Bis(benzimidazolium)methane salts: a potential guest for dibenzo-24-crown-8 towards [2]pseudorotaxanes

• Published in: Tetrahedron 2012-11, Vol.68 (47), p.9826-9835
• Main Authors: Ghosh, Sabari, Schmiedekamp, Ann Marie, Mukhopadhyay, Chhanda
• Format: Article
• Language: English
• Subjects: Bis(benzimidazolium)methane; Chemistry; Dibenzo-24-crown-8; Exact sciences and technology; Guest; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Host; Mass spectrometry; Methane; Molecular interactions; Molecular structure; Nuclear magnetic resonance; Organic chemistry; Preparations and properties; Pseudorotaxane; Tetrahedrons; Threaded; Two dimensional
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2012.08.080

We investigated the threading of bis(benzimidazolium) methane moieties with DB24C8 at 35 °C (room temperature) and found a high degree of association. The presence of threaded complexes was determined by 1H NMR and also supported by high resolution mass spectrometry and B3LYP/6-31G**++calculations. A 2D NMR study was done to elucidate the host–guest geometry and the molecular interactions present. The variable temperature NMR experiment was done over a temperature range of 243–323K. The threading was stable and visible even at 323K. Acid–base equilibrium established the reversibility of the process. DFT optimized structures establish that two H-bonded links are present between O1⋯O4′ and O3⋯O2′ across the dibenzo axis of the crown. [Display omitted] We investigated the threading of bis (benzimidazolium)methane moieties with DB24C8 at 35°C (room temperature) and found a high degree of association. Variable temperature NMR experiments (243–323K) proved the stability of the complex at 323K. The DFT optimized structures show two H-bonded links are present between O1⋯O4′ and O3⋯O2′.