Tuning Emission of AIE-Active Organometallic Ir(III) Complexes by Simple Modulation of Strength of Donor/Acceptor on Ancillary Ligands

Abstract

A new design strategy to tune emission color of aggregation-induced emission (AIE) Ir(III) complexes, by simply adjusting the strength of donor/acceptor on ancillary ligands, is reported. Herein, all studied Ir(III) complexes employ 1-(2,4difluorophenyl)-1H-pyrazole as cyclometalated ligands but different pyridine-1,2,4triazolyl moieties as ancillary ligands that were modified with carbazole end-capped alkyl groups, in which pyridine-1,2,4-triazolyl moieties and functionalized carbazole act as donor and acceptor units, respectively. The experimental and theoretical results clearly reveal the intrinsic relationship between structures and emission behaviors. Enhancing the ability of donor and/or acceptor leads to red-shifted emission and vice versa. In addition, one of the designed dyes exhibits the reversible and significant mechanochromic luminescent behavior thanks to its efficient AIE characteristic and structural modification, providing a feasible way to design multifunctional materials.

Ancillary Ligand Effects on Red‐Emitting Cyclometalated Iridium Complexes

“…Therefore, tuning the emission color and excited‐state dynamics by altering the ancillary ligand structure in heteroleptic iridium complexes with known cyclometalating ligands could be an easier, more efficient, and more expeditious approach. There are several well‐known strategies that use ancillary ligands to tune the emission and/or photochemical properties of cyclometalated iridium complexes over a wide range, including ancillary ligands that are chromophoric and completely change the nature of the excited state or those that have subtler effects on the frontier orbitals and excited states . Our group has recently reported the synthesis and characterization of red‐emitting bis‐cyclometalated Ir III complexes with high efficiency, good device performance, and excellent color purity by using β‐ketoiminate (acNac), β‐diketiminate (NacNac), and smaller bite‐angle N′N ‐diisopropylbenzamidinate (dipba) as the ancillary ligands .…”

“…There are several well-known strategies that use ancillary ligandst o tune the emission and/orp hotochemical properties of cyclometalated iridium complexes over aw ide range, including ancillary ligandst hat are chromophoric and completely change the nature of the excited state or those that have subtler effects on the frontier orbitalsa nd excited states. [20,21,[33][34][35][36] Our group has recently reported the synthesis and characterization of red-emittingb is-cyclometalated Ir III complexes with high efficiency,g ood device performance, and excellent color purity by using b-ketoiminate (acNac), b-diketiminate (NacNac), and smaller bite-angle N'N-diisopropylbenzamidinate (dipba) as the ancillary ligands. [37] We were able to show that the different L^X ligands influence the electronic structures of bis-cyclometalated iridium complexes, in some cases inducing significant redshiftso ft he emission maxima, and in other cases enhancing phosphorescence quantum yields relative to the corresponding acetylacetonate (acac) analogues or the homoleptic tris-cyclometalated complexes featuring the same cyclometalating ligands.…”

Novel Multifunctional Hybrid Molecules Constructed from β‐Carboline and Naphthalene Anhydride: Aggregation, Deaggregation and Fluorescence Detection

“…In this work, we designed and synthesized two hybrid molecules ( CA‐1 , CA‐2 ) by linking carbazole with a longer‐wavelength naphthalene anhydride derivative and studied their photophysical properties. Though carbazole derivatives present excellent AIE properties, [28] the shorter emission wavelength limits their further potential application. In addition, as a natural product alkaloid, β ‐carboline with similar chemical structure to carbazole molecule was linked to naphthalene anhydride molecules by click reaction to obtain two hybrid molecules ( CA‐3 , CA‐4 ).…”

A TPE–benzothiazole piezochromic and acidichromic molecular switch with high solid state luminescent efficiency

“…Fluorescent materials which can change their color upon exposure to different environmental stimuli, such as light, 1 acids/bases, 2-4 electricity, 5 mechanical force [6][7][8] etc., are of great importance for their potential applications in sensors, memory devices and switches. To achieve the above applications, strong emission of uorescent materials in the solid state is required.…”