Slow Magnetic Relaxation in Ladder-Type and ... - ACS Publications

Article pubs.acs.org/IC

Cite This: Inorg. Chem. 2017, 56, 13482-13490

Slow Magnetic Relaxation in Ladder-Type and Single-Strand 2p−3d− 4f Heterotrispin Chains Meng Yang,† Jing Xie,† Zan Sun,† Licun Li,*,† and Jean-Pascal Sutter*,‡,§ †

Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry and Tianjin Key Laboratory of Metal and Molecule-based Material Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China ‡ Laboratoire de Chimie de Coordination (LCC), CNRS, 205 Route de Narbonne, F-31077 Toulouse, France § LCC, Université de Toulouse, UPS, INPT, F-31077 Toulouse, France S Supporting Information *

ABSTRACT: Ladder-type and chain 2p−3d−4f complexes based on a bridging nitronyl nitroxide radical, namely, [LnCu(hfac)5(NIT-Ph-pOCH2trz)]·0.5C6H14 [Ln = Y (1a), Dy (1b)] and [LnCu(hfac)5(NITPh-p-OCH2trz)] [Ln = Y (2a), Dy (2b); NIT-Ph-p-OCH2trz = 2-[4[(1H-1,2,4-triazol-1-yl)methoxy]phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate) have been successfully achieved through a one-pot reaction of the NIT-Ph-pOCH2trz radical with Cu(hfac)2 and Ln(hfac)3·2H2O. Complexes 1a and 1b feature a ladder-like structure, where the rails are made of Ln(III) and Cu(II) ions alternatively bridged by nitronyl nitroxide and the triazole units while the NIT-Ph-p-OCH2trz moieties act as the rungs of the ladder. Complexes 2a and 2b consist of one-dimensional nitronyl nitroxide bridged Ln coordination polymers with dangly Cu(II) units connected to the triazole moieties. All of compounds exhibit ferromagnetic NIT-Dy and/or NIT-Cu interactions. Both Dy derivatives (1b and 2b) show frequency-dependent out-of-phase magnetic susceptibility signals in a zero field indicating slow magnetic relaxation behavior.

■

INTRODUCTION Since the first single-chain magnet (SCM) consisting of alternating [Co(hfac)2] (hfac = hexafluoroacetylacetonate) and nitronyl nitroxide radical units was reported by Gatteschi et al. in 2001,1 the design and synthesis of one-dimensional (1D) systems exhibiting slow magnetic relaxation have attracted tremendous interest over the past decade. This research activity is to be related to the prospective relevance of such materials for magnetic high-density information storage, molecular spintronics, and quantum computing.2 One of the great challenges in this field remains the rational design aimed at combining large magnetic anisotropy and strong intrachain exchange interactions in the 1D systems. Effective synthetic approaches to SCMs comprise heterospin 1D chains such as 2p−3d,1,3 2p−4f,4 3d−3d′,5 3d−4d/5d,6 and 3d−4f7 and homospin systems with metal ions such as MnIII,8 CoII,9 or LnIII.10 Recently, a strategy involving three different spin carriers has emerged as an appealing synthetic approach toward SCMs. Visinescu et al. have reported the first heterotrimetallic SCM combining 3d, 4d, and 4f ions.11 Dunbar and co-workers reported a heterotrispin quasi-1D chain12 involving a TCNQF•− radical anion and binuclear [CuTb]3+ units, exhibiting SCM behavior. Along this line, nitronyl nitroxide radicals are also excellent paramagnetic bridging ligands for constructing a 1D system due to their two equivalent NO groups sharing the unpaired electron. It is worth noting that the © 2017 American Chemical Society

majority of 1D chains based on bridging nitronyl nitroxide radicals are homometal (3d or 4f) compounds3d,e,4 whereas heterotrispin chains remain very scarce but revealed interesting magnetic behavior.13 With the aim of further exploring the field of 1D coordination polymers combining three different spin carriers, we considered the possibility of using nitronyl nitroxide derivatives possessing additional groups likely to act as good ligands for 3d centers.14 Herein, we disclose four novel 1D 2p− 3d−4f complexes obtained using a triazole-functionalized nitronyl nitroxide radical, NIT-Ph-p-OCH2trz (Chart 1), namely, [LnCu(hfac)5(NIT-Ph-p-OCH2trz)]·0.5C6H14 [Ln = Y (1a), Dy (1b)] and [LnCu(hfac)5(NIT-Ph-p-OCH2trz)] [Ln = Y (2a), Dy (2b)], respectively. Complexes 1a and 1b exhibit a ladder-type structure, while complexes 2a and 2b feature a 1D Ln chain bridged by the NO moieties of radical ligands. Both Chart 1. NIT-Ph-p-OCH2trz Radical Ligand

Received: August 27, 2017 Published: October 9, 2017 13482

DOI: 10.1021/acs.inorgchem.7b02204 Inorg. Chem. 2017, 56, 13482−13490

Article

Inorganic Chemistry Table 1. Crystallographic Data and Structure Refinement Summary for 1 and 2 1a formula fw cryst syst space group T, K a, Å b, Å c, Å α, deg β, deg γ, deg V, Å3 θ, deg Z Dcalcd, g cm−3 μ, mm−1 unique reflns/Rint GOF (F2) R1/wR2 [I > 2σ(I)]a R1/wR2 (all data)a a

