Publications by authors named "Masoumeh Hasani"

20 Publications

  • Page 1 of 1

Hairpin-Spherical Nucleic Acids for Diagnosing COVID-19: a Simple Method to Generalize the Conventional PCR for Molecular Assays.

Anal Chem 2021 07 22;93(26):9250-9257. Epub 2021 Jun 22.

Department of Molecular Diagnosis, Farzan Molecular and Pathobiology Laboratory, Hamedan 6515638377, Iran.

The COVID-19 pandemic revealed during the first global wave of this infectious disease that mass diagnostic testing was necessary to more rapidly detect infection in patients and control the pandemic. Therefore, extra research efforts to develop reliable and more accessible techniques for disease diagnosis are of supreme importance. Here, a target-responsive assembly of gold nanoparticle-core hairpin-spherical nucleic acids (AuNP-core H-SNAs) was implemented to modify the conventional polymerase chain reaction (PCR) assay for the "naked-eye" colorimetric detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Two hairpin DNA ligands are designed based on the two highly conserved regions within N and E genes of SARS-CoV-2 RNA by positioning two short palindromic arms (stem) on either side of a recognition sequence (loop). In the presence of a sequence-specific probe (activator), hairpin DNAs anchored to the surface of AuNPs unfold and expose the palindromic ends to the DNA-directed assembly of AuNPs. The sequence of the activator probes was chosen to be identical to the TaqMan probe in a real-time reverse transcription PCR (RT-PCR) assay for specifically targeting the N and E genes of SARS-CoV-2 RNA. They may either be degraded by the 5'-exonuclease activity of DNA polymerase during PCR cycles or stay intact depending on the presence or absence of the target template in the sample, respectively. Post-addition of H-SNA solutions to the final PCR products of some preconfirmed clinical samples for COVID-19 generated naked-eye-observable red and blue colors for positive and negative cases, respectively, with similar sensitivity to that of the real-time RT-PCR method.
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http://dx.doi.org/10.1021/acs.analchem.1c01515DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8247783PMC
July 2021

Conventional PCR assisted single-component assembly of spherical nucleic acids for simple colorimetric detection of SARS-CoV-2.

Sens Actuators B Chem 2021 Feb 28;328:128971. Epub 2020 Sep 28.

Department of Molecular Diagnosis, Farzan Molecular and Pathobiology Laboratory, Hamedan, Iran.

Continuous identification of suspected infectious cases is crucial to control the recent pandemic caused by the novel human coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2). Real-time polymerase chain reaction (real-time PCR) technology cannot be implemented easily and in large scale in some communities due to lack of resources and infrastructures. Here, we report a simple colorimetric strategy derived from linker-based single-component assembly of gold nanoparticle-core spherical nucleic acids (AuNP-core SNAs) for visual detection of PCR products of SARS-CoV-2 ribonucleic acid (RNA) template. A palindromic linker is designed based on SARS-CoV-2 specific E gene to program the identical colloidal SNAs into large assemblies along with a distinct red-to-purple color change. The linker acts as a probe of SARS-CoV-2 RNA in conventional PCR reaction. In the presence of the correct template the palindromic linker, which is complementary to a short region within the target amplicon, is cleaved by 5'-exonuclease activity of deoxyribonucleic acid (DNA) polymerase. Cleavage of the palindromic linker during the amplification process inhibits the single-component assembly formation of SNAs. So, positive and negative viral samples produce simply red and purple colors in the post PCR colorimetric test, respectively. Evaluation of the samples obtained from cases with laboratory-confirmed SARS-CoV-2 infection revealed that our assay can rival with real-time PCR method in sensitivity.
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http://dx.doi.org/10.1016/j.snb.2020.128971DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7521892PMC
February 2021

A palindromic-based strategy for colorimetric detection of HIV-1 nucleic acid: Single-component assembly of gold nanoparticle-core spherical nucleic acids.

