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While the interest in single-molecule magnets (SMMs) lies in their potential applications in information storage and quantum computing, the switching of their slow magnetic relaxation associated with dynamic crystal-to-crystal transformation is insufficiently exploited. Herein, three pentagonal-bipyramidal (PBP) Dy(III) complexes, [Dy(Bcpen)(Cl)3] (1), [Dy(Bcpen)(OPhCl2NO2)3] (2) and [Dy(Bcpen)(OPhCl2NO2)3]·0.5CH3CN (2·CH3CN), are successfully assembled, and structurally and magnetically studied (Bcpen = N,N-bis(4-chloro-2-methylenepyridinyl) ethylenediamine and Cl2NO2PhOH = 2,6-dichloro-4-nitrophenol). The molecular characteristics and magnetic properties of complexes 2 and 2·CH3CN, constructed with the motivation of modulating a magnetic switch by external stimuli, are systematically explored. Dramatically, 2 and 2·CH3CN can mutually transform through reversible single-crystal-to-single-crystal (SCSC) conversion associated with the capture and release of guest CH3CN molecules, resulting in an infrequent on/off switching of PBP Dy(III) molecule-based magnets. Further measurements on the desolvated and resolvated samples, complexes 2-re and 2·CH3CN-re, confirm the fascinating transformation processes. The magneto-structural relationship has been rationally investigated and discussed with ab initio calculations as well. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, crystal structure and detailed magnetic properties of a pyrazine (pyz) and azido (N3) bridged cobalt(II) compound of formula [Co(N3)2(pyz)] (1) are reported. Compound 1 shows a layered structure formed by Co(II) chains with double μ-N3(κN1,N1) bridges that are further connected by μ-(pyrazine-κN1,N4) bridges. The layers present weak van der Waals interactions between azido terminal groups. The magnetic properties show the presence of a metamagnetic behaviour in 1 with two critical fields of 200 and 400 mT at low temperatures. AC magnetic measurements show the presence of a long-range 2D ferromagnetic order at Tc ≈ 8.0–7.0 K for dc fields above 200 mT and a long-range 3D ferromagnetic order at Tc ≈ 4.5 K for dc fields above 400 mT. [ABSTRACT FROM AUTHOR]

A series of five mononuclear β-diketonate-Dy(III) complexes, with formulas Dy(ntfa)3(Br-bpy) (1), Dy(ntfa)3(Br2-bpy) (2), Dy(ntfa)3(5,5-(CH3)2-bpy) (3), Dy(ntfa)3(4,4-((CH3)3)2-bpy) (4) and Dy(ntfa)3(4,4-(CH3)2-bpy) (5) (ntfa = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, Br-bpy = 5-bromo-2,2′-bipyridine, Br2-bpy = 4,4′-dibromo-2,2′-bipyridine, 5,5-(CH3)2-bpy = 5,5′-di-methyl-2,2′-bipyridine, 4,4-((CH3)3)2-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine, and 4,4-(CH3)2-bpy = 4,4′-di-methyl-2,2′-bipyridine), have been prepared by altering the capping N-donor coligands. Dy(III) ions in all complexes possess N2O6 octa-coordinated environments, displaying a distorted square antiprismatic D4d symmetry in complexes 1–4, as well as a triangular dodecahedron D2d symmetry in 5. Magnetic investigations evidence the SIM behavior in the five complexes with the energy barriers (Ueff) of 104.19 K (1), 122.93 K (2), 84.20 K (3), 64.16 K (4) and 80.23 K (5) under zero applied dc field. The potential QTM effects in the title complexes are successfully suppressed in the presence of the extra applied fields. The crystal field parameters and orientations of the magnetic easy axes were obtained from the simulation of the magnetic data and the electrostatic model calculation. The distinct electronic effects originating from the subtle changes of the substituents on the capping N-donor coligands induce varying coordination microenvironments and geometries on the Dy(III) sites, further drastically impacting the overall magnetic properties of the title complexes. The disparities of the uniaxial anisotropy and the magnetic dynamics for 1–5 have been elucidated by ab initio calculations as well. [ABSTRACT FROM AUTHOR]

Two mononuclear azido–cobalt(II) complexes, with the formulas [Co(3,3-Hbpt)2(N3)2(H2O)2] (1) and [Co(abpt)2(N3)2]·H2O (2) (3,3-Hbpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole; abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole), have been prepared by altering the pyridyl-triazole coligands. In both complexes, the Co(II) centers feature hexa-coordinated environments with distorted octahedra in which the axial sites are identical, whereas the equatorial environments are finely modulated by the distinct chemical nature of the different coligands. It is worth noting that the distinct intermetallic distances in the two complexes (10.302 Å for 1 and 6.576 Å for 2) unambiguously cause a disparity in intermolecular interactions, implying their dissimilar magnetic behaviours. As a result, alternating current dynamic susceptibility measurements show that only 2 exhibits field-induced slow relaxation of magnetization with an effective energy barrier of 11.29 K, though large easy-axis magnetic anisotropies for both complexes are unveiled by combined analyses of the magnetic data and ab initio calculations. [ABSTRACT FROM AUTHOR]

