Excited State Aromaticity and Antiaromaticity: Opportunities for Photophysical and Photochemical Rationalizations

Rosenberg, Martin; Dahlstrand, Christian; Kilså, Kristine; Ottosson, Henrik

doi:10.1021/cr300471v

Cited by 425 publications

(450 citation statements)

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“…The excited state structure is buckled in a prefulvenic geometry. This behavior is a familiar feature of many small aromatics [26][27][28] and is also observed for neutral pyridine. [29][30][31][32] Very recently, Broquier et al have undertaken the investigation of protonated ortho, meta and para aminopyridine molecules 33,34 and have shown that although protonated aminopyridines are rather simple aromatic molecules, their deactivation mechanisms are indeed quite complex.…”

supporting

confidence: 54%

Vibronic spectra of protonated hydroxypyridines: contributions of prefulvenic and planar structures

García

Nieuwjaer

Desfrançois

et al. 2017

Phys. Chem. Chem. Phys.

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Various hydroxypyridine derivatives are endogenous or synthetic photosensitizers which could contribute to solar radiation damages. The study of their excited states could lead to a better understanding of their action mechanisms. We present here the ultraviolet (UV) spectra of the protonated 2-, 3-and 4-hydroxypyridine. These spectra were obtained with an experimental device coupling an electrospray ion source with a cold quadrupole ion trap and a time of flight mass spectrometer. They display well resolved vibrational structures, with a clear influence of the position of the OH group. These results are interpreted with excited states calculations at the coupled cluster CC2 level.

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supporting

confidence: 54%

Vibronic spectra of protonated hydroxypyridines: contributions of prefulvenic and planar structures

García

Nieuwjaer

Desfrançois

et al. 2017

Phys. Chem. Chem. Phys.

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“…144 Aromaticity and antiaromaticity effects observed in the excited states may play a similar role in understanding reactivity and molecular properties as in the ground state. To gain insight into the nature of these effects we need to know which ground-state descriptors of aromaticity are transferable to excited states.…”

Section: Aromaticity Of Excited Statesmentioning

confidence: 99%

Quantifying aromaticity with electron delocalisation measures

et al. 2015

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Aromaticity cannot be measured directly by any physical or chemical experiment because it is not a well-defined magnitude. Its quantification is done indirectly from the measure of different properties that are usually found in aromatic compounds such as bond length equalisation, energetic stabilisation, and particular magnetic behaviour associated with induced ring currents. These properties have been used to set up the myriad of structural-, energetic-and magnetic-based indices of aromaticity known to date. Cyclic delocalisation of mobile electrons in two or three dimensions is probably one of the key aspects that characterise aromatic compounds. However, it has not been until the last decade that electron delocalisation measures have been widely employed to quantify aromaticity. Some of these new indicators of aromaticity such as the PDI, FLU, ING, and INB were defined in our group. In this paper, we review the different existent descriptors of aromaticity that are based on electron delocalisation properties, we compare their performance with indices based on other properties, and we summarise a number of applications of electronic-based indices for the analysis of aromaticity in interesting chemical problems.2

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“…Excited-state aromaticity [9][10][11][12] can be traced back to 1972, when Baird proposed that the aromaticity of planar annulenes in the S 0 state should be reversed in the T 1 state 13 , which was later applied to both Hückel and Möbius topologies by Aihara 14 . Experimentally, Wan and co-workers reported the formation of a 4π aromatic intermediate (or transition state) in a photosolvolysis reaction 15 .…”

mentioning

confidence: 99%

Adaptive aromaticity in S0 and T1 states of pentalene incorporating 16 valence electron osmium

Chen

Shen

et al. 2018

Commun Chem

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Aromaticity is a fundamental chemical concept of ever-increasing diversity. According to Hückel's and Baird's rules, cyclic conjugated species with 4n+2 π-electrons are aromatic in the singlet electronic ground state (S 0 ) and antiaromatic in the lowest triplet state (T 1 ), and vice-versa. Thus, species with aromaticity in both states have not yet been reported. Here we carry out density functional theory calculations on recently synthesized organometallics, namely osmapentalyne and osmapentalenes, and demonstrate the first example (16-electron osmapentalene) of aromaticity in both S 0 and T 1 states, which we term adaptive aromaticity. Further electronic structure analysis reveals that the excitation pattern for the formation of the T 1 state plays a crucial role in the achievement of adaptive aromaticity. Our findings highlight the role of a transition metal in unorthodox excitation behavior, and may aid the design of adaptive aromatics for photochemical and molecular magnetism applications.

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Excited State Aromaticity and Antiaromaticity: Opportunities for Photophysical and Photochemical Rationalizations

Cited by 425 publications

References 405 publications

Vibronic spectra of protonated hydroxypyridines: contributions of prefulvenic and planar structures

Vibronic spectra of protonated hydroxypyridines: contributions of prefulvenic and planar structures

Quantifying aromaticity with electron delocalisation measures

Adaptive aromaticity in S0 and T1 states of pentalene incorporating 16 valence electron osmium

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