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A series of bis-pentamethylcyclopentadienyl-supported Dy complexes containing different ancillary ligands were synthesized and characterized. Magnetic studies showed that 1 Dy [Cp*2DyCl(THF)], 1 Dy' [Cp*2DyCl2K(THF)] n, 2 Dy [Cp*2DyBr(THF)], 3 Dy [Cp*2DyI(THF)] and 4 Dy [Cp*2DyTp] (Tp=hydrotris(1-pyrazolyl)borate) were single-ion magnets (SIMs). The 1D dysprosium chain 1 Dy' exhibited a hysteresis at up to 5 K. Furthermore, 3 Dy featured the highest energy barrier (419 cm−1) among the complexes. The effects of ancillary ligands on single-ion magnetic properties were studied by experimental, ab initio calculations and electrostatic analysis methods in detail. These results demonstrated that the QTM rate was strongly dependent on the ancillary ligands and that a weak equatorial ligand field could be beneficial for constructing Dy-SIMs. [ABSTRACT FROM AUTHOR]

The modular construction method provides a feasible way to construct pre-designed cyano-bridged {LnIIIMIV/V} systems with more attractive structures and adjustable interactions between 4d/5d and 4f ions. In this work, the pentadentate Schiff-base ligands H2Ln (H2L1: 2,6-diacetylpyridine bis(nicotinoylhydrazone); H2L2: 2,6-diacetylpyridine bis(isonicotinoylhydrazone)) with multiple coordination sites were designed to coordinate with DyIII ions firstly, and then combined with K4M(CN)8·2H2O (M = W, Mo) by a liquid–liquid diffusion method to successfully synthesize two trinuclear structures {Dy[MIV(CN)8]0.5(HL1)(H2O)3}2·8H2O (1: M = W; 2: M = Mo), and two dinuclear structures {[Dy[MIV(CN)8](H3L2)(H2O)3]}·sol (3: M = W, sol = 11.5H2O; 4: M = Mo, sol = 2CH3OH·9.5H2O). Interestingly, deprotonation occurs in ligand H2L1 during the formation of complexes 1 and 2, while deprotonation/protonation processes both occur in ligand H2L2 during the synthesis of complexes 3 and 4. Magnetic analyses reveal that complexes 1–4 are all field-induced single-ion magnets (SIMs). The energy barriers (Ueff/kB) of complexes 1 and 2 are 92.83 K and 101.08 K, respectively, which are nearly three-fold higher than those of complexes 3 (30.19 K) and 4 (32.77 K). Ab initio calculations were performed on these series of {LnIIIMIV} heteronuclear complexes to provide more insights into the magnetic relaxation properties. This work provides another example of improving the SMM behaviors of cyano-bridged {LnIIIMIV} systems by deprotonation/protonation at different sites in the ligands. [ABSTRACT FROM AUTHOR]

Complexation of dysprosium(III) ions with a multidentate hydrazone ligand, N-[(E)-pyridin-2-ylmethylideneamino]pyridine-2-carboxamide (L), in the presence of different β-diketonate coligands, leads to the formation of two novel DyIII dimers, with formulas Dy2(BTFA)4(L)2 (1) and Dy2(TTA)4(L)2 (2) (BTFA = 3-benzoyl-1,1,1-trifluoroacetone and TTA = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate). They exhibit slightly different coordination geometries around DyIII centers and discrepant binuclear motifs – as a result of altering the β-diketonate coligands – which has an impact on the magnetic interactions between metal centers, the local tensor of anisotropy on each DyIII site and their relative orientations, therefore contributing to distinct magnetization dynamics. Compared to 2, complex 1 exhibits a more significant slow magnetic relaxation of SMM behavior in the absence of a dc field. The QTM effect is effectively repressed under a static field, resulting in the energy barriers of 57 K for 1 and 38 K for 2. Ab initio calculations clarify that, strong single-ion magnetic anisotropies exist in both complexes, whereas intermetallic ferromagnetic interaction and antiferromagnetic interaction are observed in 1 and 2, respectively, therefore resulting in dissimilar magnetization dynamics. [ABSTRACT FROM AUTHOR]

