Highly Fluorinated Dithieno[3,2-b:2′,3′-d]phospholes with Stabilized LUMO Levels

Abstract

A series of dithieno[3,2-b:2′,3′-d]phospholes with a perfluorophenyl substituent at the phosphorus center has been synthesized. Further cross-coupling reactions with additional fluorinated phenyl groups afforded extended conjugated materials with different substitution patterns. Investigation of the optoelectronic properties of the materials revealed smaller highest occupied molecular orbital (HOMO)−lowest unoccupied molecular orbital (LUMO) gaps for the extended materials that were also confirmed by theoretical density functional theory (DFT) calculations. These further indicated that the LUMO levels experience a more significant drop in energy than the respective HOMO levels. This fact can be attributed to the strongly electron-withdrawing nature of the fluoroaryls. In addition, the absolute energies of the frontier orbitals depend on the position of the fluoro substituents in the terminal aryl groups, with meta-positioned fluoro atoms having the strongest effect. Electrochemical investigations as well as theoretical calculations toward the electron affinity of the extended, highly fluorinated dithienophospholes revealed promising features that may prove useful for application as n-type semiconductors in corresponding organic field-effect transistors (OFETs).

A fluoroaryl substituent with spectator function: Reactivity and structures of cyclic and acyclic HF4C6-substituted phosphanes

“…The filtrate is dried in vacuum yielding almost quantitatively 2 as a white crystalline solid (76 mg, 94%). Crystals suitable for X-ray diffraction were obtained by recrystallization from chloroform-d 1 4.5. Synthesis of (tetrakis(2,3,5,6-tetrafluorophenyl)-tetraphosphetane), 5…”

“…After recrystallization from chloroform colorless crystals suitable for X-ray diffraction are obtained (50 mg, 47%). 1 Compound 5 is also obtained by reaction of 4 (237 mg, 0.9 mmol) with PMe 3 (1.5 ml, 1 M in hexane) in the presence of Zn dust (ca. 100 mg, 1.5 mmol) in 3 ml CDCl 3 .…”

“…Phosphorus containing compounds with electron withdrawing moieties attracted considerable attention in the last decade [1,2]. Electron deficient groups are known to influence both electronic and optical properties of phosphorus containing compounds [3][4][5][6][7].…”

“…Tuning of different phosphorus based ligands has been studied with respect to hydroformylation reactions [13]. Electron deficient units are essential for the synthesis of molecular ntype conducting materials and different attempts have been made to incorporate C 6 F 5 groups into the backbone of phosphorus derived oligomers and polymers [1]. Diphosphenes bearing electron withdrawing groups are known to have reduced reactivity [14].…”

2,3,5,6‐Tetrafluoro‐p‐phenylenebis(phosphanes) – Preparation and Structure of an Electron‐Poor P–RF–P Linker

“…[18,19] The incorporation of C 6 F 5 groups into phospholes was achieved by Baumgartner and co-workers, and they explained their stabilizing effect on the LUMO level by means of DFT calculations. [20] …”