Crystal Chemistry of Zinc Quinaldinate Complexes with Pyridine-Based Ligands

Abstract

Substitution of methanol in [Zn(quin) 2 (CH 3 OH) 2 ] (quin − denotes an anionic form of quinoline-2-carboxylic acid, also known as quinaldinic acid) with pyridine (Py) or its substituted derivatives, 3,5-lutidine (3,5-Lut), nicotinamide (Nia), 3-hydroxypyridine (3-Py-OH), 3-hydroxymethylpyridine (3-Hmpy), 4-hydroxypyridine (4-Py-OH) and 4-hydroxymethylpyridine (4-Hmpy), afforded a series of novel heteroleptic complexes with compositions [Zn(quin) (6) (4-Pyridone = a keto tautomer of 4-hydroxypyridine), and [Zn(quin) 2 (4-Hmpy) 2 ] (7). In all reactions, the {Zn(quin) 2 } structural fragment with quinaldinate ions bound in a bidentate chelating manner retained its structural integrity. With the exception of [Zn(quin) 2 (4-Pyridone)] (6), all complexes feature a six-numbered coordination environment of metal ion that may be described as a distorted octahedron. The arrangement of ligands is trans. The coordination sphere of zinc(II) in the 4-pyridone complex consists of only three ligands, two quinaldinates, and one secondary ligand. The metal ion thereby attains a five-numbered coordination environment that is best described as a distorted square-pyramid (τ parameter equals 0.39). The influence of substituents on the pyridine-based ligand over intermolecular interactions in the solid state is investigated. Since pyridine and 3,5-lutidine are not able to form hydrogen-bonding interactions, the solid state structures of their complexes, [Zn(quin) 2 (Py) 2 ] (1) and [Zn(quin) 2 (3,5-Lut) 2 ] (2), are governed by π···π stacking, C-H···π, and C-H···O intermolecular interactions. With other pyridine ligands possessing amide or hydroxyl functional groups, the connectivity patterns in the crystal structures of their complexes are governed by hydrogen bonding interactions. Thermal decomposition studies of novel complexes have shown the formation of zinc oxide as the end product.

From cyclic amines and acetonitrile to amidine zinc(ii) complexes

“…10. In the monoclinic polymorph, four N-H(pyroH + )/COO À contacts with lengths not longer than 2.776(4)Å link two [Zn(quin) 3 ] À ions with two pyrrolidinium cations into a cyclic motif, denoted as R 4 4 (20). In the triclinic polymorph, one N-H/COO À contact is longer, it amounts to 2.926(3)Å.…”

“…Surprisingly, a search of the Cambridge Structural Database (CSD) has revealed that its zinc(II) complexes are fairly scarce. 14 There are reports of zinc(II) quinaldinate complexes with water, 13 methanol, 15 dimethylsulphoxide, 16 imidazole, 17 1-methylimidazole, 18 a tridentate N,N,S ligand, 19 pyridine-based ligands 20 and recently also amino alcohols. 21 The latter two systems are results of our previous work.…”

Beyond the Simple Copper(II) Coordination Chemistry with Quinaldinate and Secondary Amines

“…Based on the previous study of related zinc(II) complexes with quinaldinate [36], [Cu(quin) 2 (H 2 O)] was expected to undergo a straightforward substitution of water with the amine ligand. At fairly mild conditions, the displacement reactions should result in complexes with one or two amine ligands, [Cu(quin) 2 (amine)] and [Cu(quin) 2 (amine) 2 ].…”

Investigating the Potential of 8-Amidoquinoline Derivatives as a Fluorescent Probe for Zinc Detection: A Systematic Literature Review

“…These three atoms may react as electron-donating during the coordination binding with Zn 2+ . However, as [74] mentioned since Zn 2+ does not behave reliably either as a soft or as a hard Lewis acid, it poses a borderline case with no particular fondness for oxygen, nitrogen or sulfur-donor ligands to be coordinated, the results of the concluded binding coordination sites to form complexes were differ. Roughly, we reviewed all of them as there were no fixed preferences and the differ based on derivative, atoms presenting, molecular geometry, medium, and environment.…”