title: Synthesis, Ion Recognition Ability, and Metal-Assisted Aggregation Behavior of Dinuclear Metallohosts Having a Bis(Saloph) Macrocyclic Ligand.
abstract: Macrocyclic molecule 1 that has two saloph coordination sites was designed and synthesized. The macrocycle 1 was easily converted into the corresponding metallohosts 2 and 3 by the reaction with nickel(II) and palladium(II), respectively. As expected from the molecular structure of these metallohosts having an 18-crown-6-like cavity, the nickel(II) metallohost 2 showed excellent binding affinity toward Na(+), Ca(2+), and Sr(2+) to give 1:1 host-guest complexes. Preorganization effect due to the extremely rigid metal-containing macrocycle was suggested to be a major factor for the strong binding. Larger cations such as K(+), Rb(+), Cs(+), and Ba(2+) gave higher aggregated host-guest complexes such as 22M, 23M2, and 24M3. Density functional theory calculations revealed that smaller metal ions do not occupy the center of each macrocycle in the sandwich structures 22M, while larger Cs(+) simultaneously interacts with all the 12 oxygen donor atoms. On the basis of the interaction energy calculations, the preference for 2·Na over 22Na can be explained by destabilization of 22Na due to the elongated Na-O bonds and repulsive three-body interactions. When the ionic radius of the guest ion increases (K(+), Rb(+), Cs(+)), this destabilization becomes less significant and the formation of sandwich complexes 22M is favored. Such aggregation would significantly affect the physical and chemical properties of the metal complexes due to the interplane interactions between the metal centers.
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University , Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Shigehisa
authors.initials: S
authors.lastname: Akine
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Utsuno
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Shunjin
authors.initials: S
authors.lastname: Piao
authors.affiliation: Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Orita
authors.affiliation: Research Center for Computational Design of Advanced Functional Materials (CD-FMat), National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Tsuzuki
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Nabeshima