Related Experiment Video
Updated: Jun 26, 2026
06:08
Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera
Published on: December 27, 2018
Three-chromophore excited-state mixed valence
Ryan M Hoekstra1, Marcelle M Dibrell, Michael N Weaver
1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
The Journal of Physical Chemistry. A
|December 24, 2008
Summary
Analyzing the tris(4-bromophenyl)amine radical cation reveals insights into excited-state mixed valence (ESMV). The study highlights limitations of effective coupling models for three-chromophore systems.
Area of Science:
- Photochemistry
- Spectroscopy
- Materials Science
Background:
- Tris(4-bromophenyl)amine radical cation is a three-chromophore system.
- Understanding excited-state mixed valence (ESMV) is crucial for molecular electronics and charge transfer studies.
Purpose of the Study:
- To analyze the lowest energy optical electronic absorption band of the tris(4-bromophenyl)amine radical cation.
- To interpret the electronic transition using two different ESMV models.
- To evaluate the applicability of effective coupling versus neighboring orbital models for describing ESMV phenomena.
Main Methods:
- Analysis of the lowest energy optical electronic absorption band.
- Interpretation of the electronic spectrum using two excited-state mixed valence (ESMV) models: effective coupling and neighboring orbital models.
- Calculation of spectra using Resonance Raman data and time-dependent theory of electronic and resonance Raman spectroscopies.
Main Results:
- The lowest energy electronic transition involves a p-bromophenyl orbital to nitrogen p orbital interaction, localizing positive charge on the chromophores.
- The three-chromophore system demonstrates the inadequacy of a simple effective coupling model for explaining ESMV splitting.
- While diabatic and adiabatic state energies differ between models, calculated absorption spectra exhibit similar vibrational fine structure.
Conclusions:
- The neighboring orbital model provides a more accurate description of ESMV splitting in this three-chromophore system compared to the effective coupling model.
- The study underscores the importance of considering specific orbital interactions for accurate modeling of excited-state electronic properties.
- Resonance Raman spectroscopy and theoretical calculations are effective tools for elucidating complex electronic transitions and validating spectroscopic models.
More Related Videos
Related Concept Videos
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
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
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:29The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:45Valence Bond Theory
Overview of Valence Bond Theory