Cu(II) coordination polymers stabilized by pyridine-2,6-dicarboxylate anion and pyrazole derivatives through ligand hydrolysis

• Published in: Journal of coordination chemistry Vol. 71; no. 16-18; pp. 2658 - 2673
• Main Authors: Khan, Ezzat, Ali Khan, Sher, Zahoor, Muhammad, Nawaz Tahir, Muhammad, Noor, Awal, Altaf, Ataf Ali
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 17-09-2018; Taylor & Francis Ltd
• Subjects: 2,6-Pyridinedicarbonyldichloride; Carbonyls; Chemical analysis; Coordination polymers; Copper; Ligands; Magnetic permeability; magnetic susceptibility; NMR spectroscopy; Polymers; Pyrazole; pyrazole derivatives; Pyridine dicarboxylate; Trimethylamine; X-ray; X-ray diffraction
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2018.1501562

2,6-Pyridinedicarbonyldichloride (PDD) was treated with pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole in the presence of trimethylamine at room temperature. Reactions afforded 2,6-bis(pyrazolyl-1-carbonyl)pyridine (1), 2,6-bis(3-methylpyrazolyl-1-carbonyl)pyridine (2) and 2,6-bis(3,5-dimethylpyrazolyl-1-carbonyl)pyridine (3). 1-3 were treated with copper ion under ambient conditions in open air. Such coupling of 1 and 2 with copper led to coordination polymers 6 and 7, bearing 1D architectures, of general formulas [Cu(C
7
H
3
NO
4
)(C
3
H
4
N
2
)]
n
and [Cu(C
7
H
3
NO
4
)(C
4
H
7
N
2
)]
n
(C
7
H
3
NO
4
 = 2,6-pyridinedicarboxylate ion, C
3
H
4
N
2
 = pyrazole and C
4
H
7
N
2
 = 3-methylpyrazole), respectively. Under the same experimental conditions, 3 instead forms a mononuclear Cu(II) complex (8). Structures of 1-3 and 6-8 were determined with X-ray diffraction. The solid state structures reveal that short-range intermolecular interactions in the ligands afford 1D (1) and 2D (2 and 3) supramolecular chains, respectively. 6 and 7 both crystallize in the orthorhombic system, space group P2
1
2
1
2
1
. 1-3 were also characterized with elemental analysis and NMR spectroscopy. The magnetic susceptibility measurements indicate that both complexes are paramagnetic with effective moments of 1.75 (6) and 1.90 (7) µ
B
at 300 K. The voltammetric signatures of 6 and 8 show two steps reversible redox behavior as evidenced by the appearance of two cathodic waves with corresponding anodic peaks in the backward scan.