17997-47-6Relevant articles and documents
High molecular weight CuII coordination polymers and their characterisation by electrospray mass spectrometry (ESMS)
Nierengarten, Helene,Rojo, Javier,Leize, Emmanuelle,Lehn, Jean-Marie,Van Dorsselaer, Alain
, p. 573 - 579 (2002)
The ligands L and ligand L* self-assemble with CuII in different solvents to give a mixture of coordination polymers. These artificial nanostructures have been characterised with the help of ESMS, the only analytical tool that allows their unambiguous characterisation. Kinetic and thermodynamic ESMS studies have excluded the possibility that these compounds form aggregates during the ES process.
Synthesis, photophysics, and reverse saturable absorption of 7-(benzothiazol-2-yl)-9,9-di(2-ethylhexyl)-9: H -fluoren-2-yl tethered [Ir(bpy)(ppy)2]PF6 and Ir(ppy)3 complexes (bpy = 2,2′-bipyridine, ppy = 2-phenylpyridine)
Li, Zhongjing,Li, Hui,Gifford, Brendan J.,Peiris, Wadumesthrige D. N.,Kilina, Svetlana,Sun, Wenfang
, p. 41214 - 41218 (2016)
We report the synthesis, photophysics, and reverse saturable absorption of five iridium(iii) complexes 1-5 with 7-(benzothiazol-2-yl)-9,9-di(2-ethylhexyl)-9H-fluoren-2-yl (BTF) pendant attached to the 2-phenylpyridine ligand (1: [Ir(bpy)(BTF-ppy)2]PF6; 2: [Ir(bpy)(BTF - ppy)2]PF6; 3: Ir(ppy)2(BTF-ppy); 4: Ir(ppy)(BTF-ppy)2; 5: (BTF-ppy)3, where bpy = 2,2′-bipyridine and ppy = 2-phenylpyridine). The effects of the extended π-conjugation of the ppy ligand and the increased number of BTF-ppy ligand, as well as the effects of neutral complex vs. cationic complex were evaluated. All complexes exhibit predominantly ligand-localized 1π,π? transitions below 430 nm and charge-transfer transitions between 430 and 550 nm. They all emit at room temperature and at 77 K, mainly from the metal-to-ligand charge transfer (3MLCT)/ligand-to-ligand charge transfer (3LLCT) states for 1 and 2, and from the BTF-ppy ligand-centered 3π,π? excited states with significant contributions from the 3MLCT states for 3-5. The triplet excited states of 1-5 also manifest broad transient absorption (TA) in the visible to the near-IR spectral region. The electronic absorption, emission, and ns transient absorption are all red-shifted by extending the π-conjugation of the ppy ligand or increasing the number of BTF-ppy ligand. The energies of the lowest singlet and triplet excited states of the neutral complex 4 are lowered compared to those of its cationic counterpart 1; while the transient absorbing triplet excited state of 4 is much longer lived than that of 1. These complexes all exhibit strong reverse saturable absorption (RSA) for ns laser pulses at 532 nm, with a trend of 5 ex/σ0) at 532 nm with the triplet quantum yield also playing a role for complexes 3-5. It appears that the increased number of BTF-ppy ligand reduces the RSA of the neutral complexes while the increased π-conjugation of the ppy ligand in the cationic complexes improves the RSA. However, the neutral complex 4 exhibits a weaker RSA at 532 nm than its cationic counterpart 1.
A Near-Infrared-II Emissive Chromium(III) Complex
Jiménez, Juan-Ramón,Pfund, Bj?rn,Piguet, Claude,Prescimone, Alessandro,Sinha, Narayan,Wenger, Oliver S.
, p. 23722 - 23728 (2021)
The combination of π-donating amido with π-accepting pyridine coordination units in a tridentate chelate ligand causes a strong nephelauxetic effect in a homoleptic CrIII complex, which shifts its luminescence to the NIR-II spectral range. Previously explored CrIII polypyridine complexes typically emit between 727 and 778 nm (in the red to NIR-I spectral region), and ligand design strategies have so far concentrated on optimizing the ligand field strength. The present work takes a fundamentally different approach and focusses on increasing metal–ligand bond covalence to shift the ruby-like 2E emission of CrIII to 1067 nm at 77 K.
