Anion Recognition by a Pincer-Type Host Constructed from Two Polyamide Macrocyclic Frameworks Jointed by a Photo-Addressable Azobenzene Switch.

A sterically crowded light-responsive host was synthetized with a 93% yield by applying a post-functionalization protocol utilizing the double amidation of 4,4'-azodibenzoyl dichloride with a readily available 26-membered macrocyclic amine. X-ray structures of two hydrates of - demonstrate a very different alignment of the azobenzene linkage, which is involved in -shape or parallel-displaced π⋯π stacking interactions with the pyridine-2,6-dicarboxamide moieties from the macrocyclic backbone. Despite the rigidity of the macrocyclic framework, which generates a large steric hindrance around the azobenzene chromophore, the host retains the ability to undergo a reversible ⟷ isomerization upon irradiation with UVA (368 nm) and blue (410 nm) light.

Tuning Anion-Binding Properties of 22-Membered Unclosed Cryptands by Structural Modification of the Lariat Arm.

A series of 22-membered unclosed cryptands end-capped with intra-annular methyl (), phenyl (), --butylphenyl (), and -nitrophenyl () amide substituents (lariat arm) were synthesized to elucidate the effect of steric and electronic factors on their anion recognition behavior. The H NMR titrations in DMSO- with 0.5% water reveal enhanced selectivity for HPO vs Cl and PhCO .