Physical Sciences and Mathematics | Open Access Articles

Reactivity Of (3-Methylpentadienyl)Iron(1+) Cation: Late-Stage Introduction Of A (3-Methyl-2z,4-Pentadien-1-Yl) Side Chain, Subhabrata Chaudhury, Shukun Li, William A. Donaldson

Chemistry Faculty Research and Publications

The 3-methyl-2Z,4-pentadien-1-yl sidechain is found in various sesquiterpenes and diterpenes. A route for the late stage introduction of this functionality was developed which relies on nucleophilic attack on the (3-methylpentadienyl)iron(1+) cation, followed by oxidative decomplexation. This methodology was applied to the synthesis of the proposed structure of heteroscyphic acid A methyl ester. Realization of this synthesis led to a correction of the proposed structure.

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A Full-Dimensional Model Of Ozone Forming Reaction: The Absolute Value Of The Recombination Rate Coefficient, Its Pressure And Temperature Dependencies, Alexander Teplukhin, Dmitri Babikov

Chemistry Faculty Research and Publications

Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro–vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is …

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Does Koopmans’ Paradigm For 1-Electron Oxidation Always Hold? Breakdown Of Ip/EOx Relationship For P-Hydroquinone Ethers And The Role Of Methoxy Group Rotation, Marat R. Talipov, Anitha Boddeda, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Koopmans’ paradigm states that electron loss occurs from HOMO, thus forming the basis for the observed linear relationships between HOMO/IP, HOMO/Eox, and IP/E_ox. In cases where a molecule undergoes dramatic structural reorganization upon 1-electron oxidation, the IP/E_oxrelationship does not hold, and the origin of which is not understood. For example, X-ray crystallography of the neutral and cation radicals of bicyclo[2.2.1]heptane-annulated p-hydroquinone ethers (^THE and ^MHE) showed that they undergo electron-transfer-induced conformational reorganization and show breakdown of the IP/E_ox relationship. DFT calculations revealed that Koopmans’ paradigm …

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From Wires To Cables: Attempted Synthesis Of 1,3,5-Trifluorenylcyclohexane As A Platform For Molecular Cables, Marat R. Talipov, Sameh H. Abdelwahed, Khushabu Thakur, Scott Reid, Rajendra Rathore

Chemistry Faculty Research and Publications

Multiple molecular wires braided together in a single assembly, termed as molecular cable, are promising next-generation materials for effective long-range charge transport. As an example of the platform for constructing molecular cables, 1,3,5-trifluorenylcyclohexane (TFC) and its difluorenyl analogues (DFCs) were systematically investigated both experimentally (X-ray crystallography) and theoretically (DFT calculations). Although the syntheses of DFCs were successfully achieved, the synthesis of TFC, which involved a similar intramolecular Friedel–Crafts cyclization as the last step, was unsuccessful. An exhaustive study of the conformational landscape of cyclohexane ring of TFC and DFCs revealed that TFC is …

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A Search For Blues Brothers: X-Ray Crystallographic/Spectroscopic Characterization Of The Tetraarylbenzidine Cation Radical As A Product Of Aging Of Solid Magic Blue, Marat R. Talipov, Mohammad M. Hossain, Anitha Boddeda, Khushabu Thakur, Rajendra Rathore

Chemistry Faculty Research and Publications

Magic blue (MB⁺˙ SbCl₆⁻ salt), i.e. tris-4-bromophenylamminium cation radical, is a routinely employed one-electron oxidant that slowly decomposes in the solid state upon storage to form so called ‘blues brothers’, which often complicate the quantitative analyses of the oxidation processes. Herein, we disclose the identity of the main ‘blues brother’ as the cation radical and dication of tetrakis-(4-bromophenyl)benzidine (TAB) by a combined DFT and experimental approach, including isolation of TAB⁺˙ SbCl₆⁻ and its X-ray crystallography characterization. The formation of TAB in aged magic blue samples occurs by a Scholl-type …

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X-Ray Structure And Properties Of The Ferrous Octaethylporphyrin Nitroxyl Complex, Nagabhushanam Kundakarla, Sergey V. Lindeman, Hafiz Md. Rahman, Michael D. Ryan

Chemistry Faculty Research and Publications

The preparation and characterization of the iron octaethylporphyrin nitroxyl ion, [Fe(OEP)(NO)⁻], is reported. The complex was synthesized by the one-electron reduction of Fe(OEP)(NO) using anthracenide as the reducing agent. The compound was isolated as the potassium (2.2.2)cryptand salt. The anion was characterized using X-ray analysis with visible and infrared spectroscopy. The spectral features of the iron nitroxyl complex were consistent with previous literature reports. The important structural changes upon reduction were a significant decrease in the Fe–N–O bond angle from 142° to 127° and an increase in the N–O bond length from that in the starting nitrosyl moiety. …

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Hydrogen-Atom Attack On Phenol And Toluene Is Ortho-Directed, Olha Krechkivska, Callan M. Wilcox, Tyler P. Troy, Klaas Nauta, Bun Chan, Rebecca Jacob, Scott A. Reid, Leo Radom, Timothy W. Schmidt, Scott H. Kable

Chemistry Faculty Research and Publications

The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge. The (1 + 1′) resonance-enhanced multiphoton ionization (REMPI) spectra of the reaction products, at m/z = parent + 1, or parent + 2 amu, were measured by scanning the first (resonance) laser. The resulting spectra are highly structured. Ionization energies were measured by scanning the second (ionization) laser, while the first laser was tuned to a specific transition. Theoretical calculations, benchmarked to the well-studied H + benzene → cyclohexadienyl radical reaction, were performed. The spectrum arising from the …

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Design And Synthesis Of Oxazoline-Based Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Jacob D. Porter, Yibiao Wu, Rajdeep S. Virdi, Alaa Shanaa, Chris Dockendorff

Chemistry Faculty Research and Publications

A new class of hybrid Lewis acid/Lewis base catalysts has been designed and prepared with an initial objective of promoting stereoselective direct aldol reactions. Several scaffolds were synthesized that contain amine moieties capable of enamine catalysis, connected to heterocyclic metal-chelating sections composed of an oxazole–oxazoline or thiazole–oxazoline. Early screening results have identified oxazole–oxazoline-based systems capable of promoting a highly diastereo- and enantioselective direct aldol reaction of propionaldehyde with 4-nitrobenzaldehyde, when combined with Lewis acids such as zinc triflate.

