Substituent effects on spin-crossover Fe(II)NO pyrenylhydrazone complexes.

Multifunctional magnetic materials have broad application prospects in molecular switches and information storage. In this study, four mononuclear Fe(II) complexes are synthesized using a series of pyrenylhydrazone ligands HL. Two deprotonated ligands are coordinated to the iron(II) ions in an enolic form, leading to neutral complexes Fe(L)· with a FeNO octahedral coordination environment.

Integrating spin-dependent emission and dielectric switching in Fe catenated metal-organic frameworks.

Mechanically interlocked molecules (MIMs) including famous catenanes show switchable physical properties and attract continuous research interest due to their potential application in molecular devices. The advantages of using spin crossover (SCO) materials here are enormous, allowing for control through diverse stimuli and highly specific functions, and enabling the transfer of the internal dynamics of MIMs from solution to solid state, leading to macroscopic applications. Herein, we report the efficient self-assembly of catenated metal-organic frameworks (termed catena-MOFs) induced by stacking interactions, through the combination of rationally selected flexible and conjugated naphthalene diimide-based bis-pyridyl ligand (BPND), [M(CN)] (M = Ag or Au) and Fe in a one-step strategy.

{Gd} and {Gd} Cluster Formation Based on a Rhodamine 6G Ligand with a Magnetocaloric Effect.

Heptanuclear {Gd} (complex ) and tetradecanuclear {Gd} (complex ) were synthesized using the rhodamine 6G ligand HL (rhodamine 6G salicylaldehyde hydrazone) and characterized. Complex has a rare disc-shaped structure, where the central Gd ion is connected to the six peripheral Gd ions via CHO/μ-OH bridges. Complex has an unexpected three-layer double sandwich structure with a rare μ-O ion in the center of the cluster.

Chiral ZnLn Hexanuclear Clusters of an Achiral Flexible Ligand.

Multifunctional single-molecule magnets (SMMs) have sparked great interest, but chiral SMMs obtained via spontaneous resolution are rarely reported. We synthesized a series of chiral trinuclear hepta-coordinate lanthanide complexes [ZnLn] ( for Dy, for Tb, for Gd, and for DyY) using the achiral flexible ligand HL (2,2'-[1,2-ethanediylbis[(ethylimino)methylene]]bis[3,5-dimethylphenol]). The complexes crystallize in the chiral 6 group space, and two enantiomers of different chirality are spontaneously resolved.

Assembly of a Heterotrimetallic ZnDyIr Pentanuclear Complex toward Multifunctional Molecular Materials.

Rational selection of metal ions and organic ligands to synthesize metal-organic complexes (MOCs) is necessary for constructing multifunctional materials. Herein, we have obtained a novel heterotrimetallic ZnDyIr pentanuclear MOC by the assembly of Dy, luminescent Zn(valpn), and [Ir(HL)(ppy)]Cl metalloligands (Hppy = 2-phenylpyridine, HL = 2,2'-bipyridine-5,5'-di--benzoic acid). Single-crystal structural analysis shows that the central [Ir(L)(ppy)] bridges two ZnDy moieties using two carboxylates of L.

Magnetooptical Properties of Lanthanide(III) Metal-Organic Frameworks Based on an Iridium(III) Metalloligand.

Integrating magnetic and optical properties into a metal-organic framework (MOF) remains a great challenge. Herein, we have reasonably constructed two 3D magnetooptical MOFs by incorporating a [Ir(ppy)(bpy)]-based fluorescent metalloligand and magnetic Ln centers. The alternating arrangements of Δ- or Λ-[Ir(ppy)(bpy)] endow these MOFs with enhanced optical properties.

Heterotrimetallic NiLnFe chain complexes based on [Fe(1-CHim)(CN)].

Two phenoxo- and cyanido-bridged one-dimensional complexes NiGdFe (1) and NiDyFe (2) have been prepared. They are the first pentacyanidoferrite-bridged heterotrimetallic complexes. Magnetic studies reveal that overall ferromagnetic interactions are present in complexes 1 and 2, and complex 2 shows single-molecule magnet (SMM) behaviour with an energy barrier of 14.

