Exploration of Salts and Cocrystals of 2,2′,6,6′-Tetracarboxybiphenyl with Acetic Acid, Monobasic and Dibasic N-Heterocycles, and N-Oxides

Abstract

Several complexes of 2,2′,6,6′-tetracarboxybiphenyl (H41) with various N-containing heterocycles and N-oxides were synthesized and their crystal structures were analyzed in terms of salt/cocrystal, deprotonation, synthons, and network geometries. The tetra carboxylic acid, H41, was found to act as a host for the inclusion of acetic acid dimers. For complexation reactions with bases, the mono basic compounds such as pyridine, quinoline, and acridine; the dibasic compounds such as 9,10-phenanthrolene, 4,4′-bipyridylethane, 4,4′-bipyridyldisulfide, phenazine, and 1,4-diazabicyclooctane (dabco); and N-oxides of 4,4′-bipyridine and dabco are considered. In the crystal structures of these complexes, the H41 was found to exist as H21 (double deprotonation of H41), H31 (mono deprotonation of H41), or H41 (cocrystals) forms depending on the basicity of the complexing agent and other factors. Out of 13 complexes studied here the more probable acid-pyridine synthon was observed in one complex, the COO–···HOOC– synth...