ABSTRACT
A penta-stranded helicate was obtained by combining [Pd(CH3CN)4](BF4)2 with La(NO3)3 and a polydentate ligand. The helicate displays low symmetry, both in solution and in the solid state. A dynamic interconversion between the penta-stranded helicate and a symmetrical, four-stranded helicate was achieved by adjustment of the metal-to-ligand ratio.
Subject(s)
Molecular Conformation , LigandsABSTRACT
A water-soluble coordination cage was obtained by reaction of Pd(NO3 )2 with a 1,3-di(pyridin-3-yl)benzene ligand featuring a short PEG chain. The cavity of the metal-organic cage contains one nitrate anion, which is readily replaced by chloride. The apparent association constant for chloride binding in buffered aqueous solution is Ka =1.8(±0.1)×105 â M-1 . This value is significantly higher than what has been reported for other macrocyclic chloride receptors. The heavier halides Br- and I- compete with binding or self-assembly, but the receptor displays very good selectivity over common anions such as phosphate, acetate, carbonate, and sulfate. A further increase of the chloride binding affinity by a factor of 3 was achieved using a fluorinated dipyridyl ligand.
ABSTRACT
Thirteen palladium-ligand assemblies with different structures and topologies were investigated for the ability to bind lithium ions. In one case, the addition of LiBF4 resulted in a profound structural rearrangement, converting a dincluclear [Pd2 L4 ]4+ complex into a low-symmetry [Pd4 L8 ]8+ assembly with two binding pockets for solvated LiBF4 ion pairs. The rearrangement could only be induced by Li+ , indicating highly specific host-guest interactions. A structural analysis of the [Pd4 L8 ]8+ receptor revealed a compact structure with multiple intramolecular interactions, reminiscent of what is seen for natural and synthetic foldamers.
ABSTRACT
The design of structurally defined heteroleptic coordination cages is a challenging task, and only few examples are known to date. Here we describe a selection approach that allowed the identification of a novel hexanuclear Pd cage containing two types of dipyridyl ligands. A virtual combinatorial library of [PdnL2n](BF4)2n complexes was prepared by mixing six different dipyridyl ligands with substoichiometric amounts of [Pd(CH3CN)4](BF4)2. Analysis of the equilibrated reaction mixture revealed the preferential formation of a heteroleptic [Pd6L6L'6](BF4)12 assembly. The complex was prepared on a preparative scale by a targeted synthesis, and its structure was elucidated by single-crystal X-ray diffraction. It features an unprecedented trigonal-antiprismatic cage structure with two triangular Pd3L3 macrocycles bridged by six L' ligands. A related but significantly larger [Pd6L6L'6](BF4)12 cage was obtained by using metalloligands instead of organic dipyridyl ligands.
ABSTRACT
The threat posed by the presence of artificial volatile organic compounds (VOCs) in the environment is a widely acknowledged fact, both for environmental issues and human health concerns. Ever-increasing production requires the continuous development of technologies toward the removal of these substances. In recent years, metal-organic frameworks (MOFs) have shown a great promise toward the capture of VOCs, but their stability in humid conditions still remains a major challenge, thus hindering their widespread development. To tackle this obstacle, we designed a 3-dimensional and porous MOF, named SION-82, for the capture of small aromatic VOCs, relying solely on π-π interactions. SION-82 captures benzene efficiently (107 mg/g) in dry conditions, and no uptake decrease was observed in the presence of high relative humidity for at least six cycles. Unlike HKUST-1 and MOF-74(Co), SION-82 possesses two vital characteristics toward sustainable benzene capture under humid conditions: moisture stability and reusability. In addition, SION-82 captures benzene under humid conditions more efficiently compared to the hydrolytically stable UiO-66, highlighting the impact of having an active site for benzene capture that is not affected by water. SION-82 can additionally capture other aromatic VOCs, showing pyridine and thiophene uptake capacities of 140 and 160 mg/g, respectively.
