Solvatochromism and Nonradiative Decay of Intramolecular Charge‐Transfer Excited States: Bands‐of‐Energy Model, Thermodynamics, and Self‐Organization

Pavlovich, V. S.

doi:10.1002/cphc.201200426

Cited by 31 publications

(16 citation statements)

References 89 publications

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“…The nanosecond lifetime of τ 2 in MeCN is consistent with the energy‐gap law for nonradiative decay in intramolecular charge transfer excited states. Hydrogen bonding in water can also contribute to the shorter lifetime of τ 2 in water, as protic media can contribute to nonradiative decay pathways due to favorable interaction with charge transfer states 17…”

Section: Resultsmentioning

confidence: 99%

Extending Metal‐to‐Polyoxometalate Charge Transfer Lifetimes: The Effect of Heterometal Location

Glass

Fielden

Kaledin

et al. 2014

Chemistry A European J

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In an effort to develop robust molecular sensitizers for solar fuel production, we examine the electronic structure and photodynamics of transition-metal-substituted polyoxometalates (POMs), a novel class of compound in this context. (4a), finding the longest lived charge transfer excited state so far observed in a POM and elucidating the electronic structures and excited state dynamics of these compounds at an unprecedented level. All species exhibit a biexponential decay in which early dynamic processes with time constants in the fs domain yield longer lived excited states which decay with time constants in the ps to ns domain. The initially formed states of 1a and 3a are considered to result from metal-topolyoxometalate charge transfer (MPCT) from Co II to W, while the longer-lived excited state of 1a is tentatively assigned to a localized intermediate MPCT state. The excited state formed by the tetrahedral cobalt(II) centered heteropolyanion (1a) is far longer-lived ( = 420 ps in H2O;  = 1700 ps in MeCN) than that of 3a ( = 1.3 ps), where the single Co II atom is located in a pseudo-octahedral addendum site. Short-lived states are observed for the two Co III containing heteropolyanions 2a ( = 4.4 ps) and 4a ( = 6.3 ps) and assigned solely to OCo III charge transfer. The dramatically extended lifetime for 1a vs 3a is ascribed to a structural change permitted by the coordinatively flexible central site, weak orbital overlap of the central Co with the polytungstate framework, and putative transient valence trapping of the excited electron on a single W atom, a phenomenon not noted previously in POMs.

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Section: Resultsmentioning

confidence: 99%

Extending Metal‐to‐Polyoxometalate Charge Transfer Lifetimes: The Effect of Heterometal Location

Glass

Fielden

Kaledin

et al. 2014

Chemistry A European J

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“…To find the three unknowns, C x , C y and C z , it is necessary to examine the broadening of absorption spectra resorting to convolution procedure. It is common knowledge 45,46 that the fluctuations of orientation (dipole-dipole) solute-solvent interactions lead to the inhomogeneous broadening of the spectrum. Considering eqn (3), the relation for the variance of maximum (or 0-0 transition energy) D 2 produced by orientation fluctuations can be expressed [46][47][48][49] as…”

Section: Orientation Inhomogeneous Broadening Calculation Of C X C Y...mentioning

confidence: 99%

Gas-phase energy of the S2←S0 transition and electrostatic properties of the S2 state of carotenoid peridinin via a solvatochromic shift and orientation broadening of the absorption spectrum

