Spectroscopic Studies of Phosphazene Polymers Containing Photoluminescent Metal Complexes

Abstract

A series of small phosphazene ligands with pendant 6‐phenyl‐2,2′‐bipyridyl moieties, namely L1 [N3P3(OPh)5(OPhbpyPh)], L2 [N3P3(biph)2(OPhbpyPh)2], L3 [N3P3(tBubiph)2(OPhbpyPh)2], L4 [N3P3(biph)2(OPhbpyPh)Cl] and L5 [N3P3(biph)2(OPhbpyPh)(OPh)] [OPhbpyPh = 4‐(4‐phenoxy)‐6‐phenyl‐2,2′‐bipyridine, OPh = phenoxy, biph = 2,2′‐oxybiphenyl and tBubiph = 4,4′‐di‐tert‐butyl‐2,2′‐oxybiphenyl], have been used to synthesise the new cyclometallated palladium(II) and platinum(II) complexes [(L1‐H)PdCl], [(L1‐H)PtCl], [(L1‐H)(PdCl)2], [(L3‐H)(PdCl)2], [(L4‐H)PtCl], [(L5‐H)PtCl] and the rhenium(I) complex [L5Re(CO)3Cl]. Single‐crystal X‐ray diffraction analysis was performed on the free ligand L2 and the palladium complexes [(L1‐H)PdCl] and [(L3‐H)(PdCl)2]. In both PdII complexes, the metal centre lies in a distorted square‐planar geometry with an “N2CCl” donor set confirming the cyclopalladation. The ligand pendant arms are involved in intermolecular stacking interactions with adjacent molecules. A polyphosphazene (L6) with 4‐tert‐butylphenoxy (OtBuPh) and the potential donor OPhbpyPh as pendant groups was prepared and used to synthesise metallopolymers with ReI and PtII. Spectroscopic and computational studies were conducted to compare the discrete complexes with the polymers with similar metal pendants as well as to model compounds in the literature. By using UV/Vis and resonance Raman spectroscopic techniques it was found that very few deviations from known metal chromophores exist for both the triphosphazene‐ and polyphosphazene‐based complexes. The transient resonance Raman spectra of the PtII complexes revealed a ligand radical anion signature associated with the N2C unit.

Toward an Iron(II) Spin-Crossover Grafted Phosphazene Polymer

“…The difficulties associated with the process are consistent with reports in the literature . Trifluoroethoxy was not selected as a pendant group because Ainscough et al previously demonstrated that it has a tendency to displace aromatic substituents. Despite the residual P–Cl units, the polymers remained soluble to aqueous workup and remained stable for several months.…”

“…These properties have often proven to be useful in the development of ligands because coordinating substituents (pyridines, phosphines, nitriles, etc.) can be attached to either the cyclotriphosphazene (CTP) to form discrete metal complexes − or polyphosphazene (PP) metallopolymers. ,− Previously reported polymers produced by Ainscough et al proved that the substitution of phosphazenes with fluorophores had little effect on their physical behavior …”

Multifunctional Block Copolymer: Where Polymetallic and Polyelectrolyte Blocks Meet

“…Among the large class of polyelectrolytes, phosphonium-based polyelectrolytes have attracted increasing interest due to their unique properties such as high thermal stability, flame retardancy, and biocompatibility, leading to potential applications in molecular recognition, , humidity sensors, − and biocides . Coexistence of phosphorus centers and metallic centers in macromolecules − or the utilization of coordination chemistry in binding the lone pair of electrons on the phosphorus to coordinate metal ions has been known for decades. ,− The Ragogna Group has utilized photopolymerization methods as a strategy to generate charged, mechanically robust, highly cross-linked phosphonium containing networks with a high degree of surface tunability . By utilizing salt metathesis chemistry of the polyelectrolyte, an anionic gold cluster [(Au 25 L 18 ) − ] was incorporated onto the network ( 2 ; Figure ).…”

Terpyridine and 2,6-di(1H-pyrazol-1-yl)pyridine substituted cyclotri- and polyphosphazene ruthenium(II) complexes: Chemical and physical behaviour

“…The ruthenium-bpp-terpy complexes (17 and 18) show little difference in T g relative to that of the parent metal-free polymer for which T g = 36°C. Given the poor agreement with the elemental analysis, a typical issue with post-polymerisation modification [1], other techniques such as electronic absorbance and resonance Raman were employed to determine the formation of the complexes, an approach proven to be effective previously [2,23].…”