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Based on a β-diketonate ligand, a mononuclear Dy(III) complex, [Dy(dmpd)3(bpy)] (1) (dmpd = 4,4-dimethyl-1-phenylpentane-1,3-dione, bpy = 2,2′-dipyridyl), of [DyN2O6] type has been synthesized with a capping nitrogen-containing coligand. Then, a dual capping coligand 2,2′-bipyrimidine (bmp) is introduced to be a bridge to link two β-diketonate-Dy(III) motifs, leading to a new dinuclear Dy(III) complex, [Dy2(dmpd)6(bmp)] (2). Dy(III) centers in both complexes feature an N2O6 octacoordinated environment with an approximate square-antiprism geometry (D4d). Without a dc field, the SMM behaviour is absent in complex 1, but can be clearly observed in dinuclear 2 with a Ueff of 87.29 K. The significantly improved magnetism arising in 2 is mainly due to the modulation of the coordination environment around the Dy(III) ions and the superexchange magnetic interactions inside the dinuclear units, thus allowing for the effective inhibition of the quantum tunneling of magnetization at low temperatures and promotion of the uniaxial magnetic anisotropy. For 1, a diamagnetic Y(III) analogue [Y(dmpd)3(bpy)] (3) and diluted sample 1@Y were constructed to further perform the dilution experiment, coupled with theoretical calculations further supporting that the synergetic contributions of intermolecular dipole–dipole interactions, intramolecular coupling and uniaxial magnetic anisotropy cause the enhancement of dynamic magnetic relaxation. [ABSTRACT FROM AUTHOR]

Precise control of the crystal field and local symmetry around the paramagnetic spin center is crucial for the design and synthesis of single-molecule magnets (SMMs). Herein, three mononuclear Dy(III)-based complexes, [Dy(LN6)(CH3COO)2](BPh4)(CH2Cl2) (1), [Dy(LN6)(2,6-Cl-4-NO2-PhO)(H2O)2]2(PF6)2(H2O)(2,6-Cl-4-NO2-PhO)2 (2) and [Dy(LN6)(2,6-Cl-4-NO2-PhO)2](BPh4)(CH2Cl2)2 (3) (LN6 = N6-hexagonal plane accomplished by a neutral Schiff base ligand formed from 2,6-diacetylpyridine and ethylenediamine), are successfully isolated. In these complexes, the Dy(III) centers are coordinated with six neutral N atoms from a nonrigid equatorial ligand, while different oxygen-bearing ligands are arranged at the axial positions of the central ions by gradual regularization of the axial ligands. As a result, Dy(III) ions in the three complexes exhibit various coordination geometries, forming a ten-coordinate tetradecahedron for 1, a nine-coordinate muffin configuration for 2 and a distorted eight-coordinate hexagonal bipyramid for 3. Magnetic studies reveal that all complexes exhibit no SIM behaviour under zero dc field, due to the predominant quantum tunneling of magnetization (QTM), which can be effectively suppressed by additional dc fields. Experiments, coupled with theoretical calculations, demonstrate that varying local symmetries and coordination geometries are synergistically responsible for the disparities of QTM and uniaxial anisotropy, resulting in notably different magnetic properties. [ABSTRACT FROM AUTHOR]

Two five‐coordinate mononuclear DyIII single‐molecule magnets [(TrapenTMS)Dy(L)] (Trapen=tris(2‐aminobenzyl) amine; TMS=SiMe3; L=OPMe31, OPEt32) have been synthesized by the reaction of [(TrapenTMS)Dy(THF)] and OPMe3, OPEt3, respectively. The molecular structures of 1 and 2 were fully established by single crystal X‐ray diffraction. The centre DyIII ions of both complexes exhibit distorted triangular bipyramid geometries, varying with different neutral ligands L on the apex. The TrapenTMS ligand forms the pyramid base of the trigonal bipyramid. Subtle structural modifications of the axial O‐ligand terminal substituent result in different dynamic magnetic behaviors. Magnetic data analysis reveals that 1 and 2 exhibit the characteristic behavior of SMM without a dc field, accompanying an unambiguous quantum tunneling of the magnetization. Field‐induced slow magnetic relaxation was observed for 1 and 2 under an applied bias dc field of 1000 Oe, the relaxation energy barriers are 107 K and 88 K for 1 and 2, respectively. We have investigated the differences in magnetism and magnetic anisotropy between the two complexes by ab initio calculations. [ABSTRACT FROM AUTHOR]

