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 ( 1 and 2 ) with N -methyl-1,3-diaminopropane gave unsymmetrical cis -( 3 and 5 ) and trans -( 4 and 6 ) dispirocyclotriphosphazenes. Trans-cis-trans ( tct ) ( 7 and 11 ), cis-cis-cis ( ccc ) ( 8 and 12 ), trans-trans-cis ( ttc ) ( 9 and 13 ), and cis-trans-trans ( ctt ) ( 14 ) trispirocyclotriphosphazenes were obtained from the reactions of 3 and 5 and 4 and 6 with N -methyl-1,3-diaminopropane. cis -Dispirocyclotriphosphazenes ( 3 and 5 ) exist as "pseudomesoracemates", while trans -dispirocyclotriphosphazenes ( 4 and 6 ) are in "racemates". The existences of cis - 3 and trans - 4 as "pseudomesoracemate" and "racemate" were confirmed by 31 P NMR spectra recorded by the addition of "chiral solvating agent ( CSA )". X-ray crystallography proved that the absolute configurations of each enantiomer of cis-5 and trans-6 are SS' and RS'. Trispirocyclotriphosphazenes tct , ttc , ccc , and ctt exist as racemates, pseudomesoracemate, and meso forms. Furthermore, Hirshfeld surface analysis of the crystal structures of cis - 5 and trans - 6 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 cis - 5 . Additionally, trans - 6 exhibited the lowest minimal inhibitory concentration value (78.1 μM) against Candida tropicalis , and it was observed to cleave pBR322 plasmid DNA.