The effect of magnetic coupling along the magnetic axis on slow magnetic relaxation in DyIII complexes with D5h configuration based on an aggregation-induced-emission-active ligand.

The adjustment of crystal symmetry and intramolecular magnetic coupling is of great importance for the construction of high-performance single-molecule magnets. By using an aggregation-induced-emission-active pyridine-carbohydrazone-based Schiff base ligand and phosphine oxides, four dinuclear and one one-dimensional DyIII-based complexes, [Dy2(TPE-pc)2(Bu3PO)2Cl2]·2CH3CN·2H2O (1), [Dy2(TPE-pc)2(Cy3PO)2Cl2] (2), [Dy2(TPE-pc)2(MePA)2Cl2]·2CH3OH (3), [Dy2(TPE-pc)2(Ph3PO)2Cl2]2 (4) and [Dy2(TPE-pc)2(DPPO)Cl2]n (5) (H2TPE-pc = (E)-N'-(2-hydroxy-5-(1,2,2-triphenylvinyl)benzylidene)picolinohydrazide, MePA = N-phenyl-N',N''-bis(morpholinyl) phosphoric triamide, DPPO = piperazine-1,4-diylbis(diphenyl phosphine oxide)), were isolated. All complexes are made up of an enol oxygen-bridged Dy2 unit, where DyIII ions possess a pentagonal bipyramidal geometry with pseudo D5h symmetry. Magnetic measurements reveal that intramolecular DyIII-DyIII couplings are ferromagnetic and all complexes display a significant slow magnetic relaxation phenomenon below 30 K under a zero dc field. Ab initio calculations indicate that the anisotropic magnetic axes of all DyIII ions are approximately perpendicular to the higher-order symmetric axes in all complexes, and that DyIII-DyIII magnetic couplings along the magnetic axes effectively suppress the ground state quantum tunneling effect of magnetization and promote the occurrence of slow magnetic relaxation. Raman relaxation prevails in all complexes. In addition, the H2TPE-pc ligand shows an aggregation-induced emission (AIE) effect; however, all complexes exhibit an aggregation-caused quenching (ACQ) phenomenon.

Rare single-molecule magnets with six-coordinate Ln(III) ions exhibiting a trigonal antiprism configuration.

Four Ni-Ln-Ni heterometallic complexes, [Ni2LnL2]NO3·3H2O (H3L = tri(((3-methoxysalicylidene)amino)ethyl)amine, Ln = Gd for , Tb for and Dy for , respectively) and [Ni2DyL2]ClO4·MTBE·0.65H2O (, MTBE = methyl tert-butyl ether) have been synthesized by diffusion of methyl tert-butyl ether vapor into the reaction solution. The X-ray analyses demonstrated that the Gd(III) ion in exhibits rare seven-coordination, the Tb(III) and Dy(III) ions in display unusual six-coordination, and two Ni(II) ions and one Ln(III) ion are bridged by six phenolato atoms to form linear Ni-Ln-Ni heterotrinuclear complexes for . All complexes exhibit weak ferromagnetic interactions between Ni(II) and Ln(III) ions. Alternating current susceptibility measurements demonstrated that compounds and behave as single-molecule magnets with the effective energy barriers of 14.17 and 11.13 K under zero direct current field. They are rare single-molecule magnets containing six-coordinate Dy(III) ions.

Crystal structures and magnetic properties of chiral heterobimetallic chains based on the dicyanoruthenate building block.

