Cyclic Phosphazenes Research Articles

Molecular-Cling-Effect of Fluoroethylene Carbonate Characterized via Ethoxy(pentafluoro)cyclotriphosphazene on SiOx/C Anode Materials - A New Perspective for Formerly Sub-Sufficient SEI Forming Additive Compounds.

Effective electrolyte compositions are of primary importance in raising the performance of lithium-ion batteries (LIBs). Recently, fluorinated cyclic phosphazenes in combination with fluoroethylene carbonate (FEC) have been introduced as promising electrolyte additives, which can decompose to form an effective dense, uniform, and thin protective layer on the surface of electrodes. Although the basic electrochemical aspects of cyclic fluorinated phosphazenes combined with FEC were introduced, it is still unclear how these two compounds interact constructively during operation. This study investigates the complementary effect of FEC and ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN) in aprotic organic electrolyte in LiNi0.5 Co0.2 Mn0.3 O ∥ SiOx /C full cells. The formation mechanism of lithium ethyl methyl carbonate (LEMC)-EtPFPN interphasial intermediate products and the reaction mechanism of lithium alkoxide with EtPFPN are proposed and supported by Density Functional Theory calculations. A novel property of FEC is also discussed here, called molecular-cling-effect (MCE). To the best knowledge, the MCE has not been reported in the literature, although FEC belongs to one of the most investigated electrolyte additives. The beneficial MCE of FEC toward the sub-sufficient solid-electrolyte interphase forming additive compound EtPFPN is investigated via gas chromatography-mass spectrometry, gas chromatography high resolution-accurate mass spectrometry, in situ shell-isolated nanoparticle-enhanced Raman spectroscopy, and scanning electron microscopy.

Synthesis, optical, and structural properties of bisphenol-bridged aromatic cyclic phosphazenes.

Phenoxy- and naphthoxy-substituted bisphenol-bridged cyclic phosphazenes were synthesized in 2 steps and their thermal, photophysical, and electrochemical properties were investigated. The structures of the cyclic phosphazene compounds were determined by ESI-MS mass spectrometry and 1 H, 13 C, and 31 P NMR spectroscopies. The photophysical studies of phenoxy- and naphthoxy-substituted bridged cyclophosphazenes were investigated by means of absorption and fluorescence spectroscopies in different solvents. Thermal and electrochemical properties of the target compounds were also studied. Furthermore, the excimer emissions through intramolecular interactions in solution and in solid state were investigated by fluorescence spectroscopy and the theoretical calculations were performed in detail using DFT.

High-Pressure Synthesis of Cyclic Phosphazenes by Near-UV Photoinduced Reactivity of NH3 and Elemental Phosphorus

A comparison between the high-pressure (0.8 GPa) photoinduced reactivity of black and red phosphorus at ambient temperature in the presence of ammonia has been conducted in diamond anvil cells (DAC...

Polyphosphazenes and Cyclotriphosphazenes with Propeller-like Tetraphenylethyleneoxy Side Groups: Tuning Mechanical and Optoelectronic Properties

A new class of polyphosphazene elastomers has been synthesized that combines a −P═N– backbone with both 2,2,2-trifluoroethoxy and tetraphenylethyleneoxy (TPEO) side groups. The polymer syntheses and photoproperties were first modeled using small molecule cyclic phosphazenes, and these were then applied to the high polymers. The TPEO groups confer useful mechanical and photophysical properties on the polymers. Thus, those polyphosphazenes with the more rigid bidentate TPEO side groups have higher fluorescence quantum yields than counterparts with monodentate TPEO groups. Different TPEO substituents also allow tuning of the side-group interactions to modify the elastomeric properties of the polymers. For example, the two-dimensional TPEO unit is a stronger physical cross-linker than the comparable cross-linkers used in earlier polyphosphazene elastomers. Thus, the elastomeric polymers containing the two-dimensional TPEO exhibit greatly improved mechanical properties compared to the previous ones. Moreover, ...

Molecular structure, linear and nonlinear optical properties of some cyclic phosphazenes: A theoretical investigation

We report ab initio and density functional theory calculations of structural data, dipole moment, diagonal vibrational and electronic contributions to polarizability, vibrational and electronic contributions to first hyperpolarizability of some cyclic phosphazenes. The electronic structure of substituted cyclic phosphazenes has been investigated using Hartree-Fock and density functional theory. The vibrational and electronic contributions to polarizabilities and first hyperpolarizability of these molecules were calculated with HF method, and different DFT levels used the traditional B3LYP and PBE functional and the long-range corrected functional like Coulomb-attenuating method CAM-B3LYP, LC-BLYP and wB97XD used different basis sets. These cyclic phosphazenes adopts a planar structure. The chosen level of theory was found to describe satisfactory the molecular structure (r. m. s. of the relative deviations). The study reveals that the cyclic phosphazenes derivatives have large vibrational contribution to static first hyperpolarizability values. The results obtained from this work will provide into the electronic properties of this important class of inorganic polymers.