Macroscopic Polarization Change via Electron Transfer in a Valence Tautomeric Cobalt Complex.

Polarization change induced by directional electron transfer attracts considerable attention owing to its fast switching rate and potential light control. Here, we investigate electronic pyroelectricity in the crystal of a mononuclear complex, [Co(phendiox)(rac-cth)](ClO)·0.5EtOH (1·0.

Structural Modulation of Fluorescent Rhodamine-Based Dysprosium(III) Single-Molecule Magnets.

Two rhodamine 6G-based mononuclear dysprosium complexes, [Dy(L)(L)](ClO)·EtO·1.5MeOH·0.5HO () and [Dy(L)(HO)(MeCN)](ClO)·2HO·MeCN () (L = salicylaldehyde rhodamine 6G hydrazone, L = 2-pyridylcarboxaldehyde benzoyl hydrazone), are synthesized, aiming at improving the magnetic behavior by modulating their coordination environment.

Cu(ii) complexes of N-rich aroylhydrazone: magnetism and catalytic activity towards microwave-assisted oxidation of xylenes.

The new aroylhydrazone N'-(di(pyridin-2-yl)methylene)pyrazine-2-carbohydrazide (HL) species, rich in N-donor sites, has been used to synthesize Cu(ii) compounds with different nuclearities, viz. the binuclear [Cu(μ-1κN,2κNO-L)(Cl)(MeOH)] (1), the octanuclear [Cu(μ-1κN,2κNO-L)(μ-Cl)(Cl)] (2) and the 1D coordination polymer [Cu(μ-1κN,2κNO,3κN-L)(μ-NO)(NO)(HO)]·nNO (3). They have been characterized by elemental analysis, FT-IR and single crystal X-ray diffraction.

Two new cobalt(II) rhodamine 6G hydrazone complexes: structure, fluorescence and magnetism.

Two new Co complexes, namely bis{N-[(6-bromopyridin-2-yl)methylidene]-2-[6-ethylamino-3-(ethyliminiumyl)-2,7-dimethyl-3H-xanthen-9-yl]benzene-1-carbohydrazonate}cobalt(II) bis(perchlorate)-dichloromethane-methanol (1/1/2), [Co(CHBrNO)](ClO)·CHCl·2CHOH or [Co(L)](ClO)·CHCl·2CHOH, (1), and the bis(tetrafluoridoborate) salt, [Co(CHBrNO)](BF)·CHCl·2CHOH or [Co(L)](BF)·CHCl·2CHOH, (2) (L is commonly 6-bromopyridine-2-carbaldehyde rhodamine 6G hydrazone), have been successfully constructed and characterized. The crystal structure analysis revealed that complexes (1) and (2) are mononuclear and have a CoNO distorted octahedral structure. The large π-conjugated xanthene moiety of the L ligand causes strong intermolecular π-π stacking interactions, yielding a supramolecular one-dimensional chain.

Rhodamine 6G-Labeled Pyridyl Aroylhydrazone Fe(II) Complex Exhibiting Synergetic Spin Crossover and Fluorescence.

Here, we use a pyridinecarbaldehyde rhodamine 6G hydrazone ligand (L) to synthesize an Fe(II) complex 1 for the search of new fluorescent-spin crossover (SCO) materials. Single-crystal structural determinations suggest that the Fe(II) ion is chelated by two ring-opened ligands (L-o) to form a FeNO coordination environment, and intermolecular π---π contacts of the xanthene groups connect the adjacent molecules to form a supramolecular one-dimensional chain. Magnetic susceptibility measurements on complex 1 show that three-step SCO takes place in the temperature range of 120-350 K, and its desolvated form 1-d exhibits SCO around room temperature ( T↑ = 343 K and T↓ = 303 K) with a wide hysteresis loop of 40 K.

Rhodamine Salicylaldehyde Hydrazone Dy(III) Complexes: Fluorescence and Magnetism.

