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

M. Pourayoubi^a,b and A.R. Mahjoub^b,*

^aDepartment of Chemistry, Ferdowsi University of Mashhad, Mashhad, 91779, Iran
^bDepartment of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran

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 C_i symmetries) were assembled to the programmed supramolecular architecture. Cooperation of the positive-charge, resonance effect and the O=C…O_terminal 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.

Keywords: Strong hydrogen bond, Crystal structure, Organic/inorganic hybrid, Polyoxometalate