Structural Data, Linear and Nonlinear Optical Properties of Some Cyclic Phosphazenes: A Theoretical Investigation

We report ab initio and DFT calculation of structural data, dipole moment, diagonal vibrational and electronic contributions to polarizability, vibrational and electronic contributions to first hyperpolarizability of some cyclic phosphazenes. The electronic structure of substituted cyclic phosphazenes has been investigated using Hartree-Fock and density functional theory. The vibrational and electronic contributions to polarizabilities and first hyperpolarizability of these molecules were calculated with HF method, and different DFT levels used the traditional B3LYP and PBE functional and the long-range corrected functional like Coulomb-attenuating method CAM-B3LYP, LC-BLYP and wB97XD used different basis sets. These cyclic phosphazenes adopts a planar structure. The study reveals that the cyclic phosphazenes derivatives have large vibrational contribution to static first hyperpolarizability values. The results obtained from this work will provide into the electronic properties of this important class of inorganic polymers.

Influence of phosphazenes of various structures on the curing parameters and thermal oxidative degradation of oligomethylphenylsiloxane

Scientific and applied aspects of possible use of cyclic phosphazenes, by-products from phosphonitrilic anilide synthesis, as thermal stabilizers were considered. The solubility and thermal oxidative stability of phosphonitrile anilide trimer and tetramer were studied, the dependence of the curing parameters of oligomethylphenylsiloxane compositions (gel time, temperature intervals of curing) from the structure of the modifying additive was examined, and the resistance of compositions based on oligomethylphenylsiloxane modified with linear and cyclic oligophosphazenes to thermal oxidation at 350°C was evaluated.

Synthesis and fluorescence properties of hexameric and octameric subphthalocyanines based cyclic phosphazenes

Abstract Hexameric and octameric subphthalocyanines bearing cyclophosphazene derivatives were synthesized by threating hexa(p-hydroxyphenoxy)cyclotriphosphazene and octa(p-hydroxyphenoxy)cyclotetraphosphazene with excess of boron subphthalocyanine chloride in toluene. The hexameric and octameric subphthalocyanines bearing cyclophosphazene derivatives were fully characterized by elemental analysis, ESI and MALDI mass spectrometry, FT-IR, 1 H, 13 C and 31 P NMR spectroscopy. The photophysical properties of title compounds were investigated by means of UV/Vis absorption and fluorescence spectroscopies in dilute 1,4-dioxane solutions. The fluorescence quenching behavior of these complexes by 1,4-benzoquinone were also reported.

Lithium binding in fluorinated phosphazene trimers

Density functional theory is used to model a series of cyclic phosphazenes, with and without coordinated Li+. Two pendant groups are used, ethoxy and 2,2,2-trifluoroethoxy, in varying combinations to generate phosphazenes with 0, 1, 2, 3, or 6 trifluoro groups. In all cases, Li+ sits in a pocket on the ring, always bonding to a ring nitrogen, and can be three- or four-coordinate, depending on the local environment. Three-coordinate occurs when no fluorines are close enough to interact, with the lithium bonding to a ring nitrogen and the two adjacent oxygens. When Li+ is four-coordinate, the bonding varies between the ring nitrogen, two adjacent oxygens, and one fluorine, or the ring nitrogen, one adjacent oxygen, and two fluorines. All of the possible symmetry unique structures have been calculated. The binding strength of Li+ steadily decreases, from 74.93kcal/mol with no trifluoro groups, to 58.01kcal/mol when 6 trifluoro groups are present. The decrease is attributed to the electron withdrawing effect of the trifluoro groups, and also to distortions in the geometry to accommodate Li–F interactions.