The utilization of two isomorphic ligands with different substituents leads to two centrosymmetric DyIII dimers, namely, [Dy2(bfbpen)2(H2O)2]·2I− (1) and [Dy2(bcbpen)2(H2O)2]·2I−·0.5H2O (2) (H2bfbpen = N,N′-bis-(2-hydroxy-5-fluoro-benzyl)-N,N′-bis-(pyridin-2-ylmethyl)ethylenediamine and H2bcbpen = N,N′-bis-(2-hydroxy-5-chloro-benzyl)-N,N′-bis-(pyridin-2-ylmethyl)ethylenediamine). Although Dy ions in both compounds uniformly exhibit a square-antiprism geometry, the critical difference found in the terminal substituents of the two ligands fine-tunes the local crystal field around Dy centers and the dinuclear molecular structures of 1 and 2. Magnetic investigations unveil that both 1 and 2 display dynamic magnetic relaxation of single-molecule magnet (SMM) behaviour with different energy barriers of 20.9 K for 1 and 72.7 K for 2 under a zero direct-current (dc) field, as well as 26.9 K for 1 under a 1200 Oe dc field. Compared to 1, the stronger uniaxial anisotropy and magnetic exchange in 2 render it a better SMM as evidenced by the higher energy barrier. Ab initio calculations are also performed on both Dy2 compounds to rationalize the observed discrepancy in their magnetic behaviours. The contribution illustrates that the SMM behaviour could be effectively enhanced by means of deliberate local structural manipulation. [ABSTRACT FROM AUTHOR]

Synthesis of air-stable and high-performance single-molecule magnets (SMMs) is challenging. Here, a heptadentate pentapyridyldiamine (BPA-TPA) ligand and fine-tuned axial phenoxy ligands are used to synthesize two triangular dodecahedral Dy(III) complexes [Dy(BPA-TPA)(4-methoxy-PhO)](BPh4)2·3CH2Cl2 (4) and [Dy(BPA-TPA)(2,4-dimethyl-PhO)](BPh4)2·0.85CH2Cl2 (5). Both complexes have high effective barriers exceeding 400 K and magnetic hysteresis up to 8 K, which is ascribed to one strong and short Dy–O bond combined with seven weak Dy–N bonds. Ab initio calculations reveal the thermally activated quantum tunneling of magnetization through the first excited Kramers doublet, due to the presence of a strong axial Dy–O crystal ligand. Substitution of the phenoxy ligand leads to more constrained vibrations, improving the magnetic hysteresis behavior for 5. [ABSTRACT FROM AUTHOR]

A series of bis‐pentamethylcyclopentadienyl‐supported dysprosium complexes containing different ancillary ligands was studied. The results showed that a weak equatorial ligand field was beneficial for constructing dysprosium single‐ion magnets. More information can be found in the Full Paper by Y. Q. Zhang, B. W. Wang, S. Gao et al. on page 12724. [ABSTRACT FROM AUTHOR]

Two dysprosium complexes bearing unsupported Dy–Ge/Sn metal–metal bonds are reported here, wherein the Dy–Ge and Dy–Sn bonds both contain relatively large covalency. The complexes exhibit slow relaxation of magnetization at zero field with energy barriers of 485 and 620 K, respectively, and the blocking temperature of 6 K. [ABSTRACT FROM AUTHOR]

In a field-induced single-ion magnet [(dtc)3Dy(phen)] (dtc− = diethyldithiocarbamate anion), replacing two of the S-based dtc− ligands with O-based dbm− ligands (dbm− = dibenzoylmethanoate anion) leads to a significant enhancement of magnetic anisotropy, yielding a rarely reported sulfur-ligated lanthanide-based single-ion magnet [(dbm)2Dy(dtc)(phen)]. Ab initio calculations reveal that the gz value of [(dbm)2Dy(dtc)(phen)] is much larger than that of [(dtc)3Dy(phen)], consistent with the experimental results. [ABSTRACT FROM AUTHOR]

