Hydrogen bonded networks and a self-assembled 1D water cluster in nickel(II) and copper(II)-orotate complexes

Abstract

Three Ni(II) and Cu(II)-orotate complexes with 1,3-propanediamine (pen) and N-methylethylenediamine (nmen), [Ni(HOr)(H 2O) 2(pen)] ( 1), [Cu 2(μ-HOr) 2(pen) 2] (2) and {[Cu(μ-HOr)(nmen)]·3H 2O} n ( 3) (H 3Or = orotic acid) have been synthesized and characterized by thermal analysis, IR spectroscopy and single crystal X-ray diffraction techniques. In complex 1, the Ni(II) ion has a distorted octahedral geometry. The hydrogen bonds play an important role in the formation of the 3D polymeric structure of complex 1. The carboxylate groups interact with NH 2 groups of pen ligands, and HOr ligands are mutually hydrogen bonded to each other through the pyrimidine N and exocyclic O atoms, giving rise to R 2 2 ( 12 ) and R 2 2 ( 8 ) ring motives, respectively. Complex 2 consists of dimeric [Cu 2( μ-HOr) 2(pen) 2] units in which the Cu(II) ions have square pyramidal coordination geometries with bridging oxygen atoms at the pyramid apex. The HOr ligands, linked by N–H···O hydrogen bonds, constitute centrosymmetric R 2 2 ( 8 ) rings through the plane (1 0 1). The hydrogen bonds between pen and HOr ligands result in R 2 2 ( 8 ) rings centered at ( n + 1, 0, 1/2) ( n = zero or integer). Complex 3 is a 1D coordination polymer, in which the orotate moiety acts as a bridging ligand in the structure. The [Cu(HOr)(nmen)] units are linked by carboxylate oxygen atoms of HOr, which result in a zigzag chain structure along the a axis. Two adjacent 1D coordination polymers are connected through π···π interactions. The lattice water molecules, forming a 1D water cluster, function as a glue to form a 3D supramolecular network through extended hydrogen bonding.