Reactivity of CuI and CuBr toward Et 2 S: a Reinvestigation on the Self-Assembly of Luminescent Copper(I) Coordination Polymers (original) (raw)

CuI reacts with SEt 2 in hexane to afford the known strongly luminescent 1D coordination polymer [(Et 2 S) 3 {Cu 4 -(μ 3 -I) 4 }] n (1). Its X-ray structure has been redetermined at 115, 235, and 275 K in order to address the behavior of the cluster-centered emission and is built upon Cu 4 (μ 3 -I) 4 cubane-like clusters as secondary building units (SBUs), which are interconnected via bridging SEt 2 ligands. However, we could not reproduce the preparation of a coordination polymer with composition [(Et 2 S) 3 {Cu 4 (μ 3 -Br) 4 }] n as reported in Inorg. Chem. 1975Chem. , 14, 1667. In contrast, the autoassembly reaction of SEt 2 with CuBr results in the formation of a novel 1D coordination polymer of composition [(Cu 3 Br 3 )(SEt 2 ) 3 ] n (2). The crystal structure of 2 has been solved at 115, 173, 195, and 235 K. The framework of the luminescent compound 2 consists of a corrugated array with alternating Cu(μ 2 -Br) 2 Cu rhomboids, which are connected through two bridging SEt 2 ligands to a tetranuclear open-cubane Cu 4 Br 4 SBU, ligated on two external Cu atoms with one terminal SEt 2 . The solid-state luminescence spectra of 1 and 2 exhibit intense halide-to-metal chargetransfer emissions centered at 565 and 550 nm, respectively, at 298 K. A correlation was also noted between the change in the full width at half-maximum of the emission band between 298 and 77 K and the relative flexibility of the bridging ligand. The emission properties of these materials are also rationalized by means of density functional theory (DFT) and time-dependent DFT calculations performed on 1.