1b

2a

C44H32CuF30N5O13Ln 1561.21 1634.80 triclinic triclinic P1̅ P1̅ 113(2) 113(2) 12.619(3) 12.674(3) 13.548(3) 13.465(3) 18.375(4) 18.425(4) 82.97(3) 83.22(3) 87.73(3) 87.43(3) 71.53(3) 71.60(3) 2957(1) 2962(1) 1.12−28.09 1.11−25.00 2 2 1.753 1.833 1.493 1.767 14402/0.0331 10391/0.0306 1.059 1.064 0.0517/0.1220 0.0451/0.1238 0.0620/0.1334 0.0524/0.1344

2b

C123H75Cu3F90N15O39Ln3 4554.37 4775.14 monoclinic monoclinic P21/c P21/c 113(2) 113(2) 18.785(3) 18.975(3) 17.138(3) 17.231(3) 52.31(1) 52.50(1) 90 90 96.852(4) 96.380(4) 90 90 16720(5) 17057(5) 6.52−89.90 6.05−77.70 4 4 1.809 1.860 3.390 9.030 37880/0.1069 30702/0.1503 1.053 1.035 0.1071/0.2350 0.0779/0.1948 0.1502/0.2630 0.1212/0.2271

R1 = ∑(||Fo| − |Fc||)/∑|Fo|. wR2 = [∑w(|Fo|2 − |Fc|2)2/∑w(|Fo|2)2]1/2.

Table 2. Important Bond Lengths (Å) and Angles (deg) for Complexes 1 and 2 1a

1b

Ln−O(rad)

2.349(3)

2.334(3)

Ln−O(hfac) Ln−N Ln−O−N

2.322(3)−2.359(3) 2.572(4) 134.8(3)

2.327(4)−2.369(3) 2.578(4) 134.6(3)

Cu−O(rad) Cu−O(hfac) Cu−N

2.411(3) 1.940(3)−1.948(3) 2.464(4)

2.415(4) 1.944(4)−1.948(3) 2.469(4)

Cu−O−N

156.4(3)

156.2(4)

2b 2.408(6) 2.385(6) 2.386(7) 2.337(6)−2.396(6)

145.4(5) 138.7(5) 144.8(5)

146.1(6) 138.6(5) 145.7(5)

1.928(7)−2.190(7) 1.984(8) 1.984(8) 1.964(8)

1.924(7)−2.174(8) 1.985(8) 1.973(8) 1.972(8)

of dry CHCl3 was added. The solution was refluxed for 30 min, and then solid Cu(hfac)2 (0.0098 g, 0.02 mmol) was added. The resulting solution was stirred for 20 min, cooled to room temperature, and filtered off. The filtrate was kept at room temperature, and after 2 days, blue needlelike crystals (1a; yield 20%) and green block crystals (2a; yield 15%) suitable for X-ray diffraction (XRD) were obtained through the evaporation method. Anal. Calcd for C41H25CuF30N5O13Y (1a; without C6H14): C, 32.44; H, 1.66; N, 4.61. Found: C, 32.35; H, 1.76; N, 4.56. IR (KBr): 3505(w), 1651(s), 1502(m), 1471(m), 1256(s), 1226(s), 1142(s), 804(m), 662(m), 587(m) cm−1. Anal. Calcd for C41H25CuF30N5O13Y (2a): C, 32.44; H, 1.66; N, 4.61. Found: C, 32.51; H, 1.72; N, 4.69. IR (KBr): 3245(s), 1706(s), 1609(s), 1482(m), 1260(s), 1222(s), 1163(s), 1008(s), 767(s), 729(s) cm−1. Preparation of {[DyCu(hfac)5(NIT-Ph-p-OCH2trz)]·xC6H14} (1b, x = 0.5; 2b, x = 0). These two compounds have been synthesized following the procedure described above, but Dy(hfac)3·2H2O (0.0166 g, 0.02 mmol) was used in place of Y(hfac)3·2H2O. Anal. Calcd for C41H25CuF30N5O13Dy (1b; without C6H14): C, 30.94; H, 1.58; N, 4.42. Found: C, 30.87; H, 1.62; N, 4.37. IR (KBr): 3510(w), 1652(s), 1503(m), 1474(m), 1257(s), 1226(s), 1142(s), 801(m), 661(m), 589(m) cm−1. Anal. Calcd for C41H25CuF30N5O13Dy (2b): C, 30.94; H, 1.58; N, 4.42. Found: C, 30.82; H, 1.65; N, 4.39. IR (KBr):

Dy derivatives (1b and 2b) show frequency-dependent out-ofphase signals in a zero field.

