: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Herein we present an open-source program automating the post-treatment of solid-state ab initio calculations performed with VASP, the most used solid-state simulation package. The program plots Density of States (DOS) and Band Diagrams, enabling the user to conduct efficiently a detailed study of electronic properties of a material. Our tool includes a complete module dedicated to point defects studies, proposing various corrections which can be activated at will and innovative property calculations such as defect concentrations. This is the first program of its kind to offer a direct plot of the stability domain of the studied matrix with respect to its components' chemical potentials. We also implemented the retrieval of optical indices ɛ1 and ɛ2 , the computation of the refractive and extinction coefficients (n, k) and the reflexivity R of the material. All features of the piece of software are available through a thoroughly designed user-friendly, elegant and efficient Graphical User Interface (GUI) to be accessible to material scientists with various expertises, from both the experimental and theoretical sides. All figures are of publishable quality and can be customized as desired. © 2018 Wiley Periodicals, Inc.

PyDEF 2.0: An Easy to Use Post-treatment Software for Publishable Charts Featuring a Graphical User Interface.

Machine Learning and Big-Data in Computational Chemistry

https://par.nsf.gov/servlets/purl/10143070

Group-transfer chemistry at transition metal centers in bulky alkoxide ligand environments

The processing of the input and output files of quantum chemical calculations often necessitates a spreadsheet as a key component of the workflow. Spreadsheet packages with a built-in programming language editor can automate the steps involved and thus provide a direct link between processing files and the spreadsheet. This helps to reduce user-interventions as well as the need to switch between different programs to carry out each step. The ExcelAutomat tool is the implementation of this method in Microsoft Excel (MS Excel) using the default Visual Basic for Application (VBA) programming language. The code in ExcelAutomat was adapted to work with the platform-independent open-source LibreOffice Calc, which also supports VBA. ExcelAutomat provides an interface through the spreadsheet to automate repetitive tasks such as merging input files, splitting, parsing and compiling data from output files, and generation of unique filenames. Selected extracted parameters can be retrieved as variables which can be included in custom codes for a tailored approach. ExcelAutomat works with Gaussian files and is adapted for use with other computational packages including the non-commercial GAMESS. ExcelAutomat is available as a downloadable MS Excel workbook or as a LibreOffice workbook.

ExcelAutomat: a tool for systematic processing of files as applied to quantum chemical calculations

https://par.nsf.gov/servlets/purl/10143069

Tying the alkoxides together: an iron complex of a new chelating bulky bis(alkoxide) demonstrates selectivity for coupling of non-bulky aryl nitrenes.

Density Functional Theory (DFT)-based Global reactivity descriptor calculations have emerged as powerful tools for studying the reactivity, selectivity, and stability of chemical and biological systems. A Python-based module, PyGlobal has been developed for systematically parsing a typical Gaussian outfile and extracting the relevant energies of the HOMO and LUMO. Corresponding global reactivity descriptors are further calculated and the data is saved into a spreadsheet compatible with applications like Microsoft Excel and LibreOffice. The efficiency of the module has been accounted by measuring the time interval for randomly selected Gaussian outfiles for 1000 molecules. © 2016 Wiley Periodicals, Inc.

PyGlobal: A toolkit for automated compilation of DFT‐based descriptors

Heterocoupling of Different Aryl Nitrenes to Produce Asymmetric Azoarenes Using Iron–Alkoxide Catalysis and Investigation of the Cis–Trans Isomerism of Selected Bulky Asymmetric Azoarenes

Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]Ph (H2[OO]Ph = [1,1':4',1''-terphenyl]-2,2''-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]Ph(THF)2 (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr2([OO]Ph)2 (in CH2Cl2/THF). The electronic structure and bonding in Cr[OO]Ph(THF)2 were probed by density functional theory calculations. Isolated Cr2([OO]Ph)2 undergoes facile reaction with 4-MeC6H4N3, 4-MeOC6H4N3, or 3,5-Me2C6H3N3 to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]Ph(N(4-MeC6H4))2 was confirmed by X-ray crystallography. The reaction of Cr2([OO]Ph)2 with bulkier azides N3R (MesN3, AdN3) forms paramagnetic products, formulated as Cr[OO]Ph(NR). The attempted formation of a Cr-alkylidene complex (using N2CPh2) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]Ph(NNCPh2)2. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr2([OO]Ph)2 or H2[OO]Ph with NO+ leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

Various valuable properties of azoarenes ("azo dyes"), including their vivid colors and their facile cis-trans photoisomerization, lead to their wide use in the chemical industry. As a result, ∼700 000 metric tons of azo dyes are produced each year. Most currently utilized synthetic methods towards azoarenes involve harsh reaction conditions and/or toxic reagents in stoichiometric amounts, which may affect selectivity and produce significant amounts of waste. An efficient alternative method towards this functional group includes transition metal catalyzed nitrene coupling. This method is generally more sustainable compared with most stoichiometric methods as it uses only catalytic amounts of co-reactants (metal catalysts), requires easily synthesizable organoazide precursors, and forms only dinitrogen as a by-product of catalysis. During the last decade, several catalytic systems were reported, and their reactivity was investigated. This perspective article will review these systems, focusing on various nitrene coupling mechanisms, and the substrate scope for each system. Particular attention will be devoted to the iron-alkoxide catalytic systems investigated in the PI's laboratory. The design and structural features of several generations of iron bis(alkoxide) complexes will be discussed, followed by the structure-activity studies of these catalysts in nitrene homo- and heterocoupling.

Sudheer S. Kurup

Papers

Tying the alkoxides together: an iron complex of a new chelating bulky bis(alkoxide) demonstrates selectivity for coupling of non-bulky aryl nitrenes.

PyGlobal: A toolkit for automated compilation of DFT‐based descriptors

Heterocoupling of Different Aryl Nitrenes to Produce Asymmetric Azoarenes Using Iron–Alkoxide Catalysis and Investigation of the Cis–Trans Isomerism of Selected Bulky Asymmetric Azoarenes

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

Catalytic synthesis of azoarenes via metal-mediated nitrene coupling.