Issue 16, 2020

HERFD-XANES probes of electronic structures of ironII/III carbene complexes

Abstract

Iron centered N-heterocyclic carbene (Fe-NHC) complexes have shown long-lived excited states with charge transfer character useful for light harvesting applications. Understanding the nature of the metal–ligand bond is of fundamental importance to rationally tailor the properties of transition metal complexes. The high-energy-resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) has been used to probe the valence orbitals of three carbene complexes, [FeII(bpy)(btz)2](PF6)2 (bpy = 2,2′-bipyridine, btz = 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene)), [FeIII(btz)3](PF6)3, and [FeIII(phtmeimb)2]PF6 (phtmeimb = [phenyl(tris(3-methylimidazol-2-ylidene))borate]). The multiconfigurational restrict active space (RAS) approach has been used to simulate the metal K pre-edge X-ray absorption spectroscopy of these carbene complexes, and have reproduced the metal K pre-edge spectral features in terms of relative intensity and peak positions. The evident intensity difference between the FeII and the other two FeIII complexes has been elucidated with different intensity mechanisms in the transition. The smaller splitting between the t2g and eg character peak for [FeIII(btz)3](PF6)3 has been observed in the experimental measurements and been reproduced in the RAS calculations. The results show how the combination of experimental HERFD-XANES measurements and ab initio RAS simulations can give quantitative evaluation of the orbital interactions between metal and ligands for such large and strongly interacting systems and thus allow to understand and predict properties of novel complexes.

Graphical abstract: HERFD-XANES probes of electronic structures of ironII/III carbene complexes

Supplementary files

Article information

Article type
Paper
Submitted
21 Nov 2019
Accepted
18 Feb 2020
First published
16 Apr 2020
This article is Open Access
Creative Commons BY-NC license

Phys. Chem. Chem. Phys., 2020,22, 9067-9073

HERFD-XANES probes of electronic structures of ironII/III carbene complexes

M. Guo, O. Prakash, H. Fan, L. H. M. de Groot, V. F. Hlynsson, S. Kaufhold, O. Gordivska, N. Velásquez, P. Chabera, P. Glatzel, K. Wärnmark, P. Persson and J. Uhlig, Phys. Chem. Chem. Phys., 2020, 22, 9067 DOI: 10.1039/C9CP06309A

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