A new homoleptic dithiolene tungsten complex, tris-{1,2-bis(3,5-dimethoxyphenyl)-1,2-ethylenodithiolene-S,S'}tungsten, was successfully synthesized via a reaction of the thiophosphate ester and sodium tungstate. The thiophosphate ester was prepared from 3,5-dimethoxybenzaldehyde via benzoin condensation to produce the intermediate 1,2-bis-(3,5-dimethoxyphenyl)-2-hydroxy-ethanone compound, followed by a reaction of the intermediate with phosphorus pentasulfide. FTIR, UV-Vis spectroscopy, 1H NMR and 13C NMR and elemental analysis confirmed the product as tris{1,2-bis-(3,5-dimethoxyphenyl)-1,2-ethylenodithiolene-S,S'}tungsten with the molecular formula of C54H54O12S6W. Crystals of the product adopted a monoclinic system with space group of P2(1)/n, where a=12.756(2) Å, b=21.560(3) Å, c=24.980(4) Å and β=103.998(3)°. Three thioester ligands were attached to the tungsten as bidentate chelates to form a distorted octahedral geometry. Density functional theory calculations were performed to investigate the molecular properties in a generalized-gradient approximation framework system using Perdew-Burke-Ernzerhof functions and a double numeric plus polarization basis set. The HOMO was concentrated on the phenyl ligands, while the LUMO was found along the W(S2C2)3 rings. The theoretical optical properties showed a slight blue shift in several low dielectric solvents. The solvatochromism effect was insignificant for high polar solvents.
The presence of Ti3+ in the structure of TiO2 nanotube arrays (NTs) has been shown to enhance the photoelectrochemical (PEC) water-splitting performance of these NTs, leading to improved results compared to pristine anatase TiO2 NTs. To further improve the properties related to PEC performance, we successfully produced TiO2 NTs using a two-step electrochemical anodization technique, followed by annealing at a temperature of 450 °C. Subsequently, Mo2C was decorated onto the NTs by dip coating them with precursors at varying concentrations and times. The presence of anatase TiO2 and Ti3O5 phases within the TiO2 NTs was confirmed through X-ray diffraction (XRD) analysis. The TiO2 NTs that were decorated with Mo2C demonstrated a photocurrent density of approximately 1.4 mA cm-2, a value that is approximately five times greater than the photocurrent density exhibited by the bare TiO2 NTs, which was approximately 0.21 mA cm-2. The observed increase in photocurrent density can be ascribed to the incorporation of Mo2C as a cocatalyst, which significantly enhances the photocatalytic characteristics of the TiO2 NTs. The successful deposition of Mo2C onto the TiO2 NTs was further corroborated by the characterization techniques utilized. The utilization of field emission scanning electron microscopy (FESEM) allowed for the observation of Mo2C particles on the surface of TiO2 NTs. To validate the composition and optical characteristics of the decorated NTs, X-ray photoelectron spectroscopy (XPS) and UV absorbance analysis were performed. This study introduces a potentially effective method for developing efficient photoelectrodes based on TiO2 for environmentally sustainable hydrogen production through the use of photoelectrochemical water-splitting devices. The utilization of Mo2C as a cocatalyst on TiO2 NTs presents opportunities for the advancement of effective and environmentally friendly photoelectrochemical (PEC) systems.