Tris(o-phenylenedioxy)cyclotriphosphazene Research Articles

Inter-Spin Interactions of 1D Chains of Different-Sized Nitroxide Radicals Incorporated in the Organic 1D Nanochannels of Tris(o-phenylenedioxy)cyclotriphosphazene

Abstract Variable-temperature electron spin resonance (ESR) was measured for one-dimensional (1D) molecular chains formed using different-sized organic radicals incorporated into the 1D nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP). The ESR spectra for the molecular chains of 4-oxo-2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPONE) incorporated in the TPP nanochannels ([TPP-TEMPONE]) exhibited anisotropic three-dimensional (3D) spin diffusion at temperatures close to room temperature. In contrast, 1D spin diffusion was observed even at low temperatures indicating a longer rotational diffusion correlation time or the termination of molecular motion of the guest radicals dispersed in the TPP nanochannels. The temperature range for 1D spin diffusion in [TPP-TEMPONE] was higher and wider than that of TPP inclusion compounds incorporating smaller nitroxide radicals, such as di-t-butyl nitroxide (DTBN), or 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) radicals, as previously reported. Thus, inter-spin interactions of the organic-radical 1D molecular chains formed in size-adjustable nanochannels, such as TPP, are influenced by the molecular size and dynamics of guest radicals, and temperature.

High porosity cyclotriphosphazene-based hyper-crosslinked polymers as efficient cationic dye MB adsorbents

Inspired by triptycene unit, the rigid paddle wheel compounds tris(o-phenylenedioxy)cyclotriphosphazene (TPP) and tris(2, 3-naphthalenedioxy)cyclotriphosphazene (TNP) were synthesized and employed as core building blocks to construct high porosity hyper-crosslinked polymers ( HCP-TPP and HCP-TNP ) via Friedel-Crafts alkylation reaction with formaldehyde dimethyl acetal (FDA). The bulk of HCP-TPP and HCP-TNP were comprised of nano-particles and exhibited hierarchical pore structures with remarkable high BET specific surface area of 1641.9 and 1700.2 m 2 g −1 , respectively. The adsorption capacities of HCP-TPP and HCP-TNP toward cationic dye methylene blue (MB) run up to 504.6 and 409.1 mg g −1 at 25 °C, respectively, but they hardly adsorbed anionic dye methyl orange (MO), exhibiting charge selectivity. The adsorption behaviors on MB were in consistence with the pseudo-second-order model and Langmuir model. The estimated thermodynamic parameters indicated the adsorption process was spontaneous and exothermic. Inspired by triptycene unit, the rigid paddle wheel compounds tris(o-phenylenedioxy)cyclotriphosphazene (TPP) and tris(2, 3-naphthalenedioxy)cyclotriphosphazene (TNP) were synthesized and employed as core building blocks to construct high porosity hyper-crosslinked polymers ( HCP-TPP and HCP-TNP ) via Friedel-Crafts alkylation reaction with formaldehyde dimethyl acetal (FDA). The bulk of HCP-TPP and HCP-TNP were comprised of nano-particles and exhibited hierarchical pore structures with remarkable high BET specific surface area of 1641.9 and 1700.2 m 2 g −1 , respectively. The adsorption capacities of HCP-TPP and HCP-TNP toward cationic dye methylene blue (MB) run up to 504.6 and 409.1 mg g −1 at 25 °C, respectively, but they hardly adsorbed anionic dye methyl orange (MO), exhibiting charge selectivity. The adsorption behaviors on MB were in consistence with the pseudo-second-order model and Langmuir model. The estimated thermodynamic parameters indicated the adsorption process was spontaneous and exothermic. • Two novel cyclotriphosphazene-based hyper-crosslinked polymers were prepared from low cost raw materials. • They exhibited hierarchical structures with the highest BET specific surface areas among cyclotriphosphazene -based porous materials. • They charge-selectively absorbed cationic dye methylene blue (MB) with absorption capacities of 504.6 and 409.1 mg g −1 at 25 °C.

Efficient Access to 3D Mesoscopic Prisms in Polymeric Soft Materials.

