THEORETICAL INVESTIGATION OF CHARGE TRASFER EFFECT IN 3-METHYLTHIO-4-PHENYL-5-PHENYLAMINO-1,2,4-TRIAZOL-1-IUM HEXABROMOTELLURATE

Abstract

Hexabromotellurates of some heterocyclic organic bases exhibit semiconductor properties. Promising photoelectric properties are demonstrated by a number of hexaiodotellurate-containing defect perovskites. The study of hybrid organic-inorganic compounds is an urgent task of modern science, as such new functional materials can be used as effective converters of solar energy. In our previous works, a method for the synthesis of hexabromotellurate of 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazol-1-ium A+ was developed and its main photoelectric properties were theoretically investigated. In this work, it was decided to continue the study of the properties of this hexabromotellurate, and the use of quantum chemical methods allowed it to investigate the effect of charge transfer between the hexabromotellurate anion and the organic cation A+.
 Geometry optimization of the [A-TeBr6]– with the charge of –1 was performed by the semiempirical method PM7 in the program MOPAC2016 and by the DFT method PBE/λ1 in the program PRIRODA 19. The charge transfer effect was investigated based on the electron density generated by the ωB97X-D3/def2-SVP method in ORCA 4.2.1. The effects of the medium (gas phase, chloroform, tetrahydrofuran, n-octanol, acetone, acetonitrile, water) were taken into account using the CPCM model. The Multiwfn 3.8 package was used to analyze the electron density.
 From the analysis of the isosurface of the electrostatic potential, carried out by using the "charge decomposition analysis" method, and also from the analysis of the total charges of the fragments A+ and TeBr62–, it has been found that in the [A-TeBr6]– associate a great charge transfer from the anion to the organic cation is present. The complex orbitals HOMO and HOMO–1 in the [A-TeBr6]– associate correspond to the cation's HOMO and the anion's HOMO, respectively. These two orbitals generally remain undisturbed during the formation of the complex. It has been established that with the medium's dielectric constant increase, the number of electrons transferred from the anion to the cation decreases markedly, which is consistent with Coulomb's law. It is noted that even in the case of non-polar solvents, this kind of calculations must take into account the dielectric constant of the medium.