Ab initio molecular orbital calculations of the infrared spectra of hydrogen bonded complexes of water, ammonia, and hydroxylamine. Part 6. The infrared spectrum of the water–ammonia complex

1991 ◽  
Vol 69 (4) ◽  
pp. 632-637 ◽  
Author(s):  
Geoffrey Andrew Yeo ◽  
Thomas Anthony Ford
Keyword(s):  
Hydrogen Bond ◽  
Infrared Spectrum ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Hydrogen Bond Energy ◽  
Hydrogen Bond Interaction ◽  
Intensity Changes ◽  
Hydrogen Bonded

The molecular structure, interaction energy, and infrared spectrum of the linearly hydrogen bonded 1:1 molecular complex of water and ammonia have been predicted by means of a series of ab initio molecular orbital calculations, at the level of second order Møller–Plesset perturbation theory, using the 6-31G** basis set. The calculated wavenumbers and intensities have been compared with those calculated earlier for the respective monomers, and the wavenumber shifts and intensity changes rationalized in terms of the hydrogen bond interaction responsible for the stability of the complex.The calculated hydrogen bond energy of the complex has been compared with those of the linear water and ammonia dimers, reported in a previous publication, and the relative strengths of interaction of the three aggregates have been rationalized on the basis of the electron donor/acceptor capacities of the respective monomer units. Key words: ab initio, infrared spectrum, water, ammonia.

Hydrogen-Bond Acceptor Properties of Nitro-O Atoms: A Combined Crystallographic Database and Ab Initio Molecular Orbital Study

1997 ◽  
Vol 53 (6) ◽  
pp. 1017-1024 ◽  
Author(s):  
F. H. Allen ◽  
C. A. Baalham ◽  
J. P. M. Lommerse ◽  
P. R. Raithby ◽  
E. Sparr
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Lone Pair ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Hydrogen Bond Energy ◽  
Hydrogen Bond Acceptor ◽  
Model Dimer

Crystallographic data for 620 C—nitro-O...H—N,O hydrogen bonds, involving 560 unique H atoms, have been investigated to the van der Waals limit of 2.62 Å. The overall mean nitro-O...H bond length is 2.30 (1) Å, which is much longer (weaker) than comparable hydrogen bonds involving >C=O acceptors in ketones, carboxylic acids and amides. The donor hydrogen prefers to approach the nitro-O atoms in the C—NO2 plane and there is an approximate 3:2 preference for hydrogen approach between the two nitro-O atoms, rather than between the C and O substituents. However, hydrogen approach between the two O acceptors is usually strongly asymmetric, the H atom being more closely associated with one of the O atoms: only 60 H atoms have both O...H distances \leq 2.62 Å. The approach of hydrogen along putative O-atom lone-pair directions is clearly observed. Ab-initio-based molecular orbital calculations (6-31G** basis set level), using intermolecular perturbation theory (IMPT) applied to the nitromethane–methanol model dimer, agree with the experimental observations. IMPT calculations yield an attractive hydrogen-bond energy of ca −15 kJ mol−1, about half as strong as the >C=O...H bonds noted above.

Hydrogen-Bond-Like Nature of the CH/π Interaction as Evidenced by Crystallographic Database Analyses and Ab Initio Molecular Orbital Calculations

2001 ◽  
Vol 74 (12) ◽  
pp. 2421-2430 ◽  
Author(s):  
Osamu Takahashi ◽  
Yuji Kohno ◽  
Sachiyo Iwasaki ◽  
Ko Saito ◽  
Michio Iwaoka ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations

Structures of simple anions from ab initio molecular orbital calculations

1976 ◽  
Vol 29 (8) ◽  
pp. 1635 ◽  
Author(s):  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Basis Set ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Limited Information ◽  
Orbital Theory ◽  
Comparable Quality ◽  
Split Valence ◽  
Theoretical Results

Ab initio molecular orbital theory with the minimal STO-3G and split-valence 4-31G basis sets is used to obtain geometries of 18 anions:OH-, NH2-, HF2-, BH4-, BF4-, C22-, CN-, NCN2-, N3-, NO2-, NO3-, 0CCO2-, CO32-, HCOO-, CH3COO-, C2O42-, C4O42- and C(CN)3-. The theoretical results are compared with experimental results from the literature. The STO-3G basis set performs somewhat worse for anions than for neutral molecules. On the other hand, the 4-31G basis set gives good results and predicts bond lengths to within 0.02� for all the molecules considered. Limited information on bond angle predictions suggests that these are of comparable quality to those for neutral molecules. The tricyanomethanide ion is predicted to be planar.

Molecular Orbital Calculations of Cu-Halides

1981 ◽  
Vol 36 (10) ◽  
pp. 1095-1099 ◽  
Author(s):  
H. Itoh
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Energy Levels ◽  
Basis Set ◽  
Orbital Energy ◽  
Ionic Character ◽  
Molecular Orbital Calculations ◽  
Ab Initio Hf ◽  
Mo Theory

An ab initio HF MO theory is applied to CuX, CuX2 (X = F and Cl) and (CuCl)3 . Although the detailed sequence of energy levels depends upon the basis set used, high-lying orbital energy levels have largely halogen p-like character, whereas low-lying orbital energy levels have largely Cu 3 d-like character. This is in agreement with the chemical intuition of a highly ionic character of these compounds.

Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

2000 ◽  
Vol 55 (1-2) ◽  
pp. 315-322
Author(s):  
Nobuo Nakamura ◽  
Hirotsugo Masui ◽  
Takahiro Ueda
Keyword(s):  
Hydrogen Bond ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Quadrupole Interaction ◽  
Bond Distance ◽  
Nuclear Quadrupole Interaction ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Imidazole Derivatives ◽  
Nuclear Quadrupole

Ab initio Hartree-Fock molecular orbital calculations were applied to the crystalline imidazole and its derivatives in order to examine systematically the effect of possible N-H---N type hydrogen bond-ing on the nuclear quadrupole interaction parameters in these materials. The nitrogen quadrupole coupling constant (QCC) and the asymmetry parameter (η) of the electric field gradient (EFG) were found to depend strongly on the size of the molecular clusters, from single molecule, to dimer, trimer and to the infinite molecular chain, i.e., crystalline state, implying that the intermolecular N-H -N hydrogen bond affects significantly the electronic structure of imidazole molecule. A certain correla-tion between the QCC of 14N and the N-H bond distance R was also found and interpreted on the basis of the molecular orbital theory. However, we found that the value of the calculated EFG at the hy-drogen position of the N-H group, or the corresponding QCC value of 2 H, increases drastically as R-3 when R is shorter than about 0.1 nm, due probably to the inapplicability of the Gaussian basis sets to the very short chemical bond as revealed in the actual imidazole derivatives. We suggested that the ob-served N-H distances in imidazole derivatives should be re-examined.

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