Nanoporous three-dimensional networks topologically related to Cooperite from the self-assembly of copper(I) centres and the "‘square-planar’' building block 1,2,4,5-tetracyanobenzene

Abstract

The deliberate assembly of a Cu^I 3D coordination network with the Cooperite (PtS) topology, namely [Cu(µ₄-TCNB)][PF₆] 1, has been accomplished by using the pseudo-square-planar building block 1,2,4,5-tetracyanobenzene (TCNB). It has been obtained by reacting [Cu(NCMe)₄][PF₆] with TCNB (in molar ratio 1:1) in solvent mixtures of CH₂Cl₂ and of a poorly basic solvent, like ethanol, isopropanol, benzyl alcohol or acetone. The crystals are orthorhombic, space group Cccm, with a=8.157(1), b=18.634(2), c=11.613(1) Å, Z=4. The framework is based on tetrahedral Cu^I centres and tetradentate µ₄-TCNB ligands and presents cavities containing guest solvent molecules. On performing the same reaction in CH₂Cl₂–THF a 3D three-connected polymeric species, [Cu(µ₃-TCNB)(THF)][PF₆] 2, is obtained. Compound 2 gives monoclinic crystals, space group P2₁/c, with a=21.617(2), b=11.127(3), c=16.294(2) Å, β=111.61(2)°, Z=8. In 2 the TCNB ligands are tridentate and the copper centres achieve a tetrahedral coordination on forming a bond with a THF molecule. The network presents an unprecedented topology, (8²10)-b, and the crystals undergo, by thermal activation, an unusual crystal-to-crystal transformation, losing the THF molecules to give the same frame as 1.