■

2a 2.404(6) 2.360(6) 2.373(6) 2.329(8)−2.384(6)

EXPERIMENTAL SECTION

Materials and General Methods. All reagents were purchased from commercial sources and used without further purification. The radical ligand NIT-Ph-p-OCH2trz was synthesized according to the literature methods.15 Elemental analysis for C, H, and N were carried out using a PerkinElmer model 240 elemental analyzer. Powder X-ray diffraction (PXRD) data for all four complexes were collected at room temperature on a Rigaku Ultima IV diffractometer using graphitemonochromated Cu Kα radiation. Magnetic measurements were performed on microcrystalline powders held in gelatin capsules; for the Dy derivatives, the powders were mixed to grease. Data were collected on SQUID VSM/MPMS-5 and PPMS-9 magnetometers. The magnetic susceptibilities were corrected for the sample holder and diamagnetic contribution of the constituent atoms by using Pascal’s constants. Preparation of {[YCu(hfac)5(NIT-Ph-p-OCH2trz)]·xC6H14} (1a, x = 0.5; 2a, x = 0). Y(hfac)3·2H2O (0.0150 g, 0.02 mmol) was dissolved in dry boiling hexane (15 mL), and the solution was kept at reflux for 4 h. Then a solution of NIT-Ph-p-OCH2trz (0.0064 g, 0.02 mmol) in 3 mL 13483


Article

Inorganic Chemistry

Figure 1. 1D structure for complex 1b and local coordination geometry of the DyIII ion (H and F atoms and solvent are not shown for the sake of clarity). 3243(s), 1607(s), 1482(m), 1261(s), 1221(s), 1163(s), 1005(s), 765(s), 727(s) cm−1. X-ray Structure Determination. The crystal structure data of the four complexes were collected at 113 K with a Rigaku Saturn CCD diffractometer, employing graphite-monochromated Mo Kα (1a and 1b) and Cu Kα (2a and 2b) radiation, respectively. The structures were solved by direct methods with the SHELXS-2014 program and refined by full-matrix least squares on F2 with SHELXL-2014.16 All of the non-H atoms have been refined anisotropically and the H atoms were positioned geometrically and refined as riding atoms with a uniform value of Uiso. Relevant crystal data, collection parameters, and refinement results are given in Table 1. Selected bond lengths and angles of the complexes are listed in Tables 2 and S1−S4.

■

positions are occupied by one O atom (O1) of the NO group and one N atom of the triazole of another molecule, respectively. The Cu−Orad bond distance is 2.415(4) Å, and the Cu−N bond length is 2.469(4) Å. Four O atoms from two bidentate hfac ligands lie in the equatorial positions with the Cu−O bond distances of 1.944(4)−1.948(3) Å. The paramagnetic organic ligand coordinates to the metal centers in a tetradentate μ4-η1:η1:η1:η1 mode. It is linked to two DyIII and two CuII ions respectively via its two NO groups and two N atoms of the triazole ring, resulting in a ladder-like arrangement in which the anisole moieties form the rungs of the ladder. The Dy···Cu separations through the NIT motif and the triazole ring are of 8.50 and 6.93 Å, respectively. The Dy···Dy and Cu··· Cu distances across the rungs are 10.64 and 9.04 Å, respectively. Complexes 2a and 2b crystallize in the monoclinic system with the space group P21/c and also display an isostructural structure. Complex 2b is chosen to describe the structure in more detail. The asymmetry unit contains one [DyCu(hfac)5(NIT-Ph-p-OCH2trz)]2 and a [DyCu(hfac)5(NIT-Php-OCH2trz)] unit, which result in two crystallographically independent 1D chains in the crystal lattice. In the chain, each NIT-Ph-p-OCH2trz radical behaves as a tridentate ligand to bind two DyIII ions and one CuII ion in the μ3-η1:η1:η1 mode. The NIT moiety bridges two Dy(hfac)3 units developing into a 1D chain. One N atom from the triazole ring is coordinated to a Cu(hfac)2 unit in the equatorial position. Each DyIII ion is coordinated by two O atoms from two radical ligands and six O atoms from three hfac ligands (Figure 2). Shape analysis of the coordination sphere of the DyIII center indicates that all three DyIII ions are located in distorted square-antiprismatic geometries (D4d; Table S5). The Dy−O(hfac) bond lengths are in the range of those found for 2b (Table 2), and Dy−O(radical)

RESULTS AND DISCUSSION

Synthesis. A promising approach for the rational design of 2p−3d−4f compounds is offered by nitronyl nitroxide derivatives containing additional groups able to coordinate to a metal ion. According to the hard−soft acid−base theory, amine-functionalized nitronyl nitroxides are appealing ligands because of their NO and N groups with coordination preferences for rare-earth and transition-metal ions, respectively. This strategy was recently validated by a series of 2p− 3d−4f compounds.14,17 We now considered triazole-functionalized nitronyl nitroxide because this group is likely to act as a bridging ligand much like the nitronyl nitroxie moiety. The 2p− 3d−4f compounds were obtained by a self-assembly reaction upon mixing the nitronyl nitroxide radical NIT-Ph-p-OCH2trz, Cu(hfac)2, and Ln(hfac)3 in hexane. Two kinds of crystals were formed, and they could be easily separated because of their different colors and shapes. They were found to have similar compositions but revealed different 1D arrangements corresponding to a ladder-type chain and a single-strand coordination polymer, respectively, 1a/1b and 2a/2b. The purities of these four polycrystalline samples were confirmed by PXRD (Figures S1 and S2). Description of the Crystal Structures. X-ray analysis revealed that complexes 1a and 1b crystallize in the triclinic space group P1̅ and are isomorphous. Both complexes possess a ladder-like structure; complex 1b will be briefly described as a representative. As shown in Figure 1, each DyIII ion is located in an eight-coordinated environment with one N atom from the triazole ring of NIT-Ph-p-OCH2trz and seven O atoms, six of which are from three hfac ligands and one is from the NO group of another radical ligand. The coordination sphere around the DyIII ion was analyzed using SHAPE software,18 indicating a distorted square-antiprismatic geometry (D4d; Table S5). The Dy−O(radical) and Dy−N distances are 2.334(3) and 2.578(4) Å, respectively, while the Dy−O(hfac) distances span from 2.327(4) to 2.369(3) Å. The CuII ion is in a (4 + 2)-distorted octahedral environment, in which the axial