By means of the solvent effect, three new azido-copper 1D coordination polymers, [Cu(4-aba)(N3)] (1), [Cu(4-aba)(N3)(CH3OH)] (2), and [Cu(4-aba)(N3)(C2H5OH)] (3) (4-aba = 4-azidobenzoic acid), were successfully prepared in the presence of Cu2+ ion, NaN3 and 4-azidobenzoic acid. Interestingly, 1 can be employed as a precursor and transformed to 2 and 3via the coordination of methanol or ethanol, respectively. Meanwhile, the identical products of 1, namely 1a and 1b, could be obtained from both 2 and 3 by a dealcoholized process. As a result, the geometric configurations of Cu(ii) ions vary from the tetracoordinated square-planar in 1 to the hexacoordinated octahedron in 2 or 3. Compound 1 displays a well-isolated 1D chain with dual-bridges of EO-azido and syn,syn-carboxylate, while isomorphic 2 and 3 are triple-bridged chain-like motifs containing EO-azido, syn,syn-carboxylate and μ2-alkanol. The structural transformations caused by the intervention of alkanol molecules modulate the intrachain Cu–Cu distances (3.570 for 1, 3.204 Å for 2 and 3.154 Å for 3) and Cu–N–Cu angles (127.3° for 1, 106.82° for 2 and 104.81° for 3). This modulation, however, further leads to different intrachain ferromagnetic interactions (J = 28.4 cm−1 for 1, 67.6 cm−1 for 2, 40.2 cm−1 for 3) that are qualitatively demonstrated by theoretical calculation. More importantly, the significant scenarios of magnetic ordering and slow magnetic relaxation, which are infrequent in most of the reported azido-copper cases, are only observed in 2 and 3, due to the distinct interchain networks among 1–3. In addition, heat-capacity measurements highlight the characteristics of long-range ferromagnetic ordering in 2 and 3. [ABSTRACT FROM AUTHOR]

A family of four mononuclear DyIII β‐diketonate complexes with formulas [Dy(tmhd)3(Br2‐bpy) (1), [Dy(tmhd)3(Br‐bpy)] (2), [Dy(tmhd)3(dppz)] (3), and [Dy(tmhd)3(mcdpq)] (4) (tmhd=2,2,6,6‐tetramethyl‐3,5‐heptanedione, Br2‐bpy=5,5′‐dibromo‐2,2′‐bipyridine, Br‐bpy=5‐bromo‐2,2′‐bipyridine, dppz=dipyrido [3,2‐a:2′,3′‐c]phenazine, mcdpq=2‐methoxyl‐3‐cyanodipyrido[3,2‐f:2,3′‐h]quinoxaline) were prepared by modifying the capping N‐donor coligands. DyIII centers in these complexes feature an N2O6 octacoordinate environment with distorted square‐antiprismatic D4d symmetry. Magnetic investigations evidenced single‐ion magnet behavior in all complexes with energy barriers Ueff of 42.10 (1), 61.47, (2), 77.53 (3), and 2.51 K (4) in the absence of static field, as well as 206.03 (1), 224.13 (2), 247.76 (3), and 49.70 K (4) under applied dc field (Hdc=1500 Oe for 1 and 2; Hdc=1200 Oe for 3 and 4). The different natures of the N‐donor ligands induce changes in both the coordination geometry and their intermolecular interactions, which severely impact their magnetic dynamics. The disparities in their magnetic behaviors and the uniaxial anisotropies are also explained and substantiated by theoretical calculations. Cap variations: A combination of electron‐donating β‐diketonate ligands and different capping N‐donor coligands led to a family of four mononuclear DyIII complexes exhibiting nearly identical D4d symmetry but differing magnetic dynamics, which were elucidated by a combination of magnetic investigations and ab initio calculations. [ABSTRACT FROM AUTHOR]

