Synthesis, crystal structure, and fluorescence of an unexpected dialkoxo-bridged dinuclear copper(II) complex with bis(salen)-type tetraoxime

An unexpected dinuclear Cu(II) complex, [Cu-2(L-2)(2)] (H2L2 = 3-methoxysalicylaldehyde O-(2-hydroxyethyl) oxime), has been synthesized via complexation of Cu(II) acetate monohydrate with H4L1. Catalysis by Cu(II) results in unexpected cleavage of two N-O bonds in H4L1, giving a dialkoxo-bridged dinuclear Cu(II) complex possessing a Cu-O-Cu-O four-membered ring core instead of the usual bis(salen)-type tetraoxime Cu-3-N4O4 complex. Every complex links six other molecules into an infinite-layered supramolecular structure via 12 intermolecular C-H center dot center dot center dot O hydrogen bonds. Furthermore, Cu(II) complex exhibits purple emission with maximum emission wavelength lambda(max) = 417 nm when excited with 312 nm.