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Ghodrat Mahmoudi

Ghodrat Mahmoudi

Academic rank: Associate Professor
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Education: PhD.
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Research

Title
Quasi-aromatic Möbius Metal Chelates
Type
JournalPaper
Keywords
coordination compounds, C–H···H–C bonds, aromaticity phenomenon
Year
2018
Journal INORGANIC CHEMISTRY
DOI
Researchers Ghodrat Mahmoudi ، Farhad Akbari Afkhami ، Alfonso Castiñeiras ، Isabel García-Santos ، Atash V. Gurbanov, ، Fedor I. Zubkov ، Mariusz P. Mitoraj, ، Mercedes Kukułka ، Filip Sagan ، Dariusz W. Szczepanik ، Irina A. Konyaeva ، Damir A Safin

Abstract

We report the design as well as structural and spectroscopic characterizations of two new coordination compounds obtained from Cd(NO3)2·4H2O and polydentate ligands, benzilbis(pyridin-2-yl)methylidenehydrazone (LI) and benzilbis(acetylpyridin-2-yl)methylidenehydrazone (LII), in a mixture with two equivalents of NH4NCS in MeOH, namely [Cd(SCN)(NCS)(LI)(MeOH)] (1) and [Cd(NCS)2(LII)(MeOH)] (2). Both LI and LII are bound via two pyridyl-imine units yielding a tetradentate coordination mode giving rise to the 12 π electron chelate ring. It has been determined for the first time (qualitatively and quantitatively), using the EDDB electron population-based method, the HOMA index, and the ETS-NOCV charge and energy decomposition scheme, that the chelate ring containing CdII can be classified as a quasi-aromatic Möbius motif. Notably, using the methyl-containing ligand LII controls the exclusive presence of the NCS– connected with the CdII atom (structure 2), while applying LI allows us to simultaneously coordinate NCS– and SCN– ligands (structure 1). Both systems are stabilized mostly by hydrogen bonding, C–H···π interactions, aromatic π···π stacking, and dihydrogen C–H···H–C bonds. The optical properties have been investigated by diffused reflectance spectroscopy as well as molecular and periodic DFT/TD-DFT calculations. The DFT-based ETS-NOCV analysis as well as periodic calculations led us to conclude that the monomers which constitute the obtained chelates are extremely strongly bonded to each other, and the calculated interaction energies are found to be in the regime of strong covalent connections. Intramolecular van der Waals dispersion forces, due to the large size of LI and LII, appeared to significantly stabilize these systems as well as amplify the aromaticity phenomenon.