An efficient and versatile synthesis of 2, 2'-(alkanediyl)-bis-1H-benzimidazoles employing aqueous fluoroboric acid as catalyst: density functional theory calculations and fluorescence studies

Abstract

2,2′-(Alkanediyl)-bis-1H-benzimidazoles (simple and mixed) with variable methylene spacers were synthesized in excellent yields with aqueous fluoroboric acid (45%) (0.1 ml) as catalyst under solvent-free conditions. Their optimized structures were obtained using DFT calculations where it was seen that the s-trans orientation of the two imidazole rings was preferred for all types of bis-benzimidazole systems. The X-ray crystal structure of one such bis-benzimidazole further corroborated this fact. Finally, photophysical studies were carried out to get insight into the fluorescence characteristics of the newly synthesized bis-1H-benzimidazoles.

Heat‐resistant polyimides with lowCTEand water absorption through hydrogen bonding interactions

“…21 The above facts provided the possibility for the formation of intramolecular hydrogen bonding of DPABZ-based PIs. 18,22 The net charges of N atom attached on aromatic diamine were also calculated. The net charges of the amine N atoms in BI ring were slightly higher than those of ones in benzene ring, 20,23 indicating the former had stronger electron-donating and nucleophilicity, which was consistent with chemical shifts of the proton hydrogen of the amine in 1 H NMR.…”

“…Compared with traditional PABZ (5-amino-2-[4-aminoben-zene]benzimidazole), 12,13,17 more BI moieties in diamine segments were hope to provide more proton donors and amines attached on BI were expected to strengthen electron donation-acceptance interaction. Due to special molecular structure, 18,19 DPABZ also had the possibility of forming intramolecular hydrogen bonding, which behaved the potential to improve the hydrophobicity of polymers. Two series of copolyimide films based on PABZ or DPABZ were prepared by copolycondensation with 4,4-diaminodiphenyl ether (ODA) and 4,4-biphthalic anhydride (BPDA).…”

Synthesis of 2-alkyl substituted benzimidazoles under microwave irradiation: Anti-proliferative effect of some representative compounds on human histiocytic lymphoma cell U937

“…In case a tautomeric mixture were present, there would have been two sets of signals in 1 H NMR for each tautomer. 19 The predominant tautomer should be the one with the aromatic methyl group meta to NH as established from previous DFT calculations from our laboratory. 19…”

“…19 The predominant tautomer should be the one with the aromatic methyl group meta to NH as established from previous DFT calculations from our laboratory. 19…”