Design, Synthesis and Photophysical Studies of Luminescent Rhodium(III) Complexes in Near‐Infrared Region

Abstract

A series of near-infrared (NIR)-emitting cyclometalated rhodium(III) complexes have been designed, synthesized and characterized. The NIR luminescence has been realized by rational design of strong σ-donor cyclometalating (C^N) ligand with extended π-conjugation structure for decreasing the energy level of intraligand (IL) state. In addition, the investigation of substituents on the benzo[g]quinoxaline moiety as the carbon-donor demonstrated that the luminescence can be further shifted to the red by the introduction of electrondonating thienyl groups. The luminescence maxima of these complexes are ranging from 763 nm to 792 nm with the luminescence quantum yield (Φ lum ) of 0.41 %-0.66 % in dichloromethane solution. This work demonstrates the first example of NIR-phosphorescent rhodium(III) complexes and provides an alternative for diversifying the development of NIR materials.

Aggregation-induced emission of cyclometalated rhodium(iii) and iridium(iii) phenylpyridine complexes with ancillary 1,3-diketones

“…These data are completely consistent with previously reported similar structures. 28,34 In all the complexes, cyclometalated ligands are flat, while β-diketones are slightly nonplanar, with dihedral angles between the aromatic rings and adjacent six-membered metallacycle lying within 7.7(5) ( Ir4 )–26.61(13)° ( Rh2 ), which are governed most likely by packing effects.…”

“…A judicious selection of cyclometalating ligands and the use of 1,3-diketones as the ancillary ligands allowed access to bis-cyclometalated Rh( iii ) complexes exhibiting enhanced luminescence and high efficiency in OLEDs, 32 which stimulated studies aimed at developing cyclometalated Rh( iii ) complexes suitable for application as visible 33 and NIR 34 emitters and anticancer agents. 35,36 Moreover, there has been a renewed interest in studying rhodium( iii ) cyclometalates together with their iridium( iii ) analogues.…”

“…Despite promising optical characteristics of the cyclometalated Rh( iii ) complexes containing ancillary 1,3-diketones, 32–34 only few diketones have been exploited. Hence, there is an urgent need for a study describing the influence of the β-diketone nature on the optical and redox properties of the corresponding rhodium( iii ) complexes and their ability to show AIE.…”

N^N^C-Cyclometalated rhodium(iii) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity

“…These reactions do not require inert atmosphere which is often used for the synthesis or rhodium complexes. [94][95][96][97][98] The identity and purity of the complexes was established by elemental analysis, IR spectroscopy, X-ray single crystal and powder diffraction (ESI, Fig. S5-S8, S15-S20, S23 and S24 †).…”

“…In this manuscript we focus on the investigation of the coordination behaviour of HL 2,5 and HL 2,6 toward rhodium(III) chloride and on unveiling the impact of isomerism on structures and properties. Our particular interest to rhodium complexes stems partly from our experience in rhodium chemistry [82][83][84] and partly from appealing properties this metal shows in the C-H bond activation and catalysis, [85][86][87][88][89][90][91] photochemistry [92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] and bioinorganic chemistry. Along with the synthesis of HL 2,5 and HL 2,6 and their rhodium(III) complexes [RhL 2,5 (Solv)Cl 2 ]•nEtOH and [RhL 2,6 (Solv)Cl 2 ]•nEtOH, here we report the impact of isomerism on molecular and supramolecular structures of these compounds, on the photophysical properties of the rhodium(III) complexes and on the cytotoxic activity of the ligands and complexes.…”