Quantum yields of oxazines and phenoxazines and the investigation of their spectral luminescence properties in binary mixtures

Phenol, the simplest aromatic monohydroxy alcohol, displays a faint Debye-like process when mixed with a nonassociating liquid

“…Now, based on this result, the determination of g K rests on assumptions regarding m PhOH and vice versa. For instance, taking m PhOH = 1.5 or 2.5 D, the minimum or maximum values, respectively, reported for phenol in various solutions, [119][120][121] one arrives at 0.66 r g K r 0.81 or at 0.66 r g K r 0.70. Tentatively assuming a chainlike association, characterized by, e.g., g K = 2, which would however be at variance with the findings for neat PC 54 even at high temperatures, 126 one would have m PhOH E 1.7 D and (also at variance with the experimental value) m PC E 2.8 D. These considerations show that in the present mixtures a chain-like arrangement of the PhOH molecules can be ruled out.…”

“…Interestingly, the dipole moment for geometry-optimized PhOH trimers was found to be even larger (3.75 D). 30 In view of the large uncertainty regarding the magnitude of m PhOH in liquid mixtures that contain PhOH, [119][120][121] in the following analysis we can only expect to extract the product of g K and m 2 in a reliable way. This quantity can be estimated from 69…”

“…54 For PC the magnitude of the electrical dipole moment (m PC E 5 D) is generally agreed upon. 64 However, the dipole moments reported for PhOH in the gas phase, 37,38,116,117 in the lowviscosity liquid state, 118 in aqueous 119,120 and other solutions, 121 as well as for the crystal at ambient 28 and high pressures 29 range from 1.2 D in the gas phase, to about 1.5. . .2.5 D in solution, and 3.5 D in the ambient pressure crystal.…”