Photoluminescent and cytotoxic properties of multinuclear complexes and multinuclear-based polymers with group 12 metals and a tripodal ligand

Four novel multinuclear complexes and multinuclear-based polymers with group 12 metal centers, namely, Zn3(tpbb)Cl6 (1), {[Cd6(tpbb)2Cl12]·2CHCl3·0.5H2O}n (2), Hg4(tpbb)Br8 (3), and Hg4(tpbb)I8 (4), have been synthesized with respect to a new flexible tripodal ligand, 1,3,5-tris((2-(pyridine-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)benzene (tpbb). Complex 1 is a trinuclear cluster, as determined by X-ray crystallography, while 2 features an unprecedented hexanuclear metallacycle-based 2D network with chloride ion bridges. The similar umbrella-like tetranuclear architectures of 3 and 4 with different Hg(II)-halide salts demonstrate that halides with the same tetrahedral coordination geometries of metal centers do not greatly affect the structure of the complexes. Photoluminescent studies indicate that complexes 1 and 2 reveal enhanced and red-shifted solid-state fluorescence at room temperature compared with the ligand, tpbb, while 3 and 4 show prominent phosphorescence behaviors at cryogenic temperatures with lifetimes in the microsecond range. In addition, when tested against a panel of several human carcinoma cell lines (SH-SY5Y, QBC939 and EC109) by standard MTT assay, complex 1 displayed potential cytotoxicity against SH-SY5Y and QBC939 cells and selectivity to different tumor cell lines.

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