meta-Phenylene-bridged double Schiff base copper(II) complexes as building blocks for 1D coordination polymers: Synthesis, crystal structure and magnetic properties

The new double Schiff-base ligands H6ipa-hyhb and H6ipa-hyhh were synthesized by condensation of a 4,6-diformylresorcinol derivative (ipa) with 4-hydroxy-butanoic acid hydrazide (hyhb) and 6-hydroxy-hexanoic acid hydrazide (hyhh). The reaction with copper(II) perchlorate in the presence of an appropriate co-ligand (Him = imidazole, Hpz = pyrazole) leads to the novel coordination polymers {[Cu2(H4ipa-hyhb)(Hpz)2](ClO4)2}n (1), {[Cu2(H4ipa-hyhb)(Him)2](ClO4)2}n (2), and {[Cu2-(H4ipa-hyhh)(Hpz)2](ClO4)2}n (3). These coordination polymers are composed of primary building blocks with the general formula [Cu2(H4ipa-X)(L)2]2+ (X = hyhb, hyhh; L = Him, Hpz) which are linked by coordination of the hydroxyl groups of the ligand side chains at the apical position of copper(II) centers of adjacent building blocks. The resulting chains possess different topologies and therefore different supramolecular structures due to the variation in length of the ligand alkyl side chains. For the complexes 1 and 2 double hydroxyalkyl-bridged distorted ladder like chains are formed. Whereas in case of complex 3 single hydroxyalkyl-bridged chains are obtained which assemble to hydrogen bonded double chains. In the case of 1 and 2 these chains are cross-linked by hydrogen bonding interactions with the perchlorate counterions, whereas for 3 additional π–π stacking interaction are observed. The temperature-dependent magnetic measurements indicate weak antiferromagnetic interactions with coupling constants J = −26.1 cm−1 (1), J = −28.2 cm−1 (2), and J = −26.5 cm−1 (3). The magnetic exchange interaction is solely the result of a coupling within the dinuclear complex moieties through the central resorcinol moiety.

Graphical abstractThe X-ray structural characterization as well as the magnetic properties of three novel Cu(II) 1D coordination polymers derived from dinuclear resorcinol-bridged schiff base complexes linked over the hydroxyalkyl ligand side chains are reported. The resulting cationic coordination chains are further linked by hydrogen bonding with the perchlorate counterions forming 3D or 2D supramolecular networks.Figure optionsDownload full-size imageDownload as PowerPoint slide