Deuterium Isotope Effects in Polymerization of Benzene under Pressure

Cai, Weizhao; Dunuwille, Mihindra; He, Jiangang; Taylor, Trevor V.; Hinton, Jasmine K.; MacLean, Mary C.; Molaison, Jamie J.; Santos, A. M. dos; Sinogeikin, Stanislav V.; Deemyad, Shanti

doi:10.1021/acs.jpclett.7b00536

Cited by 12 publications

(20 citation statements)

References 50 publications

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“…This is in agreement with the Raman active mode of the skeletal ring breathing motion. [ 34,35 ] The redshifted mode at ≈996 cm −1 in D‐B3PYMPM is about 3% smaller compared to that of H‐ B3PYMPM. In contrast to the RS spectra, Figure 1b shows that the absorption spectrum of the respective donor and acceptor chromophores does not change upon deuteration, indicating that the electron manifolds are isotope independent.…”

Section: Figurementioning

confidence: 99%

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Isotope Effect in the Magneto‐Optoelectronic Response of Organic Light‐Emitting Diodes Based on Donor–Acceptor Exciplexes

et al. 2020

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The isotope effect is studied in the magneto‐electroluminescence (MEL) and pulsed electrically detected magnetic resonance of organic light‐emitting diodes based on thermally activated delayed fluorescence (TADF) from donor–acceptor exciplexes that are either protonated (H) or deuterated (D). It is found that at ambient temperature, the exchange of H to D has no effect on the spin‐dependent current and MEL responses in the devices. However, at cryogenic temperatures, where the reverse intersystem crossing (RISC) from triplet to singlet exciplex diminishes, a pronounced isotope effect is observed. These results show that the RISC process is not governed by the hyperfine interaction as thought previously, but proceeds through spin‐mixing in the triplet exciplex. The observations are corroborated by electrically detected transient spin nutation experiments that show relatively long dephasing time at ambient temperature, and interpreted in the context of a model that involves exchange and hyperfine interactions in the spin triplet exciplex. These findings deepen the understanding of the RISC process in TADF materials.

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Section: Figurementioning

confidence: 99%

“…It is seen that most modes are redshifted upon deuteration, since deuterium is heavier than hydrogen. [31,34,35] Specifically, the mode at ≈944 cm −1 in D-mCP is about 6% redshifted compared with that in H-mCP (1007 cm −1 ). This is in agreement with the Raman active mode of the skeletal ring breathing motion.…”

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confidence: 99%

Isotope Effect in the Magneto‐Optoelectronic Response of Organic Light‐Emitting Diodes Based on Donor–Acceptor Exciplexes

et al. 2020

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“…For Phase I, the slope dν/dP of Raman mode at ~993 cm −1 is 5.1 cm −1 / GPa which is comparable with its earlier reported value as 5.0 cm −1 / GPa by Theiry et al [ 23 ] At higher pressure >2.5 GPa, the slope for the two Raman modes at 1004 and 1009 cm −1 are 3.1 and 3.8 cm −1 /GPa, respectively. Weizhao et al [ 34 ] observed slope of 4.32 cm −1 /GPa for pressure lower than 4.2 GPa (benzene I) and above this pressure 2.61 and 3.25 cm −1 /GPa for the two modes of benzene in Phases I and II in their static experiments. [ 34 ] Baggen et al [ 41 ] observed a phase change from benzene I to benzene II at 1.5 GPa in static experiments and observed slope of 4.6 cm −1 /GPa for lower than this pressure.…”

Section: Resultsmentioning

confidence: 99%

“…Katrusiak et al [ 33 ] performed single crystal X‐ray diffraction studies in the pressure range 0.1 MPa to 5 GPa and in the temperature range 295 to 670 K and have determined the structure of benzene Phase II. Recently, Weizhao et al [ 34 ] used high‐pressure synchrotron X‐ray, neutron diffraction, and micro‐Raman spectroscopy together with density functional calculations to investigate the isotope effects in benzene isotopologues C 6 H 6 and C 6 D 6 up to 46.0 GPa.…”

