Two new cobalt(II) rhodamine 6G hydrazone complexes: structure, fluorescence and magnetism.

Two new CoII complexes, namely bis{N-[(6-bromopyridin-2-yl)methylidene]-2-[6-ethylamino-3-(ethyliminiumyl)-2,7-dimethyl-3H-xanthen-9-yl]benzene-1-carbohydrazonate}cobalt(II) bis(perchlorate)-dichloromethane-methanol (1/1/2), [Co(C32H30BrN5O2)2](ClO4)2·CH2Cl2·2CH3OH or [CoII(L)2](ClO4)2·CH2Cl2·2CH3OH, (1), and the bis(tetrafluoridoborate) salt, [Co(C32H30BrN5O2)2](BF4)2·CH2Cl2·2CH3OH or [CoII(L)2](BF4)2·CH2Cl2·2CH3OH, (2) (L is commonly 6-bromopyridine-2-carbaldehyde rhodamine 6G hydrazone), have been successfully constructed and characterized. The crystal structure analysis revealed that complexes (1) and (2) are mononuclear and have a CoIIN4O2 distorted octahedral structure. The large π-conjugated xanthene moiety of the L ligand causes strong intermolecular π-π stacking interactions, yielding a supramolecular one-dimensional chain. Complexes (1) and (2) display an obvious fluorescence emission near 560 nm in the solid state. Magnetic investigations show that both (1) and (2) are paramagnetic, dominated by the structural distortion and spin-orbit coupling of CoII.