Synthesis, characterization, and structural determination of copper(II) complexes with alkyl derivatives of hydroxybenzophenones

<p>Four mononuclear copper(II) complexes, [Cu(LFQM-115)₂] (<b>1</b>), [Cu(LFQM-116)₂] (<b>2</b>), [Cu(LFQM-117)₂] (<b>3</b>) and [Cu(octyloxy)₂] (<b>4</b>) [LFQM-115 = 2-hydroxy-4-<i>O</i>-methylbenzophenone (C₁₄H₁₁O₃), LFQM-116 = 2-hydroxy-4-<i>O</i>-butylbenzophenone (C₁₇H₁₈O₃), LFQM-117 = 2-hydroxy-4-<i>O</i>-(33-dimethylallyl)benzophenone (C₁₈H₁₈O₃) and octyloxy = 2-hydroxy-4-<i>O</i>-octylbenzophenone (C₂₁H₂₅O₃)], have been prepared and investigated by infrared spectroscopy, thermal analysis, and powder and single crystal X-ray diffraction. Even though the synthesis and infrared analysis of <b>1</b>, <b>2</b>, and <b>4</b> have been reported previously, their crystal structures were elucidated for the first time here. In addition, the crystal structures of LFQM-116 and LFQM-117 were also determined by single crystal X-ray diffraction. The pseudo-translational symmetry found in LFQM-116 and the isomorphism between LFQM-115 and LFQM-117 are discussed. The complexes were prepared from a reaction of copper(II) nitrate trihydrate and the respective ligand in a (1:2) molar ratio in methanol (for <b>1</b> and <b>2</b>) or THF (for <b>3</b> and <b>4</b>) with addition of NaOH. Furthermore, crystallographic studies show that each copper(II) exhibits a square planar geometry, coordinated by four oxygens of two ligands. The nature and crystal packing of the intermolecular interactions are discussed. Compounds <b>2</b> and <b>3</b> are isomorphic crystals and all structures have the same supramolecular synthon.</p