Cyclometalated N-heterocyclic carbene iridium(iii) complexes with naphthalimide chromophores: a novel class of phosphorescent heteroleptic compounds. Issue 10 (12th February 2018)

• Record Type: Journal Article
• Authors: Lanoë, Pierre-Henri; Chan, Jonny; Groué, Antoine; Gontard, Geoffrey; Jutand, Anny; Rager, Marie-Noelle; Armaroli, Nicola; Monti, Filippo; Barbieri, Andrea; Amouri, Hani
• Is Part Of: Dalton transactions. Volume 47:Issue 10(2018)
• Page Start: 3440
• Page End: 3451
• Publication Date: 2018-02-12
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt04369d
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A novel class of phosphorescent heteroleptic iridium cyclometalated NHC complexes containing organic and inorganic chromophores has been reported. Abstract : A series of cyclometalated N-heterocyclic carbene complexes of the general formula [Ir(C^N)2 (C^C:)] has been prepared. Two sets of compounds were designed, those where (C^C:) represents a bidentate naphthalimide-substituted imidazolylidene ligand and (C^N) = ppy (3a ), F2ppy (4a ), bzq (5a ) and those where (C^C:) represents a naphthalimide-substituted benzimidazolylidene ligand and (C^N) = ppy (3b ), F2ppy (4b ), bzq (5b ). The naphthalimide-imidazole and naphthalimide-benzimidazole ligands1a, b and the related imidazolium and benzimidazolium salts2a, b were also prepared and fully characterized. The N-heterocyclic carbene Ir(iii ) complexes have been characterized by NMR spectroscopy, cyclic voltammetry and elemental analysis. Moreover, the molecular structures of one imidazolium salt and four Ir(iii ) complexes were determined by single-crystal X-ray diffraction. The structures provide us with valuable information, most notably the orientation of the naphthalimide chromophore with respect to the N-heterocyclic carbene moiety. All compounds are luminescent at room temperature and in a frozen solvent at 77 K, exhibiting a broad emission band that extends beyond 700 nm. The presence of the naphthalimide moiety changes the character of the lowest excited state from 3 MLCT to 3 LC, as corroborated by DFT and TD-DFT calculations. Remarkably, replacing imidazole with a benzimidazole unit improves the quantum yields of these compounds by decreasing the k nr values which is an important feature for optimized emission performance. These studies provide valuable insights about a novel class of N-heterocyclic carbene-based luminescent complexes containing organic chromophores and affording metal complexes emitting across the red–NIR range.