scholarly journals Photophysical properties and electron transfer photochemical reactivity of substituted phthalimides

2020 ◽  
Vol 44 (40) ◽  
pp. 17252-17266
Author(s):  
Leo Mandić ◽  
Iva Džeba ◽  
Dijana Jadreško ◽  
Branka Mihaljević ◽  
László Biczók ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited States ◽  
Photophysical Properties ◽  
Electron Donors ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Photochemical Reactivity

Substituents on phthalimide affect its photophysics and photochemical reactivity. Electron donors generally result in low quantum yields of intersystem crossing and reactivity from singlet excited states.

scholarly journals Photochemical Reactivity of Naphthol-Naphthalimide Conjugates and Their Biological Activity

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3355
Author(s):  
Matija Sambol ◽  
Patricia Benčić ◽  
Antonija Erben ◽  
Marija Matković ◽  
Branka Mihaljević ◽  
...  
Keyword(s):  
Biological Activity ◽  
Rational Design ◽  
Human Cancer ◽  
Photophysical Properties ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Quinone Methide ◽  
Quantum Yields ◽  
Photochemical Reactivity ◽  
Human Cancer Cell Lines

Quinone methide precursors 1a–e, with different alkyl linkers between the naphthol and the naphthalimide chromophore, were synthesized. Their photophysical properties and photochemical reactivity were investigated and connected with biological activity. Upon excitation of the naphthol, Förster resonance energy transfer (FRET) to the naphthalimide takes place and the quantum yields of fluorescence are low (ΦF ≈ 10−2). Due to FRET, photodehydration of naphthols to QMs takes place inefficiently (ΦR ≈ 10−5). However, the formation of QMs can also be initiated upon excitation of naphthalimide, the lower energy chromophore, in a process that involves photoinduced electron transfer (PET) from the naphthol to the naphthalimide. Fluorescence titrations revealed that 1a and 1e form complexes with ct-DNA with moderate association constants Ka ≈ 105–106 M−1, as well as with bovine serum albumin (BSA) Ka ≈ 105 M−1 (1:1 complex). The irradiation of the complex 1e@BSA resulted in the alkylation of the protein, probably via QM. The antiproliferative activity of 1a–e against two human cancer cell lines (H460 and MCF 7) was investigated with the cells kept in the dark or irradiated at 350 nm, whereupon cytotoxicity increased, particularly for 1e (>100 times). Although the enhancement of this activity upon UV irradiation has no imminent therapeutic application, the results presented have importance in the rational design of new generations of anticancer phototherapeutics that absorb visible light.

scholarly journals Photophysical Properties of Nitrated and Halogenated Phosphorus Tritolylcorrole Complexes: Insights from Theory

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2779 ◽  
Author(s):  
Marta Alberto ◽  
Bruna De Simone ◽  
Gloria Mazzone ◽  
Nino Russo ◽  
Marirosa Toscano
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Energy Gap ◽  
Photophysical Properties ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Excited Singlet ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Singlet And Triplet States

The photophysical properties of a series of nitrated and halogenated phosphorus tritolylcorrole complexes were studied in dichloromethane solvent by using the density functional theory. Particular emphasis was given to the absorption spectra, the energy gap between the excited singlet and triplet states, and the magnitude of the spin-orbit couplings for a series of possible intersystem crossing channels between those excited states. The proposed study provides a better description of the photophysical properties of these systems while giving insights into their possible use as photosensitizers in photodynamic therapy.

scholarly journals Fluorescent Liquid Tetrazines

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 6047
Author(s):  
Maximilian Paradiz Paradiz Dominguez ◽  
Begüm Demirkurt ◽  
Marion Grzelka ◽  
Daniel Bonn ◽  
Laurent Galmiche ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Liquid Films ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Time Resolved ◽  
Fluorescence Quantum Yields ◽  
Exciton Migration ◽  
Orange Fluorescence ◽  
The Difference ◽  
Chain Lengths

Tetrazines with branched alkoxy substituents are liquids at ambient temperature that despite the high chromophore density retain the bright orange fluorescence that is characteristic of this exceptional fluorophore. Here, we study the photophysical properties of a series of alkoxy-tetrazines in solution and as neat liquids. We also correlate the size of the alkoxy substituents with the viscosity of the liquids. We show using time-resolved spectroscopy that intersystem crossing is an important decay pathway competing with fluorescence, and that its rate is higher for 3,6-dialkoxy derivatives than for 3-chloro-6-alkoxytetrazines, explaining the higher fluorescence quantum yields for the latter. Quantum chemical calculations suggest that the difference in rate is due to the activation energy required to distort the tetrazine core such that the nπ*S1 and the higher-lying ππ*T2 states cross, at which point the spin-orbit coupling exceeding 10 cm−1 allows for efficient intersystem crossing to occur. Femtosecond time-resolved anisotropy studies in solution allow us to measure a positive relationship between the alkoxy chain lengths and their rotational correlation times, and studies in the neat liquids show a fast decay of the anisotropy consistent with fast exciton migration in the neat liquid films.

State Dependent Photochemical and Photophysical Behavior of Dithiolate Ester and Trithiocarbonate RAFT Polymerization Agents.

