Lanthanide chloride clusters, LnxCl3x+1−, x = 1–6: an ion mobility and DFT study of isomeric structures and interconversion timescales†

Ion mobility spectrometry (IMS) (also including IMS–IMS measurements) as well as DFT calculations have been used to study isomer distributions and isomer interconversion in a range of electrospray-generated lanthanide chloride cluster anions, Ln_xCl_3x+1⁻ (where x = 1–6, and Ln corresponds to the 15 lanthanide elements (except for radioactive Pm)). Where measurement and structural rearrangement timescales allow, we obtain almost quantitative agreement between experiment and theory thus confirming isomer predictions and reproducing isomer intensity ratios. Ln_xCl_3x+1⁻ structures reflect strong ionic bonding with limited directionality. Ring and chain motifs dominate for smaller clusters while for larger clusters more compact three-dimensional structures become favourable. At cluster sizes with two or more closely lying isomers, the lanthanide contraction can lead to systematic variations in structure types across the series.