Bis(9-ethyl-3-carbazolyl)-spiro-(N,N)-tetrachloro and tetraamino cyclotriphosphazenes: design, synthesis, characterization and investigation of their free radical scavenging activity

In this thesis study, novel hybrid compounds were synthesized based on a trimeric phosphazene scaffold. Within the framework of the molecular hybridization strategy, carbazole-diamine derivatives with proven biological activity in the literature were combined with the biocompatible trimeric phosphazene structure to obtain new hybrid molecules. For this purpose, Schiff base derivatives (1 and 2) were first synthesized through the reactions of 9-ethyl-3-carbazolecarboxaldehyde with ethylenediamine and 1,3-diaminopropane, and subsequent reduction with NaBH4 afforded N/N-donor type carbazolyldiamines (3 and 4). Thereafter, the reactions of hexachlorocyclotriphosphazene (HCCP, trimer,N3P3Cl6) with the carbazole-diamines yielded monospirocyclotriphosphazenes (5 and 6). In the final step, bis(9-ethyl-3-carbazolyl)-(N,N)-spirotetrachlorocyclotriphosphazenes (5 and 6) were reacted with secondary amines (pyrrolidine, piperidine, morpholine, and 1,4-dioxa-8-azaspiro[4,5]decane) to obtain bis(9-ethyl-3-carbazolyl)-(N,N)-spirotetraaminocyclotriphosphazenes (5a-5d and 6a-6d). The structures of the monospirocyclotriphosphazenes were elucidated by elemental analysis, FT-IR, HRMS, and 1H, 13C and 31P NMR spectroscopy. The crystal structures of compounds 5 and 6 were determined by single-crystal X-ray diffraction. Moreover, the free radical scavenging activities of all synthesized compounds were investigated.