In recent years, plentiful lanthanide-based (TbIII, DyIII, and ErIII) single-molecule magnets (SMMs) were studied, while examples of other lanthanides, for example, TmIII are still unknown. Herein, for the first time, we show that by rationally manipulating the coordination sphere, two thulium compounds, 1[(Tp)Tm(COT)] and 2[(Tp*)Tm(COT)] (Tp=hydrotris(1-pyrazolyl)borate; COT=cyclooctatetraenide; Tp*=hydrotris(3,5-dimethyl-1-pyrazolyl)borate), can adopt the structure of non-Kramers SMMs and exhibit their behaviors. Dynamic magnetic studies indicated that both compounds showed slow magnetic relaxation under dc field and a relatively high effective energy barrier (111 K for 1, 46 K for 2). Magnetic diluted 1 a[(Tp)Tm0.05Y0.95(COT)] and 2 a[(Tp*)Tm0.05Y0.95(COT)] even exhibited magnetic relaxation under zero dc field. Relativistic ab initio calculations combined with single-crystal angular-resolved magnetometry measurements revealed the strong easy axis anisotropy and nearly degenerated ground doublet states. The comparison of 1 and 2 highlights the importance of local symmetry for obtaining Tm SMMs. [ABSTRACT FROM AUTHOR]

Terminal fluoride ligands generate strong magnetic anisotropy in air-stable chiral dysprosium enantiomers supported by a bulky equatorial macrocycle, exhibiting a typical zero-field single-molecule magnet behaviour. [ABSTRACT FROM AUTHOR]

Three mononuclear Co(II) complexes with the compositions of [Co(L1)2] (1), [Co(L2)2(CH3CN)] (2) and [Co(L3)2] (3) (HL1 = 2-((E)-(2-fluorobenzylimino)methyl)-4,6-dibromophenol, HL2 = 2-((E)-(3-fluorobenzylimino)methyl)-4,6-dibromophenol and HL3 = 2-((E)-(4-fluorobenzylimino)methyl)-4,6-dibromophenol) were prepared and structurally determined. The changes in the F-positions in the ligands and solvents led to the formation of these products with various coordination geometries. Both complexes 1 and 3 are four-coordinated and their coordination geometries can be described as tetrahedron and seesaw, whereas complex 2 is five coordinated with a coordination configuration in between trigonal bipyramid and square pyramid. Static magnetic studies reveal that all these complexes exhibit considerable easy-axis magnetic anisotropy. The easy-axis magnetic anisotropy of 1 and 3 mainly derives from the first quartet excited state, whereas that of 2 primarily originates from the first, third and fourth quartet excited states established by theoretical calculations. All the resulting complexes display field-induced slow magnetic relaxation. Complex 3 represents the first Co(II) single ion magnet with a seesaw coordination geometry. Ab initio calculations predict that the magnetic anisotropy will enhance when the seesaw coordination geometry varies from distortion to regulation. [ABSTRACT FROM AUTHOR]

