Jing-Yuan Ge

Modulating Single-Molecule Magnetic Behavior of a Dinuclear Erbium(III) Complex by Solvent Exchange

[Er2(thd)4Pc]·2C6H6 (1) (Hthd = 2,2,6,6-tetramethylheptanedione), obtained as green crystals from the reaction of [Er(thd)3]·2H2O with lithium phthalocyanine, Li2Pc, is a stable dinuclear complex with two ErIII centers. Its lattice benzene solvent can be exchanged by soaking the crystals in dichloromethane to give [Er2(thd)4Pc]·2CH2Cl2 (2). The magnetic susceptibility data suggest different coupling interactions for the two complexes. While 1 exhibits fast relaxation and an estimated energy barrier of Ea = 2.6 cm-1 under 600 Oe dc field, the single-molecule magnet behavior of 2 is field-induced and the energy barrier is higher at 34.3 cm-1. Ab initio calculations were performed to understand the nature of the coupling interaction between two ErIII ions bridged by the phthalocyanine and the origin of different magnetic behavior. Importantly, the single-molecule magnetic properties can be reversibly tuned through the exchange of solvent molecules, confirmed by further measurements on the reverse solvated complexes 1-re and 2-re. This subtle control of relaxation by lattice solvents is rarely observed in single-molecule magnets, especially for ErIII-based complexes.

Modulating the Magnetic Interaction in New Triple-Decker Dysprosium(III) Single-Molecule Magnets

A new type of dinuclear dysprosium(III) complex based on phthalocyanine and salicylaldehyde derivatives (HL-R), [Dy2(Pc)2(L-R)2(H2O)]·2THF (R = OCH3 (1), OC2H5 (2); H2Pc = phthalocyanine; HL-OCH3 = 2-hydroxy-3-methoxybenzaldehyde; HL-OC2H5 = 3-ethoxy-2-hydroxybenzaldehyde), was successfully synthesized and structurally characterized. Complex 1 features a sandwich-type triple-decker structure, where two coplanar L-OCH3 ligands lie in the middle layer shared by two eight-coordinated DyIII ions and two Pc ligands are located in the outer layer. In 2, the introduction of an ethoxy group generates a noncoordination mode for the Oalkoxy atom. Magnetic studies indicate that complex 1 behaves as a zero-field single-molecule magnet with a higher energy barrier, while 2 exhibits a fast tunneling relaxation process. Theoretical calculations revealed that changes in the ligand field environment around DyIII ions can significantly affect the arrangement of the main magnetic axes and further result in distinct magnetic interactions as well as different relaxation behaviors.

Redox-switchable breathing behavior in tetrathiafulvalene-based metal–organic frameworks

Metal–organic frameworks (MOFs) that respond to external stimuli such as guest molecules, temperature, or redox conditions are highly desirable. Herein, we coupled redox-switchable properties with breathing behavior induced by guest molecules in a single framework. Guided by topology, two flexible isomeric MOFs, compounds 1 and 2, with a formula of In(Me2NH2)(TTFTB), were constructed via a combination of [In(COO)4]− metal nodes and tetratopic tetrathiafulvalene-based linkers (TTFTB). The two compounds show different breathing behaviors upon the introduction of N2. Single-crystal X-ray diffraction, accompanied by molecular simulations, reveals that the breathing mechanism of 1 involves the bending of metal–ligand bonds and the sliding of interpenetrated frameworks, while 2 undergoes simple distortion of linkers. Reversible oxidation and reduction of TTF moieties changes the linker flexibility, which in turn switches the breathing behavior of 2. The redox-switchable breathing behavior can potentially be applied to the design of stimuli-responsive MOFs.Modulating the adsorption behaviours of metal-organic frameworks using external stimuli is desirable, but challenging to achieve. Here, Zhou and colleagues design an indium-based MOF in which tetrathiafulvalene ligands undergo reversible redox reactions that alter the framework breathing behaviour.

Magnetic Anisotropy along a Series of Lanthanide Polyoxometalates with Pentagonal Bipyramidal Symmetry

Magneto-structural correlations in a series of lanthanide polyoxometalates (POMs) with pentagonal bipyramidal symmetry, namely, [Ln2(NMP)12(PW12O40)][PW12O40] (NMP is N-methyl pyrrolidone), were studied in detail experimentally combined with theoretical calculations. Furthermore, two types of Dy-based complexes with pentagonal bipyramidal symmetry were built to discuss the dependence of the theoretical energy barriers with the axial Dy-O bond lengths when the magnetic axes in ground Kramers doublet are along the axial orientation or on the equatorial plane. A meaningful conclusion was put forward for designing such Dy-based SIMs with high performance.

