Photoinduced Processes in Fluorene‐Bridged Rhenium–Phenothiazine Dyads – Comparison of Electron Transfer Across Fluorene, Phenylene, and Xylene Bridges

Walther, Mathieu E.; Grilj, Jakob; Hanss, David; Vauthey, Eric; Wenger, Oliver S.

doi:10.1002/ejic.201000645

Cited by 30 publications

(25 citation statements)

References 81 publications

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“…One should note that the LCCT state is not charge separated; both the donor and the acceptor orbitals have overlap and thus appreciable 3 (π → π*) character. A number of good examples of charge-separated states have been studied, and they are characterized with shortlived excited states which show electron tunneling through spacer groups 51,52 which are not present in [Re(CO) 3 Cl-(DPA)] + While the SOMOs of the Cl − and py complexes appear almost identical, the HOMO of the former is metal based (not shown), which is consistent with a smaller energy gap between the dπ and the π L orbitals. As can be seen from Figure 12a, the transients of the peaks at 418 and 555 nm persist for longer than depletion of the ground state.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Synthesis, Characterization, and Photophysics of Oxadiazole- and Diphenylaniline-Substituted Re(I) and Cu(I) Complexes

et al. 2013

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Transition-metal complexes of the types [Re(CO)3Cl(NN)], [Re(CO)3py(NN)]+, and [Cu(PPh3)2(NN)]+, where NN = 4,4′-bis(5-phenyl-1,3,4-oxadiazol-2-yl)-2,2′-bipyridine (OX) and 4, 4′-bis(N,N-diphenyl-4-[ethen-1-yl]-aniline)-2,2′-bipyridine (DPA), have been synthesized and characterized. Crystal structures for [Re(CO)3Cl(DPA)] and [Cu(PPh3)2(OX)]BF4 are presented. The crystal structure of the rhenium complex shows a trans arrangement of the ethylene groups, in agreement with density functional theory calculations. The structure of the copper complex displays the planar aromatic nature of the bpy-oxadiazole ligand. Density functional theory modeling of the complexes was supported by comparison of calculated and experimental normalized Raman spectra; the mean absolute deviations of the complexes were <10 >cm-1. The Franck-Condon state was investigated using UV-vis and resonance Raman spectroscopic as well as density functional theory computational techniques. It was shown that the lowest energy absorption peaks are metal to ligand charge transfer and ligand-centered charge transfer for the oxadiazole-and diphenylaniline-substituted bipyridine ligands, respectively. The lowest energy excited states were characterized using transient emission and absorption spectroscopic techniques in conjunction with density functional theory calculations. These showed that the DPA complexes had ligand-centered nonemissive "dark" states with lifetimes ranging from 300 to 2000 ns. The crystal structure of the rhenium complex shows a trans arrangement of the ethylene groups, in agreement with density functional theory calculations. The structure of the copper complex displays the planar aromatic nature of the bpy−oxadiazole ligand. Density functional theory modeling of the complexes was supported by comparison of calculated and experimental normalized Raman spectra; the mean absolute deviations of the complexes were <10 cm −1 . The Franck−Condon state was investigated using UV−vis and resonance Raman spectroscopic as well as density functional theory computational techniques. It was shown that the lowest energy absorption peaks are metal to ligand charge transfer and ligand-centered charge transfer for the oxadiazole-and diphenylaniline-substituted bipyridine ligands, respectively. The lowest energy excited states were characterized using transient emission and absorption spectroscopic techniques in conjunction with density functional theory calculations. These showed that the DPA complexes had ligand-centered nonemissive "dark" states with lifetimes ranging from 300 to 2000 ns.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Synthesis, Characterization, and Photophysics of Oxadiazole- and Diphenylaniline-Substituted Re(I) and Cu(I) Complexes

et al. 2013

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“…A more recent study comparing charge transport in structurally similar bridges is the work of Wenger et al on D-B-A molecules linked by phenylene-based bridges. 25 They investigated hole tunneling in D-B-A systems with a rhenium(I) complex as a hole donor and phenothiazine as a hole acceptor. The donor-acceptor couple was connected either by two phenyls (ph 2 ), two xylene groups (xy 2 ) or a fluorene group (fl 1 ) (see Table 1).…”

