PUB - Publikationen an der Universität Bielefeld

The rigid, p-conjugated dicarboxylic acid 1,4-bis-[2-(4-carboxyphenyl)ethynyl]-2,5-dihexylbenzene {HO2C[PEP(hexyl)(2)EP]CO2H} has been used to synthesise the new crystalline coordination polymers {Zn(O2C[PEP(hexyl)(2)EP]CO2)(DMF)(2)} (1) and {Zn(O2C[PEP(hexyl)(2)EP]CO2)(DEF)(2)} (2) in N, N-dimethylformamide (DMF) and N, N-diethylformamide (DEF), respectively, under mild conditions. Single-crystal X-ray crystallography revealed that 1 and 2 are isostructural and consist of uncharged zigzag coordination chains in which [Zn(formamide)(2)](2+) fragments are bridged by (O2C[PEP(hexyl)(2)EP] CO2)(2) ligands. The zigzag chains possess different intra-chain Zn center dot center dot center dot Zn center dot center dot center dot Zn angles due to the different volumes of the coordinating formamide molecules and subtle differences in the hydrophobic inter-chain interactions. Upon heating 1 and 2 to 200 degrees C, removal of the coordinating formamide molecules occurs, yielding the formamide-free compounds 1-DMF and 2-DEF of composition {Zn(O2C[PEP(hexyl)(2)EP] CO2)}. According to powder X-ray diffraction and FT-IR spectroscopy studies, these materials are not crystalline but still possess partial ordering of intact, yet modified coordination chains in a structural arrangement which appears to be related to the respective parent compounds. Compounds 1, 2, 1-DMF and 2-DEF exhibit blue photoluminescence. The emission maxima of 1-DMF and 2-DEF are red-shifted by ca. 25 nm with respect to lambda(max) of 1 and 2, respectively. (C) 2009 Elsevier B. V. All rights reserved.