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Paul G. Wenthold - One of the best experts on this subject based on the ideXlab platform.

  • Spin-state dependent radical stabilization in nitrenes: the unusually small Singlet-Triplet Splitting in 2-furanylnitrene.
    The Journal of organic chemistry, 2011
    Co-Authors: Paul G. Wenthold
    Abstract:

    Geometries and energies of the triplet and singlet states of 2-furanylnitrene and 3-furanylnitrene have been calculated by using spin–flip coupled-cluster methods. Calculations with triple-ζ basis sets predict a singlet–triplet Splitting of 10.9 kcal/mol for 2-furanylnitrene, 4.5 kcal/mol smaller than that in phenylnitrene. In contrast, the singlet–triplet Splitting in 3-furanylnitrene is computed to be 1.9 kcal/mol larger than that in phenylnitrene. The differences in the singlet–triplet Splittings for the furanylnitrenes are attributed to the differences in the radical stabilizing abilities of the 2-furanyl- and 3-furanyl-groups compared to a phenyl ring. Comparison of the singlet–triplet Splittings of more than 20 substituted aromatic nitrenes and the radical stabilizing ability of the aromatic systems reveals a high degree of correlation between the singlet–triplet Splitting and the radical stabilizing ability, indicating that singlet states of aromatic nitrenes are preferentially stabilized by radica...

  • photoelectron imaging of ncccn the triplet ground state and the singlet triplet Splitting of dicyanocarbene
    Journal of Chemical Physics, 2010
    Co-Authors: Daniel J Goebbert, Paul G. Wenthold, Kostyantyn Pichugin, Dmitry Khuseynov, Andrei M Sanov
    Abstract:

    The photoelectron spectra of NCCCN− have been measured at 355 and 266 nm by means of photoelectron imaging. The spectra show two distinct features, corresponding to the ground and first excited states of dycianocarbene. With support from theoretical calculations using the spin-flip coupled-cluster methods, the ground electronic state of HCCCN is assigned as a triplet state, while the first excited state is a closed-shell singlet. The photoelectron band corresponding to the triplet is broad and congested, indicating a large geometry change between the anion and neutral. A single sharp feature of the singlet band suggests that the geometry of the excited neutral is similar to that of the anion. In agreement with these observations, theoretical calculations show that the neutral triplet state is either linear or quasilinear (X B31 or Σ3g−), while the closed-shell singlet (a A11) geometry is strongly bent, similar to the anion structure. The adiabatic electron binding energy of the closed-shell singlet is m...

  • Photoelectron Spectroscopy of Chloro-Substituted Phenylnitrene Anions
    The journal of physical chemistry. A, 2009
    Co-Authors: Neloni R. Wijeratne, Maria Da Fonte, Alan Ronemus, Phillip J. Wyss, Daryoush Tahmassebi, Paul G. Wenthold
    Abstract:

    The 355 nm time-of-flight negative ion photoelectron spectra of (o-, m-, and p-chlorophenyl)nitrene radical anions are reported. Electron affinities are obtained from the photoelectron spectra, and are 1.79 ± 0.05, 1.82 ± 0.05, and 1.72 ± 0.05 eV for the (o-, m-, and p-chlorophenyl)nitrenes, respectively. Singlet−triplet Splittings are determined to be 14 ± 2, 15 ± 1, and 14 ± 2 kcal/mol, respectively. The shapes of the photoelectron bands indicate resonance interactions in the singlet states for the ortho- and para-substituted isomers, which is attributed to quinoidal structures of the open-shell singlet states. Reanalysis of the photoelectron spectrum of phenylnitrene anion leads to a revised experimental singlet−triplet Splitting of 14.8 kcal/mol in the unsubstituted phenylnitrene.

  • Absolute Heat of Formation and Singlet-Triplet Splitting for HCCN
    The Journal of Physical Chemistry A, 2002
    Co-Authors: John C. Poutsma, Stephanie D. Upshaw, Robert R. Squires, Paul G. Wenthold
    Abstract:

