New dithiolene derivatives as coordination chromophores: structural, spectroscopic, electrochemical, Hirshfeld surface analyses, and in-vitro cytotoxicity

Seven substituted dithiolene systems with acetylacetonate, 3,4-dimethylpyrazole (HPz), and 3,4-dimethoxybenzyl moieties were synthesized by nucleophilic substitution, cyclocondensation, and transchalcogenation reactions. The seven compounds were characterized by NMR and X-ray diffraction techniques. The single-crystal X-ray diffraction analysis revealed that 4,5-bis[(2,4-dioxopentan-3-yl)sulfanyl]-1,3-dithiol-2-one, C₁₃H₁₄O₅S₄ or DMIO(acac)₂, and 4,5-bis[(3,5-dimethylpyrazol-4-yl)sulfanyl]-1,3-dithiole-2-thione methanol monosolvate, C₁₃H₁₄N₄S₅·CH₃OH or DMIT(HPz)₂, crystallized in the triclinic P1̄ and monoclinic P2₁/n space groups, respectively, while 4,5-bis[(3,4-dimethoxybenzyl)sulfanyl]-1,3-dithiole-2-thione, C₂₁H₂₂O₄S₅ or DMIT(3,4-dimethoxybenzyl)₂, and 4,5-bis[(3,4-dimethoxybenzyl)sulfanyl]-1,3-dithiol-2-one, C₂₁H₂₂O₅S₄ or DMIO(3,4-dimethoxybenzyl)₂, crystallized in the monoclinic space groups P2₁/n and P2₁/c, respectively. Methyl 4-({[5-({[4-(methoxycarbonyl)phenyl]methyl}sulfanyl)-2-sulfanylidene-1,3-dithiol-4-yl]sulfanyl}methyl)benzoate, C₂₁H₁₈O₄S₅ or DMIT(4-methylbenzoate)₂, and methyl 4-({[5-({[4-(methoxycarbonyl)phenyl]methyl}sulfanyl)-2-oxo-1,3-dithiol-4-yl]sulfanyl}methyl)benzoate, C₂₁H₁₈O₅S₄ or DMIO(4-methylbenzoate)₂, crystallized in the orthorhombic P2₁2₁2₁ and monoclinic P2₁/n space groups, respectively. Similarly, 4-{[(5-{[(4-carboxyphenyl)methyl]sulfanyl}-2-oxo-1,3-dithiol-4-yl)sulfanyl]methyl}benzoic acid, C₁₉H₁₄O₅S₄ or DMIO(4-methylbenzoic acid)₂, crystallized in the monoclinic space group P2₁/c. The molecular packings of the seven crystalline compounds were stabilized by a variety of intermolecular O...H, H...H, C...H, S...H, S...S, S...O, and N...H interactions, depending on the substituent group. Hirshfeld surface analysis confirmed the presence of the above-mentioned interactions and the percentage contributions of the interatomic contacts were determined by 2D fingerprint plots in the total Hirshfeld surface. Studies of the antiproliferative activity against the NCI-60 cell line panel were performed for selected 2-oxo-1,3-dithiole-4,5-dithiolate (DMIO) derivatives.