Five β-diketone based Dy(III) single-ion magnets (SIMs), [DyIII(TTA)3(AIP)]·0.5CH3CH2OH·0.5H2O (1), [DyIII(TTA)3(APIP)]·2CH3OH·H2O (2), [DyIII(TTA)3(DPP)] (3), [DyIII(TTA)3(BPP)]·0.5CH3CH2OH (4) and [DyIII(TTA)3(AIP)]·1.5H2O (5), were fully synthesized through alteration of their phenanthroline derivates (AIP = 2-(anthracen-9-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, APIP = 2-(4-(anthracen-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, DPP = 2,3-diphenylpyrazino[2,3-f][1,10]phenanthroline and BPP = 2,3-bis(2,5-dimethylthiophen-3-yl)pyrazino[2,3-f][1,10]phenanthroline). Magnetic investigations reveal that all the complexes perform as SIMs, with notably different effective barriers of 69.4 K (1), 147.3 K (2), 122.1 K (3) and 234.2 K (4) in zero direct current (dc) field. Complexes of 2 and 4 possess almost twofold higher effective barriers compared to 1 and 3. By analyzing the crystal structures, the distinct magnetic dynamics was found to stem from the variation in intermolecular hydrogen bond interactions and charge delocalization of auxiliary ligands. With the help of ab initio calculations, a change of auxiliary ligand brings about varying intensities of quantum tunnelling magnetization (QTM), which account for the distinguishable magnetic dynamics. With a combination of experimental and theoretical analyses, this work provides a visual and instructive perspective to the understanding of fine tuning auxiliary ligands to design structurally modulated SIMs of mononuclear β-diketone dysprosium(III) complexes. [ABSTRACT FROM AUTHOR]

A β-diketonate mononuclear dysprosium compound, [Dy(DBM)2(bpy)(CH3OH)2]·Cl− (1) (DBM = dibenzoylmethane, bpy = 2,2′-bipyridine), has been prepared and structurally and magnetically characterized. The metal centers in 1 adopt an approximately square-antiprismatic (SAP) coordination environment with D4d axial symmetry. Magnetic investigations unveil that 1 displays slow magnetic relaxation of SMM behavior with an effective barrier (Ueff) of 25.13 K under a zero dc field as well as 68.30 K in the presence of a 1200 Oe dc field. The comparative studies of some known Dy(III)-based SIMs with DBM ligands show that the energy barriers can be significantly tuned by adjusting the distortion of the SAP configuration on DyIII ions. Ab initio calculations demonstrate that relaxation of the magnetization for 1 mainly takes place via the first excited-state Kramers doublet through Orbach, Raman, and thermally assisted quantum-tunnelling mechanisms. [ABSTRACT FROM AUTHOR]

The reaction of Dy(NO3)3·6H2O and an asymmetric Schiff-base linker 5-chloro-2-(((2-hydroxy-3-methoxybenzyl)imino)methyl) phenol (H2L) afforded a dinuclear compound [Dy2L2(HL)(NO3)(EtOH)]·0.5C2H5OH (1). Complex 1 features two inequivalent Dy(III) sites, where three ligand sets (one HL− moiety and two L2− groups) are shared by two Dy(III) ions. The strategic introduction of CH3COOH in the reaction system used for synthesizing 1 induces the replacement of the HL− ligand by the CH3COO− ion, consequently resulting in the generation of [Et3NH][Dy2L2(NO3)(CH3COO)2] (2). In complex 2, two Dy(III) centers adopt NO7 (D2d geometry) and NO6 (C2v) coordination sphere, respectively. DC magnetic susceptibility studies for the two complexes indicate ferromagnetic interactions. Complexes 1 and 2 exhibit single-molecule magnet behavior with two-step slow relaxation processes due to the possession of inequivalent metal sites. The energy barriers of 69.19 and 45.73 K for 1, and 92.77 and 72.95 K for 2 are determined. Theoretical calculations reveal that the two-step relaxation processes in both 1 and 2 mainly originate from the single-ion magnetism of two distinct Dy(III) ions with inequivalent coordination environments. [ABSTRACT FROM AUTHOR]

