Supramolecular architectures of cadmium(ii)-orotate complexes containing water clusters

Abstract

Three novel cadmium(II) complexes containing orotate ligand have been synthesized under different pH and characterized by X-ray crystallography, IR spectroscopy and thermal analyses measurements. In the complexes, the orotate ligand exhibits three different coordination modes. In [Cd₂(μ-HOr)₂(H₂O)₄(NH₃)₂]·2H₂O (1), the orotate acts as a tridentate ligand, showing unprecedented coordination mode. The (NH₄)₂[Cd₃(μ-HOr)₂(HOr)₂(H₂O)₈]·4H₂O (2) is constructed from orotate acting as both bidentate and tridentate bridging ligands. The Cd1 and Cd2 ions have two different coordination environments with four HOr, eight aqua ligands. Furthermore, 2 exhibits the novel 2D metal–water cluster layers. The (Hcha)₄[Cd(HOr)₂(H₂O)(cha)][Cd(HOr)₂(H₂O)₂]·H₂O (3) (cha = cyclohexylamine, H₃Or = orotic acid) consists of discrete cis and trans anionic complexes. The cha molecules exhibit chemically different functions by coordinating to Cd(II) ion in one form and being protonated and acting as counter–ions in other form. In the complexes, the supramolecular networks are constructed by novel N–H⋯O strong hydrogen bonds to form DA : AD motif, CO⋯π and π⋯π interactions.