Heterotrimetallic Cyanide-Bridged 3d-4d-5d Frameworks Based on a Photomagnetic Secondary Building Unit

[Image: see text] The rational design of coordination frameworks combining more than two different metal ions using a self-assembly approach is challenging because it rarely offers sufficient control over the building blocks at the actual self-assembly stage. In this work, we present a successful two-step strategy toward heterotrimetallic coordination frameworks by employing a new bimetallic [(NC)(7)Mo(IV)-CN-Pt(IV)(NH(3))(4)-NC-Mo(IV)(CN)(7)](4–) secondary building unit (SBU). This anionic moiety has been isolated and characterized as a simple salt with an organic dppipH(2)(2+) cation (dppipH(2))(2)[(NC)(7)Mo(IV)-CN-Pt(IV)(NH(3))(4)-NC-Mo(IV)(CN)(7)]·15H(2)O (1) (dppip = 1,4-di(4-pyridinyl)piperazine). The salt presents a second-order phase transition related to cation conformational change around 250 K and a photomagnetic effect after irradiation with 450 nm light at 10 K. When combined with aqueous solutions of Mn(II) or Cu(II) complexes, it forms either a one-dimensional chain [Mn(II)(dpop)][Mn(II)(dpop)(H(2)O)][(NC)(7)Mo(IV)-CN-Pt(IV)(NH(3))(4)-NC-Mo(IV)(CN)(7)]·36H(2)O (2) (dpop = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) or a photomagnetic two-dimensional honeycomb network [Cu(II)(cyclam)](2)[(NC)(7)Mo(IV)-CN-Pt(IV)(NH(3))(4)-NC-Mo(IV)(CN)(7)]·40.89H(2)O (3) (cyclam = 1,4,8,11-tetraazacyclotetradecane), both characterized by very large cavities in their structure filled with solvent molecules. Both 2 and 3 incorporate three different transition-metal ions and constitute a new family of 3d-4d-5d coordination frameworks. Moreover, compound 3 inherits the photomagnetic properties of the MoPtMo SBU.