Advances in the chemistry of chlorocyclophosphazenes

Molecular, 1D and 2D assemblies from hexakis(3-pyridyloxy)cyclophosphazene containing 20-membered metallamacrocyclic motifs

The coordination behaviour of hexakis(3-pyridyloxy)cyclophosphazene (L) towards divalent metal ions is described. The reaction of L with hydrated metal nitrates afforded [{N3P3(O-C5H4N-3)6}2{Zn(H2O)3(NO3)}2{Zn(H2O)2(NO3)}2]n[NO3]2n·4nH2O·nCH3OH (1), [{N3P3(O-C5H4N-3)6}2{Zn(H2O)3(NO3)}2{Cu(NO3)}2]n[NO3]2n·4nH2O·nCH3CN (2), [{N3P3(O-C5H4N-3)6}2{(NO3)Cd-(μ-(NO3)-Cd(NO3)2(μ-(NO3)Cd(NO3)}]n·2nCH3OH·3nH2O (3), and [{N3P3(O-C5H4N-3)6}2{Cd(H2O)3(NO3)}2][NO3]2·9H2O (4). 1 and 2 are one-dimensional coordination polymers while 3 is a two-dimensional coordination polymer. On the other hand 4 is a molecular metallamacrocycle. A common feature of 1-4 is the presence of a 20-membered dimetallamacrocyclic motif constructed through the involvement of a pair of cyclophosphazene ligands through their geminal pyridyloxy substituents. The P-N bond distances in L and its metal complexes 1-4 are nearly the same indicating the flexible nature of the coordination pyridyloxy arms present on the cyclophosphazene scaffold.

Phosphorus-nitrogen compounds: part 30. Syntheses and structural investigations, antimicrobial and cytotoxic activities and DNA interactions of vanillinato-substituted NN or NO spirocyclic monoferrocenyl cyclotriphosphazenes

The gradual Cl replacement reactions of NN (1-3) or NO spirocyclic monoferrocenyl cyclotriphosphazenes (4 and 5) with the potassium salt of 4-hydroxy-3-methoxybenzaldehyde (potassium vanillinate) resulted in the mono (1a-5a), geminal (gem-1b-5b), non-geminal (cis-5b and trans -1b-4b), tri (1c, 3c-5c) and tetra-vanillinato-substituted phosphazenes (1d-5d). All the phosphazene derivatives have stereogenic P-center(s), except tetra-substituted ones. The vanillinatophosphazenes have reversible voltammograms with one-electron anodic and cathodic peaks which are attributed to ferrocenyl redox probe. The structures of the new phosphazene compounds were determined by FTIR, MS, (1)H, (13)C{(1)H} and (31)P{(1)H} NMR spectral data. The solid-state structure of cis -5b was examined by single-crystal X-ray diffraction techniques. In addition, the compounds were tested in HeLa cancer cell lines using MTT assay. The 12 phosphazene derivatives were screened for antimicrobial activity, and 3c was very effective against S. aureus even at 4.88 µM concentration, taking into account the MIC values. Besides, interactions between the phosphazenes and pBR322 plasmid DNA were also investigated.

Reactions of alkyne- and butadiyne-derived fluorinated cyclophosphazenes with diiron and dimolybdenum carbonyls

