Ion mobility as a tool to highlight steric effects in coordination complexes with a mono‐metallic center

Introduction

In ion mobility, the collision cross section obtained from arrival time distribution shows generally a smooth increase with mass for a given charge state provided the shape of the ion remains approximatively constant. We present here the behavior of the CCS for ions in which compact ligands (Cl-, Br-, I-) are progressively replaced by ligands occupying a larger volume for the same mass. By this, we hope to analyze the effect of the apparent density of the ligand and the effect of the steric hindrance on the CCS and try to link the observations with the reactivity of the metallic center in the complexes.

Methods

Two types of ion mobility devices (T-wave ion mobility and trapped ion mobility) have been used to compare the effect of the trapping time and the energetic conditions of the ion diffusion process. We measured the CCS after replacement of halogen ligands by carboxylic acid of different size with one or two coordination sites, for different charges state of the cation. To support the data the CCS have been also calculated by the CCS software (imos). The experimental CCS calibration range has been extended to lower mass region (ajouter masse). Break down curve have been obtained by CID using Argon.

Preliminary data

In the case of inorganic ligands (chlorine, bromine, iodine) different trends in the collision cross section (CCS) in terms of m / z, associated with the number of ligands of a complex, suggests a distinction between the tetrahedral, trigonal planar, linear and bent geometries. In the case of complexes based on organic monodentate (carboxylates) and polydentate (oxalate and citrate) ligands, different trends were observed as compared to the inorganic complexes. This is a result of the different in density between halogenated ligands compared to their carboxylate counterparts. The results show changes in the oxidation state of the metal center of the complex either in solution or in the gas phase after activation depending on the nature of the ligand. The CID behavior is used to probe the reactivity of the complexes.

Novel aspect

Ion mobility and CID of inorganic complexes with inorganic and organic ligands of different density.