By the reaction of chiral Mn(III) Schiff-base complexes with the dicyanoruthenate building block, [Ru(salen)(CN)2](-) (salen(2-) = N,N'-ethylenebis(salicylideneimine) dianion), two couples of enantiomerically pure chiral cyano-bridged heterobimetallic one-dimensional (1D) chain complexes, [Mn((R,R)-salcy)Ru(salen)(CN)2]n (1-(RR)) and [Mn((S,S)-salcy)Ru(salen)(CN)2]n (1-(SS)) (Salcy = N,N'-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [Mn((R,R)-salphen)Ru(salen)(CN)2]n (2-(RR)) and [Mn((S,S)-salphen)Ru(salen)(CN)2]n (2-(SS)) (salphen = N,N'-(1,2-diphenylethylene)bis(salicylideneiminato) dianion), were synthesized and structurally characterized. Circular dichroism (CD) and vibrational circular dichroism (VCD) spectra confirm the enantiomeric nature of the optically active complexes. Structural analyses reveal the formation of neutral cyano-bridged zigzag single chains in 1-(RR) and 1-(SS), and double chains in 2-(RR) and 2-(SS). Magnetic studies show that antiferromagnetic coupling is operative between Ru(III) and Mn(III) centers bridged by cyanide. Compounds 1-(RR) and 1-(SS) show metamagnetic behavior with a critical field of about 7.2 kOe at 1.9 K resulting from the intermolecular π∙∙∙π interactions. Additionally, magnetostructural correlation for some typical cyano-bridged heterobimetallic Ru(III)-Mn(III) compounds is discussed.

Enantiopure heterobimetallic single-chain magnets from the chiral Ru(III) building block.

A pair of one-dimensional enantiomers based on the versatile chiral dicyanoruthenate(III) building block have been synthesized and they are chiral single-chain magnets with the effective spin-reversal barrier of 28.2 K.

Syntheses, structures, and magnetic properties of seven-coordinate lanthanide porphyrinate or phthalocyaninate complexes with Kläui's tripodal ligand.

A series of seven-coordinate mononuclear lanthanide(III) complexes of the general formula [(TPP)Ln(L(OEt))]·0.25H2O and [(Pc)Ln(L(OEt))] (Ln(3+) = Dy(3+), Tb(3+), Ho(3+), and Gd(3+); TPP = 5,10,15,20-tetraphenylporphyrinate; Pc = phthalocyaninate; L(OEt)(-) = [(η(5)-C5H5)Co(P(=O)(OEt)2)3](-)) are synthesized on the basis of the tripodal ligand L(OEt)(-) and either porphyrin or phthalocyanine ligands. All of the complexes are characterized by X-ray crystallography and by static and dynamic magnetic measurements. The Dy and Tb complexes show the field-induced slow relaxation of magnetization, and they are interesting seven-coordinate single-lanthanide-based SMMs. The magnetic relaxation properties of these double-decker sandwich complexes are influenced by the local molecular symmetry and are sensitive to subtle distortions of the coordination geometry of the paramagnetic lanthanide ions, such as metal-to-plane distances, plane center distances, and bending angles.

Controlled synthesis of heterotrimetallic single-chain magnets from anisotropic high-spin 3 d-4 f nodes and paramagnetic spacers.

By using the node-and-spacer approach in suitable solvents, four new heterotrimetallic 1D chain-like compounds (that is, containing 3d-3d'-4f metal ions), {[Ni(L)Ln(NO(3))(2)(H(2)O)Fe(Tp*)(CN)(3)]⋅2 CH(3)CN⋅CH(3)OH}(n) (H(2)L = N,N'-bis(3-methoxysalicylidene)-1,3-diaminopropane, Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate; Ln = Gd (1), Dy (2), Tb (3), Nd (4)), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide- and phenolate-bridged heterotrimetallic chain, with a {-Fe-C≡N-Ni(-O-Ln)-N≡C-}(n) repeat unit. Within these chains, each [(Tp*)Fe(CN)(3)](-) entity binds to the Ni(II) ion of the [Ni(L)Ln(NO(3))(2)(H(2)O)](+) motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO(3))(2)(H(2)O)](+) unit is linked to two [(Tp*)Fe(CN)(3)](-) ions through the Ni(II) ion in a trans mode. In the [Ni(L)Ln(NO(3))(2)(H(2)O)](+) unit, the Ni(II) and Ln(III) ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1-4 are rare examples of 1D cyanide- and phenolate-bridged 3d-3d'-4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe(III) and Ni(II) ions through a cyanide bridge and between neighboring Ni(II) and Ln(III) (except for Nd(III) ) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single-chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d-4f heterotrimetallic single-chain magnets.

