Solid-State67Zn NMR Spectroscopic Studies and ab Initio Molecular Orbital Calculations on a Synthetic Analogue of Carbonic Anhydrase

2003 ◽  
Vol 125 (13) ◽  
pp. 3768-3772 ◽  
Author(s):  
Andrew S. Lipton ◽  
Catherine Bergquist ◽  
Gerard Parkin ◽  
Paul D. Ellis
Keyword(s):  
Carbonic Anhydrase ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Spectroscopic Studies ◽  
Molecular Orbital Calculations ◽  
Synthetic Analogue

Photoelectron Spectroscopic Studies of Some Substituted Borotrans

1987 ◽  
Vol 40 (5) ◽  
pp. 803 ◽  
Author(s):  
JB Peel ◽  
RG Rothwell ◽  
DX Wang
Keyword(s):  
Thermal Decomposition ◽  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Spectroscopic Studies ◽  
Photoelectron Spectra ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Phase Measurements ◽  
Dative Bond

The HeI photoelectron spectra of a series of borotrans have been measured. Ab initio molecular orbital calculations using minimum basis sets were performed on the six molecules in this study, by using geometries based on the known structure of the parent borotran, a tricyclic system containing a relatively short B←N dative bond. Temperatures up to 312� were required for the gas-phase measurements and considerable thermal decomposition was observed in two cases. The lowest-energy photoelectron bands are assigned to combinations of oxygen orbitals of the BO3 unit, but the B←N bonding electrons cannot be accurately located in the spectra.

A pairwise additivity scheme for conformational energies of substituted ethanes

1975 ◽  
Vol 343 (1632) ◽  
pp. 1-10 ◽  
Keyword(s):  
Large Deviations ◽  
Ab Initio ◽  
Dihedral Angle ◽  
Molecular Orbital ◽  
Methyl Groups ◽  
Molecular Orbital Calculations ◽  
Linear Combinations ◽  
Strongly Interacting ◽  
Conformational Energies

Ab initio molecular orbital calculations are used to explore additivity in the conformational energies of poly-substituted ethanes in terms of conformational energies of ethane and appropriate mono- and 1,2-di-substituted derivatives. Such relations would allow complex calculations for poly-substituted ethanes to be replaced by much simpler ones on a small number of parent molecules. General expressions for the linear combinations are derived from the assumption that interactions between vicinal substituents are pairwise additive and depend only on the vicinal dihedral angle. The additivity scheme is tested for 15 ethanes, di-, tri- or tetrasubstituted by cyano and methyl groups and for a smaller number of fluoroethanes. Additivity applies to within 0.1- 0.3 k J mol -1 in the methylethanes and mostly to within about 0.7- 0.8 kJ mol -1 in cyanoethanes. Large deviations are found among the geminally substituted fluoroethanes. It is suggested that the additivity approximation is most successful in the absence of strongly interacting geminal groups. Predictions are made of conformational energies of ten hexa(cyano- and methyl-) substituted ethanes.

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

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