Synthesis of π-Conjugated Polymers Containing Phosphole Units in the Main Chain by Reaction of an Organometallic Polymer Having a Titanacyclopentadiene Unit

Abstract

A regioregular organometallic polymer possessing titanacyclopentadiene units in the main chain, which was obtained by the reaction of terminal diyne and a low-valent titanium complex, was subjected to the reaction with dichlorophosphines to give π-conjugated polymers with phosphole or phosphole oxide units in the main chain. For example, a phenylphospholecontaining polymer was obtained in 76% yield by the reaction with dichlorophenylphosphine, whose number-average molecular weight (M n ) and molecular weight distribution (M w /M n ) were estimated to be 6100 and 1.9, respectively, by GPC. The polymer was found to have an extended π-conjugated system, and its lowest unoccupied molecular orbital (LUMO) energy level was remarkably low (−3.28 eV) as supported by its UV−vis absorption spectrum and cyclic voltammetric (CV) analysis. Also, the polymer exhibits orange photoluminescence with an emission maximum (E max ) of 595 nm and a quantum yield (Φ) of 0.10.π-Conjugated polymers are applicable to various functional materials such as organic light-emitting diodes (OLEDs), organic solar cells (OSCs), organic field effect transistors (OFETs), and chemosensors. 2 Among them, those possessing heteroatoms are expected to exhibit unique features originated from the nature of the heteroatoms. For example, polymers containing heteroles of the group 16 elements such as thiophene and selenophene are known to serve as electronrich (electron-donor) materials. In cases of those containing the group 15 elements, quite a few examples of pyrrole-containing polymers have been reported which likewise exhibit electronrich properties. Accordingly, these polymers are also applicable to p-type semiconducting materials for the electronic applications. Although polymers containing heteroles with the heavier group 15 elements such as phosphole are expected to exhibit electron-accepting properties due to the σ*−π* orbital interactions between the group 15 elements and butadiene unit in each heterole unit, 3 only a few synthetic studies on phosphole-containing polymers have been reported.Tilley et al. first reported the synthesis of a phospholecontaining polymer by the reaction of a zirconacyclopentadiene-containing organometallic polymer with dichlorophenylphosphine. 4 However, the resulting phosphole-containing polymer did not exhibit sufficient π-conjugated properties due to the lack of the regioregularity of the precursor polymer. Chujo et al. reported the synthesis of regioregular π-conjugated phosphole-containing polymers by the Sonogashira−Hagihara coupling of an aromatic diyne and phosphole-containing aryl dihalides that were prepared by the transformation of regioregular zirconacyclopentadiene intermediates. 5 Likewise, Imahori et al. described the synthesis of phosphole-or phosphole oxide-containing π-conjugated polymers by use of the Stille coupling technique. 6 The electrochemical polymerization of a phosphole-containing monomer was also described by Reáu et al. 7 The polymers obtained by these methods exhibited the effective extens...

Redox chemistry of π-extended tellurophenes

“…All reagents and dehydrated solvents were from commercial source and used without further purification unless otherwise noted. Diethyl ether solution of isopropylmagnesium chloride (Pr i MgCl, 1.0 M) was prepared by the previously reported procedure 37 . Titanium(IV) isopropoxide [Ti(OPr i ) 4 ] was obtained from Sigma-Aldrich and distilled under reduced pressure.…”

Arsole‐Containing π‐Conjugated Polymer by the Post‐Element‐Transformation Technique

“…The polymer ( 6 ) exhibited an orange photoluminescence (PL) in CHCl 3 with an emission maximum ( E max ) and the quantum yield ( Φ ) of 600 nm and 0.05, respectively. The optical properties of 6 are very close to those of a phosphole‐containing polymer ( λ max =522 nm, λ onset =620 nm, E max =594 nm, Φ =0.10), which was prepared by reaction of the same organotitanium polymer ( 5 ) . This result indicates that the electronic character of the arsole ring is almost comparable to that of the phosphole ring.…”

“…The energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were estimated to be −5.43 and −3.24 eV, respectively, from the onsets for oxidation and reduction signals in the CV analysis. The HOMO and LUMO energy levels of 6 were very close to those of the phosphole‐containing polymer (HOMO=−5.35 eV, LUMO=−3.28 eV) . Namely, the arsole‐containing polymer ( 6 ) also exhibits both electron‐donating and ‐accepting‐properties.…”

The Dawn of Functional Organoarsenic Chemistry

“…[93] To mita et al have developedageneralm ethod to effectively produce heteroatom-containing polymers. [94][95][96][97] The reaction of diethynyl monomers with al ow-valent titanium complex generates regioregular titanacyclopentadiene-containing polymer 41,a nd subsequentlyt he addition of adequate electrophiles gives the corresponding heterole-containingpolymers. Involvement of 4 in this protocol leads to arsole polymer 42.…”