Anal Chim Acta 2020 Mar 19;1102:119-129. Epub 2019 Dec 19.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 65174, Iran. Electronic address:

Gold nanoparticle-core spherical nucleic acids (AuNP core-SNAs), by virtue of the programmable nature of oligonucleotides, have yielded access to the innovative strategies for targeted biodiagnostics. Here, DNA-directed self-assembly of AuNP core-SNAs has been used to design a colorimetric method to sense HIV-1 viral nucleic acid. This strategy utilizes an oligonucleotide with sequence of 5'-untranslated region (5' UTR) of the HIV-1 RNA genome anchored on the surface of AuNPs and a complementary linker strand with a palindromic sequence tail. In the absence of HIV-1 target nucleic acid the complementary linker induces self-assembly of SNAs based on sequence symmetry in the free palindromic tail which can bridge two DNA double helices. While in the presence of the target DNA, due to linker-target duplex formation, the colloidal stability and the red color of the SNAs solution are preserved. Picomole amounts of target DNA can easily be detected with the naked eyes. A 95-mer synthetic DNA strand with the same sequence of HIV-1 viral RNA was utilized for positive control of HIV-1 RNA. The selectivity of the selected linker was satisfactory up to 90% match.
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http://dx.doi.org/10.1016/j.aca.2019.12.050DOI Listing
March 2020

Nanodiamonds and Their Applications in Cells.

Small 2018 06 24;14(24):e1704263. Epub 2018 Mar 24.

University Medical Center Groningen, Groningen University, Antonius Deusinglaan 1, 9713, AW, Groningen, The Netherlands.

Diamonds owe their fame to a unique set of outstanding properties. They combine a high refractive index, hardness, great stability and inertness, and low electrical but high thermal conductivity. Diamond defects have recently attracted a lot of attention. Given this unique list of properties, it is not surprising that diamond nanoparticles are utilized for numerous applications. Due to their hardness, they are routinely used as abrasives. Their small and uniform size qualifies them as attractive carriers for drug delivery. The stable fluorescence of diamond defects allows their use as stable single photon sources or biolabels. The magnetic properties of the defects make them stable spin qubits in quantum information. This property also allows their use as a sensor for temperature, magnetic fields, electric fields, or strain. This Review focuses on applications in cells. Different diamond materials and the special requirements for the respective applications are discussed. Methods to chemically modify the surface of diamonds and the different hurdles one has to overcome when working with cells, such as entering the cells and biocompatibility, are described. Finally, the recent developments and applications in labeling, sensing, drug delivery, theranostics, antibiotics, and tissue engineering are critically discussed.
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http://dx.doi.org/10.1002/smll.201704263DOI Listing
June 2018

Nanodiamonds for In Vivo Applications.

Small 2018 05 9;14(19):e1703838. Epub 2018 Feb 9.

University Medical Center Groningen, Groningen University, Antonius Deusinglaan 1, 9713, AW, Groningen, Netherlands.

Due to their unique optical properties, diamonds are the most valued gemstones. However, beyond the sparkle, diamonds have a number of unique properties. Their extreme hardness gives them outstanding performance as abrasives and cutting tools. Similar to many materials, their nanometer-sized form has yet other unique properties. Nanodiamonds are very inert but still can be functionalized on the surface. Additionally, they can be made in very small sizes and a narrow size distribution. Nanodiamonds can also host very stable fluorescent defects. Since they are protected in the crystal lattice, they never bleach. These defects can also be utilized for nanoscale sensing since they change their optical properties, for example, based on temperature or magnetic fields in their surroundings. In this Review, in vivo applications are focused upon. To this end, how different diamond materials are made and how this affects their properties are discussed first. Next, in vivo biocompatibility studies are reviewed. Finally, the reader is introduced to in vivo applications of diamonds. These include drug delivery, aiding radiology, labeling, and use in cosmetics. The field is critically reviewed and a perspective on future developments is provided.
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http://dx.doi.org/10.1002/smll.201703838DOI Listing
May 2018

H-point curve isolation method for determination of catechol in complex unknown mixtures.

Spectrochim Acta A Mol Biomol Spectrosc 2012 Oct 15;96:563-8. Epub 2012 Jul 15.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran.

In this work, the combination of H-point curve isolation method (HPCIM) and H-point standard additions method (HPSAM) was used for determination of catechol in the presence of phenolic interferents. Spectrophotometric multivariate calibration data constructed by successive standard additions of an analyte in an unknown matrix was used by the method. A cumulative spectrum for interferents in sample was extracted by HPCIM and then HPSAM is used for determination of the catechol concentration by obtained cumulative interferents spectrum. The method was tested with simulated data set. The spectrum obtained from applying HPCIM to the simulated data well agrees with the cumulative spectra of the interferents. The method was applied to the determination of catechol in the presence of highly overlapping interferents in synthetic ternary mixtures using spectrophotometric data. Moreover, the proposed method was successfully used for determination of catechol in real complicated matrices of tea and urine samples. Percent recoveries were between 95.4 and 113.6.
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http://dx.doi.org/10.1016/j.saa.2012.07.024DOI Listing
October 2012

Hard- and soft-modeling approaches for resolution of complex formation of Co2+ and Ni2+ with glycine.

