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
02:24Properties of Enantiomers and Optical Activity
It is essential to understand the difference between chiral and achiral interactions and the implications thereof in optical activity and their applications. Just as our feet, which are chiral, interact uniquely with chiral objects, such as a pair of shoes, but identically with achiral socks, enantiomers of a molecule exhibit different properties only when they interact with other chiral media. An example of a significant implication from this facet is the phenomenon known as optical activity,...
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.
02:52Stereoisomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
02:30Chirality in Nature
Chirality is the most intriguing yet essential facet of nature, governing life’s biochemical processes and precision. It can be observed from a snail shell pattern in a macroscopic world to an amino acid, the minutest building block of life. Most of the snails around the world have right-coiled shells because of the intrinsic chirality in their genes. All the amino acids present in the human body exist in an enantiomerically pure state, except for glycine - the sole achiral amino acid. The...
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Related Experiment Video
Updated: Jun 12, 2026
09:33
Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
Second-Harmonic Hyper-Mie Optical Activity Enables Closed-Loop Chiral Photochemistry.
Hoyeon Choi1, Kody Whisnant2,3, Ben J Olohan1
1Centre For Photonics, Department of Physics, University of Bath, Bath, UK.
Advanced Materials (Deerfield Beach, Fla.)
|June 11, 2026
Summary
Researchers developed nonlinear chiral photochemistry using infrared light to transform nanomaterials. This method offers precise control and real-time monitoring of material changes, paving the way for sustainable chemical processing.
Area of Science:
- Materials Science
- Photochemistry
- Nanotechnology
Background:
- Traditional photochemistry often relies on ultraviolet light, facing limitations in selectivity and penetration depth.
- Developing sustainable chemical processing methods is crucial for environmental and industrial advancements.
Purpose of the Study:
- To introduce and demonstrate nonlinear chiral photochemistry for controlled material transformation.
- To utilize femtosecond infrared pulses for driving and tracking chemical reactions.
- To explore the application of chiroptical phenomena in monitoring material synthesis.
Main Methods:
- Frequency-doubling of femtosecond infrared pulses to drive photochemical reactions.
- Real-time monitoring of material transformation using second-harmonic scattering intensity.
- Utilizing chiroptical contrast to track changes in material structure.
- Observing the second-harmonic hyper-Mie optical activity effect.
Main Results:
- Successful transformation of chiral cadmium telluride/cadmium oxide (CdTe/CdO) nanohelices into CdO nanospheroids.
- Controlled oxidation sequence induced by circularly polarized light.
- A twenty-fold increase in second-harmonic intensity and polarization reversal upon CdTe exposure.
- Emergence of characteristic CdTe photoluminescence indicating material transformation.
Conclusions:
- Nonlinear chiral photochemistry provides a spatially confined, selective, and temporally-resolved method for material transformation.
- The experimental observation of the second-harmonic hyper-Mie effect validates theoretical predictions.
- This approach offers a novel pathway for advanced nanomaterial synthesis and processing.