Photophysical Properties of the Lowest Excited Singlet and Triplet States of Thio- and Seleno-psoralens

Aloisi, Gian Gaetano; Elisei, Fausto; Moro, Stefano; Miolo, Giorgia; Dall’Acqua, Francesco

doi:10.1562/0031-8655(2000)071<0506:ppotle>2.0.co;2

Cited by 11 publications

(6 citation statements)

References 27 publications

(32 reference statements)

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“…32). The effects of the selenium atom on the fluorescence quantum yield could be ascribed to the heavy atom effect,45, 48 which promotes intersystem crossing as a nonradiative relaxation process competing with the fluorescence (cf. the spin–orbit coupling constants of oxygen, sulfur, and selenium are 154, 365, and 1659 cm −1 , respectively49).…”

Section: Discussionmentioning

confidence: 99%

Environment‐Sensitive Fluorophores with Benzothiadiazole and Benzoselenadiazole Structures as Candidate Components of a Fluorescent Polymeric Thermometer

Uchiyama¹,

Kimura²,

Gota³

et al. 2012

Chemistry A European J

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An environment-sensitive fluorophore can change its maximum emission wavelength (λ(em)), fluorescence quantum yield (Φ(f)), and fluorescence lifetime in response to the surrounding environment. We have developed two new intramolecular charge-transfer-type environment-sensitive fluorophores, DBThD-IA and DBSeD-IA, in which the oxygen atom of a well-established 2,1,3-benzoxadiazole environment-sensitive fluorophore, DBD-IA, has been replaced by a sulfur and selenium atom, respectively. DBThD-IA is highly fluorescent in n-hexane (Φ(f) =0.81, λ(em) =537 nm) with excitation at 449 nm, but is almost nonfluorescent in water (Φ(f) =0.037, λ(em) =616 nm), similarly to DBD-IA (Φ(f) =0.91, λ(em) =520 nm in n-hexane; Φ(f) =0.027, λ(em) =616 nm in water). A similar variation in fluorescence properties was also observed for DBSeD-IA (Φ(f) =0.24, λ(em) =591 nm in n-hexane; Φ(f) =0.0046, λ(em) =672 nm in water). An intensive study of the solvent effects on the fluorescence properties of these fluorophores revealed that both the polarity of the environment and hydrogen bonding with solvent molecules accelerate the nonradiative relaxation of the excited fluorophores. Time-resolved optoacoustic and phosphorescence measurements clarified that both intersystem crossing and internal conversion are involved in the nonradiative relaxation processes of DBThD-IA and DBSeD-IA. In addition, DBThD-IA exhibits a 10-fold higher photostability in aqueous solution than the original fluorophore DBD-IA, which allowed us to create a new robust molecular nanogel thermometer for intracellular thermometry.

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Section: Discussionmentioning

confidence: 99%

Environment‐Sensitive Fluorophores with Benzothiadiazole and Benzoselenadiazole Structures as Candidate Components of a Fluorescent Polymeric Thermometer

Uchiyama¹,

Kimura²,

Gota³

et al. 2012

Chemistry A European J

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“…8 Measurements of the corresponding quantum yields F D revealed moderate to sizeable values depending on the system under consideration. 7,[9][10][11] Furthermore, [2 + 2]photocycloadditions to fatty acids, electron transfer reactions, and fragmentation processes have been reported. 3,7 Commonly, photocycloadditions of psoralens to DNA bases are accounted as the key to understanding the mechanisms underlying the PUVA treatment.…”

Section: Introductionmentioning

confidence: 99%

“…Up to now, the situation is similar with respect to the photophysical prerequisites of the diverse photoreactions, i.e., the problem from which excited electronic state(s) the diverse reactions start out: Pertaining to cycloadditions to thymine and the production of O 2 ( 1 D g ), a prominent role has been suggested for the T 1 state. [11][12][13] Definite answers seem still to be missing, however. 6,14 In experimental photophysical studies on parent psoralen, its S 1 and T 1 states were assigned as (pp*) states.…”

Section: Introductionmentioning

confidence: 99%

Intersystem crossing driven by vibronic spin–orbit coupling: a case study on psoralen

Tatchen

Gilka

Marian

2007

Phys. Chem. Chem. Phys.