The kinetics and mechanism of interconversion within a system of [Fe2L 3]4+helicates and [Fe4L 6]8+cages
Al-Fayaad, Hydar A.,Arachchige, Kasun S. A.,Brock, Aidan J.,Clegg, Jack K.,Luis, Ena T.,McMurtrie, John C.,Micallef, Aaron S.,Siddique, Rashid G.,Thoburn, John D.
supporting information, p. 4918 - 4921 (2021/05/26)
Nature builds simple molecules into highly complex assemblies, which are involved in all fundamental processes of life. Some of the most intriguing biological assemblies are those that can be precisely reconfigured to achieve different functions using the same building blocks. Understanding the reconfiguration of synthetic self-assembled systems will allow us to better understand the complexity of proteins and design useful artificial chemical systems. Here we have prepared a relatively simple system in which two distinct self-assembled structures, a [Fe2L3]4+ helicate and a [Fe4L6]8+ cage that are formed from the same precursors, coexist at equilibrium. We have measured the rates of interconversion of these two species and propose a mechanism for the transformation.
Observation of an inversion in photophysical tuning in a systematic study of luminescent triazole-based osmium(II) complexes
Scattergood, Paul A.,Roberts, James,Omar, Salem A.E.,Elliott, Paul I.P.
, p. 8607 - 8621 (2019/08/21)
In a systematic survey of luminescent bis(terdentate) osmium(II) complexes, a tipping point involving a reversal in photophysical tuning is observed whereby increasing stabilization of the ligand-based lowest unoccupied molecular orbital (LUMO) results in a blue shift in the optical absorption and emission bands. The complexes [Os(N^N′^N″)2]2+ [N^N′^N″ = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine (Os1), 2,6-bis(1-benzyl-1,2,3-triazol-4-yl)pyrazine (Os2), 6-(1-benzyl-1,2,3-triazol-4-yl)-2,2′-bipyridyl (Os3), 2-(pyrid-2-yl)-6-(1-benzyl-1,2,3-triazol-4-yl)pyrazine (Os4), 2-(pyrazin-2-yl)-6-(1-benzyl-1,2,3-triazol-4-yl)pyridine (Os5), and 6-(1-benzyl-1,2,3-triazol-4-yl)-2,2′-bipyrazinyl (Os6)] have been prepared and characterized, and all complexes display phosphorescence ranging from the orange to near-IR regions of the spectrum. Replacement of the central pyridine in the ligands of Os1 by the more π-accepting pyrazine in Os2 results in a 55 nm red shift in the triplet metal-to-ligand charge-transfer-based emission band, while a larger red shift of 107 nm is observed for the replacement of one of the triazole donors in the ligands of Os1 by a second pyridine ring in Os3 (λemmax = 702 nm). Interestingly, replacement of the central pyridine ring in the ligands of Os3 by pyrazine (Os4, λemmax = 702 nm) fails to result in a further red shift in the emission band. Reversal of the relative positions of the pyridine and pyrazine donors in Os5 (λemmax = 733 nm) compared to Os4 does indeed result in the expected red shift in the emission with respect to that for Os3 based on the increased π-acceptor character of the ligands present. However, an inversion in emission tuning is observed for Os6, in which the incorporation of a second pyrazine donor in the ligand architecture results in a blue shift in the optical absorption and emission maxima (λemmax = 710 nm). Electrochemical studies reveal that while incorporating pyrazine in the ligands indeed results in an expected anodic shift in the first reduction potential through stabilization of the ligand-based LUMO, there is also a concomitant anodic shift in the OsII/OsIII-based oxidation potential. This stabilization of the metal-based highest occupied molecular orbital (HOMO) thus nullifies the effect of stabilization of the LUMO in Os4 compared to Os3, resulting in these complexes having coincident emission maxima. For Os6, stabilization of the HOMO through the incorporation of two pyrazine donors in the ligand structure now exceeds stabilization of the LUMO, resulting in a larger HOMO?LUMO gap and a counterintuitive blue shift in the optical properties in comparison with those of Os5. While it is known that the replacement of ligands (e.g., replacing bipyridyl with bipyrazinyl) can result in a larger HOMO?LUMO energy gap through greater stabilization of the HOMO, these results importantly allow us to capture the tipping point at which this inversion in photophysical tuning occurs. This therefore enables us to explore the limits available in emission tuning with a relatively simple and minimalist ligand structure.
