Phosphorus-nitrogen compounds. Part 77. The synthesis of novel ferrocenyl(N/O)spiro- and 2-<i>cis</i>-4-dichloro-ferrocenyl(N/O)ansa-cyclotetraphosphazenes with 9-ethyl-3-carbazolyl pendant arm(s): spectral, bioactivity, electrochemical and dye-sensitized solar cell fabrication studies

Herein, the reactions of octachlorocyclotetraphosphazene (OCCP, 1) with sodium-3-ferrocenylmethyl-amino)-1-propanoxide (L1) gave hexachloro-ferrocenyl-(N/O)-spiro-2 and 2-cis-4-dichloro-ferrocenyl-(N/O)-ansa-3 cyclotetraphosphazenes in THF. Spiro- (2) reacted with excess 9-ethyl-N-methyl-3-carbazolyl-1,3-diaminopropane (L2) and 9-ethyl-N-ethyl-3-carbazolyl-1,2-diaminoethane (L3) to produce 2-trans-6-dispiro (dispiro-2a) and 2-trans-4-cis-6-trans-8-tetraspiro (tetraspiro-2b) cyclotetraphosphazenes, respectively. The reactions of ansa-3 with excess L2 led to the formation of monospiro {2-cis-4-dichloro-ansa-2-trans-6-spiro(N/N) (ansa-spiro-3b)} and dispiro {2-cis-4-dichloro-ansa-6-trans-8-dispiro(N/N) (ansa-dispiro-3b)} cyclotetraphosphazenes. However, the reactions of ansa-3 with excess 9-methyl-N-ethyl-3-carbazolyl-1,2-diaminomethane (L4) afforded 2-cis-4-dichloro-ansa-6-trans-8-dispiro(N/N) (ansa-dispiro-3a). Ansa-3 was also reacted with excess sodium 3-(9-ethyl-carbazolamino)-1-propanoxide (L5) to give 2-cis-4-dichloro-ansa-2-trans-6-spiro(N/O) (ansa-spiro-3c) and 2-cis-4-dichloro-ansa-6-trans-8-dispiro(N/O) (ansa-dispiro-3c) cyclotetraphosphazenes. Reactions were carried out by classical and microwave-assisted methods. These novel multi-heterocyclic inorganic/organic hybrid cyclotetraphosphazenes can offer valuable insights into developing new materials. Tetraspiro-2b and all ansa compounds have more than one stereogenic P-atom. The optical and electrochemical properties of some cyclotetraphosphazenes were investigated using UV-vis absorption and cyclic voltammetry (CV) techniques. As a result, these phosphazenes can be suggested as ferrocene-based charge transformable structures. They can be used as new-generation and synergistic dye-sensitized solar cell (DSSC) materials. Additionally, antimicrobial activities of five compounds (dispiro-2a, ansa-spiro-3b, ansa-dispiro-3b, ansa-spiro-3c and ansa-dispiro-3c) against various pathogenic bacteria and yeasts were evaluated. Their interactions with pBR322 plasmid DNA were also investigated.