Dimeric metallacycles and coordination polymers: Zn(II), Cd(II) and Hg(II) complexes of two positional isomers of a flexible N,O-hybrid bispyrazole derived ligand

Abstract

Reaction of MCl2 (M = Zn(II), Cd(II) and Hg(II)) with two flexible N,O-hybrid arene-linked, bispyrazole derivative ligands (1,2-bis([4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-oxabutyl]benzene (L1) and 1,4-bis([4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-oxabutyl]benzene (L2)) in EtOH yields six new compounds. All compounds have been characterized by analytical and spectroscopic techniques. Their crystal structures have been elucidated by single-crystal X-ray diffraction. Compounds containing L1 are isostructural dimeric metallacycles of general formula [M(L1)Cl2]2 (M= Zn(II) (1), Cd(II) (2) and Hg(II) (3)), L1 bearing a NN’-bridged coordination mode. Those containing L2, are coordination polymers of general formula {[M(L2)Cl2]·1/2solvent}n (M = Zn(II), solvent = H2O (4); M = Cd(II) (5) or Hg(II) (6), solvent = EtOH), L2 showing two different coordination modes depending on the metal: NN’-bridged in 4 and NON’-chelated and bridged in 5 and 6. Their molecular and extended structures are discussed, with a special focus on the coordination modes and conformations of L1 and L2. Finally, their photoluminescence properties have been analyzed.