Directing the Morphology, Packing, and Properties of Chiral Metal–Organic Frameworks by Cation Exchange**

Abstract

We show that metal-organic frameworks, based on tetrahedral pyridyl ligands, can be used as a morphological and structural template to form a series of isostructural crystals having different metal ions and properties. An iterative crystal-to-crystal conversion has been demonstrated by consecutive cation exchanges. The primary manganese-based crystals are characterized by an uncommon space group (P622). The packing includes chiral channels that can mediate the cation exchange, as indicated by energy-dispersive X-ray spectroscopy on microtome-sectioned crystals. The observed cation exchange is in excellent agreement with the Irving-Williams series (Mn < Fe < Co < Ni < Cu > Zn) associated with the relative stability of the resulting coordination nodes. Furthermore, we demonstrate how the metal cation controls the optical and magnetic properties. The crystals maintain their morphology, allowing a quantitative comparison of their properties at both the ensemble and single-crystal level.

Energy transport in dichromic metallo-organic crystals: selective inclusion of spatially-resolved arrays of donor and acceptor dyes in different nanochannels

“…Colorless cadmium-based crystals with the ligand, AdDB, were prepared as host matrix for the assembly of new materials for optical applications. Coordination of this ligand to bivalent cadmium cations resulted in the same coordination structure as recently found for other first row metals (22)(23)(24)(25)(26), but these new crystals are highly transparent (similar to the less stable manganese-based crystals) (26).…”

“…The phase purity was confirmed by fitting the measured powder X-ray diffraction (PXRD) diffraction patterns of bulk samples with one simulated from the crystal structure (Figure 1C). These crystals are part of our series of isostructural, chiral metal-organic frameworks grown from achiral components (22)(23)(24)(25)(26). The propellor-type arrangement of four coordinated pyridine units from four different ligands around the bivalent cadmium cations imparts a chiral arrangement on both the coordination nodes and the channels.…”

“…We have demonstrated recently that the organic ligand, AdDB (21), shown in Scheme 1 and similar systems form isostructural crystals with first row, bivalent metals (i.e., manganese, iron, cobalt, nickel, copper and zinc) (22)(23)(24)(25)(26). The crystals have two types of continuous and chiral channels aligned along the crystallographic c-axis.…”

“…Previous studies have shown that the uniformity in the size and shape of isostructural crystals is higher than that of crystals formed at room temperature using the slow diffusion of one solvent into another (26). Therefore, solvothermal reaction conditions were here used to generate thermodynamically-favored, stable structures that are suitable for post-assembly functionalization.…”

Energy Transport in Dichroic Metallo‐organic Crystals: Selective Inclusion of Spatially Resolved Arrays of Donor and Acceptor Dyes in Different Nanochannels**

“…We have demonstrated recently that the organic ligand, AdDB , [33] shown in Scheme 1 and similar systems form isostructural crystals with first row, bivalent metals (i.e., manganese, iron, cobalt, nickel, copper and zinc) [34–38] . The crystals have two types of continuous and chiral channels aligned along the crystallographic c ‐axis.…”