Coordination sphere hydrogen bonding as a structural element in metal-organic Frameworks

In the design of new metal-organic frameworks, the constant challenges of framework stability and structural predictability continue to influence ligand choice in favour of well-studied dicarboxylates and similar ligands. However, a small subset of known MOF ligands contains suitable functionality for coordination sphere hydrogen bonding which can provide new opportunities in ligand design. Such interactions may serve to support and rigidity the coordination geometry of mononuclear coordination spheres, as well as providing extra thermodynamic and kinetic stabilisation to meet the challenge of hydrolytic stability in these materials. In this perspective, a collection of pyrazole, amine, amide and carboxylic acid containing species are examined through the lens of (primarily) inner-sphere hydrogen bonding. The influence of these interactions is then related to the overall structure, stability and function of these materials, to provide starting points for harnessing these interactions in future materials design.

Anti-cancer and anti-inflammatory activities of a new family of coordination compounds based on divalent transition metal ions and indazole-3-carboxylic acid

A new family of mononuclear coordination compounds has been synthetized and characterized: [M(3-ind)₂(H₂O)₂] (M = Co (1), Ni (2), Zn (3), Fe (4), Mn (5); 3-ind = indazole-3-carboxylate). These materials are mononuclear coordination compounds that possess strong hydrogen bond interactions. The anti-inflammatory effects of these compounds were assayed in lipopolysaccharide activated RAW 264.7 macrophages by inhibition of NO production. Moreover, the cytotoxicity of the complexes and the ligand in RAW 264.7 cells were determined for the first time. The most significant results were obtained for the compounds 4 and 5 reaching values of NO inhibition close to 80% at 48 h, and above to 90% at 72 h of treatment. The highest inhibitory effects on NO production were showed at the range 7-23 μg/mL for compounds 4 and 5. As a consequence, compounds 4 and 5 could be potential drugs due to the interesting anti-inflammatory properties showed. The anti-cancer potential of these compounds has been also tested against different tumor cell lines. The cytotoxicity of the ligand and of compounds 2 and 3 were assayed in three cell lines: HT29, colon cancer cells, Hep-G2, hepatoma cells and B16-F10 melanoma cells. The best results have been achieved with compound 2 in HepG2 and B16-F10 cell lines, being between 1.5 and 2 times more effective that the ligand in HepG2 cells, and B16-F10 cells. All in all, indazole-3-carboxylic acid is a promising ligand for the formation of coordination compounds with biochemical properties.

Antiparasitic, anti-inflammatory and cytotoxic activities of 2D coordination polymers based on 1H-indazole-5-carboxylic acid

We report on the formation of two novel multifunctional isomorphous (4,4) square-grid 2D coordination polymers based on 1H-indazole-5-carboxylic acid. To the best of our knowledge, these complexes are the first examples of 2D-coordination polymers constructed with this novel ligand. We have analysed in detail the structural, magnetic and anti-parasitic properties of the resulting materials. In addition, the capability of inhibiting nitric oxide production from macrophage cells has been measured and was used as an indirect measure of the anti-inflammatory response. Finally, the photocatalytic activity was measured with a model pollutant, i.e. vanillic acid (phenolic compound), with the aim of further increasing the functionalities and applicability of the compounds.

Metal-controlled structural variations of coordination architectures constructed from flexible 1H-benzimidazole-1-propionic acid

Five low-dimensional coordination polymers and a novel discrete dodecametallic cage have been obtained from appropriate transition metals in combination with a flexible bifunctional benzimidazole carboxylic acid.

Architectures varying from discrete molecular units to 2-dimensional coordination polymers and photoluminescence behavior of zinc and cadmium comprising an anionic zwitterion of rigid 4,5-dicarboxy-1,3-dimethyl-1H-imidazolium iodide

A rigid ligand, 4,5-dicarboxy-1,3-dimethyl-1H-imidazolium iodide (H₂DDII) and crystallized as zwitterion (1) and employed in the synthesis of anionic zwitterion complexes or coordination polymers (CPs)2–6of Zn(ii) and Cd(ii).

Copolymerization of an indazole ligand into the self-polymerization of dopamine for enhanced binding with metal ions

Synthesis and mussel-inspired polymerization of a new catechol monomer. The generated copolymer exhibits enhanced metal binding, due to the ligand nature of the new monomer, compared to polydopamine homopolymer.