A rare class of dinuclear double-stranded helicates having tetrahedral metal centres with formulae [Co2(L(1))2]·2(CH3CN) (1), [Co2(L(2))2]·6(CH3CN) (2), [Zn2(L(1))2]·2(CH3CN)·(CH3OH) (3) and [Zn2(L(2))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.