Based on different alkanol solvents, a family of azido–copper coordination polymers has been successfully synthesized. The as-synthesized compounds share the formula [Cu(4-tfmba)(N3)(solvent)]n, where 4-tfmba = 4-trifluoromethyl benzoic acid and solvent = CH3OH (1), C2H5OH (2) and C3H7OH (3). Single-crystal structure analysis indicates that the Cu(ii) centers in 1–3 are interconnected by an alternant triple-bridge of μ-1,1-azido, syn,syn-carboxy and μ2-alkanols, yielding homoplastically well-isolated 1D metal-chain patterns with tiny disparities in the geometric parameters. Noteworthily, the homologous alkanol solvents with growing carbon chain are not only the reaction solvents but are also employed to be the linkers to embed the structural frameworks of the resulting polymers, regulating in an orderly way the interchain structures and thus fine-tuning the magnetic behaviors of the resulting compounds. As a result, the predominant intrachain ferromagnetic exchanges caused by counter-complementarity of the threefold super-exchange channels are revealed in all three cases, finally giving rise to the ascending magnitudes of magnetic coupling effect (J = 56.21 cm−1 for 1, J = 68.94 cm−1 for 2 and J = 77.94 cm−1 for 3) and the well-organized scenarios of magnetic order and slow relaxation that are infrequent in known azido–Cu(ii) coordination networks. Among 1–3, the exchange of CH3OH for C2H5OH or C3H7OH, all of which coordinate through a single O atom, induces an interesting dynamic magnetic transition from a vitreous state to quasi-superparamagnet. Moreover, DFT calculations have been carried out to provide a qualitative and quantitative theoretic explanation of the magnetic behaviors of 1–3. [ABSTRACT FROM AUTHOR]

Based on two fluoro-substituted phenylacetate isomers, o-fluorophenylacetic acid (o-Hfpa) and p-fluorophenylacetic acid (p-Hfpa), two new Cu(ii)-azido compounds, [Cu(o-fpa)(N3)(C2H5OH)]n (1) and [Cu(p-fpa)(N3)(C2H5OH)]n (2), have been prepared, and structurally and magnetically characterized. Single-crystal structure analyses indicate that compounds 1 and 2 consist of 1D chain-like coordination networks in which adjacent copper cations are linked by the alternating triple-bridges of μ-1,1-azido, syn,syn-carboxylate and μ2-ethanol. For the two title compounds, the diverse charge distributions on the carboxyl groups caused by distinct substituent effects of the two phenylacetate coligands lead to the different structural parameters of intrachain Cu–Cu distances (3.218 Å for 1 and 3.168 Å for 2) and Cu–N–Cu angles (106.82° for 1 and 104.81° for 2), further resulting in the disparity of magnetic behaviors. The dominant ferromagnetic couplings between neighbouring Cu(ii) ions in the two compounds (J = 87.08 cm−1 for 1, J = 66.05 cm−1 for 2) are due to the counter-complementarity of the multiple superexchange pathways, contributing to the interesting plots of a ferromagnetic order (Tc = 11.0 K for 1, 9.5 K for 2) and slow magnetic relaxation that are rarely observed in most of the reported azido-Cu(ii) architectures. Heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in compounds 1 and 2. Magneto-structural relationships of 1 and 2 are investigated as well. Moreover, DFT calculations (using different methods and basis sets) have been performed on both compounds to provide a qualitative and quantitative theoretical explanation of their magnetic behavior. [ABSTRACT FROM AUTHOR]

Employing two benzoate derivatives with different numbers of non-coordinated fluoro-substituents, 2-fluorobenzoic acid (2-Hfba) and 2,6-difluorobenzoic acid (2,6-Hdfba), two new azido-copper coordination polymers, [Cu(2-fba)(N3)(CH3OH)]n (1) and [Cu(2,6-dfba)(N3)(CH3OH)]n (2), have been successfully isolated, and then structurally and magnetically investigated. Single crystal structure analysis demonstrates that the metal cations in the two resulting compounds are connected by the alternating triple-bridge of μ-1,1-azido, syn,syn-carboxylate and μ2-methanol, contributing to analogously linear 1D Cu(ii) chain-like motifs with slightly different intrachain and interchain geometric parameters. The fine-tuned structures lead to variant magnetic properties in the two title compounds. Although a dominant ferromagnetic coupling between adjacent Cu(ii) ions within each chain due to the counter-complementarity of the multiple superexchange pathways is observed in both compounds, the interesting plots of magnetic ordering and slow magnetic relaxation, which are rare in most of the reported azido-Cu(ii) architectures, only occur in compound 1, while 2 behaves as an antiferromagnet consisting of ferromagnetic Cu(ii) chains. The heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in 1 and the typical behavior of antiferromagnets in 2. Moreover, density functional theory (DFT) calculations (using different methods and basis sets) have been performed on both compounds to obtain the qualitatively theoretical interpretation of the magnetic behaviors. [ABSTRACT FROM AUTHOR]

