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

The present work explores two biphenyl-dicarboxylate linkers, 3,3'-dihydroxy-(1,1'-biphenyl)-4,4'-dicarboxylic (H4L1) and 4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylic (H4L2) acids, in hydrothermal generation of nine new compounds formulated as [Co2(μ2-H2L1)2(phen)2(H2O)4] (1), [Mn2(μ4-H2L1)2(phen)2]n·4nH2O (2), [Zn(μ2-H2L1)(2,2'-bipy)(H2O)]n (3), [Cd(μ2-H2L1) (2,2'-bipy)(H2O)]n (4), [Mn2(μ2-H2L1)(μ4-H2L1)(μ2-4,4'-bipy)2]n·4nH2O (5), [Zn(μ2-H2L1)(μ2-4,4'-bipy)]n (6), [Zn(μ2-H2L2)(phen)]n (7), [Cd(μ3-H2L2)(phen)]n (8), and [Cu(μ2-H2L2) (μ2-4,4'-bipy)(H2O)]n (9). These coordination polymers (CPs) were generated by reacting a metal(II) chloride, a H4L1 or H4L2 linker, and a crystallization mediator such as 2,2'-bipy (2,2'-bipyridine), 4,4'-bipy (4,4'-bipyridine), or phen (1,10-phenanthroline). The structural types of 1-9 range from molecular dimers (1) to one-dimensional (3, 4, 7) and two-dimensional (8, 9) CPs as well as three-dimensional metal-organic frameworks (2, 5, 6). Their structural, topological, and interpenetration features were underlined, including an identification of unique two- and fivefold 3D + 3D interpenetrated nets in 5 and 6. Phase purity, thermal and luminescence behavior, as well as catalytic activity of the synthesized products were investigated. Particularly, a Zn(II)-based CP 3 acts as an effective and recyclable heterogeneous catalyst for Henry reaction between a model substrate (4-nitrobenzaldehyde) and nitroethane to give β-nitro alcohol products. For this reaction, various parameters were optimized, followed by the investigation of the substrate scope. By reporting nine new compounds and their structural traits and functional properties, the present work further outspreads a family of CPs constructed from the biphenyl-dicarboxylate H4L1 and H4L2 linkers.

A tryptophan-based copper(ii) coordination polymer: catalytic activity towards Suzuki–Miyaura cross-coupling reactions

An unusual tryptophan coordination mode with copper(ii) wherein l-tryp is coordinated through the carboxylate and amine groups. A heterogeneous catalyst for the Suzuki cross-coupling reaction with ∼98% yield under normal reaction conditions.