Crystal Structures and Magnetic and Gas-Occlusion Properties of Microporous Materials Containing Infinite Chains of Mononuclear Metal (Cu(II), Zn(II), and Ni(II)) Dicarboxylates Unit

A new series of microporous materials containing infinite chains of a mononuclear metal (Cu(II), Zn(II), Ni(II))-pyridine unit bridged by dicarboxylates (copper(II) terephthalate-pyridine 1a, copper(II) terephthalate-4-phenylpyridine 1b, zinc(II) fumarate-pyridine 2a, zinc(II) terephthalate-pyridine 2b, nickel(II) fumarate-pyridine 3a, and nickel(II) terephthalate-pyridine 3b) have been prepared. These complexes, which have a regular one-dimensional structure, occlude large amounts of gases. The maximum amount of N2 gas is 0.7-10.7 mole per mole of metal(II) salt, indicating the presence of a large number of micropores. A porous structure, which is formed by stacking and self-assembly of the linear metal(II) dicarboxylates, was determined by X-ray crystallography. We have elucidated the paramagnetic properties of 1a, 1b, 3a, and 3b by magnetic measurement (SQUID), whereas 2a and 2b were found to be diamagnetic. The magnetic susceptibilities of 1a and 1b obey the Curie-Weiss law over the range of 70-300 K ((theta) = -1.4 K and (theta) = +5.5 K, respectively); the obtained Weiss constants ((theta)) indicate the existence of small antiferromagnetic interactions (1a) and ferromagnetic interactions (1b). The different magnetic behaviors between 1a and 1b demonstrate that hydrogen bonding between the carboxylate groups and coordinated water molecules plays an important role in determining the bridge geometries and super-exchange interaction between the Cu(II) ions through the Cu-O-C-O-H-O-Cu pathways. In contrast to those of the copper(II) complexes, the magnetic susceptibilities of 3a and 3b obey the Curie law.