Molecular Structure and Photoinduced Intramolecular Hydrogen Bonding in 2-Pyrrolylmethylidene Cycloalkanones.

The structures of pyrrolylmethylidene derivatives of 2,3-dihydro-1H-inden-1-one (3), 3,4-dihydro-naphthalen-1(2H)-one (4), and cycloalkanones (5-7) were studied for the first time in the solid state and solution by NMR, IR, and UV spectroscopies supported by DFT quantum mechanical calculations. It was shown that all studied compounds except cycloheptanone derivative 7 both in crystal and in solution exist in the form of dimers where single E or E,E configuration with respect to the exocyclic C═C bond is stabilized by intermolecular hydrogen bonds N-H···O═C. UV irradiation at a wavelength of 365 nm of MeCN or DMSO solutions of 3-6 results, depending on the exposition time and solvent, partial to complete isomerization to the Z or Z,E isomers (in the case of 6, also the Z,Z isomer).

Stilbene photochrome-fluorescence-spin molecules: covalent immobilization on silica plate and applications as redox and viscosity probes.

We report herein on the development of a new photochrome-fluorescence-spin method for the quantitative analysis of the redox status and viscosity of a medium. The method of the viscosity measurement is based on the use of double fluorescence-nitroxide molecules. In such hybrid compounds the nitroxide moiety quenches the fluorescence of the fluorophore (stilbene moiety).

Depth of immersion of fluorescent chromophores in biomembranes studied by quenching with nitroxide radical.

A novel method has been developed for measuring depth of immersion of a fluorescent chromophore in biological matrices, such as biomembranes. The method is based on dynamic quenching of chromophore fluorescence by a nitroxide probe freely diffused in solution. Theoretical considerations and experimental evidences relating to the method are discussed.