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Polymetallic complexes with covalently bridged metal centers that interact magnetically are important in the molecular magnetism field, with binuclear compounds receiving special attention because they represent the simplest type of multinuclear species with covalently bridged metal centers. Herein, we report the synthesis and properties of two new binuclear FeII complexes, namely, {[Fe(abpt-TPE)(NCS)2]2(bpym)}·2MeOH·2MeCN (1) and {[Fe(abpt-TPE)(NCS)2]2(bpym)}·2CH2Cl2 (2) (bpym = 2,2′-bipyrimidine). The crystal structure is analyzed at different temperatures, and its properties are analyzed by variable-temperature magnetic susceptibility and variable-temperature fluorescence emission spectroscopy tests. Variable-temperature magnetic susceptibility measurements of two binuclear compounds show different types of magnetic behavior. Complex 1 exhibits two-step spin transition behavior with an intermediate state near 150 K (Tc1 = 191 K, Tc2 = 111 K); 1 undergoes an [LS–LS] ↔ [LS–HS] ↔ [HS–HS] spin transition during thermal induction. On the other hand, complex 2 exhibits intramolecular antiferromagnetic coupling, with J = −0.47 cm−1. The analysis of correlations between the structural characteristics and different types of magnetic behaviors for two binuclear complexes, revealed that the different magnetic behaviors shown by the two complexes are attributable to different degrees of [FeN6] octahedral distortion caused by different lattice solvents, ligand strain and crystal stacking. [ABSTRACT FROM AUTHOR]

Spin doctor: A mononuclear ferric complex [Fe(H‐5‐Br‐thsa)(5‐Br‐thsa)]⋅H2O (1) (H2‐5‐Br‐thsa=5‐bromo‐2‐hydroxybenzylidene)hydrazinecarbothioamide) was synthesized and its magnetic properties and structure were investigated by DFT calculations. This complex shows unprecedented reversible, six/five‐step spin‐crossover behavior accompanied by symmetry breaking. More importantly, each step in the multi‐step transition was successfully characterized by single‐crystal X‐ray diffraction. [ABSTRACT FROM AUTHOR]

Reacting lanthanide nitrates with 2,5-pyrazinedicarboxylic acid (2,5-pzdcH2) and oxalic acid (oxH2) hydrothermally at 140 °C yielded a series of MOFs with 1D nano-sized channels, [Ln(2,5-pzdc)(ox)0.5(H2O)2]·4.5H2O (1-Ln; Ln = Nd, Sm, Eu, Gd, Tb, Dy), different from previously reported ultra-microporous [Ln(2,5-pzdc)1.5(H2O)3]·0.5H2O. While the oxalic acid was replaced by other dicarboxylic acids like terephthalic acid, malonic acid, glutaric acid, or pyrazole-3,5-dicarboxylic acid, obtained was a novel series of 1D polymers, [Ln(2,5-pzdc)0.5(2,6-pzdc)(H2O)3] (2-Ln; Ln = Pr, Sm, Eu, Tb; 2,6-pzdc2−= 2,6-pyrazinedicarboxylate), with 2,6-pzdc2−formed in situby formal carboxyl transfer. This represents the first example of carboxyl transfer either in coordination compounds or in hydrothermal synthesis. The Eu and Tb complexes in these two series emit strong ligand sensitized f–fluminescence. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Spin crossover (SCO), characterized by distinct high‐spin (HS) and low‐spin (LS) states, has potential applications in memory, electronic, and electroluminescent devices. The OFF/ON switching of SCO is crucial for obtaining bistable magnetic properties. However, there are few strategies for achieving this switching. Herein, based on a ligand chemical doping strategy, we report an Fe(III) solid solution that can be prepared using a ligand chemical doping strategy, enabling not only the OFF/ON switching of SCO but also the fine‐tuning of the spin transition temperature (Tc) within a 45 K range near room temperature. The experimental results show that when the polar ligand doping ratio reaches 20%, SCO behavior is triggered, and the crystal phase transforms significantly, becoming loose and flexible. Furthermore, Tc can be continuously regulated as the ligand‐doping ratio increases. Density functional theory (DFT) calculations reveal that solid packing‐induced molecular distortion blocks SCO, whereas loosely flexible packing triggers SCO via fluorinated ligand chemical doping. [ABSTRACT FROM AUTHOR]

We report three self-assembled iron complexes that comprised an anti-parallel open form (o-L anti ), a parallel open form (o-L syn ), and a closed form (c-L) of diarylethene conformers. Under kinetic control, Fe II 2 (o-L anti ) 3 was isolated, which exhibited a dinuclear structure with diamagnetic properties. Under light-irradiation control, Fe II 2 (c-L) 3 was prepared and exhibited paramagnetism and spin-crossover behaviour. Under thermodynamic control and in the presence of indispensable [Fe III (Tp*)(CN) 3 ] - , Fe II 2 (o-L anti ) 3 and Fe II 2 (c-L) 3 transformed into tetranuclear Fe III 2 Fe II 2 (o-L syn ) 2 , which exhibited complete spin-crossover behaviour at T 1/2 =353 K., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the title complex, [Fe(NCS)2(C18H18N4)], the Fe(II) cation is chelated by a tris-(2-pyridyl-meth-yl)amine ligand and coordin-ated by two thio-cyanate anions in a distorted N6 octa-hedral geometry. In the crystal, weak C-H⋯S hydrogen bonds and π-π stacking inter-actions between parallel pyridine rings of adjacent mol-ecules [centroid-centroid distance = 3.653 (3) Å] link the mol-ecules into a two-dimensional supra-molecular architecture. The structure contains voids of 124 (9) Å(3), which are free of solvent molecules.

Spin doctor: A mononuclear ferric complex [Fe(H-5-Br-thsa)(5-Br-thsa)]⋅H2O (1) (H2-5-Br-thsa = 5-bromo-2-hydroxybenzylidene)hydrazinecarbothioamide) was synthesized and its magnetic properties and structure were investigated by DFT calculations. This complex shows unprecedented reversible, six/five-step spin-crossover behavior accompanied by symmetry breaking. More importantly, each step in the multi-step transition was successfully characterized by single-crystal X-ray diffraction., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The three-dimensional polymeric title compound, {[Zn(C(9)H(4)N(2)O(4))]·H(2)O}(n), contains one crystallographically independent Zn(II) atom, one fully deprotonated 1H-benzimid-azole-5,6-dicarboxyl-ate (bdc) ligand and one uncoordinated water mol-ecule. The Zn(II) atom is four-coordinated by three O atoms and one N atom from the bdc ligands, giving a distorted tetra-hedral coordination geometry. The uncoordinated water mol-ecule is bound to the main structure through a strong bdc-water N-H⋯O hydrogen bond, and two much weaker water-bdc O-H⋯O inter-actions.