Three new dysprosium(III) complexes [Dy(HL-o)(L)(NO)][Dy(NO)]·1.5ACE·0.5EtO (1), [Dy(L)]·2.

Iron(iii) complexes of 2-methyl-6-(pyrimidin-2-yl-hydrazonomethyl)-phenol as spin-crossover molecular materials.

Four new mononuclear Fe(iii) complexes 1-4 of 2-methyl-6-(pyrimidin-2-yl-hydrazonomethyl)-phenol (HL) have been synthesized and characterized by magnetic susceptibility measurements and single-crystal X-ray diffraction analysis. Complexes 1-3 are ionic compounds with the formula [Fe(HL)]X·nsolvent (X = ClO (1), BF (2) and Cl (3)), while complex 4 ([Fe(HL)(L)]) is neutral. The central Fe(iii) ion in complexes 1-4 is coordinated by four nitrogen and two oxygen atoms of two Schiff base ligands HL or L, and the coordination geometries of Fe are all distorted octahedral.

Chiral six-coordinate Dy(iii) and Tb(iii) complexes of an achiral ligand: structure, fluorescence, and magnetism.

Two new chiral six-coordinate lanthanide complexes (1 for Dy and 2 for Tb) have been synthesized using the achiral flexible ligand HL (2,2'-[1,2-ethanediylbis[(methylimino)methylene]]bis[4,5-dimethylphenol]). Both complexes crystallize in the chiral P1 group space, and the enantiomers [Zn(L)Cl]Dy·MeOH·0.5HO (Λ-1), [Zn(L)Cl]Dy·1.

Slow Magnetic Relaxation in a Mononuclear Ruthenium(III) Complex.

The development of magnetic molecules with long spin reversal/decoherence times highly depends on the understanding of relaxation behavior under different external conditions. Herein, a magnetic study on a Ru complex (1) is presented. Detailed analysis of the relaxation time and the magneto-heat capacity data suggests that the resonant phonon trapping process dominates the magnetic relaxation in the crystalline sample of 1, slowing down the spin relaxation rate, as further confirmed by the measurements on a ground sample and frozen solution.

Metallocyclic NiLnM single-molecule magnets.

We herein report the synthesis, crystal structure and magnetic properties of nine new heterotrimetallic complexes. [Ni(Mevalpn)] (HMevalpn = N,N'-bis(3-methoxysalicylidene)-2,2-dimethyl-1,3-diaminopropane) was used as the precursor to construct phenoxo-bridged [NiLn] (Ln = Dy, Tb, Gd and Y) species that were respectively connected by two [M(CN)] (M = Cr, Fe or Co) anions to form octanuclear cyclic complexes, i.e.

Porous Coordination Polymers Based on {Mn6} Single-Molecule Magnets.

In this paper, three isostructural porous coordination polymers, namely, [Mn6(μ3-O)2(sao)6(DMF)4(L(1))2/3]·4DMF·2H2O·2CH3OH (1), [Mn6(μ3-O)2(sao)6(DMF)4(L(2))2/3]·4DMF·2H2O·2CH3OH (2), and [Mn6(μ3-O)2(sao)6(DMF)4(L(3))2/3]·4DMF·4H2O·2CH3OH (3) (DMF = dimethylformamide, H2sao = salicylaldoxime, H3L(1) = benzene-1,3,5-trisbenzoic acid, H3L(2) = 4,4',4″-s-triazine-2,4,6-triyltribenzoic acid, and H3L(3) = 2,4,6-tris(4-carboxyphenoxy)-1,3,5-s-triazine), based on the oximato-bridged {Mn6} single-molecule magnet (SMM) and tricarboxylic acid ligands, were designed and synthesized. X-ray structural analysis shows that they possess a two-dimensional layered structure, where the {Mn6} moieties are linked by the corresponding (L(x))(3-) carboxylate ligands (x = 1, 2, 3) forming a huge honeycomb layer. These compounds not only show the SMM behavior as confirmed by alternative current susceptibility measurements but also show selectivity for CO2 over N2 at 273 K.

Solid state reconstructive phase transition from porous supramolecular network to porous coordination polymer.