Thiacalix[4]arene-supported heterodinuclear NiII–LnIII complexes: slow magnetic relaxation behavior in the dysprosium analogue

Three heterodinuclear complexes, [(NiL1)Ln(L2)(CH3OH)]·acetone (Ln = Gd (1), Tb (2), Dy (3); H3L1 = 1,1,1-tris[(salicylideneamino)methyl]ethane), were stepwise synthesized based on a thiacalix[4]arene ligand (H2L2 = 5,11,17,23-tetrakis(1,1-dimethylethyl)-25,27-dihydroxy-26,28-dimethoxy thiacalix[4]arene). In 1–3, NiII and LnIII ions are doubly bridged by two phenoxo O atoms of L1. The NiII ion, only coordinated by the L1 ligand, features a {NiN3O3} coordination sphere; and the LnIII ion adopts a seven-coordinated {LnO7} environment, capped by one thiacalix[4]arene ligand in a bowl-shaped conformation. Magnetic studies on all complexes reveal that ferromagnetic couplings are operative between the NiII and LnIII ions. The dysprosium analogue (3) exhibits field-induced single-molecule magnet (SMM) behavior under a dc-applied field of 800 Oe. Moreover, the Dy:Y (1:10) magnetically diluted sample (3′) shows slow magnetic relaxation at zero dc field. The results demonstrate that the stepwise synthetic method is more useful and effective than self-assembly for designing new 3d–4f heterodinuclear complexes with the thiacalix[4]arene ligand or other derivatives. The introduction of this type of thiacalix[4]arene ligand into the heterodinuclear complexes renders them promising candidates for new SMMs.

The new dicyanoruthenium(III) building block with 2′-hydroxyacetophenone imine for heterobimetallic complexes

A new ruthenium(III)-based building block, trans-(Ph4P)[RuIII(L)2(CN)2] (L = 2′-hydroxyacetophenone imine), has been synthesized and characterized. Reactions of this building block with different MnIII Schiff base (SB) complexes, [Mn(SB)(H2O)2]ClO4, result in 1-D zigzag chain complexes, [RuIII(L)2(CN)2MnIII(SB)]n (SB = salen, 1; salcy, 2; nappa, 4; napcy, 5), respectively. X-ray crystallographic studies reveal that each of the MnIII centers has a distorted octahedral environment, while complex 3 possesses a single cationic chain structure consisting of [Cu(chxn)2][Ru(L)2(CN)2]n units and their corresponding [Ru(L)2(CN)2]− anions. Compounds 1–3 exhibit antiferromagnetic coupling between the RuIII and MnIII/CuII centers, whereas 4 and 5 reveal ferromagnetic coupling between the RuIII and MnIII centers through the cyano bridges. Furthermore, magneto-structural correlation for some typical cyano-bridged heterobimetallic RuIII–MnIII/CuII compounds is discussed.

Controlling the assembly and spin transport of tetrathiafulvalene carboxylate coated iron oxide nanoparticles

We report a solution phase based assembly method to tune the transport mechanism and magnetoresistance (MR) of Fe3O4 nanoparticles (NPs). The NP topological arrangement is altered by the NP coating of tetrathiafulvalene carboxylic acid (TTFCOOH) or its dicarboxylic analogue (TTF(COOH)2). Consequently, the transport mechanism of the assembly switches from tunneling to Mott hopping. The MR ratios of the Fe3O4 NP assemblies can be further tuned by the polarity of the solvent used in the ligand exchange process. The TTF(COO)2-coated Fe3O4 NP assembly has a 5% room temperature MR ratio, which is the highest value among all TTF-COO-Fe3O4 NP assemblies reported so far.

CCDC 1487767: Experimental Crystal Structure Determination

Related Article: Fei Yu, Zi-Heng Cao, Jing-Yuan Ge, Yi-Chen Sun, Zhong-Wen Ouyang, Jing-Lin Zuo, Zhenxing Wang, Mohamedally Kurmoo|2017|Dalton Trans.|46|4317|doi:10.1039/C7DT00110J

Structure-dependent electronic transition in a new type of π-electron delocalized multi-sulfur bis(dithiolene)nickel complex

Four new nickel bis(dithiolene) complexes with different substituent groups on their benzene rings were synthesized and characterized. X-ray structure analysis reveals that the anions of these Ni-complexes exhibit chair-like configurations. Magnetic measurements confirm that compounds 1–4 show antiferromagnetic interactions. The absorption spectra show strong and broad absorptions in the near-infrared region (700–1100 nm). Density functional theory (DFT) calculations indicate that the HOMO and LUMO energy levels are highly dependent on the electron donating/withdrawing abilities of the substituents. The electron-donating substituent results in a bathochromic-shift absorption, while the electron-withdrawing substituent leads to a hypsochromic-shift absorption band. Moreover, the results of solution-state electrochemical studies also show a good agreement with our findings in spectroscopic and DFT studies.