Synthesis of Bis(2,2,3,3-tetrafluoro-1,4-butanedialkoxy)-2-trans-6-bis(4-fluorobenzyl)spirocyclotetraphosphazene: Structural Characterization, Biological Activity and DFT Studies

The Cl replacement reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (1), with two equimolar amounts of N-(4-fluorobenzyl)-N′-methylpropane-1,3-diamine led to the formation of 4,4,8,8-tetrachloro-2-trans-6-bis-N-(4-fluorobenzyl)-N′-methylpropane-1,3-diamino-cyclotetraphosphazene (2). The reaction of 2 with excess sodium 2,2,3,3-tetrafluoro-1,4-butanedioxide afforded the bis(2,2,3,3-tetrafluoro-1,4-butanedialkoxy)-2-trans-6-bis(4-fluorobenzyl)spirocyclotetraphosphazene (2a). The elemental analyses, mass spectrum (ESI–MS), FTIR, HSQC, HMBC, 1H, 13C and 31P NMR spectral data of 2a were consistent with the proposed structure. The crystal structure of 2a was elucidated by X-ray diffraction method. The spectroscopic data of the molecules (2 and 2a) in the ground state were investigated by the Density Functional Theory (DFT) from the crystal structures. On the other hand, compound 2a was found to be the most active against S. aureus G(+) (MIC value: 125 µM). Whilst, any antifungal activity of 2a was not observed against C. albicans and C. tropicalis. This compound also exhibits cytotoxic activity against L929 fibroblast and MCF-7 breast cancer cells. The interaction of 2a with pBR322 DNA was researched using gel electrophoresis. It is understood that the change in DNA conformation by interstrand of 2a with A/A and G/G nucleobases in DNA. The synthesis, spectroscopic and crystallographic characterizations, biological activities and DFT studies of bis(2,2,3,3-tetrafluoro-1,4-butanedialkoxy)-2-trans-6-bis(4-fluorobenzyl)spirocyclotetraphosphazene were presented.