Appl Spectrosc 2012 Apr;66(4):432-9

Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah, Iran.

Principal component analysis (PCA) was used to obtain information about the number of components in the complex formation equilibria of Co(2+) and Ni(2+) with glycine (Gly). In order to obtain a clearer insight into these complex formation systems, multivariate curve resolution-alternating least squares (MCR-ALS) was used. Using MCR-ALS as a soft-modeling method, well-defined concentration and spectral profiles were obtained under unimodality, non-negativity, and closure constraints. Based on the obtained results, an equilibrium model was proposed and subsequently, a hard-modeling method was used to resolve the complex formation equilibria completely. Due to the presence of multiple equilibria, the resolution of such systems is very difficult. The Co-Gly system was best described by a model consisting of M(GlyH), M(Gly), M(Gly)(2), M(Gly)(2)H, and M(Gly)(3) (M = Co(2+)) with the overall stability constants determined to be 7.10 ± 0.011, 5.14 ± 0.006, 9.28 ± 0.009, 13.75 ± 0.016, and 11.10 ± 0.010, respectively. On the other hand, the system of Ni-Gly was best fitted by a model containing M(GlyH), M(Gly), M(Gly)(2), M(Gly)(3), and M(Gly)(2)(OH) (M = Ni(2+)) with overall stability constants of 10.95 ± 0.04, 6.41 ± 0.03, 11.31 ± 0.03, 15.39 ± 0.06, and 14.32 ± 0.02, respectively.
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http://dx.doi.org/10.1366/11-06512DOI Listing
April 2012

Principle component analysis (PCA) and second-order global hard-modelling for the complete resolution of transition metal ions complex formation with 1,10-phenantroline.

Anal Chim Acta 2009 Aug 17;648(1):60-70. Epub 2009 Jun 17.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran.

Second-order global hard-modelling was applied to resolve the complex formation between Co(2+), Ni(2+), and Cd(2+) cations and 1,10-phenantroline. The highly correlated spectral and concentration profiles of the species in these systems and low concentration of some species in the individual collected data matrices prevent the well-resolution of the profiles. Therefore, a collection of six equilibrium data matrices including series of absorption spectra taken with pH changes at different reactant ratios were analyzed. Firstly, a precise principle component analysis (PCA) of different augmented arrangements of the individual data matrices was used to distinguish the number of species involved in the equilibria. Based on the results of PCA, the equilibria included in the data were specified and second-order global hard-modelling of the appropriate arrangement of six collected equilibrium data matrices resulted in well-resolved profiles and equilibrium constants. The protonation constant of the ligand (1,10-phenantroline) and spectral profiles of its protonated and unprotonated forms are the additional information obtained by global analysis. For comparison, multivariate curve resolution-alternating least squares (MCR-ALS) was applied to the same data. The results showed that second-order global hard-modelling is more convenient compared with MCR-ALS especially for systems with completely known model. It can completely resolve the system and the concentration profiles which are closer to correct ones. Moreover, parameters showing the goodness of fit are better with second-order global hard-modelling.
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http://dx.doi.org/10.1016/j.aca.2009.06.020DOI Listing
August 2009

Application of multivariate curve resolution-alternating least squares (MCR-ALS) for secondary structure resolving of proteins.

Biochimie 2009 Jul 17;91(7):850-6. Epub 2009 Apr 17.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran.

Fourier transform infrared (FTIR) spectroscopy is the most common spectroscopic technique used for study of protein structure. Initially, band deconvolution techniques were applied to determine the secondary structure of proteins. Recently, several multivariate regression methods have been used to predict the secondary structure of proteins as an alternative to the previous methods. Multivariate curve resolution-alternating least squares (MCR-ALS) was applied on the FTIR spectra of proteins to resolve the fraction and spectral profiles of different structural motifs. Initial estimates of spectral profiles of different protein motifs were built using orthogonal projection approach (OPA). Predicted fractions of alpha-helix and beta-sheet obtained by MCR-ALS technique were compared with those from partial least squares (PLS) modeling which revealed superiority of the former. If we consider the possibility of pure spectra prediction in addition to the prediction of secondary structure from the data set, MCR-ALS can be proposed as a very valuable alternative for qualitative and quantitative study of protein structures.
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http://dx.doi.org/10.1016/j.biochi.2009.04.005DOI Listing
July 2009

Application of soft- and hard-modelling approaches to resolution of kinetics of electron donor-acceptor complex formation of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with imipramine in different solutions.

