One Dense and Two Open Chiral Metal−Organic Frameworks:  Crystal Structures and Physical Properties

Three 3D robust homochiral helical coordination polymers, [Cu(2,2‘,3,3‘-H₂odpa)(bpy)] (1), {[Ni₄(2,2‘,3,3‘-odpa)₂(bpy)₄(H₂O)₄]·(H₂O)₁₆} (2), and {[Co₄(2,2‘,3,3‘-odpa)₂(bpy)₄(H₂O)₄]·(H₂O)₁₄} (3), have been hydrothermally synthesized from a flexible ligand of 2,2‘,3,3‘-odpda (2,2‘,3,3‘-oxydiphthalic dianhydride). Compound 1 crystallized in space group P3₁21 and has a rare chiral dense qzd 7.⁵9 topology that incorporates single helical substructures with the same accessibility, whereas compounds 2 and 3 crystallized in the space group C2 and possessed isostructural 3D chiral open frameworks based on the homochiral 2D sheets and 4,4‘-bpy pillars. TGA and PXRD analyses show that the porous framework of 2 is stable after the removal of solvent water molecules. In contrast, 3 changed its structure to an amorphous one because of the simultaneous loss of solvent and coordination water molecules. 1 is nearly paramagnetic, whereas weak ferromagnetic interactions between M(II) (M = Ni, Co) ions have been found in 2 and 3.