Figure 2. 1D structure of complex 2b (H and F atoms are omitted for clarity). 13484


Article

Inorganic Chemistry bond lengths vary from 2.385(6) to 2.408(6) Å. All of the CuII ions are five-coordinated (Figure S9). The Cu1 and Cu3 atoms are in distorted square-pyramidal geometries, where one O atom from the hfac ligand occupies the apical site. The equatorial plane is occupied by three O atoms from two bidentate hfac ligands and one N atom from the triazole unit. The Cu−N distances are 1.985(8) Å for Cu1 and 1.973(8) Å for Cu3. The Cu−O distances in the equatorial plane are comprised between 1.924(7) and 1.956(6) Å for Cu1 and Cu3. The apical Cu−O bond distances are 2.174(8) and 2.188(9) Å for Cu1 and Cu3, respectively. The Cu2 sits in a trigonalbipyramidal environment. Its equatorial plane is formed by two O atoms (O23 and O25) from two hfac ligands and one N atom (N10) from the triazole unit; the apical positions are occupied by two hfac O atoms (O24 and O26). The axial Cu− O distances are 2.110(9) and 1.925(8) Å. Packing of the chains of complex 2b is shown in Figure S10. The shortest intrachain Dy···Dy distance bridged by two NO groups is 8.66 Å, while the nearest interchain Dy···Dy, Cu···Dy, and Cu···Cu separations are found to be 9.75, 9.01, and 9.39 Å, respectively. Magnetic Properties. The temperature dependences of the molar magnetic susceptibility, χM, for complexes 1a and 2a are displayed in Figure 3 in the form of χMT versus T. For

were analyzed by a theoretical expression for the susceptibility ̂ ŜCu. (1) deduced from the spin Hamiltonian Ĥ = −2JSRad χ=

2Ng 2β 2 [3 + exp( − 2J /kT )]−1 kT

(1)

The best fit of the experimental data yielded J = 20.81 cm−1 and g = 2.13. The observed ferromagnetic coupling between the CuII ion and the axial NO unit results from the orthogonality of the magnetic orbital (dx2−y2) of the CuII ion and the radical π* magnetic orbital.19,20 The magnitude of the exchange coupling in 1a is in agreement with those of the reported similar CuII− NO couplings.21−23 The M versus H curve at 2.0 K for complex 1a shows that magnetization smoothly increases with the applied directcurrent (dc) field to reach the value of 2.07 Nβ at 7 T (Figure S11). The experimental magnetization value is above the magnetization calculated from the Brillouin function for two noncorrelated S = 1/2 spins employing g = 2.0 and T = 2 K, which is a further confirmation of the ferromagnetic interactions between the CuII ion and the coordinated radical group. Furthermore, the magnetization value is well reproduced by the behavior obtained with the Brillouin function for S = 1 with g = 2.13, indicating that complex 1a has an S = 1 spin ground state. For complex 2a, the χMT value at room temperature is 0.82 cm3 K mol−1, which is slightly above the expected value of 0.75 cm3 K mol−1 corresponding to the Curie contributions of one radical (S = 1/2) and one CuII (S = 1/2) ion with g = 2.0. With decreasing temperature, the χMT value decreases more and more rapidly to reach 0.47 cm3 K mol−1 at 2 K. According to the crystal structure, 2a can be considered as one 1D S = 1/2 radical chain with uncoupled CuII ions; thus, the magnetic data were analyzed by the Heisenberg chain model with S = 1/2 (the spin Hamiltonian Ĥ = − 2J ∑i ≠ j Sî Sĵ )24 to which the contribution for an independent S = 1/2 was added (see eq 2). χ= +

Ng12β 2 kT Ng2 2β 2 3kT

×

0.25 + 0.18207x 2 1 + 1.5467x + 3.4443x 3

S(S + 1)

x = |J | /kT

S = 1/2

(2)

The best fit resulted in the magnetic parameters J = −5.82 cm−1, g1 = 1.99, and g2 = 2.20. The value of J is comparable to the values found for other yttrium nitronyl nitroxide compounds.25,26 The substantial antiferromagnetic interaction between two radical units via the diamagnetic YIII ion is usually attributed to the superexchange interaction through the empty 5s or 4d orbitals of Y or superexchange mediated by the hfac ligands.25 The latter interaction is suggested by the positioning of the p orbitals of the O atoms of the hfac ligand perpendicular to the O1−O2 direction of the two NO groups, which may ensure orbital overlap, thus providing a passageway for antiferromagnetic interactions.25c The field dependence of magnetization shows a steady increase of M with the magnetic field, but saturation is not reached (Figure S12). The value of 1.73 Nβ reached for 70 kOe confirms that antiferromagnetic interactions are operative in this system. For complexes 1b and 2b, the values of χMT at 300 K are respectively 14.95 and 15.08 cm3 K mol−1, close to the expected value of 14.92 cm3 K mol−1 for one DyIII ion, one radical (S =