Anal Chim Acta 2009 Mar 3;636(2):175-82. Epub 2009 Feb 3.

Faculty of Chemistry, Bu-Ali Sina University, Mahdieh, Hamedan, 65174, Iran.

Kinetics of electron donor-acceptor (EDA) complex formation of imipramine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was investigated spectrophotometrically in acetonitrile, 1,2-dichloroethane, and chloroform solutions using soft- and hard-modelling approaches. From the results of exploratory analysis of kinetic data and the spectral changes by soft-modelling approaches, evolving factor analysis (EFA) and orthogonal projection approach (OPA), a consecutive two-steps reaction with two intermediates was proposed for the process in acetonitrile and 1,2-dichloroethane media and one with a single intermediate in chloroform solution. Secondly, by applying, multivariate nonlinear least squares hard-modelling approach on the collected experimental kinetic data matrix, the nonlinear parameters (rate constants) as well as the linear parameters (spectral profiles) were obtained by fitting the collected experimental kinetic data matrix to the proposed model. Small values of standard deviation in the resulting parameters and sum of squares of the residuals (ssq) obtained showed the proper selection of the model. Furthermore, the values of lack of fit and percent of explained variance confirmed the correct identified models. Identification of the model with the aid of soft-modelling approaches followed by application of the hard-modelling approaches decreases significantly the rotational ambiguity associated with the obtained concentration and spectral profiles. Variations in the kinetic constants were in complete agreement with the model proposed and the solvent polarities.
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http://dx.doi.org/10.1016/j.aca.2009.01.049DOI Listing
March 2009

Evaluation of feed-forward back propagation and radial basis function neural networks in simultaneous kinetic spectrophotometric determination of nitroaniline isomers.

Talanta 2008 Mar 4;75(1):116-26. Epub 2007 Dec 4.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran.

Mixtures of 2-, 3-, and 4-nitoroanilines, are simultaneously analyzed with spectrophotometry, based on their different kinetic properties. These nitroanilines react differentially with 1,2-naphtoquinone-4-sulphonate (NQS) at pH 7 in micellar medium to produce colored product. The differential kinetic spectra were monitored and recorded at 500 nm, and the data obtained from the experiments were processed by chemometric approaches, such as back-propagation neural networks (BPNNs), radial basis function neural networks (RBFNNs), and partial least squares (PLS). Experimental conditions were optimized and training the network was performed using principal components (PCs) of the original data. A set of synthetic mixtures of nitroanilines was evaluated and the results obtained by the application of these chemometric approaches were discussed and compared. The analytical performance of the models was characterized by relative standard errors. It was found that the artificial neural networks model affords relatively better results than PLS. The proposed method was applied to the determination of considered nitroanilines in water samples.
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http://dx.doi.org/10.1016/j.talanta.2007.10.038DOI Listing
March 2008

Application of principal component-artificial neural network models for simultaneous determination of phenolic compounds by a kinetic spectrophotometric method.

J Hazard Mater 2008 Aug 4;157(1):161-9. Epub 2008 Jan 4.

Faculty of chemistry, Bu-Ali Sina University, Hamedan 65174, Iran.

A multicomponent analysis method based on principal component analysis-artificial neural network models (PC-ANN) is proposed for the determination of phenolic compounds. The method relies on the oxidative coupling of phenols (phenol, 2 chlorophenol, 3-chlorophenol and 4-chlorophenol) to N,N-diethyl-p-phenylenediamine in the presence of hexacyanoferrate(III). The reaction monitored at analytical wavelength 680 nm of the dye formed. Phenols can be determined individually over the concentration range 0.1-7.0 microg ml(-1). Differences in the kinetic behavior of the four species were exploited by using PC-ANN, to resolve mixtures of phenol. After reducing the number of kinetic data using principal component analysis, an artificial neural network consisting of three layers of nodes was trained by applying a back-propagation learning rule. The optimized ANN allows the simultaneous quantitation of four analytes in mixtures with relative standard errors of prediction in the region of 5% for four species. The results show that PC-ANN is an efficient method for prediction of the four analytes.
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http://dx.doi.org/10.1016/j.jhazmat.2007.12.096DOI Listing
August 2008

Spectrophotometric resolution of ternary mixtures of tryptophan, tyrosine, and histidine with the aid of principal component-artificial neural network models.

