Conformational studies on chiral rhodium complexes by ECD and VCD spectroscopy
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Updated: Jun 8, 2026

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Gábor Szilvágyi1, Zsuzsa Majer, Elemér Vass
1Laboratory for Chiroptical Structure Analysis, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary.
Abstract:
This article reports vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopic studies in acetonitrile on the chiral Rh(2)(O-Phe-Cbz)(1)(OAc)(3) and Rh(2)(O-Phe-Ac)(1)(OAc)(3) complexes (abbreviated Rh(2)Z(1) and Rh(2)Ac(1) , respectively; Phe, L-phenylalanine; Cbz, benzyloxycarbonyl; Ac, acetyl) supported by theoretical calculations. The ECD spectra of the complexes depend on temperature that indicates the conformational mobility of the chiral ligands. Calculations of the VCD spectra were performed at ab initio (DFT) level of theory using Gaussian 03 [B3LYP functional combined with the LANL2DZ basis set for the dirhodium core and the 6-31G(d) basis set for other atoms]. The population-weighted sums of the computed VCD spectra of the conformers are in excellent agreement with the experimental VCD spectra. The combination of the VCD and ECD spectroscopic methods led us to the structural characterization of the complexes.
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Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...

