Electronic structure of the phosphonitrilic trimer?role ofd orbitals in chemical bonding

Ferris, Kim F.; Friedman, Paul; Friedrich, Donald M.

doi:10.1002/qua.560340824

Cited by 40 publications

(20 citation statements)

References 21 publications

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“…The nature of phosphorus-nitrogen chemical bonding in these systems has been addressed previously and refined in recent work involving ab initio electronic structure calculations of the phosphonitrilic trimer [1]. This work confirmed the "islands-of-delocalization" model which limits pielectron delocalization to a three-atom center (N-P-N) owing to the symmetries of the contributing nitrogen 2p and phosphorus 3d atomic orbitals.…”

Section: Introductionsupporting

confidence: 65%

“…Therefore, the polarizability of localized -R2P=N-moieties is also perturbed by substituent electronegativity. The model accounts for the observed extension of optical transmission to shorter wavelengths [1]. Here, the lowest energy allowed electronic transition is between pi-bonding and piantibonding states and occurs deep in the ultraviolet owing to the restricted pi-conjugation.…”

Section: Discussionmentioning

confidence: 98%

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Design, Characterization, and Optical Properties of Phosphazene-Based Polymers

Samuels

1989

MRS Proc.

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Physical properties intrinsic to linear inorganic polymer systems can be modified through replacement of chemical groups external to the chain backbone. This substitution also perturbs chemical bonding along the chain which can further influence polymer properties. Several phosphazene polymers deposited as thin dielectric films exhibit extended ultraviolet transmission. Second harmonic generation (SHG) has been observed in these polymers as well as in cyclic polymer precursors. The relative magnitude of SHG is found to correlate both with the nature of the substitutional group and molecular conformation. Influence of these parameters on substrate-film adhesion and measured optical properties is discussed in terms of substitutional group electronegativity, and electronic charge localization in the polymer chain which is probed using molecular spectroscopic techniques.

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Section: Introductionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 98%

Design, Characterization, and Optical Properties of Phosphazene-Based Polymers

Samuels

1989

MRS Proc.

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“…[17][18][19][20][21] These investigations were also sparked by the special electronic structure of the phosphazene rings. [11,13,16,22,23] In the halogen-substituted P 3 N 3 X 6 cyclophosphazenes the basicity of the ring nitrogen atom is very low. Therefore, little is known about the complexing abilities of the P 3 N 3 X 6 halophosphazenes.…”

Section: Introductionmentioning

confidence: 99%

Silver Complexes of Cyclic Hexachlorotriphosphazene

Gonsior

Antonijevic

Krossing

2006

Chemistry A European J

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The first solid-state structures of complexed P3N3X6 (X = halogen) are reported for X = Cl. The compounds were obtained from P3N3Cl6 and Ag[Al(OR)4] salts in CH2Cl2/CS2 solution. The very weakly coordinating anion with R = C(CF3)3 led to the salt Ag(P3N3Cl6)2+[Al(OR)4]- (1), but the more strongly coordinating anion with R' = C(CH3)(CF3)2 gave the molecular adduct (P3N3Cl6)AgAl(OR')4 (3). Crystals of [Ag(CH2Cl2)(P3N3Cl6)2]+[Al(OR)4]- (2), in which Ag+ is coordinated by two phosphazene and one CH2Cl2 ligands, were isolated from CH2Cl2 solution. The three compounds were characterized by their X-ray structures, and 1 and 3 also by NMR and vibrational spectroscopy. Solution and solid-state 31P NMR investigations in combination with quantum chemically calculated chemical shifts show that the 31P NMR shifts of free and silver-coordinated P3N3Cl6 differ by less than 3 ppm and indicate a very weakly bound P3N3Cl6 ligand in 1. The experimental silver ion affinity (SIA) of the phosphazene ligand was derived from the solid-state structure of 3. The SIA shows that (PNCl2)3 is only a slightly stronger Lewis base than P4 and CH2Cl2, while other ligands such as S8, P4S3, toluene, and 1,2-Cl2C2H4 are far stronger ligands towards the silver cation. The energetics of the complexes were assessed with inclusion of entropic, thermal, and solvation contributions (MP2/TZVPP, COSMO). The formation of the cations in 1, 2, and 3 was calculated to be exergonic by delta(r)G(degrees)(CH2Cl2) = -97, -107, and -27 kJ mol(-1), respectively. All prepared complexes are thermally stable; formation of P3N3Cl5+ and AgCl was not observed, even at 60 degrees C in an ultrasonic bath. Therefore, the formation of P3N3Cl5+ was investigated by quantum chemical calculations. Other possible reaction pathways that could lead to the successful preparation of P3N3X5+ salts were defined.

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“…The CTP ring itself is also non-aromatic [22]. The charge localization is evident in the orbital contours shown in Fig.…”

Section: The Electronic Structure Of Some Star Polymer Coresmentioning

confidence: 90%

“…The next two highest occupied orbitals (#82, #81) are attributed to the in-plane P-N bonding involving the inclusion of the P d-orbital and the N p-orbital. The in-plane P-N bonding serves to stabilize the ring planarity despite the lack of aromaticity [22,23]. The steric inaccessibility of these electrons (Fig.…”

Section: The Electronic Structure Of Some Star Polymer Coresmentioning

confidence: 99%

Perfluoropolyether Boundary Lubricants Based on the Star Architecture

2018

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Star PFPE (perfluoropolyether) polymers based on an aromatic benzene core and a non-aromatic cyclotriphosphazene (CTP) core are investigated as boundary lubricant films on rigid magnetic media. The effect of the benzene and CTP cores on head-disk spacing are measured by the changes in the acoustic emission signal as a function of head-disk spacing at similar lubricant film thicknesses. The earlier head-disk contact observed with the CTP core is attributed in part to its larger size perpendicular to the plane of the disk surface. The adhesion of the benzene and CTP cores to the underlying carbon film is investigated by ab initio quantum chemistry. The nonaromatic nature of the CTP ring and the lack of steric accessibility to the CTP core nitrogen atoms prevent good adhesive interactions with the underlying carbon film. Conversely, the π-electrons of aromatic benzene create a quadrupole moment in the direction perpendicular to the plane of the benzene that can interact with the underlying carbon surface and hence provide weak adhesion. Electron-withdrawing and-donating substituents on the benzene ring can be used to exert a "push-pull" effect on the π-electrons to alter the strength of the intermolecular interactions to specific functional groups of the underlying carbon surface. These effects are visualized by mapping the electrostatic potential of the benzene core as a function of electron-withdrawing and-donating substituents and computing model dimer optimized geometries and intermolecular interaction energies. Finally, the thermal stability of the star PFPE polymers are quantified by measuring the evaporation rate of thin films (11 Å) as a function of time at the HDD temperature (~ 60°C). Thermogravimetric analyses (TGA) of the neat polymers also provide direction for improvement of the synthetic lubricants.

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Electronic structure of the phosphonitrilic trimer?role ofd orbitals in chemical bonding

Cited by 40 publications

References 21 publications

Design, Characterization, and Optical Properties of Phosphazene-Based Polymers

Design, Characterization, and Optical Properties of Phosphazene-Based Polymers

Silver Complexes of Cyclic Hexachlorotriphosphazene

Perfluoropolyether Boundary Lubricants Based on the Star Architecture

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