In( <scp>iii</scp> ) complexes of sulfonyldithiocarbimates as selective antineoplasic agents against human colorectal adenocarcinoma

The synthesis, antineoplasic profile, and structural aspects of six In(III) sulfonyldithiocarbimate complexes (Ph₄P[(RSO₂NCS₂)₂In], 2a-f) are described. The salts were readily obtainable with 38% to 98% yield by the water-mediated complexation of the ligand (1a-f) in the presence of In(NO₃)₃ without further purification. Spectroscopic data pointed to the formation of isomers, which were postulated as the result of three complexation modes - SS-SS, SN-SN, and SN-SS. DFT calculations furnished Δ<i>G</i>, <i>K</i>_eq, and <i>δ</i> values that indicated a preference for the SS-SS isomer. Statistical analysis of ¹³C NMR data placed ¹³CN <i>δ</i> values as efficient probes of the d-electron count of the metal in sulfonyldithiocarbimate complexes. The compounds displayed antineoplasic activity against human colorectal adenocarcinoma (HCT-116) cell lines (IC₅₀ = 3.02(21) μmol L^-1 to 5.36(42) μmol L^-1) with high selectivity compared to HaCaT cells. Moreover, an XRD analysis of a water-insoluble decomposition product of a ligand (1b) is also described, showing the formation of a supramolecular-like network and corroborating the use of the metallic complexes as biologically active compounds instead of their isolated ligands.