Helical dinuclear transition metal complexes with bis(bidentate) [S,N] ligands: synthesis, structural and computational studies

18 April 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


A diprotic bis(β-thioketoimine) ligand featuring a flexible 4,4’-methylbis(aniline) linker, H22, was synthesised via treatment of the corresponding bis(β-ketoimine) with Lawesson’s reagent. Proligand H22 underwent lithiation and coordination with one equivalent of d-block metal(II) chlorides MCl2(THF)x (M = Fe, Co and Zn) to yield a corresponding series of homoleptic dinuclear complexes, [M2(μ-2)2]. X-ray diffraction analysis reveals a tetrahedral geometry for the two metals and a double-stranded helicate structure arising from inter-strand face-face π-stacking. These interactions create a helical ‘twist’ of ca. 70°. Utilising a bulky mononucleating β-thioketoiminate ligand, [3]–, the analogous series of heteroleptic monometallic complexes, [M(3)2] (M = Fe, Co and Zn), were prepared and characterised by spectroscopic, analytical and X-ray diffraction techniques. A comprehensive DFT study of all complexes reveals a stronger M–S bonding compared to M–N due to a higher degree of covalency. Solution magnetic studies and Natural Bonding Orbital calculations are consistent with high-spin tetrahedral Fe(II) and Co(II) centres, and cyclic voltammetry reveals both oxidation and reduction processes are accessible.


Dinuclear complexes
Bis(bidentate) ligands
X-ray crystallography
DFT calculations

Supplementary materials

Electronic Supplementary Information
Experimental details, Additional characterisation data (NMR, MS, CV, IR, XRD), Additional computational data (DFT optimised structures, Comparison between observed and calculated structure, Frontier orbitals using PBE0 and BHandHLYP, Bader analysis, Atomic charges).


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