Herein, we present an exceptional structural transformation from a porous supramolecular network to a porous coordination polymer. The transformation involves a change of interpenetrating dimensionality from 6-fold to 5-fold. Simultaneously, the spin state of nickel(ii) is altered from S = 0 to S = 1, which is concomitant with the formation of the Ni-O(carboxylate) coordination bonds.

Silver complexation by metallacryptates.

We report the first complete characterization of metallycryptates encapsulating Ag(I) cations: carboxylato ligands derived from l-proline and l-alanine chelate and bridge six Cu(II) centres arranged in a slightly distorted octahedral fashion. Eight oxygen atoms of these ligands are disposed in square-prismatic geometry and coordinate the monovalent cation. Two alternative metallacryptates based on alanine have been identified which differ with respect to aggregation: a solid in which pairs of encapsulating sites are formed competes with an infinite chain of M(I) coordinating sites.

A trimetallic strategy towards ZnDyCr and ZnDyCo single-ion magnets.

Two cyano- and phenoxo-bridged octanuclear complexes ZnDyCo (complex ) and ZnDyCr (complex ) with diamagnetic Zn(ii) and Co(iii) are reported. Dy(iii) is surrounded by nine oxygen atoms of two [Zn(Me2valpn)] (Me2valpn(2-) = dianion of N,N'-2,2-dimethylpropylenebis(3-methoxysalicylideneimine)) and one water molecule. Magnetic studies reveal that both exhibit single-ion magnet (SIM) behavior with the energy barrier of 85.

Slow magnetization relaxation in Ni(II)Dy(III)Fe(III) molecular cycles.

Two cyano- and phenoxo-bridged hexanuclear Ni(II)2Dy(III)2Fe(III)2 (1) and octanuclear Ni(II)4Dy(III)2Fe(III)2 (2) trimetallic cyclic complexes have been obtained. They are the first trimetallic metallocycles. Magnetic studies reveal that 1 and 2 exhibit single-molecule-magnet behavior with an energy barrier of 17.

Heterodinuclear M(II)-Ln(III) single molecule magnets constructed from exchange-coupled single ion magnets.

The synthesis and characterization of four dinuclear 3d-4f complexes [M(II)Ln(III)(L)(DBM)3] (ZnDy = 1, CoY = 2, CoDy = 3·3.5CH3CN, CoGd = 4·3.5CH3CN) are reported (H2L = N,N'-dimethyl-N,N'-(2-hydroxy-3-methoxy-5-methyl-benzyl)ethylenediamine, DBM(-) = anion of 1,3-diphenyl-propane-1,3-dione).

Toward higher nuclearity: tetranuclear cobalt(II) metallogrid exhibiting spin crossover.

Supramolecular strategy was employed to achieve the highest nuclearity Co(II) cluster exhibiting spin-crossover (SCO) behavior. Magnetic susceptibility characterization of the Co4(II) complex shows that two different spin-transition processes occur. The SCO behavior is directed by the partially deprotonated polydentate ligand, which favors the structural distortion required by the spin transition.

In Situ Formation of Semichelating Ligands: A Strategy for Tuning the Magnetic Coupling in Azide-Bridged Copper(II) Complexes.

Five Cu complexes of trinuclear [Cu (L ) (N ) ] (1), one-dimensional chain [Cu (L ) (N ) ]  (2), trinuclear [Cu (L ) (N ) ] (3) and dinuclear [Cu (L ) (N ) Cl ] (4) and [Cu (L ) (N ) Cl ] (5) (L =RCH OR', R=substituted pyrazole or imidazole, R'=Me, Et or nPr) were synthesized by the reaction of CuCl ⋅2 H O, sodium azide with RCH Cl in CH OH, C H OH or n-C H OH. The ether ligands L and L can be alternatively prepared by the alcoholysis of RCH Cl in the presence of sodium azide, whereas the ligands L form in corresponding alcohols without azide. For complexes 1-5, the oxygen atom of the ether ligands is located at the Jahn-Teller axis of Cu with the long CuO separations of 2.