Pavlovich

2014

Photochem Photobiol Sci

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The solvent effect on the position and the shape of the absorption spectrum of peridinin for 12 protic and aprotic solvents as well as the temperature effect for methanol were studied using a solvatochromic theory based on the Onsager sphere cavity model. (Experimental data have been provided by T. Polivka and V. Sundström.) Solvatochromic calculations combined with estimations of orientation broadening of the absorption spectrum by convolution allowed the conclusion that the orientation (dipole-dipole), induction and dispersion solute-solvent interactions reasonably describes the position of the 0-0 frequency. The orientation interactions led to the blue solvatochromic shift, separating them from the induced and dispersion interactions, which produce a red shift. The FWHM of Gaussian of inhomogeneous broadening originated from the fluctuations of orientation interactions was demonstrated to be high (945 cm(-1)) even for such a nonpolar solvent as hexane. The value of |Δμ|/cos φ of -18.7 D has been found (Δμ = μ2 - μg, φ is the angle between Δμ and μg). By assigning peridinin to the idealized C2v point group, the large change of dipole moment |Δμ| of 18.7 D under S2←S0 transition is obtained for peridinin in gas phase. Moreover, the S2-excited state dipole moment μ2 has the opposite orientation relative to that at the ground S0 state μg. The determined gas-phase 0-0 energy of the S2←S0 transition, 22 910 cm(-1) (2.84 eV) is employed to calculate the polarizability change between the S0 and S2 states of 376 Å(3). The finding for the effective Onsager radius is of 9.4 Å. Obtained results for electrostatic properties of the S2 state are compared with those known from Stark spectroscopy and quantum-mechanical calculations.

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“…[9] With respect to neat film, λ PL of PCzAPT10 solution was distinctly red-shifted to 576 nm, which was due to solvatochromic effect typically happened in emitters with high polar CT-state in excited states. [10] In practice, λ PL of PCzAPT10 solution was monotonically shifted from 495 nm to 616 nm by using solvents with increased polarity in sequence, i. e. n-hexane, toluene, chlorobenzene and dichloromethane, (Figure S2). Additional peak located at ca.…”

Section: Resultsmentioning

confidence: 99%

“…Considering electrochemical electron-transfer process in solid-state ECL, [11] it was believed that the ECL process occurred within the PCzAPT10 film and also close to the PCzAPT10/ACN solid-liquid interface. TADF excited states of PCzAPT10 with highly polar CT characteristics [8] would be stabilized and largely influenced by polar solvent, [10] i. e. ACN in this case. Due to this reason, the ECL spectrum of PCzAPT10 would be redshifted significantly as compared with its PL spectrum in air.…”

Section: Resultsmentioning

confidence: 99%

Polymer Electrochemiluminescence Featuring Thermally Activated Delayed Fluorescence

Huang

Zhang

et al. 2021

ChemPhysChem

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Electrochemiluminescence (ECL) based on conjugated polymers or oligomers is persistently being pursued owing to its huge application scope ranging from ultra-sensitive bioanalysis to ultra-resolution imaging and spectroscopy. Because of the theoretical limit in radiative exciton generation yield (typicallỹ 25 %) of those polymers or oligomers, the corresponding ECL efficiency is still limited, which hampers its ECL performance and its related applications. Herein, we report ECL based on a thermally activated delayed fluorescence (TADF) polymer scaffold, which is characteristic of all-exciton harvesting in the ECL process, and thus potentially capable of achieving~100 % ECL efficiency. These desired properties of the TADF polymer ECL is attributed to a fast and efficient up-conversion process from non-radiative triplet to radiative singlet states under thermal activation, which is absent in conventional fluorescent polymers/oligomers, such as F8BT. In this study, various ECL modes, including annihilation or co-reactant mode using TPrA or S 2 O 8 2À as co-reactant, are confirmed for our model TADF polymer ECL system, which was different from fluorescent polymer ECL counterpart. Furthermore, solid-state ECL sensing on L-cysteine (an important marker of disease) is also evaluated by using the model TADF polymer. Ultralow detection limit in combination with high sensitivity and good specificity are achieved for this model system, indicative of a high potential of the TADF polymer scaffold for applications in the broad field of ECL.

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Solvatochromism and Nonradiative Decay of Intramolecular Charge‐Transfer Excited States: Bands‐of‐Energy Model, Thermodynamics, and Self‐Organization

Cited by 31 publications

References 89 publications

Extending Metal‐to‐Polyoxometalate Charge Transfer Lifetimes: The Effect of Heterometal Location

Extending Metal‐to‐Polyoxometalate Charge Transfer Lifetimes: The Effect of Heterometal Location

Gas-phase energy of the S2←S0 transition and electrostatic properties of the S2 state of carotenoid peridinin via a solvatochromic shift and orientation broadening of the absorption spectrum

Polymer Electrochemiluminescence Featuring Thermally Activated Delayed Fluorescence

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