The theoretical understanding of the magneto‐structural correlations of an oximato‐bridged dinuclear copper(II) complex can help develop new applied molecular magnets. This study evaluated the magnetic coupling constant of a [Cu2(hfac)2(ppko)2] complex using the density functional theory combined with the broken symmetry approach (DFT‐BS). The magnetic structure correlation between the magnetic coupling constant (Jcalc) of the complex and the structural parameters, NOCu bond angle (α), ONCu bond angle (β), NO bond length (RN‐O), and Cu•••Cu distance (R0), was evaluated. The data showed that Jcalc initially decreased and then increased as bond angles α and β increased. These relationships were expressed by unary quadratic functions. However, Jcalc varied linearly with the bond length, RN‐O, and spacing, R0. Moreover, in the ground state, the magnetic coupling constant increased with a decrease in the spin density of Cu(1), but gradually decreased as the spin density of Cu(2) increased. An increase of parameters α, β, RN‐O, and R0, resulted in a gradual increase in the distance between Cu(II) ions, and the square of the overlap integral between the non‐orthogonal magnetic orbitals of Cu(II) ions to gradually decay. Finally, the contribution of the antiferromagnetic part decreased as the magnetic coupling constant gradually increased. [ABSTRACT FROM AUTHOR]

Two isomeric Co(II) complexes with the same general molecular formula of [Co(napy)2(NO3)2] (napy = 1,8-naphthyridine) have been synthesized. X-ray single crystal structural determination demonstrates that the two compounds exhibit highly irregular six- (1) and seven-coordinate (2) geometries, respectively. The magnetic measurements, X-band EPR data and theoretical calculations were thoroughly investigated. Both complexes show field-induced slow magnetic relaxation, of which the slow magnetic relaxation in 2 is attributed to an easy-plane anisotropy. [ABSTRACT FROM AUTHOR]

A new Co(II)-based compound with a 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole (4-Hppt) and isophthalic acid (H2ip) mixed ligand, [Co[(4-Hppt).sub.2](ip)] (1), has been synthesized and structurally and magnetically characterized. The structure of compound 1 consists of one-dimensional coordination chains based on the [Co.sub.2] units bridged by dual carboxylate groups, where the pyridyl nitrogen atoms in 4-Hppt ligands are located in the axial coordination sites of the octahedral Co(II) nodes. Magnetic investigation suggests that the magnetic coupling derived from the dinuclear Co(II) ions is a moderately antiferromagnetic exchange in the title compound. Moreover, DFT calculations have been performed on the compound to offer a qualitatively theoretical explanation of the magnetic behavior. Key words: cobalt(II) compound, isophthalic acid, triazole pyridine, dimeric metal unit, magnetic properties. Nous avons realise la synthese d'un nouveau compose a base de Co(II), le compose [Co[(4-Hppt).sub.2](ip)] (1), possedant un ligand mixte de 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole (4-Hppt) et d'acide isophtalique (H2ip) et l'avons caracterise sur les plans structurel et magnetique. La structure du compose 1 est constituee de chaines de coordination unidimensionnelles par rapport aux unites [Co.sub.2] pontees par deux groupements carboxylates, oU les atomes d'azote des groupes pyridyles dans les ligands 4-Hppt sont situes sur les sites de coordination axiale des atomes de Co(II) formant la structure tetrahedrique. Dans le compose faisant l'objet du present article, l'etude magnetique semble indiquer que le couplage magnetique derive des ions Co(II) dinucleaires est un echange moderement antiferromagnetique. Par ailleurs, nous avons effectue des calculs de DFT avec ce compose afin de fournir une explication theorique qualitative du comportement magnetique. [Traduit par la Redaction] Mots-cles: compose de cobalt(II), acide isophtalique, triazole pyridine, unite dimerique metallique, proprietes magnetiques., Introduction Structural design and magnetic properties of coordination polymers (CPs) containing paramagnetic centers ([Co.sup.2+], [Ni.sup.2+], [Cu.sup.2+] etc.) are presently of considerable interest. (1) In particular, the advancements of low-dimensional magnetic [...]

Based on a β-diketonate ligand, a mononuclear Dy(III) complex, [Dy(dmpd) 3 (bpy)] (1) (dmpd = 4,4-dimethyl-1-phenylpentane-1,3-dione, bpy = 2,2'-dipyridyl), of [DyN 2 O 6 ] type has been synthesized with a capping nitrogen-containing coligand. Then, a dual capping coligand 2,2'-bipyrimidine (bmp) is introduced to be a bridge to link two β-diketonate-Dy(III) motifs, leading to a new dinuclear Dy(III) complex, [Dy 2 (dmpd) 6 (bmp)] (2). Dy(III) centers in both complexes feature an N 2 O 6 octacoordinated environment with an approximate square-antiprism geometry ( D 4d ). Without a dc field, the SMM behaviour is absent in complex 1, but can be clearly observed in dinuclear 2 with a U eff of 87.29 K. The significantly improved magnetism arising in 2 is mainly due to the modulation of the coordination environment around the Dy(III) ions and the superexchange magnetic interactions inside the dinuclear units, thus allowing for the effective inhibition of the quantum tunneling of magnetization at low temperatures and promotion of the uniaxial magnetic anisotropy. For 1, a diamagnetic Y(III) analogue [Y(dmpd) 3 (bpy)] (3) and diluted sample 1@Y were constructed to further perform the dilution experiment, coupled with theoretical calculations further supporting that the synergetic contributions of intermolecular dipole-dipole interactions, intramolecular coupling and uniaxial magnetic anisotropy cause the enhancement of dynamic magnetic relaxation.

