Coordination Polymers Driven by Carboxy Functionalized Picolinate Linkers: Hydrothermal Assembly, Structural Multiplicity, and Catalytic Features
Hongrui Zhang, Jin‐Zhong Gu, Marina V. Kirillova, Alexander M. Kirillov
Abstract
This work explores an N,O-donor dicarboxylic acid, 5-(3-carboxyphenyl)picolinic acid (H2cpic), as an adjustable linker for generating diverse types of coordination polymers (CPs). Eight new compounds were hydrothermally assembled, completely characterized, and formulated as [Mn(μ3-cpic)(H2O)2]n (1), [Cd2(μ3-cpic)(μ4-cpic)(H2O)2]n (2), [Cd(μ4-cpic)]n (3), [Mn(μ-cpic)(phen)(H2O)]n (4), [Zn(μ-cpic)(phen)]n·nH2O (5), [Cd2(μ-cpic)2(phen)2(H2O)]·3H2O (6), [Cd(μ3-cpic)(phen)]n (7), and [Zn2(μ-cpic)2(bipy)(H2O)2]n·4nH2O (8). Products 1–8 were assembled from H2O solutions containing the respective metal(II) chloride salts, H2cpic, NaOH, and an N-donor crystallization mediator (optional: 1,10-phenanthroline, phen; or 2,2′-bipyridine, bipy). The structural types of 1–8 include a dimer complex (6), one-dimensional (1, 4, 5, 7, 8) and two-dimensional (2) CPs, and a three-dimensional (3) metal–organic framework. Hydrothermal reaction temperature, type of metal(II) center, and presence of mediators of crystallization are the factors responsible for structural diversity of 1–8. Thermal behavior, topological features, and catalytic properties of these products were studied. Notably, CP 1 acts as an effective, stable, and recyclable catalyst for the heterogeneous cyanosilylation of different aldehydes under mild conditions, resulting in quantitative conversion of aldehyde substrates to respective cyanohydrin products (99% product yields). Compounds 1–8 expand the usage of H2cpic for the assembly of functional coordination polymers, thus stimulating further research in this swiftly growing field.