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Lemler PM, Craft CL, Pollok CH, Regan TP, Vaccaro PH. Isolated and solvated chiroptical behavior in conformationally flexible butanamines. Chirality 2023; 35:586-618. [PMID: 37550220 DOI: 10.1002/chir.23570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/15/2023] [Accepted: 04/17/2023] [Indexed: 08/09/2023]
Abstract
The nonresonant optical activity of two highly flexible aliphatic amines, (2R)-3-methyl-2-butanamine (R-MBA) and (2R)-(3,3)-dimethyl-2-butanamine (R-DMBA), has been probed under isolated and solvated conditions to examine the roles of conformational isomerism and to explore the influence of extrinsic perturbations. The optical rotatory dispersion (ORD) measured in six solvents presented uniformly negative rotatory powers over the 320-590 nm region, with the long-wavelength magnitude of chiroptical response growing nearly monotonically as the dielectric constant of the surroundings diminished. The intrinsic specific optical rotation,α λ T (in deg dm-1 [g/mL]-1 ), extracted for ambient vapor-phase samples of R-MBA [-11.031(98) and -2.29 (11)] and R-DMBA [-9.434 (72) and -1.350 (48)] at 355 and 633 nm were best reproduced by counterintuitive solvents of high polarity (yet low polarizability) like acetonitrile and methanol. Attempts to interpret observed spectral signatures quantitatively relied on the linear-response frameworks of density-functional theory (B3LYP, cam-B3LYP, and dispersion-corrected analogs) and coupled-cluster theory (CCSD), with variants of the polarizable continuum model (PCM) deployed to account for the effects of implicit solvation. Building on the identification of several low-lying equilibrium geometries (nine for R-MBA and three for R-DMBA), ensemble-averaged ORD profiles were calculated at T = 300 K by means of the independent-conformer ansatz, which enabled response properties predicted for the optimized structure of each isomer to be combined through Boltzmann-weighted population fractions derived from corresponding relative internal-energy or free-energy values, the latter of which stemmed from composite CBS-APNO and G4 analyses. Although reasonable accord between theory and experiment was realized for the isolated (vapor-phase) species, the solution-phase results were less satisfactory and tended to degrade progressively as the solvent polarity increased. These trends were attributed to solvent-mediated changes in structural parameters and energy metrics for the transition states that separate and putatively isolate the equilibrium conformations supported by the ground electronic potential-energy surface, with the resulting displacement of barrier locations and/or decrease of barrier heights compromising the underlying premise of the independent-conformer ansatz.
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Affiliation(s)
- Paul M Lemler
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
- Intel Corporation, Hillsboro, Oregon, USA
| | - Clayton L Craft
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
- United States Air Force Research Laboratory, Rome, New York, USA
| | - Corina H Pollok
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
- Organische Chemie II, Ruhr-Universität Bochum, Bochum, Germany
| | - Thomas P Regan
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
| | - Patrick H Vaccaro
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
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2
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Sabia R, Ciogli A, Pierini M, Franzini R, Iazzetti A, Villani C. Chromatographic separation of the interconverting enantiomers of imidazo- and triazole-fused benzodiazepines. J Chromatogr A 2021; 1647:462148. [PMID: 33957345 DOI: 10.1016/j.chroma.2021.462148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/25/2021] [Accepted: 04/03/2021] [Indexed: 10/21/2022]
Abstract
The toolbox of medicinal chemists includes the 1,4-benzodiazepine scaffold as a "privileged scaffold" in drug discovery. Several biologically active small molecules containing a 1,4-benzodiazepine scaffold have been approved by the FDA for the treatment of various diseases, with most of them being used for their psychotropic effects. The therapeutic potential of 1,4-benzodiazepines has stimulated the interest of synthetic chemists in developing new synthetic strategies to a range of substituted analogues for biological evaluation. A structural variation of the classical benzodiazepine skeleton is observed e.g. in alprazolam, midazolam, and related benzodiazepines, which contain a 1,2,4-triazole or an imidazole ring fused to the benzodiazepine core. Irrespective of the presence of the fused heterocyclic ring, the seven-membered diazepine ring is far from planar, and its shape resembles a twist chair. Then, the unsymmetrical substitution pattern around the seven membered cycle renders these molecules chiral, as they lack any reflection-type symmetry element. However, chirality of this molecules is labile at room temperature, becausea simple ring flipping process converts one enantiomer into the other, and 1,4-benzodiazepines exist as a mixture of rapidly interconverting conformational enantiomers in solution at or near room temperature. Physical separation of the interconverting enantiomers of diazepam and of other related 1,4-benzodiazepin-2-ones can be accomplished by low temperature HPLC on chiral stationary phases (CSPs). If the HPLC column is cooled down to temperatures where the interconversion rate is sufficiently low, compared to the chromatographic separation rate, distinct separated peaks can be observed, provided the CSP is sufficiently enantioselctive. The apparent rate constants for the on-column enantiomerization and the corresponding free energy activation barriers were obtained by simulation of exchange-deformed HPLC profiles using a computer program based on the stochastic model. Here we report on the dynamic HPLC investigations carried out on a set of fused imidazo and triazolo-benzodiazepines (alprazolam, midazolam, triazolam and estazolam) The experimental dynamic chromatograms and the corresponding interconversion barriers reported in this paper show that the third fused heterocyclic ring increase the energy barrier by 2 kcal/mol.
