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

• A new Ga(III) supramolecular compound 2 was synthesized.
• Its solid-state structure was compared to the previously reported compound 1.
• Interaction energies were investigated by AIM analysis and DFT and NBO calculations.
• This comparison revealed that a further compaction has been achieved in the presence of the OH substituent.

A new Ga(III) supramolecular compound (4,4′-bipyH2)[Ga(hpydc)2]2·7H2O (2) (where H2hpydc = 4-hydroxy-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 (bipyH2)[Ga(pydc)2]·(H2pydc)·4H2O (1) (where H2pydc = 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.

This research article reports a new Ga(III) supramolecular compounds 2, and combines experimental and theoretical approaches to compare its interactions with those of the previously reported Ga(III) compound 1.Figure optionsDownload as PowerPoint slide