Phosphorus‐Based Heteropentacenes: Efficiently Tunable Materials for Organic n‐Type Semiconductors

Abstract

Benzo-condensed dithieno[3,2-b:2',3'-d]phospholes have been synthesized that allow convenient tuning of properties that are essential for application as semiconductor materials in organic field-effect transistor (OFET) devices. The versatile reactivity of the trivalent phosphorus atom in these heteropentacenes provides access to a series of materials that show different photophysical properties, significantly different organization in the solid state, and distinctly different electrochemical properties that can be achieved by simple chemical modifications. The materials show strong photoluminescence in solution and in the solid state that depends on the electronic nature of the phosphorus center. Electrochemical studies revealed that the phosphorus atom intrinsically furnishes materials with n-channel or ambipolar behavior, also depending on its electronic nature. The experimental data were verified by DFT quantum chemical calculations and suggest that the phosphorus-based heteropentacenes could be excellent candidates for n-channel OFET semiconductor materials.

3,7‐Diazadibenzophosphole Oxide: A Phosphorus‐Bridged Viologen Analogue with Significantly Lowered Reduction Threshold

“…[3] The high practical value of MV 2+ is based on its pronounced electron-acceptor character and the change between intense colors (purple and orange) for the radical cation (MVC + ), and the neutral species (MV), respectively, that make the reduction event(s) easily detectable by optical spectroscopy or even the naked eye. [1a] In the context of systematic studies on phosphoruscontaining p-conjugated materials for organic electronics, our group [4] and others [5] could confirm the highly tunable, favorable electron-acceptor features that are attributable to the electronic nature of phosphorus. Recently we have extended our studies toward p-conjugated phospholes with pyridine units as integral part of the scaffold and were able to establish the highly functional nature, as well as the pronounced electron-accepting features of these systems, particularly for the phosphole oxides.…”

Organic Electron Acceptors Comprising a Dicyanomethylene‐Bridged Acridophosphine Scaffold: The Impact of the Heteroatom

“…Compound 1 was subjected to a microwave‐assisted Knoevenagel condensation with malononitrile to afford 2 as a yellow microcrystalline solid (Scheme ). To tune the electronic properties, further derivatization of trivalent phosphorus in 2 was carried out . Treatment of 2 with elemental sulfur provided phosphine sulfide 3 (97 % yield), oxidation with H 2 O 2 gave phosphine oxide 4 (98 % yield), and methylation with methyl triflate furnished cation 5 (98 % yield).…”

“…To tune the electronic properties,f urtherd erivatization of trivalent phosphorus in 2 was carriedo ut. [14] Treatment of 2 with elemental sulfurp rovided phosphine sulfide 3 (97 %y ield), oxidation with H 2 O 2 gave phosphine oxide 4 (98 %y ield), and methylation with methyl triflatef urnished cation 5 (98 %y ield). All dicyanomethylenebridged compounds 2-5 were obtained as air-stable,c olorless solids which were soluble in common organic solvents.…”

MPHT‐Promoted Bromocyclization of ortho‐Substituted Arylalkynes: Application to the Synthesis of 2‐Substituted 3‐Bromobenzofurans and ‐Benzo[b]thiophenes

“…of MPHT ( Table 2, Entries 1 and 2). We were pleased to observe the quantitative formation of bis(3-bromobenzofuran) 4a and bis(3-bromobenzothiophene) 4b, which were used as starting materials for the synthesis of benzannulated phospholes, [15] dibenzothienopyrroles, [16] dithienosiloles, [17] and functionalized phenanthrenes [18] of physical interest. Unsymmetrical diyne 3c reacted cleanly with MPHT to afford expected heterocycle 4c, again with excellent yield (Table 2, Entry 3).…”