Section: Using Structurally Identical Bridgesmentioning

confidence: 99%

Photoinduced charge and energy transfer in molecular wires

2015

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Exploring charge and energy transport in donor-bridge-acceptor systems is an important research field which is essential for the fundamental knowledge necessary to develop future applications. These studies help creating valuable knowledge to respond to today's challenges to develop functionalized molecular systems for artificial photosynthesis, photovoltaics or molecular scale electronics. This tutorial review focuses on photo-induced charge/energy transfer in covalently linked donor-bridge-acceptor (D-B-A) systems. Of utmost importance in such systems is to understand how to control signal transmission, i.e. how fast electrons or excitation energy could be transferred between the donor and acceptor and the role played by the bridge (the "molecular wire"). After a brief description of the electron and energy transfer theory, we aim to give a simple yet accurate picture of the complex role played by the bridge to sustain donor-acceptor electronic communication. Special emphasis is put on understanding bridge energetics and conformational dynamics effects on the distance dependence of the donor-acceptor electronic coupling and transfer rates. Several examples of donor-bridge-acceptor systems from the literature are described as a support to the discussion. Finally, porphyrin-based molecular wires are introduced, and the relationship between their electronic structure and photophysical properties is outlined. In strongly conjugated porphyrin systems, limitations of the existing electron transfer theory to interpret the distance dependence of the transfer rates are also discussed.

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“…Many different molecular bridges have been used to link Ds and As. Typical bridges in DBA systems comprise oligo-phenylenevinylenes (oPVs), [18][19][20][21][22] oligophenyleneethynylenes (oPEs), [23][24][25][26][27][28][29] oligo-fluorenes (oFls), [30][31][32][33] oligo-vinylfluorenes, 34 ladder-OFls, 35 oligothiophenes, [36][37][38] oligo-vinylthiophenes, 39 oligo(ethynylene-10,20-porphyrindiyl-ethynylene)s, 40 oligo-phenylenes, [41][42][43][44][45] and others. 3,46 It is noteworthy that oligoynes [(C≡C) n ] have only been partially studied as bridge units in this context.…”

Section: Introductionmentioning

confidence: 99%

Resonance-Enhanced Charge Delocalization in Carbazole–Oligoyne–Oxadiazole Conjugates

et al. 2020

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There are notably few literature reports of electron donor-acceptor oligoynes although they offer unique opportunities for studying charge transport through 'all-carbon' molecular bridges. In this context, the current study focuses on a series of carbazole-(C≡C) n -2,5-diphenyl-1,3,4-oxadiazoles (n = 1-4) as conjugated π-systems, in general, and explores their photophysical properties, in particular. Contrary to the behavior of typical electron donor-acceptor systems, for these oligoynes the rates of charge recombination after photoexcitation increase with increasing electron donoracceptor distance. To elucidate this unusual performance, detailed photophysical and time-dependent density functional theory investigations were conducted. Significant delocalization of the electron density along the bridge indicates that the bridging states come into resonance with either the electron donor or acceptor, thereby accelerating the charge transfer. Moreover, the calculated bond lengths reveal a reduction in bond length alternation upon photoexcitation, indicating significant cumulenic character of the bridge in the excited state. In short, strong vibronic coupling between the electrondonating N-arylcarbazoles and the electron-accepting 1,3,4-oxadiazoles accelerates the charge recombination as the oligoyne becomes longer.

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Photoinduced Processes in Fluorene‐Bridged Rhenium–Phenothiazine Dyads – Comparison of Electron Transfer Across Fluorene, Phenylene, and Xylene Bridges

Cited by 30 publications

References 81 publications

Synthesis, Characterization, and Photophysics of Oxadiazole- and Diphenylaniline-Substituted Re(I) and Cu(I) Complexes

Synthesis, Characterization, and Photophysics of Oxadiazole- and Diphenylaniline-Substituted Re(I) and Cu(I) Complexes

Photoinduced charge and energy transfer in molecular wires

Resonance-Enhanced Charge Delocalization in Carbazole–Oligoyne–Oxadiazole Conjugates

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