Geometrical structure, electronic and nonlinear optical properties of square-planar heteroleptic complexes containing bypridine and pyrazine dithiolate derivatives as dye-sensitized solar cell: A DFT study

The structural stability, optoelectronic and nonlinear optical (NLO) properties of the designed heteroleptic complexes [M (diimine)(dithiolate)] {M = Ni, Pd and Pt; diimine = 2,2 '-bipyridine (bpy); dithiolate = pyrazine-2,3-dithiolate (pdt), uinoxaline-2,3-dithiolate (qdt) and 2,5-dicyano-2,3-dithiolatepyrazine (dcdmp)} were determined by means of the density functional theory (DFT) method and time-dependent-DFT calculations. Natural bond orbital analyses are also performed for scrutinizing the structural properties of the considered heteroleptic complexes. This study compared the sensitization properties of all complexes in terms of their electronic properties, such as molecular orbital distribution, gap energy (E-g), absorbed wavelength (lambda(max)), light-harvesting efficiency (LHE), charge transfer descriptors, dipole moment (mu), polarizability (alpha) and first hyperpolarizability (beta(0)). Based on the obtained results, it can be induced that the change of metal center and dithiolate ligands plays a key role in tuning optoelectronic properties, especially the LHE and hyperpolarizability. Also the results reveal that Pt as metal center with qdt ligand considerably increases their electronic and NLO properties. Moreover, the thermodynamic analysis showed that the formation of these complexes is exothermic, and the synthesis of all considered complexes will be possible at 298 K and 1 atm. To sum up, it seems that these designed complexes could be introduced as promising new electro-optical materials.