Synthesis, characterization and photo-physical studies of naphthalamide-based Ir(III) complexes

Abstract

Interest in tuning the emission towards deep-red (DR) and near-infrared (NIR) regions is enhanced due to their fascinating applications in the field of organic light-emitting diodes (OLEDs), night-vision display and bio-imaging. In this regard, Naphthalimide based bidentate chromophoric ligand (L1, NIPy, 2‑butyl‑6-(pyridin-2-yl)-1H-benzo[de]isoquinoline-1,3(2H)‑dione) was utilized to prepare the DR emitting Ir(III) complexes [Ir(L1)2(L2)] (1) and [Ir(L1)2(L3)] (2) where L2 = 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine and L3 = 1-(4-fluorophenyl)-3-methyl-1H-3λ4-imidazole). Complexes have been characterized by various analytical and spectroscopic methods, and 2 was further confirmed by a single crystal X-ray diffraction method. Strong intermolecular π···π interactions between the naphthalamide units in complex 2 lead to the formation of a multi-dimensional framework. These complexes show emissions in the range of 650–700 nm at room temperature, which extends up to the near-infra-red region (800 nm). The photophysical studies were supported by DFT and TD-DFT calculations. These types of naphthalimide-based Ir(III) complexes tend to show emissions in the NIR region which has potential applications in the field of photodynamic therapy and OLEDs.