4-(p-X-phenyl)thiosemicarbazone of napthaldehyde {where X = Cl (HL¹) and X = Br (HL²)}, thiosemicarbazone of quinoline-2-carbaldehyde (HL³) and 4-(p-fluorophenyl)thiosemicarbazone of salicylaldehyde (H₂L⁴) and their copper(I) {[Cu(HL¹)(PPh₃)₂Br]·CH₃CN (1) and [Cu(HL²)(PPh₃)₂Cl]·DMSO (2)} and copper(II) {[(Cu₂L³ ₂Cl)₂(μ-Cl)₂]·2H₂O (3) and [Cu(L⁴)(Py)] (4)} complexes are reported herein. The synthesized ligands and their copper complexes were successfully characterized by elemental analysis, cyclic voltammetry, NMR, ESI-MS, IR and UV-Vis spectroscopy. Molecular structures of all the Cu(I) and Cu(II) complexes have been determined by X-ray crystallography. All the complexes (1–4) were tested for their ability to exhibit DNA-binding and -cleavage activity. The complexes effectively interact with CT-DNA possibly by groove binding mode, with binding constants ranging from 10⁴ to 10⁵ M⁻¹. Among the complexes, 3 shows the highest chemical (60%) as well as photo-induced (80%) DNA cleavage activity against pUC19 DNA. Finally, the in vitro antiproliferative activity of all the complexes was assayed against the HeLa cell line. Some of the complexes have proved to be as active as the clinical referred drugs, and the greater potency of 3 may be correlated with its aqueous solubility and the presence of the quinonoidal group in the thiosemicarbazone ligand coordinated to the metal.

The salicylhydrazone of anthranilhydrazide (H₂L) reacted with MoO₂(acac)₂ in refluxing alcohols to yield compounds of the general formula MoO₂L(ROH) (where R = CH₃, C₂H₅, n-C₃H₇, n-C₄H₉). The complex MoO₂L(C₂H₅OH) is found to undergo facile reaction with heterocyclic bases to form MoO₂L(Q)-type complexes where Q = pyridine, 4-picoline, imidazole and substituted imidazoles. Single crystal X-ray structural studies on the ligand H₂L (1) and the complexes MoO₂L(C₂H₅OH) (2) and MoO₂L(Imz) (3) indicate that the free ligand exists in its keto form, but in the two complexes 2 and 3 the ligand coordinates to the MoO₂ ²⁺ core through the enolate oxygen, the phenolate oxygen and the azomethine nitrogen. Reaction of MoO₂L(C₂H₅OH) with PPh₃ in CH₃CN under dry dinitrogen, in the absence and presence of bipy, produced Mo^IVOL (2a) (brown) and Mo^IVOL(bipy) (2b) (green) respectively along with Ph₃PO. This reaction is reminiscent of the oxotransfer reaction from the MoO₂ ⁺² core of a molybdoenzyme to the substrate PPh₃. Complexes 2 and 3 crystallized in the P2₁/n and P2₁/c space groups respectively and for both of them Z = 4. The structures clearly show that 2 and 3 have distorted octahedral coordination environments in which the Mo–O(ethanol) bond of 2 and the Mo–N (imidazole) bond of 3 are significantly longer than is usually observed. This is indicative of the weak bonding of ethanol and imidazole to the MoO₂ ²⁺ core and points to the inherent weakness of the sixth coordination position of the coordination polyhedron of the MoO₂ ²⁺ core in MoO₂L(C₂H₅OH) and MoO₂L(Imz).