Phosphole polymers

Polymers incorporating phosphole subunits are still very rare. However, the pioneering work described in this section shows that such macromolecules are... 

Biphenyl-phosphole copolymer 65 is isolated as an air-stable and soluble powder exhibiting a rather high molecular weight (Mw = 16 000 Mn = 6200) according to gel permeation chromatographic (GPC) analysis. Although multinuclear magnetic resonance spectroscopy and elemental analysis support the proposed structure, the presence of a small number of diene defects is very likely. Polymer 65... 

It is likely that the P atoms of the as-synthesized film obtained from the o3,X3-derivative 35 are protonated, at least partially, since the electropolymerization process generates protons [15a]. The polymers prepared with neutral phospholes... 

In conclusion, for the most part, polymers incorporating phosphole units are still rare. However, the work described above demonstrates that they are accessible via a number of diverse synthetic routes including organometallic coupling or electropolymerization processes. The general property-structure relationships established with well-defined small oligomers have been shown to extend to the corresponding polymeric materials. 

Dibenzophosphole A was in fact the first type of phosphole to be prepared [9], but it has only very recently been used as a building block for the preparation of jr-conjugated systems. In this regard, polymer 70 is obtained with a high polydis-persity (Mn = 5 X 102 Mw = 6.2 X 103) by Ni-catalyzed homo-coupling of derivative 69 (Scheme 4.20) [52]. The presence of o3-P centers, which are potential donor sites for the Ni catalyst, does not prevent C-C bond formation. This macromolecule is photoluminescent in the solid state (2em = 516 nm), a property of potential interest for the development of OLEDs [52]. 

Table TDDFT(B3LYP) calculated excitation energies (eV) for oligo(cyclopentadiene)s, oligo(pyrrole)s, oligo(phosphole)s (Ph) ollgo(thlophene)s (Th)n, and the corresponding polymers (DFT HOMO-LUMO gaps in parentheses)...

Note that insoluble mixed thiophene-phosphole conjugated polymers have been characterized by MAS NMR spectroscopy <2006AGE6152>. The chemical shifts recorded in the solid state for polymers having m -phosphole, a -phosphole sulfide, or phosphole-Au(l) moieties compare well with those recorded in solution for the corresponding molecular monomers. 

The reaction of l,4-diethynyl-2,5-dioctyloxybenzene with a low-valent Ti(ll) complex generated from Ti(iv) isopropoxide affords the titanacyclopentadiene-containing polymer 179 having a regioregular backbone (Scheme 57) . This polymer can be converted into the corresponding phosphole-based macromolecule 180 upon addition of dichlorophenylphosphine. 

A variety of different functionalities were introduced into this class of polymers by conversion of the zirconacyclopentadiene units (Scheme 2.35).205-206 The reaction of polymer 124 with dimethylaceteylene dicarboxylate 125 in the presence of CuCl/LiCl produced the phenylene-based polymer 126 as an example. Polymers containing thiophene and phosphole units 127 were also prepared. 

The Zr polymers 201 are not just of intrinsic interest but they also permit chemical modification reactions in which the Zr atom is replaced.This allows for the introduction of diene, thiophene, phosphole, and aromatic functionalities, to yield novel vr-conjugated organic polymers 202-205 with controlled structures and electronic properties (Scheme 18). 

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