title: Structural basis for the phase switching of bisaminecopper(II) cations at the thermal limits of lattice stability.
abstract: The structural grounds of the decrease of point and lattice symmetries coupled with switching of the exchange interaction in single crystals of a highly strained, coordinationally unsaturated bisdiaminecopper(II) cation are described. The combined magnetic susceptibility and X-ray diffraction results indicate that the interplay between the inherent vibronic instability and ligand-field strain imposed by moderately flexible, coordinationally shielding ligands enables effective switching of the pseudo-Jahn-Teller d9 centers between states with different exchange interaction in the low-temperature regime and valence orbital orientation and coordination geometry in the high-temperature regime. Within the low-temperature hysteresis region, the phase transition can also be induced by excitation of the ligand-to-metal charge-transfer bands, resulting in overall shrinkage of the lattice. The compound is a prototype of weakly electronically coupled one-dimensional Jahn-Teller systems, which can undergo phase transitions induced by light, in addition to heating, cooling, and change of pressure, and it represents a prospective basis for the design of switching materials capable of multimode external control.
authors.affiliation: International Center for Young Scientists, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan. naumov.pance@nims.go.jp
authors.forename: Pance
authors.initials: P
authors.lastname: Naumov
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakurai
authors.forename: Toru
authors.initials: T
authors.lastname: Asaka
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Belik
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Adachi
authors.forename: Junichi
authors.initials: J
authors.lastname: Takahashi
authors.forename: Shin-ya
authors.initials: SY
authors.lastname: Koshihara