Nonradiative relaxation process of the higher excited states of meso-substituted anthracenes

Hamanoue, Kumao; Hirayama, Satoshi; Nakayama, Toshihiro; Teranishi, Hiroshi

doi:10.1021/j100453a015

Cited by 50 publications

(45 citation statements)

References 2 publications

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“…This behavior is probably a consequence of the −NO 2 group, which is known to severely quench fluorescence (see below), an effect that may occur in addition to the photochemical isomerization channels in this molecule . Such effect is likely due to nonbonding orbitals in nitroaromatics which open the possibility for efficient intersystem crossing channels . In fact, as discussed later, transient absorbance measurements produced evidence for a low‐yield formation of a long‐lived species which was assigned to triplet states (see below).…”

Section: Resultsmentioning

confidence: 91%

Synthesis and Photodynamics of Stilbenyl‐Azopyrroles: Two‐Photon Controllable Photoswitching Systems

et al. 2019

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Three new stilbenyl‐azopyrroles 3 a–c were synthesized through a Mizoroki‐Heck C−C‐type coupling reaction between the 2‐(4′‐iodophenyl‐azo)‐N‐methyl pyrrole (1), and three different para‐substituted styrene derivatives. Inclusion of additional NO2 and NMe2 groups at the para‐position of the stilbenyl section resulted in significant changes of their linear and non‐linear optical properties. The photoisomerization behavior was studied through ultrafast laser techniques for single‐ and two‐photon excitation. The time‐resolved studies indicate that, despite the drastic changes in conjugation, the typical path for photoisomerization is maintained in these systems for both single and biphotonic excitation. In particular, the NO2 substituted molecule showed improved two‐photon absorption capacities, together with a significant trans−cis isomerization channel, implying that the photoswitching process can be controlled with high spatial precision through non‐linear optical excitation.

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Section: Resultsmentioning

confidence: 91%

Synthesis and Photodynamics of Stilbenyl‐Azopyrroles: Two‐Photon Controllable Photoswitching Systems

et al. 2019

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“…Spectroscopic studies, mainly by Hamanoue [56][57][58][59][60], and Testa and their co-workers [61,62] were subsequently performed in an effort to detect the proposed excited states and reactive intermediate species participating in the photochemistry of NPAH compounds. Studies by Hamanoue et al using 9-nitroanthracene and several meso-substituted nitroanthracene derivatives suggested that NPAH compounds decay through two simultaneous pathways after light absorption [29,[56][57][58][59][60]. Singlet-to-triplet intersystem crossing was proposed as one of the relaxation pathways (path 1 in Figure 3).…”

Section: Brief Summary Of the Primary Photochemical Pathways In Npahsmentioning

confidence: 99%

On the Primary Reaction Pathways in the Photochemistry of Nitro-Polycyclic Aromatic Hydrocarbons

Crespo‐Hernández¹

2013

Mod Chem Appl

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The primary reaction pathways in the photochemistry of nitro-polycyclic aromatic hydrocarbons under specific laboratory conditions are briefly summarized. In addition, photochemical data is presented for 2-nitronaphthalene, 1-nitronaphthalene, and 2-methyl-1-nitronaphthalene in cyclohexane and acetonitrile solutions under aerobic and anaerobic conditions. It is shown that molecular oxygen significantly reduces the photodegradation quantum yield of 1-nitronaphthalene and 2-methyl-1-nitronaphthalene by 63% and 81%, respectively, whereas 2-nitronaphthalene is photoinert in both solvents under aerobic and anaerobic conditions. In addition, it is proposed that recombination of the aryl and nitrogen (IV) dioxide geminate radical pair within the solvent cage or internal conversion of an initially formed intramolecular charge transfer state may play an important role in the fraction of excited molecules that returns to the ground state in 1-nitronaphthalene and 2-methyl-1-nitronaphthalene. Scavenging of radical species by molecular oxygen and the generation of singlet oxygen in high yield are proposed to contribute to the photochemistry of these nitro-naphthalene derivatives in solution.

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“…The primary pathways after excitation to the first singlet excited state in these compounds include, as the main channel, rapid intersystem crossing to the triplet manifold which results in the formation of a highly phosphorescent state. [1][2][3][4][5] In several nitrated aromatic compounds an additional direct reactive channel exists in parallel with the formation of T 1 . This channel corresponds to a molecular rearrangement of the bonding of the NO 2 group to the aromatic rings, leading to the dissociation of nitrogen(II) oxide (NO‚) and the formation of an aryoxyl radical (Ar-O‚ ).…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Intersystem Crossing in 1-Nitronaphthalene. An Experimental and Computational Study

2008

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Previous studies have established that the major pathway for the first singlet excited state of 1-nitronaphthalene is intersystem crossing to the triplet manifold. In this contribution we present determinations of the decay of the S1 state of this compound in several solvents to establish the time scale of the multiplicity change as a function of the polarity and hydrogen-bonding ability of the solvent environment. The measurements were made with the femtosecond frequency up-conversion technique to follow the weak spontaneous molecular emission which precedes triplet formation. Our results show that in all environments the S1 lifetime is 100 fs or less, making 1-nitronaphthalene the organic compound with the fastest multiplicity change ever measured. We also show that the bathochromic shifts observed for the first absorption band imply changes in the relative energies of the singlet and triplet manifolds, which in turn manifest in a 2-fold increase of the fluorescence lifetime in cyclohexane compared with the polar solvents. Additionally, we performed excited-state calculations at the TD-DFT/ PBE0/6-311++G(d,p) level of theory with the PCM model for solvation. The TD-DFT theory identifies the presence of upper triplet states which can act as receiver states in this highly efficient photophysical pathway. Together, the experimental and theoretical results show that the dynamics of the S1 state in 1-nitronaphthalene represent an extreme manifestation of El-Sayed's rules due to a partial (n-pi*) character in the receiver triplets which are nearly isoenergetic with S1, determining a change in the molecular spin state within 100 fs.

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Nonradiative relaxation process of the higher excited states of meso-substituted anthracenes

Cited by 50 publications

References 2 publications

Synthesis and Photodynamics of Stilbenyl‐Azopyrroles: Two‐Photon Controllable Photoswitching Systems

Synthesis and Photodynamics of Stilbenyl‐Azopyrroles: Two‐Photon Controllable Photoswitching Systems

On the Primary Reaction Pathways in the Photochemistry of Nitro-Polycyclic Aromatic Hydrocarbons

Ultrafast Intersystem Crossing in 1-Nitronaphthalene. An Experimental and Computational Study

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