Five new CuI /[Au(CN)2 ]- -based coordination polymer materials-Cu(py)2 [Au(CN)2 ] (1), Cu(PPh3 )(MeCN)[Au(CN)2 ]⋅MeCN (2 a), Cu(PPh3 )(MeCN)[Au(CN)2 ] (2 b), Cu3 (THT)4 [Au(CN)2 ]3 (3 a) and Cu(THT)[Au(CN)2 ] (3 b)-were prepared and characterized in terms of their structural and photoluminescence properties, and thermal stability (py=pyridine, THT=tetrahydrothiophene). While 1 and 2 a/2 b adopted one-dimensional zig-zag chain structures with no Au⋅⋅⋅Au (aurophilic) bonding, 3 a and 3 b exhibited much more complex three-dimensional frameworks featuring numerous aurophilic interactions; bridging THT units formed either eight-membered Cu4 S4 rings (3 a) or helical (Cu/S)n chains (3 b). When these materials are excited using a broad-band UV source (365 nm), they each emit light of a distinct colour (except for 2 a): light green for 1, pale blue for 2 b, deep blue for 3 a, and violet for 3 b (λmax =506 nm (1), 464 nm (2 b), 457 nm (3 a) and 404 nm (3 b)). The emission band in 1, 2 b and 3 b was assigned to CuI /ligand/CN- -based MLCT transitions, while the emission band of 3 a appears to be influenced by the presence of the aurophilic interactions in the structure. Materials 1 and 3 a lose their bound pyridine and THT, respectively, at 110 and 95 °C, respectively, indicating their potential utility as sensory materials.
Keywords: copper; heterobimetallics; metal-organic frameworks; noncovalent interactions; structure elucidation.
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