Effect of anions on supramolecular architecture of benzimidazole-based ionic salts

The reaction of N , N , N ′, N ′-tetrakis-(1H,benzimidazol-2ylmethyl) propane-1,3-diamine (L) with different inorganic acids affords salts viz., LH 4 4+ ·4ClO 4 − ·H 2 O ( 1 ), LH 4 4+ ·4Cl − ·2H 2 O ( 2 ), LH 4 4+ ·2H 2 PO 4 − ·H 7 P 3 O 12 2− ·3H 3 PO 4 ( 3 ), LH 4 4+ ·4NO 3 − ( 4 ), and 2LH + ·2CF 3 COO − ·5H 2 O ( 5 ). The X-ray crystallographic studies revealed that the proton transfer occurred from acid to the ligand. It also demonstrated that different type of hydrogen bond between protonated ligand and anions is responsible for the supramolecular framework. The colorimetric test showed color change upon the addition of acids in the solution of the ligand. The photo-physical experiments suggested the fluorescence properties of ligand in the presence of acids.