Chromophores calculations

Table 1. Dipole moments, charge transfers, and molecular hyperpolarizabiUties for azobenzene chromophores, calculated using CNDO/S method ...

Figure 8 The interaction energy of (a) long-axis and (b) short-axis transition dipoles in a two-dimensional arrangement of carbazolyl chromophores calculated by Kuhn s extended dipole model[47] for the longer wavelength transitions at 291 and 342 nm.

If viewed from the oxygen, most optically active carbonyl compounds have their substituents only in the rear octants. The appearance of the plane that separates the rear octants from the front octants is not determined by the symmetry of the isolated chromophore. Calculations have shown that it has approximately the shape depicted in Figure 3.4b. Many examples have verified the validity of the octant rule, but there are also cases where it is not applicable, at least not in its original, simple form. This is true for ketones with a cyclopropane ring in the a, jS-position and for fluorosubstituted ketones, for which the experimentally observed sign can be reproduced only if the perturbation due to the fluorine atom is assumed to be smaller than that due to the hydrogen atom. More recent detailed calculations solved some of these problems. (Cf. Charney, 1979.)... 

Calculated considering excitation distribution over N individual chromophores. Calculated considering coherent coupling over four porphyrin units. 

Table 7.9 Electronic Absorption Bands for Representative Chromophores Table 7.10 Ultraviolet Cutoffs of Spectrograde Solvents Table 7.11 Absorption Wavelength of Dienes Table 7.12 Absorption Wavelength of Enones and Dienones Table 7.13 Solvent Correction for Ultraviolet-Visible Spectroscopy Table 7.14 Primary Bands of Substituted Benzene and Heteroaromatics Table 7.15 Wavelength Calculation of the Principal Band of Substituted Benzene Derivatives...

Tile basic chromophors of indigo and of some tetraazafulvalenes are very similar and therefore the frontier orbitals are comparable (90JPC949). PPP calculations on the 1,3,5,7-tetraazafulvalene 90 (R = Me) showed a good agreement with its UV/VIS spectrum. Tlie substitution of both methyl-sulfanyl groups in 90 by diethylamino/piperidino moieties led to a hypso-chromic shift of about 45 nm. 

It can be seen from Figures 3.7 and 3.8 that the calculations reproduce very well not only the experimental spectra but also the experimentally observed isotopic shifts indicating a high reliability of the computational method. According to this comparison, definite attribution can be made for even the difficult Raman bands that cannot be assigned based solely on the experimental results. It is, however, necessary to mention at this point that the calculated Raman spectrum provided directly by the ab initio computations correspond to the normal Raman spectrum with the band intensity determined by the polarizability of the correlating vibration. Since the intensity pattern exhibited by the experimentally recorded resonance Raman spectrum is due to the resonance enhancement effect of a particular chromophore, with no consideration of this effect, the calculated intensity pattern may, in many... 

In our first ONIOM study, we showed the advantages of combining two molecular orbital (MO) methods in calculations of the chromophore itself. Compared to a full CASSCF treatment of a scaled chromophore (PSBN in Figure 2-3), a two-layer ONIOM (CASSCF CIS) calculation where only parts of the conjugated system (PSBN8 in Figure 2-3) is included in the model system, reproduces the... 

A comparison of the thus calculated with the measured specific rotations of the 0th- to 4th-generation dendrimers of this kind gave a close resemblance, with a curve, approaching asymptotically a limiting value (Fig. 26). It was also shown that the shape of this curve was independent of solvent, concentration and temperature. This was not the case when CD spectra of these dendrimers were compared (Fig. 27) in solvents such as CH2C12 and f-butyl methyl ether a constant rise of the Cotton effect was observed, which correlates with the increasing amount of benzene chromophores in the dendrimers. However, in the... 

The chromophore atoms are assigned charges given by the density matrix in the Lowdin basis from the INDO/S calculation ... 

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