Transient spectra for 4‘-(N,N-dimethylamino)-3-hydroxy- (1a) and 4‘-(N,N-dimethylamino)-3-methoxyflavone (2a) in several solvents at room temperature are reported following excitation with pulses of approximately 100 fs fwhm. 1a exhibits emission from both the normal excited state and from the excited tautomer produced following excited-state intramolecular proton transfer (ESIPT). Rate constants for the ESIPT process are found to vary between 3.3 × 1011 and 3 × 1010 s-1 depending on the solvent. Polar solvents are found to play a significant role in stabilizing the normal excited state of both 1a and 2a.

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A dissolved oxygen sensor for marine application is reported which is based on a ratiometric approach to the fluorescence intensity quenching of the ruthenium dye [Ru(II)-tris(4, 7-diphenyl-1, 10-phenanthroline)] 2+ . Both the ruthenium complex and the coumarin derivative dye have been entrapped in a porous sol-gel film. The membrane shows good optical response on exposure to low levels of dissolved oxygen in seawater. The design and limitations of such an optode membrane are discussed.