Self-assembled hetero-bimetallic coordination cage and cation-clusters with µ2-Cl bridging using a flexible two-arm ferrocene amide linker

Oxidation triggers guest dissociation during reorganization of an FeII 4L6 twisted parallelogram

A three-dimensional FeII 4L6 parallelogram was prepared from ferrocene-containing ditopic ligands. The steric preference of the bulky ferrocene cores towards meridional vertex coordination brought about this new structure type, in which the ferrocene units adopt three distinct conformations. The structure possesses two distinct, bowl-like cavities that host anionic guests. Oxidation of the ferrocene FeII to ferrocenium FeIII causes rotation of the ferrocene hinges, converting the structure to an FeII 1L1 + species with release of anionic guests, even though the average charge per iron increases in a way that would ordinarily increase guest binding strength. The degrees of freedom exhibited by these new structures - derived from the different configurations of the three ligands surrounding a meridional FeII center and the rotation of ferrocene cores - thus underpin their ability to reconfigure and eject guests upon oxidation.

Synthesis and Characterisation of a Cd(II) Complex with a Chiral Framework Constructed from Achiral 1,1′-[bis-3-(3-pyridyl)pyrazol-5-yl]ferrocene via Spontaneous Resolution

The chiral Cd(II) complex {[Cd(L)(CH3COO)2(H2O)]·H2O} n {L = 1,1′-[bis-3-(3-pyridyl)pyrazol-5-yl]ferrocene} has been synthesised. The Cd(II) ion is coordinated by two pyridyl nitrogen atoms, two chelating acetate anions and one water molecule, showing a distorted pentagonal-bipyramidal coordination environment. Each ligand L serves as a bisconnector, bridging two Cd atoms through its two pyridyl moieties, to afford an infinite 1D left-handed helical chain along the a-axis with a short pitch of 5.8761 (9) Å. Moreover, all of the left-handed helical chains are joined by hydrogen bonds to form a left-handed homochiral crystal.

Heterobimetallic metal-complex assemblies constructed from the flexible arm-like ligand 1,1'-bis[(3-pyridylamino)carbonyl]ferrocene: structural versatility in the solid state

The bidentate ferrocenyl sandwich molecule 1,1'-bis[(3-pyridylamino)carbonyl]ferrocene (3-BPFA) has been employed as an organometallic ligand in reactions with a series of transition metal salts to construct heterobimetallic architectures. X-ray crystallographic characterization reveals that the crystal packing of free ligand 3-BPFA induces spontaneous resolution of helical chains via intermolecular hydrogen bonds. By combining the flexibility from the arm-like molecule (3-BPFA) with the variation of the coordination property from different metal ions and/or the different counteranions, five different types of architectures are prepared: one octahedral coordination cage (copper(II) complex 1); two discrete pseudocapsules for combination of chlorine anions (nickel(II) complex 2 and cobalt(II) complex 3); two dimers with metal-metal interactions (silver(I) complexes 4 and 5); one macrocyclic complex (mercury(II) complex 6); and five two-dimensional mixed-metal-organic frameworks (M'-MOFs) (zinc(II), cadmium(II), and mercury(II) complexes 7-11). The structures of all complexes are characterized in detail by IR, elementary analysis, and single-crystal X-ray diffraction analysis. The factors inducing the structure variation among the complexes are discussed by taking account of the coordination geometry of different metal ions, the span angle between the two "arms", and the coordination mode of the 3-BPFA ligand.