Ternary Phenolate-Based Thiosemicarbazone Complexes of Copper(II): Magnetostructural Properties, Spectroscopic Features and Marked Selective Antiproliferative Activity against Cancer Cells

• Published in: Molecules (Basel, Switzerland) Vol. 29; no. 2; p. 431
• Main Authors: Al-Salmi, Iman K, Shongwe, Musa S
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.01.2024; MDPI
• Subjects: Cancer; Carbon; Carboxylic Acids; Cisplatin; Copper; Copper compounds; Data collection; Humans; intermolecular forces; Ligands; mononuclear and dinuclear ternary copper(II) complexes; Neoplasms; Phenanthrolines - pharmacology; Phenols; Polymers; Protons; spectroscopy; Spectrum Analysis; tetragonal distortion; thiosemicarbazone; X-ray structures; United States; mononuclear and dinuclear ternary copper(II) complexes; selective potent cytotoxicity; spectroscopy; thiosemicarbazone; intermolecular forces; X-ray structures; tetragonal distortion
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules29020431

The new diprotic ligand 3,5-di- -butylsalicylaldehyde 4-ethyl-3-thiosemicarbazone, abbreviated H (3,5- -Bu )-sal4eT, exists as the thio-keto tautomer and adopts the -configuration with respect to the imine double bond, as evidenced by single-crystal X-ray analysis and corroborated by spectroscopic characterisation. Upon treatment with Cu(OAc) ·H O in the presence of either 2,9-dimethyl-1,10-phenanthroline (2,9-Me -phen) or 1,10-phenanthroline (phen) as a co-ligand in MeOH, this thiosemicarbazone undergoes conformational transformation (relative donor-atom orientations: → ) concomitantly with tautomerisation and double deprotonation to afford the ternary copper(II) complexes [Cu{(3,5- -Bu )-sal4eT}(2,9-Me -phen)] ( ) and [Cu {3,5- -Bu )-sal4eT} (phen)] ( ). Crystallographic elucidation has revealed that complex is a centrosymmetric dimer of mononuclear copper(II) complex molecules brought about by intermolecular H-bonding. The coordination geometry at the copper(II) centre is best described as distorted square pyramidal in accordance with the trigonality index (τ = 0.14). The co-ligand adopts an axial-equatorial coordination mode; hence, there is a disparity between its two Cu-N coordinate bonds arising from weakening of the apical one as a consequence of the tetragonal distortion. The axial X-band ESR spectrum of complex is consistent with retention of this structure in solution. Complex is a centrosymmetric dimer of dinuclear copper(II) complex molecules exhibiting intermolecular H-bonding and π-π-stacking interactions. The two copper(II) centres, which are 4.8067(18) Å apart and bridged by the thio-enolate nitrogen of the quadridentate thiosemicarbazonate ligand, display two different coordination geometries, one distorted square planar (τ = 0.082) and the other distorted square pyramidal (τ = 0.33). Such dinuclear copper(II) thiosemicarbazone complexes, which are crystallographically characterised, are extremely rare. In vitro, complexes and outperform cisplatin as antiproliferative agents in terms of potency and selectivity towards HeLa and MCF-7 cancer cell lines.