Supramolecular assemblies of benzene-1,3,5-tricarboxylic acid and 3,5-substituted pyrazoles: formation and structural analysis

Abstract

Different supramolecular assemblies of benzene-1,3,5-tricarboxylic acid (H3BTC) with various substituted pyrazoles, viz., 3,5-dimethylpyrazole (Pz^Me2H), 3,5-diisopropylpyrazole (Pz^iPr2H), 3-tert-butyl-5-isopropylpyrazole (Pz^tBu,iPrH), 3-phenyl-5-methylpyrazole (Pz^Ph,MeH), 3-cumenyl-5-methylpyrazole (Pz^Cum,MeH), 3,5-diphenylpyrazole (Pz^Ph2H) and 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (BPzH2) have been prepared. The present study demonstrates that the formation of hydrogen bond between protonated pyrazoles and anions provides a sufficient driving force for the directed assembly of varied supramolecular frameworks where H3BTC nicely adjusts its cavity dimensions to accommodate the guest. Theoretical studies were performed to analyze the effect of different substituents on hydrogen-bond interaction energy of the resultant salts and co-crystals. Energies of the various synthons were also calculated to correlate their stability and occurrence with the change of substituent on the pyrazole ring.