Structural, spectroscopic and DFT theoretical studies of phosphorescent CuIP2S‐containing cuprous complexes

Luminescent cuprous complexes are important coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The structures of two CuIP2S‐type cuprous complexes, namely, iodido(thiourea‐κS)bis(triphenylphosphane‐κP)copper(I), [CuI(CH4N2S)(C18H15P)2] or [CuI(TU)(TPP)2] (I), and (2,3‐dihydrobenzimidazole‐2‐thione‐κS)iodidobis(triphenylphosphane‐κP)copper(I), [CuI(C7H6N2S)(C18H15P)2] or [CuI(DHBIT)(TPP)2] (II), are described. In these two structures, the complex molecules of both are constructed by one copper(I) centre, one iodide ion, two TPP ligands and one thione ligand (TU for I and DHBIT for II). The copper(I) centres of I and II are both located in a distorted CuIP2S tetrahedron and are coordinated by two P atoms from two TPP ligands, one S atom from the thione ligand and the I atom. The UV–Vis absorption and photoluminescence properties of these CuIP2S‐type cuprous complexes have been studied using crystalline powder samples. Detailed time‐dependent density functional theory (TD‐DFT) calculations and wavefunction analysis reveal that the pale‐blue–green phosphorescence emission should originate from intra‐ligand (TPP for I and DHBIT for II) charge transfer, with a small component of the metal‐to‐ligand charge transfer 3(IL+ML)CT excited state. In the two CuIP2S‐type cuprous complexes [CuI(TPP)2(TU)] (I) and [CuI(TPP)2(DHBIT)] (II), triphenylphosphane (TPP), thiourea (TU) and 2,3‐dihydrobenzimidazole‐2‐thione (DHBIT) all exhibit a terminal coordination mode. TD‐DFT calculations and wavefunction analysis demonstrate that the pale‐blue–green phosphorescence should be emitted from a metal‐perturbed triplet TPP‐centred (in I) or DHBIT‐centred (in II) excited state.