Lanthanide permanent magnets are widely used in applications ranging from nanotechnology to industrial engineering. However, limited access to the rare earths and rising costs associated with their extraction are spurring interest in the development of lanthanide‐free hard magnets. Zero‐ and one‐dimensional magnetic materials are intriguing alternatives due to their low densities, structural and chemical versatility, and the typically mild, bottom‐up nature of their synthesis. Here, we present two one‐dimensional cobalt(II) systems Co(hfac)2(R‐NapNIT) (R‐NapNIT=2‐(2′‐(R‐)naphthyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide, R=MeO or EtO) supported by air‐stable nitronyl nitroxide radicals. These compounds are single‐chain magnets and exhibit wide, square magnetic hysteresis below 14 K, with giant coercive fields up to 65 or 102 kOe measured using static or pulsed high magnetic fields, respectively. Magnetic, spectroscopic, and computational studies suggest that the record coercivities derive not from three‐dimensional ordering but from the interaction of adjacent chains that compose alternating magnetic sublattices generated by crystallographic symmetry. [ABSTRACT FROM AUTHOR]

Lanthanide permanent magnets are widely used in applications ranging from nanotechnology to industrial engineering. However, limited access to the rare earths and rising costs associated with their extraction are spurring interest in the development of lanthanide‐free hard magnets. Zero‐ and one‐dimensional magnetic materials are intriguing alternatives due to their low densities, structural and chemical versatility, and the typically mild, bottom‐up nature of their synthesis. Here, we present two one‐dimensional cobalt(II) systems Co(hfac)2(R‐NapNIT) (R‐NapNIT=2‐(2′‐(R‐)naphthyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide, R=MeO or EtO) supported by air‐stable nitronyl nitroxide radicals. These compounds are single‐chain magnets and exhibit wide, square magnetic hysteresis below 14 K, with giant coercive fields up to 65 or 102 kOe measured using static or pulsed high magnetic fields, respectively. Magnetic, spectroscopic, and computational studies suggest that the record coercivities derive not from three‐dimensional ordering but from the interaction of adjacent chains that compose alternating magnetic sublattices generated by crystallographic symmetry. [ABSTRACT FROM AUTHOR]

Based on a multidentate Schiff-base ligand, N,N′-bis(2-hydroxy-5-methyl-3-formylbenzyl)-N,N′-bis-(pyridin-2-ylmethyl)ethylenediamine (H2L), two binuclear DyIII compounds, with formulas [Dy2(L)(NO3)3(CH3O)] (1) and [Dy2(L)(NO3)3(CH3CH2O)] (2), have been synthesized under different solvent systems. The DyIII ions in 1 and 2 adopt monocapped square antiprism coordination geometries, while different structural distortions can be observed. The two DyIII ions in 1 and 2 are bridged by two phenoxide atoms of one L2− ligand and one bridged CH3O−/CH3CH2O− oxygen node, leading to an approximate fusiform Dy2O3 core. The different DyIII–Obridged node distances, DyIII–Obridged node–DyIII angles and DyIII⋯DyIII distances can be observed. Magnetic studies reveal that 1 and 2 display slow magnetic relaxation behaviours under a zero direct-current field with the effective energy barriers (Ueff) of 114.17 K and 171.23 K, respectively. Furthermore, compound 2 possesses the highest Ueff in nine-coordinated Dy2 compounds. The M versus H data exhibit weak butterfly-shaped hysteresis loops at 2 K for 2. The rare CH3O−/CH3CH2O−-bridged nine-coordinated binuclear DyIII single-molecule magnets (SMMs) significantly regulate and enhance the Ueff of compounds 1 and 2. To deeply understand their different magnetic behaviours, the magnetic anisotropies and magnetic interactions of 1 and 2 were studied by ab initio calculations. These findings demonstrate an efficient approach for regulating and enhancing the magnetic anisotropy barriers using a bridged CH3O− anion or CH3CH2O− anion. [ABSTRACT FROM AUTHOR]

Two mononuclear, seven-coordinate Co(II) and Fe(II) complexes [CoII(BPA-TPA)](BF4)2 (1-Co) and [FeII(BPA-TPA)](ClO4)2 (2-Fe) with a capped trigonal prismatic coordination geometry have been synthesized from the pentapyridyldiamine (BPA-TPA) ligand. 1-Co exhibits easy plane anisotropy in which slow magnetic relaxation is observed under a 1.0 kOe dc field. It is the first example of a single-ion magnet (SIM) of a 3d transition metal ion with a capped trigonal prismatic configuration. 2-Fe is not a SIM at 1.8 K. [ABSTRACT FROM AUTHOR]

