Die Bedeutung von Donor-Acceptor-Wechselwirkungen im äußeren Schweratom-Effekt von AgNO3 auf das Lumineszenzverhalten von Aza-aromaten und Carbazolen / The Significance of Donor-Acceptor Interactions in the External Heavy Atom Effect of AgNO3 on the Luminescence Behaviour of Aza-aromatic Systems and Carbazoles

1978 ◽  
Vol 33 (8) ◽  
pp. 998-1000 ◽  
Author(s):  
M. Zander
Keyword(s):  
Aromatic Hydrocarbons ◽  
Transition Probabilities ◽  
Heavy Atom ◽  
Fluorescence Analysis ◽  
Electronic System ◽  
Electron Donors ◽  
Strong Electron ◽  
Donor Acceptor ◽  
Aromatic Systems ◽  
Atom Effect

The transition probabilities of spin-forbidden processes become much more enhanced in the case of aza-aromatic systems than for structurally related aromatic hydrocarbons when AgNO3 is used as an external heavy atom perturber. This is explained with the strong electron donor properties of aza-aromatic systems thus causing strong interaction between the π-electronic system and the perturber. Since carbazoles are weaker electron donors than aza-aromatic systems, the enhancement of the phosphorescence/fluorescence quantum yield ratio by AgNO3 is lower than for aza-aromatic systems. The different behaviour of aza-aromatic systems and aromatic hydrocarbons in the heavy atom experiment with AgNO3 can find applications in fluorescence analysis.

Revealing Internal Heavy Chalcogen Atom Effect on the Photophysics of Dibenzo[a,j]phenazine-Cored Donor–Acceptor–Donor Triad

2021 ◽  
Author(s):  
Shimpei Goto ◽  
Yuya Nitta ◽  
Nicolas Oliveira Decarli ◽  
Leonardo E de Sousa ◽  
Partycja Stachelek ◽  
...  
Keyword(s):  
Electron Acceptor ◽  
Organic Molecule ◽  
Electron Donors ◽  
Chalcogen Atom ◽  
Donor Acceptor ◽  
Atom Effect

A new twisted donor–acceptor–donor (D–A–D) multi-photofunctional organic molecule comprising of phenoselenazine as the electron-donors (Ds) and dibenzo[a,j]phenazine (DBPHZ) as the electron-acceptor (A) has been developed. The developed selenium-incorporated D–A–D compound...

An exceptionally long-lived triplet state of red light-absorbing compact phenothiazine-styrylBodipy electron donor/acceptor dyads: a better alternative to the heavy atom-effect?

2020 ◽  
Vol 56 (11) ◽  
pp. 1721-1724 ◽  
Author(s):  
Yuqi Hou ◽  
Qingyun Liu ◽  
Jianzhang Zhao
Keyword(s):  
Charge Transfer ◽  
Triplet State ◽  
Electron Donor ◽  
Heavy Atom ◽  
Red Light ◽  
Intersystem Crossing ◽  
Spin Orbital ◽  
Heavy Atom Effect ◽  
Donor Acceptor ◽  
Atom Effect

Heavy atom-free dyads showing a red light-absorbing and exceptionally long-lived triplet state based on a spin–orbital charge transfer intersystem crossing mechanism.

Notizen: Zur Lumineszenz von aromatischen Verbindungen mit Schweratom-Substituenten in unterschiedlichen Bindungssituationen / On the Luminescence of Aromatic Compounds with Heavy Atom Substituents in Different Bonding Situations.

1979 ◽  
Vol 34 (7) ◽  
pp. 909-910 ◽  
Author(s):  
G.-P. Blümer ◽  
M. Zander
Keyword(s):  
Electron Density ◽  
Aromatic Compounds ◽  
Heavy Atom ◽  
Electronic System ◽  
Chlorine Atoms ◽  
Heavy Atom Effect ◽  
Inductive Effects ◽  
Atom Effect

Compounds like III(4,9,10,11,12,13,13-Heptachloro-8b,9,12,12a-tetrahydro-9,12-methano-benzo[e]pyrene) are ex­amples for systems with heavy atom substituents in two different bonding situations. The halogen directly connected with the 7-electronic system causes an internal heavy atom effect whilst the halogens isolated from the .7-system by aliphatic carbons produce a “quasi external” heavy atom effect. The observation that the internal heavy atom effect in III is weaker than in halo phenanthrenes is explained with the lower electron density in the phenanthrene unit of III compared to phenanthrene. this lower electron density being a result of field and inductive effects of the peripherically arranged chlorine atoms.