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Affiliation(s)
- Rocchina Sabia
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy.
| | - Alessia Ciogli
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Marco Pierini
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Roberta Franzini
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Antonia Iazzetti
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Claudio Villani
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy.
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Ballard A, Narduolo S, Ahmed HO, Keymer NI, Asaad N, Cosgrove DA, Buurma NJ, Leach AG. Racemisation in Chemistry and Biology. Chemistry 2020; 26:3661-3687. [PMID: 31709642 DOI: 10.1002/chem.201903917] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Indexed: 11/09/2022]
Abstract
The two enantiomers of a compound often have profoundly different biological properties and thus their liability to racemisation in aqueous solutions is an important piece of information. The authors reviewed the available data concerning the process of racemisation in vivo, in the presence of biological molecules (e.g., racemase enzymes, serum albumin, cofactors and derivatives) and under purely chemical but aqueous conditions (acid, base and other aqueous systems). Mechanistic studies are described critically in light of reported kinetic data. The types of experimental measurement that can be used to effectively determine rate constants of racemisation in various conditions are discussed and the data they provide is summarised. The proposed origins of enzymatic racemisation are presented and suggest ways to promote the process that are different from processes taking place in bulk water. Experimental and computational studies that provide understanding and quantitative predictions of racemisation risk are also presented.
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Affiliation(s)
- Andrew Ballard
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Stefania Narduolo
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Hiwa O Ahmed
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.,Pharmaceutical Chemistry Department, Hawler Medical University, Erbil, Kurdistan Region, Iraq
| | - Nathaniel I Keymer
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Nabil Asaad
- AstraZeneca, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | | | - Niklaas J Buurma
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Andrew G Leach
- Division of Pharmacy and Optometry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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4
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Zimányi L, Krishnan SB, Williford E, Gupta S, Sepulveda J, Schwartz H, Mallory FB, Mallory CW, Dmitrenko O, Saltiel J. Translational Diffusion and Unstable Conformer Trapping in Glassy Isopentane at 77 K. J Phys Chem A 2019; 123:9102-9112. [PMID: 31557030 DOI: 10.1021/acs.jpca.9b07964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Diffusional quenching in isopentane (IP) glass at 77 K is demonstrated by the reduction of triphenylene phosphorescence lifetimes in the presence of 1,3-pentadiene and/or molecular oxygen. Fluorescence spectra and lifetimes of cis- and trans-1,2-di(1-methyl-2-naphthyl)ethene in IP glass at 77 K reveal that the cis → trans photoisomerization leads to the trapping of unstable conformers of the trans isomer. The claim that IP at 77 K is not sufficiently viscous to trap unstable photoproduct conformers is invalidated.
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Affiliation(s)
- László Zimányi
- Institute of Biophysics , Biological Research Centre, Hungarian Academy of Sciences , P.O. Box 521, Szeged , Hungary , H-6701
| | - Sumesh B Krishnan
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
| | - Emily Williford
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
| | - Shipra Gupta
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
| | - Jonathan Sepulveda
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
| | - Hadleigh Schwartz
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
| | - Frank B Mallory
- Department of Chemistry , Bryn Mawr College , Bryn Mawr , Pennsylvania 19010 , United States
| | - Clelia W Mallory
- Department of Chemistry , Bryn Mawr College , Bryn Mawr , Pennsylvania 19010 , United States.,Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Olga Dmitrenko
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Jack Saltiel
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
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5
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Al-Otaibi JS, El Gogary TM, El-Demerdash SH. Umbrella inversion and structure of phosphorus-containing compounds: A quantum chemical study. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2018. [DOI: 10.1142/s0219633618500426] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ab initio and density functional theory calculations were used to determine structure and inversion barrier at phosphorous (III) for open and cyclic phosphorus-containing compounds. Structures of the investigated systems were compared with the available experimental data. Effects of ring size on the P-inversion barriers in these molecules have been discussed. The largest/smallest inversion barrier was reported for phosphocyclopropene/trivinylphosphine (85.1/21.0 kcal/mol). Inversion rate and half-life time were computed.
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Affiliation(s)
- Jamelah S. Al-Otaibi
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Tarek M. El Gogary
- Department of Chemistry, Faculty of Science, Jazan University, Jazan, Saudi Arabia
- School of Allied Health Science, Faculty of Health and Life Sciences, De Montfort University, Leicester UK
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A new fundamental type of conformational isomerism. Nat Chem 2018; 10:615-624. [PMID: 29784991 DOI: 10.1038/s41557-018-0043-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 03/08/2018] [Indexed: 11/08/2022]
Abstract
Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol-1, which we term 'akamptisomerization'. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization.
