Related Experiment Video
Updated: Aug 9, 2026
14:11
Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Photophysical processes involved within the anisole-thioindoxyl dyad system
Sudeshna Bhattacharya1, Tarun K Pradhan, Asish De
1Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, West Bengal.
The Journal of Physical Chemistry. A
|April 28, 2006
Summary
Researchers studied a novel anisole-thioindoxyl dyad (24MBTO) system. This photoswitchable system exhibits photoinduced electron transfer reactions and forms isomeric species, showing potential for advanced molecular applications.
Area of Science:
- Photochemistry and Photophysics
- Supramolecular Chemistry
- Computational Chemistry
Background:
- Understanding photoinduced electron transfer (PET) is crucial for developing advanced molecular systems.
- Dyad systems offer tunable photophysical properties for specific applications.
- Thioindoxyl derivatives are known for their photoresponsive characteristics.
Purpose of the Study:
- To investigate the photophysical properties and PET reactions in a synthesized anisole-thioindoxyl dyad (24MBTO).
- To explore the formation of isomeric species and the photoswitchable behavior of the dyad.
- To assess the potential of preventing charge recombination using beta-cyclodextrin.
Main Methods:
- Electrochemical, steady-state, and time-resolved spectroscopic techniques were employed.
- Theoretical computations using Time-Dependent Density Functional Theory (TD-DFT) with B3LYP and 6-311G(d,p) basis set were performed.
- Geometry optimization was conducted using the Gaussian package.
Main Results:
- Theoretical excitation energies correlated well with experimental observations.
- Electrochemical measurements confirmed the possibility of PET reactions between anisole and thioindoxyl moieties.
- Spectroscopic studies revealed the formation of Z- and E- isomeric species due to charge separation, indicating photoswitchable behavior.
Conclusions:
- The synthesized 24MBTO dyad functions as a versatile photoswitchable system.
- The study highlights the potential for controlling charge recombination by encapsulation within beta-cyclodextrin.
- This research contributes to the design of novel photoresponsive molecular materials.
Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
01:22Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.