Luminescent cyanometallate networks: the influence of weak interactions on structure and function

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This proposal is to exploit the utility of cyanometallate complex anions as components for coordination networks in two ways, each of which takes advantage of a different aspect of the bonding properties of cyanometallates. Firstly, combination of luminescent cyanometallate anions with other metal cations will afford a range of networks based on M-CN-M' bridges. Alternatively, use of hydrogen-bonding cations will result in formation of coordination networks based on hydrogen bonds between cations and anions, rather than dative coordinate bonds. These networks will be of interest for a variety of reasons: (i) polynuclear cyanometallates with up to 24 cyanide groups will provide networks with unprecedentedly high connectivity at a single node; (ii) use of optically resolved components will lead to chiral frameworks which must lead to second-order non-linear optical activity; (iii) they will display unusual luminescence properties such as photoinduced energy-transfer between components, leading to sensitised near-infrared luminescence from lanthanides. Secondly, the ability of cyanometallates to form halogen bonding interactions M-CN...X-C will be investigated in detail. Interaction strengths will be examined through the effect of the halogen bonds on the luminescence of [Ru(bipy)CN)4]2-.The utility of this cyanide...halogen interaction as a crystal engineering synthon will be evaluated for the first time by employing halogen bond donors based upon simple halopyridinium cations and cationic halopyridine complexes as well as neutral halogen bond donors based upon assembly of electron-poor perfluoroiodophenyl groups. Combination of these building blocks with cyanometallate anions will provide a range of materials which are novel from both a structural and a luminescence viewpoint, and we will examine how well the (non-covalent) M-CN...X-C halogen bonds can mediate interactions such as photoinduced energy-transfer and magnetic exchange.