Phosphorus-nitrogen compounds. 26. Molecular motion and molecular separations in cyclophosphazene clathrates

Synthesis of Trispirocyclotriphosphazenes with Oxaphosphorine Rings and Their Crystal and Molecular Structures

Novel trispirocyclotriphosphazenes with oxaphosphorine rings (DOP-PZs) were successfully synthesized by an Appel reaction with phosphoramide, which was prepared from ammonia and 10-chloro-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derived from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, generally abbreviated as DOPO. The resulting DOP-PZs were characterized by ¹H, ¹³C{¹H}, and ³¹P{¹H} nuclear magnetic resonance spectroscopy and time-of-flight mass spectrometry and shown to consist of cis-trans isomers. Moreover, the crystal and molecular structures of the DOP-PZs were determined by X-ray diffraction; cis- and trans-DOP-PZs (C₃₆H₂₄N₃O₃P₃, M = 639.49 g/mol) were refined to final R₁ values of 0.0260 and 0.0463, respectively, with the SHELXL refinement package using least-squares minimization. The crystal of cis-DOP-PZ is trigonal in space group R3c and the following cell constants: a = 19.5984(5) Å, c = 13.2754(4) Å, V = 4415.9(3) ų, Z = 6, and Flack parameter = 0.038(8). In contrast, trans-DOP-PZ is monoclinic in space group P2₁/c and the following cell constants: a = 9.98647(18) Å, b = 24.1737(4) Å, c = 12.8472(2) Å, β = 112.649(8)°, V = 2862.26(18) ų, and Z = 4. The molecular structures of these DOP-PZs were compared with those of other trispirocyclotriphosphazenes. In addition, the DOP-PZs showed high thermal stability up to 400 °C, with dielectric constants of 2.76-2.77 and dissipation factors of 0.0017-0.0031 at 10 GHz.

Preparation and Characterization of New Inclusion Compounds Using Stable Nitroxide Radicals and an Organic 1-D Nanochannel as a Template

A new inclusion compound (IC) using di-t-buthyl nitroxide (DBNO) radical and tris(o-phenylenedioxy)cyclotriphosphazene (TPP) (1), which has an organic one-dimensional (1-D) nanochannel in the crystal, is reported. According to the characterization using thermogravimetric analysis (TG), ESR measurements, etc., the composition of the inclusion compound was assigned as TPP:DBNO = 1:0.62. The narrowing of the isotropic ESR adsorption line of 1 was observed with a temperature increase from 103 K to room temperature. The line shape indicated a type of 1-D spin diffusion as observed in our previous study of the IC using TPP and 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO).

Modulation of tris(o-phenylenedioxy)cyclotrisphosphazene (TPP) properties for zeolite use: effect of pi-conjugation length and CH/N heterosubstitution

Highly accurate quantum chemical calculations were used in a comparative study of the pi-conjugation length and CH/N heterosubstitution effects on the structure and a number of properties of tris(o-phenylenedioxy)cyclotrisphosphazene (TPP) derivatives to identify the role of each of them in the modulation of the host...guest complex stability and available space for the adsorbate within TPP-like organic zeolite (OZ). From the BH&HLYP/6-31G(d,p) structures it was found that extending the side fragment with a phenyl ring and substituting CH/N preserve the "paddle wheel" molecular shape, a key factor in the tunnel formation on which the organic zeolite use of TPP is based on. Compared to the unsubstituted molecules, the side fragment is shortened for CH/N heterosubstitution, which may decrease the diameter of the tunnel. In addition, through accurate ionization potential (IP) calculations (at the HF/6-311+G(d) level) the electron-donor (E-D) capacity was found to be more significantly enhanced by a lateral than a linear extension with phenyl ring, while it decreased upon CH/N heterosubstitution, which can affect the stability of some related host...guest complexes in the same order. Finally, as recently reported for TPP, the current results based on PBE0/6-31G(d,p) show that upon release of an electron the structural stability may not be altered by a CH/N mono- or disubstitution. From these features it was concluded that if the crystal requirement can be attained clathrates of good tolerance toward guest molecules in a wide range of Lewis acidity with variable E-D strength and available space for adsorbates may be reasonably awaited by exploiting these two approaches.

Influence of the substituted side group on the molecular structure and electronic properties of TPP and related implications on organic zeolites use

Tris(o-phenylenedioxy)cyclotriphosphazene (TPP) became a compound of choice to investigate the structural features of organic zeolite and their potential applications. Different TPP-like materials are studied in this Letter from the electron-donor (E-D) capacity viewpoint, since this was reported as a stabilizing parameter of the TPP-Lewis acid inclusion compound up to high temperatures. On the basis of DFT-PBE0/6-31G(d,p) calculations, the results reported herein show a tight dependence of the E-D of the entire molecule on that of the side group. It was shown that both the O/NH substitution and the extension of the phenylenedioxyl group with an aromatic ring significantly enhance the E-D. As a result, the corresponding clathrates, including some reported ones, may also be exploited for the same issue, with an even wider range of operating temperatures when trapping compounds of Lewis acidity character comparable to that of I2. Furthermore, it was concluded that these two strategies may significantly enhance the E-D capacity without altering the tolerance of TPP-like host materials to the guest molecules.

