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The interaction of BH2NH2 with HNZ (Z: O, S) in the gas phase: Theoretical study of the blue shift of N-H...H-B dihydrogen bonds and the red shift of N-H...O and N-H...S hydrogen bonds

The blue shift of the N5-H7 bond stretching frequencies is observed in the B9-H4.H7-N5 dihydrogen bonds for BH2NH2.HNO and BH2NH2.HNS,corresponding to contraction of the N5-H7 bonds (except for slight elongation of the N5-H7 bond found in the complex BH2NH2.HNS), increase of stretching frequencies and decrease of infrared intensities respectively. | Journal of Chemistry, Vol. 47 (6), P. 779 - 785, 2009 The Interaction of BH2NH2 with HNZ (Z: O, S) in the Gas Phase: Theoretical Study of the Blue Shift of N-H.H-B Dihydrogen Bonds and the Red Shift of N-H.O and N-H.S Hydrogen Bonds Received 13 September 2007 Nguyen Tien Trung1, Tran Thanh Hue2 1 Faculty of Chemistry, Quy Nhon University 2 Faculty of Chemistry, Hanoi National University of Education Abstract Theoretical calculations at the MP2/6-311++G(2d,2p) level were performed to study the origin of the B-H.H-N blue-shifting dihydrogen bonds in the complexes of BH2NH2.HNZ (Z = O, S). The stably optimized cyclic structures of the complexes are displayed in figure 1, with interaction energies as table 1. The blue shift of the N5-H7 bond stretching frequencies is observed in the B9-H4.H7-N5 dihydrogen bonds for BH2NH2.HNO and BH2NH2.HNS, corresponding to contraction of the N5-H7 bonds (except for slight elongation of the N5-H7 bond found in the complex BH2NH2.HNS), increase of stretching frequencies and decrease of infrared intensities respectively. I - Introduction Very recently, the 1990s, a new type of interaction named dihydrogen bond was detected for metal organic crystal structure [1, 2] which was coined to describe an interaction of the type X-H.H-E; where X is a typical hydrogen donor such as N or O; and E are transition metals such as Ir, Re or B. These bonds are of type “proton-hydride”, i.e. between + X − Hδ and Hδ − − E . The Cambridge Structural Databases (CSD) have shown that the main characteristics of X-H.H-E systems are: the d(H.H) distances are typically 1.7-2.2 Å, significantly less than the sum of van der Waals for two hydrogen atoms, 2.4 Å; interaction energies in the range of classical hydrogen bonds (12-28 kJ.mol-1) [3]. The importance of dihydrogen bond in chemical, physical, and bio- chemical processes was studied [4, 5]. The authors have pointed out that similar processes were observed for biological systems .