Photoelectron spectra and electronic structures of some naphtho[1,2-d]thiazoles

Rademacher, Paul; Kowski, Klaus; Müller, Annerose; Bohlmann, G.

doi:10.1016/0022-2860(93)80125-f

Cited by 9 publications

(13 citation statements)

References 21 publications

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“…We report in Fig. 7 the comparison between experimental [47][48][49][50][51] and theoretical ionization energies evaluated from sc-GW and G 0 W 0 based on the HF, PBE, and PBE0 starting points, for thiophene, benzothiazole, 1,2,5-thiadiazole, naphthalene, and tetrathiafulvalene. For an unbiased assessment, it would be desirable to benchmark sc-GW against higher level theories, since in experiment the distinction between vertical and adiabatic ionization energies is difficult and vibrational effects are always present.…”

Section: Spectral Properties Of Moleculesmentioning

confidence: 99%

Self-consistentGW: All-electron implementation with localized basis functions

et al. 2013

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This paper describes an all-electron implementation of the self-consistent GW (sc-GW ) approach-i.e., based on the solution of the Dyson equation-in an all-electron numeric atom-centered orbital basis set. We cast Hedin's equations into a matrix form that is suitable for numerical calculations by means of (i) the resolution-of-identity technique to handle four-center integrals and (ii) a basis representation for the imaginary-frequency dependence of dynamical operators. In contrast to perturbative G 0 W 0 , sc-GW provides a consistent framework for ground-and excited-state properties and facilitates an unbiased assessment of the GW approximation. For excited states, we benchmark sc-GW for five molecules relevant for organic photovoltaic applications: thiophene, benzothiazole, 1,2,5-thiadiazole, naphthalene, and tetrathiafulvalene. At self-consistency, the quasiparticle energies are found to be in good agreement with experiment and, on average, more accurate than G 0 W 0 based on Hartree-Fock or density-functional theory with the Perdew-Burke-Ernzerhof exchange-correlation functional. Based on the Galitskii-Migdal total energy, structural properties are investigated for a set of diatomic molecules. For binding energies, bond lengths, and vibrational frequencies sc-GW and G 0 W 0 achieve a comparable performance, which is, however, not as good as that of exact-exchange plus correlation in the random-phase approximation and its advancement to renormalized second-order perturbation theory. Finally, the improved description of dipole moments for a small set of diatomic molecules demonstrates the quality of the sc-GW ground-state density. Many-body perturbation theory (MBPT) 1 in the GW approach for the electron self-energy 2-4 provides a natural framework for an ab initio, parameter-free description of photo-ionization processes and charged excitations. 5 In recent years, the GW approach has become a popular method for the computation of band gaps and charged excitation energies for extended 6,7 and finite systems. 8,9 In numerical implementations, following Hybertsen and Louie, 10 it is standard practice to treat the GW self-energy as a single-shot perturbation (G 0 W 0 ) acting on a Kohn-Sham (KS) or Hartree-Fock (HF) reference system. Thus, excitation energies are evaluated from first-order Feynman-Dyson perturbation theory as corrections to a set of single-particle eigenvalues.The popularity of the G 0 W 0 approximation stems from the substantial reduction in the complexity of Hedin's equations at first-order perturbation theory: The KS or HF eigenstates from a self-consistent field calculation can be used as basis functions and provide a convenient representation in which the noninteracting Green's function is diagonal. In this basis, only diagonal matrix elements of the self-energy are needed to evaluate quasiparticle corrections at first order. Thus, G 0 W 0 grants a considerable simplification of the linear algebra operations which is decisive for applying the theory to large molecules and solids.Although num...

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Section: Spectral Properties Of Moleculesmentioning

confidence: 99%

Self-consistentGW: All-electron implementation with localized basis functions

et al. 2013

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“…IE 2 has IE 2 A $9.95 eV, and IE 2 V 10.24 eV; only IE 3 V 10.48 eV was determined. The symmetry identification of IE 2 and IE 3 is not agreed [11][12][13][14], although Koopmans' theorem [11] led to the order: p À1 4 < p À1 3 LP À1 N . The absence of a strong 0-0band makes identification of the p À1 3 state uncertain, IE from LP À1 N are often Gaussian in shape.…”

Section: Ionization Energies (Ie)mentioning

confidence: 95%

“…The lowest ionization energy of thiazole is: adiabatic (IE A ) 9.37 and vertical (IE V ) 9.43 eV [11]. Seven vibrational members were observed on IE 1 A ; the relatively strong 0-0 band implied a p-ionisation, which was assigned to p À1 4 [11][12][13][14]. This vibrational pattern (in stick form) is used extensively in the present study, as an identifier for Rydberg states in the VUV spectrum.…”

Section: Ionization Energies (Ie)mentioning

confidence: 96%

“…An electron diffraction (ED) study [21] has also been reported. Molecular properties from these MW studies, such as dipole moments [17], 14 N quadrupole coupling constants [18], and nonlocal contributions of the diamagnetic susceptibility component perpendicular to the ring [19], are known from these MW studies. These properties are compared with our ground state structural results, and with previous theoretical calculated values [22][23][24][25][26] in Appendix A.…”

