirm the presence of two adjacent charge-transfer states, a C-ZnP-Fc intermediate in addition to C-ZnP-Fc, en route to the distant C-ZnP-Fc charge-separated state. Our studies demonstrate how the interplay of changes in the reorganization energy and the damping factor of the molecular bridges, in addition to variation in the solvent polarity, affect the outcome of the charge-transfer and corresponding rate constants. The different regions of the Marcus parabola are highly relevant in this matter: The charge recombination of, for example, the adjacent C-ZnP-Fc charge-separated state is located in the inverted region, while that of the distant C-ZnP-Fc charge-separated state lies in the normal region. Here, the larger reorganization energy of Fc relative to ZnP makes the difference.
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http://dx.doi.org/10.1021/jacs.0c01452DOI Listing
April 2020