Figure 3. χMT versus T plots of complexes 1a (top) and 2a (bottom). The solid lines represent the best fits of the experimental data to the magnetic models described in the text.

compound 1a, the χMT product is 0.84 cm3 K mol−1 at 300 K, which is slightly above the expected value of 0.75 cm3 K mol−1 for one isolated radical (S = 1/2) and one CuII (S = 1/2) ion with g = 2.0. Upon cooling, χMT increases to reach a value of 1.07 cm3 K mol−1 at 2 K, thus revealing ferromagnetic radical− CuII interactions in the ladder. The magnetic behavior of complex 1a mainly results from isolated Cu−radical magnetic units due to diamagnetic YIII ions; therefore, the magnetic data 13485


Article

Inorganic Chemistry 1

/2), and one CuII (S = 1/2) ion with g = 2.0 in the absence of exchange interactions. For complex 1b, the value of χMT gradually decreases when the temperature is lowered to reach a value of 14.0 cm3 K mol−1 at 24 K (Figure 4), which can be

plot shows a linear region between 4.0 and 14.0 K (Figure 4, inset), confirming the 1D Ising-like character of this compound. Analysis of the linear variation of the data yielded for Δξ a value of 0.24 K. The M versus H behavior at 2.0 K for 1b is characterized by a fast increase of M for fields below 10 kOe, followed by a more gradual but continuous augmentation for higher fields to reach 7.0 Nβ at 50 kOe (Figure S13). For complex 2b, with decreasing temperature, the χMT product smoothly decreases from 15.08 to 11.94 cm3 K mol−1 at 8.5 K, then slightly increases to reach 12.55 cm3 K mol−1 at 4.0 K, and finally drops to 9.32 cm3 K mol−1 at 2.0 K (Figure 4). The observed χMT−T curve is similar to those of the previously reported dysprosium nitronyl nitroxide chains.4a,b,27 Complex 2b also shows a linear region between 4.4 and 8.8 K, and the value of Δξ is 0.451 K, confirming the 1D Ising-like character of this complex (Figure 4, inset). The field dependence of magnetization at 2 K for this compound shows a behavior similar to that of 1b (Figure S14), with magnetization of 7.36 Nβ for 70 kOe. In order to assess the relaxation dynamics of 1b and 2b, the frequency dependence of the χ′ and χ″ signals were examined in a frequency range of 10−10000 Hz without applying a dc field. For complex 1b, both the in-phase and out-of-phase signals show temperature dependencies, and two well-resolved maxima in χ″ are observed below 2.6 K (Figures 5 and S16). The relaxation time (τ) was extracted by a fitting to the χ″ versus frequency curves using a Debye model modified for two relaxation processes,28 and the obtained parameters are given in Table S6. The variation of τ as a function of T−1 (Figure 6)

Figure 4. Plots of χMT versus T for 1b (top) and 2b (bottom). Insets: ln(χT) versus 1/T plots. The solid lines represent the fits.

attributed to the crystal-field effect for DyIII. As the temperature is further lowered, the curve increases abruptly, reaches 14.50 cm3 K mol−1 at 4.0 K, and finally drops to 14.27 cm3 K mol−1 at 2.0 K. The observed increase of the χMT value at low temperature may be ascribed to the anticipated ferromagnetic interaction between the metal ions and the coordinated NO group of the organic radical. Moreover, evidence for exchange interactions between the Dy and Cu centers mediated by the triazole ligand is provided by the plot of ln(χMT) = f(T). For a 1D Ising system, the χT product is expected to follow a behavior such as χT varies as Cexp(Δ ξ /T), where Δ ξ corresponds to the energy barrier for producing a domain wall along the chain.2b For complex 1b, the ln(χT) versus 1/T

Figure 6. Plots of ln τ versus 1/T for complex 1b. The solid line represents the fit to the Arrhenius law.

Figure 5. (left) Frequency dependence of the out-of-phase components for the ac magnetic susceptibility in a zero field for 1b. (right) Cole−Cole plots for 1b. The solid lines represent the best fits with modified Debye functions (see the text). 13486


Article

Inorganic Chemistry

Figure 7. (left) Frequency dependence of the out-of-phase components for the ac magnetic susceptibility in a zero field for 2b. (right) Cole−Cole plots for 2b. The solid lines represent the best fits with generalized Debye functions (see the text).

4.0 K. The present work illustrates that the use of functionalized nitronyl nitroxide radicals represents an appealing strategy for preparing 2p−3d−4f heterotrispin compounds, not only to enrich the structural diversity of 2p−3d−4f compounds but also for to modulate the magnetic behavior of the 2p−3d−4f systems.

