Toward development of water soluble dye derivatized nitrosyl compounds for photochemical delivery of NO.
This report describes the synthesis, spectroscopy, and photochemistry of a new fluorescein-derivatized iron sulfur nitrosyl compound, the Roussin's red salt ester bis-((mu-S,mu-S')-fluorescein-2-thioethyl-ester)-tetranitrosyldiiron (Fluor-RSE). Under continuous photolysis Fluor-RSE decomposes with moderate quantum yields (0.0036 +/- 0.0005 at lambda(irr) = 436 nm) with the corresponding release of most of the NO carried by the Fe2S2NO4 cluster. Large changes in the optical absorptivity occur upon photolysis of the Fluor-RSE, and these changes have been attributed to the different protic forms available to the fluorescein chromophore as it is separated from the cluster. Steady-state luminescence experiments have shown that the fluorescence of Fluor-RSE is about 85% quenched relative to the model compound ethyl fluorescein (Fluor-Et). Thus, it is clear that excitation of the fluorescein chromophore antennae is followed by energy transfer to the Fe/S/NO cluster at a rate at least comparable to fluorescence. However, the effect of the iron-sulfur core on the fluorescent lifetimes from fluorescein chromophore is much smaller. A single-exponential decay (tau = 3.3 ns) was seen for Fluor-RSE that is only modestly shorter than that for Fluor-Et (tau = 4.5 ns), and this is the effect of the smaller radiative rate constant (k(r)) for the former. These systems further demonstrate that attachment of a pendant dye chromophore as an antenna significantly improves the effective rate for photochemical NO generation from the Roussin's red salt esters at longer excitation wavelengths.
Wecksler
Stephen R
SR
Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106-9510, USA.
Hutchinson
Jordan
J
Ford
Peter C
PC
D005452:Fluoresceins / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D010777:Photochemistry; D010782:Photolysis; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry
D005452:Fluoresceins; D009589:Nitrogen Oxides; D014867:Water; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; D007501:Iron