Very Strong Centrosymmetric [O...H...O]+ and Asymmetric [O-H& O]+ Hydrogen Bonds In a New POM-Based Hybrid Material

A specific assembly process, driven by coexisting X-H…O hydrogen bonding and X…O short intermolecular contacts (X = C, N, O) is described, in which the pseudo-Keggin polyoxoanion and two types of molecule...cation pairs (with C1 and Ci symmetries) were assembled to the programmed supramolecular architecture. Cooperation of the positive-charge, resonance effect and the O=C…Oterminal intermolecular contact led to the short and strong symmetrical [O…H…O]+ hydrogen bond (O…O = 2.449(13) Å) in one of the molecule…cation pairs [C4H9NO…H…ONC4H9]+ with the H-bonded proton in the center of inversion. The other [C4H9NOH…ONC4H9]+ molecule…cation pair (non-centrosymmetric) was formed through a very strong asymmetric [O.H.O]+ hydrogen bond of 2.431(13) Å in length which was created via the synergistic effect between the minor N-H…O secondary interaction, +CAHB (positive-charge-assisted hydrogen bond) and RAHB (resonance assisted hydrogen bond) mechanisms.