MOLECULAR AND ELECTRONIC STRUCTURES OF A NEW RUTHENIUM-TUNGSTEN BIMETALLIC COMPLEX USING DENSITY FUNCTIONAL THEORY CALCULATIONS (Struktur Molekul Dan Elektronik Kompleks Dwilogam Rutenium-Tungsten Berdasarkan Pengiraan Teori Fungsi Ketumpatan)

A potential dye sensitizer material for solar cell composed of a ruthenium-(4, 4’dimethyl-2, 2′-bipyridine)-isothiocyanatotungsten-[bis-(phenyl-1, 2-ethilenodithiolenic)] bimetallic complex structure was successfully developed using Density Functional Theory (DFT) calculations. The optimal structure was realized by calculations using the generalized gradient approximation (GGA) framework in a double numeric plus polarization (DNP) basis set using the following three functional methods: Becke-Pardew (BP), Becke-Lee-Yang-Parr (BLYP) and Perdew-Burke-Ernzerhof (PBE). The PBE calculation gave a structure with bond lengths and angles that approximated the experimental data. The restricted-spin calculation of PBE found that BM has 339 molecular orbitals in which the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are located at orbital numbers 312 and 313, respectively. The HOMO was delocalized over the W(S2C2) ring, the ruthenium metal center and the thiocyanate bridging ligand. In contrast, the LUMO was found mainly at the bipyridyl ligand with a small contribution from the ruthenium metal center. Electron excitation from the HOMO  LUMO occurred at 2964 nm with an excitation energy of 0.42 eV, which is depicted by the charge transfer from one metal to another (intervalence charge transfer, IVCT) or as a manifestation of the NCS bridging ligand.