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Reactivity of CuI and CuBr toward Et2S: a Reinvestigation on the Self-Assembly of Luminescent Copper(I) Coordination Polymers

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posted on 05.07.2010, 00:00 by Michael Knorr, Abdoulaye Pam, Abderrahim Khatyr, Carsten Strohmann, Marek M. Kubicki, Yoann Rousselin, Shawkat M. Aly, Daniel Fortin, Pierre D. Harvey
CuI reacts with SEt2 in hexane to afford the known strongly luminescent 1D coordination polymer [(Et2S)3{Cu43-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 Cu43-I)4 cubane-like clusters as secondary building units (SBUs), which are interconnected via bridging SEt2 ligands. However, we could not reproduce the preparation of a coordination polymer with composition [(Et2S)3{Cu43-Br)4}]n as reported in Inorg. Chem. 1975, 14, 1667. In contrast, the autoassembly reaction of SEt2 with CuBr results in the formation of a novel 1D coordination polymer of composition [(Cu3Br3)(SEt2)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(μ2-Br)2Cu rhomboids, which are connected through two bridging SEt2 ligands to a tetranuclear open-cubane Cu4Br4 SBU, ligated on two external Cu atoms with one terminal SEt2. The solid-state luminescence spectra of 1 and 2 exhibit intense halide-to-metal charge-transfer 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.