Toward fluorine-free blue-emitting cationic iridium complexes: to generate emission from the cyclometalating ligands with enhanced triplet energy. Issue 13 (26th February 2016)

• Record Type: Journal Article
• Authors: He, Lei; Wang, Zhen; Duan, Lian; Yang, Chunpeng; Tang, Ruiren; Song, Xiangzhi; Pan, Chunyue
• Is Part Of: Dalton transactions. Volume 45:Issue 13(2016)
• Page Start: 5604
• Page End: 5613
• Publication Date: 2016-02-26
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt04728e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Generating emission from cyclometalating ligands with enhanced triplet energy is an efficient avenue toward fluorine-free blue-emitting cationic iridium complexes. Abstract : A route toward fluorine-free blue-emitting cationic iridium complexes, to generate emission from the cyclometalating ligands with enhanced triplet energy, has been proposed and demonstrated. Attaching electron-donating groups to the pyridine moieties of the ppy-type cyclometalating ligands (Hppy is 2-phenylpyridine) enhances the triplet ( 3 π–π*) energy of the ligand, and the use of electron-rich or non-conjugated ancillary ligands ensures that the emission is generated from the 3 π–π* states of cyclometalating ligands. By this molecular design, [Ir(buoppy)2 (pzpy)]PF6 (1 ) and [Ir(buoppy)2 (bim-cb)]PF6 (2 ) have been developed, with 4-butoxy-2-phenylpyridine (buoppy) as the cyclometalating ligand and electron-rich 2-(1 H -pyrazol-1-yl)pyridine (pzpy) or non-conjugated N-heterocyclic dicarbene (bim-cb) as the ancillary ligands. Complexes1 and2 give emission with major emission peaks around 465 nm, which is among the bluest reported for fluorine-free cationic iridium complexes. For both complexes, the emission is generated from the 3 π–π* states centered on buoppy. For complex1, the charge-transfer (Ir/buoppy → pzpy) state is dominated by non-radiative deactivation and it behaves as a non-radiative deactivation channel for the emissive buoppy-centered 3 π–π* states which lies close to the charge-transfer state in energy. Such a non-radiative deactivation channel is largely suppressed in the rigid matrix, and is eliminated in complex2 with a non-conjugated dicarbene ancillary ligand.