shows mainly a temperature-independent behavior for the highfrequency maximum, while a linear variation is found for the low-frequency peaks. The low-frequency data were fitted using the Arrhenius equation to afford the parameters Ueff = 21.0 K and τ0 = 5.37 × 10−8 s. The Cole−Cole plots have been constructed, and two relaxation processes are also obvious below 2.6 K (Figure 5). Information on the distribution width of the relaxation time was obtained from the fitting of the relaxation processes via a modified Debye model (vide ante), yielding values of 0.01−0.49 for α1 and 0.04−0.27 for α2 for temperatures between 2.0 and 3.0 K. Multiple relaxation processes classically arise from structurally inequivalent magnetic centers29 but also could derive from the individual magnetic ions.30 For the latter, additional relaxation processes can be associated with the weak magnetic coupling or phonon effects.31 For 1b, the magnetic relaxation found for the lower frequencies may be attributed to the Orbach process, while the slow relaxation detected at high frequency is likely to be associated with a phonon process. To come to a conclusion on the relaxation mechanism for the present system, further investigations such as magnetic dilution and theoretical calculations would be required. For 2b, both χ′ and χ″ components of the alternating-current (ac) susceptibility feature strong frequency-dependent phenomena (Figure 7). The peak maximum of the χ″ signal exhibits a gradual shift toward the high-frequency region as the temperature is increased. The Cole−Cole plots of 2b exhibit a symmetrically semicircular shape below 2.7 K (Figure 7); their analysis with the generalized Debye model32 yielded the magnetization relaxation time (τ) and distribution width (α) (Table S7). The obtained α values vary from 0.18 to 0.49, indicating a rather broad distribution of relaxation times. As shown in Figure S18, the relaxation time (τ) versus T−1 curve features a linear relationship. The best fit to the Arrhenius equation gave the effective energy barrier (Ueff) of 29.0 K with a preexponential factor (τ0) of 6.1 × 10−10 s, which well compares to those of the previously reported dysprosium nitronyl nitroxide SCMs.4a,b,27

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b02204. Tables of selected bond lengths and angles, XRD analysis, crystal structure, packing diagram, additional magnetic data, and tables for the fitting results of complexes 1b and 2b using Debye model (PDF) Accession Codes

CCDC 1558373−1558376 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (L.L.). *E-mail: [email protected] (J.-P.S.). ORCID

Licun Li: 0000-0001-8380-2946 Jean-Pascal Sutter: 0000-0003-4960-0579 Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant 21471083).

■

CONCLUSIONS A new family of heterotrispin complexes based on triazolesubstituted nitronyl nitroxide radicals has been successfully obtained through the self-assembly method. Remarkably, an unprecedented ladder-like arrangement of alternating 2p−3d− 4f spins was achieved, with exchange interactions propagating along the rails. The corresponding derivative made of dysprosium exhibits slow magnetic relaxation behavior below

REFERENCES

(1) Caneschi, A.; Gatteschi, D.; Lalioti, N.; Sangregorio, C.; Sessoli, R.; Venturi, G.; Vindigni, A.; Rettori, A.; Pini, M. G.; Novak, M. A. Cobalt(II)-Nitronyl Nitroxide Chains as Molecular Magnetic Nanowires. Angew. Chem., Int. Ed. 2001, 40, 1760−1763. (2) (a) Gatteschi, D.; Sessoli, R.; Villain, J. Molecular Nanomagnets; Oxford University Press: Oxford, U.K., 2006. (b) Coulon, C.; Miyasaka, H.; Clérac, R. Single-Chain Magnets: Theoretical Approach

