Anion directed supramolecular architecture of benzimidazole-based receptor

• Published in: Journal of molecular structure 2015-02, Vol.1081, p.128-135
• Main Authors: Singh, Udai P., Maurya, Radha Raman, Kashyap, Sujata
• Format: Article
• Language: English
• Subjects: Anions; Benzimidazole; Co-crystal; Colorimetry; Hydrogen bonds; Inorganic acids; Ligands; Molecular structure; Networks; Stacking; Supramolecules; Three dimensional; X-ray structure
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2014.10.008

LH44+·4ClO4−·4H2O, LH44+·4Br−·4(CH3)2SO, 2LH33+·3SiF62−·14H2O, LH44+·4H2PO4−·2H3PO4 and L·2CH3COOH were prepared by the reaction of N,N,N′,N′-tetrakis-(1H,benzimidazol-2ylmethyl)ethane-1,2-diamine (L) with different inorganic acids and organic acid structurally characterized. In each case the proton was transferred from inorganic acid to the nitrogen of benzimidazole ring. With the variation of anion, different structure was observed due to variation in number and type of interaction and orientation of cation and anion present in the asymmetric unit. [Display omitted] •Synthesis of five novel benzimidazole-based salts and co-crystal.•These salts/co-crystal show photoluminescence properties in presence of different mineral acids.•Crystal structures show different type of hydrogen-bonding. The reaction of N,N,N′,N′-tetrakis-(1H,benzimidazol-2ylmethyl)ethane-1,2-diamine (L) with different inorganic as well as organic acid afford salts viz., LH44+·4ClO4−·4H2O (1), LH44+·4Br−·4(CH3)2SO (2), 2LH33+·3SiF62−·14H2O (3), LH44+·4H2PO4−·2H3PO4 (4) and L·2CH3COOH (5) with different structures. The X-ray crystallographic studies revealed that these compounds are all ionic in nature due to proton transfer except 5 and are stabilized in the solid state by networks of hydrogen bonds between their respective components as well as solvent molecules. It also demonstrates that different types of hydrogen bond between protonated ligand and the anions are responsible for the extensive supramolecular frame work. The three dimensional packing is mainly guided by well-balanced primary N–H⋯O, O–H⋯N, O–H⋯O hydrogen bonds and secondary C–H⋯O interactions between benzimidazole and acids. Moreover, the hydrogen bonds, π⋯π and C−H⋯π stacking interactions appear to be effective in stabilizing the crystal structures. The colorimetric test showed color change upon the addition of acids in solution of the ligand. The photo-physical experiments suggest that the ligand shows fluorescence properties in the presence of acids.