Anal Biochem 2007 Nov 21;370(1):68-76. Epub 2007 Jun 21.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran.

A simple and sensitive spectrophotometric method to resolve ternary mixtures of tryptophan (Trp), tyrosine (Tyr), and histidine (His) in synthetic and water samples is described. It relies on the different kinetic rates of the analytes in their oxidative reaction with potassium ferricyanide (K(3)Fe(CN)(6)) in alkaline medium. The absorbance data were monitored on the analytical wavelength (420 nm) of K(3)Fe(CN)(6) spectrum. Synthetic mixtures of the three amino acids were analyzed, and the data obtained were processed by principal component-artificial neural network (PC-ANN) models. After reducing the number of spectral data using principal component analysis, an artificial neural network consisting of three layers of nodes was trained by applying a back-propagation learning rule. Tangent and sigmoidal transfer function were used in the hidden and output layers, respectively. The analytical performance of this method was characterized by relative standard error. The method allowed the determination of Trp, Tyr, and His at concentrations between 10 and 55, 10 and 60, and 10 and 40 microg ml(-1), respectively. The results show that the PC-ANN is an efficient method for prediction of the three analytes.
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http://dx.doi.org/10.1016/j.ab.2007.06.025DOI Listing
November 2007

A kinetic spectrophotometric method for simultaneous determination of glycine and lysine by artificial neural networks.

Anal Biochem 2007 Jun 15;365(1):74-81. Epub 2007 Feb 15.

Faculty of Chemistry, Bu-Ali Sina University, Hamadan 65174, Iran.

A spectrophotometric method for simultaneous analysis of glycine and lysine is proposed by application of neural networks on the spectral kinetic data. The method is based on the reaction of glycine and lysine with 1,2-naphthoquinone-4-sulfonate (NQS) in slightly basic medium. On the basis of the difference in the rate between the two reactions, these two amino acids can be determined simultaneously in binary mixtures. Feed-forward neural networks have been trained to quantify considered amino acids in mixtures under optimum conditions. In this way, a one-layer network was trained. Sigmoidal and linear transfer functions were used in the hidden and output layers, respectively. Linear calibration graphs were obtained in the concentration range of 1 to 25microgml(-1) for glycine and 1 to 19microgml(-1) for lysine. The analytical performance of this method was characterized by the relative standard error. The proposed method was applied to the determination of considered amino acids in synthetic samples.
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http://dx.doi.org/10.1016/j.ab.2007.02.010DOI Listing
June 2007

Kinetic spectrophotometric determination of Fe(II) in the presence of Fe(III) by H-point standard addition method in mixed micellar medium.

Spectrochim Acta A Mol Biomol Spectrosc 2007 Nov 14;68(3):414-9. Epub 2006 Dec 14.

Department of Chemistry, Bu-Ali Sina University, Hamadan, Iran.

The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition.
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http://dx.doi.org/10.1016/j.saa.2006.12.011DOI Listing
November 2007

Spectrophotometric study of interaction of iodine with 4'-aminobenzo-15-crown-5 in chloroform, dichloromethane and 1,2-dichloroethane solutions.

Spectrochim Acta A Mol Biomol Spectrosc 2007 Nov 8;68(3):409-13. Epub 2006 Dec 8.

Department of Chemistry, College of Science, Bu-Ali Sina University, Hamadan, Iran.

The formation of charge transfer complex between 4'-aminobenzo-15-crown-5 (AB15C5) and iodine is investigated spectrophotometrically in chloroform, dichloromethane (DCM) and 1,2-dichloroethane (DCE) solutions at 25 degrees C. The continuous variation method clearly revealed the formation of 1:1 charge transfer complex in solution. The observed time dependence of the charge transfer band and subsequent formation of I 3- in solution were related to the slow transformation of the initially formed 1:1 AB15C5.I2 outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants for the transformation process were evaluated from the absorbance-time data and found to vary in the order of 1,2-DCE>DCM>CHCl3. The values of the formation constant, KDA, for each complex are evaluated from Benesi-Hilebrand equation. Stability of the resulting complex in three solvents was also found to vary in the order of 1,2-DCE>DCM>CHCl3.
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http://dx.doi.org/10.1016/j.saa.2006.12.003DOI Listing
November 2007

A spectrophotometric and thermodynamic study of the charge-transfer complexes of iodine with 2-aminomethyl-15-crown-5 in chloroform and 1,2-dichloroethane solutions.

Spectrochim Acta A Mol Biomol Spectrosc 2007 May 1;67(1):139-44. Epub 2006 Jul 1.