13487


Article

Inorganic Chemistry and Experimental Systems. Struct. Bonding (Berlin) 2006, 122, 163− 206. (c) Sun, H. L.; Wang, Z. M.; Gao, S. Strategies towards singlechain magnets. Coord. Chem. Rev. 2010, 254, 1081−1100. (d) Troiani, F.; Affronte, M. Molecular spins for quantum information technologies. Chem. Soc. Rev. 2011, 40, 3119−3129. (e) Bogani, L.; Vindigni, A.; Sessoli, R.; Gatteschi, D. Single chain magnets: where to from here? J. Mater. Chem. 2008, 18, 4750−4758. (f) Zhang, W. X.; Ishikawa, R.; Breedlove, B.; Yamashita, M. Single-chain magnets: beyond the Glauber model. RSC Adv. 2013, 3, 3772−3798. (3) (a) Ishikawa, R.; Katoh, K.; Breedlove, B. K.; Yamashita, M. MnIII (tetra-biphenyl- porphyrin)−TCNE Single-Chain Magnet via Suppression of the Interchain Interactions. Inorg. Chem. 2012, 51, 9123− 9131. (b) Miyasaka, H.; Madanbashi, T.; Sugimoto, K.; Nakazawa, Y.; Wernsdorfer, W.; Sugiura, K. i.; Yamashita, M.; Coulon, C.; Clérac, R. Single-Chain Magnet Behavior in an Alternated One-Dimensional Assembly of a MnIII Schiff-Base Complex and a TCNQ Radical. Chem. - Eur. J. 2006, 12, 7028−7040. (c) Ishii, N.; Okamura, Y.; Chiba, S.; Nogami, T.; Ishida, T. Giant coercivity in a one-dimensional cobaltradical coordination Magnet. J. Am. Chem. Soc. 2008, 130, 24−25. (d) Vaz, M. G. F.; Cassaro, R. A. A.; Akpinar, H.; Schlueter, J. A.; Lahti, P. M.; Novak, M. A. A Cobalt Pyrenylnitronylnitroxide SingleChain Magnet with High Coercivity and Record Blocking Temperature. Chem. - Eur. J. 2014, 20, 5460−5467. (e) Cassaro, R. A. A.; Reis, S. G.; Araujo, T. S.; Lahti, P. M.; Novak, M. A.; Vaz, M. G. F. A SingleChain Magnet with a Very High Blocking Temperature and a Strong Coercive Field. Inorg. Chem. 2015, 54, 9381−9383. (4) (a) Bogani, L.; Sangregorio, C.; Sessoli, R.; Gatteschi, D. Molecular Engineering for Single-Chain-Magnet Behavior in a OneDimensional Dysprosium-Nitronyl Nitroxide Compound. Angew. Chem., Int. Ed. 2005, 44, 5817−5821. (b) Bernot, K.; Bogani, L.; Caneschi, A.; Gatteschi, D.; Sessoli, R. A family of rare-earth-based single chain magnets: playing with anisotropy. J. Am. Chem. Soc. 2006, 128, 7947−7956. (c) Liu, R. N.; Li, L. C.; Wang, X. L.; Yang, P. P.; Wang, C.; Liao, D. Z.; Sutter, P. J. Smooth transition between SMM and SCM-type slow relaxing dynamics for a 1-D assemblage of {Dy(nitronyl nitroxide)2} units. Chem. Commun. 2010, 46, 2566− 2568. (d) Li, C.; Sun, J.; Yang, M.; Sun, G. F.; Guo, J. N.; Ma, Y.; Li, L. C. From Monomeric Species to One-Dimensional Chain: Enhancing Slow Magnetic Relaxation through Coupling Mononuclear Fragments in Ln-rad System. Cryst. Growth Des. 2016, 16, 7155−7162. (e) Wang, X. F.; Li, Y. G.; Hu, P.; Wang, J. J.; Li, L. C. Slow magnetic relaxation and field-induced metamagnetism in nitronyl nitroxide-Dy(III) magnetic chains. Dalton Trans. 2015, 44, 4560−4567. (5) (a) Ferrando-Soria, J.; Cangussu, D.; Eslava, M.; Journaux, Y.; Lescouezec, R.; Julve, M.; Lloret, F.; Pasan, J.; Ruiz-Perez, C.; Lhotel, E.; Paulsen, C.; Pardo, E. Rational Enantioselective Design of Chiral Heterobimetallic Single-Chain Magnets: Synthesis, Crystal Structures and Magnetic Properties of Oxamato-Bridged MIICuII Chains (M = Mn, Co). Chem. - Eur. J. 2011, 17, 12482−12494. (b) Wang, S.; Zuo, J. L.; Gao, S.; Song, Y.; Zhou, H. C.; Zhang, Y. Z.; You, X. Z. The observation of superparamagnetic behavior in molecular nanowires. J. Am. Chem. Soc. 2004, 126, 8900−8901. (c) Hoshino, N.; Iijima, F.; Newton, G. N.; Yoshida, N.; Shiga, T.; Nojiri, H.; Nakao, A.; Kumai, R.; Murakami, Y.; Oshio, H. Three-way switching in a cyanide-bridged [CoFe] chain. Nat. Chem. 2012, 4, 921−926. (d) Miyasaka, H.; Madanbashi, T.; Saitoh, A.; Motokawa, N.; Ishikawa, R.; Yamashita, M.; Bahr, S.; Wernsdorfer, W.; Clerac, R. Cyano-Bridged MnIII−MIII Single-Chain Magnets with MIII = CoIII, FeIII, MnIII, and CrIII. Chem. Eur. J. 2012, 18, 3942−3954. (e) Clérac, R.; Miyasaka, H.; Yamashita, M.; Coulon, C. Evidence for single-chain magnet behavior in a MnIII− NiII chain designed with high spin magnetic units: a route to high temperature metastable magnets. J. Am. Chem. Soc. 2002, 124, 12837− 12844. (f) Shiga, T.; Maruyama, K.; Newton, G. N.; Inglis, R.; Brechin, E. K.; Oshio, H. Chiral Single-Chain Magnet: Helically Stacked [MnIII2CuII] Triangles. Inorg. Chem. 2014, 53, 4272−4274. (g) Rams, M.; Peresypkina, E. V.; Mironov, V. S.; Wernsdorfer, W.; Vostrikova, K. E. Magnetic relaxation of 1D coordination polymers (X)2 [Mn (acacen) Fe (CN)6], X = Ph4P+, Et4N+. Inorg. Chem. 2014, 53, 10291− 10300. (h) Wang, Y. Q.; Yue, Q.; Gao, E. Q. Effects of Metal Blending