The effect of screening the CoII moment of monomeric [CoIIL2(H2O)] (L = 8-hydroxyquinaldine), having a trigonal bipyramid coordination, by diamagnetic Zn in Co x Zn 1−x solid solutions on its magnetic relaxation was explored using ac-susceptibility, high-field electron–spin-resonance measurements and CASPT2 calculations. The retention of the crystal structure for all the solid solutions was demonstrated using single crystal diffraction. The dc-magnetization and theoretical fittings of the susceptibility for Co1 and Co0.1Zn0.9 gave a large zero-field-splitting (ZFS) D of 50 ± 6 cm−1, and very weak dipole interaction between the nearest neighbors, while EPR and calculations confirmed the positive sign of the axial component (D). Consistent parameters were obtained from experiments and theory. Importantly, only field-induced relaxation was observed for the samples with less than 50% Co and a gradual change in the barrier energy to moment reversal and relaxation times was observed between 11% and 20% Co, while both were enhanced for higher dilutions. The results establish a clear barrier for extending the longevity of the magnetism for this type of single-ion species by lowering the intramolecular interactions. The results suggest that the magnetic interaction persists up to the second sphere, that is, for a dilution of 1 in 9 (11% Co). Importantly, this method is applicable to all single-ion magnet systems, that is, the optimum dilution concentration to restrain the dipole field can be given only by the single crystal structure. [ABSTRACT FROM AUTHOR]

Three phenoxyl-bridged dinuclear lanthanide complexes [Ln2(dbm)2(LH2)2]·H2O (Ln = Gd for 1, Tb for 2, and Dy for 3, LH3 = (1E,3E)-2-hydroxy-5-methylisophthalaldehyde dioxime, Hdbm = dibenzoylmethane) were synthesized, and structurally and magnetically characterized. In these complexes, LnIII ions are eight coordinated and lie in D4d local symmetry. Intramolecular ferromagnetic couplings are exhibited between LnIII ions. Surprisingly, the intramolecular DyIII–DyIII magnetic couplings are up to 15.00 cm−1, which are the strongest ones of the reported Dy2 complexes by phenoxyl bridges. Complex 3 shows single-molecule magnet behavior with an effective energy of 76.18 K under zero dc field which is in accordance with the calculated value. The magnetostructural correlation of phenoxyl-bridged Dy2 complexes is analyzed. [ABSTRACT FROM AUTHOR]

For a long time, the cobalt(II) complex ([Co(napy)4](ClO4)2) (napy=1, 8‐naphthyridine) has been considered as an eight‐coordinate complex without any structural proof. After careful considerations, two complexes [Co(napy)2Cl2] (1) and [Co(napy)4](ClO4)2 (2) based on the bidentate ligand napy were synthesized and structurally characterized. X‐ray single‐crystal structural determination showed that the cobalt(II) center in [Co(napy)2Cl2] (1) is four‐coordinate with a tetrahedral geometry (Td), while [Co(napy)4](ClO4)2 (2) is seven‐coordinate rather than eight‐coordinate with a capped trigonal prism geometry (C2v). Direct‐current (dc) magnetic data revealed that complexes 1 and 2 possess positive zero‐field splitting (ZFS) parameters of 11.08 and 25.30 cm−1, respectively, with easy‐plane magnetic anisotropy. Alternating current(ac) susceptibility measurements revealed that both complexes showed slow magnetic relaxation behaviour. Theoretical calculations demonstrated that the presence of easy‐plane magnetic anisotropy (D>0) for complexes 1 and 2 is in agreement with the experimental data. Furthermore, these results pave the way to obtain four‐coordinate and seven‐coordinate cobalt(II) single‐ion magnets (SIMs) by using a bidentate ligand. [ABSTRACT FROM AUTHOR]

