Phosphorus-Nitrogen Compounds: Part 76. Design and Syntheses of Dispiro- and Trispiro(N/N)cyclotriphosphazenes: Conformational and Structural Analyses, Chirality, Electrochemical, Dye-Sensitized Solar Cells, and Bioactivity Studies.

The reactions of monospirocyclotriphosphazenes ( and ) with -methyl-1,3-diaminopropane gave unsymmetrical -( and ) and -( and ) dispirocyclotriphosphazenes. Trans-cis-trans () ( and ), cis-cis-cis () ( and ), trans-trans-cis () ( and ), and cis-trans-trans () () trispirocyclotriphosphazenes were obtained from the reactions of and and and with -methyl-1,3-diaminopropane. -Dispirocyclotriphosphazenes ( and ) exist as "pseudomesoracemates", while -dispirocyclotriphosphazenes ( and ) are in "racemates". The existences of - and - as "pseudomesoracemate" and "racemate" were confirmed by P NMR spectra recorded by the addition of "chiral solvating agent ()". X-ray crystallography proved that the absolute configurations of each enantiomer of and are SS' and RS'. Trispirocyclotriphosphazenes , , , and exist as racemates, pseudomesoracemate, and meso forms. Furthermore, Hirshfeld surface analysis of the crystal structures of - and - revealed that the most significant contribution to crystal packing comes from H···H (58.2 and 57.6%, respectively). An oxidation-reduction wave was detected in the reversible cyclic voltammograms of the phosphazenes. The highest power conversion efficiency in dye-sensitized solar cell studies was obtained with -. Additionally, - exhibited the lowest minimal inhibitory concentration value (78.1 μM) against , and it was observed to cleave pBR322 plasmid DNA.