Luminescent osmium(ii) bi-1,2,3-triazol-4-yl complexes: photophysical characterisation and application in light-emitting electrochemical cells

Abstract

The series of osmium(ii) complexes [Os(bpy)3-n(btz)n][PF6]2 (bpy = 2,2'-bipyridyl, btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl, n = 0, n = 1, n = 2, n = 3), have been prepared and characterised. The progressive replacement of bpy by btz leads to blue-shifted UV-visible electronic absorption spectra, indicative of btz perturbation of the successively destabilised bpy-centred LUMO. For , a dramatic blue-shift relative to the absorption profile for is observed, indicative of the much higher energy LUMO of the btz ligand over that of bpy, mirroring previously reported data on analogous ruthenium(ii) complexes. Unlike the previously reported ruthenium systems, heteroleptic complexes and display intense emission in the far-red/near-infrared (λmax = 724 and 713 nm respectively in aerated acetonitrile at RT) as a consequence of higher lying, and hence less thermally accessible, (3)MC states. This assertion is supported by ground state DFT calculations which show that the dσ* orbitals of to are destabilised by between 0.60 and 0.79 eV relative to their Ru(ii) analogues. The homoleptic complex appears to display extremely weak room temperature emission, but on cooling to 77 K the complex exhibits highly intense blue emission with λmax 444 nm. As complexes to display room temperature luminescent emission and readily reversible Os(ii)/(iii) redox couples, light-emitting electrochemical cell (LEC) devices were fabricated. All LECs display electroluminescent emission in the deep-red/near-IR (λmax = 695 to 730 nm). Whilst devices based on and show inferior current density and luminance than LECs based on , the device utilising shows the highest external quantum efficiency at 0.3%.

Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes

“…For spectroscopic comparison the complex [Os(tolterpy) 2 ][PF 6 ] 2 (2, tolterpy = 4 -p-tolyl-2,2 :6 ,2 -terpyridine) was also prepared. reported the synthesis and characterization of deep-red/near-IR emissive osmium(II) bitriazolyl (btz) complexes and demonstrated their use in light-emitting electrochemical cells [19]. Of recent and growing interest has been the use of luminescent complexes in biological applications [26][27][28].…”

“…We, and others, have paid particular attention to the use of copper-catalysed coupling of alkynes and azides to form 1,2,3-triazole-based ligands [7][8][9][10] and have investigated the photophysical properties of their resultant complexes. A significant number of reports have appeared detailing the photophysical and photochemical properties of triazole-based complexes of Re(I), Ru(II) and Ir(III) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Examples of triazole-containing complexes of osmium(II)…”

Labilizing the Photoinert: Extraordinarily Facile Photochemical Ligand Ejection in an [Os(N^N)3]2+ Complex

“…We have previously reported the synthesis and characterization of complex 1 as its hexafluorophosphate salt. [12] We noted that on being left to stand in ambient daylight that NMR samples in donor solvents appeared to darken, presumably due to some photochemical decomposition process.T his appeared to be accelerated by irradiation with the 363, 403 and 433 nm mercury emission lines of a2 3W fluorescent lamp or a1mW 405 nm LED.U nder identical conditions only small changes are evident in spectra of [Ru(bpy) 3 ] 2+ whilst there is no evidence of any photolysis for [Os(bpy) 3 ] 2+ (see Supplementary Information). When 1 is dissolved in d 5 -pyridine in an NMR tube and subsequently irradiated for an hour,resonances for an equivalent of free btz are observed to grow-in alongside new resonances for a bisbitriazolyl ligand-loss product (Figure 1a and Scheme 1); singlet resonances are observed at d 8.91 and 6.08 which are assigned to the triazole ring and methylene protons,r espectively of the ligated btz ligands of the product.…”

Low‐Cost, Organic Light‐Emitting Electrochemical Cells with Mass‐Producible Nanoimprinted Substrates Made Using Roll‐to‐Roll Methods

“…The extraction of light with broad-spectrum characteristics demonstrated in this paper and a previous one on OLED [32] suggest that the corrugated substrates could be used for full color and white PLECs without changing the original spectra. [36,[54][55][56][57][58][59] Reducing the exciton-polaron interaction that is commonly observed in LECs and developing high-purity polymer materials will be our next challenge in the effort to realize devices with high stability. It remains to be seen whether LECs can be developed with performance comparable to OLEDs (>100 lm W −1 ), because, to date, efficiency has topped www.advmattechnol.de Adv.…”