By using paramagnetic [Fe(CN)6]3− anions in place of diamagnetic [Co(CN)6]3− anions, two field‐induced mononuclear single‐molecular magnets, [Nd(18‐crown‐6)(H2O)4][Co(CN)6]⋅2 H2O (1) and [Nd(18‐crown‐6)(H2O)4][Fe(CN)6]⋅2 H2O (2), have been synthesized and characterized. Single‐crystal X‐ray diffraction analysis revealed that compounds 1 and 2 were ionic complexes. The NdIII ions were located inside the cavities of the 18‐crown‐6 ligands and were each bound by four water molecules on either side of the crown ether. Magnetic investigations showed that these compounds were both field‐induced single‐molecular magnets. By comparing the slow relaxation behaviors of compounds 1 and 2, we found significant differences between the direct and Raman processes for these two complexes, with a stronger direct process in compound 2 at low temperatures. Complete active space self‐consistent field (CASSCF) calculations were also performed on two [Nd(18‐crown‐6)(H2O)4]3+ fragments of compounds 1 and 2. Ab initio calculations showed that the magnetic anisotropies of the NdIII centers in complexes 1 and 2 were similar to each other, which indicated that the difference in relaxation behavior was not owing to the magnetic anisotropy of NdIII. Our analysis showed that the magnetic interaction between the NdIII ion and the low‐spin FeIII ion in complex 2 played an important role in enhancing the direct process and suppressing the Raman process of the single‐molecular magnet. [ABSTRACT FROM AUTHOR]

Three two-dimensional CoII complexes, namely, [Co(dps)2Cl2]n (1), [Co(dps)2Br2]n (2), and [Co(dps)2(H2O)2·I2·(H2O)4]n (3) (where dps = 4,4′-dipyridyl sulfide), have been synthesized using a rationally designed synthetic approach and characterized structurally and magnetically. Although they crystallize in different space groups, these compounds all have similar two-dimensional (4,4) layer structures where the Co2+ centers are bridged by the bis(monodentate) ligand dps. In addition, the coordination geometry of the Co2+ centers is of a general CoN4X2 octahedral environment formed by four equatorial N atoms from four dps ligands and two X atoms (X = Cl, Br, and O atoms for 1–3, respectively) in the axial positions. Ab initio calculations revealed that due to the strong spin–orbit coupling, the spin Hamiltonian containing the zero-field splitting parameters D and E cannot be used to describe their magnetic anisotropy. According to the calculation, the gz values for the spin–orbit ground doublets of 1–3 are larger than the gx and gy values, which indicates the easy-axis magnetic anisotropy of these compounds. Due to the existence of the magnetic anisotropy, field-induced single-ion magnet behavior can be observed in all these complexes. This work illustrated that care should be taken to interpret the magnetic data of octahedral CoII compounds. In addition, extended frameworks with long and flexible organic spacers are good candidates for the construction of SIMs with different axial ligands and different magnetic properties. [ABSTRACT FROM AUTHOR]

A tetradentate 8-hydroxyquinoline-based acyl hydrazone ligand (HL1 = 8-hydroxyquinoline-2-carboxaldehyde-(aminourea)hydrochloride) was elaborately used to construct a mononuclear dysprosium complex DyCl3HL1·CH3OH (1) with a nearly ideal pentagonal bipyramid coordination geometry (D5h) surrounding the Dy(iii) ion to achieve the significant performance of single-molecule magnets (SMMs). Meanwhile, the isolated high local symmetry center was successfully kept intact and further bridged to a series of double bipyramid systems by two phenolic oxygen atoms of the acyl hydrazone ligands (HL1 and HL2 = 8-hydroxyquinoline-2-carboxaldehyde-(benzoyl)hydrazine), with the formulae [Dy2Cl4(L1)2(CH3OH)2]·4C5H5N (2) and [Dy2Cl4(L2)2]·2CH3CN (3). In addition, the monodentate co-ligand anion was replaced by a larger sterically hindered ligand and a bidentate monovalent β-diketonate anion to generate [Dy2(tfo)4(L2)2(EtOH)2] (4), [Dy2(tta)4(L2)2(EtOH)2]·2(EtOH) (5) and [Dy2(dbm)4(L2)2(EtOH)2] (6) (tfo = trifluoromethanesulfonic acid, dbm = dibenzoylmethane, tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione) with eight-coordinate geometry. Strikingly, the dynamic magnetic measurements revealed that complexes 1–3 did not display the expected significant SMM performance albeit they had high local symmetry. In combination with ab initio calculation, the alignment of the coordination symmetric axis and the magnetic easy axis dominates the molecular magnetic anisotropy, and the magnetic easy axis could be modulated by the distribution of coordination atoms with different electrostatic properties. [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]