2020 ◽  
Author(s):  
Daniel Falvey ◽  
Matthew Thum ◽  
Steven Wolf
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Raft Polymerization ◽  
Photophysical Properties ◽  
Energy Levels ◽  
Transient Absorption Spectroscopy ◽  
Quantum Yields ◽  
Peak Reduction ◽  
Initiation Mechanism ◽  
Reduction Potentials

The rise in popularity of photochemically initiated RAFT polymerization (photoRAFT) along with the broad spectrum of proposed, and possible, initiation mechanisms results in the need for careful characterization of the photophysical properties of some common RAFT agents. Direct irradiation of the RAFT agent as a means to generate radicals, also known as the photoiniferter mechanism, is one commonly proposed mechanism. The current study shows that the dithioesters and trithiocarbonates have lowest singlet, and triplet excited state energy levels that are close to, or lower then C-S bond dissociation energies. Excitation of these agents into their S<sub>1</sub> band results in negligible radical production, while excitation into S<sub>2</sub> or higher results in the decomposition of dithioesters and trithiocarbonates resulting in radical formation, but with low quantum yields. Likewise, there is significant literature precedence for an electron transfer initiation mechanism, PET-RAFT. It is shown that the dithioesters and trithiocarbonates all show peak reduction potentials at ca. -1.0 V (vs. SCE). However, transient absorption spectroscopy studies of the electron transfer from a mediator shows that theses reactions occur rapidly only when the mediator potential is more negative than -1.2 V (vs. SCE).

1,3,5-Triarylpyrazolines — pH-driven off-on-off molecular logic devices based on a “receptor1-fluorophore-spacer-receptor2” format with internal charge transfer (ICT) and photoinduced electron transfer (PET) mechanisms

2015 ◽  
Vol 93 (2) ◽  
pp. 199-206 ◽  
Author(s):  
Ramon Zammit ◽  
Maria Pappova ◽  
Esther Zammit ◽  
John Gabarretta ◽  
David C. Magri
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Charge Transfer ◽  
Photoinduced Electron Transfer ◽  
Photophysical Properties ◽  
Molecular Probes ◽  
Quantum Yields ◽  
Ph Sensing ◽  
Internal Charge Transfer ◽  
Internal Charge

The excited state photophysical properties of the 1,3,5-triarylpyrazolines 1–4 were studied in methanol and 1:1 (v/v) methanol–water, as well as 1:4 (v/v) methanol–water and water by fluorescence spectroscopy. The molecules 2–4 incorporate a “receptor1-fluorophore-spacer-receptor2” format while 1 is a reference compound based on a “fluorophore-receptor1” design. The molecular probes operate according to photoinduced electron transfer (PET) and internal charge transfer (ICT) processes. At basic and neutral pHs, 2–4 are essentially nonfluorescent due to PET from the electron-donating dimethylamino moiety appended on the 5-phenyl ring to the excited state of the 1,3,5-triarylpyrazoline fluorophore. At proton concentrations of 10−3 mol/L, the dimethylamino unit is protonated resulting in a strong blue fluorescence about 460 nm with significant quantum yields up to 0.54. At acid concentrations above 10−2 mol/L, fluorescence quenching is observed by an ICT mechanism due to protonation of the pyrazoline chromophore. Symmetrical off-on-off fluorescence–pH profiles are observed, spanning six log units with a narrow on window within three pH units. Hence, 2–4 are novel examples of ternary photonic pH sensing molecular devices.

scholarly journals Fluorescence properties of halogenated mono-hydroxyl corroles: the heavy-atom effects

2009 ◽  
Vol 13 (12) ◽  
pp. 1221-1226 ◽  
Author(s):  
Lei Shi ◽  
Hai-Yang Liu ◽  
Han Shen ◽  
Jun Hu ◽  
Guo-Liang Zhang ◽  
...  
Keyword(s):  
Fluorescence Spectra ◽  
Halogen Atom ◽  
Photophysical Properties ◽  
Heavy Atom ◽  
Phenyl Group ◽  
Atomic Weight ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Fluorescence Quantum Yields ◽  
Atom Effect

A series of mono-hydroxyl corrole bearing a fluorine (1), chlorine (2), bromine (3) and iodine (4) atom on its 10-phenyl group have been synthesized. Fluorescence spectroscopy shows that the halogen atom at meso-phenyl group of corroles exhibit significant heavy-atom effect on their photophysical properties. Fluorescence quantum yields and the lifetime of these corroles decrease with the increasing of the atomic weight of halogen atoms. The quenching of the fluorescence could be interpreted in terms of a heavy atom-induced increase in intersystem crossing from S1 to T1. The intersystem crossing rate constant of these corroles were also determined by transient fluorescence spectra.

scholarly journals The Synthesis and Photophysical Properties of Weakly Coupled Diketopyrrolopyrroles

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4744
Author(s):  
Michał Pieczykolan ◽  
James B. Derr ◽  
Amara Chrayteh ◽  
Beata Koszarna ◽  
John A. Clark ◽  
...  
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Photophysical Properties ◽  
Electronic Transitions ◽  
Intersystem Crossing ◽  
Straightforward Manner ◽  
Functional Theory ◽  
Weakly Coupled

Three centrosymmetric diketopyrrolopyrroles possessing either two 2-(2′-methoxyphenyl)benzothiazole or two 2-(2′-methoxyphenyl)benzoxazolo-thiophene scaffolds were synthesized in a straightforward manner, and their photophysical properties were investigated. Their emission was significantly bathochromically shifted as compared with that of simple DPPs reaching 650 nm. Judging from theoretical calculations performed with time-dependent density functional theory, in all three cases the excited state was localized on the DPP core and there was no significant CT character. Consequently, emission was almost independent of solvents’ polarity. DPPs possessing 2,5-thiophene units vicinal to DPP core play a role in electronic transitions, resulting in bathochromically shifted absorption and emission. Interestingly, as judged from transient absorption dynamics, intersystem crossing was responsible for the deactivation of the excited states of DPPs possessing para linkers but not in the case of dye bearing meta linker.

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