title: Synthesis, Structure, Magnetic Behavior, and Mössbauer Spectroscopy of Two New Iron(II) Spin-Transition Compounds with the Ligand 4-Isopropyl-1,2,4-triazole. X-ray Structure of [Fe(3)(4-isopropyl-1,2,4-triazole)(6)(H(2)O)(6)](tosylate)(6).2H(2)O.
abstract: Two new iron(II) compounds with the formula [Fe(3)(iptrz)(6)(H(2)O)(6)]X(6).xH(2)O (with iptrz = 4-isopropyl-1,2,4-triazole and X = p-toluenesulfonate (Tos) or trifluoromethanesulfonate (Trifl)) were synthesized. The crystal structure of [Fe(3)(iptrz)(6)(H(2)O)(6)](Tos)(6).2H(2)O (I) has been solved at room temperature. Crystals of I are triclinic, space group P&onemacr; with a = 12.8820(11) Å, b = 15.580(2) Å, c = 24.445(4) Å, alpha = 79.270(12) degrees, beta = 86.688(11) degrees, gamma = 83.007(8) degrees, Z = 2. The structure of I consists of linear trinuclear cations with a +6 charge and noncoordinated anions and lattice water molecules. The central iron ion is located on an inversion center and is coordinated by 6 nitrogen atoms of 6 iptrz molecules bridging via the nitrogen atoms in the 1,2-positions. Each external iron atom completes its coordination sphere with three coordinated water molecules. The temperature dependent magnetic measurements of compound I and [Fe(3)(iptrz)(6)(H(2)O)(6)](Trifl)(6) (II) show that both compounds exhibit a gradual spin conversion of the central iron ion centered at T(1/2) = 242 K for I and 187 K for II. Temperature dependent Mössbauer spectroscopy measurements on I show the behavior expected for a compound of this nature. The measurements on II indicate a strong influence of the spin conversion of the central iron ion on both external iron ions. The nature of this phenomenon is proposed to be connected to a very rigid lattice structure (ionic, H-bonding) connecting the trinuclear units.
authors.affiliation: Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Bijvoet Centre for Biomolecular Research, Crystal and Structural Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Institut für Anorganische und Analytische Chemie, Universität Mainz, Staudingerweg 9, D-55099 Mainz, Germany.
authors.forename: Jeroen J. A.
authors.initials: JJ
authors.lastname: Kolnaar
authors.forename: Gytha
authors.initials: G
authors.lastname: van Dijk
authors.forename: Huub
authors.initials: H
authors.lastname: Kooijman
authors.forename: Anthony L.
authors.initials: AL
authors.lastname: Spek
authors.forename: Vadim G.
authors.initials: VG
authors.lastname: Ksenofontov
authors.forename: Philipp
authors.initials: P
authors.lastname: Gütlich
authors.forename: Jaap G.
authors.initials: JG
authors.lastname: Haasnoot
authors.forename: Jan
authors.initials: J
authors.lastname: Reedijk