    The absolute heat of formation at 298 K for ground-state triplet cyanocarbene, HCCN, has been determined from a measurement of the chloride dissociation energy of ClCHCN - . Analysis of the energy-resolved collision-induced dissociation cross section as a function of center-of-mass collision energy in a flowing afterglow triple quadrupole instrument gives a chloride dissociation enthalpy of 43.7 ′ 2.5 kcal/mol. Proton-transfer bracketing experiments were used to determine a gas-phase acidity, ΔH a c i d , of 357.7 ′ 2.0 kcal/mol for ClCH 2 CN. The heat of formation at 298 K for ClCH 2 CN was determined from collision-induced dissociation of a series of protonated nitriles to be 25.5 ′ 3.8 kcal/mol. The chloride ion dissociation enthalpy and the heat of formation and gas-phase acidity of ClCH 2 CN are combined in a simple thermochemical cycle to give an absolute heat of formation for HCCN of 115.6 ′ 5.0 kcal/mol. High level theoretical calculations were performed in support of the experimental study at the G2 (I), CBS-Q (II), CBS-APNO (III), B3LYP/6-31G * (IV), and B3LYP/6-311++G * * (V) levels of theory. The compound methods, I-III, give predictions for the acidity and heat of formation of ClCH 2 CN and for the heat of formation of the triplet ground state and first excited singlet state of HCCN that are in good agreement with experiment. The density functional theory predictions (IV,V) for these quantities are fair at best. The heat of formation of 3 HCCN is used to derive additional thermodynamic quantities including a C-H bond dissociation enthalpy in CH 2 CN of 107.3 ′ 5.4 kcal/mol and a Singlet-Triplet Splitting for HCCN of 11.1 ′ 5.8 kcal/mol.

  • A computational study of the electron affinity of silene
    Chemical Physics Letters, 1998
    Co-Authors: Paul G. Wenthold
    Abstract:

    Abstract The electron affinity (EA) of silene, CH 2 SiH 2 , is investigated using density functional theory and molecular orbital calculations. EA values of 6.6, 4.1, and 9.0 kcal/mol are calculated at the B3LYP, BLYP, and BP86 levels of theory, respectively, suggesting that the ion is bound with respect to electron detachment in the gas phase. Calculations of the electron binding energy of the triplet state and the singlet–triplet Splitting in silene are used to establish a lower limit to the EA of 0.1–0.7 kcal/mol, consistent with the results obtained by direct calculation.

Henry F. Schaefer - One of the best experts on this subject based on the ideXlab platform.

  • Substituted Ortho-Benzynes: Properties of the Triple Bond.
    The Journal of organic chemistry, 2020
    Co-Authors: Mitchell Evan Lahm, Ryan K. Maynard, Justin M. Turney, Frank Weinhold, Henry F. Schaefer
    Abstract:

    Ortho-benzyne has been well studied by both experiment and theory. Its substituted variants, however, have been less carefully examined. Benchmark data are computed for unsubstituted ortho-benzyne using several density functional theory functionals and basis sets, up to cc-pVQZ. Optimized geometries for the substituted ortho-benzyne as well as harmonic vibrational frequencies and Singlet-Triplet Splittings are computed using the benchmarked functionals. A proximal (syn)OH substitution causes a mean θ1 distortion of +8.1 ± 1.4° from ortho-benzyne. Substituting in the proximal position with F shifts the Singlet-Triplet Splitting by +4.5 ± 0.4 kcal mol-1 from ortho-benzyne. Natural bond orbital analysis, including natural Coulomb electrostatics, elucidates the presence of three influences from the selected substituents: hyperconjugative, resonance, and electrostatic effects.

  • Erratum to: Telluroformaldehyde and its derivatives: structures, ionization potentials, electron affinities and singlet–triplet gaps of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species
    Theoretical Chemistry Accounts, 2012
    Co-Authors: Naziah B Jaufeerally, Hassan H Abdallah, Ponnadurai Ramasami, Henry F. Schaefer
    Abstract:

    A systematic investigation of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species is carried out using the second-order Moller–Plesset perturbation theory and density functional theory. The basis sets used for all atoms (except iodine and tellurium) in this work are of double-ζ plus polarization quality with additional s- and p-type diffuse functions and denoted DZP++. The LANL2DZdp ECP and 6-311G(d,p) basis sets are used for tellurium and iodine. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. The ionization potentials (IPad and IPad(ZPVE)), the four different forms of neutral–anion separations (EAad, EAad(ZPVE), VEA and VDE), the singlet–triplet Splittings as well as the HOMO–LUMO gaps are predicted. The electronegativity (χ) reactivity descriptor for the halogens (F, Cl, Br and I) and the calculated Mulliken’s electronegativity are used as tools to assess the interrelated properties of these telluroformaldehyde derivatives. The predicted IPad(ZPVE) values with the B3LYP functional range from 7.89 [I2CTe] to 9.16 eV [F(NC)CTe], the EAad(ZPVE) ranges from 1.29 [I2CTe] to 3.34 eV [(NC)2CTe], the singlet–triplet Splitting ranges from 0.64 [H(NC)CTe)] to 1.85 eV [F2CTe], and the HOMO–LUMO gap ranges from 2.21 [H(NC)CTe] to 3.42 eV [F2CTe]. The HOMO–LUMO gap is found to be proportional to the singlet–triplet Splitting. The results obtained are critically analyzed and discussed. This research is also compared with analogous studies of formaldehyde, thioformaldehyde and selenoformadehyde.

