Implications of hydrogen/halogen-bond in the stabilization of confined water and anion-water clusters by a cationic receptor

• Benzimidazole based benzene capped planar tripodal receptor has been reported.
• Fluoride-water trimer [F2–(H2O)0.5]2−, chloride-water tetramer [Cl2–(H2O)2]2−.
• I2···I (homo type) and S···I− (hetero type) halogen bond has observed.
• Thermal stability of anion complexes of is reported.

Anion complexation of benzene capped flexible tripodal receptor and solid state stabilization of discrete hybrid anion-water or infinite water clusters by various supramolecular interactions are reported here. The crystal structure of the receptor in protonated states shows all the three arms projected in one direction. We structurally demonstrate discrete fluoride-water cluster [F2–H2O]2− and square shaped chloride-water cluster [Cl2–(H2O)2]2− inside the cationic channel of the receptor. Structural analysis also reveals that these clusters are stabilized inside the channel through active participation of N/C/Ow′H⋯Ow, N/C/Ow′H⋯X− (X− = F−, Cl− and I−) H-bonds and electrostatic interactions. Moreover, C–H⋯π and π⋯π types weak intermolecular interactions appear to play crucial role in supramolecular assembly of receptor. Additionally, on treatment with hydroiodic acid (HI) L resulted zwitterionic iodide complex. Crystal structure reveals the presence of S···I halogen bonded dimer, I2···I halogen bond, 1D infinite water chain and neutral iodine molecules. It is comprehensible that ligand basal structure (benzene capped and N-bridge head in two tripodal) play crucial roles in the formation of diverse halide-water cluster. All structures were well examined by different techniques such as NMR, IR, TGA, DSC, PXRD and XRD.

Various structural morphology of water/anion-water clusters generated by benzene capped protonated tripodal receptor and influence of ligand structure on the formation of anion-water cluster, and a glimpse on I⋯I or S⋯I− halogen/chalcogen bond in zwitterionic complex has been demonstrated here.Figure optionsDownload as PowerPoint slide