The preparation of 3D functional isolated mesoscopic assemblies remains a challenge in the self-assembly of polymers. Here, well-defined 3D hexagonal and hexagram prisms with uniform dimensions are acquired by the crystallization of the inclusion complex composed of a crystalline molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and a block copolymer. The crystalline TPP plays an important role in the self-assembling process. The faceted morphologies of the hexagonal and hexagram prisms are infrequent in the self-assembly field of soft materials. The formation of the prisms experiences a 3D growth mechanism. The epitaxial growth, accompanied by the heterogeneous nucleation in the edges, yields the growth of inclusion crystals. This study provides a path to construct well-defined polymeric soft materials with broad utility based on numerous supramolecular complexes.

Bulk Inclusions of Double Pyridazine Molecular Rotors in Hexagonal Tris( o-phenylene)cyclotriphosphazene.

A new generation of double pyridazine molecular rotors differing in intramolecular dipole-dipole spacing was synthesized. All rotor molecules formed bulk inclusions in a tris( o-phenylenedioxy)cyclotriphosphazene (TPP) host. Results of dielectric spectroscopy were fitted to a pair of nine-state models that accounted for interactions of neighboring dipoles at either an aligned or opposed possible orientation of the local threefold dipole rotation potentials within a channel of the TPP host. The results indicate dipole-dipole interaction strengths at the 100 to 200 K scale that lead dipoles to preferentially populate a subset of low-energy configurations. They also reveal that pyridazines with ethynyl substituents in 3- and 6-positions have slightly higher rotational barriers (3.2-3.5 kcal/mol) than those carrying one ethynyl and one tert-butyl group (1.9-3.0 kcal/mol). Upon cooling, these barriers reduce the rate of thermal transitions between the potential wells so much that the inclusions cannot achieve ordered dipolar ground states.

Electron Spin Resonance Study of Molecular Orientation and Dynamics of Phenyl Imino and Nitronyl Nitroxide Radicals in Organic 1D Nanochannels of Tris( o-phenylenedioxy)cyclotriphosphazene.

Imino and nitronyl nitroxide (IN and NN, respectively) radicals such as phenyliminonitroxide (PhIN) and phenylnitronylnitroxide (PhNN), respectively, were dispersed in the organic 1D nanochannels of tris( o-phenylenedioxy)cyclotriphosphazene (TPP). Electron spin resonance (ESR) measurements were conducted on these inclusion compounds (ICs) in the temperature range 4.2-300 K. The modulated-septet ESR spectra of TPP ICs using PhIN observed in the range 165-258 K were reproduced with the EasySpin program package using a model in which some of the PhIN molecules underwent uniaxial rotational diffusion in the TPP nanochannels around the molecular long axis corresponding to the principal y-axis of the g tensor. However, for the TPP IC using PhNN, complicated ESR spectra were observed, which were not consistent with the modulated quintet observed in solution or in the fast-motion limit in solids. These spectra were reproduced by the superposition of a quintet originating from rotational diffusion of PhNN molecules and a septet based on rotational diffusion of PhIN molecules generated in the synthetic process. The rotational diffusion activation energies of PhIN and PhNN in the TPP nanochannels were estimated to be 19 and 45 kJ mol-1 using an Arrhenius plot, respectively. These were consistent with that for NN radicals in the 1D nanochannels of 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) (37-54 kJ mol-1) with a larger pore diameter than TPP reported in our previous study, or with that for 4-substituted-2,2,6,6-tetramethyl-1-piperidinyloxyl (4-X-TEMPO) in TPP nanochannels (5-26 kJ mol-1) with regard to molecular size or host-guest or guest-guest interactions. These results indicate that not only the NN group but also IN may be used for the clarification of chemical or biological structures of nanomaterials such as nanosized cavities.

Inter-Spin Interaction of CLPOT Inclusion Compounds with 1D Molecular Chains of 4-X-TEMPO Radicals in the Temperature Range of 4.2–300 K

Abstract ESR measurements of [CLPOT-(4-X-TEMPO)] inclusion compounds (CLPOT = 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine, and 4-X-TEMPO = 4-substituted-2,2,6,6-tetramethyl-1-piperidinyloxyl radical) with 1D organic-radical molecular chains constructed in organic 1D nanochannels used as templates were conducted in the range of temperatures from 4.2 to 300 K. The peak-to-peak line width (ΔBpp) of all isotropic ESR spectra of the [CLPOT-(4-X-TEMPO)] was much narrower in the whole temperature range than the estimation based on the Van Vleck’s formula for the second moment of the rigid lattice model. In addition, the line profiles of all ESR spectra of the [CLPOT-(4-X-TEMPO)] became Lorentzian in the whole temperature range, compared with our previous results using tris(o-phenylenedioxy)cyclotriphosphazene (TPP) as templates in which the ESR profiles were temperature-dependent. These results indicate that the narrower ESR line width of the [CLPOT-(4-X-TEMPO)] may be caused not by motional narrowing but by 3D exchange interaction even at room temperature although the magnitude was less than 1 K.

