Synthesis, characterization and computational investigations of new alkyl [2,4-methoxyphenyl)phosphonodithioato]Ni(II) complexes and potential anticancer, antioxidant, and antimicrobial studies of their ligands

Abstract

New alkylphosphonodithioic acids (HS(S)P-(Ar)(ORn), Ar=2,4-methoxyphenyl-; R1= ethyl-, 1; R2= n propyl-, 2) in anionic form were obtained from the reaction between 2,4-bis(2,4-methoxyphenyl)-1,3,2,4-dithiaphosphetane-2,4-disulfide, SAV-A2, and alcohol, ethanol or n-propanol. Crude viscous acids were converted to their stable salts, [+NH4][- S2P(Ar)(OEt)]- (3) and [+NH4][- S2P(Ar)(OPrn)] (4) by treating with dry ammonia gas. Compounds 3 and 4, known as phosphonodithoates, react with Ni(II) cation to form new nickel(II) phosphonodithioato complexes, [Ni(S2P(Ar)(OEt))2] (5) and [Ni(S2PS2P(Ar)(OPrn))2] (6), respectively. The characterization of compounds 3-6 was achieved through spectroscopic techniques. Single-crystal X-ray analyses were done for 5 and 6. Hirshfeld surface analysis and 2D fingerprint plotting analyses were applied to show the relevant significant interaction cites in the complexes. The optimized geometries, the chemical parameters, frontier molecular orbitals and molecular electrostatic potential surfaces (MEPs) of 5 and 6 were predicted using Density Functional Theory (DFT) calculations. Compounds 3 and 4 were screened in human cancer cell lines including breast (MCF-7) and lung (A549) in vitro. The results demonstrated that these two compounds have no cytotoxic effects on MCF-7 and A549. Further investigations revealed the high antioxidant activity and weak antimicrobial activity of compounds. Compound 4 displayed relatively stronger antibacterial activity on the microorganisms and lower 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity as compared to compound 3.