Dynamic dimer copper coordination redox shuttles

•Copper complexes form dimers or monomers depending on metal oxidation states•Upon single of two dimers, these undergo disproportionation•Reduction Cu(II) to Cu(I) is highly energetically unfavorable•The stability the monomer reduces charge recombination in solar cells A new generation hybrid using low-cost, Earth-abundant materials can transform energy sector. The majority progress toward this goal has come from improving light-absorbing materials. Charge transfer issues remain a barrier widespread adoption technology, and challenge that article addresses. We developed copper tetradentate ligands, which tetrahedral dimeric structures with planar monomeric Cu(II). Despite fact their are significantly diverse, reorganization remarkably low. dimer’s 2-electron process yields monomers, thus stabilizing both states. Because unfavored, processes dye-sensitized become largely inhibited. dynamic dimer system represents efficient redox mediators for molecular devices. Conventional based coordination electron through change state center. However, kinetics offset preferred states when preorganized ligands constrain sphere. In contrast, we report here copper(II/I) couples, wherein extent oxidation/reduction centers dictates formation complexes: (Cu(I))2 transitions bis(thiazole/pyrrole)-bipyridine stabilize unique systems. offer viable two-electron mechanism develop inhibited rapid transport. Density functional theory calculations reveal inner energies single-electron as low 0.27 eV, marking superior systems over liquid potentially solid-state electrolytes. Redox organic inorganic used biological donors acceptors processes.1Hathaway B.J. Billing D.E. electronic properties stereochemistry mono-nuclear copper(II) ion.Coord. Chem. Rev. 1970; 5: 143-207https://doi.org/10.1016/S0010-8545(00)80135-6Google Scholar,2Rorabacher D.B. 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Edvinsson Muñoz-Garcia enhanced cells.Inorganics. 6: 53https://doi.org/10.3390/inorganics6020053Google DSCs subject, consequence slow kinetics, much reduced voltage losses. presented open design scheme mediators, combining comprehensive control batteries other technologies. syntheses Ctetra Stetra associated reported first time documented supplemental information. To enable easier comparison literature, some experiments also conducted bis-(4,4?,6,6?-tetramethyl-2,2?-bipyridine) copper(I/II) bis(trifluoromethanesulfonyl)imide ([Cu(tmby)2](TFSI)1–2, Figure S1). UV-vis spectra molar extinction coefficients visible range acetone/acetonitrile Cu(Ctetra) Cu(Stetra) shown Figures 2A S2. showed metal-to-ligand S3) about 450 nm shoulder 575 nm, whereas species exhibited ligand-to-metal 650 lower coefficient (Table Cyclic voltammograms acetonitrile 2B) gave potentials 569 mV versus normal electrode (NHE) Cu(Stetra), respectively. Further cyclic voltammetry analysis different sets electrodes S4) scan rates (Figures S5–S10), Table S3 lists all derived parameters. geometries elucidated single-crystal X-ray diffraction (XRD) S11–S14; Tables S4–S7). assemble dimer, bridging binding each sites. monomers. DFT was minimum features Cu(II/I) 2C S15). Cu resides middle environment, Cu–N lengths 2.0 Å. instead, closer 5-membered ring (bond length ?2.0 Å) pyridines ?2.1 Å ?2.2 Cu(Stetra)). Molecular either 4-tert-butylpyridine (tBP) TFSI molecules axial position above plane calculated S15 S16, well S9. Binding negative tBP environment (?0.8 ?1.0 respectively), suggesting electrolyte. Bond angles good agreement S8), providing confidence values. For what concerns species, found 1.16 1.36 eV respectively, solvent-continuum model (here acetonitrile, values summarized This large difference translates an expected ratio present solution order 10?20–10?24. proof prevails form, only solid solution, optical computed time-dependent S3). fact, give rise wavelength 400 < ? 425 second >500 S2), more closely matches peaks observed experimental spectrum 2A). About properties, upon (Cu(I)Cu(II)) mixed valence 0.39 0.40 Cu(Stetra). smaller those common bipyridine complexes12Saygili imply should regenerate photosensitizers rapidly.Table 1Computed free ?G (in eV) inner-sphere reduction dimers––Cu(Ctetra)Cu(Stetra)(CuI)2 (L)2?G1.161.372 CuI (L)CuI CuII (L)2?G0.570.88CuI (L) + (L)2 tBP?G0.280.59CuI (L)(tBP)2 (L)2?G?0.150.38CuI2 2 tBP?G?0.60?0.19CuI2 (L)(tBP)CuI (L)?ox0.740.68CuII (L)–?red1.411.16–?tot2.151.84CuI (L)(tBP)?ox0.610.65CuII (L)(tBP)–?red0.970.62–?tot1.581.28CuI (L)(TFSI)?ox0.670.67CuII (L)(TFSI)–?red0.990.79–?tot1.671.46(CuI)2 (L)2?ox0.390.40CuI (L)2–?red0.340.20–?tot0.730.60 Open table tab