Related Experiment Video
Updated: Apr 21, 2026

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Two act as one: unexpected dimers of catechol direct a solid-state [2+2] photodimerization in a six-component
Giannis S Papaefstathiou1, Andrew J E Duncan, Leonard R MacGillivray
1Department of Chemistry, University of Iowa, Iowa, IA 52242-1294, USA. len-macgillivray@uiowa.edu.
Abstract:
We describe hydrogen-bonded dimers of catechol that act collectively as a single template to direct an intermolecular [2+2] photocycloaddition in the solid state. The directed reactivity involves discrete, six-component hydrogen-bonded assemblies and a photoreaction that occurs stereoselectively and in quantitative yield.
Related Concept Videos
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Thermal and Photochemical Electrocyclic Reactions: Overview
Cycloaddition Reactions: MO Requirements for Photochemical Activation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
Stereoisomerism
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...

