Synthesis and structural characterization of 1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine and its Cu(II) complex

The hydrogen-bonding potential and complexation behavior with copper(II) of a multidentate Schiff-base ligand, 1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (H2L) was studied. Crystallization of H2L from an aqueous methanol solution resulted in the formation of an adduct H2L·H2O, which features a two-dimensional (2D) supramolecular hydrogen-bonded network, as evidenced by X-ray structural analysis. The reaction of H2L with copper(II) salt in a CH2Cl2MeOH solution formed a dinuclear double-stranded helicate, Cu2(L)2 (1) in high yield, which was characterized by microanalysis, IR spectra, and single-crystal X-ray crystallographic analysis. UV–vis titration experiments confirmed the spontaneous formation of a 1:1 metal–ligand complex in solution.

► The reactions of a multidentate H2L with water or copper salts were investigated.
► A 2D organic hydrogen-bonded network was observed in the crystals of adduct H2L·H2O.
► The reaction of H2L with CuII produced a dinuclear helicate.
► The structure was confirmed by both X-ray analysis and UV–vis titration in solution.