  • erratum to telluroformaldehyde and its derivatives structures ionization potentials electron affinities and singlet triplet gaps of the x2cte and xycte x y h f cl br i and cn species
    Theoretical Chemistry Accounts, 2012
    Co-Authors: Naziah B Jaufeerally, Hassan H Abdallah, Ponnadurai Ramasami, Henry F. Schaefer
    Abstract:

    A systematic investigation of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species is carried out using the second-order Moller–Plesset perturbation theory and density functional theory. The basis sets used for all atoms (except iodine and tellurium) in this work are of double-ζ plus polarization quality with additional s- and p-type diffuse functions and denoted DZP++. The LANL2DZdp ECP and 6-311G(d,p) basis sets are used for tellurium and iodine. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. The ionization potentials (IPad and IPad(ZPVE)), the four different forms of neutral–anion separations (EAad, EAad(ZPVE), VEA and VDE), the singlet–triplet Splittings as well as the HOMO–LUMO gaps are predicted. The electronegativity (χ) reactivity descriptor for the halogens (F, Cl, Br and I) and the calculated Mulliken’s electronegativity are used as tools to assess the interrelated properties of these telluroformaldehyde derivatives. The predicted IPad(ZPVE) values with the B3LYP functional range from 7.89 [I2CTe] to 9.16 eV [F(NC)CTe], the EAad(ZPVE) ranges from 1.29 [I2CTe] to 3.34 eV [(NC)2CTe], the singlet–triplet Splitting ranges from 0.64 [H(NC)CTe)] to 1.85 eV [F2CTe], and the HOMO–LUMO gap ranges from 2.21 [H(NC)CTe] to 3.42 eV [F2CTe]. The HOMO–LUMO gap is found to be proportional to the singlet–triplet Splitting. The results obtained are critically analyzed and discussed. This research is also compared with analogous studies of formaldehyde, thioformaldehyde and selenoformadehyde.

  • Singlet-Triplet Splitting of carbohydroxycarbene
    Molecular Physics, 1996
    Co-Authors: Yaoming Xie, Henry F. Schaefer
    Abstract:

    Ab initio quantum mechanical methods have been applied to determine the Singlet-Triplet Splitting of carbohydroxycarbene, which is the prototype of carbalkoxycarbenes. These methods employ basis sets up to triple-ζ plus double polarization plus f functions (TZ2Pf) in calibre and levels of correlation up to coupled cluster including single, double and perturbatively treated connected triple excitations (CCSD(T)). The triplet state is the ground state, which has the planar Cs symmetry structure, while the lowest singlet state has C1 symmetry. At the highest level of theory employed, the Singlet-Triplet Splitting is predicted to be 4·7 kcal mol-1, which falls between an early theoretical prediction of 7 kcal mol-1 by Kim and Schaefer (1980, J. Amer. Chem. Soc., 102, 5389) and recent experimental conclusions of Toscano, Platz, Nikolaev and Popic (1994, J. Amer. Chem. Soc., 116, 8146) from solution kinetics. The harmonic vibrational frequencies and their infrared intensities are also reported.

Wenlian Li - One of the best experts on this subject based on the ideXlab platform.

  • the application of charge transfer host based exciplex and thermally activated delayed fluorescence materials in organic light emitting diodes
    Organic Electronics, 2019
    Co-Authors: Ziqi Wang, Chao Wang, Heng Zhang, Bo Zhao, Wenlian Li
    Abstract:

    Abstract Here, we review systematically the applications of exciplex and thermally activated delayed fluorescence (TADF) materials as the host in organic light-emitting diodes (OLEDs), who is the charge transfer host based inter-molecular and intra-molecular, respectively. Exciplex and TADF materials present many advantages of natural bipolarity, small Singlet-Triplet Splitting energy and low driving voltage to act as the host rather than emitter. The applications of exciplex and TADF materials as the host in phosphorescent, fluorescent and white OLEDs are given and new challenges, suggestions are also provided finally for further research and potential development of this area.

