Homoconjugation and Tautomeric Isomerism in Triptycene-Fused Pyridylbenzimidazoles

Abstract

The facile, metal-free synthesis and characterization of three new series of triptycene-fused pyridylbenzimidazoles are reported; such compounds possess an imidazole moiety fused within the benzene rings of the trypticene and a pyridine ring installed at position 2 of the imidazole rings. The position of the nitrogen atom of the pyridyl moiety linked to position 2 of the fused benzimidazole scaffold is systematically changed from the ortho to para position. The number of substituted blades bearing the pyridyl-substituted fused benzimidazole scaffolds has been increased from one to three. Such a library of compounds allowed us to evaluate the enhancement of two main effects: tautomeric isomerism and homoconjugation. The characteristic dynamic equilibrium between different isomers induced by prototropic tautomerization was examined by 1H nuclear magnetic resonance spectroscopy. By comparison of the photophysical properties of the new compounds with those of classical planar pyridylbenzimidazoles, the presence of the homoconjugation effect between the different triptycene blades was demonstrated. Fine details of the electronic structure of the new derivatives were unraveled by a computational analysis. The novel compounds can be employed for the construction of intriguing self-assembled supramolecular architectures.

Triptycene-based diiron(ii) mesocates: spin-crossover in solution

“…To the best of our knowledge, the system described in this manuscript represents the inaugural instance of a triptycene-based supramolecular assembly incorporating Fe( ii ) and exhibiting spin-crossover in solution. These results not only can contribute to the fundamental understanding of supramolecular chemistry (aromatic ligands with a rigid framework typically favor the formation of helicate complexes), 12,13 but also hold promise for the utilization of triptycene derivatives in various technological applications, 1,2,8 ranging from molecular switches and sensors to advanced materials for electronics, optoelectronics, and beyond. 15–23…”

“…Triptycenes (Tp) possess a propeller-like rigid structure, with three benzene rings (the propeller blades) connected by two bridgehead sp 3 carbon atoms, defining dihedral angles of 120°. 1 This class of compounds has been garnering increasing interest among supramolecular chemists and material scientists 1–3 for their applications in solution, including molecular machines, 3 catalysis, 4 host–guest chemistry, 5,6 homochiral self-sorting and enantioseparation, 7 and optoelectronics. 8 Despite these wide applications, only very few examples of supramolecular assemblies containing Tp are known.…”