Issue 43, 2025, Issue in Progress

Influence of ionic liquid composition on surface enrichment of fluorine-free Ru complexes

Abstract

Tailoring the surface composition of ionic liquids (ILs) is a key strategy for enhancing the performance of supported ionic liquid phase (SILP) catalysts. Here, we investigate the interfacial behavior of fluorine-free Ru polypyridyl complexes functionalized with n-nonyl side chains (Ru–C9) dissolved in two ILs with contrasting physicochemical properties, such as hydrophobicity and surface tension, namely [C4C1Im][PF6] and [C4C1Im][OAc]. Using angle-resolved X-ray photoelectron spectroscopy (ARXPS), we show that Ru–C9 complexes undergo pronounced surface enrichment in [C4C1Im][PF6], adopting a buoy-like orientation at the IL/vacuum interface. Surface saturation is achieved at a bulk concentration of 0.12%mol, a regime relevant for efficient SILP catalysis. In contrast, no interfacial enrichment is observed in [C4C1Im][OAc], highlighting the critical role of IL composition, particularly anion identity and surface tension, in governing the surface distribution of metal complexes. These findings provide molecular-level insights into the design of IL-based catalytic systems with optimized interfacial properties.

Graphical abstract: Influence of ionic liquid composition on surface enrichment of fluorine-free Ru complexes

Supplementary files

Article information

Article type
Paper
Submitted
23 Jul 2025
Accepted
18 Sep 2025
First published
30 Sep 2025
This article is Open Access
Creative Commons BY license

RSC Adv., 2025,15, 36137-36144

Influence of ionic liquid composition on surface enrichment of fluorine-free Ru complexes

A. Ceccatto, L. Sanchez Merlinsky, L. M. Baraldo, F. J. Williams, F. Maier and H. Steinrück, RSC Adv., 2025, 15, 36137 DOI: 10.1039/D5RA05316A

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