Tetrahedral MII based binuclear double-stranded helicates: single-ion-magnet and fluorescence behaviour

Abstract

A rare class of dinuclear double-stranded helicates having tetrahedral metal centres with formulae [Co₂(L¹)₂]·2(CH₃CN) (1), [Co₂(L²)₂]·6(CH₃CN) (2), [Zn₂(L¹)₂]·2(CH₃CN)·(CH₃OH) (3) and [Zn₂(L²)₂]·4(CH₃CN) (4) were synthesized and characterized. Detailed dc and ac magnetic susceptibility measurements reveal the presence of field induced slow magnetic relaxation behaviour in high spin tetrahedral Co^II centres with an easy-plane magnetic anisotropy. Complexes 1 and 2 are the rare examples of transition metal based helicates showing such behaviour. Furthermore, 3 and 4 exhibit fluorescence emission in different solvents that are analyzed in terms of fluorescence quantum yields and lifetimes.