Electronic properties of acenes: Oligomer to polymer structure

Santos, Maria Cristina dos

doi:10.1103/physrevb.74.045426

Cited by 76 publications

(59 citation statements)

References 11 publications

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“…8,9 Naphthacene ͑also referred to as tetracene͒, pentacene, and derivative compounds have been used recently to prepare highly ordered conducting organic materials or thin films with particularly large charge carrier mobilities. 10 In contrast with the prevailing view 11 that large acenes have a closed-shell singlet or open-shell triplet electronic ground states, a few groups [12][13][14][15][16] recently conjectured that large acenes such as hexacene, heptacene, or octacene should rather be regarded as open-shell singlet biradical systems, as a result of the instability of unrestricted ͑UBLYP, UB3LYP, UPW91, UBPW91, etc.͒ wave functions, in conjunction with rather modest basis sets ͑STO-3G, 6-31G ‫ء‬ , or cc-pVDZ͒. This in-stability was diagnosed 12 from the fact that in these unrestricted calculations the two outermost singly occupied ␣ and ␤ spin orbitals do not smoothly follow the D 2h symmetry point group imposed by the nuclear frame, but rather reflect an overwhelmingly strong symmetry breaking of the electronic wave function, 12 in the form of a localization of the two frontier electrons on opposite polyacetylenic strands.…”

Section: Introductionmentioning

confidence: 94%

A benchmark theoretical study of the electronic ground state and of the singlet-triplet split of benzene and linear acenes

Hajgató

Szieberth

Geerlings

et al. 2009

The Journal of Chemical Physics

200

216

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A benchmark theoretical study of the electronic ground state and of the vertical and adiabatic singlet-triplet ͑ST͒ excitation energies of benzene ͑n =1͒ and n-acenes ͑C 4n+2 H 2n+4 ͒ ranging from naphthalene ͑n =2͒ to heptacene ͑n =7͒ is presented, on the ground of single-and multireference calculations based on restricted or unrestricted zero-order wave functions. High-level and large scale treatments of electronic correlation in the ground state are found to be necessary for compensating giant but unphysical symmetry-breaking effects in unrestricted single-reference treatments. The composition of multiconfigurational wave functions, the topologies of natural orbitals in symmetry-unrestricted CASSCF calculations, the T1 diagnostics of coupled cluster theory, and further energy-based criteria demonstrate that all investigated systems exhibit a 1 A g singlet closed-shell electronic ground state. Singlet-triplet ͑S 0 -T 1 ͒ energy gaps can therefore be very accurately determined by applying the principles of a focal point analysis onto the results of a series of single-point and symmetry-restricted calculations employing correlation consistent cc-pVXZ basis sets ͑X=D, T, Q, 5͒ and single-reference methods ͓HF, MP2, MP3, MP4SDQ, CCSD, CCSD͑T͔͒ of improving quality. According to our best estimates, which amount to a dual extrapolation of energy differences to the level of coupled cluster theory including single, double, and perturbative estimates of connected triple excitations ͓CCSD͑T͔͒ in the limit of an asymptotically complete basis set ͑cc-pVϱZ͒, the S 0 -T 1 vertical excitation energies of benzene ͑n =1͒ and n-acenes ͑n =2-7͒ amount to 100.79, 76.28, 56.97, 40.69, 31.51, 22.96, and 18.16 kcal/mol, respectively. Values of 87.02, 62.87, 46.22, 32.23, 24.19, 16.79, and 12.56 kcal/mol are correspondingly obtained at the CCSD͑T͒ / cc-pVϱZ level for the S 0 -T 1 adiabatic excitation energies, upon including B3LYP/cc-PVTZ corrections for zero-point vibrational energies. In line with the absence of Peierls distortions, extrapolations of results indicate a vanishingly small S 0 -T 1 energy gap of 0 to ϳ4 kcal/ mol ͑ϳ0.17 eV͒ in the limit of an infinitely large polyacene.

