Proposal of a Fermi-Dirac-Derived Reactivity Descriptor: Beyond the Frontier MO Model.

In this paper, we derive a reactivity descriptor stemming from the Fermi-Dirac population scheme, applied to density functional calculations on molecular systems. Assuming that molecular orbitals only marginally change when temperature is slightly increased from 0 K, we study the response of electron density to a change in temperature. Connection with usual conceptual density functional theory descriptors is made, and the T-variation of electron density for some representative examples is given and discussed.

Spectroscopic and structural studies, thermal characterization, optical proprieties and theoretical investigation of 2-aminobenzimidazolium tetrachlorocobaltate(II).

In this study we present the crystal structure, spectroscopic and thermal behavior, Hirshfeld surface analysis, and DFT calculations of a new organic-inorganic hybrid compound (C7H8N3)2[CoCl4]. This compound crystallizes in the centrosymmetric space group P1¯. Single-crystal X-ray diffraction analysis indicates that structure consists of a succession of mixed layers formed by organic cations and inorganic anions parallel to the (001) plane and propagate according to the c-axis. Layers further are assembled into a 3D supramolecular architecture through N-H…Cl hydrogen bonds and π…π interactions. The peak positions of the experimental PXRD pattern are in agreement with the simulated ones from the crystal structure, indicating phase purity of the title compound. The presence of the different functional groups and the nature of their vibrations were identified by ATR-FTIR and FT-Raman spectroscopies. The tetrahedral environment of Co2+ was confirmed by UV-visible spectroscopy, where the spectrum shows three weak absorption bands in the visible range due to d-d electronic transitions 4A2(F) → 4T2(F), 4A2(F) → 4T1(F) and 4A2(F) → 4T1(P) typical of Co(II) coordination compounds. The direct and indirect optical band gap values were determined by Tauc method. The optimized structure and calculated vibrational frequencies were obtained by density functional theory (DFT) using B3LYP functional. TGA and DSC coupled to mass spectrometry (MS) experiments under argon atmosphere in the temperature range (25-950 °C) were carried out in order to determine the thermal stability of the title compound.