Studies on fluorescent species of spiro-indolinonaphthooxazines and their fluorescence spectra

Photophysical behavior of spiro1,3,3-trimethylindolino-2,3′-naphtho2,1-b]-1,4-oxazine] (SP1) and spiro1,3,3,2′-tetramethylindolino-2,3′-naphtho2,1-b]-1,4-oxazine] (SP2) were studied. The fluorescent species and their spectra of SP1 and SP2 in polar solvents (acetonitrile and methanol) and non-polar solvent (cyclohexane) were investigated. The fluorescence decay in polar solvents was studied by picosecond time-correlated single photon counting. In most cases, fluorescence decay obeyed triexponential decay kinetics. The major fluorescent species is an excited intermediate which has similar conformation as its precursor (¹ SP ^*) formed after the bond cleavage between spirocarbon and oxygen in oxazine ring. The effects of molecular structure and solvent polarity on fluorescence spectra and fluorescence decay lifetime were studied.