Related Experiment Video
Updated: May 11, 2026
05:47
Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
Published on: August 7, 2018
Molecular Design Principles for Photoactive Transition Metal Complexes: A Guide for "Photo-Motivated" Chemists.
Giacomo Morselli1, Christian Reber2, Oliver S Wenger1
1Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.
Journal of the American Chemical Society
|March 27, 2025
Summary
Researchers explore strategies for controlling excited states in d-block coordination compounds. This guide focuses on achieving luminescence and photochemistry by slowing energy dissipation or targeting dissociative states for radical generation.
Area of Science:
- Coordination Chemistry
- Photophysics
- Photochemistry
Background:
- Electronically excited states in luminescence and photochemistry are unstable, rapidly decaying via nonradiative energy release (heat).
- Energy dissipation typically occurs on femtosecond (fs) timescales, requiring slowing to nanosecond (ns) timescales for luminescence and photochemistry.
- Controlling excited state lifetimes and pathways presents significant challenges in coordination chemistry.
Purpose of the Study:
- To provide a concise guide for synthesizing luminescent and photochemically active coordination compounds with d-block elements.
- To encourage chemists to apply synthetic expertise to photophysics and photochemistry.
- To stimulate novel approaches for synthetic control over excited state behavior.
Main Methods:
- Review of recent advances in controlling excited state dynamics in d-block coordination compounds.
- Focus on strategies to slow energy dissipation for luminescence.
- Exploration of targeting dissociative excited states for metal-ligand bond homolysis and radical generation.
Main Results:
- Identified key factors and challenges in achieving luminescence and photochemistry in coordination compounds.
- Highlighted the emerging strategy of utilizing dissociative excited states for subnanosecond radical generation.
- Presented a framework for synthetic control over excited state properties.
Conclusions:
- Achieving controlled luminescence and photochemistry requires careful manipulation of excited state lifetimes and decay pathways.
- Targeting dissociative excited states offers a promising route to synthetically useful radicals on short timescales.
- This work aims to bridge synthetic chemistry with photophysics and photochemistry for d-block coordination compounds.
Related Concept Videos
02:58Properties of Transition Metals
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
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.
01:26Thermal 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.
00:56Extraction: Advanced Methods
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is formed in...