Abstract
The biomolecule chelidonic acid (H2chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) has been used to build new coordination polymers with the bridging N,N′-ligands 4,4′-bipyridine (4,4-bipy) and 1,2-bis(4-pyridyl)ethane (bpe). Four compounds have been obtained as single crystals: 1D cationic coordination polymers [M(4,4-bipy)(OH2)4]2+ with chelidonate anions and water molecules in the second coordination sphere in 1∞[Zn(4,4-bipy)(H2O)4]chel·3H2O (2) and in the two pseudopolymorphic 1∞[Cu(4,4-bipy)(H2O)4]chel·nH2O (n = 3, 4a; n = 6, 4b), and the 2D neutral coordination polymers 2∞[Zn(chel)(4,4-bipy)(H2O)]·2H2O (1) and 2∞[Zn(chel)(bpe)(H2O)]·H2O (3) where the chelidonate anion acts as a bridging ligand. The effects of the hydrogen bonds on the crystal packing were analyzed. The role of the water molecules hosted within the crystals lattices was also studied.
Highlights
Chelidonic acid (H2chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) is a biomolecule found in several plants and is considered to be an active component of some medicinal herbs [1]
The isolated molecule, O13w, corresponds to the W1 motif that is present in all three compounds (2, 4a and 4b) with the same structural behaviour; as a donor this water molecule is connected with a chelidonate molecule by hydrogen bonds with two oxygen atoms from the two carboxylate groups (O···O distances of 2.721(3) and 2.723(3) Å in 4b) and as an acceptor with one or two coordinated water molecules of the corresponding cations
The layers in 1 are stacked along the b axis to yield a final 3D arrangement with an ABAB stacking mode (Figure 5). These layers are connected by means of hydrogen bonds involving the coordinated water molecule and oxygen atoms from carboxylate groups of neighbouring layers (d(O1W · Ochel) = 2.699(4) and 2.772(5) Å; Table S4, detail shown in FSicghuermee53)
Summary
Chelidonic acid (H2chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) is a biomolecule found in several plants and is considered to be an active component of some medicinal herbs [1]. The isolated molecule, O13w, corresponds to the W1 motif that is present in all three compounds (2, 4a and 4b) with the same structural behaviour; as a donor this water molecule is connected with a chelidonate molecule by hydrogen bonds with two oxygen atoms from the two carboxylate groups (O···O distances of 2.721(3) and 2.723(3) Å in 4b) and as an acceptor with one or two coordinated water molecules of the corresponding cations. One carboxylate group of the chelidonate ligand is anisobidentate, with a bite angle of about 155◦, one zinc metal has a short3Zn–O distance (2.130(3) ZÅni–nO1(1aWnd) 2.085(2) Å in 3), the o2t.0h3e2r(h3a) s a longer distance of ar2o.1u5n8d(22). Å and the other carboxylate group is monodentate2..015(3)
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