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    Phosphorus-nitrogen compounds. Part 35. Syntheses, spectroscopic and electrochemical properties, and antituberculosis, antimicrobial and cytotoxic activities of mono-ferrocenyl-spirocyclotetraphosphazenes
    (Royal Soc Chemistry, 2016) Okumus, Aytug; Elmas, Gamze; Cemaloglu, Resit; Aydin, Betul; Binici, Arzu; Simsek, Hulya; Acik, Leyla
    The reactions of octachlorocyclotetraphosphazene, N4P4Cl8, with N-alkyl-N-mono-ferrocenyldiamines, FcCH(2)NH(CH2)(n)NHR1 [n = 2, Fc = ferrocene, R-1 = Me (1); n = 2, R-1 = Et (2) and n = 3, R-1 = Me (3)], led to the formation of monoferrocenyl-spirocyclotetraphosphazenes (4-6). When the reactions were carried out with excess pyrrolidine, morpholine and 1,4-dioxa-8-azaspiro[4,5] decane (DASD), the fully substituted products (4a-6c) were obtained in high yields. The structures of all the phosphazene derivatives were characterized by MS, FTIR, H-1, C-13 and P-31 NMR, HSQC and HMBC techniques. The crystal structures of 4a and 5a were determined by X-ray crystallography. The electrochemically reversible one-electron oxidation of Fc redox centers was observed for cyclotetraphosphazenes. The fully substituted phosphazenes (4a-6c) were evaluated for their antituberculosis activity against reference strain Mycobacterium tuberculosis H37Rv, and compounds 4a-6a and 5c were found to be active. The antibacterial activities of phosphazenes 4a-6c against G(+) and G(-) bacteria and their antifungal activities against yeast strains were carefully scrutinized. The results indicate that compounds 4a-6a, 6b, 4c and 5c are very effective against yeast strains. The anticandidal activities of 6a and 6b make them promising anticandidal agents. The interactions of these compounds with plasmid DNA and their cytotoxic activity against L929 fibroblast and DLD-1 colon cancer cell lines were also investigated.
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    Phosphorus-nitrogen compounds. Part 42. The comparative syntheses of 2-cis-4-ansa(N/O) and spiro(N/O) cyclotetraphosphazene derivatives: spectroscopic and crystallographic characterization, antituberculosis and cytotoxic activity studies
    (Royal Soc Chemistry, 2019) Binici, Arzu; Okumus, Aytug; Elmas, Gamze; Kilic, Zeynel; Ramazanoglu, Nagehan; Acik, Leyla; Simsek, Hulya
    The reaction of N4P4Cl8 (1) with one equimolar amount of the sodium salt of an N/O donor-type bidentate ligand (2) afforded two kinds of derivatives, namely, mono-ferrocenyl-2-cis-4-dichloro-ansa- (2,4-ansa; 3) and mono-ferrocenyl-spiro- (spiro; 4) hexachlorocyclotetraphosphazenes. The reaction yield (35%) of 4 was significantly larger than that of 3 (14%). The 2,4-ansa compound (3) was reacted with excess secondary amines to produce 2-cis-4-dichloro-ansa-cyclotetraphosphazenes (3a-3d). On the other hand, the spiro compound (4) gave fully substituted mono-ferrocenyl-spiro-cyclotetraphosphazenes (4a-4d) with excess monoamines as well. The tetrameric phosphazene derivatives were characterized by ESI-MS and/or HRMS, FTIR, HSQC, HMBC, H-1, C-13, and P-31 NMR spectroscopy and X-ray crystallography (for 4). It is observed that the 2,4-ansa and spiro-cyclotetraphosphazenes have different thermal stabilities. Additionally, the CVs of the new mono-ferrocenyl pendant-armed cyclotetraphosphazenes revealed electrochemically reversible one-electron oxidation of the Fe-redox centre. The 2,4-ansa phosphazenes (3 and 3a-3d) have two different stereogenic P centers indicating that they are expected to be in racemic mixtures (RR'/SS'). The chiralities of 3a and 3c were investigated by chiral HPLC. The manuscript also deals with the antimicrobial activities against G(+)/G(-) bacteria and fungi, the interactions with plasmid DNA, the in vitro cytotoxic activities against L929 fibroblast and MCF7 breast cells, and the antituberculosis activities against Mycobacterium tuberculosis H37Rv of the cyclotetraphosphazenes.
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    Phosphorus-nitrogen compounds. Part 65. Novel diansa-spiro-cyclotetraphosphazenes: synthesis, characterization, bioactivity and electrochemical properties, and dye-sensitized solar cell fabrication studies
    (Royal Soc Chemistry, 2022) Mutlu, Gurcu; Okumus, Aytug; Elmas, Gamze; Kilic, Zeynel; Guzel, Remziye; Sabah, Busra Nur; Acik, Leyla
    In this investigation, the substitution reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (tetramer, OCCP, 1), with sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (L1) was found to yield the compounds, 2,4-ansa-(2) and spiro-(2) cyclotetraphosphazene derivatives. The starting hexachloro-2-cis-4-dichloro-monoferrocenyl-ansa-(N/O)cyclotetraphosphazene (2) reacted separately with dipotassium salts of N2O2 donor-type aminopodands, (KOPhCH2NH)(2)R [R = (CH2)(n), n = 2 (L2) and n = 3 (L3)], to produce mono-ferrocenyl-2,4-ansa-6,8-ansa-spirocyclotetraphosphazenes (dias; 3 and 4). Both products were purified by column chromatography, and their structures were confirmed using ESIMS, FTIR, H-1, C-13, and P-31 NMR spectral data. Besides, the molecular and crystal structures of 4 were elucidated by single-crystal X-ray diffraction. Compound 4 has four-different chiral P-centers. However, the absolute configuration of stereogenic P-centres of an enantiomer was designated as SS'S '' R'''. Both new compounds were also used for the examination of optical and electrochemical properties, and survey of bioactivity. To this end, the minimum inhibitory, bactericidal, and fungicidal concentrations (MIC, MBC, and MFC) were determined with the microdilution technique. These MIC, MBC, and MFC values were found to vary between 2500 mu M and 312.5 mu M. DNA cleavage activities of 3 and 4 with pBR322 plasmid DNA were also studied using electrophoretic mobility on an agarose gel. BamHI and HindIII restriction enzyme digestions of compound-pBR322 plasmid DNA were conducted to supply more insight into changes in DNA conformation. Cyclotetraphosphazene 4 caused DNA cleavage activity even at the lowest concentration. In addition to that, compound 4 inhibited enzyme digestion, indicating that DNA binds to A/A nucleotides with DNA binding activity. Moreover, the cytotoxicities of 3 and 4 were investigated by MTT assay against MDA-MB-231 breast cancer cells and COS-1 mammalian fibroblast cells. On the other hand, the optical and electrochemical properties of dias 3 and 4 were studied using UV-vis absorption and cyclic voltammetry techniques. As a result, both compounds can be suggested as ferrocene-based charge transformable phosphazene structures that can be used as new generation and synergistic DSSC materials.