A Convenient Approach To Synthesize o‐Carborane‐Functionalized Phosphorescent Iridium(III) Complexes for Endocellular Hypoxia Imaging

Abstract

The structure-property relationship of carborane-modified iridium(III) complexes was investigated. Firstly, an efficient approach for the synthesis of o-carborane-containing pyridine ligands a-f in high yields was developed by utilizing stable and cheap B H (Et N) as the starting material. By using these ligands, iridium(III) complexes I-VII were efficiently prepared. In combination with DFT calculations, the photophysical and electrochemical properties of these complexes were studied. The hydrophilic nido-o-carborane-based iridium(III) complex VII showed the highest phosphorescence efficiency (abs. ϕP =0.48) among known water-soluble homoleptic cyclometalated iridium(III) complexes and long emission lifetime (τ=1.24 μs) in aqueous solution. Both of them are sensitive to O , and thus endocellular hypoxia imaging of complex VII was realized by time-resolved luminescence imaging (TRLI). This is the first example of applying TRLI in endocellular oxygen detection with a water-soluble nido-carborane functionalized iridium(III) complex.

Using highly emissive and environmentally sensitive o-carborane-functionalized metallophosphors to monitor mitochondrial polarity

“…The novel o -carborane-modified N⁁N ligands ( 1a–1j ) ( Schemes 1 and S1 † ) were synthesized in high yields by using commercially available B 10 H 10 (Et 4 N) 2 which is cheap, stable and non-toxic. 9 f Through the change of the 2-R substituent or the substitution site of the carboranyl unit at bipyridine, 11 , 12 two series of complexes 2a–2e and 3a–3e were prepared by the reactions of the dimeric [(C⁁N) 2 Ir(μ-Cl) 2 Ir(C⁁N) 2 ] and the corresponding carborane-functionalized ligands ( 1a–1j ) ( Schemes 1 and 2 ). Complex 4 containing two carboranyl motifs was also synthesized in order to further tune the photophysical properties.…”

Azaheterocyclic Derivatives of ortho-Carborane: Synthetic Strategies and Application Opportunities

“…Treatment of 122 with diethyl sulfide and sulfuric acid was shown to form an active bis(ligand) derivative B 10 H 12 (Et 2 S) 2 123, which reacted readily with Short Review Syn thesis substituted acetylenes, including pyridine-containing alkynes 124 (Scheme 42). 51 On the basis of this modified synthetic approach, new carborane-containing ligands 127 were obtained in high yields (55-75%) via the cross-coupling reaction of compound 123 with pyridines 126 (Scheme 43).…”

“…It was also established that incorporation of the carboranyl moiety enhanced oxidation potentials and reduced the HOMO energy levels of the iridium(III) complexes through stabilization of the HOMO due to the presence of the carborane fragment, exhibiting the electronwithdrawing effect. 51…”

Boron‐Functionalized Phosphorescent Iridium(III) Complexes

“…In particular, OLEDs containing 21 showed deep red emission [CIE = (0.693, 0.290)], with maximum EQE of 3.8 % and power efficiency of 0.6 lm W -1 . Yan, Zhao, et al [35] introduced the o-Cb group at the m-position to the Ir-N bond and achieved Ir III complexes 23a-e (Scheme 3). The photophysical properties of 23a-e were investigated in detail ( Table 2).…”

“…Yan, Zhao, et al introduced the o ‐Cb group at the m ‐position to the Ir–N bond and achieved Ir III complexes 23a – e (Scheme ). The photophysical properties of 23a – e were investigated in detail (Table ).…”