A flexible multidentate Schiff-base ligand having multifarious coordination modes in its copper(II) and cadmium(II) complexes

A mononuclear complex, [CuL2]·2(CH3OH) (1), and two one-dimensional (1D) coordination polymers, {[Cu3L4(CH3OH)2]·(NO3)2}n (2) and [Cd(LH)2(N3)2]n (3), having a flexible multidentate Schiff-base ligand, 2-(3-(1H-imidazol-1-yl)propyliminomethyl)phenol (LH), with multifarious coordination modes have been obtained in different solvents and pH values. Another 1D cadmium(II) coordination polymer, [Cd(apimH)2Br3]n (4) (apim = (3-aminopropyl)imidazole), is also included for comparison. A four-coordinate square-planar Cu(II) center is formed in 1 where L serves as a bidentate N,O-chelating ligand, while two five-coordinate dinuclear Cu(II) centers and one six-coordinate mononuclear Cu(II) center are alternately arranged via two tridentate ligands in 2. In contrast, six-coordinate Cd(II) centers are constructed in 3 and 4, in the absence of a base, and they are bridged by double μ2 azide anions in an end-to-end way in 3 and alternate mono and triple μ2 bromine anions in 4. Furthermore, FT-IR, 1H NMR, UV–Vis and fluorescence spectral comparisons between LH and its metal complexes have been studied.

Graphical abstractThe coordination chemistry of a flexible multidentate Schiff-base ligand has been explored. One mononuclear Cu(II) complex (1) and three Cu(II) and Cd(II) 1D coordination polymers (2–4) have been obtained under different experimental conditions, and LH exhibits multifarious coordination modes.Figure optionsDownload full-size imageDownload as PowerPoint slide