Section: Molecular Structurementioning

confidence: 99%

“…A number of important thiazoles occur in nature; one forms a crucial part of vitamin B 1 (thiamine), and other examples are the fungal metabolites epothilones-A, -B and -C, important as cancer chemotherapy drugs. In order to interpret the VUV Rydberg spectrum, we also reconsider the order of cationic states previously reported in UV-photoelectron spectra (UV-PES) [11][12][13][14] and Penning ionization (PIES) [15,16].…”

Section: Introductionmentioning

confidence: 98%

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The electronic states of thiazole studied by VUV absorption spectroscopy and ab initio configuration interaction methods

Palmer

2008

Chemical Physics

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The thiazole VUV absorption spectrum over the range 5-12 eV shows intense bands near 5.4, 6.0, 7-7.8, 8.2-8.8, 9.2-10.1 and 10.2-11.0 eV; there is marked vibrational structure in the 7.5-8.5 and 10.2-11 eV regions. A number of Rydberg states have been identified, largely from IE 1 , but also tentative values for ones from IE 2 and IE 4 . Electronic excitation energies for valence and Rydberg-type states have been computed using ab initio multi-reference multi-root CI methods, and these have been compared with the VUV envelope. Calculated energies for low-lying Rydberg states are close to those expected, and there is generally a good correlation between the theoretical intensities and calculated density of states, with the experimental envelope. The CI studies used a triple zeta + polarization basis set, augmented by diffuse (Rydberg) orbitals. The lowest absorption bands are dominated by intense pp * (A 0 ) valence states, together with LP N p * and pr * states, which are relatively weak. The lowest Rydberg states arise from excitation of the occupied MOs in the sequential order p 4 < r 18 (LP N ) < p 3 < p 2 < r 17 (LP S ) this same order is determined by CI for ionisation in the UV-PES spectrum. Adiabatic structures of the r-and p-triplets, -cations and the p-anion have been compared with the ground state structure. The known phosphorescence of thiazole is from the 3 A triplet state (C 1 symmetry) where significant twisting of C 5 H and S to opposite sides of the mean plane occurs. Some theoretical molecular properties of thiazole are described, which give good agreement with microwave spectral data.

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The Thiazole Ylide: A Frequently Invoked Intermediate Is a Stable Species in the Gas Phase

McGibbon

Hrušák

Lavorato

et al. 1997

Chemistry A European J

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The 1, 2-hydrogen shift isomers of neutral (singlet and triplet) thiazole (1) and its radical cation have been investigated by a combination of mass spectro-metric experiments and hybrid density functional theory calculations. The latter were used to probe the structures and stabilities of selected C3 H3 NS and C3 H3 NS(.+) isomers and transition state structures. Although 3H-thiazole-2-ylidene (2) is less stable than 1, by 31.5 kcalmol(-1) , it is expected to be capable of independent existence, since the 1, 2-hydrogen shift from carbon to nitrogen involves a very large energy barrier of 72.4 kcalmol(-1) . The other 1, 2-hydrogen shift reaction from C(2) leads not to the expected cyclic 1H-thiazole-2-ylidene structure (3), which is apparently unstable, but rather to the ring-opened species HSCHCHNC (4), which is 34.5 kcalmol(-1) higher in energy than 1. The barrier in this case is lower but still large (54.9 kcalmol(-1) ). The triplet ground states of 1, 2 and 4 are considerably destabilised (69.5, 63.2 and 58.7 kcalmol(-1) ) relative to their singlet states. Interestingly, in addition to 2(.+) and 4(.+) , the cyclic radical cation 3(.+) is predicted to be stable although it is substantially higher in energy than ionised thiazole 1(.+) (by 53.9 kcalmol(-1) ), whereas 2(.+) and 4(.+) are much closer in energy (only 10.2 and 27.0 kcalmol(-1) higher, respectively). Dissuading 2(.+) and 3(.+) from isomerising to 1(.+) are energy barriers of 52.6 and 15.3 kcalmol(-1) , respectively. Experimentally, dissociative ionisation of 2-acetylthiazole enabled the generation of 2(.+) , which could be differentiated from 1(.+) by collisional activation mass spectrometry. Reduction of the ylide ion 2(.+) in neutralisation-reionisation mass spectrometry experiments yielded the corresponding neutral molecule 2. This direct observation of a thiazolium ylide provides support for postulates of such species as discrete intermediates in a variety of biochemical transformations.

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Photoelectron spectra and electronic structures of some naphtho[1,2-d]thiazoles

Cited by 9 publications

References 21 publications

Self-consistentGW: All-electron implementation with localized basis functions

Self-consistentGW: All-electron implementation with localized basis functions

The electronic states of thiazole studied by VUV absorption spectroscopy and ab initio configuration interaction methods

The Thiazole Ylide: A Frequently Invoked Intermediate Is a Stable Species in the Gas Phase

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