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SPECTROSCOPIC OBSERVATION OF SOLVENT INTERACTION WITH SELECTED RETINAL SCHIFF BASES *
Author(s) -
Blatz Paul E.,
Mohler JonathanH.,
Ahmed Wasi
Publication year - 1991
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1991.tb02014.x
Subject(s) - chemistry , iodide , solvent , bromide , solvent effects , hydrogen bond , dipole , nucleophile , tetrahydrofuran , acetonitrile , crystallography , photochemistry , inorganic chemistry , organic chemistry , molecule , catalysis
Iodide salts of several N ‐retinylidenedialkylamines were prepared and their UV‐VIS spectra recorded. Their γ max values increased as the number of hydrogen atoms on the carbons alpha to nitrogen increased. In separate experiments, iodide salts of N ‐retinylidene‐ n ‐butylammonium (1) and N ‐retinylidene‐ n ‐butylmethylammonium (2) were prepared, and their excitation energies (ΔE) were measured in selected solvents of varying dielectric constant Data from each compound gave a straight line which converged at ε= 0. On the other hand, when ΔE values of the iodide and bromide of 2 were plotted vs solvent e, parallel rather than convergent lines were obtained. When γ max values of 1 and 2 were measured in a greater number of solvents, the solvents fell into four main groups. The first group, regular solvents, are rigid, have fixed dipoles, neither donate nor accept H‐bonds, and the δE of 1 and 2 decreases linearly as solvent e increases. This line for 2 is taken as a standard against which other solvents are judged. A second class of solvents that are good H‐bond donors like CHCl 3 , whose dipole moment coincides with the CH bond axis, is located in an area below the standard line. A third group, nucleophilic solvents like tetrahydrofuran, whose dipole moment is coincident with a strongly nucleophilic oxygen atom are good H‐bond acceptors and are found above the standard line. Solvents with unpredictable spectroscopic behavior are classed as anomalous.