title: Systematic syntheses and metalloligand doping of flexible porous coordination polymers composed of a Co(III)-metalloligand.
abstract: A series of flexible porous coordination polymers (PCPs) RE-Co, composed of a Co(III)-metalloligand [Co(dcbpy)3](3-) (Co; H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide cations (RE(3+) = La(3+), Ce(3+), Pr(3+), Nd(3+), Sm(3+), Eu(3+), Gd(3+), Tb(3+), Er(3+)), was systematically synthesized. X-ray crystallographic analysis revealed that the six carboxylates at the top of each coordination octahedron of Co(III)-metalloligand were commonly bound to RE(3+) cations to form a rock-salt-type porous coordination framework. When RE-Co contains a smaller and heavier RE(3+) cation than Nd(3+), the RE-Co crystallized in the cubic Fm-3m space group, whereas the other three RE-Co with larger RE(3+) crystallized in the lower symmetrical orthorhombic Fddd space group, owing to the asymmetric 10-coordinated bicapped square antiprism structure of the larger RE(3+) cation. Powder X-ray diffraction and vapor-adsorption isotherm measurements revealed that all synthesized RE-Co PCPs show reversible amorphous-crystalline transitions, triggered by water-vapor-adsorption/desorption. This transition behavior strongly depends on the kind of RE(3+); the transition of orthorhombic RE-Co was hardly observed under exposure to CH3OH vapor, but the RE-Co with smaller cations such as Gd(3+) showed the transition under exposure to CH3OH vapors. Further tuning of vapor-adsorption property was examined by doping of Ru(II)-metalloligands, [Ru(dcbpy)3](4-), [Ru(dcbpy)2Cl2](4-), [Ru(dcbpy)(tpy)Cl](-), and [Ru(dcbpy)(dctpy)](3-) (abbreviated as RuA, RuB, RuC, and RuD, respectively; tpy = 2,2':6',2″-terpyridine, H2dctpy = 4,4″-dicarboxy-2,2':6',2″-terpyridine), into the Co(III)-metalloligand site of Gd-Co to form the Ru(II)-doped PCP RuX@Gd-Co (X = A, B, C, or D). Three Ru(II)-metalloligands, RuA, RuB, and RuD dopants, were found to be uniformly incorporated into the Gd-Co framework by replacing the original Co(III)-metalloligand, whereas the doping of RuC failed probably because of the less number of coordination sites. In addition, we found that the RuA doping into the Gd-Co PCP had a large effect on vapor-adsorption due to the electrostatic interaction originating from the negatively charged RuA sites in the framework and the charge-compensating Li(+) cations in the porous channel.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University , North-10 West-8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Yui
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ohba
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ogawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Noro
authors.forename: Ho-Chol
authors.initials: HC
authors.lastname: Chang
authors.forename: Masako
authors.initials: M
authors.lastname: Kato