RESUMO
A surprising 20-fold increase in chemiluminescence efficiency was observed for dialkyl luminol derivatives in comparison with the parent compound. This effect could be a direct consequence of steric gearing which facilitates the transition from the intermediate endoperoxide to the electronically excited phthalate. Mechanistic aspects of this process have been supported by computational calculations (CASPT2//CASSCF).
Assuntos
Luminol/química , Alcanos/química , Luminescência , Modelos Moleculares , Ácidos Ftálicos/química , Teoria QuânticaRESUMO
The chiral chemosensor 1, based on a thiourea-activated phthalimide, is available by four reaction steps from 4-nitrophthalimide. 1 detects fluoride, chloride, acetate, and dihydrogen phosphate anions by changes in UV-vis absorption. Fluoride in excess induces deprotonation whereas the other anions show only complex formation in the ground state. (1)H-NMR studies confirm the formation of these H-bonded complexes and the fluoride-induced receptor deprotonation in the recognition process. Moderate chiral recognition was observed for sodium D/L-lactate with K(ass)(D)/K(ass)(L) = 1.93.
Assuntos
Ânions/química , Ácidos Carboxílicos/química , Colorimetria/métodos , Nitrocompostos/química , Ftalimidas/química , Tioureia/análogos & derivados , Tioureia/química , Cinética , Espectroscopia de Ressonância Magnética , Ftalimidas/síntese química , Lactato de Sódio/química , Espectrofotometria Ultravioleta , Estereoisomerismo , Tioureia/síntese químicaRESUMO
The photophysical properties of a series of structurally related 4-aminophthalimides and the corresponding 5-aminophthalic hydrazides (luminols) are reported. Absorption, steady-state, and time-resolved fluorescence spectra of luminols exhibited substitution, solvent, and pH dependence. Singlet lifetimes have been determined by time-resolved laser flash spectroscopy. UV spectra in gas phase and DMSO solution were calculated by TD-DFT which revealed the existence of two low-energy excited singlet states with strong pH-sensitivity.
RESUMO
The fluorescence of caged phthalimide-serine couples 2 and 4 is up/down modulated by decarboxylative photorelease with fluorescence decrease (2) vs. moderate fluorescence increase (4) serving as reporter function.