A three‐dimensional (3D) manganese (II) coordination polymer: Synthesis, structure and catalytic activities

Abstract

A new Mn (II)‐containing coordination polymer, [Mn6(Ipa)6(ad)⋅6H2O] (1; Ipa = isophthalate ligand; ad = adenine), was synthesized by reacting hydrated manganese nitrate with isophthalic acid and adenine under solvothermal reaction conditions. Polymer 1 was characterized using single‐crystal X‐ray diffraction analysis and other techniques such as Fourier transform infrared spectroscopy, elemental analyses and powder X‐ray diffraction. The solid‐state structure of 1 confirmed the formation of a three‐dimensional framework structure based on Mn6 secondary building units. Phase purity of bulk 1 and its thermal stability were investigated. Polymer 1 was evaluated for its performance as a heterogeneous catalyst for the Henry (nitroaldol) reaction of nitromethane with several aldehydes. The recyclability of 1 and heterogeneity of the reaction were also explored. A plausible mechanism for such reaction is proposed. To the best of our knowledge, polymer 1 represents the first example of a Mn (II)‐ and adenine‐containing coordination polymer as well as the first example of a Mn (II)‐containing coordination polymer that has been employed for the Henry reaction.

Coordination Polymers from Biphenyl-Dicarboxylate Linkers: Synthesis, Structural Diversity, Interpenetration, and Catalytic Properties

“…This can be evidenced by almost constant yields of products, a minor decline of which is likely associated with a minor loss of catalyst after several recycling experiments. In a model reaction involving 4-nitrobenzaldehyde and nitroethane as substrates, the catalytic performance of 3 is comparable to other heterogeneous catalytic systems based on metal-carboxylate coordination compounds (Table S3, Supporting Information) − or is superior if the reaction time is taken into consideration. Apart from high activity, good stability, and recyclability of 3 , this catalyst can lead to excellent product yields in a shorter reaction time.…”

“…For these Henry reactions, a possible mechanism was proposed on the basis of prior research studies describing related transformations that involve aldehydes and nitroethane and are catalyzed by CPs (Figure S8, Supporting Information). − Hence, there is an initial activation of both 4-nitrobenzaldehyde and nitroethane via an interaction with Zn­(II) sites of the CP (Figure S8, step i). Such an interaction augments electrophilicity of 4-nitrobenzaldehyde and acidity of nitroethane.…”

“…The following tendency in the total product yields was observed (Table , entries 7, 14–17): CH 3 OH (89%) > H 2 O (76%) > THF (66%) > C 2 H 5 OH (52%) > CH 3 CN (10%). Although there is no clear connection between the activity and structure of the catalyst, a superior performance of compound 3 might be related to its 1D chain structure and/or existence of open Zn sites and labile water ligands. ,,, Compound 3 with a 1D structure features a better accessibility of metal centers if compared to MOF 6 with a 3D structure. This likely explains superior catalytic performance of 3 . , Besides, we have to highlight that the present Henry reactions between 4-nitrobenzaldehyde and nitroethane do not occur in the catalyst’s absence or applying organic H 4 L 1 and H 4 L 2 precursors as catalysts (no products were detected in all cases).…”

“…The Henry reaction, also known as nitroaldol transformation, represents an important carbon–carbon bond-forming technique in organic synthesis, wherein nitroalkanes are combined with carbonyl substrates (aldehydes, ketones) to generate beta-nitro alcohol products. Generally, this type of reaction requires a base as a catalyst, such as alkoxide, alkali metal hydroxide, or amine. − Considering possible use of different CPs as heterogeneous catalytic systems in the Henry transformation that can proceed in the absence of base, − the catalytic behavior of 1 – 9 was explored in the transformations involving various aldehyde substrates and nitroethane to give the corresponding β-nitro alcohol products. As a model substrate, 4-nitrobenzaldehyde was chosen (Scheme and Table ) and the impact of various reaction conditions was monitored (e.g., reaction time, type of solvent, and amount of catalyst and its recycling).…”

“…Although there is no clear connection between the activity and structure of the catalyst, a superior performance of compound 3 might be related to its 1D chain structure and/or existence of open Zn sites and labile water ligands. 75 , 79 , 83 , 84 Compound 3 with a 1D structure features a better accessibility of metal centers if compared to MOF 6 with a 3D structure. This likely explains superior catalytic performance of 3 .…”