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Flavin-related Compounds: 3-Ethyl-lumiflavin. Combined DFT, NMR, X-ray and EI Mass Spectral Study

Sikorska E., Hernando J., Bourdelande J. L., Khmelinskii I., Kubicki M., Komasa A., Prukała D., Sikorski M.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 11

2141-2152

EN

3-Ethyl-lumiflavin was characterized by a variety of methods. Laser flash photolysis measurements in methanol solutions yielded a triplet state living 9.5 ms and a radical species living 91mi s, with steady-state photolysis quantum yields below 10-5. Fluorescence life time of 4.5 ns and quantum yield of 0.16 was recorded in aqueous solu tions. Crystal structure determined by X-ray diffraction was quite similar to the geometry of an isolated molecule calculated using the DFT approach, with the observed differences attributable to a non linear hydrogen bond existing in the crystal solid. EI mass spectra revealed a fragmentation path specific to this compound and in existent in lumiflavin or other similar compounds, due to ejection of a C2H5-N=C=O molecule, containing the ethyl substituent of the parent molecule.

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Spectroscopy and Photophysics of 6,8-Dimethylalloxazine. Experimental and Theoretical Study

Sikorska E., Khmelinskii I., Bednarek A., Williams S., Worrall D., Herance J., Bourdelande J., Nowacka G., Koput J., Sikorski M.

Polish Journal of Chemistry

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2004

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Vol.78 /nr 11-12

2163-2173

EN

Photophysics of 6,8-dimethylalloxazine was studied experimentally in function of solvent properties and theoretically by using time-dependent density functional theory (TD-DFT) calculations. The absorption spectrum of 6,8-dimethylalloxazine in the near-UV region shows one broad maximum at approximately 350 nm (ca. 28600 cm-1), which is a superposition of the two lowest-energy bands, and a fluorescence emission band varying from about 462 nm (21600 cm-1) in dioxane and acetonitrile to 475 nm (21000 cm-1) in methanol solution. In aprotic solvents neither band shows a significant dependence on the solvent polarity. The fluorescence lifetime increases in protic relative to aprotic solvents, and increases with increasing solvent polarity, due to reduction of the non-radiative rate constant. TD-DFT calculations provide details of the electronic structure of the molecule in its excited states and allow the interpretation of the observed photophysics in terms of the proximity effect.

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Albery Model Applied to Fluorescence Decay of Alloxazines Adsorbed into Cellulose

Sikorska E., Khmelinskii I., Sikorski M.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 5

745-751

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Diffuse Reflectance Spectroscopy Applied to Solid-State 2-Methylsparteine Metal Complexes

Jasiewicz B., Sikorska E., Khmelinskii I., Sikorski M.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 1

117-122