Field-induced slow magnetic relaxation in chiral seven-coordinated mononuclear lanthanide complexes.

Four couples of enantiomerically pure chiral seven-coordinated mononuclear lanthanide complexes, [(L(OEt))Dy((R,R)-Salphen)](2)·3H(2)O (1, L(OEt) = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene, Salphen = N,N'-1,2-diphenylethylenebis(salicylideneiminato) dianion), [(L(OEt))Dy((S,S)-Salphen)](2)·3H(2)O (2), [(L(OEt))Dy((R,R)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (3, Salcy = N,N'-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [(L(OEt))Dy((S,S)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (4), [(L(OEt))Tb((R,R)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (5), [(L(OEt))Tb((S,S)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (6), [(L(OEt))Ho((R,R)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (7) and [(L(OEt))Ho((S,S)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (8), have been successfully synthesized by using tetradentate chiral salen-type ligands and the Kläui's tripodal ligand of L(OEt). Structural analyses reveal that all compounds have a typical double-decker sandwich structure, and the Ln(iii) ions exhibit a rare seven-coordinated mode, situating in a distorted monocapped triangular prism polyhedron. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes and demonstrate that the chirality is successfully transferred from the ligand to the coordination environment of the Ln(iii) ions. Field-induced slow relaxation of the magnetization is observed for complexes 1-4, suggesting that they can be rare chiral single-ion magnets (SIMs) based on the seven-coordinated lanthanide ions.

Chiral cyanide-bridged Cr(III)-Mn(III) heterobimetallic chains based on [(Tp)Cr(CN)3]-: synthesis, structures, and magnetic properties.

By the reactions of Mn(III) Schiff-base complexes with the tricyanometalate building block, [(Tp)Cr(CN)(3)](-) (Tp = Tris(pyrazolyl) hydroborate), two couples of enantiomerically pure chiral cyano-bridged heterobimetallic one-dimensional (1D) chain complexes, [Mn((R,R)-Salcy)Cr(Tp)(CN)(3)·1/4H(2)O·1/2CH(2)Cl(2)](n) (1) and [Mn((S,S)-Salcy)Cr(Tp)(CN)(3)·1/4H(2)O·1/2CH(2)Cl(2)](n) (2) (Salcy = N,N'-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [Mn((R,R)-Salphen)Cr(Tp)(CN)(3)](n) (3) and [Mn((S,S)-Salphen)Cr(Tp)(CN)(3)](n) (4) (Salphen = N,N'-1,2-diphenylethylene-bis(salicylideneiminato) dianion), have been successfully synthesized. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes. Structural analyses reveal the formation of neutral cyano-bridged zigzag single chains in 1 and 2, and neutral cyano-bridged zigzag double chains in 3 and 4. Magnetic studies show that antiferromagnetic couplings are operative between Cr(III) and Mn(III) centers bridged by cyanide. Complexes 1 and 2 are the rare examples of chiral ferrimagnets; while complexes 3 and 4 exhibit a coexistence of chirality and spin-glass behavior in a 1D chain.

Syntheses, structures, and magnetic properties of low-dimensional heterometallic complexes based on the versatile building block [(Tp)Cr(CN)3]-.

