Thioamide Pincer Ligands with Charge Versatility

This paper reports the synthesis and characterization of three complexes, two palladium and one platinum, with 2,6-bis-thioamido-phenyl and 2,6-bis-thioamido-pyridine ligands. The ligands show internal charge versatility by losing protons from a phenyl CH (I) or from amide NH's (II and III). The complexes were also examined as Heck catalysts, and the palladacycle, I, was found to be more effective compared to the others. The crystal structures of the complexes are also reported

Anion Binding Motifs: Topicity and Charge in Amidocryptands

An expanded amidocryptand with propyl linkages provides multitopic sites for binding anions and water molecules. Upon quaternization of the two bridgehead amines, the molecular shape changes from an inverted Y to that of a bowl, which is filled with water and topped by the anion

Anion Binding Motifs: Topicity and Charge in Amidocryptands

An expanded amidocryptand with propyl linkages provides multitopic sites for binding anions and water molecules. Upon quaternization of the two bridgehead amines, the molecular shape changes from an inverted Y to that of a bowl, which is filled with water and topped by the anion

Cyclophane Capsule Motifs with Side Pockets

Neutral and charged multitopic cyclophane-capped anion hosts connected by three or four diamide/monoamine chains and a decomposition product with two chains have been synthesized and characterized. The chains in the two former hosts fold together to form one or two binding pockets, respectively, and FHF− and several phosphate complexes have been obtained with the anions nestled in these pockets. The decomposition product also shows propensity for binding dicarboxylates, as evidenced by an isophthalate crystal structure

Fluoride: Solution- and Solid-State Structural Binding Probe

Solid-state and solution studies were performed to determine if F− is encapsulated by anion hosts in both media. X-ray crystal structure determinations were compared with both 1H and 19F solution NMR data. Three hosts were studied: (1) two polyamide hosts, one with isophthaloyl spacers and the other with pyridine spacers, and (2) a polythioamide host with pyridine spacers. Binding studies showed that the pyridine-containing amide cryptand shows the highest affinity (Ka > 105 in DMSO-d6), with the other hosts at least a factor of 10 lower. All of the cryptands appear to encapsulate F− in solution, where a deuterium-exchange reaction with DMSO-d6 can be monitored by 19F NMR. Four crystal structures are reported and compared: two for the pyridine-containing free base hosts and two for encapsulated F− complexes of the two amide-based cryptands

Fluoride: Solution- and Solid-State Structural Binding Probe

Solid-state and solution studies were performed to determine if F− is encapsulated by anion hosts in both media. X-ray crystal structure determinations were compared with both 1H and 19F solution NMR data. Three hosts were studied: (1) two polyamide hosts, one with isophthaloyl spacers and the other with pyridine spacers, and (2) a polythioamide host with pyridine spacers. Binding studies showed that the pyridine-containing amide cryptand shows the highest affinity (Ka > 105 in DMSO-d6), with the other hosts at least a factor of 10 lower. All of the cryptands appear to encapsulate F− in solution, where a deuterium-exchange reaction with DMSO-d6 can be monitored by 19F NMR. Four crystal structures are reported and compared: two for the pyridine-containing free base hosts and two for encapsulated F− complexes of the two amide-based cryptands

Tricyclic Host for Linear Anions

A tricyclic host for anions consisting of two tetraamide monocycles attached by two ethylene chains was designed and synthesized. Structural and binding results indicate that the receptor is selective for linear triatomic anions. Crystallographic data for two hydrated free bases, along with FHF−, N3−, and SO42− complexes indicate that there are at least two preferred gross conformations for the host, one of which possesses pseudo-D2 symmetry and the other pseudo-C2h symmetry. Both FHF− and N3− are encapsulated in the pseudo-D2 symmetric complex, bridging the two tetraamido macrocyclic halves. The pseudo-C2h octahydrate structure shows an ice-like H-bonded (H2O)6 array of water molecules embedded in the host cavity. The SO42− structure has a nearly superimposable host conformation to the octahydrate but with the SO42− anions lying outside the host. Binding studies in DMSO-d6 indicate selectivity for FHF−, with lesser affinity for other inorganic anions

Thioamide Pincer Ligands with Charge Versatility

This paper reports the synthesis and characterization of three complexes, two palladium and one platinum, with 2,6-bis-thioamido-phenyl and 2,6-bis-thioamido-pyridine ligands. The ligands show internal charge versatility by losing protons from a phenyl CH (I) or from amide NH's (II and III). The complexes were also examined as Heck catalysts, and the palladacycle, I, was found to be more effective compared to the others. The crystal structures of the complexes are also reported

The Influence of Amine Functionalities on Anion Binding in Polyamide-Containing Macrocycles

Mixed amide/amine macrocyclic anion hosts of varying sizes and with different amine substituents have been synthesized and characterized. Host 2, containing a 28-membered ring and secondary amines, has shown selective binding for HSO4− over other oxo anions and halides in DMSO-d6 using NMR titrations. Crystal structures of SO42−, HPO42−, H2PO4−, and H2P2O72− with the 28-membered ring hosts indicate different macrocyclic conformations depending on the N-substituent. Anion affinities appear to be correlated with macrocycle conformation

Chemistry and Structure of a Host–Guest Relationship: The Power of NMR and X‑ray Diffraction in Tandem

An amine/amide mixed covalent organic tetrahedral cage <b>1</b> (<i><b>H</b></i>_<b>12</b>) was synthesized and characterized. The <i><b>H</b></i>_<b>12</b> cage contains 12 amide NH groups plus four tertiary amine N groups, the latter of which are positioned in a pseudo-tetrahedral array. Crystallographic findings indicate that the tetrahedral host can adopt either a pseudo-<i>C</i>₃ symmetric “compressed tetrahedron” structure, or one in which there are two sets of three stacked pyridine units related by a pseudo-S₄ axis. The latter conformation is ideal for encapsulating small pentameric clusters, either a water molecule or a fluoride ion surrounded by a tetrahedral array of water molecules, i.e., H₂O·4H₂O or F^–·4H₂O, as observed crystallographically. In solution, however, ¹⁹F NMR spectroscopy indicates that <i><b>H</b></i>_<b>12</b> encapsulates fluoride ion through direct amide hydrogen bonding. By collectively combining one-dimensional ¹H, ¹³C, and ¹⁹F with two-dimensional ¹H–¹H COSY, ¹H–¹³C HSQC, and ¹H–¹⁹F HETCOR NMR techniques, the solution binding mode of fluoride can be ascertained as consisting of four sets of independent structural subunits with <i>C</i>₃ symmetry. A complex deuterium exchange process for the fluoride complex can also be unraveled by multiple NMR techniques