Designing inorganic–organic hybrid molecules based on carbazole/indole-appended cyclotriphosphazenes and the investigation of their photophysical properties

Abstract

The preparation of new fluorescent cyclotriphosphazene compounds and examination of the effect of the substituent on the photophysical properties of the new compounds formed in terms of the number and variety of substituents are attempted in this work. Therefore, cyclotriphosphazene derivatives bearing carbazole and indole moieties (2–9) were synthesized via the nucleophilic substitution reactions of cyclotriphosphazene (1) with N-(2-hydroxyethyl)carbazole (I) and 1-(2-hydroxylethyl)-2-methyl-1H-indole (II) and those of tris nongeminal cyclotriphosphazene derivatives (3a,b and 5a,b) with I and II. The full characterization data of compounds 2–9 were obtained by utilizing mass spectrometry and spectroscopic techniques. The crystal structures of II and 3a were elucidated using the single crystal X-ray diffraction method. The photophysical aspects of the targeted compounds (7a, 8 and 9) were investigated by UV/Vis and fluorescence spectroscopies using different organic solvents, and the results for the targeted compounds were compared within themselves, together with their precursors (I and II). It was seen that compound 7a, which includes both an ethoxycarbazole and an ethoxymethylindole group, has improved photophysical properties when compared with the fully ethoxycarbazole (8) and fully ethoxymethylindole (9) substituted cyclotriphosphazene derivatives.