Exploiting Host–Guest Interactions for the Synthesis of a Rod–Rod Block Copolymer with Crystalline and Liquid‐Crystalline Blocks

AbstractBy making use of the host–guest interactions between the host molecule tris‐o‐phenylenedioxycyclotriphosphazene (TPP) and the rod–coil block copolymer (BCP) poly(ethylene oxide)‐block‐poly(octyl 4′‐octyloxy‐2‐vinylbiphenyl‐4‐carboxylate) (PEO‐b‐PVBP), the supramolecular rod–rod block copolymer P(EO@TPP)‐b‐PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid‐crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed. The self‐assembled nanostructure is thus clearly affected by the interplay between the two blocks. On the basis of wide‐ and small‐angle X‐ray scattering analysis, we conclude that the supramolecular rod–rod BCP can self‐assemble into a cylinder‐in‐cylinder double hexagonal structure.

Exploiting Host-Guest Interactions for the Synthesis of a Rod-Rod Block Copolymer with Crystalline and Liquid-Crystalline Blocks.

By making use of the host-guest interactions between the host molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and the rod-coil block copolymer (BCP) poly(ethylene oxide)-block-poly(octyl 4'-octyloxy-2-vinylbiphenyl-4-carboxylate) (PEO-b-PVBP), the supramolecular rod-rod block copolymer P(EO@TPP)-b-PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid-crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed. The self-assembled nanostructure is thus clearly affected by the interplay between the two blocks. On the basis of wide- and small-angle X-ray scattering analysis, we conclude that the supramolecular rod-rod BCP can self-assemble into a cylinder-in-cylinder double hexagonal structure.

Bulk Inclusions of Pyridazine‐Based Molecular Rotors in Tris(o‐phenylenedioxy)cyclotriphosphazene (TPP)

A new class of rod‐shaped strongly dipolar molecular rotors for insertion into channels of hexagonal tris(o‐phenylenedioxy)cyclotriphosphazene (TPP) has been examined. Seven different 3,6‐disubstituted pyridazines and one singly 3‐substituted system have been prepared and studied by solid‐state nuclear magnetic resonance (NMR), X‐ray powder diffraction, and dielectric spectroscopy. NMR and X‐ray diffraction both show that all but one of these molecular rotors form hexagonal bulk inclusion compounds with TPP. In‐plane lattice parameters for the hexagonal phases increase with the size of the end group, which also controls the energy barriers for rotation of the pyridazine dipole. The barriers range from ≈4 kcal mol−1 for small or flexible end groups to less than 0.7 kcal mol−1 for 3‐methylbicyclo[1.1.1]pent‐1‐yl end groups after annealing to 235 °C, and an interpretation of these differences is offered. Computer modeling of the relaxed TPP channels followed by density functional calculation of the environment for one of the rotors provides quantitative agreement with the observed barrier. The systems with the lowest rotational barriers show signs of collective behavior, discussed in terms of antiferroelectric intrachannel and ferroelectric interchannel dipole–dipole interactions. A Curie temperature of 22 K is deduced for 3,6‐diadamant‐1′‐ylpyridazine, but no ordered dielectric phases are found. Conclusions have been drawn for improved rotor design.

Arrays of Molecular Rotors with Triptycene Stoppers: Surface Inclusion in Hexagonal Tris(o-phenylenedioxy)cyclotriphosphazene.

A new generation of rod-shaped dipolar molecular rotors designed for controlled insertion into channel arrays in the surface of hexagonal tris(o-phenylenedioxy)cyclotriphosphazene (TPP) has been designed and synthesized. Triptycene is used as a stopper intended to prevent complete insertion, forcing the formation of a surface inclusion. Two widely separated (13)C NMR markers are present in the shaft for monitoring the degree of insertion. The structure of the two-dimensional rotor arrays contained in these surface inclusions was examined by solid-state NMR and X-ray powder diffraction. The NMR markers and the triptycene stopper functioned as designed, but half of the guest molecules were not inserted as deeply into the TPP channels as the other half. As a result, the dipolar rotators were distributed equally in two planes parallel to the crystal surface instead of being located in a single plane as would be required for ferroelectricity. Dielectric spectroscopy revealed rotational barriers of ∼4 kcal/mol but no ferroelectric behavior.