142

158

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For 7H-furo[3,2-g][1]benzopyran-7-one (psoralen), intersystem crossing (ISC) rate constants have been computed. Employing the Fermi golden rule, the harmonic approximation, and a pure-spin Born-Oppenheimer basis, both direct and vibronic spin-orbit (SO) coupling has been taken into account. Necessary data on electronic excitation energies and potential energy hypersurfaces originate from correlated all-electron calculations applying (time-dependent) density functional theory and the density functional theory/multireference configuration interaction approach. SO coupling has been treated by means of the one-center mean-field approximation. Vibronic SO couplings have been evaluated via numerical differentiation of SO matrix elements. Accounting only for direct SO coupling, rate constants of the order of k(ISC) approximately 10(10) s(-1) result for S2(n --> pi*) --> T1(pi --> pi*) ISC, whereas the rates of the channels S1 (pi --> pi*) --> {1,2 3} (pi --> pi*) do not exceed k(ISC) approximately 10(5) s(-1). Including vibronic SO coupling, rate constants of k(ISC) approximately 3 x 10(8) s(-1) are obtained for the S1 (pi --> pi*) --> T1 (pi --> pi*) ISC. The radiationless transition from the S1(pi --> pi*) state to the nearly degenerate T3(pi --> pi*) state has been estimated to be slightly less efficient (k(ISC) approximately 10(7) s(-1)). Based on our computed rates of ISC and excited state solvent shifts, we conclude that the experimentally observed appreciable triplet quantum yields of psoralen in polar protic media are primarily due to S1(pi --> pi*) --> T (pi --> pi*) channels. For heteroaromatic systems, (pi --> pi*)/(pi --> pi*) ISC driven by vibronic SO coupling is expected to be a common triplet state population mechanism.

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“…ref. [6][7][8] The first spectroscopic investigations of electronically excited psoralens were conducted in the 1970s by Song et al [9][10][11] They measured absorption and emission spectra in glassy ethanol matrices at low temperatures for a series of psoralens and coumarins. 11 All compounds show fluorescence as well as phosphorescence.…”

Section: Introductionmentioning

confidence: 99%

Vibronic absorption, fluorescence, and phosphorescence spectra of psoralen: a quantum chemical investigation

Tatchen

Marian

2006

Phys. Chem. Chem. Phys.

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Excited state potential energy hypersurfaces of 7H-furo[3,2-g][1]benzopyran-7-one (psoralen) have been explored employing (time-dependent) Kohn-Sham density functional theory. At selected points, we have determined electronic excitation energies and electric dipole (transition) moments utilizing a combined density functional/multireference configuration interaction method. Spin-orbit coupling has been taken into account employing an efficient, non-empirical spin-orbit mean-field Hamiltonian. Franck-Condon factors have been computed for vibrational modes with large displacements in the respective Dushinsky transformations. The simulated band spectra closely resemble experimental band shapes and thus validate the theoretically determined nuclear structures at the S(0), S(1), and T(1) minima. In the S(1) (pi(HOMO)-->pi*(LUMO)) state, the lactone bond of the pyrone ring is significantly elongated. From excited vibrational levels of the S(1) state a conical intersection between a (pi-->sigma*) excited state and the electronic ground state may be energetically accessible. Fast non-radiative decay via this relaxation pathway could explain the low fluorescence quantum yield of psoralen. The T(1) (pi(HOMO-1)-->pi*(LUMO)) exhibits a diradicaloid electronic structure with a broken C(5)-C(6) double bond in the pyrone ring. A variational multireference spin-orbit configuration interaction procedure yields a phosphorescence lifetime of 3 s, in excellent agreement with experimental estimates.

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Photophysical Properties of the Lowest Excited Singlet and Triplet States of Thio- and Seleno-psoralens

Cited by 11 publications

References 27 publications

Environment‐Sensitive Fluorophores with Benzothiadiazole and Benzoselenadiazole Structures as Candidate Components of a Fluorescent Polymeric Thermometer

Environment‐Sensitive Fluorophores with Benzothiadiazole and Benzoselenadiazole Structures as Candidate Components of a Fluorescent Polymeric Thermometer

Intersystem crossing driven by vibronic spin–orbit coupling: a case study on psoralen

Vibronic absorption, fluorescence, and phosphorescence spectra of psoralen: a quantum chemical investigation

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