single-oxidized, Cu(I)Cu(II) constitute transient species: into favored, especially presence (?0.60 ?0.19 tBP, (CT, 1B) restore (Cu(I))2, dissociation pathway. Therefore, live cycle, DSC electrolytes, anodic diffusion stem diffusing combination 1C). seem differ will point out later impedance spectroscopy, studied further spectroscopic tools. Implemented electrolyte, following offers decouples dye recombination: previously stabilized and, such, electrons oxidized heavily thermodynamically favored. after disproportionation, stabilizes injected unfavored up 1 per At same time, kinetically unlikely would involve separate Furthermore, bulkier Cu(tmby)2, it difficult them infiltrate monolayer, reducing rate back surface. materials, overcoming pending challenges DSCs. Raman recorded baseline-corrected 2B S18–S24), simulated computationally S25–S28) aid band assignment. Low-energetic vibrations below 900 cm?1 assigned counter bands 997 1,001 CuI(Stetra) CuI(Ctetra), combined Npy-Cu breathing mode.23Jain Z. Häggman Mirmohades Johansson M.B. Frustrated Lewis pair-mediated recrystallization CH3NH3PbI3 improved optoelectronic quality perovskite cells.Energy Environ. 3770-3782https://doi.org/10.1039/C6EE02544GGoogle From 1,250 1,500 number C=C aromatic, C–C aliphatic, CH3/CH2 stretches,24Maes bromine.Bull. Chim. 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Diffusion minority extracted listed S10 1.5-fold (1.2 × 10?5 cm2 s?1) CuII(Ctetra) (8.8 10?6 CuII(tmby)2 (8.4 s?1). al. recently suggested close interplay diffusive self-exchange systems.32Kim T.-Y. Raithel A.L. Hamann T.W. Real-time observation progression complexes.ACS Lett. 583-588https://doi.org/10.1021/acsenergylett.9b02677Google Given barriers oxidation/reduction, likely contributes concentrations. additive greatly limited S37 S39; S12), accordance earlier findings.33Hoffeditz W.L. Katz Deria Cutsail III, G.E. Pellin Farha O.K. Hupp J.T. One everything. multispecies shuttle 3731-3740https://doi.org/10.1021/acs.jpcc.6b01020Google 34Kavan Electrochemical Cu(II/I)-based 227: 194-202https://doi.org/10.1016/j.electacta.2016.12.185Google 35Wang Improved performance induced situ reactions couples 54: 12361-12364https://doi.org/10.1039/C8CC07191HGoogle 36Fürer S.O. Milhuisen R.A. Kashif M.K. Raga S.R. Acharya S.S. Forsyth Liu Frazer Duffy N.W. Ohlin C.A. al.The performance-determining role copper-bisphenanthroline mediators.Adv. 2002067https://doi.org/10.1002/aenm.202002067Google PEDOT?PEDOT probed spectroscopy 3B) resulting fitted circuit S38 (data S11). opposed S38), capacitive response e.g., (23 ? cm2) dominated Warburg resistance (6 cm2). Cu(Ctetra), capacitance 32 recorded. latter case, exponent ? constant phase element increased beyond 0.95, indicating interface nearly resembled capacitor. (RQ element) shifted far commonly ionic (25 ms Cu(tmby)2), modeled slower interfaces Lück al.37Lück Latz double layer lithium-ion batteries.Phys. 2019; 21: 14753-14765https://doi.org/10.1039/C9CP01320BGoogle support proposed since restoration cathode scenario follows kinetics. reason behind stems Gibbs former (?0.19 eV). assume dominates whereas, presumably, effects, appear series devices, fill factor, section. Overall, finite-length low-frequency regime, that—despite contributions self-exchange—ion ultimately mechanism. note (Tables S11 S12) generally exceed S10). “apparent” measuring voltammetric methods shuttles.22Michaels reasons decoupling sometimes (especially bases) Similar observations parameters obtained full illumination conditions S40; S13). ability photoinduced 3C) 3D) absorption spectroscopy.38Yang Efficient force achieved triphenylamine LEG4 TEMPO cells.Phys. 17: 15868-15875https://doi.org/10.1039/C5CP01880CGoogle Both regenerated Y123+ efficiently S41 S42; S14), efficiencies 99.6% 99.0% regenerative outcompetes sensitizer. employed fabricate dye, 3E; S15; S43). (VOC) trend expected, giving (911 881 mV, respectively). Still, photovoltages (0.87 NHE20Saygili Scholar): despite least 210–300 potential, 136 187 lower. loss result rates, predicted pathways interpretation photovoltage 3F), longer lifetimes intensities Cu(tmby)2. Cu(Ctetra)-based devices less (7.2% efficiency) Cu(Stetra)-based (8.7%), mostly factor drop, readily electrolyte/PEDOT interface, discussed earlier. general, accessible far-red ground-state energies. remains understood why, limit, force, photocurrent collected did improve Thus, exact mesoporous scaffold, investigated. Two presented. while inhibiting carrier disproportionation. gives access addressing limitations, DSCs, simultaneously. results minimal losses, comparably <0.40 transfers indicate suitable conductors.