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

Four mononuclear copper(II) complexes, [Cu(LFQM-115)2] (1), [Cu(LFQM-116)2] (2), [Cu(LFQM-117)2] (3) and [Cu(octyloxy)2] (4) [LFQM-115 = 2-hydroxy-4-O-methylbenzophenone (C14H11O3), LFQM-116 = 2-hydroxy-4-O-butylbenzophenone (C17H18O3), LFQM-117 = 2-hydroxy-4-O-(33-dimethylallyl)benzophenone (C18H18O3) and octyloxy = 2-hydroxy-4-O-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 1, 2, and 4 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 1 and 2) or THF (for 3 and 4) 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 2 and 3 are isomorphic crystals and all structures have the same supramolecular synthon.