| Abstrakt: |
The prediction of the equilibrium molecular geometry, photostability, and electronic properties of new diarylide and pyrazolone pigments based on nonmutagenic analogs of benzidine is discussed. Several semi-empirical molecular orbital methods were assessed for prediction of geometry including MNDO, MINDO/3, AM1, and PM3. Prediction of the wavelength of maximum absorption was assessed using PPP, CNDO/1, CNDO/2, INDO/1, and INDO/2 Hamiltonians. Comparison of the predicted equilibrium geometry of pigments, as well as some benzidine-based intermediates, with single crystal x-ray crystallographic data, showed that PM3 generally provides more accurate prediction of crystal structures of pigment intermediates with primary amino substituents. However, an AMI protocol was more accurate in predicting crystal structures of pigments possessing intramolecular hydrogen bonds. Prediction of wavelength of maximum absorption showed consistently that a PPP (Pariser-Parr-Pople) MO method provides the highest correlation with experimental data. [ABSTRACT FROM AUTHOR] |