Using Density Functional Theory To Interpret the Infrared Spectra of Flexible Cyclic Phosphazenes

The cyclic phosphazene trimer P(3)N(3)(OCH(2)CF(3))(6)and the related cyclic tetramer P(4)N(4)(OCH(2)CF(3))(8) have been synthesized, isolated and their vapor-phase absorption spectra recorded at moderate resolution using an FTIR spectrometer. The interpretation of these spectra is achieved primarily by comparison with the results of high-precision density functional calculations, which enable the principal absorption features to be assigned and conclusions to be drawn regarding the geometries and conformations adopted by both molecules. These in turn allow interesting comparisons to be made with analogous cyclic halo-phosphazenes (such as P(3)N(3)Cl(6)) and other related ring compounds. The highly flexible nature of the two cyclic phosphazenes precludes a complete theoretical study of their potential energy hypersurfaces and a novel alternative approach involving the analysis of a carefully selected subset of the possible molecular conformations has been shown to produce satisfactory results. The two cyclic phosphazene oligomers have been proposed as the major low-to-medium temperature pyrolysis products of the parent polyphosphazene (PN(OCH(2)CF(3))(2))(n), and the identification of vibrational absorption features characteristic of each molecule will enable future studies to test the validity of this proposition.

Synthesis, thermal and photophysical properties of naphthoxycyclotriphosphazenyl-substituted dendrimeric cyclic phosphazenes

The synthesis and properties of naphthoxycyclotriphosphazenyl-substituted dendrimeric cyclic phosphazenes are reported. Compound 3, [N3P3(ONp)5OPhOH], is prepared by the sequential reactions of hexachlorocyclotriphosphazene with 2-naphthol and 4-benzyloxyphenol derivatives, as side groups. The dendrimeric compounds 5, 6 and 7 have been obtained by the reactions of compound 3 with hexachlorocyclotriphosphazene, N3P3Cl6, octachlorocyclotetraphosphazene, N4P4Cl8, and bisphenol bridged cyclophosphazene, N6P6Cl10 (4), respectively. The newly synthesized compounds have been fully characterized by elemental analysis, ESI, MALDI-TOF mass spectrometry, FT-IR, 1H, 13C and 31P NMR spectroscopy. The thermal stability and fluorescence spectral properties of all these novel compounds are investigated.

Studies of polycyanurates based on phenoxy-substituted cyclic phosphazenes: Synthesis of the monomer and a preliminary study of its thermal properties in binary blends

The four-step preparation of a new monomer, 1,2,3-tris(4-cyanatophenoxy)-,3′,5,5-tris-phenoxy-2λ5,4λ5,6λ5-[1,3,5,2,4,6]-triazatriphosphinine, is reported. Characterization of the monomer is undertaken using spectroscopic and chromatographic methods and elemental analysis and the data are in agreement with the proposed structure (as a mixture of isomers). The thermal polymerization of the monomer and its behaviour within selected blends containing 2,2-bis(4-cyanatophenyl)propane (AroCy B10) are studied using differential scanning calorimetry. The blends appear to melt sharply at ca. 80 °C onset of polymerization (corresponding to the melting point of the commercial dicyanate) before commencing polymerization directly thereafter. Typical exothermic peak maxima at ca. 135 °C are observed, whilst the cure is apparently concluded by 200 °C under the scanning conditions. On rescan, the cured samples display glass transition values in the region of 160–190 °C, depending on composition with the higher values reflecting increasing amounts of the new material. The cured polycyanurate of the tricyclophosphazene is also analysed using thermogravimetric analysis and displays a mass loss of 5% at approximately 381 °C in air and 366 °C in nitrogen. When 1,2,3-tris(4-cyanatophenoxy)-,3′,5,5-tris-phenoxy-2λ5,4λ5,6λ5-[1,3,5,2,4,6]-triazatriphosphinine is combined with AroCy B10, the cured copolymers (containing between 10 and 30 wt% of the tricyclophosphazene) show disappointing thermal stability with a progressive reduction in the onset of degradation with increasing phosphazine content; this may be a result of incomplete cure.

Phosphazene-Based Host Materials for the Use in Blue Phosphorescent Organic Light-Emitting Diodes

We present a series of low-molecular-weight materials based on cyclic phosphazenes for the use as host materials in blue phosphorescent organic light-emitting diodes. Substituted phenyl rings are attached to the central phosphazene ring either via phosphorus–oxygen bonds to yield phenoxy-substituted derivatives or via direct phosphorus–carbon bonds to yield phenyl-substituted derivatives. The phenoxy substituted cyclic phosphazenes were prepared by nucleophilic substitution of the six chlorine atoms in hexachlorocyclotriphosphazene with phenoxy groups, whereas the phenyl substituted cyclic phosphazenes were formed in a cyclocondensation reaction of three equivalents of substituted phosphinic amides. The phenyl substitution leads to materials with superior thermal properties compared to the phenoxy substitution. Because of the nonconjugated linkage to the phosphazene core, the host materials have very high triplet energies of more than 3 eV. In an OLED device using one compound as host for the saturated bl...

