Hydrogen bond

About: Hydrogen bond is a research topic. Over the lifetime, 57701 publications have been published within this topic receiving 1306326 citations.

Design of Organic Structures in the Solid State: Molecular Tapes Based on the Network of Hydrogen Bonds Present in the Cyanuric Acid.cntdot.Melamine Complex

Abstract: This paper describes the single-crystal X-ray structures of I :l complexes between seven N,Nrbis(4-X- phenyl)melamines (X = H, F, Cl, Br, I, CH3, and CF3) and 5,5-diethylbarbituric acid. These complexes crystallize as infinite tapes having components joined by triads of hydrogen bonds; the tapes pack with their long axes parallel. The crystalline architecture of these complexes-parallel tapes-serves as a structurally constrained framework with which to study physical-organic relationships between the structures of the crystals and the molecules of which they are composed. The complex with X = Br exists in polymorphic forms. One of the polymorphs is isomorphous to the X = Cl complex; the other is related to the X = I complex.

Novel infrared spectra for intermolecular dihydrogen bonding of the phenol-borane-trimethylamine complex in electronically excited state.

Abstract: The intermolecular dihydrogen bonding in the electronically excited states of the dihydrogen-bonded phenol-BTMA complex in gas phase was theoretically investigated using the time-dependent density functional theory method for the first time. It was theoretically demonstrated that the S(1) state of the dihydrogen-bonded phenol-BTMA complex is a locally excited state, in which only the phenol moiety is electronically excited. The infrared spectra of the dihydrogen-bonded phenol-BTMA complex in ground state and the S(1) state were calculated at both the O-H and B-H stretching vibrational regions. A novel infrared spectrum of the dihydrogen-bonded phenol-BTMA complex in the electronically excited state was found. The stretching vibrational absorption bands of the dihydrogen-bonded O-H and B-H groups are very strong in the ground state, while they are disappeared in the S(1) state. At the same time, a new strong absorption band appears at the C[Double Bond]O stretching region. From the calculated bond lengths, it was found that both the O-H and B-H bonds in the dihydrogen bond O-H...H-B are significantly lengthened in the S(1) state of the dihydrogen-bonded phenol-BTMA complex. However, the C-O bond in the phenol moiety is markedly shortened in the excited state, and then has the characteristics of C[Double Bond]O group. Furthermore, it was demonstrated that the intermolecular dihydrogen bonds in the electronically excited state of the dihydrogen-bonded phenol-BTMA complex are strengthened, since calculated H...H distance is drastically shortened in the S(1) state.

Interaction of amino acids with gold and silver clusters.

Abstract: Binding of gold and silver clusters with amino acids (glycine and cysteine) was studied using density functional theory (DFT). Geometries of neutral, anionic, and cationic amino acids with Au3 and Ag3 clusters were optimized using the DFT-B3LYP approach. The mixed basis set used here was denoted by 6-31+G** ∪LANL2DZ. This work demonstrated that the interaction of amino acids with gold and silver clusters is governed by two major bonding factors: (a) the anchoring N−Au(Ag), O−Au(Ag), and S−Au(Ag) bonds and (b) the nonconventional N−H···Au(Ag) and O−H···Au(Ag) hydrogen bonds. Among the three forms of amino acids, anionic ones exhibited the most tendency to interact with the Au and Ag clusters. Natural bond orbital analysis was performed to calculate charge transfer, natural population analysis, and Wiberg bond indices of the complexes. Atoms-in-molecules theory was also applied to determine the nature of interactions. It was shown that these bonds are partially electrostatic and partially covalent.