The sensitive and selective chemosensor for copper(II) ions (Cu2+) was successfully optimized using the 1,5-diphenylthiocarbazone (DPT) compound. The result showed that dimethyl sulfoxide (DMSO) in a 9:1 (DMSO:water) ratio at a pH of 3 was the optimum medium for DPT to act as chemosensor of Cu2+ recognition. The DPT chemosensor did not encounter any interference from other metal ions, including Fe3+, Ag+, Cr3+, Pb2+, Mg2+, Cd2+, Zn2+, K+, Ni2+ and Co2+. The presence of Cu2+ led to an absorption peak at 658 nm, where the color changed from cantaloupe to gray-green color indicating the interaction by the formation of the DPT-Cu complex in 2:1 stoichiometry. The theoretical s-profile calculation using conductor-like screening model for real solvents (COSMO-RS) showed the compatibility of DPT with the DMSO solvent through hydrogen bonding. In the density functional theory (DFT) calculations, the formation energy of DPT and DPT-Cu were -1113.79645660 and -2435.71832681 a.u. , respectively. Under optimal conditions, a detection limit of 6.08 µM for the DPT chemosensor for Cu2+ recognition can compete with the flame atomic absorption spectroscopy (FAAS) value of 6.21 µM. Finally, DPT was able to provide less expensive, more portable and convenient chemosensor for Cu2+ recognition in environmental water samples.

In this study, a new thiosemicarbazone ligand, namely acetylpyrazine N(4)butylthiosemicarbazone (APBT), was synthesized and characterized using 1H and 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. Quantum chemical calculations were performed using density functional theory at the B3LYP/6-311++G(d,p) basis set level. The optimized molecular geometry of APBT is discussed based on X-ray structural reports from the literature. The assignment of the vibrational frequencies was done based on a potential energy distribution analysis using the vibrational energy distribution analysis (VEDA) 4 software. The energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) was evaluated to study the reactivity and stability of the compound. Global chemical reactivity and local reactivity descriptors of reactants and the product (APBT) were calculated to study the reaction mechanism. The region of interaction during the reaction to form APBT was determined using molecular electrostatic potential analysis. Finally, a preliminary study of the title compound as a cyclin-dependent kinase (CDK) inhibitor was further evaluated by performing a docking calculation.