Using the tricyano precursor (Bu(4)N)[(Tp)Cr(CN)(3)] (Bu(4)N(+) = tetrabutylammonium cation; Tp = tris(pyrazolyl)hydroborate), a pentanuclear heterometallic cluster [(Tp)(2)Cr(2)(CN)(6)Cu(3)(Me(3)tacn)(3)][(Tp)Cr(CN)(3)](ClO(4))(3)·5H(2)O (1, Me(3)tacn = N,N',N'-trimethyl-1,4,7-triazacyclononane), three tetranuclear heterometallic clusters [(Tp)(2)Cr(2)(CN)(6)Cu(2)(L(OEt))(2)]·2.5CH(3)CN (2, L(OEt) = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene), [(Tp)(2)Cr(2)(CN)(6)Mn(2)(L(OEt))(2)]·4H(2)O (3), and [(Tp)(2)Cr(2)(CN)(6)Mn(2)(phen)(4)](ClO(4))(2) (4, phen = phenanthroline), and a one-dimensional (1D) chain polymer [(Tp)(2)Cr(2)(CN)(6)Mn(bpy)](n) (5, bpy = 2,2'-bipyridine) have been synthesized and structurally characterized. Complex 1 shows a trigonal bipyramidal geometry in which [(Tp)Cr(CN)(3)](-) units occupy the apical positions and are linked through cyanide to [Cu(Me(3)tacn)](2+) units situated in the equatorial plane. Complexes 2-4 show similar square structures, where Cr(III) and M(II) (M = Cu(II) or Mn(II)) ions are alternatively located on the rectangle corners. Complex 5 consists of a 4,2-ribbon-like bimetallic chain. Ferromagnetic interactions between Cr(III) and Cu(II) ions bridged by cyanides are observed in complexes 1 and 2. Antiferromagnetic interactions are presented between Cr(III) and Mn(II) ions bridged by cyanides in complexes 3-5. Complex 5 shows metamagnetic behavior with a critical field of about 22.5 kOe at 1.8 K.

Hexanuclear Fe(III)2Co(III)2M(II)2 (M = Cu, Ni, Mn) clusters based on Kläui's tripodal ligand and tricyanometalates: syntheses, structures and magnetic properties.

With the use of Kläui's tripodal ligand, [(Cp)Co(P(O)(OEt)(2))(3)](-) (L(CoEt), Cp = cyclopentadiene) as the auxiliary ligand to react with different metal salts and tricyanometalate building blocks, five neutral trimetallic hexanuclear complexes: [(Tp)(2)Fe(2)(CN)(6)Cu(2)(L(CoEt))(2)]·6H(2)O (1, Tp = hydridotris(pyrazolyl)borate), [(Tp*)(2)Fe(2)(CN)(6)Cu(2)(L(CoEt))(2)]·2H(2)O (2, Tp* = hydridotris(3,5-dimethyl-pyrazolyl)borate), [(pzTp)(2)Fe(2)(CN)(6)Cu(2)(L(CoEt))(2)]·H(2)O·3MeOH (3, pzTp = tetra(pyrazolyl)borate), [(Tp)(2)Fe(2)(CN)(6)Ni(2)(L(CoEt))(2)(MeCN)(2)]·2MeCN·2H(2)O (4) and [(Tp)(2)Fe(2)(CN)(6)Mn(2)(L(CoEt))(2)(MeCN)(2)]·2MeCN (5), have been obtained and structurally characterized. Magnetic measurements confirm that there are ferromagnetic couplings between the cyano-bridged Fe and Cu/or Ni ions and antiferromagnetic interaction between the cyano-bridged Fe and Mn ions. Slow relaxation of the magnetization is observed in complexes 1 and 4, while complex 3 exhibits metamagnetic behavior with a critical field of 17.5 kOe.

A unique 2D framework containing linear trimeric cobalt(II) of mixed Td-Oh-Td geometries linked by two different single-carboxylate-aromatic amine ligands: structure and magnetic properties.

A new 2D coordination polymer Co3(OH)2(pa)2(ina)2 (1, pa = 3-(1H-benzimidazol-2-yl) propanoic carboxylate, ina = isonicotinate) contained uncommon, linear Co(ii) trimers of mixed Td-Oh-Td geometries, exhibits spin canting below 20 K. Such magnetic behavior mainly arises from the Dzyaloshinski-Moriya interaction from the anisotropic, mixed geometries trimeric Co(II) ions to the crimpled 2D network based on the nature of the binding modes of Co(II)-carboxylate trimer and the effect of the intertrimers arrangement of 1. The mixed single-carboxylate-aromatic amine ligands bridged metal systems display a new structurally authenticated example of a thick 2D layer, and also indicate homometallic Co(II) clusters with Td-Oh-Td mixed-geometries can result in relatively obvious noncompensation moments, according to different efficient spins of Co(II) at very low temperature, in spite of antiferromagnetic intracluster interactions.