Medium Effect of Polymer Matrices on Spectral Properties of 4‐Aminophthalimide and 4‐Dimethylaminophthalimide

Absorption and fluorescence spectra of 4‐aminophthalimide (API) and 4‐dimethylaminophthalimide (DAPI) were taken in solution of chloroform, methanol and water and polymer matrices as polystyrene (PS), poly(methyl methacrylate), (PMMA), polyvinylchloride (PVC) and polyvinylalcohol (PVA). The absorption spectra were dependent on the medium slightly; the longest wavelength band being around 350 nm for API and 390 nm for DAPI. Contrary to it, fluorescence of both probes is strongly influenced by polarity of the medium. The fluorescence in polar methanol or water is strongly bathochromically shifted from around 410 nm in cyclohexane up to 550 nm for API and 570 nm for DAPI in water. The quantum yield of fluorescence in polar solvents is low and it exhibits a short lifetime (under 1 ns for both API and DAPI). In polar solvents, both probes exhibit a large Stoke's shift up to 8,000 cm⁻¹. In polymer matrices both probes exhibit intense fluorescence as compare to anthracene with a lifetime longer than 10 ns and with a Stokes shift around 4,000 cm⁻¹. The less polar polymer matrix is polystyrene. In contrast, no strong medium effect is observed in polar PVA as compared with polar solvents. The reasons for different behavior of molecular probes in polar solvents of low viscosity and in polymer matrices are discussed.

Keywords:

• fluorescence
• probes
• 4‐aminophthalimide
• 4‐dimethylaminophthalimide
• medium effect
• quenching
• N‐oxyls

5 Acknowledgement

Authors thank grant agency VEGA for financial support through the projects 2/6015/26.