Near-Infrared Absorptive and Emissive Poly(p-phenylene vinylene) Derivative Containing Azobenzene–Boron Complexes

Abstract

Poly­(p-phenylene vinylene) (PPV) is known to be a typical π-conjugated polymer and used as a commodity platform for constructing optoelectronic organic devices because of superior optical and material properties. PPV derivatives generally show a large degree of light absorption and intense emission in the visible region; meanwhile, very few examples have been reported to offer near-infrared (NIR) absorptive and emissive PPV derivatives. In this study, we designed and synthesized a novel PPV derivative, named BAz-PPV, containing boron-fused NN double bond units in the main chain. BAz-PPV showed intense NIR absorption and emission (λabs = 702 nm, λPL = 760 nm, and ΦPL = 2.0% in diluted toluene). This polymer had a narrow energy band gap because of not only extension of main chain π-conjugation over 50 monomer units but also stabilization of the energy level of the lowest unoccupied molecular orbital. Moreover, the polymer shows high stability toward photodegradation and sufficient carrier-transport ability for the applications in organic semiconducting devices. Advantages of the introduction of the NN double bond to main-chain conjugation followed by boron coordination for the development of NIR materials are demonstrated in this manuscript.

Vapochromic Luminescent π‐Conjugated Systems with Reversible Coordination‐Number Control of Hypervalent Tin(IV)‐Fused Azobenzene Complexes

“…[28][29][30] As examples, we discovered cubic silica and boron cluster compounds named polyhedral oligomeric silsesquioxane (POSS) [31,32] and ocarborane, [33,34] respectively, have been applicable to main scaffolds for creating functional materials showing superior luminescence behaviors with high durability or stimuli-responsiveness. We recently reported the series of solid-state luminescent complexes and polymers containing boron-fused azomethine (À C=NÀ ) [35][36][37][38][39] and azo (À N=NÀ ) [40][41][42][43][44] complexes with the tridentate ligands, o-salicylideneaminophenol or 2,2'-dihydroxyazobenzne scaffold, respectively. [45] These materials showed intense emission in the condensed state, and highlyefficient polymer film emission [38] and near-infrared (NIR) absorptive and emissive characteristics [40][41][42]44] were obtained.…”

“…We recently reported the series of solid-state luminescent complexes and polymers containing boron-fused azomethine (À C=NÀ ) [35][36][37][38][39] and azo (À N=NÀ ) [40][41][42][43][44] complexes with the tridentate ligands, o-salicylideneaminophenol or 2,2'-dihydroxyazobenzne scaffold, respectively. [45] These materials showed intense emission in the condensed state, and highlyefficient polymer film emission [38] and near-infrared (NIR) absorptive and emissive characteristics [40][41][42]44] were obtained. It should be emphasized that unique environment-sensitive luminescent properties, such as aggregation-induced emission (AIE), [46,47] crystallization-induced emission enhancement (CIEE), [48] in which enhanced emission can be observed only in aggregation and crystal, respectively.…”

Discovery of Functional Luminescence Properties Based on Flexible and Bendable Boron‐Fused Azomethine/Azobenzene Complexes with O,N,O‐Type Tridentate Ligands

“…Considering that the PPV scaffold usually works as a donor moiety, [64] the opposite electron‐accepting properties of the PAM and PAZ scaffold are of interest and useful for constructing functional π‐conjugated polymers. Furthermore, we found that construction of the PPV‐like structure with alternating copolymerization between BAz and vinylene units achieved NIR absorption and emission although there were no electron‐donating units [65] . Although the wavelengths of absorption and emission of PPV are limitedly from blue to orange region, [66,67] narrow energy gap between FMOs in ground and excited states can be achieved by employing the PAM and PAZ structures.…”

B←N Coordination: From Chemistry to Organic Photovoltaic Materials

“…Recently, an O–B←N‐embedded polymer (80b) analogous to poly(p‐phenylene vinylene) with NIR absorption and were reported. [ 133 ] In comparison with the B‐free polymer 80a, B‐complexed 80b showed significantly a bathochromic absorption maximum (510 vs. 702 nm), lowered HOMO (−5.30 vs. −5.38 eV) and LUMO (−3.23 vs. −3.98 eV), and narrowed bandgap (2.07 vs. 1.60 eV). Moreover, nonfluorescence was observed for 80a, whereas NIR luminescence was found for B‐complexed 80b.…”