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Section: Introductionmentioning

confidence: 94%

A benchmark theoretical study of the electronic ground state and of the singlet-triplet split of benzene and linear acenes

Hajgató

Szieberth

Geerlings

et al. 2009

The Journal of Chemical Physics

200

216

View full text Add to dashboard Cite

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“…First, although in this work the optimized geometries for acenes up to 12 all collapse to the D 2h point group, it does not necessarily mean that it will always keep such a high symmetry without any Jahn-Teller distortion or Peierls distortion as the number of benzene rings becomes even larger. In fact, some existing literature has already pointed out the possibility (95). Second, even if we assume the absence of the distortion and trust a geometry with D 2h symmetry, from Fig.…”

Section: St Energy Gapmentioning

confidence: 99%

Nature of ground and electronic excited states of higher acenes

Yang

Davidson

Yang

2016

Proc. Natl. Acad. Sci. U.S.A.

174

208

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Higher acenes have drawn much attention as promising organic semiconductors with versatile electronic properties. However, the nature of their ground state and electronic excited states is still not fully clear. Their unusual chemical reactivity and instability are the main obstacles for experimental studies, and the potentially prominent diradical character, which might require a multireference description in such large systems, hinders theoretical investigations. Here, we provide a detailed answer with the particleparticle random-phase approximation calculation. The 1 A g ground states of acenes up to decacene are on the closed-shell side of the diradical continuum, whereas the ground state of undecacene and dodecacene tilts more to the open-shell side with a growing polyradical character. The ground state of all acenes has covalent nature with respect to both short and long axes. The lowest triplet state 3 B 2u is always above the singlet ground state even though the energy gap could be vanishingly small in the polyacene limit. The bright singlet excited state 1 B 2u is a zwitterionic state to the short axis. The excited 1 A g state gradually switches from a doubleexcitation state to another zwitterionic state to the short axis, but always keeps its covalent nature to the long axis. An energy crossing between the 1 B 2u and excited 1 A g states happens between hexacene and heptacene. Further energetic consideration suggests that higher acenes are likely to undergo singlet fission with a low photovoltaic efficiency; however, the efficiency might be improved if a singlet fission into multiple triplets could be achieved.higher acenes | diradical | double excitation | particle-particle random-phase approximation | charge-transfer excitation

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“…magnetism without ions presenting partially filled d or f shells [7][8][9][10][11][12]. If the larger magnetic acenes can be stabilized, their magnetism coupled with the long spin-diffusion length will make this material class extremely appealing for the next generation of organic spintronics devices [29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

“…The smaller acenes have a non-magnetic (diamagnetic) ground state. For the higher acenes calculations predict the edges of the molecule to be spin polarized [7][8][9]11,12,18]. In this case there are two degenerate highest occupied molecular orbitals (HOMOs), each of them populated by a single electron.…”

Section: Introductionmentioning

confidence: 99%

Spin transport in highern-acene molecules

et al. 2011

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Abstract. We investigate the spin transport properties of molecules belonging to the acenes series by using density functional theory combined with the non-equilibrium Green's function approach to electronic transport. While short acenes are found to be non-magnetic, molecules comprising more than nine acene rings have a spin-polarized ground state. In their gas phase these have a singlet total spin configuration, since the two unpaired electrons occupying the doubly degenerate highest molecular orbital are antiferromagnetically coupled to each other. Such an orbital degeneracy is however lifted once the molecule is attached asymmetrically to Au electrodes via thiol linkers, leading to a fractional magnetic moment. In this situation the system Au/n-acene/Au can act as an efficient spin-filter with interesting applications in the emerging field of organic spintronics.

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Electronic properties of acenes: Oligomer to polymer structure

Cited by 76 publications

References 11 publications

A benchmark theoretical study of the electronic ground state and of the singlet-triplet split of benzene and linear acenes

A benchmark theoretical study of the electronic ground state and of the singlet-triplet split of benzene and linear acenes

Nature of ground and electronic excited states of higher acenes

Spin transport in highern-acene molecules

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