A Simple Design for Strongly Emissive Sky-Blue Phosphorescent Neutral Rhenium Complexes: Synthesis, Photophysics, and Electroluminescent Devices

Abstract

A simple design strategy for a new class of stable, vacuum-sublimable, and strongly emissive sky-blue neutral phosphorescent Re(I) phenanthroline complexes {Re(R 2 phen)(CO) 3 [CNB(C 6 F 5 ) 3 ]} is reported. These complexes show intense bluish green emission in CH 2 Cl 2 solution with the highest emission quantum yield and bluest emission ever reported for the neutral Re(I) diimine complexes. In the solid state, they display sky-blue emission. The electroluminescent properties of devices containing these complexes have also been investigated.

Strongly Phosphorescent Neutral Rhenium(I) Isocyanoborato Complexes: Synthesis, Characterization, and Photophysical, Electrochemical, and Computational Studies

“…, which are in the typical range of the isocyanoborato complexes [8][9][10] and lower than that observed in MeCNB(C 6 F 5 ) 3 (2367 cm À1 ) [12] owing to the p-back-bonding interaction.…”

“…This work further corroborated our earlier postulation that the incorporation of the strong p-accepting isocyanoborate ligands to cationic luminophores is an effective strategy to develop neutral phosphorescent materials with improved quantum efficiency and blue-shifted emission energy. [8] It also illustrated the capability of fine-tuning the emission properties of these complexes through the modifications of the substituents on isocyanoborate ligands. It is anticipated that these complexes are also potentially useful for OLED device applications, as illustrated in our earlier work.…”

“…Complexes {Re(CO) 3 (N^N) [CNB(C 6 F 5 ) 3 ]} (1 a-6 a, N^N= diimine ligand) and [Re(CO) 3 (phen)(CNBCl 3 )] (3 c) were prepared in moderate yields from the Lewis acid-base reactions between the cyano precursor complexes with B(C 6 F 5 ) 3 and BCl 3 , respectively, in dichloro-methane. [8,9] When the stable tetraphenyl borate salt and its substituted phenyl derivatives such as NaBPh 4 , KB(C 6 H 4 Cl) 4 and NaB [C 6 H 3 (CF 3 ) 2 ] 4 are available, the corresponding isocyanoborato complexes can be obtained by the reactions of the cyano precursor complexes with the respective borate salts in acidified methanolic solution. [10] These reactions are illustrated in the preparation of [Re(CO) 3 (N^N)(CNBPh 3 )] (1 b-4 b) and [Re(CO) 3 (phen)(CNBR 3 )] [3 d: R= C 6 H 4 Cl; 3 e: R= C 6 H 3 (CF 3 ) 2 ].…”

“…[14] The CN and NÀB distances are in the range of 1.14-1.19 and 1.54-1.59 , respectively, which are in the typical ranges (CN: 1.132-1.174 , NÀB: 1.548-1.618 ) reported in other isocyanoborato transition-metal complexes. [8][9][10] UV/Vis absorption and emission properties…”

“…Regarding our work on isocyano rhenium(I) diimine luminophores, [7] we have demonstrated the use of anionic isocyano tris(pentafluorophenyl)borate ligand in the development of strongly sky-blue phosphorescent chargeneutral rhenium(I) complexes, which are stable for vacuum sublimation and suitable for electroluminescent device application. [8] To design phosphorescent materials from these isocyanoborato complexes, it is crucial to understand their electronic properties as well as their photophysics. To provide insights and elucidate these properties and their structural correlation, herein we report the detailed syntheses, characterizations, photophysics, electrochemistry, and computational study of a new series of neutral rhenium(I) diimine complexes with various isocyanoborate and diimine ligands of diverse electronic and steric nature.…”