Photophysics and Photochemistry of Imipramine, Desimipramine, and Clomipramine in Several Solvents: A Fluorescence, 266 nm Laser Flash, and Theoretical Study
文摘
Imipramine (IPA) and its derivatives are used widely for the treatment of depression and other mental disorders.Although there are more than 20 FDA-approved antidepressant drugs, the search continues for better compoundswith fewer deleterious side effects and higher efficacy. Over the past decade, several classes of antipsychoticdrugs have been developed, which-in spite of their structural diversity-share an ability to modulateneurotransmission and to produce undesirable side effects. Phototoxicity is one of the most important sideeffects noted in treatment with tricyclic antidepressants (TCAs), but its mechanism has not yet been elucidated.To develop new knowledge regarding the relationship between the structure and the photophysics of theseTCAs, we measured the photophysical properties of IPA, desimipramine (DIPA), and clomipramine (CIPA)in different solvents. The electronic configurations for the ground and the first excited singlet states werecalculated using the AM1/RHF/CI and the AM1/RHF/HE semiempirical quantum theoretical methods,respectively. The ground-state properties are solvent-independent, while the emission maxima are red-shiftedwith increasing solvent polarity/polarizability. However, the fluorescence quantum yield is relatively low inall of the tested solvents (f < 0.02). The primary transient intermediates produced by 266 nm high-intensitylaser photolysis are the solvated electron and the corresponding radical cation, with a negligible contributionof triplet-triplet absorption. The properties determined for the primary transients generated with a 266 nmlaser flash are consistent with the photodamaging effects generated through a limited radical mechanism.