Design of TTF-Based Phosphazenes Combining a Good Electron-Donor Capacity and Possible Inclusion Adduct Formation

The physical properties of porous material can be modulated by intercalation of small molecules, whose size, in the case of tris-o-phenylenedioxy)cyclotriphosphazene (TPP)-based materials, vary with the different side groups. Starting from the TPP structure, a series of new derivatives were constructed through the core ring [(NP)(3)] substitution by [(CNH)(3)], [(CO)(3)], and [(CS)(3)] or/and the side group substitution by tetrathiafulvalene and a series of related fragments including bis(ethylenedithio)tetrathiafulvalene, 2-methylene-1, 3-dithiole, and 2-methylene-5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiine. In the side fragment, such a substitution corresponds to the replacement of a ring heteroatom, an addition of substituents, or both. With use of theoretical methodologies based on DFT-B3LYP/6-31G* and HF/6-31G*//B3LYP/6-31G* approaches, molecular geometries and electronic properties including the LUMO and HOMO energies, the HOMO-LUMO gap, as well as the ionization potential (IP) were calculated. In comparison with the commonly used organic superconductors, most of the molecules investigated were predicted to show comparable or better electron-donor strength. Interestingly, a number of cyclophosphazene [(NP)(3)]-containing compounds were predicted to show the "paddle wheel" shape responsible for inclusion adducts formation, making these compounds to be potential candidates for organic superconductors with the ease of modulating their conducting properties by intercalation of suitable acceptors.

Molecular dynamics and ordering of pyridine in its cyclophosphazene inclusion compound as evaluated by solid state 2H NMR spectroscopy

Variable temperature 2H NMR experiments (line shape analysis, relaxation studies) were carried out on the pyridine-d5-tris-(1,2-dioxyphenyl)-cyclotriphosphazene inclusion compound in the temperature range between 110-300 K. It is found that the pyridine guests are highly mobile throughout the whole temperature range covered here. The observation of three superimposed 2H NMR signals can be understood in terms of a particular (motionally averaged) orientation of the pyridine molecules, which is a consequence of the molecular symmetry of the pyridine guests and the imposed channel restrictions. The experimental data are consistent with a combined rotation on cone-small angle fluctuation model, which assumes a fast molecular reorientation between two superimposed cones with an opening angle for the inner cone between 59-73 degrees (angle of fluctuation between 1-3 degrees ). On the basis of this model assumption it is possible to reproduce both the experimental 2H NMR line shapes and the spin-lattice relaxation data in a quantitative way. The analysis of the partially relaxed spectra (inversion recovery experiments) yields the correlation times for this overall motional process. They follow an Arrhenius behavior from which an activation energy of 8.7 +/- 0.4 kJ mol(-1) is derived. The results are discussed in the framework of the published data for related systems.

Separation of polyunsaturated fatty acids by selective inclusion in guanidinium-1,5-naphthalenedisulfonate-2-methoxyethanol host networks

Hydrogen-bonded networks composed of guanidinium (G) and 1,5-naphthalenedisulfonate (NDS) have been developed for the selective inclusion and separation of fatty acid esters based on their degree of unsaturation. Porous crystalline networks have been synthesized and include fatty acid esters during crystallization from both methanol and 2-methoxyethanol. Crystalline networks formed in methanol are selective for the inclusion of saturates in preference to polyunsaturated fatty acid methyl esters, but their applicability is limited by the competing inclusion of the solvent methanol. In 2-methoxyethanol, a three-component host structure is formed that provides 4.1 x 4.7 A2 pores which are also selective for saturated fatty acid ester inclusion. These networks do not suffer from the competing inclusion of the solvent 2-methoxyethanol as is the case with methanol, and thus complete removal of initial saturated fatty acid 2-methoxyethyl esters is possible. Binary selectivity experiments on mixtures of the 2-methoxyethyl esters of saturated stearic acid and the omega-3 fatty acid alpha-linolenic acid reveal that this three-component network structure provides nearly complete resolution of these two guests in the crystal and filtrate fractions. Separation of the 2-methoxyethyl esters of alpha-linolenic acid from the monounsaturated oleic acid is also possible, although with decreased efficiency in comparison to removal of the saturated fatty acid ester.

Structural features and molecular assembly of amorphous phosphazenic materials in the bulk--combined theoretical and experimental techniques: Tris-(2,2'-dioxy-1,1'-binaphthyl)cyclotriphosphazen

The structure and the assembly of tris-(2,2'-dioxy-binaphthyl)cyclotriphosphazene [(+)-[NP3(O2C20H12)3], DBNP, in the solid amorphous state was studied using molecular dynamics (MD) including ad hoc quantum mechanically derived force field (FF) parameters, in combination with the energy dispersive X-ray diffraction (EDXD) technique. The atom-atom radial distribution function (RDF) curve obtained through the EDXD experiment revealed low intensity peaks not attributable to the intramolecular distances of the single molecule, but clearly featuring a low energy state of long-distance three-dimensional assembly. The radial distribution functions (RDF) were calculated for various models of DBNP submitted to theoretical MD simulations. Based on the comparison of theoretically calculated RDFs and those obtained from the EDXD experiment, the predominant structural motif of the material in the bulk was found to have DBNP molecules laid one upon the other to form tubular nanostructures. These contain eight DBNP units each (length ca. 46 A) with two and three of these units aligned in parallel and held together. The material can be represented as a bulk of tubular snake-like chains undergoing distortions with a step of eight DBNP units. The bending angles, that vary randomly, attain limited values sufficient to induce disorder and thus nonperiodic structure. The present application of MD simulations combined with EDXD data appear to be a general approach to solve for the first time otherwise intractable issues concerning structural features and assembly of molecular materials in the bulk.