  • thermally activated delayed fluorescence organic light emitting diodes based on exciplex emitter with high efficiency and low roll off
    Organic Electronics, 2016
    Co-Authors: Tianyou Zhang, Qiaogang Song, Zisheng Su, Wenlian Li
    Abstract:

    Abstract Highly efficient thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) based on exciplex are demonstrated in a blended system with commercially available 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC) and 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T). By well adjusting the ratio between these two materials, the optimized device shows a low turn-on voltage of 2.4 V and a high external quantum efficiency (EQE) of 11.6%. More importantly, the device retains an EQE of 9.4% even at a high luminescence of 1000 cd/m 2 . The low efficiency roll-off is attributed to the small Singlet-Triplet Splitting and the short of the delayed fluorescence lifetime. Both EQE and efficiency roll-off are ones of the best performance among the reported TADF OLEDs based on exciplex.

Mark A. Eriksson - One of the best experts on this subject based on the ideXlab platform.

  • Tunable Singlet-Triplet Splitting in a few-electron Si/SiGe quantum dot
    2012
    Co-Authors: Zhan Shi, Christie Simmons, Jonathan Prance, John King Gamble, Mark Friesen, Donald E. Savage, Max G. Lagally, Susan Coppersmith, Mark A. Eriksson
    Abstract:

    We measure the excited-state spectrum of a Si/SiGe quantum dot as a function of in-plane magnetic field and identify the spin of the lowest three eigenstates in an effective two-electron regime. We extract the Singlet-Triplet Splitting, an essential parameter for spin qubits, from the data. We find it to be tunable by lateral displacement of the dot, which is realized by changing two gate voltages on opposite sides of the device. We present calculations showing the data are consistent with a spectrum in which the first excited state of the dot is a valley-orbit state.

  • Tunable Singlet-Triplet Splitting in a few-electron Si/SiGe quantum dot
    Applied Physics Letters, 2011
    Co-Authors: Zhan Shi, Christie Simmons, Jonathan Prance, John King Gamble, Mark Friesen, Donald E. Savage, Max G. Lagally, Susan Coppersmith, Mark A. Eriksson
    Abstract:

    We measure the excited-state spectrum of a Si/SiGe quantum dot as a function of in-plane magnetic field, and we identify the spin of the lowest three eigenstates in an effective two-electron regime. The Singlet-Triplet Splitting is an essential parameter describing spin qubits, and we extract this Splitting from the data. We find it to be tunable by lateral displacement of the dot, which is realized by changing two gate voltages on opposite sides of the device. We present calculations showing the data are consistent with a spectrum in which the first excited state of the dot is a valley-orbit state.

Naziah B Jaufeerally - One of the best experts on this subject based on the ideXlab platform.

  • erratum to telluroformaldehyde and its derivatives structures ionization potentials electron affinities and singlet triplet gaps of the x2cte and xycte x y h f cl br i and cn species
    Theoretical Chemistry Accounts, 2012
    Co-Authors: Naziah B Jaufeerally, Hassan H Abdallah, Ponnadurai Ramasami, Henry F. Schaefer
    Abstract:

    A systematic investigation of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species is carried out using the second-order Moller–Plesset perturbation theory and density functional theory. The basis sets used for all atoms (except iodine and tellurium) in this work are of double-ζ plus polarization quality with additional s- and p-type diffuse functions and denoted DZP++. The LANL2DZdp ECP and 6-311G(d,p) basis sets are used for tellurium and iodine. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. The ionization potentials (IPad and IPad(ZPVE)), the four different forms of neutral–anion separations (EAad, EAad(ZPVE), VEA and VDE), the singlet–triplet Splittings as well as the HOMO–LUMO gaps are predicted. The electronegativity (χ) reactivity descriptor for the halogens (F, Cl, Br and I) and the calculated Mulliken’s electronegativity are used as tools to assess the interrelated properties of these telluroformaldehyde derivatives. The predicted IPad(ZPVE) values with the B3LYP functional range from 7.89 [I2CTe] to 9.16 eV [F(NC)CTe], the EAad(ZPVE) ranges from 1.29 [I2CTe] to 3.34 eV [(NC)2CTe], the singlet–triplet Splitting ranges from 0.64 [H(NC)CTe)] to 1.85 eV [F2CTe], and the HOMO–LUMO gap ranges from 2.21 [H(NC)CTe] to 3.42 eV [F2CTe]. The HOMO–LUMO gap is found to be proportional to the singlet–triplet Splitting. The results obtained are critically analyzed and discussed. This research is also compared with analogous studies of formaldehyde, thioformaldehyde and selenoformadehyde.

