Controlling Second Coordination Sphere Effects in Luminescent Ruthenium Complexes by Means of External Pressure

Andrea Pannwitz; Stéphanie Poirier; Nicolas Bélanger-Desmarais; Alessandro Prescimone; Oliver S Wenger; Christian Reber

doi:10.1002/chem.201800703

Controlling Second Coordination Sphere Effects in Luminescent Ruthenium Complexes by Means of External Pressure

Chemistry. 2018 Jun 4;24(31):7830-7833. doi: 10.1002/chem.201800703. Epub 2018 May 9.

Authors

Andrea Pannwitz¹, Stéphanie Poirier², Nicolas Bélanger-Desmarais², Alessandro Prescimone³, Oliver S Wenger¹, Christian Reber²

Affiliations

¹ Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland.
² Département de chimie, Université de Montréal, Montréal, Québec, H3C 3J7, Canada.
³ Department of Chemistry, University of Basel, Mattenstrasse 24a BPR 1096, 4058, Basel, Switzerland.

PMID: 29682809
DOI: 10.1002/chem.201800703

Abstract

Two luminescent heteroleptic Ru^II complexes with a 2,2'-biimidazole (biimH₂ ) ligand form doubly hydrogen-bonded salt bridges to 4-sulfobenzoate anions in single crystals. The structure of one of these cation-anion adducts shows that the biimH₂ ligand is deprotonated. Its ³ MLCT luminescence band does not shift significantly under the influence of an external hydrostatic pressure, a behavior typical for these electronic transitions. In contrast, hydrostatic pressure on the other crystalline cation-anion adduct induces a shift of proton density from the peripheral N-H groups of biimH₂ towards benzoate, leading to a pronounced redshift of the ³ MLCT luminescence band. Such a significant and pressure-tunable influence from an interaction in the second coordination sphere is unprecedented in artificial small-molecule-based systems.

Keywords: high-pressure chemistry; hydrogen bonds; luminescence; noncovalent interactions; supramolecular chemistry.