The effect of ligand substituent on crystal packing: Structural and theoretical studies of two Ga(III) supramolecular compounds

Abstract

A new Ga(III) supramolecular compound (4,4´-bipyH 2)[Ga(hpydc) 2 ] 2 .7H 2 O (2) (where H 2 hpydc = 4hydroxy-pyridine-2,6-dicarboxylic acid and 4,4´-bipy = 4,4´-bipyridine) was synthesized using the proton transfer reaction. Compound 2 was structurally characterized using single crystal X-ray diffraction, and it was shown that its asymmetric unit consists of two independent anionic Ga(III) complexes, one fully protonated 4,4´-bipyridine and seven uncoordinated water molecules. In order to understand the effect of pyridine OH substituent on supramolecular interactions and crystal packing, compound 2 was compared with (bipyH 2)[Ga(pydc) 2 ].(H 2 pydc).4H 2 O (1) (where H 2 pydc = pyridine-2,6-dicarboxylic acid), that does not have an OH group on the pyridine ligand. The Density Functional Theory (DFT) and Natural Bond Orbital (NBO) calculations and also Atoms in Molecules (AIM) analysis were used to analyze the non-covalent interactions in both complexes. The calculation of non-covalent interactions' energy provides a useful means to investigate their effects in the crystal packing.