title: Flexible crystals of perovskite-like coordination polymers with a tunable and switchable organic guest: (CH3NH3)2[KFe(CN)6] and (CH3NH3)2[KCo(CN)6].
abstract: The crystal structure has been determined for (CH3NH3)2[KCo(CN)6] at temperatures 100 and 443 K. It crystallizes in the monoclinic space group C2/c (LT) and in the cubic one Fm3[combining macron]m (HT). The dielectric response has been investigated for single crystals of pure K3[A'(CN)6] and guest-hosts of (CH3NH3)2[KA'(CN)6], where A' is a trivalent metal, Co or Fe. Their dielectric properties were measured in the frequency range between 135 Hz and 2 MHz in a wide temperature range between 200 and 460 K. The anisotropy of the electric permittivity for single crystals of (CH3NH3)2[KCo(CN)6] was analysed in terms of the crystal structure. The relaxation processes were observed in the case of the pure host K3Fe(CN)6and the guest/host crystal (CH3NH3)2[KFe(CN)6]. The activation energies of the dielectric relaxation have been estimated to be equal to 44 and 40 kJ mol-1for (CH3NH3)2[KFe(CN)6] and K3Fe(CN)6, respectively. The mechanism of the phase transitions found at 425 K and 421 K for (CH3NH3)2[KFe(CN)6] and (CH3NH3)2[KCo(CN)6], respectively, has been postulated. From the dielectric losses the value of the electric ac conductivity has been estimated and analyzed in terms of the activation process of the current carriers.
authors.affiliation: Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw, Poland. magdalena.rok@chem.uni.wroc.pl.
authors.forename: M
authors.identifier: http://orcid.org/0000-0001-6206-8391
authors.initials: M
authors.lastname: Rok
authors.affiliation: Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw, Poland. magdalena.rok@chem.uni.wroc.pl.
authors.forename: J K
authors.initials: JK
authors.lastname: Prytys
authors.affiliation: Institute of Low Temperature and Structure Research, Polish Academy of Science, Okólna 2, PO Box 937, 50-950 Wroclaw, Poland.
authors.forename: V
authors.identifier: http://orcid.org/0000-0003-1060-0459
authors.initials: V
authors.lastname: Kinzhybalo
authors.affiliation: Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw, Poland. magdalena.rok@chem.uni.wroc.pl.
authors.forename: G
authors.initials: G
authors.lastname: Bator