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7
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Testa B, Vistoli G, Pedretti A. Mechanisms and pharmaceutical consequences of processes of stereoisomerisation — A didactic excursion. Eur J Pharm Sci 2016; 88:101-23. [DOI: 10.1016/j.ejps.2016.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 04/02/2016] [Accepted: 04/05/2016] [Indexed: 11/29/2022]
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8
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Dynamic Behavior of Clobazam on High-Performance Liquid Chromatography Chiral Stationary Phases. Chirality 2015; 28:17-21. [DOI: 10.1002/chir.22542] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 09/03/2015] [Accepted: 09/09/2015] [Indexed: 12/24/2022]
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9
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Stereolability of Chiral Ruthenium Catalysts With Frozen NHC Ligand Conformations Investigated by Dynamic-HPLC. Chirality 2015; 27:685-92. [DOI: 10.1002/chir.22487] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 06/24/2015] [Accepted: 07/06/2015] [Indexed: 11/07/2022]
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10
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Redwood C, Ratheesh Kumar VK, Hutchinson S, Mallory FB, Mallory CW, Clark RJ, Dmitrenko O, Saltiel J. Photoisomerization ofcis-1,2-di(1-Methyl-2-naphthyl)ethene at 77 K in Glassy Media. Photochem Photobiol 2014; 91:607-15. [DOI: 10.1111/php.12367] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 10/06/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher Redwood
- Department of Chemistry and Biochemistry; The Florida State University; Tallahassee FL
| | - V. K. Ratheesh Kumar
- Department of Chemistry and Biochemistry; The Florida State University; Tallahassee FL
| | - Stuart Hutchinson
- Department of Chemistry and Biochemistry; The Florida State University; Tallahassee FL
| | | | - Clelia W. Mallory
- Department of Chemistry; University of Pennsylvania; Philadelphia PA
| | - Ronald J. Clark
- Department of Chemistry and Biochemistry; The Florida State University; Tallahassee FL
| | - Olga Dmitrenko
- Department of Chemistry and Biochemistry; University of Delaware; Newark DE
| | - Jack Saltiel
- Department of Chemistry and Biochemistry; The Florida State University; Tallahassee FL
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11
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Tan L, Parker KA, Sampson NS. A Bicyclo[4.2.0]octene-Derived Monomer Provides Completely Linear Alternating Copolymers via Alternating Ring-Opening Metathesis Polymerization (AROMP). Macromolecules 2014; 47:6572-6579. [PMID: 25328246 PMCID: PMC4196745 DOI: 10.1021/ma5012039] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 09/01/2014] [Indexed: 12/26/2022]
Abstract
Strained bicyclic carbomethoxy olefins were utilized as substrates in alternating ring-opening metathesis polymerization and found to provide low-dispersity polymers with novel backbones. The polymerization of methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate with cyclohexene in the presence of the fast-initiating Grubbs catalyst (H2IMes)(3-Br-Pyr)2Cl2Ru=CHPh leads to a completely linear as well as alternating copolymer, as demonstrated by NMR spectroscopy, isotopic labeling, and gel permeation chromatography. In contrast, intramolecular chain-transfer reactions were observed with [5.2.0] and [3.2.0] bicyclic carbomethoxy olefins, although to a lesser extent than with the previously reported monocyclic cyclobutenecarboxylic ester monomers [Song A.; Parker K. A.; Sampson N. S.J. Am. Chem. Soc.2009, 131, 3444]. Inclusion of cyclohexyl rings fused to the copolymer backbone minimizes intramolecular chain-transfer reactions and provides a framework for creating alternating functionality in a one-step polymerization.
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Affiliation(s)
- Li Tan
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Kathlyn A. Parker
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Nicole S. Sampson
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
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12
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Sabia R, Ciogli A, Pierini M, Gasparrini F, Villani C. Dynamic high performance liquid chromatography on chiral stationary phases. Low temperature separation of the interconverting enantiomers of diazepam, flunitrazepam, prazepam and tetrazepam. J Chromatogr A 2014; 1363:144-9. [DOI: 10.1016/j.chroma.2014.07.097] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 07/25/2014] [Accepted: 07/28/2014] [Indexed: 10/24/2022]
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13
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Testa B, Vistoli G, Pedretti A. Small Molecules as Exemplars of Emergent Properties and Diversification into the ‘Adjacent Possible’. Chem Biodivers 2014; 11:1309-29. [DOI: 10.1002/cbdv.201400177] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Indexed: 11/11/2022]
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14
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Redwood C, Kumar VKR, Hutchinson S, Mallory FB, Mallory CW, Dmitrenko O, Saltiel J. Four-Component Fluorescence of trans-1,2-Di(1-methyl-2-naphthyl)ethene at 77 K in Glassy Media. Conformational Subtleties Revealed. J Phys Chem A 2014; 118:10575-86. [DOI: 10.1021/jp5056478] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher Redwood
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
| | - V. K. Ratheesh Kumar
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Stuart Hutchinson
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Frank B. Mallory
- Department
of Chemistry, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, United States
| | - Clelia W. Mallory
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States,
| | - Olga Dmitrenko
- Department
of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Jack Saltiel
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
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