Characterizing the Solvated Structure of Photoexcited [Os(terpy)2]2+ with X-ray Transient Absorption Spectroscopy and DFT Calculations

Zhang, Xiaoyi; Pápai, Mátyás; Møller, Klaus Braagaard; Zhang, Jianxin; Canton, Sophie E.

doi:10.3390/molecules21020235

Cited by 11 publications

(15 citation statements)

References 33 publications

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“…Curiously, unlike in the case of 2, the T1 state of 1 undergoes a puckering like distortion of the btzpy ligand on which the unpaired electron density is localized. Such distortions have been observed, however, in theoretical calculations of the T1 states of bis(tridentate) ruthenium(II) cyclometalated complexes [48] and [Os(terpy)2] 2+ [49].…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2016

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Abstract:The complex [Os(btzpy) 2 ][PF 6 ] 2 (1, btzpy = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine) has been prepared and characterised. Complex 1 exhibits phosphorescence (λ em = 595 nm, τ = 937 ns, φ em = 9.3% in degassed acetonitrile) in contrast to its known ruthenium(II) analogue, which is non-emissive at room temperature. The complex undergoes significant oxygen-dependent quenching of emission with a 43-fold reduction in luminescence intensity between degassed and aerated acetonitrile solutions, indicating its potential to act as a singlet oxygen sensitiser. Complex 1 underwent counterion metathesis to yield [Os(btzpy) 2 ]Cl 2 (1 Cl ), which shows near identical optical absorption and emission spectra to those of 1. Direct measurement of the yield of singlet oxygen sensitised by 1 Cl was carried out (φ ( 1 O 2 ) = 57%) for air equilibrated acetonitrile solutions. On the basis of these photophysical properties, preliminary cellular uptake and luminescence microscopy imaging studies were conducted. Complex 1 Cl readily entered the cancer cell lines HeLa and U2OS with mitochondrial staining seen and intense emission allowing for imaging at concentrations as low as 1 µM. Long-term toxicity results indicate low toxicity in HeLa cells with LD50 >100 µM. Osmium(II) complexes based on 1 therefore present an excellent platform for the development of novel theranostic agents for anticancer activity.

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Section: Resultsmentioning

confidence: 99%

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

et al. 2016

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“…28,29 Finally, complexes with a 5d 6 central atom ground state electron configuration as well N or C in the first coordination sphere display only minor changes in their local structure (∼0.02 Å) upon photoexcitation and the X-ray absorption spectra in the near-edge region (XANES) became sensitive to the electronic structure only. Os photosensitizers were the first examples in this category 30,31 and the interest for Ir has increased since then. [32][33][34] Here we will demonstrate the use of pump-probe XAS on a novel organometallic Ir complex with chromenopyridinone ligands [Ir(Chp) 2 (dtbbpy)]PF 6 , where Chp is 3-methyl-6-oxo-6H-isochromeno[4,3-b]pyridin-10-ide and dtbbpy is 4,4′-di-tert-butyl-2,2′-bipyridine ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Pump—probe XAS investigation of the triplet state of an Ir photosensitizer with chromenopyridinone ligands

Smolentsev

Vliet

Azzaroli

et al. 2018

Photochem Photobiol Sci

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The triplet excited state of a new Ir-based photosensitizer with two chromenopyridinone and one bipyridine-based ligands has been studied by pump-probe X-ray absorption near edge structure (XANES) spectroscopy coupled with DFT calculations. The excited state has a lifetime of 0.5 μs in acetonitrile and is characterized by very small changes of the local atomic structure with an average metal-ligand bond length change of less than 0.01 Å. DFT-based calculations allow the interpretation of the XANES in the energy range of ∼50 eV around the absorption edge. The observed transient XANES signal arises from an additional metal-centered Ir 5d vacancy in the excited state which appears as a result of electron transfer from the metal to the ligand. The overall energy shift of the excited state spectrum originates from the shift of 2p and unoccupied states induced by screening effects. The approach for the analysis of time-resolved spectra of 5d metal complexes is quite general and can also be used if excited and ground state structures are significantly different.

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“…The trend can be ascribed to the effective oxidation of the ring orbital and to the closer approach of the fullerene, with a Cu-C now of 2.533 Å as predicted by DFT (Figure 10a Upcoming TR-XAS experiments with higher S/N will be attempted next, in order to ascertain experimentally the predicted structural changes of a few picometers (Table S6), a task which remains demanding in the sub-millimolar regime. 70,71 It should be noted that the transient change in covalency revealed by the optical pump-X-ray probe measurement could also be affected by the coupling between the unpaired metal electrons and the ring electrons. In any non-D 4h structure, the spatial overlap between 3dx2-y 2 and a 2u () is significant enough for the spins to couple antiferromagentically, a phenomenon recognized as conceptually undistinguishable from bond formation.…”

Section: P-c 60mentioning

confidence: 99%

Elucidating the Ultrafast Dynamics of Photoinduced Charge Separation in Metalloporphyrin-Fullerene Dyads Across the Electromagnetic Spectrum

et al. 2016

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Metalloporphyrins are prominent building blocks in the synthetic toolbox of advanced photodriven molecular devices. When the central ion is paramagnetic, the relaxation pathways within the manifold of excited states are highly intricate so that unravelling the intramolecular energy and electron transfer processes is usually a very complex task. This fact is critically hampering the development of applications based on the enhanced coupling offered by the electronic exchange interaction. In this work, the dynamics of charge separation in a copper porphyrin-fullerene are studied with several complementary spectroscopic tools across the electromagnetic spectrum (from near infra-red to X-ray wavelengths), each of them providing specific diagnostics. Correlating the various rates clearly demonstrates that the lifetime of the photoinduced charge-separated state exceeds by about 10 fold that of the isolated photoexcited Cu II porphyrin. As revealed by the spectral modifications in the XANES region, this stabilization is accompanied by a transient change in covalency around the Cu II center, which is induced by an enhanced interaction with the C 60 moiety. This experimental finding is further confirmed by state-of-the art calculations using DFT and TD-DFT including dispersion effects that explain the electrostatic and structural origins of this interaction, as the Cu II P cation becomes ruffled and approaches closer to the fullerene in the charge-separated state. From a methodological point of view, these results exemplify the potential of multielectron excitation features in transient X-ray spectra as future diagnostics of sub-femtosecond electronic dynamics. From a practical point of view, this work is paving the way for elucidating out-ofequilibrium electron transfer events coupled to magnetic interaction processes on their intrinsic time-scales.

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Characterizing the Solvated Structure of Photoexcited [Os(terpy)2]2+ with X-ray Transient Absorption Spectroscopy and DFT Calculations

Cited by 11 publications

References 33 publications

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

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

Pump—probe XAS investigation of the triplet state of an Ir photosensitizer with chromenopyridinone ligands

Elucidating the Ultrafast Dynamics of Photoinduced Charge Separation in Metalloporphyrin-Fullerene Dyads Across the Electromagnetic Spectrum

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