  • Erratum to: Telluroformaldehyde and its derivatives: structures, ionization potentials, electron affinities and singlet–triplet gaps of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species
    Theoretical Chemistry Accounts, 2012
    Co-Authors: Naziah B Jaufeerally, Hassan H Abdallah, Ponnadurai Ramasami, Henry F. Schaefer
    Abstract:

    A systematic investigation of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species is carried out using the second-order Moller–Plesset perturbation theory and density functional theory. The basis sets used for all atoms (except iodine and tellurium) in this work are of double-ζ plus polarization quality with additional s- and p-type diffuse functions and denoted DZP++. The LANL2DZdp ECP and 6-311G(d,p) basis sets are used for tellurium and iodine. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. The ionization potentials (IPad and IPad(ZPVE)), the four different forms of neutral–anion separations (EAad, EAad(ZPVE), VEA and VDE), the singlet–triplet Splittings as well as the HOMO–LUMO gaps are predicted. The electronegativity (χ) reactivity descriptor for the halogens (F, Cl, Br and I) and the calculated Mulliken’s electronegativity are used as tools to assess the interrelated properties of these telluroformaldehyde derivatives. The predicted IPad(ZPVE) values with the B3LYP functional range from 7.89 [I2CTe] to 9.16 eV [F(NC)CTe], the EAad(ZPVE) ranges from 1.29 [I2CTe] to 3.34 eV [(NC)2CTe], the singlet–triplet Splitting ranges from 0.64 [H(NC)CTe)] to 1.85 eV [F2CTe], and the HOMO–LUMO gap ranges from 2.21 [H(NC)CTe] to 3.42 eV [F2CTe]. The HOMO–LUMO gap is found to be proportional to the singlet–triplet Splitting. The results obtained are critically analyzed and discussed. This research is also compared with analogous studies of formaldehyde, thioformaldehyde and selenoformadehyde.

  • Telluroformaldehyde and its derivatives: structures, ionization potentials, electron affinities and singlet–triplet gaps of the X_2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species
    Theoretical Chemistry Accounts, 2012
    Co-Authors: Naziah B Jaufeerally, Hassan H Abdallah, Ponnadurai Ramasami, Henry F. Schaefer Iii
    Abstract:

    A systematic investigation of the X_2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species is carried out using the second-order Møller–Plesset perturbation theory and density functional theory. The basis sets used for all atoms (except iodine and tellurium) in this work are of double-ζ plus polarization quality with additional s - and p -type diffuse functions and denoted DZP++. The LANL2DZdp ECP and 6-311G( d , p ) basis sets are used for tellurium and iodine. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. The ionization potentials (IP_ad and IP_ad(ZPVE)), the four different forms of neutral–anion separations (EA_ad, EA_ad(ZPVE), VEA and VDE), the singlet–triplet Splittings as well as the HOMO–LUMO gaps are predicted. The electronegativity (χ) reactivity descriptor for the halogens (F, Cl, Br and I) and the calculated Mulliken’s electronegativity are used as tools to assess the interrelated properties of these telluroformaldehyde derivatives. The predicted IP_ad(ZPVE) values with the B3LYP functional range from 7.89 [I_2CTe] to 9.16 eV [F(NC)CTe], the EA_ad(ZPVE) ranges from 1.29 [I_2CTe] to 3.34 eV [(NC)_2CTe], the singlet–triplet Splitting ranges from 0.64 [H(NC)CTe)] to 1.85 eV [F_2CTe], and the HOMO–LUMO gap ranges from 2.21 [H(NC)CTe] to 3.42 eV [F_2CTe]. The HOMO–LUMO gap is found to be proportional to the singlet–triplet Splitting. The results obtained are critically analyzed and discussed. This research is also compared with analogous studies of formaldehyde, thioformaldehyde and selenoformadehyde. Graphical Abstract