Development of the P‐Arylation of Dithieno[3,2‐b : 2’,3’‐d]phosphole with Aryl Iodonium Salts

A highly blue luminescent, P,P-diphenyl-dithieno[3,2-b : 2’,3’-d]phospholium with a quantum yield of unity was obtained by P-arylation of the trivalent congener with an aryliodonium reagent with a bulky hexafluorophosphonium counter ion. The functional properties of the diphenylphospholium species were found to be noticeably distinct from its P-methyl,P-phenyl congener.

Abstract

P-Arylation of dithieno[3,2-b : 2’,3’-d]phosphole toward cationic phenyl phospholium species using diaryliodonium reagents was explored. Multiple conditions were tested to optimize the reaction, including variation of solvent, temperature, stoichiometry, time, and aryliodonium species employed. Initial use of diphenyliodonium chloride led to an unexpected dithienophosphole Cu(I) chloride complex that was characterized crystallographically. Alternatively, the use of diphenyliodonium hexafluorophosphate in ethanol under microwave conditions led to the successful isolation of the P-arylated target. The phenyl dithienophospholium species exhibits blue luminescence with a quantum yield of 100 % in solution that is considerably red-shifted in the solid state. The photophysics and solid-state organization of the new species were compared with those of a related methyl congener, showing distinct differences that are assigned to the nature of the carbon-based substituent at the phosphorus center, which was also confirmed by DFT calculations, and the supramolecular organization in the solid state.

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