Electron-rich phenanthroline bearing N-heterocyclic imine substituents: synthesis, optical properties, metal coordination

Abstract

Polypyridines functionalized with π-donating groups constitute a class of electron-rich ligands with significant relevance in coordination chemistry and catalysis. The incorporation of strongly basic guanidinyl substituents, however, often introduces multiple binding sites, with coordination typically favoring the guanidyl nitrogen atoms. Herein, we report the synthesis and characterization of a new electron-rich 1,10-phenanthroline ligand featuring bulky NHI groups that define a well-structured coordination cavity. Protonation studies and the preparation of a zinc(II) complex reveal that Lewis acids preferentially coordinate at the phenanthroline nitrogen atoms rather than the NHI moiety. The electronic and photophysical properties of the new ligand and its complexes are explored through a combination of computational and experimental methods, demonstrating that its emission and absorption characteristics are highly sensitive to protonation, concentration, and metal coordination.

Graphical abstract: Electron-rich phenanthroline bearing N-heterocyclic imine substituents: synthesis, optical properties, metal coordination

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Article information

Article type
Research Article
Submitted
22 Apr 2025
Accepted
07 Jun 2025
First published
12 Jun 2025
This article is Open Access
Creative Commons BY license

Inorg. Chem. Front., 2025, Advance Article

Electron-rich phenanthroline bearing N-heterocyclic imine substituents: synthesis, optical properties, metal coordination

J. H. Franzen, X. Zhou, K. Biv, A. Ajò, A. Mencke, L. F. B. Wilm, M. Seidl, T. S. Hofer, L. De Cola, P. Brüggeller, M. E. Thompson and F. Dielmann, Inorg. Chem. Front., 2025, Advance Article , DOI: 10.1039/D5QI00957J

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