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Inelastic Scattering Of Identical Molecules Within Framework Of The Mixed Quantum/Classical Theory: Application To Rotational Excitations In H2 + H2, Alexander Semenov, Dmitri Babikov

Chemistry Faculty Research and Publications

Theoretical foundation is laid out for description of permutation symmetry in the inelastic scattering processes that involve collisions of two identical molecules, within the framework of the mixed quantum/classical theory (MQCT). In this approach, the rotational (and vibrational) states of two molecules are treated quantum-mechanically, whereas their translational motion (responsible for scattering) is treated classically. This theory is applied to H2 + H2 system, and the state-to-state transition cross sections are compared versus those obtained from the full-quantum calculations and experimental results from the literature. Good agreement is found in all cases. It is also found that results of MQCT, …

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A Flipped Classroom Redesign In General Chemistry, Scott Reid

Chemistry Faculty Research and Publications

The flipped classroom continues to attract significant attention in higher education. Building upon our recent parallel controlled study of the flipped classroom in a second-term general chemistry course (J. Chem. Educ., 2016, 93, 13–23), here we report on a redesign of the flipped course aimed at scaling up total enrollment while keeping discussion sizes small (i.e.,students), and maintaining equivalent contact hour load for faculty and workload for students. To that end, the course format featured lecture contact pushed outside of the classroom in the form of video lectures (mean duration 13 minutes) paired with online …

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On Stabilization Of Scattering Resonances In Recombination Reaction That Forms Ozone, Mikhail V. Ivanov, Dmitri Babikov

Chemistry Faculty Research and Publications

Calculations of energy transfer in the recombination reaction that forms ozone are carried out within the framework of the mixed quantum/classical theory and using the dimensionally reduced 2D-model of ozone molecule, with bending motion neglected. Recombination rate coefficients are obtained at room temperature for symmetric and asymmetric isotopomers of singly and doubly substituted isotopologues. The processes of resonance formation, spontaneous decay, collisional dissociation, and stabilization by bath gas (Ar) are all characterized and taken into account within the steady-state approximation for kinetics. The focus is on stabilization step, where the mysterious isotopic η-effect was thought to originate from. Our results …

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Full-Text Articles in Physical Sciences and Mathematics

Reactivity Of (3-Methylpentadienyl)Iron(1+) Cation: Late-Stage Introduction Of A (3-Methyl-2z,4-Pentadien-1-Yl) Side Chain, Subhabrata Chaudhury, Shukun Li, William A. Donaldson

Chemistry Faculty Research and Publications

A Full-Dimensional Model Of Ozone Forming Reaction: The Absolute Value Of The Recombination Rate Coefficient, Its Pressure And Temperature Dependencies, Alexander Teplukhin, Dmitri Babikov

Chemistry Faculty Research and Publications

Does Koopmans’ Paradigm For 1-Electron Oxidation Always Hold? Breakdown Of Ip/EOx Relationship For P-Hydroquinone Ethers And The Role Of Methoxy Group Rotation, Marat R. Talipov, Anitha Boddeda, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

From Wires To Cables: Attempted Synthesis Of 1,3,5-Trifluorenylcyclohexane As A Platform For Molecular Cables, Marat R. Talipov, Sameh H. Abdelwahed, Khushabu Thakur, Scott Reid, Rajendra Rathore

Chemistry Faculty Research and Publications

A Search For Blues Brothers: X-Ray Crystallographic/Spectroscopic Characterization Of The Tetraarylbenzidine Cation Radical As A Product Of Aging Of Solid Magic Blue, Marat R. Talipov, Mohammad M. Hossain, Anitha Boddeda, Khushabu Thakur, Rajendra Rathore

Chemistry Faculty Research and Publications

X-Ray Structure And Properties Of The Ferrous Octaethylporphyrin Nitroxyl Complex, Nagabhushanam Kundakarla, Sergey V. Lindeman, Hafiz Md. Rahman, Michael D. Ryan

Chemistry Faculty Research and Publications

Hydrogen-Atom Attack On Phenol And Toluene Is Ortho-Directed, Olha Krechkivska, Callan M. Wilcox, Tyler P. Troy, Klaas Nauta, Bun Chan, Rebecca Jacob, Scott A. Reid, Leo Radom, Timothy W. Schmidt, Scott H. Kable

Chemistry Faculty Research and Publications

Design And Synthesis Of Oxazoline-Based Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Jacob D. Porter, Yibiao Wu, Rajdeep S. Virdi, Alaa Shanaa, Chris Dockendorff

Chemistry Faculty Research and Publications

Inelastic Scattering Of Identical Molecules Within Framework Of The Mixed Quantum/Classical Theory: Application To Rotational Excitations In H2 + H2, Alexander Semenov, Dmitri Babikov

Chemistry Faculty Research and Publications

A Flipped Classroom Redesign In General Chemistry, Scott Reid

Chemistry Faculty Research and Publications

On Stabilization Of Scattering Resonances In Recombination Reaction That Forms Ozone, Mikhail V. Ivanov, Dmitri Babikov

Chemistry Faculty Research and Publications