Charge transfer bands, correlation with chemical shift

The preference of this conformation (the barrier hindering the rotation of the p-XCgH — at X = Cl, CHj, CFj amounts to 8.5 kcal/mol., cf. also ° 0 is assumed to be due, at least partially, to the donor-acceptor interaction between the K-system of the aryl residue and the carbenium centre at Cjg in the electronic absorption spectra of the 9-p-X-phenyl-9,10-dimethylphenanthrenium ions the charge transfer bands have been revealed whose position correlates well with the ionization potentials of respective X-substituted benzenes. Judging by the NMR- C spectra, however, the extent of this interaction in the main state of ions is insignificant — the chemical shift of the Cjo atom nearly remains unchanged as the X substituent... 

A rough correlation of 8 carbene carbon with the frequency of the metal to ligand charge transfer band was found. The energy of the band increased as the electron donating properties of R decreased, due to the increased stabilization of the carbene pz orbital with increasing electron delocalization (chemical shift of the carbene carbon will be electron density differences. 

Properties of the microenvironment of soluble and cross-linked polymers were studied by the shift of bands in the electron spectra of solvatochromic reporter molecules embedded in polymer chains. Generally, the charge-transfer (CT) absorption spectra and emission spectra of a number of compounds were used to correlate solute-solvent interactions with physical and chemical properties of interest. The energy of the band maxima of these chromophores is quite solvent sensitive and is linearly correlated with empirical solvent polarity parameters. The observed shift of the maximum of the solvatochromic reporter embedded in the polymer chains, compared with a low-molecular weight analog in the same solvent, was interpreted in terms of a change in the polarity of the microenvironment of the polymer in solution. 

---