By modulating the substitution on the oxamide ligand, a mononuclear tetrahedral Co(II) complex (HNEt 3) 2 [CoL 2 ] (1) (H 2 L = N , N ′-bis(methanesulfonyl)oxamide) with subtle variation in the CoN 4 coordination environment was successfully synthesized, which displays zero-field slow magnetic relaxation and a hysteresis loop at 1.8 ​K. The complex adopts distorted tetrahedral coordination geometries with acute N–Co–N bite angle imposed by two mutually perpendicular oxamide ligands. Magnetic studies and computational results reveal that the acute N–Co–N bite angle seems to govern the overall magnetic anisotropy of tetrahedral Co(II) complexes with two bidentate chelated ligands containing N 4 -donor set. Upon reducing the bite angle, the D parameter increases gradually and reaches the maximum at about 81°, and then show a significant decrease as the angle continuing to decline. This research demonstrates that the easy-axial magnetic anisotropy can be maximized by reducing the bite angle to a certain extent, which is also feasible for tetrahedral cases with other donor sets. Magnetic studies and theoretical calculations indicate the D value of tetrahedral Co(II) complexes can be increased by appropriately reducing the bite angle of N-Co-N. [Display omitted] • A tetrahedral Co(II) complex with CoN 4 coordination environment was successfully synthesized. • The complex displays zero-field slow magnetic relaxation and a hysteresis loop at 1.8 K. • Magnetic and computational studies reveal that the N-Co-N bite angle seems to govern the overall magnetic anisotropy. • The D value of tetrahedral Co(II) complexes can be maximized by reducing the N-Co-N bite angle to a certain extent. [ABSTRACT FROM AUTHOR]

Inserting 3d metal-cmplex Cu(acac) 2 into the crystal lattice of paramagnetic Dy(hfac) 3 (H 2 O) 2 leads to the formation of the first true 3d-4f cocrystal made up of only reactants, which exhibits improved magnetic performance with evident SIM behavior. • A genuine 3d-4f complex cocrystal only composed of reactants. • The cocrystal displays evident SIM behavior. • Co-crystallization is a useful tool for improving the magnetic property of LnIII complex. Employing Cu(acac) 2 to react with Dy(hfac) 3 (H 2 O) 2 (where acac− = acetylacetonate and hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate), the first true 3d-4f metal-complex cocrystal with the composition of [Cu(acac) 2 ·Dy(hfac) 3 (H 2 O) 2 that only consists of reactants, was acquired and structurally characterized. Magnetic investigations revealed that the 4f coformer Dy(hfac) 3 (H 2 O) 2 does not show slow magnetic relaxation behavior even under an applied dc field of 2000 Oe down to 1.9 K, while the obtained 3d-4f cocrystal displays evident slow magnetic relaxation behavior associated with single-ion magnet (SIM) characteristic under the same dc field. This phenomenon is further supported and elucidated by the results of theoretical calculations together with the analyses of their crystal structures. Thus our results first indicate that 3d-4f co-crystallization technique is a useful tool for improving the magnetic performance of lanthanide complexes. [ABSTRACT FROM AUTHOR]