Studies on the mechanism of phosphazene ring-opening polymerization (ROP)

In this study, the ring-opening polymerization (ROP) of cyclic trimer N_3P_3Cl_6 catalyzed by [Et_3Si(N_3 P_3Cl_6)][CHB_{11}H_5Br_6] (3) obtained from the reaction of N_3P_3Cl_6 (1) and Et_3Si(CHB_{11}H_5Br_6) (2) at room temperature was investigated. This provided a unique opportunity to explore the polymerization mechanism. The coordinatively unsaturated cation [N_3P_3Cl_5]^+ is responsible for the ROP of N_3P_3Cl_6, and is formed by the intramolecular elimination of Et_3SiCl from 3. The detection of Et_3SiCl by ^1H-NMR as the catalysis proceeded offers new evidence for the formation of [N_3P_3Cl_5]^+. The progress of the catalysis was followed using ^{31} P-NMR and revealed the build-up of a polymer. Cyclic phosphazenes with rings larger than that of N_3P_3Cl_6 [(Cl_2P=N)_n (n = 4-7)] were observed fairly early in the course of the ROP. The propagation of that polymerization at room temperature proceeded via a living cationic mechanism.

Liquid chromatography/electrospray time‐of‐flight mass spectrometry for the characterisation of cyclic phosphazenes

Cyclic phosphazenes with different substituents were synthesised and investigated by liquid chromatography (LC) and electrospray ionisation mass spectrometry (ESI-MS). Hexachlorocyclotriphosphazene was functionalised with aliphatic substituents as alcohols and amines, leading to product mixtures, which were subsequently analysed. In contrast to classical methods of structural analysis such as nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography, which are restricted to pure compounds, these complex mixtures can favourably be analysed by means of LC/ESI-MS. The main products could be separated from by-products and, moreover, all the components of the unknown mixture were unambiguously identified by accurate mass measurements. For all compounds with different side-chain ratios, remaining chlorine atoms or hydroxyl groups and even for spiro or ansa products, molecular structures could be suggested.

Ring-Closing Metathesis Reactions of Terminal Alkene-Derived Cyclic Phosphazenes

The first examples of ring-closing metathesis (RCM) reactions of a series of terminal alkene-derived cyclic phosphazenes have been carried out. The tetrakis-, hexakis-, and octakis(allyloxy)cyclophosphazenes (NPPh(2))(NP(OCH(2)CH=CH(2))(2))(2) (1), N(3)P(3)(OCH(2)CH=CH(2))(6) (2), and N(4)P(4)(OCH(2)CH=CH(2))(8) (3) and the tetrakis(allyloxy)-S-phenylthionylphosphazene (NS(O)Ph)[NP(OCH(2)CH=CH(2))(2)](2) (4) were prepared by the reactions of CH(2)=CHCH(2)ONa with the cyclophosphazenes (NPPh(2))(NPCl(2))(2), N(3)P(3)Cl(6), and N(4)P(4)Cl(8) and the S-phenylthionylphosphazene (NS(O)Ph)(NPCl(2))(2). The reactions of 1-4 with Grubbs first-generation olefin metathesis catalyst Cl(2)Ru=CHPh(PCy(3))(2) resulted in the selective formation of seven-membered di-, tri-, and tetraspirocyclic phosphazene compounds (NPPh(2))[NP(OCH(2)CH=CHCH(2)O)](2) (5), N(3)P(3)(OCH(2)CH=CHCH(2)O)(3) (6), and N(4)P(4)(OCH(2)CH=CHCH(2)O)(4) (7) and the dispirocyclic S-phenylthionylphosphazene compound (NS(O)Ph)[NP(OCH(2)CH=CHCH(2)O)](2) (8). X-ray structural studies of 5-8 indicated that the double bond of the spiro-substituted cycloalkene units is in the cis orientation in these compounds. In contrast to the reactions of 1-4, RCM reactions of the homoallyloxy-derived cyclophosphazene and thionylphosphazene (NPPh(2))[NP(OCH(2)CH(2)CH=CH(2))(2)](2) (9) and (NS(O)Ph)[NP(OCH(2)CH(2)CH=CH(2))(2)](2) (10) with the same catalyst resulted in the formation of 11-membered diansa compounds NPPh(2)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)](2) (11) and (NS(O)Ph)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)](2) (13) and the intermolecular doubly bridged ansa-dibino-ansa compounds 12 and 14. The X-ray structural studies of compounds 11 and 13 indicated that the double bonds of the ansa-substituted cycloalkene units are in the trans orientation in these compounds. The geminal bis(homoallyloxy)tetraphenylcyclotriphosphazene [NPPh(2)](2)[NP(OCH(2)CH(2)CH=CH(2))(2)] (15) upon RCM with Grubbs first- and second-generation catalysts gave the spirocyclic product [NPPh(2)](2)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)] (16) along with the geminal dibino-substituted dimeric compound [NPPh(2)](2)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)(2)PN][NPPh(2)](2) (17) as the major product. The dibino compound 17, upon reaction with the Grubbs second-generation catalyst, was found to undergo a unique ring-opening metathesis reaction, opening up the bino bridges and partially converting to the spirocyclic compound 16.

