Five New Cobalt(II) and Copper(II)-1,2,4,5-benzenetetracarboxylate Supramolecular Architectures: Syntheses, Structures, and Magnetic Properties

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• 作者：Arpi Majumder ; Volker Gramlich ; Georgina M. Rosair ; Stuart R. Batten ; Jason D. Masuda ; M. S. El Fallah ; Joan Ribas ; Jean-Pascal Sutter ; Cé ; dric Desplanches ; Samiran Mitra
• 刊名：Crystal Growth & Design
• 出版年：2006
• 出版时间：October 2006
• 年：2006
• 卷：6
• 期：10
• 页码：2355 - 2368
• 全文大小：883K
• 年卷期：v.6,no.10(October 2006)
• ISSN：1528-7505

文摘

1,2,4,5-Benzenetetracarboxylic acid (H₄btec) and a combination of N-donor coligands, such as 4-aminopyridine (4-apy), pyrazine (pyz), 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), and 4,4'-bipyridine (4,4'-bipy) with transition metal ions Co(II) andCu(II), give rise to five coordination complexes namely, [{Co(H₂btec)(H₂O)₄}·4-apy·(H₂O)₂]_n (1), [{Cu(btec)(4-apy)₂}·(4-Hapy)₂·(H₂O)₄]_n (2), [{Cu(H₃btec)₂(pyz)·(H₂O)₂}·H₂O]_n (3), [Co(tptz)(H₂O)₂(H₂btec)]·(H₂O)₂ (4), and [{Co₂(4,4'-bipy)₂(H₂O)₈}·(btec)·(H₂O)₂]_n (5). All these complexes form supramolecular frameworks through ligand-based hydrogen bonding interactions. They havebeen characterized by a combination of analytical, spectroscopic, and crystallographic methods. These highly crystalline complexeshave been obtained under different pH conditions at room temperature and the btec binding mode differs in these five complexes.Complex 1 is a one-dimensional (1D) layered solid consisting of alternating neutral metal-organic coordination polymeric chains,[Co(H₂btec)(H₂O)₄]_n, and amines whereas the molecular structure of 2 is made up of alternating layers of anionic [Cu(btec)(4-apy)₂]^2-_n coordination polymers and 4-apy cations (4-Hapy). In both 1 and 2, btec links the metal centers. Complex 3 is composedof zigzag 1D copper chains, and complex 4 is a mononuclear cobalt complex. In both 3 and 4, btec binds as a monodentate ligand.In the crystal structure of 5, btec^4- is present unbound in the lattice and linked to 1D chains of [Co(4,4'-bipy)(H₂O)₄]²⁺ throughstrong hydrogen bonding interactions. The magnetic properties of the polymers were investigated in the temperature range 300-2K. The values for the spin coupling constant J were estimated to be -0.60, -0.50, -0.79, and -5.72 cm^-1 for 1-3 and 5, respectively,indicative of antiferromagnetic interactions.