Copper(I) Complexes with Thiourea Derivatives as Ligands: Revealing Secrets of Their Bonding Scheme

We have synthesized and characterized five copper(I) complexes with unsymmetrically substituted thiourea ligands. These include two coordination polymers, [Cu((SNH)-N-tu)Br](n) and [Cu(S-tu(Py)NH)Br](n), two dinuclear complexes, [Cu-2((SNH)-N-tu)(4)Br-2] and [Cu-2(S-tu(Py)NH)(2)Br-2(MeCN)(2)], and one hexanuclear complex, [Cu-6((SN)-N-tu)(6)]. The Cu atoms of the coordination polymers are connected through alternating thione and bromide bridges and the dimeric structures through thione bridges. The thionebridged structures show similarities with the biologically highly relevant CuA center in its fully reduced oxidation state. Three of the complexes were further investigated by using DFT, including a full orbital analysis utilizing fragment orbitals (FOs) and overlap populations (OPs). The bonding motifs of the dinuclear complexes are similar to that of the CuA complex, whereas the analysis of the hexanuclear species showed the influence of the ligands on the core and hence on its electronic structure. Moreover, a comparative analysis of related dinuclear and hexanuclear copper- sulfur systems is presented.