Macrocyclic coordination chemistry

Abstract

Short-lived radioactive isotopes (SLRs) with half-lives between 0.1 to 100 Myr can be used to probe the origin of the Solar System. In this work, we examine the core-collapse supernovae production of the 15 SLRs produced: 26

Metallathiacrown Ethers: Synthesis and Characterization of Transition-Metal Complexes Containing α,ω-Bis(phosphite)-Polythioether Ligands and an Evaluation of Their Soft Metal Binding Capabilities

“…This was purified first by column chromatography using silica gel as the stationary phase and a 4/1 hexanes/ethyl acetate mixture as the eluent followed by recrystallization from DCM/hexanes to yield 0.256 g (63.5%) of analytically pure 1 as colorless crystals. 31 (2). A solution of 0.228 g (0.760 mmol) of cis-Mo(CO) 4 (nbd) in dry DCM was added dropwise with stirring to a solution of 0.500 g (0.759 mmol) of L2 in dry DCM.…”

“…4−10 The heteroatom donor sites in these compounds have also been varied to enhance selectivities for specific classes of metal cations and metal-containing small molecules. For instance, hard metals such as the alkali metals show an increased selectivity for hard donor atoms such as oxygen (crown ether) 1 and nitrogen (azacrown ether), 2,11 whereas metals such as those found in the fifth and sixth rows of the periodic table more strongly bind to soft donor atoms such as sulfur (thiacrown ether). 12−28 Due to their soft donor capability, thiacrown ethers, in particular, have found a wide variety of applications from toxic heavy metal sensing and removal agents to nanomaterials and anticancer agents.…”

“…Due to their excellent selectivities for binding small molecules and metal cations, crown ethers have been studied for many years by both organic and inorganic chemists alike. − Modification of the crown ether ring with various functional groups has been used to provide additional donor sites, increase selectivity for specific substrates, or add a spectroscopic probe. − The heteroatom donor sites in these compounds have also been varied to enhance selectivities for specific classes of metal cations and metal-containing small molecules. For instance, hard metals such as the alkali metals show an increased selectivity for hard donor atoms such as oxygen (crown ether) and nitrogen (azacrown ether), , whereas metals such as those found in the fifth and sixth rows of the periodic table more strongly bind to soft donor atoms such as sulfur (thiacrown ether). − Due to their soft donor capability, thiacrown ethers, in particular, have found a wide variety of applications from toxic heavy metal sensing and removal agents to nanomaterials and anticancer agents. − …”

Amide conjugates of the DO3A‐N‐(α‐amino)propionate ligand: leads for stable, high relaxivity contrast agents for MRI?

“…Nonetheless, the high relaxivities predicted theoretically have not yet been achieved in spite of the tremendous efforts and developments in the field (7). The main approaches to enhancing detection sensitivity involve optimizing the relaxivity of individual chelates, clustering a high number of (high relaxivity) chelates into (bio)macromolecular carriers or self-assembling monomeric chelates into supramolecular structures, and directing chelate constructs to the sites of interest by attaching targeting moieties recognized specifically by cellular receptors (6,8). All these approaches require chemical modification of the basic chelator structure in order to introduce 'handles' for chemical functionalization.…”