Two-step spin conversion of [FeII(5-NO2-sal-N(1,4,7,10))]: 292, 153, and 103 K x-ray crystal and molecular structure, infrared, magnetic, Moessbauer, calorimetric, and theoretical studies

Abstract

A detailed study of the two-step spin-state conversion in 4,7,10))] is presented with special emphasis on the structural changes evidenced by a multitemperature X-ray crystal and molecular structure study (292, 153, 103 K). The ligand (5-NO2-sal-N(l,4,7,10)) results from the Schiff base condensation of 5-nitrosalicylaldehyde with tetraazadecane in a 2:1 ratio. The

Spin-crossover Compounds with Wide Thermal Hysteresis

“…44,45 1:1 ratio. 58 However, there are also hysteretic transitions, where the steps and plateau only appear in the warming branch of the hysteresis loop. Only few such compounds have been structurally characterized, but this is most obviously explained by a notably large structural difference between the high-spin and low-spin state.…”

Symmetry Breaking in Iron(II) Spin-Crossover Molecular Crystals

“…Although crystallographic evidence of order in the intermediate states could only be partially demonstrated for the first plateau (1HS-2LS), where the unit cell triples to contain three distinct Fe II centers, it could be concluded from magnetic susceptibility and Mössbauer data that the steps corresponds to the LS step1 Ø 1HS : 2LS step2 Ø 2HS : 1LS step3 Ø HS sequence [36]. Despite the nature of the SCO in [Fe II (2-pic) 3 ]Cl 2¨E tOH] has attracted much attention for two decades, the first structurally investigated two-step SCO with CSB was reported by Tuchagues et al for the complex [Fe II {5-NO 2 -sal-N(1,4,7,10)}], where 5-NO 2 -sal-N(1,4,7,10) is a six-coordinating ligand prepared by Schiff base condensation of 5-NO 2 -salicylaldehyde with 1,4,7,10-tetraazadecane [37]. The magnetic data showed the occurrence of two cooperative half spin transitions centered at T c2 = 176 K and T c1 =142 K with hysteresis loops 3 K and 8 K wide, respectively ( Figure 4).…”

Aperiodic Spin State Ordering of Bistable Molecules and Its Photoinduced Erasing

“…1, q is the wave vector and η is the amplitude of the wave. In several SC systems, superstructure ordering of γ HS over crystalline sites were reported 23,25 , including the isostructural PF 6 derivative 26 . For the latter, the spin-state ordering around an average value of γ HS =0.5 corresponds to a cell doubling along c axis, since q=c*/2.…”

“…Both basic scientific research 20 , as well as potential technological applications were investigated, because of ultrafast-switching 21 , information storage or visual displays 13,22 abilities. The possibility offered by various external control parameters such as temperature, pressure or light irradiation for balancing the relative population between low-spin (LS, S=0) and high-spin (HS, S=2) states has attracted much interest and many such complexes have been widely studied over the past decades 12 . In addition to simple entropy-driven macroscopic conversion from LS to HS, complex phenomena resulting from the partial spin conversion and the periodic ordering of HS and LS states around stepped transitions have been described 23,24,25,26 . In this paper we describe a novel type of phase, where the long-range order of HS and LS molecular states is incommensurately modulated with respect to the 3D structure.…”

“…23,24 For [Fe II H 2 L 2-Me ] cation in the PF 6 and AsF 6 salts, <Fe-N> changes from 2.01 Å (LS) to 2.19 Å (HS). 25,26,28 At room temperature these complexes are isostructural to the reported SbF 6 derivative (space group P22 1 2 1 , Fig.…”