The reaction of (β-phenylethynyl)pentafluorocyclotriphosphazene, [(PhC≡C)(F)PN](PNF2)2, with Fe2(CO)9 in refluxing hexane resulted in five new compounds, namely, [Fe(CO)2{η(2):η(2)-2,4-(P3N3F5)2Ph2C4Fe(CO)3}-μ-CO] (1), [Fe(CO)2{η(2):η(2)-2,5-(P3N3F5)2Ph2C4Fe(CO)3}-μ-CO] (2), [Fe(CO)2{η(5)-2,5-(P3N3F5)2Ph2C4CO}C(Ph)═C(P3N3F5)](3), [Fe(CO)3{η(2):η(2)-2,4-(P3N3F5)2Ph2C4CO] (4), and [Fe(CO)3{η(2):η(2)-2,5-(P3N3F5)2Ph2C4CO] (5). While compounds 1, 2, 4, and 5 have five-membered ferracyclopentadiene or cyclopentadienone rings coordinated to the Fe(CO)3 unit in the η(2):η(2) mode, compound 3 has a 2,5-cyclopentadienone ring attached to an Fe(CO)2(P3N3F5)C═C(Ph) unit, where Fe is η(5)-bonded to the cyclopentadienone ring, and the carbon that is α to the phenyl unit of the Fe(CO)2(P3N3F5)C═C(Ph) group is σ-bonded to the oxygen atom of the cyclopentadienone ring. Formation of five-membered cyclic compounds having two fluorophosphazene units on the vicinal carbon atoms of C4R2R'2Y rings was not observed in this reaction. No examples of Fe(CO)3-bound cyclobutadiene complexes were also isolated from this reaction. A similar reaction in the presence of trimethylamine N-oxide, NMe3O, was found to proceed at -20 °C with the formation of compounds 4 and 5 only. In contrast to the Fe2(CO)9 reaction, a reaction of alkyne-derived pentafluorocyclotriphosphazenes, [(RC≡C)(F)PN](PNF2)2 [R = Ph, Fe(C5H5)2] with the molybdenum complex Cp(CO)3Mo-Mo(CO)3Cp (Cp = cyclopentadienyl) in refluxing toluene resulted in the simple tetrahedral clusters Cp(CO)2Mo(P3N3F5)C-C(Ph)Mo(CO)2Cp (6) and Cp(CO)2Mo(P3N3F5)C-C(Fc)Mo(CO)2Cp (7) (Fc = ferrocenyl). A similar reaction of Cp(CO)3Mo-Mo(CO)3Cp with butadiyne-derived fluorophosphazenes, [(RC≡C-C≡C)(F)PN](PNF2)2 [R = Ph, Fe(C5H5)2], yielded the tetrahedral clusters Cp(CO)2Mo(P3N3F5)C-C(C≡CPh)Mo(CO)2Cp (8) and Cp(CO)2Mo(P3N3F5)C-C(C≡CFc)Mo(CO)2Cp (9) with the tetrahedral Mo2C2 unit forming exclusively with the alkyne unit of the butadiyne group bound to the cyclophosphazene ring. The crystal structures and infrared spectral data of these molybdenum clusters showed the presence of a semibridging carbonyl on one of the molybdenum units. All new compounds were characterized by IR, NMR [(1)H, (13)C{(1)H}, (31)P{(1)H}, and (19)F{(1)H}] and high-resolution mass spectrometry studies. Compounds 2, 3, 5, and 7-9 were also structurally characterized using single-crystal X-ray diffraction studies.

Cyclophosphazene–organostannoxane hybrid motifs in polymeric and molecular systems

The synthesis and structural characterization of two hybrid inorganic ring systems that contain interconnected cyclophosphazene–stannoxane motifs are reported.

Phosphorus-nitrogen compounds. Part 24. Syntheses, crystal structures, spectroscopic and stereogenic properties, biological activities, and DNA interactions of novel spiro-ansa-spiro- and ansa-spiro-ansa-cyclotetraphosphazenes

