Integration of Trinuclear Triangle Copper(II) Secondary Building Units in Octacyanidometallates(IV)-Based Frameworks

The design and synthesis of high-dimensional materials based on secondary building blocks (SBUs) play a pivotal role in the further development of functional molecular materials. Herein, the self-assembly of Cu­(II) ions, pyrazole (Hpz), and octacyanidometallate­(IV) anions in the presence of water produced two new isostructural three-dimensional systems {[Cu₃(μ₃-OH)­(μ-pz)₃(H₂O)₃]₂[M­(CN)₈]}·nH₂O (M = W, 1, and Mo, 2). 1 and 2 consist of trinuclear triangle copper­(II) (TTC) SBUs and octacyanidometallates­(IV). At room temperature, both assemblies display strong antiferromagnetic interactions within the TTC entities with an average Cu^II···Cu^II isotropic magnetic coupling constant of about −145 cm^–1. Moreover, a detailed analysis of magnetic data revealed the presence of spin frustration with antisymmetric magnetic exchange-coupling constants of around +32 and +46 cm^–1 for 1 and 2, respectively. Finally, quantum chemical calculations explained their magnetic and optical properties.