2021
DOI: 10.3390/molecules27010232
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pH-Responsive N^C-Cyclometalated Iridium(III) Complexes: Synthesis, Photophysical Properties, Computational Results, and Bioimaging Application

Abstract: Herein we report four [Ir(N^C)2(L^L)]n+, n = 0,1 complexes (1–4) containing cyclometallated N^C ligand (N^CH = 1-phenyl-2-(4-(pyridin-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole) and various bidentate L^L ligands (picolinic acid (1), 2,2′-bipyridine (2), [2,2′-bipyridine]-4,4′-dicarboxylic acid (3), and sodium 4,4′,4″,4‴-(1,2-phenylenebis(phosphanetriyl))tetrabenzenesulfonate (4). The N^CH ligand precursor and iridium complexes 1–4 were synthesized in good yield and characterized using chemical analysis, ESI m… Show more

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Cited by 9 publications
(10 citation statements)
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“…The electronic absorption spectra of mononuclear species Re(NN1)−Re(NN3), Ir(NC2) 2 (NN1), and Ir(NC2) 2 (NN2) (Figure S26) are reminiscent of those found for the previously studied tricarbonylrhenium(I) diimine emitters 47,52−54 and bisorthometalated iridium(III) diimine complexes, 49,50,55,56 with the metal centers bound to closely analogous chelating S26) expectedly display a superposition of the spectra of the corresponding mononuclear complexes. According to the results of DFT calculations, the long-wavelength region of the spectrum of the binuclear homometallic rhenium Re 2 (NN2) complex is similar to the corresponding spectrum of mononuclear analogues and displays mainly the rhenium(I)-to-phenanthroline (S 0 → S 2 ) and rhenium(I)-to-imidazole-quinoline (S 0 → S 1 ) 1 MLCT character (Tables S11−S14 and Figures S32 and S33) with a noticeable admixture of 1 LLCT transitions from Cl − and CO to the aromatic system of the bridging ligand.…”
Section: ■ Introductionmentioning
confidence: 52%
See 1 more Smart Citation
“…The electronic absorption spectra of mononuclear species Re(NN1)−Re(NN3), Ir(NC2) 2 (NN1), and Ir(NC2) 2 (NN2) (Figure S26) are reminiscent of those found for the previously studied tricarbonylrhenium(I) diimine emitters 47,52−54 and bisorthometalated iridium(III) diimine complexes, 49,50,55,56 with the metal centers bound to closely analogous chelating S26) expectedly display a superposition of the spectra of the corresponding mononuclear complexes. According to the results of DFT calculations, the long-wavelength region of the spectrum of the binuclear homometallic rhenium Re 2 (NN2) complex is similar to the corresponding spectrum of mononuclear analogues and displays mainly the rhenium(I)-to-phenanthroline (S 0 → S 2 ) and rhenium(I)-to-imidazole-quinoline (S 0 → S 1 ) 1 MLCT character (Tables S11−S14 and Figures S32 and S33) with a noticeable admixture of 1 LLCT transitions from Cl − and CO to the aromatic system of the bridging ligand.…”
Section: ■ Introductionmentioning
confidence: 52%
“…The mononuclear iridium complexes Ir(NC2) 2 (NN1) and Ir(NC2) 2 (NN2) containing the {Ir(NC2) 2 } moiety coordinated to different diimine chelating functions display rather strong orange/red and yellow phosphorescence (Table 1). The nature of emissive excited states in both cases is typical for these types of iridium [(NC) 2 Ir(NN)] + complexes 49,50,55 and may be assigned to a mixture of 3 MLCT/ 3 LLCT/ 3 LC emissive transitions localized at the corresponding diimine fragments of the bridging ligands (Tables S39 and S43 and Figure S48).…”
Section: ■ Introductionmentioning
confidence: 95%
“…Ligands in the coordination sphere of these complexes form a pseudo-octahedral environment at the iridium ion, with the nitrogen and carbon atoms of the N^C ligands disposed in trans - and cis -positions, respectively. This structural pattern is typical for complexes of this sort; bond angles and lengths in the coordination octahedron are not exceptional and fall in the range characteristic for the cationic [Ir(N^C) 2 (N^N)] + complexes [ 26 , 27 , 28 ]. The observed deviations from the ideal octahedral geometry around the iridium center are due to short bite angles of the N^C ligands, which are about 80° in these structures.…”
Section: Resultsmentioning
confidence: 83%
“…The study of luminescent materials based on transition metal complexes is motivated by a number of importantapplications in fields such as photocatalysis [ 1 , 2 , 3 ], sensing and bioimaging [ 4 , 5 , 6 , 7 ], and optoelectronic devices [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. In the field of OLEDs (organic light emitting diodes), phosphorescent metal complexes are of particular interest due to their ability to harvest all generated excitons through the availability of excited triplet states.…”
Section: Introductionmentioning
confidence: 99%
“…The necessary intersystem crossing (ISC) is facilitated through efficient spin-orbit coupling (SOC) associated with the heavy metal centres, which also boosts the phosphorescent relaxation [ 8 , 10 , 17 ]. Typical phosphorescent (triplet) emitters are based on metal cations such as Ir(III), Ru(II), and Pt(II) [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. While the d 6 metal centres of Ir(III) and Ru(II) adopt an octahedral coordination environment, the d 8 configured Pt(II) complexes and the less frequently used Pd(II) and Au(III) coordination compounds adopt square planar geometries with open coordination sites in the axial positions [ 16 , 18 ].…”
Section: Introductionmentioning
confidence: 99%