MNDO geometry optimization

Both MNDO [340] and ab initio calculations [341] have been performed on the radical cation. The MNDO geometry optimization yields a flap angle of 132° and a Cj— C3 bond distance of 178.6 pm INDO calculations at this geometry give hfcs of 12.0, +18.3, and +78.0G. The ab initio calculations at the 6.31 G level yield a slightly smaller bond distance (174.3 pm) and Fermi contact terms of — 25.7, +14.7, and + 72.0 G. 

Smooth COSMO solvation model. We have recently extended our smooth COSMO solvation model with analytical gradients [71] to work with semiempirical QM and QM/MM methods within the CHARMM and MNDO programs [72, 73], The method is a considerably more stable implementation of the conventional COSMO method for geometry optimizations, transition state searches and potential energy surfaces [72], The method was applied to study dissociative phosphoryl transfer reactions [40], and native and thio-substituted transphosphorylation reactions [73] and compared with density-functional and hybrid QM/MM calculation results. The smooth COSMO method can be formulated as a linear-scaling Green s function approach [72] and was applied to ascertain the contribution of phosphate-phosphate repulsions in linear and bent-form DNA models based on the crystallographic structure of a full turn of DNA in a nucleosome core particle [74],... 

Modified intermediate neglect of differential overlap (MINDO/3) and modified neglect of differential overlap (MNDO) methods with full geometry optimization calculate triazol[4,5-, [l,2,3]triazole to possess antiaromatic structure with C h symmetry but not 1)2,5. In contrast, the aromatic structure with 1)2,5 symmetry is found advantageous for the 2,5-dioxide derivative <1991IZV1825>. 

Related research has been reported by Elder and Worley (39), in which MNDO was used to examine the structure of coniferyl alcohol, and its corresponding phenolate anion and free radical. This method represents an improvement over the PPP method, in that MNDO is an all-electron technique, and performs geometry optimizations. It was found that the calculated spin densities and charge values for the reactive sites did not correlate quantitatively with observed bond frequency, but it was observed that positions with partial negative charge and positive spin densities are the positions through which the polymerization has been found to occur. 

Boyd DB, Smith DW, Stewart JJP, Wimmer E. Numerical sensitivity of trajectories across conformational energy hypersurfaces from geometry optimized molecular orbital calculations AMI, MNDO, and MINDO/3. J Comput Chem 1988 9 387-398. 

Benzyl-2,4,6-triphenyl-27/-thiopyran 236 shows two absorption peaks in the UV which are only marginally influenced by the polarity of the solvent, typical of jt,7t transitions, and which are in general agreement with those calculated using INDO/1-C1 for geometry optimized at the MNDO level (Table 11a). 

D. B. Boyd, Drug Inf. J., 17,121 (1983). Quantum Mechanics in Drug Design Methods and Applications. D. B. Boyd, D. W. Smith, J. J. P. Stewart, and E, Wimmer, J. Comput. Chem., 9, 387 (1988). Numerical Sensitivity of Trajectories across Conformational Energy Hypersurfaces from Geometry Optimized Molecular Orbital Calculations AMI, MNDO and MNDO/3. D. B. Boyd, in Reviews in Computational Chemistry, Vol. 1, K. B. Lipkowitz and D. B. Boyd, Eds., VCH Publishers, New York, 1990, pp. 321-354. Aspects of Molecular Modeling. 

MNDO, AMI, and PM3 study (with full geometry optimization, in the gas and aqueous phases) of the protonation tautomerization and valence tautomerization equilibria of some pyrrole macromolecules is described in the work <2002JMT(589)43>. 

Indazoles can also show tautomeric forms. MP2-6-31G calculations on H- and 277-indazole annular tautomers showed that the 1/7-tautomer 86 is more stable the 2/7-tautomer 87 by 3.6kcalmoP <1996J(P2)57>. This result was further confirmed by the fact that the microwave rotational constants were reproduced with great accuracy. Also, electronic spectra recorded at 80 °C provided experimental evidence for the clear predominance of 177-indazole in the gas phase. The relative stabilities, PAs, and dipole moments for the tautomeric forms of some 3-substituted indazoles were calculated with full geometry optimization using AMI, PM3, and MNDO methods in the gas phase <2002JMT(583)137>. When the annular tautomerism is taken into account, the results of the semi-empirical AMI, PM3, and MNDO calculations confirmed that the 1/7-form 88 of the studied molecules is more stable than the 2/7-form 89 as stated in the previous literature. 

Donald B. Boyd (Eli Lilly and Company), David W. Smith, James J. P. Stewart (U.S. Air Force Academy), and Erich Wimmer (Cray Research) Importance of Criteria for Self-Consistent Field Convergence and Geometry Optimization in AMI, MNDO, and MINDO/3 Molecular Orbital Calculations. ... 

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