Synthesis of Monodisperse Platinum Acetylide Oligomers End-Capped with Naphthalene Diimide Units

Keller, Julia; Schanze, Kirk S.

doi:10.1021/om900195p

Cited by 41 publications

(45 citation statements)

References 72 publications

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“…The naphthalene diimide acceptor was used due to its relatively low reduction potential, combined with relatively high singlet and triplet energies, which preclude OPE to NDI energy transfer from competing with electron transfer. [26][27] In addition, the NDI anion radical (NDI -. ) has distinct absorption features which are easily identified by visible transient absorption spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Effect of Conjugation Length on Photoinduced Charge Transfer in π-Conjugated Oligomer-Acceptor Dyads

et al. 2017

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A series of π-conjugated oligomer-acceptor dyads were synthesized that feature oligo(phenylene ethynylene) (OPE) conjugated backbones end-capped with a naphthalene diimide (NDI) acceptor. The OPE segments vary in length from 4 to 8 phenylene ethynene units (PEn-NDI, where n = 4, 6 and 8). Fluorescence and transient absorption spectroscopy reveals that intramolecular OPE → NDI charge transfer dominates the deactivation of excited states of the PEn-NDI oligomers. Both charge separation (CS) and charge recombination (CR) are strongly exothermic (ΔG ∼ -1.1 and ΔG ∼ -2.0 eV), and the driving forces do not vary much across the series because the oxidation and reduction potentials and singlet energies of the OPEs do not vary much with their length. Bimolecular photoinduced charge transfer between model OPEs that do not contain the NDI acceptors with methyl viologen was studied, and the results reveal that the absorption of the cation radical state (OPE) remains approximately constant (λ ∼ 575 nm) regardless of oligomer length. This finding suggests that the cation radical (polaron) of the OPE is relatively localized, effectively occupying a confined segment of n ≤ 4 repeat units in the longer oligomers. Photoinduced intramolecular electron transfer dynamics in the PEn-NDI series was investigated by UV-visible femtosecond transient absorption spectroscopy with visible and mid-infrared probes. Charge separation occurs on the 1-10 ps time scale with the rates decreasing slightly with increased oligomer length (β ∼ 0.15 Å). The rate for charge-recombination decreases in the sequence PE4-NDI > PE6-NDI ∼ PE8-NDI. The discontinuous distance dependence in the rate for charge recombination may be related to the spatial localization of the positive polaron state in the longer oligomers.

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Section: Introductionmentioning

confidence: 99%

Effect of Conjugation Length on Photoinduced Charge Transfer in π-Conjugated Oligomer-Acceptor Dyads

et al. 2017

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“…Preparing metallopolymers requires either appending metal ions to an already existing polymer backbone or incorporating them into the repeating unit directly . Conjugated platinum(II) acetylide oligomers/polymers, studied extensively by Schanze and co-workers [33][34][35][36][37][38][39][40], are hallmark examples of incorporating metal ions into the propagating repeat unit. The platinum ions engender photophysical properties that are challenging or impossible to replicate by organic polymers alone.…”

Section: Introductionmentioning

confidence: 99%

Expanding iClick to group 9 metals

et al. 2016

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“…As reported recently, we synthesized a series of monodisperse oligomers (Pt n NDI 2 , where n = 2, 3, 6, and 10 shown in Figure 1) end capped with naphthalene diimide (NDI) units that serve as traps for triplet excitons (via charge separation) and negative polarons (by charge shift from the chain to the end group). 52 Here, we report the results of fast time-scale pumpÀprobe spectroscopy and pulse radiolysis experiments on the dynamics of triplet exciton and negative polaron transport along the chains. This work shows that triplet excitons and negative polarons, initially localized on the PtÀacetylide chain, rapidly transport to the chain ends and become trapped by charge separation or charge shift to NDI.…”

Section: ' Introductionmentioning

confidence: 99%

Negative Polaron and Triplet Exciton Diffusion in Organometallic “Molecular Wires”

et al. 2011

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The dynamics of negative polaron and triplet exciton transport within a series of monodisperse platinum (Pt) acetylide oligomers is reported. The oligomers consist of Pt-acetylide repeats, [PtL(2)-C≡C-Ph-C≡C-](n) (where L = PBu(3) and Ph = 1,4-phenylene, n = 2, 3, 6, and 10), capped with naphthalene diimide (NDI) end groups. The Pt-acetylide segments are electro- and photoactive, and they serve as conduits for transport of electrons (negative polaron) and triplet excitons. The NDI end groups are relatively strong acceptors, serving as traps for the carriers. Negative polaron transport is studied by using pulse radiolysis/transient absorption at the Brookhaven National Laboratory Laser-Electron Accelerator Facility (LEAF). Electrons are rapidly attached to the oligomers, with some fraction initially residing upon the Pt-acetylide chains. The dynamics of transport are resolved by monitoring the spectral changes associated with transfer of electrons from the chain to the NDI end group. Triplet exciton transport is studied by femtosecond-picosecond transient absorption spectroscopy. Near-UV excitation leads to rapid production of triplet excitons localized on the Pt-acetylide chains. The excitons transport to the chain ends, where they are annihilated by charge separation with the NDI end group. The dynamics of triplet transport are resolved by transient absorption spectroscopy, taking advantage of the changes in spectra associated with decay of the triplet exciton and rise of the charge-separated state. The results indicate that negative polarons and excitons are transported rapidly, on average moving distances of ~3 nm in less than 200 ps. Analysis of the dynamics suggests diffusive transport by a site-to-site hopping mechanism with hopping times of ~27 ps for triplets and <10 ps for electrons.

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Synthesis of Monodisperse Platinum Acetylide Oligomers End-Capped with Naphthalene Diimide Units

Cited by 41 publications

References 72 publications

Effect of Conjugation Length on Photoinduced Charge Transfer in π-Conjugated Oligomer-Acceptor Dyads

Effect of Conjugation Length on Photoinduced Charge Transfer in π-Conjugated Oligomer-Acceptor Dyads

Expanding iClick to group 9 metals

Negative Polaron and Triplet Exciton Diffusion in Organometallic “Molecular Wires”

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