Department of Chemistry, College of Science, Bu-Ali Sina University, Hamadan 65174, Iran.

Interaction of 2-aminomethyl-15-crown-5 (AM15C5) with iodine has been investigated spectrophotometrically in chloroform and 1,2-dichloroethane (1,2-DCE) solutions. The observed time dependence of the charge-transfer band and subsequent formation of I(3)(-) in solution were related to the slow transformation of the initially formed 1:1 AM15C5.I(2) outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants were evaluated from the absorbance- and conductivity-time data. The stoichiometry and formation constants of the resulting EDA complexes have also been determined. Thermodynamic parameters, Delta H degrees and Delta S degrees , of the complexes have been determined from the temperature dependence of stability constants by Van't Hoff equation. The results indicate that iodine complexes of AM15C5 in both solvents are enthalpy stabilized but entropy destabilized. The influence of solvent properties on the kinetics and stability of the resulting charge-transfer complexes are discussed.
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http://dx.doi.org/10.1016/j.saa.2006.06.033DOI Listing
May 2007

Spectrophotometric study of the charge-transfer complexes of iodine with antipyrine in organic solvents.

Spectrochim Acta A Mol Biomol Spectrosc 2006 Dec 5;65(5):1093-7. Epub 2006 Jul 5.

Department of Chemistry, College of Science, Bu-Ali Sina University, Hamadan 65174, Iran.

The charge-transfer complex formation of iodine with antipyrine has been studied spectrophotometrically in chloroform, dichloromethane (DCM) and 1,2-dichloroethane (DCE) solutions at 25 degrees C. The results indicate the formation of 1:1 charge-transfer complexes. The observed time dependence of the charge-transfer band and subsequent formation of I(3)(-) in solution were related to the slow transformation of the initially formed 1:1 antipyrine:I(2) outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The values of the equilibrium constant, K, are calculated for each complex and the influence of the solvent properties on the formation of EDA complexes and the rates of subsequent reaction is evaluated.
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http://dx.doi.org/10.1016/j.saa.2006.02.009DOI Listing
December 2006

Spectroscopic and conductometric studies of molecular complex formation between 2,4,6-trinitrophenol and diaza-18-crown-6, tetraaza-14-crown-4 and cryptand C222 in 1,2-dichloroethane solution.

Spectrochim Acta A Mol Biomol Spectrosc 2006 Feb 27;63(2):377-82. Epub 2005 Dec 27.

Department of Chemistry, Bu-Ali Sina University, Hamadan, Iran.

The formation of molecular complexes between 2,4,6-trinitrophenol (TNP) and aza-substituted macrocycles diaza-18-crown-6 (DA18C6), tetraaza-14-crown-4 (TA14C4) and cryptand C222 in 1,2-dichloroethane solution was investigated spectrophotometrically and conductometrically. The mole ratio and continuous variations studies based on both physicochemical techniques employed clearly revealed the formation of both 1:1 and 2:1 (TNP:macrocycle) adducts in solution. Formation of the resulting complexes was also confirmed by 1H NMR and IR spectroscopic studies. Formation constants of the resulting complexes were evaluated from computer fitting of the corresponding mole ratio data. Stability of the resulting complexes was found to vary in the order C222 approximately TA14C4 > DA18C6.
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http://dx.doi.org/10.1016/j.saa.2005.05.023DOI Listing
February 2006

Spectrophotometric study of interaction of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with diaza-18-crown-6 and diaza-15-crown-5 in acetonitrile and chloroform solutions.

Spectrochim Acta A Mol Biomol Spectrosc 2005 Mar;61(5):815-21

Department of Chemistry, Bu-Ali Sina University, Hamadan, Iran.

Interactions of diaza-18-crown-6 and diaza-15-crown-5, as electron donors, with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), as an electron acceptor, have been investigated spectrophotometrically in acetonitrile and chloroform solutions. The results indicated immediate formation of an electron donor-electron acceptor complex DA: [reaction in text] which is followed by two relatively slow consecutive reactions: [reaction in text]. The pseudo-first-order rate constants for the formation of the ionic intermediate and the final product have been evaluated at various temperatures by computer fitting of the absorbance time data to appropriate equations. The formation constants of the resulting DA complexes have also been determined. The influences of both the azacrown's structure and the solvent properties on the formation of DA complexes and the rates of subsequent reactions are discussed.
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http://dx.doi.org/10.1016/j.saa.2004.06.004DOI Listing
March 2005
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