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2-Iminophenol ligands and their Boron Complexes: Coordination-Controlled Photophysical Duality
Denis Jacquemin1,2, Julien Massue3
1Nantes UniversitéCNRS, CEISAM UMR 6230, F-44000 Nantes, France.
Inorganic Chemistry
|May 15, 2026
Summary
2-iminophenol ligands, known as anils, exhibit excited-state intramolecular proton transfer (ESIPT). Boron coordination in boranils enhances fluorescence, enabling environment-sensitive applications.
Area of Science:
- Photophysics and Supramolecular Chemistry
- Organic and Organoboron Chemistry
Background:
- 2-iminophenol ligands (anils) possess internal hydrogen bonds, facilitating excited-state intramolecular proton transfer (ESIPT).
- ESIPT in anils can lead to thermochromic and photochromic properties, but often quenches solution-state fluorescence.
- Aggregation-induced emission (AIE) has been observed in confined media, forming fluorescent nanoaggregates.
Purpose of the Study:
- To provide a concise overview of the photophysical properties of anils and their boron complexes (boranils).
- To highlight the impact of boron coordination on the optical characteristics of these compounds.
- To explore the potential of boranils in applications requiring environment-sensitive fluorescence.
Main Methods:
- Review of recent literature on the synthesis and photophysical characterization of anils and boranils.
- Analysis of structure-property relationships, focusing on the role of the N'̂'O chelating site.
- Discussion of excited-state intramolecular proton transfer (ESIPT) mechanisms and their influence on optical behavior.
Main Results:
- Anils exhibit ESIPT, leading to isomerizable imine moieties and potential photochromism.
- While anils often lack solution-state fluorescence, they can display aggregation-induced emission (AIE).
- Boron coordination to anils forms boranils, rigidifying the molecular structure and enabling intense, environment-sensitive fluorescence in solution and solid states.
Conclusions:
- Boron coordination significantly enhances the photophysical properties of 2-iminophenol ligands.
- Boron complexes (boranils) offer tunable fluorescence, making them promising for sensing and imaging applications.
- The rigidification induced by boron coordination overcomes the fluorescence quenching issues associated with ESIPT in anils.
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