Related Experiment Video
Updated: Mar 25, 2026
Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope
Published on: March 24, 2019
Spin-State Versatility in a Series of Fe4 [2 × 2] Grid Complexes: Effects of Counteranions, Lattice Solvent, and
Markus Steinert1, Benjamin Schneider1, Sebastian Dechert1
1Georg-August-University , Institute of Inorganic Chemistry, Tammannstrasse 4, D-37077 Göttingen, Germany.
Abstract:
The new compartmental proligand 4-bromo-3,5-bis{6-(2,2'-bipyridyl)}pyrazole (HL(Br)) was synthesized and shown to form robust [2 × 2] grid complexes [Fe(II)4L(Br)4]X4 with various counteranions (X(-) = PF6(-), ClO4(-), BF4(-), Br(-)). The grid [Fe(II)4L(Br)4](4+) is stable in solution and features two high-spin (HS) and two low-spin (LS) ferrous ions in frozen MeCN, and its redox properties have been studied. Six all-ferrous compounds [Fe4L(Br)4]X4 with different counteranions and different lattice solvent (1a-f) were structurally characterized by X-ray diffraction, and their magnetic properties were investigated by Mössbauer spectroscopy and SQUID magnetometry. Variations in spin-state for the crystalline material range from the [4HS] via the [3HS-1LS] to the [2HS-2LS] forms, with some grids showing thermal spin crossover (SCO). The series of [Fe(II)4L(Br)4](4+) compounds allowed us to establish experimentally well-grounded correlations between structural distortion of the {FeN6} coordination polyhedra, quantified by using continuous shape measures, and the grid's spin-state pattern. These correlations evidenced pronounced cooperativity for the multistep SCO transitions within the grid, imparted by the strain effects of the rigid bridging ligands, and a high stability of the dimixed-spin configuration trans-[2HS-2LS] that has identical sites at opposite corners of the grid. The results are in good agreement with recent quantum chemical calculations for such molecular [2 × 2] grids featuring strongly elastically coupled vertices.
More Related Videos
Related Concept Videos
02:42Valence Bond Theory
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
03:06The Pauli Exclusion Principle
01:03Atomic Nuclei: Nuclear Spin State Overview