Based on experimental results and DFT studies, a detailed reaction mechanism is presented for the CuNPs/TiO ₂ -catalysed hydrothiolation of activated alkynes with thiols bearing a catechol group.

Coordination polymer particles (CPPs) with catechol functionalities present significant potential for various applications. To elucidate their structural features, we synthesized CPPs using bidentate bis-catechol and catechol–pyridine ligands and employed both computational and spectroscopic techniques. The results reveal distinct coordination environments: a four-center coordination for catechol–catechol and an octahedral coordination for catechol–pyridine. Experimental UV-Vis, IR, and Raman spectroscopic analyses confirmed these findings, further supporting the accuracy of the computational model.

Copper nanoparticles (CuNPs) supported on TiO₂ have shown to effectively catalyze the synthesis of Z-alkenyl sulfides from activated alkynes and thiol derivatives, through an anti-Markovnikov process. Activated alkynes bearing an adjacent electron-withdrawing group gave good to excellent products conversions, while the unactivated alkynes did not react. In order to give an explanation to the reactivity observed from the experimental results and to know the most simple and representative structure of the catalyst, density functional theory (DFT) computational studies have been applied.

A recently published article by our research group demonstrated that the hydrothiolation of activated alkynes is a successful way to functionalize thiols bearing catechols. The reaction was promoted by the CuNPs/TiO₂ nanocatalyst and was regio- and stereoselective towards the anti-Markovnikov Z-vinyl sulfide with good to excellent yields (47–97%). The scope of the reaction was evaluated and, based on experimental observations, the reaction mechanism was investigated through DFT studies. Theoretical results and experimental data were consistent with a reaction mechanism based on a copper-catalyzed anti-Markovnikov hydrothiolation process that favors the formation of the Z-vinyl sulfide.

DFT calculations were applied to an iron/catechol derivative system to investigate their effect on the structure of CPPs as a function of (a) metal valence—Fe⁺² and Fe⁺³ in high- and low-spin states; (b) type of chelating groups in the catechol derivatives and their geometries; and (c) the aliphatic chain length between two chelating groups in a model polydentate ligand. The results indicate that catechol-pyridine and bis-catechol ligands, with Fe⁺³ salts, are promising combinations to synthesize CPPs. In addition, the inclusion of an aliphatic chain with four carbons between the chelating groups could enhance polymerization versus monomer formation.