Transformation of a Chiral Nanoporous Bimetallic Cyano-Bridged Framework Triggered by Dehydration/Rehydration

The syntheses, crystal structures, and adsorption/desorption properties of two novel chiral three-dimensional cyano-bridged bimetallic assemblies, {[Cu(1R,2Rchxn)2]2[Ru(CN)6]·6H2O}∞ (1) and {[Cu(1R,2Rchxn)2]12[Ru(CN)6]6·26H2O}∞ (2) (where 1R,2Rchxn = trans-cyclohexane-(1R,2R)-diamine), are reported. Complex 1 crystallizes in the monoclinic space group C2, with a = 18.9979(11) Å, b = 17.8507(11) Å, c = 15.5853(8) Å, β = 119.062(4)°, V = 4619.9(4) Å3, and Z = 4, while 2 crystallizes in the triclinic space group P1, with a = 13.7183(8) Å, b = 21.3378(12) Å, c = 24.4177(13) Å, α = 68.715(4)°, β = 78.284(4)°, γ = 73.004(5)°, V = 6331.3(6) Å3, and Z = 1. Compounds 1 and 2 can be described as nanoporous cyano-bridged frameworks, in which alternating trans-[Cu-(trans-(1R,2R-chxn)2]2+ cations and [Ru(CN)6]4− anions are linked via CN− bridges, and have three-dimensional 66 diamondoid frameworks. In both structures there are large cavities filled with H2O molecules which show guest-dependent dynamic behavior. The chemical rearrangement of the framework is driven by the loss or addition of water molecules, as proved unequivocally by single-crystal and powder X-ray diffraction analyses. These changes are also fully reversible. The two types of frameworks reported show different behavior upon drying, falling within the category of “recoverable collapsing” and “guest-induced re-formation” framework materials.