Two Hg(II)-Based Macrocycles Offering Hydrogen Bonding Cavities: Influence of Cavity Structure on Heterogeneous Catalysis

Abstract

We present the synthesis and characterization of two Hg-macrocycles offering H-bonding based cavities of varying dimensions. Both Hg-macrocycles illustrate a noteworthy difference in their catalytic performance that has been related to their cavity structures.

Half-Sandwich Ruthenium Complexes of Amide-Phosphine Based Ligands: H-Bonding Cavity Assisted Binding and Reduction of Nitro-substrates

“…Both Ru­(II) ions in 1 exhibited a six-coordinate distorted octahedral geometry. The Ru–P, Ru–Cl, and Ru– p -cymene bond distances were comparable to the literature examples. ,, Importantly, two Ru­(II) ions are coordinated in such a way that the pyridine-2,6-dicarboxamide based pincer cavity of the ligand remained intact. , …”

“…Notably, the presence of the water molecule within the pincer cavity forces one of the RuCl 2 fragments facing inward. Importantly, existence of a H 2 O molecule H-bonded within the pincer cavity of 1 suggests the possibility of a suitable substrate being held in place closer to the Ru­(II) center(s) and such a situation may help in the catalysis (vide infra) …”

“…Both in complexes 1 and 2 , the presence of a pyridine-2,6-dicarboxamide based pincer cavity presenting H-bonding groups suggested its ability to potentially interact or bind a substrate closer to the metal centers; ,, therefore, substrate binding was investigated. The substrate binding was further supported by the molecular docking studies.…”

“…Our group has also been working on placing various H-bonding based functional groups in coordination complexes as well as in coordination polymers . We have shown that such H-bonds control the recognition events. , We have also illustrated that H-bonding pocket in the vicinity of a Lewis acidic metal orients a substrate before the Lewis acidic metal assisted catalysis. , …”

Selective Detection of Picric Acid and Pyrosulfate Ion by Nickel Complexes Offering a Hydrogen-Bonding-Based Cavity

“…Further evidence were obtained from the molecular docking studies for all three complexes to that of PA (Figure 7; Figures S37 and S38). 86 The docked structure of the picrate ion with complex 3 showed that the O phenol atom of the picrate ion coordinated with the Ni(II) ion with a bond distance of 2.353 Å. In addition, one of the protonated benzimidazolium rings created an H-bond with the O phenol atom of the picrate ion (N5−H1••• O picrate ) with a N•••O heteroatom separation of 3.829 Å.…”