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

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]·4nH₂O (2), [Zn(μ₂-H₂L₁)(2,2'-bipy)(H₂O)] (3), [Cd(μ₂-H₂L₁) (2,2'-bipy)(H₂O)] (4), [Mn₂(μ₂-H₂L₁)(μ₄-H₂L₁)(μ₂-4,4'-bipy)₂]·4nH₂O (5), [Zn(μ₂-H₂L₁)(μ₂-4,4'-bipy)] (6), [Zn(μ₂-H₂L₂)(phen)] (7), [Cd(μ₃-H₂L₂)(phen)] (8), and [Cu(μ₂-H₂L₂) (μ₂-4,4'-bipy)(H₂O)] (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.