Employing different benzendicarboxylic acids as co-ligands, two new compounds, [Cu 2 (bpad) 2 (Hp) 2 ] n ( 1 ) and [Cu 2 (bpad) 2 (Hip) 2 ] n ( 2 ) (Hbpad = N 3 -benzoylpyridine-2-carboxamidrazone, H 2 p = phthalic acid, H 2 ip = isophthalic acid), have been synthesized. The structures and magnetic properties of title compounds have been systematically characterized. The two dinuclear Cu(II) compounds are isomers in which the metal ions adopt distinguishably penta-coordinated geometries. Cu(II) ions with square pyramidal structure are bridged by carboxylate oxygen atoms in 1 , while the Cu(II) centers with trigonal bipyramid model are linked by carbamoyl oxygen atoms in 2 . Magnetic measurements illustrate that the short contacts causing antiferromagnetic intra-dimer interactions consist in compound 1 , whereas ferromagnetic intra-dimer interactions are performed on compound 2 . [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)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 Co2 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. [ABSTRACT FROM AUTHOR]

Based on the InOm notion (In = the dimensionality of the inorganic connectivity; Om = the dimensionality of the organic connectivity; n + m≤ 3), we obtained ten transition/alkaline earth mixed-metal–organic frameworks (M′MOFs) from 1D to 3D through a “metalloligand” strategy at room temperature. Single-crystal X-ray diffraction analyses indicate that the resulting compounds possess the square plane [MII(pzdc)2]2− (M = Co, Ni or Cu) “organic” connectivity and the Ae–O–Ae (Ae = Ca, Sr or Ba) inorganic connectivity, which can be classified as I1O0 connectivity for complexes 1, 4, 7 and 9, I1O1 connectivity for complexes 2, 3, 5, 6 and 8 and I1O2 connectivity for complex 10. The [MII(pzdc)2]2− moieties acting as bis(tetradentate) polycarboxylate ligands show three types of coordination modes, namely μ4-(η2-O,O)2,(η1-O′)2, μ6-(η2-O,O)2,(η1-O′)2,(η1-O′)2 and μ10-(η2-O,O)2,(η2-O′,O′)2, (η1-O′)2,(η1-O′)2,(η1-N′)2. Additionally, the thermal stabilities of complexes 1–10 and magnetic properties of complexes 1, 2, 4, 5 and 10 have also been investigated. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, crystal structure and detailed magnetic properties of a pyrazine (pyz) and azido (N3) bridged cobalt(II) compound of formula [Co(N3)2(pyz)] (1) are reported. Compound 1 shows a layered structure formed by Co(II) chains with double μ-N3(κN1,N1) bridges that are further connected by μ-(pyrazine-κN1,N4) bridges. The layers present weak van der Waals interactions between azido terminal groups. The magnetic properties show the presence of a metamagnetic behaviour in 1 with two critical fields of 200 and 400 mT at low temperatures. AC magnetic measurements show the presence of a long-range 2D ferromagnetic order at Tc ≈ 8.0–7.0 K for dc fields above 200 mT and a long-range 3D ferromagnetic order at Tc ≈ 4.5 K for dc fields above 400 mT. [ABSTRACT FROM AUTHOR]

With the increased electron donating effect on carboxylic acid substituents, the ferromagnetic interaction between the paramagnetic centres was enhanced, whereas the contribution of the antiferromagnetic interaction was reduced. • The calculations at the B3LYP/def2-TZVP level could describe the magnetic properties of the azide copper complex accurately. • Magnetic orbits were mainly composed of orbits 3 d z2 of Cu(1)/Cu(2) and the -type molecular orbital. • With the increased electron donating effect on carboxylic acid substituents, the ferromagnetic interaction between the paramagnetic centres was enhanced, whereas the contribution of the antiferromagnetic interaction was reduced. The magnetic properties of the azide copper complex [Cu 2 (dpyam) 2 (μ 1,1 -N 3) 2 (O 2 CCH 3) 2 were studied using the density functional theory-broken symmetry methodology under different functional methods and basis sets. The magnetic coupling constant between paramagnetic centres was calculated as 36.75 cm−1, which agreed with the experimental value of 31.9 cm−1. Accordingly, the calculations at the B3LYP/def2-TZVP level could describe the magnetic properties of the azide copper complex accurately. To study thoroughly the effect of carboxylic acid auxiliary ligands in azido-Cu(II) systems, acetas were deleted from the auxiliary ligands(1) and replaced by H 2 O-(2), HCOO-(3), CH 3 COO-(4), C 2 H 5 COO-(5), and C 6 H 5 COO-(6), yielding six research models. With the increased electron donating effect on carboxylic acid substituents, the ferromagnetic interaction between the paramagnetic centres was enhanced, whereas the contribution of the antiferromagnetic interaction was reduced. The parameters ρ HS 2 - ρ BS 2 , S ab 2 , and (ε 1 - ε 2) 2 can be extended to other binuclear complexes for the study of magneto-structural correlation. [ABSTRACT FROM AUTHOR]