Pyrazole is one of the most versatile ligand components available to inorganic chemists.1, 2 This is due to the convenient positioning of two nitrogen donors adjacent to one another and the presence of a deprotonable or hydrogen bond donor NH group (N1) and an aromatic-like N (N2). Both N1 and N2 are capable of coordinating to metal centres thus facilitating the synthesis of pyrazolate-bridged dinuclear and/or polynuclear metal complexes.
Some of the spin crossover (SCO) active iron(II) complexes of pyrazole-containing ligands that only coordinate through N2 have been reported to interact with solvent and/or anions through the uncoordinated N1-H; interactions that have modified the SCO-properties, making these systems suitable for molecular recognition devices.3, 4
We report the synthesis and characterisation of a new class of ligand, H2L, formed from a 2:1 reaction of 2-formyl-3-phenyl-pyrazole and o-phenylenediamine. It contains a tetradentate binding pocket as well as two NH moieties capable of interacting with solvent molecules/anions or, on deprotonation, of bridging to another metal centre. This presentation will focus on the synthesis and characterisation of mononuclear complexes of H2L and their subsequent use as synthons for the preparation of homo- and hetero-metallic tetranuclear complexes.
1. Ward, M. D.; McCleverty, J. A.; Jeffery, J. C., Coord. Chem. Rev. 2001, 222, 251–272.
2. Halcrow, M. A., Dalton Trans. 2009, 2059–2073.
3. Bhattacharjee, A.; Ksenofontov, V.; Sugiyarto, K. H.; Goodwin, H. A.; Gutlich, P., Adv. Funct. Mater. 2003, 13, (11), 877-882.
4. Clemente-León, M.; Coronado, E.; Giménez-López, M. C.; Romero, F. M., Inorg. Chem. 2007, 46, 11266-11276.
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