Two-photon spectroscopy of antiaromatic molecules: the case of biphenylene

Bich, Vu Thi; Bini, Roberto; Salvi, Pier Remigio; Marconi, Giancarlo

doi:10.1016/0009-2614(90)85556-r

Cited by 12 publications

(6 citation statements)

References 31 publications

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“…This yields an estimate of 5.15 eV for the 0-0 transition in the free molecule, about 0.38 eV more than the calculated value. The shape of the band 13,14,17 indicates a difference between vertical and adiabatic excitation energy of less than 0.1 eV, which agrees well with the calculated value 0.08 eV. Extrapolation to the free molecule yields a value of about 5.25 eV for the vertical excitation energy, about 0.4 eV more than calculated.…”

Section: E Comparison With Experimentssupporting

confidence: 83%

Vertical and adiabatic electronic excitations in biphenylene: A theoretical study

Beck

Rebentisch

Hohlneicher

et al. 1997

The Journal of Chemical Physics

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Articles you may be interested inLow-lying electronic states and their nonradiative deactivation of thieno [3,4-b]pyrazine: An ab initio study J. Chem. Phys. 137, 224313 (2012); 10.1063/1.4770229 Improved virtual orbital multireference Møller-Plesset study of the ground and excited electronic states of protonated acetylene, C 2 H 3 + The low-lying singlet states of biphenylene have been studied using ab initio methods. Vertical excitation energies were calculated by multiconfigurational perturbation theory ͑CASPT2͒, starting from a complete active space self-consistent field ͑CASSCF͒ reference. The geometries of the most important low-lying excited states were individually optimized at the CASSCF level to study the difference between vertical and adiabatic excitations. Extended atomic natural orbital ͑ANO͒-type basis sets were used to calculate state energies. Geometry optimizations were done with smaller ANO-type basis sets. Excitations from the ground state to the 1 1 B 3g and 1 1 B 2u excited singlet states lead to pronounced geometry changes which alter the bond alternation pattern. The theoretical results provide a solid basis for the assignment and interpretation of experimental spectra.

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Section: E Comparison With Experimentssupporting

confidence: 83%

Vertical and adiabatic electronic excitations in biphenylene: A theoretical study

Beck

Rebentisch

Hohlneicher

et al. 1997

The Journal of Chemical Physics

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“…The central ring a in the class A compounds can be viewed as a 4π-electron CBD ring or alternatively as the four-membered ring in [4]radialene. The first compound in this series, biphenylene ( A1 ), , was suggested above to have an “aromatic chameleon” feature (Figure ). Yet, is this labeling in accordance with computational results?…”

Section: Resultsmentioning

confidence: 90%

“…Biphenylene could tentatively also be considered as an aromatic chameleon (Figure B) because in the S 0 state it can be influenced by a resonance structure with two 6π-electron benzene rings while in the T 1 state it can be described by four different Baird-aromatic resonance structures; one with a 12π-electron biradical perimeter ( T 1 -I ), two equivalent ones with 8π-electron circuits ( T 1 -III and T 1 -III′ ), and one with a central 4π-electron cycle ( T 1 -II ). Yet, biphenylene in its S 0 state can also be labeled as a Hückel-antiaromatic, and previous computational studies indicated that biphenylene in this state has localized C–C bonding and some antiaromatic character in the 12π-electron perimeter …”

Section: Introductionmentioning

confidence: 99%

Can Baird’s and Clar’s Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4nπ- and (4n+ 2)π-Rings?

et al. 2017

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Compounds that can be labeled as "aromatic chameleons" are π-conjugated compounds that are able to adjust their π-electron distributions so as to comply with the different rules of aromaticity in different electronic states. We used quantum chemical calculations to explore how the fusion of benzene rings onto aromatic chameleonic units represented by biphenylene, dibenzocyclooctatetraene, and dibenzo[a,e]pentalene modifies the first triplet excited states (T) of the compounds. Decreases in T energies are observed when going from isomers with linear connectivity of the fused benzene rings to those with cis- or trans-bent connectivities. The T energies decreased down to those of the parent (isolated) 4nπ-electron units. Simultaneously, we observe an increased influence of triplet state aromaticity of the central 4n ring as given by Baird's rule and evidenced by geometric, magnetic, and electron density based aromaticity indices (HOMA, NICS-XY, ACID, and FLU). Because of an influence of triplet state aromaticity in the central 4nπ-electron units, the most stabilized compounds retain the triplet excitation in Baird π-quartets or octets, enabling the outer benzene rings to adapt closed-shell singlet Clar π-sextet character. Interestingly, the T energies go down as the total number of aromatic cycles within a molecule in the T state increases.

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“…Two-photon active states of ππ * character belong to the A g and B 1g symmetry species. The two-photon spectrum of biphenylene in Figure 32 has been measured in the spectral range 225-370 nm combining fluorescence excitation and thermal lensing detection [225]. Figure 32.…”

Section: [12]annulenementioning

confidence: 99%

“…The structure of the S 2 state, having approximate D 2h symmetry according to semiempirical methods [214], is in good agreement with expectations. Biphenylene has been extensively investigated in the ground and lowest ππ * excited states [220][221][222][223][224][225][226].…”

Section: [12]annulenementioning

confidence: 99%

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Gellini

Salvi

2010

Symmetry

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The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]-and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties.

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Two-photon spectroscopy of antiaromatic molecules: the case of biphenylene

Cited by 12 publications

References 31 publications

Vertical and adiabatic electronic excitations in biphenylene: A theoretical study

Vertical and adiabatic electronic excitations in biphenylene: A theoretical study

Can Baird’s and Clar’s Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4nπ- and (4n+ 2)π-Rings?

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

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