Low-lying electronically excited states of cycl[3.3.3]azine, a bridged 12.pi.-perimeter

Leupin, Werner; Wirz, Jakob

doi:10.1021/ja00539a016

Cited by 119 publications

(133 citation statements)

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“…Finally, the qualitative results obtained by the flash-photolysis technique for the triplet absorption spectra of the [4n]annulenes 22 (tetraalkyl derivative [45]), 23 [46], and cyc1[3.3.3]azine [47] are in agreement with the present calculations. Since we have retained the standard parameter set used for PPP-SCI calculations of closed-shell hydrocarbons, it is likely that heterocycles can be treated by the same method using standard parameters for the heteroatoms.…”

supporting

confidence: 89%

Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State

Gisin

Wirz

1983

Helvetica Chimica Acta

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SummaryThe semiempirical PPP-SCF-SCI method has been adapted to even-electron, open-shell x-systems by performing the SCF calculation on the lowest triplet configuration and choosing a limited set of single electronic excitations from the latter for configuration interaction. The basic approximations and parameters of the standard PPP model were retained. The results were compared with experimental triplet-triplet absorption spectra of aromatic hydrocarbons and with more elaborate calculations available for selected systems. The reliability of the model was found to be comparable to its well-known performance in predicting the absorption spectra of closed-shell x-systems and of conjugated radicals. Triplet-state absorption spectra for various planar, conjugated biradicals were calculated and, where possible, compared with experimental data.

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supporting

confidence: 89%

Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State

Gisin

Wirz

1983

Helvetica Chimica Acta

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“…First, the UV/Vis absorption properties of 3 and 5 a were examined in chloroform (Figure , 1.0×10 −5 M for overall spectra and 1.0×10 −4 M for inset in visible region). The spectra resembled with those reported for other 5AP derivatives . The strong (molar absorption coefficient ( ϵ ) ∼ 3×10 4 M −1 cm −1 ) and weak ( ϵ ∼0.3×10 4 M −1 cm −1 ) absorption bands were observed in the ultraviolet and visible regions, respectively.…”

Section: Resultssupporting

confidence: 82%

“…The strong (molar absorption coefficient ( ϵ ) ∼ 3×10 4 M −1 cm −1 ) and weak ( ϵ ∼0.3×10 4 M −1 cm −1 ) absorption bands were observed in the ultraviolet and visible regions, respectively. The strong absorption band was assigned to the allowed π–π* transition, whereas the weak absorption band was assigned to the forbidden HOMO−LUMO transition . Notably, the ϵ value of 5AP−B was larger than that of 5AP−Ph, suggesting that the HOMO−LUMO transition of 5AP−B should have the more allowed character compared to those of the previous 5AP derivatives as well as 5AP−Ph .…”

Section: Resultsmentioning

confidence: 93%

Enhancing Light‐Absorption and Luminescent Properties of Non‐Emissive 1,3,4,6,9b‐Pentaazaphenalene through Perturbation of Forbidden Electronic Transition by Boron Complexation

et al. 2020

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We report an improvement of optical properties of the non‐emissive molecule through shuffling the molecular orbitals by boron complexation. The 1,3,4,6,9b‐pentaazaphenelene (5AP) derivative having a 2‐(dimesitylboryl)phenyl group was synthesized through a substitution reaction from a 2‐bromophenyl compound. The formation of the B−N dative bond was confirmed by 11B{1H} NMR spectroscopy and a single‐crystal X‐ray structure analysis. Most of the conventional 5AP derivatives hardly showed emission despite their planar and rigid molecular structures. The previous reports on 5AP derivatives ascribed the non‐luminescent behavior to the forbidden transition between frontier orbitals. On the other hand, the 5AP‐based boron complex in this work showed enhanced light absorption and luminescence from the HOMO−LUMO transition. Theoretical calculations suggested that the boron complexation should play a critical role in perturbing the forbidden character of the HOMO−LUMO transition. Because the nitrogen atom on the 5AP moiety formed the Lewis acid−base pair with the boron atom, the energy level of the HOMO of 5AP was downshifted. The character of the HOMO−LUMO transition of the boron complex was changed to afford the improved optical properties of the boron complex.

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“…['2h' ' *' I In the case of ring systems the bond fixation corresponds to the loss of the delocalization of the conjugated bonding system present in benzene ([6]annulene) and still present to a large extent in [IRIannu-lene. In addition, various configurations are possible for larger rings, non-planar arrangements often being preferred.l"bl However, even when the molecule is forced into a nearly planar configuration by a transannular bond or by substituents," 3, 141 NMR spectroscopy has shown that the higher annulenes become increasingly polyenic. This has again been demonstrated recently in a comparison between a structurally partially fixed [38]ann~lene['~] and smaller rings in the same series.…”

Section: On the Long-wavelength Absorption Of Some Conjugated Organicmentioning

confidence: 99%

The Search for Highly Colored Organic Compounds

Fabian

Zahradník

1989

Angew. Chem. Int. Ed. Engl.

147

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Until now the study of organic compounds in which the n-electron system is excited by absorbed light has been mainly concentrated on the ultraviolet and visible regions of the electromagnetic spectrum. Various new applications, such as the use of conjugated organic compounds as dye lasers or as materials for storing information with the help of diode lasers, led to the synthesis of new compounds which absorb light in the near infrared (NIR). It is possible to use structure-color relationships to predict the properties of such new compounds when they belong to dyestuff classes which have already been studied in detail; in this case the approach involves decreasing the energy difference between the ground state and the first excited state. A less conventional starting point is provided by molecular structures in which from the outset there is only a very small energy difference between the lowest-energy electronic states; such diradicaloid molecules occupy a special position among the various types of organic compounds. It is possible by means of suitable structural modification to stabilize such molecules in a singlet form which absorbs light at very long wavelengths (i.e. at small wave numbers).

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Low-lying electronically excited states of cycl[3.3.3]azine, a bridged 12.pi.-perimeter

Cited by 119 publications

References 4 publications

Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State

Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State

Enhancing Light‐Absorption and Luminescent Properties of Non‐Emissive 1,3,4,6,9b‐Pentaazaphenalene through Perturbation of Forbidden Electronic Transition by Boron Complexation

The Search for Highly Colored Organic Compounds

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