title: Light-induced bistability in the 2 D coordination network {[Fe(bbtr)3][BF4]2}∞ : wavelength-selective addressing of molecular spin states.
abstract: Whereas the neat polymeric Fe(II) compound {[Fe(bbtr)3 ][ClO4 ]2 }∞ (bbtr=1,4-di(1,2,3-triazol-1-yl)butane) shows an abrupt spin transition centered at 107 K facilitated by a crystallographic symmetry breaking, in the covalently linked 2D coordination network of {[Fe(bbtr)3 ][BF4 ]2 }∞ , Fe(II) stays in the high-spin state down to 10 K. However, strong cooperative effects of elastic origin result in reversible, persistent, and wavelength-selective photoswitching between the low-spin and high-spin manifolds. This compound thus shows true light-induced bistability below 100 K. The persistent bidirectional optical switching behavior is discussed as a function of temperature, irradiation time, and intensity. Crystallographic studies reveal a photoinduced symmetry breaking and serve to establish the correlation between structure and cooperative effects. The static and kinetic behavior is explicated within the framework of the mean-field approximation.
authors.affiliation: Département de chimie physique, Université de Genève, 30 Quai Ernest-Anserment, 1211 Genève 4, Switzerland.
authors.forename: Pradip
authors.initials: P
authors.lastname: Chakraborty
authors.forename: Sebastien
authors.initials: S
authors.lastname: Pillet
authors.forename: El-Eulmi
authors.initials: el-E
authors.lastname: Bendeif
authors.forename: Cristian
authors.initials: C
authors.lastname: Enachescu
authors.forename: Robert
authors.initials: R
authors.lastname: Bronisz
authors.forename: Andreas
authors.initials: A
authors.lastname: Hauser
keywords: cooperative effects; iron; photoinduced bistability; photoswitching; spin crossover