Tetra(pyrazino[2,3-b]pyrazino)porphyrazines: Synthesis, absorption, photophysical and electrochemical properties of strongly electron-deficient macrocycles

2017 ◽  
Vol 21 (04-06) ◽  
pp. 302-310 ◽  
Author(s):  
Veronika Novakova ◽  
Bartosz Małachwiej ◽  
René Šebl ◽  
Miroslav Miletin ◽  
Petr Zimcik
Keyword(s):  
Electrochemical Properties ◽  
Absorption Spectra ◽  
Zinc Acetate ◽  
Heavy Atom ◽  
Blue Shift ◽  
Strong Electron ◽  
Reduction Potentials ◽  
Photophysical Parameters ◽  
Atom Effect ◽  
Template Reaction

Highly electron deficient 6,7-disubstituted (tert-butylsufanyl, 2,6-diisopropylphenoxy, diethylamino, 2-pyridyl, 2-thienyl, 2-furyl) pyrazino[2,3-[Formula: see text]]pyrazino-2,3-dicarbonitriles were prepared and attempted in cyclotetramerization to corresponding tetra(pyrazino[2,3-[Formula: see text]]pyrazino)porphyrazines (TPyzPyzPzs). Only the template reaction in pyridine with zinc acetate and only for the compounds substituted with tert-butylsulfanyl or 2,6-diisopropylphenoxy substituents resulted in efficient cyclotetramerization. Absorption spectra of these zinc TPyzPyzPzs indicated considerable blue shift of the main absorption Q-band ([Formula: see text] 693 nm and 669 nm in pyridine for tert-butylsulfanyl or 2,6-diisopropylphenoxy derivatives) when compared to other aza-analogs of naphthalocyanines. Photophysical parameters ([Formula: see text] [Formula: see text] 0.25, [Formula: see text] [Formula: see text] 0.65) seemed to be unaffected by change of the macrocycle core and only slightly by different peripheral substituents in agreement with heavy-atom effect. Electrochemical data revealed strong electron-deficient character of hetaryl disubstituted pyrazino[2,3-[Formula: see text]]pyrazino-2,3-dicarbonitriles. The first reduction potentials of tert-butylsulfanyl or 2,6-diisopropylphenoxy substituted zinc TPyzPyzPzs were even more cathodically shifted when compared to their corresponding pyrazino[2,3-[Formula: see text]]pyrazino-2,3-dicarbonitriles. TPyzPyzPzs represent an example of the strongest electron-deficient core among the phthalocyanines, naphthalocyanines and their aza-analogs.

Synthesis and photophysical studies of porphyrin-ferrocene conjugates

2007 ◽  
Vol 11 (10) ◽  
pp. 719-728 ◽  
Author(s):  
Hanaa Mansour ◽  
Mohamed E. El-Khouly ◽  
Shaban Y. Shaban ◽  
Osamo Ito ◽  
Norbert Jux
Keyword(s):  
Transient Absorption ◽  
Heavy Atom ◽  
Solvent Polarity ◽  
Separation System ◽  
Excited Singlet ◽  
Time Resolved ◽  
Quenching Efficiency ◽  
Donor Acceptor ◽  
Photophysical Studies ◽  
Atom Effect

The porphyrin-ferrocene conjugates ( P-nFc; n = 1, 2 and 4 ), which are simple examples of a donor-acceptor charge separation system, were synthesized. Their photoindued intramolecular and intermolecular processes have been investigated by time-resolved emission and nanosecond transient absorption techniques. Upon excitation of the porphyrins ( H 2P and ZnP ) moieties, an efficient fluorescence quenching of the excited singlet porphyrin is observed. It was found that the quenching efficiency increases with increasing number of attached ferrocene moieties and solvent polarity. The main quenching pathway involves (i) electron transfer from ferrocene to the singlet excited porphyrin and (ii) the heavy-atom effect.

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