Synthesis, thermal and photophysical properties of phenoxy-substituted dendrimeric cyclic phosphazenes

In the present study, we describe the synthesis of a hydroxyl substituted bridged phenoxycyclotriphosphazene (5), [N3P3(OPh)5OPhO(OPh)5N3P3OPhOH], as a side group and its use for preparation of dendrimeric cyclic phosphazenes. For this purposes, compound 5 is synthesised in five steps from the reactions of cyclotriphosphazene with phenol derivatives. The dendrimeric compounds 6 and 7 have been prepared by the reactions of compound 5 with hexachlorocyclotriphosphazene, N3P3Cl6, or octachlorocyclotetraphosphazene, N4P4Cl8, respectively. Newly synthesized compounds have been fully characterized by elemental analysis, MALDI-TOF mass spectrometry, FT-IR, 1H, 13C and 31P NMR spectroscopy. The thermal stability and fluorescence spectral properties of dendrimeric compounds 6 and 7 are investigated and compared with that of the previously reported cyclic compounds (I–II). Fluorescence quantum yields and lifetimes of dendrimeric compounds and their quenching behaviour by 1,4-benzoquinone are studied in dichloromethane.

ChemInform Abstract: Ring Expansion and Equilibration in Organophosphazenes and the Relationship to Polymerization.

A series of cyclic trimeric phosphazenes that bear both halogen and organic side groups have been found to undergo ring expansion-equilibration reactions at elevated temperatures. Compounds N 3 P 3 F 5 CMe 3 , N 3 P 3 F 5 Ph, non-gem-N 3 P 3 F 4 (CMe 3 ) 2 , N 3 P 3 F 4 Ph 2 , N 3 P 3 Cl 4 Me 2 , N 3 P 3 Cl 4 Et 2 , N 3 P 3 Cl 3 Me 3 , and N 3 P 3 Cl 3 Et 3 yield cyclic tetramers, pentamers, hexamers, and, in some cases, heptamers, octamers, and nonamers when heated. The cyclic tetramers (NPClMe) 4 and (NPClEt) 4 also equilibrate to a range of cyclic species that range from trimer to hexamer. Several of these equilibrations also lead to the formation of high polymers. The results are discussed in terms of possible mechanisms for ring-ring equilibration and polymerization

ChemInform Abstract: Synthesis and Structure of Small-Molecule Cyclic Phosphazenes Bearing ortho-Substituted Aryloxy and Phenoxy Substituents.

A series of cyclic trimeric and tetramcric phosphazenes with ortho-substitutcd aryloxy side groups have been synthesized. The ortho substituents are methyl and phenyl groups. These compounds are structural models for the corresponding linear high-polymeric phosphazenes. X-ray structural analysis of the cyclic tetrameric species [NP(OC 6 H 4 CH 3 -2) 2 ] 4 (3), (NP(OC 6 H 4 C 6 -H 5 -2) 2 ] 4 (4) and [NP(OC 6 H 5 ) 2 ] 4 are reported

Synthesis and inclusion behavior of cyclotriphosphazene molecules with asymmetric spiro rings

Two novel cyclic phosphazenes with asymmetric spiro rings were synthesized via reactions of hexachlorocyclotriphosphazene with chiral amino alcohol residues. The reactions showed preferential formation of the cis isomer possibly due to the delocalization of the lone pair electrons of the spirocylic nitrogen, which reduces its ability to solvate protons. Crystals of these phosphazenes were analyzed by X-ray crystallography which confirmed the formation of cis isomers and showed their ability to include guest molecules within the crystal lattices. The selective inclusion of epoxides by one of the phosphazenes was an effective method for the separation of thermally sensitive guest molecules.