title: Coordination nano-space as stage of hydrogen ortho-para conversion.
abstract: The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)-para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o-p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o-p conversion.
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Fukushima Renewable Energy Institute , AIST, Fukushima 963-0215, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kosone
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University , Kyoto 606-8501, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hori
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Faculty of Pure and Applied Sciences, TIMS and CiRfSE, University of Tsukuba , 305-8571, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Nishibori
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Department of Physical Science , Osaka Prefecture University , Osaka 599-8531, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kubota
authors.affiliation: Department of Chemistry , Kyushu University , Fukuoka 812-8581, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Mishima
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Department of Chemistry , Kyushu University , Fukuoka 812-8581, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ohba
authors.affiliation: Department of Materials Science , Shimane University , Matsue 690-8504, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kato
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Japan Synchrotron Radiation Research Institute , SPring-8, Hyogo 679-5198, Japan.
authors.forename: Jungeun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Instituto de Ciencia Molecular (ICMol), Universidad de Valencia , 46980 Paterna, Valencia, Spain.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Real
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University , Kyoto 606-8501, Japan ; Department of Synthetic Chemistry and Biological Chemistry , Kyoto University , Kyoto 615-8510, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kitagawa
authors.affiliation: RIKEN SPring-8 Center , RIKEN, 1-1-1 Koto, Hyogo 679-5148, Japan ; Japan Synchrotron Radiation Research Institute , SPring-8, Hyogo 679-5198, Japan ; Department of Advanced Materials Science , The University of Tokyo , Chiba 277-8561, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Takata
keywords: hydrogen storage porous coordination polymer; ortho–para conversion; structure of absorbed H2