Semiempirical MO calculation

Breindl, A., Beck, B., Qark, T., Glen, R. C. Prediction of the n-octanol/water partition coefficient, log P, using a combination of semiempirical MO-calculations and a neural network. J. Mol. Model. 1997, 3, 142-155. 

Fragalia and co-workers have reported the details of the He(I) and He(II) excited photoelectron spectra of Cp2Ti(CO)2 and concluded that evidence exists for significant backbonding between the Ti 3d orbitals and empty carbonyl v orbitals. Further, there is no evidence of important overlap between Ti and Cp orbitals. A small electrostatic perturbation of the Cp ligands is caused by the titanium atom (85). Bohm has described an elaborate study of the low energy PE spectrum of Cp2Ti(CO)2 (1) by means of semiempirical MO calculations (86). 

Yoshida et al. have reported the preparation of trisila[l.l.l]meta-cyclophane (trisilacalix[3]arene, 44) and tetrasila[l.l.l.l]metacyclo-phane (tetrasilacalix[4]arene, 45) (40) (Scheme 11) and indicate conformational analyses by using semiempirical MO calculations. 

Irradiation of 1-phenylcycloalkenes (160) with cyano-aromatics electron-accepting sensitizers in MeCN and benzene containing 1 m methanol gave trans- 6 ) and di-isomers (162) of anti-Markovnikov adducts. The (161)7(162) isomer ratio was found to depend on the ring size of 1-phenylcycloalkene but not on the sensitizer used. The mechanism of the reactions was studied by semiempirical MO calculations. 

The existence of an intermediate species in the dioxygen transfer from 4a-hydroper-oxyflavin anion to phenolate and indole anions has previously been shown and ab initio and semiempirical MO calculations have been used to examine possible candidates for... 

Several semiempirical MO calculations on the electronic structures of (C5H5)2M and (C6H6)2Cr have been published ... 

Semiempirical MO calculations using the AMI Hamiltonian suggested that the 2-hydroxy-4-oxo form of compound 20 has a lower heat of formation than the 2-oxo-4-hydroxy tautomer by approximately 42 kJ/mol (89AJC2161). 

The photoelectron spectrum of (4) has four bands at 8.03, 9.0, 10.20 and 11.37eV. These were assigned on the basis of semiempirical MO calculations (75T1415). 

Whereas semiempirical MO calculations do not provide reliable estimates of cycloproparene geometries, they do give reliable heats of formation and strain energies (SE) in comparison with both ab initio methods and experiment. The strain energies of 1 and 11... 

The third reason for our premature rejection of 5 was, as has recently been correctly guessed by Karfunkel (1992), the underdeveloped status of computational chemistry in those days computers large enough to handle C<0 were not available to us. Even when we performed the first semiempirical MO calculations of C60 and C70 in 1986, the molecules were rather too large to be studied by routine calculation and we had to work half a year debugging the program until we finally succeeded in detailed vibrational analysis (Slanina et al. 1987a,b, 1989 Rudzinski 1987). 

Using 1H NMR, Yokoyama et al. observed the racemization of helicity of an E form fulgide in solution for the case of 21E. IX The AH value of racemization of 21E obtained experimentally was compared with those for the possible racemization pathways calculated by AMI semiempirical MO calculations, and the racemization process was deemed to occur by way of the highly strained transition state 21E-TS. 

One theoretical approach for the calculation of certain thermodynamic properties of molecules is the use of semiempirical (MO) calculations. As an example, the heat of... 

The photoelectron spectra of aziridine (1) <74PMH(6)l, 74PMH(6)53> and 2//-azirine (2) have been measured <83JA768i, 87CB1971). The lone-pair ionization potential was found to be 10.58 eV, while the C=N 7t-electron ionization potential was measured as 11.56 eV. These values compared favorably with those obtained from MNDO semiempirical MO calculations. 

Scheme 3 Enantioisomerization process of F-IE calculated by AM-1 semiempirical MO calculation method.

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