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-sensi

Herein, the reactions of octachlorocyclotetraphosphazene (<b>OCCP, 1</b>) with sodium-3-ferrocenylmethyl-amino)-1-propanoxide (<b>L1</b>) gave hexachloro-ferrocenyl-(N/O)-spiro-<b>2</b> and 2-<i>cis</i>-4-dichloro-ferrocenyl-(N/O)-ansa-<b>3</b> cyclotetraphosphazenes in THF. Spiro- (<b>2</b>) reacted with excess 9-ethyl-<i>N</i>-methyl-3-carbazolyl-1,3-diaminopropane (<b>L2</b>) and 9-ethyl-<i>N</i>-ethyl-3-carbazolyl-1,2-diaminoethane (<b>L3</b>) to produce 2-<i>trans</i>-6-dispiro (<b><i>dispiro-</i>2a</b>) and 2-<i>trans</i>-4-<i>cis</i>-6-<i>trans</i>-8-tetraspiro (<b><i>tetraspiro</i>-2b</b>) cyclotetraphosphazenes, respectively. The reactions of ansa-<b>3</b> with excess <b>L2</b> led to the formation of monospiro {2-<i>cis</i>-4-dichloro-ansa-2-<i>trans</i>-6-spiro(N/N) (<b><i>ansa-spiro-</i>3b</b>)} and dispiro {2-<i>cis</i>-4-dichloro-ansa-6-<i>trans</i>-8-dispiro(N/N) (<b><i>ansa-dispiro-</i>3b</b>)} cyclotetraphosphazenes. However, the reactions of ansa-<b>3</b> with excess 9-methyl-<i>N</i>-ethyl-3-carbazolyl-1,2-diaminomethane (<b>L4</b>) afforded 2-<i>cis</i>-4-dichloro-ansa-6-<i>trans</i>-8-dispiro(N/N) (<b><i>ansa-dispiro-</i>3a</b>). Ansa-<b>3</b> was also reacted with excess sodium 3-(9-ethyl-carbazolamino)-1-propanoxide (<b>L5</b>) to give 2-<i>cis</i>-4-dichloro-ansa-2-<i>trans</i>-6-spiro(N/O) (<b><i>ansa-spiro-</i>3c</b>) and 2-<i>cis</i>-4-dichloro-ansa-6-<i>trans</i>-8-dispiro(N/O) (<b><i>ansa-dispiro-</i>3c</b>) 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. <b><i>Tetraspiro-</i>2b</b> 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 (<b>DSSC</b>) materials. Additionally, antimicrobial activities of five compounds (<b><i>dispiro-</i>2a, <i>ansa-spiro-</i>3b, <i>ansa-dispiro-</i>3b, <i>ansa-spiro-</i>3c</b> and <b><i>ansa-dispiro-</i>3c</b>) against various pathogenic bacteria and yeasts were evaluated. Their interactions with pBR322 plasmid DNA were also investigated.