Time-Resolved Fluorescence Anisotropy of Bicyclo[1.1.1]pentane/Tolane-Based Molecular Rods Included in Tris(o-phenylenedioxy)cyclotriphosphazene (TPP).

We examine the fluorescence anisotropy of rod-shaped guests held inside the channels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) host nanocrystals, characterized by powder X-ray diffraction and solid state NMR spectroscopy. We address two issues: (i) are light polarization measurements on an aqueous colloidal solution of TPP nanocrystals meaningful, or is depolarization by scattering excessive? (ii) Can measurements of the rotational mobility of the included guests be performed at low enough loading levels to suppress depolarization by intercrystallite energy transfer? We find that meaningful measurements are possible and demonstrate that the long axis of molecular rods included in TPP channels performs negligible vibrational motion.

Dynamics of TEMPOL Radicals in TPP 1D Nanochannels and Different Molecular Orientation from Other TEMPO Derivatives

Abstract The molecular orientation and dynamics of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPOL) radicals in one-dimensional (1D) nanochannels of the crystal of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) were examined using electron spin resonance (ESR) measurements. TEMPOL radicals in the TPP nanochannels performed rotational diffusion motion not around the principal y axis of the g-tensor, as observed in most cases of TEMPO derivatives, but approximately around the principal z axis with much larger activation energy.

Tris-o-phenylenedioxycyclotriphosphazene (TPP) Inclusion Compounds Containing a Dipolar Molecular Rotor

A rod-shaped molecular rotor consisting of a p-terphenyl shaft attached to p-carborane whose antipodal position carries a dipolar 2,3-dichlorophenyl rotator forms an inclusion compound with hexagonal tris-o-phenylenedioxycyclotriphosphazene (TPP). Results of solid-state NMR spectroscopy, X-ray powder diffraction, dielectric loss spectroscopy, and density functional theory calculations lead us to propose that the whole molecule inserts into the TPP channels, with the rotator located in the outermost surface layer. Although the placement and alignment of the dipoles at the surface appear favorable, the sample does not exhibit collective behavior even at 7 K, presumably due to the relatively large barrier to rotation (∼8.6 kcal/mol). In incompletely annealed samples of the inclusion compound, some of the rotators protrude outside the surface and have a rotational barrier of ∼3.4 kcal/mol. In the inclusion compound of an analog in which the rotator is replaced with a methyl group, some of the methyl substituents are located inside the surface layer of TPP and others protrude above it.

Molecular Orientation and Dynamics of Different Sized Organic Radicals Included in Organic 1D Nanochannels

The molecular orientation and dynamics of di-t-butylnitroxide (DTBN) and 4-oxo-2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPONE) radicals in the organic 1D nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) were investigated by examining inclusion compounds (ICs) diluted by the co-inclusion of nonradicals using electron spin resonance (ESR). Spectral simulation showed that the axial rotation of DTBN or TEMPONE molecules is excited in TPP nanochannels with activation energies of 3 and 10 kJ mol(-1), respectively. The rotation axes for both DTBN and TEMPONE were determined to be almost parallel to the principal y-axis of the g tensor, which agrees with the result reported for 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) in TPP nanochannels, which has the activation energy of 5 kJ mol(-1). These results indicate that the molecular orientations of guest nitroxide radicals are almost independent of the molecular sizes of the guest radicals in TPP nanochannels, although the molecular dynamics are dependent on the molecular sizes.

Inclusion Compound Based Approach to Forming Arrays of Artificial Dipolar Molecular Rotors: A Search for Optimal Rotor Structures

Hexagonal tris(o-phenylenedioxy)cyclotriphosphazene (TPP) is used as ahost for organizing dipolar molecular rotor guests into regular trigonal arrays. Inclusion of molecular rotors with transversely dipolar rotators into TPP channels is followed by solid-state nuclear magnetic resonance, diifferential scanning calorimetry, X-ray diffraction, and dielectric spectroscopy. The more polar of the two rotors does not form an inclusion. The second rotor forms two different inclusions differing in crystallite size and the rotational barriers.

