TTF salts of optically pure cobalt pyridine amidates; detection of soluble assemblies with stoichiometry corresponding to the solid state

Abstract

Optically pure anionic complexes of pyridinecarboxamide ligands, N²,N⁶-bis((R)-α-methylbenzyl)pyridine-2, 6-dicarboxamide H₂(R,R-L¹) and N²,N⁶-bis((S)-1-methoxypropan-2-yl)pyridine-2, 6-dicarboxamide H₂(S,S-L²) have been synthesised and fully characterised. The complexes: (18-crown-6)K[Co^III(R,R-L¹)₂], (18-crown-6)K[Fe^III(R,R-L¹)₂] and K[Co^III(S,S-L²)₂]·3H₂O show interesting extended structures from 0D discrete units through 1D zigzag chains to 2D honeycomb layers. The complex anions were used in the synthesis of radical cation salts with tetrathiafulvalene (TTF). The salts (TTF)[Co^III(R,R-L¹)₂] and (TTF)[Co^III(S,S-L²)₂]·EtOAc were characterised by single crystal X-ray diffraction and conductivity measurements. Both compounds comprise mono-oxidised TTF molecules and exhibit similar layered structures with no direct TTF stacking but in which phenyl substituents from the complex anion or co-crystallised ethyl acetate alternate with TTF⁺ units. Solution spectroscopic and cyclic voltammetric evidence points to the formation of soluble assemblies between TTF⁺ and the counterion which correspond to the stoichiometry observed by crystallography and other methods in the solid state.