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Steric group enforced aromatic cyclic trimer conformer in tripodal molecules†
Shankar Deval Sathiyashivan,Bhaskaran Shankar,Palanisamy Rajakannu,Pratap Vishnoi,Dhanraj T. Masram
RSC Advances Pub Date : 08/26/2015 00:00:00 , DOI:10.1039/C5RA05151G
Abstract

A family of tripodal molecules (1–6) with/without steric ethyl groups at the central benzene scaffold and with furan/thiophene/pyridyl group at the 2-position of the benzimidazolyl unit was synthesised. Compounds 1–6 were characterized by elemental analysis and NMR spectroscopy. Compounds 1, 3, and 5 were further characterized by single crystal X-ray diffraction analysis. The molecular structures of 1 and 4 were optimized using density functional theory (DFT) calculations. X-ray and 1H NMR studies reveal that the introduction of three ethyl groups into a central benzene scaffold of furan/thiophene/pyridyl substituted benzimidazolyl based tripodal molecules enhances the edge-to-face C–H⋯π interactions, thereby favouring the aromatic cyclic trimer motif, in solution and the solid state. The unsubstituted central benzene scaffold allows the furan/thiophene substituted benzimidazolyl units in the tripodal molecules to move freely thereby weakening the edge-to-face C–H⋯π interactions between the aromatic cyclic trimer motif. Molecular modelling calculations indicate that the energy minimized structures of the tripodal molecules adopt a symmetric cyclic aromatic motif conformation.

Graphical abstract: Steric group enforced aromatic cyclic trimer conformer in tripodal molecules
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