The Honeysuckle and the Bindweed Revisited: Synthesis and Stereochemistry of Extended Helical Structures from Coordination Complexes

We report structural studies of a chiral tridentate ligand which forms helical cubanes with cobalt(II) and manganese(II). A quadruple helicate with (P)-chirality is obtained using a (S)-ligand with cobalt(II) but the ligand binds manganese(II) in one of two possible orientations and either (P)- or (M)-quadruple helicates may be observed for a given ligand enantiomer. The helicates may be linked into extended structures by p-nitrobenzoate capping ligands which show stacking interactions with neighbouring complexes. With cobalt(II) we find an extended helical structure with (M)-chirality linking helicates which themselves have (P)-chirality. With manganese(II) we observe a remarkable structure with extended (M)-helices coexisting with extended (P)-helices. image

Automated summary

This study investigates the structural properties of a chiral ligand forming helical cubanes with cobalt(II) and manganese(II). It is found that a (P)-quadruple helicate can be obtained with a (S)-ligand and cobalt(II). However, when the ligand binds to manganese(II), there are two possible orientations, resulting in the observation of either (P)- or (M)-quadruple helicates for a given ligand enantiomer. The helicates can be linked into extended structures by p-nitrobenzoate capping ligands, which exhibit stacking interactions with neighboring complexes. Interestingly, the study reveals the presence of extended (M)-helices coexisting with extended (P)-helices when manganese(II) is used.