Self-organization of K ⁺-crown ether derivatives into double-columnar arrays controlled by supramolecular isomers of hydrogen-bonded anionic biimidazolate Ni complexes

Anionic tris (biimidazolate) nickelate (II) ([Ni(Hbim) ₃] ^-), which is a hydrogen-bonding (H-bonding) molecular building block, undergoes self-organization into honeycomb-sheet superstructures connected by complementary intermolecular H-bonds. The crystal obtained from the stacking of these sheets is assembled into channel frameworks, approximately 2 nm wide, that clathrate two cationic K ⁺-crown ether derivatives organised into one-dimensional (1D) double-columnar arrays. In this study, we have shown that all five cationic guest-included crystals form nanochannel structures that clathrate the 1-D double-columnar arrays of one of the four types of K ⁺-crown ether derivatives, one of which induces a polymorph. This is accomplished by adaptably fitting two types of anionic [Ni(Hbim) ₃] ^- host arrays. One is a Δ Λ Δ Λ Δ Λ network with H-bonded linkages alternating between the two different optical isomers of the Δ and Λ types with flexible H-bonded [Ni(Hbim) ₃] ^-. The other is a Δ Δ Δ Λ Λ Λ network of a racemate with 1-D H-bonded arrays of the same optical isomer for each type. Thus, [Ni(Hbim) ₃] ^- can assemble large cations such as K ⁺ crown-ether derivatives into double-columnar arrays by highly recognizing flexible H-bonding arrangements with two host networks of Δ Λ Δ Λ Δ Λ and Δ Δ Δ Λ Λ Λ .