Precise control of the crystal field and local symmetry around the paramagnetic spin center is crucial for the design and synthesis of single-molecule magnets (SMMs). Herein, three mononuclear Dy(III)-based complexes, [Dy(L N6 )(CH 3 COO) 2 ](BPh 4 )(CH 2 Cl 2 ) (1), [Dy(L N6 )(2,6-Cl-4-NO 2 -PhO)(H 2 O) 2 ] 2 (PF 6 ) 2 (H 2 O)(2,6-Cl-4-NO 2 -PhO) 2 (2) and [Dy(L N6 )(2,6-Cl-4-NO 2 -PhO) 2 ](BPh 4 )(CH 2 Cl 2 ) 2 (3) (L N6 = N6-hexagonal plane accomplished by a neutral Schiff base ligand formed from 2,6-diacetylpyridine and ethylenediamine), are successfully isolated. In these complexes, the Dy(III) centers are coordinated with six neutral N atoms from a nonrigid equatorial ligand, while different oxygen-bearing ligands are arranged at the axial positions of the central ions by gradual regularization of the axial ligands. As a result, Dy(III) ions in the three complexes exhibit various coordination geometries, forming a ten-coordinate tetradecahedron for 1, a nine-coordinate muffin configuration for 2 and a distorted eight-coordinate hexagonal bipyramid for 3. Magnetic studies reveal that all complexes exhibit no SIM behaviour under zero dc field, due to the predominant quantum tunneling of magnetization (QTM), which can be effectively suppressed by additional dc fields. Experiments, coupled with theoretical calculations, demonstrate that varying local symmetries and coordination geometries are synergistically responsible for the disparities of QTM and uniaxial anisotropy, resulting in notably different magnetic properties.

A mononuclear four-coordinate Co(II) complex with a [Co II O 4 ] core, namely, PPN[Li(MeOH) 4 ][Co(L) 2 ] ( 1 ) (PPN = bis(phosphoranediyl)iminium; H 2 L = perfluoropinacol), has been studied by X-ray crystallography, magnetic characterization, and theoretical calculations. This complex presents a severely distorted coordination geometry. The O-Co-O bite angle is 83.42°/83.65°, and the dihedral twist angle between the O-Co-O chelate planes is 55.6°. The structural distortion results in a large easy-axis magnetic anisotropy with D = -104(1) cm -1 and a transverse component with | E | = +4(2) cm -1 . Alternating current (ac) susceptibility measurements demonstrate that 1 exhibits slow relaxation of magnetization at zero static field. However, the frequency-dependent out-of-phase (χ" M ) susceptibilities of 1 at 0 Oe do not show a characteristic maximum. Upon the application of a dc field or the dilution with a diamagnetic Zn matrix, the quantum tunneling of magnetization (QTM) process can be successfully suppressed. Notably, after dilution with the Zn matrix, the obtained sample exhibits a structure different from that of the pristine complex. In this altered sample, the asymmetric unit does not contain the Li(MeOH) 4 + cation, resulting in an O-Co-O bite angle of 86.05° and a dihedral twist angle of 75.84°, thereby leading to an approximate D 2d symmetry. Although such differences are not desirable for magnetic studies, this study still gives some insights. Theoretical calculations reveal that the D parameter is governed by the O-Co-O bite angle, in line with our previous report for other tetrahedral Co(II) complex with a [Co II N 4 ] core. On the other hand, the rhombic component is found to increase as the dihedral angle deviates from 90°. These findings provide valuable guidelines for fine-tuning the magnetic properties of Co(II) complexes.

Two isomeric Co(II) complexes with the same general molecular formula of [Co(napy) 2 (NO 3 ) 2 ] (napy = 1,8-naphthyridine) have been synthesized. X-ray single crystal structural determination demonstrates that the two compounds exhibit highly irregular six- (1) and seven-coordinate (2) geometries, respectively. The magnetic measurements, X-band EPR data and theoretical calculations were thoroughly investigated. Both complexes show field-induced slow magnetic relaxation, of which the slow magnetic relaxation in 2 is attributed to an easy-plane anisotropy.

Metallofullerenes of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 encapsulating mixed-metal nitride clusters were synthesized. Spectroscopic characterization of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 was employed to reveal their structural and vibrational properties. The structural properties of these species were analyzed by using theoretical calculations. The studies of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 laid the foundations for these species to be used as multifunctional molecules., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)