Research interests

Our research is mainly focused on the interaction of light with matter, including pure photochemistry and its applications. We have a special interest in several groups of compounds.

Pure photochemistry
Our first commitment is to an ongoing study of the photophysics and electronic structure of biologically important isoalloxazines, particularly flavins. Flavins refer to 10-substituted 7,8-dimethyl-2,3,4,10-tetrahydro-benzo[g]pteridine-2,4-diones (7,8-dimethyl substituted isoalloxazines). Lumiflavin is the parent molecule from which all other variants derive, such as vitamin B2 (riboflavin), flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD), all of which are ubiquitous biologically important molecules. The excited states of flavins play an important role in living organisms and are involved in a number of important photobiological and photochemical processes, such as phototropism, phototaxis, and photodynamic action.

Another group of compounds under scrutiny is alloxazines, the main photodecomposition products of flavins. We are interested in the photophysics of alloxazines and, in particular, in their use as efficient photosensitizers of singlet oxygen. Alloxazines and related compounds belong to an interesting group of species whose hydrogen-bonded complexes are capable of undergoing excited-state double proton-transfer (ESDPT) in the presence of, for example, acetic acid. Currently, we are investing a large effort into studying ESDPT reactions, both in solution and in crystal solids.

A third group of compounds of special interest are aromatic thioketones. In this case, we are interested in photophysical processes, with special attention to their application in monitoring environmental effects after immobilizing them on a solid support. Aromatic thioketones have been shown to be extraordinarily useful models for studying the photophysics of polyatomic molecules in homogeneous media because they make an exception to Kasha's rule. Their fluorescence originates from the second singlet excited state S2 rather than from the first singlet excited state S1 due to their large S2-S1 energy gap. Additionally, strong spin-orbit coupling in thioketones results in intense phosphorescence from the first triplet excited state T1. Thermally activated delayed fluorescence from S1 and delayed fluorescence from S2 by triplet-triplet annihilation can be observed in the appropriate circumstances. We are particularly interested in spectroscopy and photophysics of thioketones adsorbed onto solid supports, such as cyclodextrin, cellulose, p-tert-butylcalix[n]arenes, and polycrystals.

We have also devoted some effort to other compounds, such as sparteine, a naturally occurring member of the lupine alkaloid family. We are specifically interested in the spectral properties of copper, cobalt, nickel, and zinc chloride complexes with sparteine and its derivatives. The respective crystal solids were studied by elemental analysis and mass spectrometry, IR absorption spectroscopy, and UV-Vis and NIR diffuse-reflectance spectroscopy.

Other compounds have come to our attention from time to time.



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