The reactions of octachlorocyclotetraphosphazene, N(4)P(4)Cl(8), with N(2)O(2) donor-type aminopodands (1a, 1b, 1g, and 1h) afforded two kinds of derivatives, namely, spiro-ansa-spiro (sas) (2a, 2b, 2g, and 2h) and ansa-spiro-ansa (asa) (3a and 3b) phosphazenes. The partly substituted sas phosphazenes (2a and 2b) reacted with excess pyrrolidine and morpholine in tetrahydrofuran to produce the tetrapyrrolidino (2c and 2d) and morpholino (2e and 2f) derivatives. The reactions of the asa phosphazenes (3a and 3b) with excess pyrrolidine and morpholine produced gem-2-trans-6-dichloropyrrolidinophosphazenes (3c and 3d) and -morpholinophosphazenes (3e and 3f). However, the fully substituted products were not obtained in these solvents. In addition, the expected fully substituted compound was not obtained from the reaction of 3a with excess pyrrolidine by standard or microwave-assisted methods. The reaction of the long-chain starting compound (1g) with N(4)P(4)Cl(8) gave sas (2g) and the interesting 2,6-ansa-spiro-bicyclo product (bicyclo-2,6-as; 4g), while the reaction of 1h with N(4)P(4)Cl(8) yielded only sas (2h). The structural investigations of the compounds were verified by elemental analyses, mass spectrometry, Fourier transform infrared, and DEPT, HSQC, HMBC, (1)H, (13)C, and (31)P NMR techniques. The crystal structures of 2b, 3a, 3b, 3e, and 4g were determined by X-ray crystallography. Compounds 2a-2h, 3a-3f, and 4g had two stereogenic P atoms. Compound 3b had one enantiomer according to the Flack parameter, and 3f was a racemic mixture, as shown by chiral high-performance liquid chromatography and chiral-solvating-agent, (R)-(+)-2,2,2-trifluoro-1-(9'-anthryl)ethanol, experiments. Furthermore, compounds 2a, 2c, and 2d exhibited weak antibacterial activity against (G+) bacterium, and 3c and 3d displayed moderate antifungal activity against Candida tropicalis. Gel electrophoresis data demonstrated that 2e, 3c, and 3e promoted the formation of DNA cleavage. The prevention of BamHI digestion by 2a-2f and 3a-3f, except 2b and 2e, disclosed binding with GG nucleotides in DNA.

Novel spirocyclic phosphazene-based epoxy resin for halogen-free fire resistance: synthesis, curing behaviors, and flammability characteristics

A novel halogen-free fire resistant epoxy resin with pendent spiro-cyclotriphosphazene groups was designed and synthesized via a three-step synthetic pathway. The chemical structures and compositions of spiro-cyclotriphosphazene precursors and final product were confirmed by (1)H, (13)C, and (31)P NMR spectroscopy, mass spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. The thermal curing behaviors of the synthesized epoxy resin with 4,4'-diamino-diphenylmethane, 4,4'-diamino-diphenyl sulfone, and novolac as hardeners were investigated by differential scanning calorimetry (DSC), and the curing kinetics were also studied under a nonisothermal condition. The evaluation of the thermal properties demonstrated that these thermosets achieved a good thermal resistance due to their high glass transition temperatures more than 150 °C, and also gained high thermal stabilities with high char yields. The flammability characteristics of the spirocyclic phosphazene-based epoxy thermosets cured with these three hardeners were investigated on the basis of the results obtained from the limiting oxygen index (LOI) and UL-94 vertical burning experiments as well as the analysis of the residual chars collected from the vertical burning tests. The high LOI values and UL-94 V-0 classification of these epoxy thermosets indicated that the incorporation of phosphazene rings into the backbone chain imparts nonflammability to the epoxy resin owing to the unique combination of phosphorus and nitrogen following by a synergistic effect on flame retardancy. The epoxy resin obtained in this study is a green functional polymer and will become a potential candidate for fire- and heat-resistant applications in electronic and microelectronic fields with more safety and excellent performance.

Phosphorus-nitrogen compounds Part 17: The synthesis, spectral and electrochemical investigations of porphyrino-phosphazenes

The reactions of unsymmetrical porphyrins (1 and 2) with Ni(OAc)2·4H2O in boiling DMF produce porphyrin complexes (3 and 4). From the reactions of free porphyrin ligands 1 and 2 with hexachlorocyclotriphosphazatriene, N3P3Cl6 , the new free porphyrino-phosphazene derivatives (5 and 6) are obtained. On the other hand, the reactions of N3P3Cl6 with porphyrin complexes (3 and 4) afford the new porphyrino-phosphazene complexes (7 and 8). In the literature there are a few examples of the porphyrino-phosphazene architectures. The structural investigations of all the compounds have been made by elemental analyses, MS, FTIR, 1H NMR, 31P NMR and UV-visible techniques. The cyclic voltammograms (CVs) are examined in acetonitrile (MeCN) containing 0.1 M tetrabutylammonium-tetrafluoroborate (TBATFB) to investigate the surface attachment properties at the glassy carbon electrode (GCE) and the influence of the presence of metal cations in the porphyrin ring.

