Heterocycloimmonium salts generally react with 3-methoxy 5-nitro salicylaldéhyde to give spirochromenes or merocyanines. Only the latter compounds are obtained in the thiazolinic and the benzimidazolinic series. The linking of a paraffinic ring to the merocyanines allows their 13C nmr study. The comparison of their spectra with those of heterocycloimmonium salts stresses a hyperconjugative effect in the thiazolinic and the benzimidazolinic series. The benzoxazolinic series appears to be in an intermediate position: the thermodynamic stabilities of spirochromenes and merocyanines are quite similar. The limiting value of the chemical shift of the carbon atom involved in the spiroannellation of merocyanines, can be approximately determined.
Dual-functionalized mesoporous silica nanobeans capable of GSH-dependent turn-on fluorescence and stimuli-responsive drug release are prepared for tumor inhibition and imaging.