Experimental and theoretical studies on cis-dioxomolybdenum(VI) complexes of ONN-donor~thiosemicarbazone

Authors: BERAT İLHAN CEYLAN, AYBERK YILMAZ, OLCAY BÖLÜKBAŞI YALÇINKAYA, BAHRİ ÜLKÜSEVEN

Abstract: Cis-dioxomolybdenum(VI) chelate complexes with 5-chloro-2-hydroxybenzophenone S-methyl-4-phenylthiose- micarbazone (L) were synthesized in the general formula (MoO$_{2}$(L)D), where D is an odd- or even-numbered alcohol (methanol (1), ethanol (2), n-propanol (3), n-butanol (4), and allyl alcohol (5)). The structures of 1-5 were verified by elemental analysis, Fourier transform infrared (FT-IR), and $^{1}$H NMR spectra. Complex 5 crystallizes in the monoclinic space group P21/n, and its crystalline data showed a dimeric structure formed by a pair of intermolecular hydrogen bonds with 1.92 Å. These dimers are stacked in a similar crystalline structure as a single molecule. The experimental data were compared with the theoretical results obtained by the quantum chemical calculations of the DFT/B3LYP method with LANL2DZ basis set. A detailed interpretation of the FT-IR spectra of the studied compounds was performed based on the total energy distribution. In order to investigate the electronic structures and the UV-Vis spectrum of complex 5, time-dependent density functional theory calculation was taken into account. The interaction energies between the odd- and even-numbered alcohols and remaining parts of complexes 1-4 were evaluated with the help of natural bonding orbital analysis. In addition, the basis set superposition error correction energies were calculated. The results were evaluated by considering the coordinated alcohols with an even number of carbon atoms to have much higher interaction energy than the next lower homologous alcohols with an odd number of carbon atoms.

Keywords: Thiosemicarbazone, vibrational spectra, density functional theory, time-dependent density functional theory, basis set superposition error, natural bonding orbital

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