The changes of the non-illuminated HPD Soret band in solutions of various pH show that, in a slightly acidic medium, the PS is more aggregated than in neutral or alkaline solution (Fig.
Spectral measurements showed that HPD penetrates into micelles of these detergents; a typical red shift of the Soret band (from 369 to 402 nm) upon increasing the concentrations of TX-100, CTAB, and SDS was observed (Fig.
The Soret band energies of five porphyrins show significant correlations ([absolute val of r] = 0.
Kolling analyzed the Soret band energies of nickel protoporphyrin IX dimethyl ester in a set of 16 solvents with varying polarities and varying polarizabilities and concluded, by grouping solvents according to the Chastrette-Purcell generalized classification system, that the dependence of the Sore t band energies upon solvent polarizability effects is insignificant (Kolling 1989).
The absorption spectra of free-base porphyrins contain a strong Soret band in the blue region and four weaker Q bands in the visible region, while the absorption spectra of metalloporphyrins typically show only two Q bands (the [alpha] and [beta] bands) in addition to the strong Soret band.
Table 2 shows the correlation coefficients for the Soret band energies with respect to the solvent refractive index for the ethyl acetate -- chlorobenzene and ether -- anisole mixtures, and with respect to two functions of refractive index which have been related to polarizability (Renge 1993; Renge 1991).
Since band shifts caused by slight systematic solvent polarity changes are not ruled out in mixed-solvent systems, a causal relationship between the changes in the solvent polarizability and the observed Soret band shifts must be established.
In addition to the Soret band energies, the energies of several porphyrin Q bands also show correlations with respect to the refractive index of the ethyl acetate -- chlorobenzene and ether -- anisole mixtures (Table 3).
In the ethyl acetate - chlorobenzene and ether - anisole mixtures, the Soret band energies show linear trends with respect to the solvent mole fraction, with r values of 0.
The Soret band energies of three free-base porphyrins and two nickel porphyrin complexes show highly linear correlations with respect to the Lorentz-Lorenz function of the solvent refractive index in ethyl acetate -- chlorobenzene and ether -- anisole binary solvent mixtures.