Auxiliary ligand-induced structural diversities of octacyanometalate-based heterobimetallic coordination polymers towards diverse magnetic properties

Abstract

Three octacyanometalate-based bimetallic coordination polymers (CPs), {[μ₄-M^V(CN)₈][Co(DMF)₄]₂(ClO₄)}_n (M = W CP-1, Mo CP-2) and {[μ₄-W^IV(CN)₈]Co₂(azpy)₄}_n CP-3, were synthesized in the absence (for CPs 1 and 2) or presence (for CP-3) of auxiliary ligand 4,4′-azopyridine (azpy), respectively. CPs 1 and 2 exhibit the same three-dimensional (3D) polymeric cation frameworks with [ClO₄]⁻ as the counterions, while CP-3 displays a porous 3D framework in an unusual 2-nodal (4,6)-connected 4,6T155 topology with point symbol as {4²·6⁴}{4⁶·6⁴·7·8⁴}₂. Notably is that octacyanometalate [W^V(CN)₈]³⁻ has been reduced into [W^IV(CN)₈]⁴⁻ during the synthetic process of CP-3. The magnetic investigations indicate that CP-1 exhibits the typical ferromagnetic property due to the ferromagnetic coupling between W(V) and Co(II) spin centers, while CP-3 displays the weak ferromagnetic interaction at low temperature, which is consistent with the valence change of W center in CP-3.