Phosphorus-nitrogen compounds. 21. Syntheses, structural investigations, biological activities, and DNA interactions of new N/O spirocyclic phosphazene derivatives. The NMR behaviors of chiral phosphazenes with stereogenic centers upon the addition of chiral solvating agents

The reactions of hexachlorocyclotriphosphazatriene, N(3)P(3)Cl(6), with N/O-donor-type N-alkyl (or aryl)-o-hydroxybenzylamines (1a-1e) produce mono- (2a-2e), di- (3a-3d), and tri- (4a and 4b) spirocyclic phosphazenes. The tetrapyrrolidino monospirocyclic phosphazenes (2f-2i) are prepared from the reactions of partly substituted compounds (2a-2d) with excess pyrrolidine. The dispirodipyrrolidinophosphazenes (3e-3h) and trispirophosphazenes (3i-3k) are obtained from the reactions of trans-dispirophosphazenes with excess pyrrolidine and sodium (3-amino-1-propanoxide), respectively. Compounds 3a-3d have cis and trans geometric isomers. Only the trans isomers of these compounds are isolated. Compounds 3a-3h have two stereogenic P atoms. They are expected to be in cis (meso) and trans (racemic) geometric isomers. In the trans trispiro compounds (3i-3k), there are three stereogenic P atoms. They are expected to be in racemic mixtures. The stereogenic properties of 3a-3k are confirmed by (31)P NMR spectroscopy upon the addition of the chiral solvating agent; (S)-(+)-2,2,2-trifluoro-1-(9'-anthryl)ethanol. The molecular structures of 3i-3k, 4a, and 4b look similar to a propeller, where the chemical environment of one P atom is different from that of others. Additionally, 4a and 4b are also expected to exist as cis-trans-trans and cis-cis-cis geometric isomers, but both of them are found to be in cis-trans-trans geometries. The solid-state structures of 2a, 2e, 2f, 3e, and 3f are determined by X-ray crystallography. The compounds 2f-2i, 3e-3i, and 3k are screened for antibacterial activity against gram-positive and gram-negative bacteria and for antifungal activity against yeast strains. These compounds (except 3f) have shown a strong affinity against most of the bacteria. Minimum inhibitory concentrations (MIC) are determined for 2f-2i, 3e-3i, and 3k. DNA binding and the nature of interaction with pUC18 plasmid DNA are studied. The compounds 2f-2i, 3e-3i, and 3k induce changes on the DNA mobility. The prevention of BamHI and HindIII digestion (except 2g) with compounds indicates that the compounds bind with nucleotides in DNA.

Cyclotriphosphazene ring as a platform for multiporphyrin assemblies

A simple method has been employed to synthesize a cyclotriphosphazene appended with six porphyrins. The reaction of one equivalent of hexachlorocyclotriphosphazene with six equivalents of 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl)porphyrin or -21-thiaporphyrin in tetrahydrofuran in the presence of cesium carbonate, followed by simple column-chromatography purification, afforded the hexaporphyrinato cyclotriphosphazene systems as the single products in 80-90 % yields. The metal(II) derivatives (Cu(II), Zn(II)) of the hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assemblies with the appropriate metal salts under standard metallation conditions. The compounds are freely soluble in common organic solvents and were characterized by mass spectrometry, NMR, absorption, and fluorescence spectroscopy, and electrochemical techniques. Material studies carried out by using fluorescence microscopy, SEM, and AFM techniques showed that the hexaporphyrinato cyclotriphosphazene systems form ringlike architectures. Preliminary biological studies indicate that the hexacopper(II) porphyrin assembly can be used as an artificial nuclease.