Inclusion Compound Based Approach to Arrays of Artificial Dipolar Molecular Rotors. A Surface Inclusion

We describe an approach to regular triangular arrays of dipolar molecular rotors based on insertion of dipolar rotator carrying shafts as guests into channels of a host, tris(o-phenylenedioxy)cyclotriphosphazene (TPP). The rotor guests can either enter the bulk of the host or stay at or near the surface, if a suitable stopper is installed at the end of the shaft. Differential scanning calorimetry, solid-state NMR, and powder X-ray diffraction were used to examine the insertion of a dipolar rotor synthesized for the purpose, 1-n-hexadecyl-12-(2,3-dichlorophenyl)-p-dicarba-closo-dodecaborane, and it was found that it forms a surface inclusion compound. Rotational barriers from 1.2 to 9 kcal/mol were found by dielectric spectroscopy and were attributed to rotors inserted into the surface to different degrees, some rubbing the surface as they turn.

ESR study of the molecular orientation and dynamics of stable organic radicals included in the 1‐D organic nanochannels of 2,4,6‐tris‐4‐(chlorophenoxy)‐1,3,5‐triazine

The molecular orientation and dynamics of the organic stable radicals such as 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) or 4-hydroxy-TEMPO (TEMPOL) included in the one-dimensional (1-D) organic nanochannels of 2,4,6-tris-4-(chlorophenoxy)-1,3,5-triazine (CLPOT) were investigated by examining the inclusion compounds (ICs) diluted by the co-inclusion of non-radicals using ESR spectroscopy. Spectral simulation showed that the axial rotation of TEMPO or TEMPOL molecules is excited in the nanochannels with activation energies of 8 and 7 kJ mol(-1) , respectively. The rotation axis was estimated to be tilted towards the principal x direction in the axis system of the g-tensor of the respective radicals. This is quite different from that for similar ICs in the nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP), in which the radicals are axially rotating around the principal axis y of the g-tensor. The difference is attributed to the larger nanospace of the CLPOT nanochannels.

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).

Design of an Organic Zeolite toward the Selective Adsorption of Small Molecules at the Dispersion Corrected Density Functional Theory Level

Tris(o-phenylenedioxy)cyclotriphosphazene (TPP) became the compound of choice to investigate the structural features of organic zeolites and their potential applications as soft materials. A van der Waals crystal of the TPP analogue (host) with the thiophene side fragment tris(3,4-thiophenedioxy)cyclotriphosphazene (TTP) was designed to investigate the selective adsorption among some common gases (guest): methane (CH(4)), carbon dioxide (CO(2)), nitrogen (N(2)), or hydrogen (H(2)). The crystal structure of TTP was modeled by applying minimization methods using the COMPASS (condensed-phase optimized molecular potentials for atomic simulation studies) force field. Interaction energies and structural properties of van der Waals complexes of the crystal of TTP and gas molecules were studied using the dispersion corrected density functional theory (DFT-D). The proper functional and basis set were selected after comparing with benchmark data of the coupled-cluster calculations with singles, doubles, and perturbative triple excitations [CCSD(T)] estimated at the complete basis set (CBS) limit. On the basis of our results, the interaction energy between the host and the guest molecules was predicted in the increasing order of host-H(2) << host-N(2) < host-CH(4) < host-CO(2), suggesting the designed TTP is a good candidate as an organic zeolite for potential fuel storage, hydrogen purification, carbon dioxide removal from the air, as well as safety care in a coal mine.

Preparation and Characterization of Inclusion Compounds Using TEMPOL and an Organic 1-D Nanochannel as a Template

Inclusion of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPOL) radical into an organic one-dimensional (1-D) nanochannels formed in guest-free tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was attempted. The inclusion of TEMPOL molecules adsorbed into the TPP nanochannel and their molecular orientation and dynamics were confirmed by temperature-dependent election spin resonance (ESR) measurements. In the specimens prepared by co-precipitation, the existence of 1-D spin diffusion was suggested from the ESR line shape, but the diffusion was not as effective as in the case of the TPP and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) inclusion compound reported in our previous article. These results imply a new methodology for the preparation of a new organic magnet using TPP as a template.