Computational (DFT) and Experimental (EXAFS) Study of the Interaction of [Ir(IMes)(H)2(L)3] with Substrates and Co‐substrates Relevant for SABRE in Dilute Systems1. Issue 29 (12th June 2015)

• Record Type: Journal Article
• Authors: van Weerdenburg, Bram J. A.; Engwerda, Anthonius H. J.; Eshuis, Nan; Longo, Alessandro; Banerjee, Dipanjan; Tessari, Marco; Guerra, Célia Fonseca; Rutjes, Floris P. J. T.; Bickelhaupt, F. Matthias; Feiters, Martin C.
• Is Part Of: Chemistry. Volume 21:Issue 29(2015)
• Page Start: 10482
• Page End: 10489
• Publication Date: 2015-06-12
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201500714
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Signal amplification by reversible exchange (SABRE) is an emerging hyperpolarization method in NMR spectroscopy, in which hyperpolarization is transferred through the scalar coupling network of <italic>para‐</italic>hydrogen derived hydrides in a metal complex to a reversibly bound substrate. Substrates can even be hyperpolarized at concentrations below that of the metal complex by addition of a suitable co‐substrate. Here we investigate the catalytic system used for trace detection in NMR spectroscopy with [Ir(IMes)(H)₂(L)₃]⁺ (IMes=1, 3‐dimesitylimidazol‐2‐ylidene) as catalyst, pyridine as a substrate and 1‐methyl‐1, 2, 3‐triazole as co‐substrate in great detail. With density functional theory (DFT), validated by extended X‐ray absorption fine structure (EXAFS) experiments, we provide explanations for the relative abundance of the observed metal complexes, as well as their contribution to SABRE. We have established that the interaction between iridium and ligands <italic>cis</italic> to IMes is weaker than that with the <italic>trans</italic> ligand, and that in mixed complexes with pyridine and triazole, the latter preferentially takes up the <italic>trans</italic> position.</p> </abstract>