title: Molecular Spin Crossover in Slow Motion: Light-Induced Spin-State Transitions in Trigonal Prismatic Iron(II) Complexes.
abstract: A straightforward access is provided to iron(II) complexes showing exceedingly slow spin-state interconversion by utilizing trigonal-prismatic directing ligands (L(n)) of the extended-tripod type. A detailed analysis of the interrelations between complex structure (X-ray diffraction, density functional theory) and electronic character (SQUID magnetometry, Mössbauer spectroscopy, UV/vis spectroscopy) of the iron(II) center in mononuclear complexes [FeL(n)] reveals spin crossover to occur along a coupled breathing/torsion reaction coordinate, shuttling the complex between the octahedral low-spin state and the trigonal-prismatic high-spin state along Bailar's trigonal twist pathway. We associate both the long spin-state lifetimes in the millisecond domain close to room temperature and the substantial barriers against thermal scrambling (Ea ≈ 33 kJ mol(-1), from Arrhenius analysis) with stereochemical constraints. In particular, the topology of the κ(6)N ligands controls the temporary and structural dynamics during spin crossover.
authors.affiliation: Institut für Chemie, Technische Universität Berlin , Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Stock
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT) , Engesserstrasse 15, 76131 Karlsruhe, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Deck
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT) , Engesserstrasse 15, 76131 Karlsruhe, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Hohnstein
authors.affiliation: Department Chemie und Pharmazie, Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstraße 1, 91058 Erlangen, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Korzekwa
authors.affiliation: Department Chemie und Pharmazie, Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstraße 1, 91058 Erlangen, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Meyer
authors.affiliation: Department Chemie und Pharmazie, Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstraße 1, 91058 Erlangen, Germany.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Heinemann
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT) , Engesserstrasse 15, 76131 Karlsruhe, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Breher
authors.affiliation: Institut für Chemie, Technische Universität Berlin , Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Hörner