Section: Introductionmentioning

confidence: 99%

Phase transitions in benzene under dynamic and static compression

Rao

Chaurasia

Mishra

et al. 2020

J Raman Spectroscopy

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Phase transitions in liquid benzene under laser shocked conditions are studied using high‐resolution time‐resolved Raman spectroscopic technique. The C‐C ring breathing mode (υ1) of benzene at 993 cm−1 is analyzed to monitor the phase transitions occurring in the Raman spectra during shock wave propagation in the pressure range 1.3–5 GPa. Phase transition from liquid benzene to solid benzene (Phase I) is observed below 1.3 GPa, and above this pressure, another phase transition from Phases I and II occurs. We also performed Raman spectroscopic measurements under static compression employing diamond anvil cell (DAC) to compare the effect of shock wave on benzene with isothermal compression using DAC. In static pressure measurements, the first phase transition from liquid to solid benzene (orthorhombic) occurs at 0.3 GPa, and the second phase transition from benzene I (orthorhombic) to benzene Phase II (monoclinic) occurs at 2.3 GPa, which is higher than that observed in case of shock compression experiments. The observed high‐resolution spectrum enables us to determine the effect of pressure gradient upon the Raman spectrum of benzene in shocked condition. One‐dimensional radiation‐hydrodynamic simulations were performed to corroborate the Raman spectroscopic results under dynamic compression. Simulated spatial profiles of the shock wave propagation in benzene at different delay times are used to explain the observation of multiple Raman modes in the spectral region 990–1020 cm−1. It is understood that different regions of the sample experience distinct pressure due to shock pressure gradient across the sample. The new Raman modes appearing in this spectral region are attributed to the Raman signals due to phase transition and from differently shocked regions of benzene under dynamic compression. The effect of reflected shock wave from benzene‐glass interface manifested in terms of red shifting and intensity enhancement of Raman modes at higher pressure is explained in this study.

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“…This shifts the balance of charges across the P3HT:PCBM junction and leads to lowering of V oc by 0.24 eV upon the side‐chain deuteration of P3HT . A few other recent notable examples of experimentally observed H/D isotope effects are polymerization of benzene , stability of organic molecules in the electronic beam of the transmission electron microscope and the spin response in polymer films and devices . It is even argued that olfaction is sensitive to the H/D isotopic substitution through its effect on noncovalent interactions between the molecules .…”

Section: Introductionmentioning

confidence: 99%

Theoretical assessment of the nuclear quantum effects on polymer crystallinity via perturbation theory and dynamics

Jakowski

Huang

Sumpter

et al. 2018

Int J of Quantum Chemistry

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As seen in experiments with poly(3-hexylthiophene), substitution of hydrogen with deuterium on the main chain alone decreases crystallinity. To understand this effect, a general formalism for analysis of the dipole moments and polarizabilities incorporating quantum nuclei, is developed. The formalism, based on quantum dynamics of the proton/deuteron and on the perturbative analysis of the dipole interaction energy, accounts for the anharmonicity of a potential energy surface and for the anisotropy of molecular dipole moments. The formalism is implemented within the Discrete Variable Representation and the Density Functional Theory describing, respectively, the quantum proton/deuteron on the thiophene ring and the electronic structure of the 27-atom model polymer chain, embedded into a larger crystalline environment. The isotope effect is mainly attributed to the differences in the zero-point energy of the CH/CD bonds and to the isotope-dependence of the dipole-dipole inter-chain interactions.dipole interactions, isotope effect on crystallinity, nuclear quantum effects, perturbation theory, quantum dynamics | INTRODUCTIONIt is increasingly recognized that nuclear quantum effects (NQEs) associated with light nuclei, such as protons, may influence structure, dynamics and properties of large molecular systems and materials. The NQE studies are mainly focused on the zero-point vibrational energy (ZPE), delocalization of the nuclear wavefunction and quantum tunneling [1][2][3][4] . Liquid water is the prime example of a system in which NQEs are particularly important because of the central role of the hydrogen bonding on its properties [5][6][7] . The difference in stability of the hydrogen bonding and its deuterium-substituted equivalent is due to the interplay of two competing quantum effects: the ZPE of vibrations and quantum tunneling. Some other systems, which may be influenced by the quantum behavior of the nuclei, are two-dimensional materials [3,8] and conducting polymers [9,10] .Recent experiments have shown that selective deuteration of conducting polymers may change their optoelectronic properties [9] . For example, in an organic photovoltaic heterojunction, consisting of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM), selective deuteration of the hexyl side-chain of P3HT affects the open circuit voltage, V oc , through fluctuation of the energy levels of the electron donor (P3HT) and acceptor (PCBM). Because of the difference in fluctuations of H and D in their respective ground vibrational states due to the nuclear wavefunction delocalization, the rates of the charge transfer across a heterojunction and of the recombination are different for the protonated and deuterated versions of P3HT. This shifts the balance of charges across the P3HT:PCBM junction and leads to lowering of V oc by 0.24 eV upon the side-chain deuteration of P3HT [10] . A few other recent notable examples of experimentally observed H/D isotope effects are polymerization of benzene [11] , stability of organi...

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Deuterium Isotope Effects in Polymerization of Benzene under Pressure

Cited by 12 publications

References 50 publications

Isotope Effect in the Magneto‐Optoelectronic Response of Organic Light‐Emitting Diodes Based on Donor–Acceptor Exciplexes

Isotope Effect in the Magneto‐Optoelectronic Response of Organic Light‐Emitting Diodes Based on Donor–Acceptor Exciplexes

Phase transitions in benzene under dynamic and static compression

Theoretical assessment of the nuclear quantum effects on polymer crystallinity via perturbation theory and dynamics

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