in Random Bimetallic Single-Chain Magnets: Synergetic, Antagonistic, or Innocent. Chem. - Eur. J. 2017, 23, 896−904. (i) Lescouëzec, R.; Vaissermann, J.; Ruiz-Pérez, C.; Lloret, F.; Carrasco, R.; Julve, M.; Verdaguer, M.; Dromzee, Y.; Gatteschi, D.; Wernsdorfer, W. Cyanidebridged iron (III)−cobalt (II) double zigzag ferromagnetic chains: two new molecular magnetic nanowires. Angew. Chem., Int. Ed. 2003, 42, 1483−1486. (j) Toma, L. M.; Lescouëzec, R.; Pasán, J.; Ruiz-Pérez, C.; Vaissermann, J.; Cano, J.; Carrasco, R.; Wernsdorfer, W.; Lloret, F.; Julve, M. [Fe (bpym)(CN)4]−: A New Building Block for Designing Single-Chain Magnets. J. Am. Chem. Soc. 2006, 128, 4842−4853. (k) Miyasaka, H.; Julve, M.; Yamashita, M.; Clérac, R. Slow dynamics of the magnetization in one-dimensional coordination polymers: single-chain magnets. Inorg. Chem. 2009, 48, 3420−3437. (6) (a) Wang, X. Y.; Avendaño, C.; Dunbar, K. R. Molecular magnetic materials based on 4d and 5d transition metals. Chem. Soc. Rev. 2011, 40, 3213−3238. (b) Guo, J. F.; Wang, X. T.; Wang, B. W.; Xu, G. C.; Gao, S.; Szeto, L.; Wong, W. T.; Wong, W. Y.; Lau, T. C. One-Dimensional Ferromagnetically Coupled Bimetallic Chains Constructed with trans-[Ru(acac)2(CN)2]−: Syntheses, Structures, Magnetic Properties, and Density Functional Theoretical Study. Chem. - Eur. J. 2010, 16, 3524−3535. (c) Zhang, D. P.; Zhang, L. F.; Chen, Y. T.; Wang, H. L.; Ni, Z. H.; Wernsdorfer, W.; Jiang, J. Z. Heterobimetallic porphyrin-based single-chain magnet constructed from manganese (III)-porphyrin and trans-dicyanobis (acetylacetonato) ruthenate (III) containing co-crystallized bulk anions and cations. Chem. Commun. 2010, 46, 3550−3552. (d) Feng, X.; Harris, T. D.; Long, J. R. Influence of structure on exchange strength and relaxation barrier in a series of FeIIReIV(CN)2 single-chain magnets. Chem. Sci. 2011, 2, 1688−1694. (e) Zhang, Y.-Q.; Luo, C. L.; Wu, X. B.; Wang, B. W.; Gao, S. Magneto-structural correlations in a family of FeIIReIV(CN)2 single-chain magnets: density functional theory and Ab initio calculations. Inorg. Chem. 2014, 53, 3503−3510. (f) Peresypkina, E. V.; Majcher, A. M.; Rams, M.; Vostrikova, K. E. A single chain magnet involving hexacyanoosmate. Chem. Commun. 2014, 50, 7150−7153. (g) Feng, X.; Liu, J.; Harris, T. D.; Hill, S.; Long, J. R. Slow magnetic relaxation induced by a large transverse zero-field splitting in a MnIIReIV(CN)2 single-chain magnet. J. Am. Chem. Soc. 2012, 134, 7521−7529. (h) Venkatakrishnan, T. S.; Sahoo, S.; Bréfuel, N.; Duhayon, C.; Paulsen, C.; Barra, A.-L.; Ramasesha, S.; Sutter, J.-P. Enhanced Ion Anisotropy by Nonconventional Coordination Geometry: Single-Chain Magnet Behavior for a [{FeIIL}2{NbIV(CN)8}] Helical Chain Compound Designed with HeptacoordinateFeII. J. Am. Chem. Soc. 2010, 132, 6047−6056. (7) (a) Andruh, M.; Costes, J. P.; Diaz, C.; Gao, S. 3d−4f combined chemistry: synthetic strategies and magnetic properties. Inorg. Chem. 2009, 48, 3342−3359. (b) Zhang, J. W.; Kan, X. M.; Liu, B. Q.; Liu, G. C.; Tian, A. X.; Wang, X. L. Systematic Investigation of Reaction-Time Dependence of Three Series of Copper−Lanthanide/Lanthanide Coordination Polymers: Syntheses, Structures, Photoluminescence, and Magnetism. Chem. - Eur. J. 2015, 21, 16219−16228. (c) Gheorghe, R.; Madalan, A. M.; Costes, J. P.; Wernsdorfer, W.; Andruh, M. A heterotrimetallic 3d−3d′−4f single chain magnet constructed from anisotropic high-spin 3d−4f nodes and paramagnetic spacers. Dalton Trans. 2010, 39, 4734−4736. (d) Yao, M. X.; Zheng, Q.; Qian, K.; Song, Y.; Gao, S.; Zuo, J. L. Controlled Synthesis of Heterotrimetallic Single-Chain Magnets from Anisotropic High-Spin 3d−4f Nodes and Paramagnetic Spacers. Chem. - Eur. J. 2013, 19, 294−303. (8) (a) Miyasaka, H.; Saitoh, A.; Abe, S. Magnetic assemblies based on Mn(III) salen analogues. Coord. Chem. Rev. 2007, 251, 2622−2664. (b) Xu, H. B.; Wang, B. W.; Pan, F.; Wang, Z. M.; Gao, S. Stringing Oxo-Centered Trinuclear [MnIII3O] Units into Single-Chain Magnets with Formate or Azide Linkers. Angew. Chem., Int. Ed. 2007, 46, 7388− 7392. (c) Zhang, Y. Z.; Zhao, H. H.; Funck, E.; Dunbar, K. R. A Single-Chain Magnet Tape Based on Hexacyanomanganate (III). Angew. Chem., Int. Ed. 2015, 54, 5583−5587. (d) Zhang, W. X.; Shiga, T.; Miyasaka, H.; Yamashita, M. New approach for designing singlechain magnets: organization of chains via hydrogen bonding between nucleobases. J. Am. Chem. Soc. 2012, 134, 6908−6911. (e) Chen, X.; Wu, S. Q.; Cui, A. L.; Kou, H. Z. A cyano-bridged single-chain magnet 13488


Article

Inorganic Chemistry

(16) (a) Sheldrick, G. M. SHELXS-2014, Program for structure solution; Universität of Gö ttingen: Gö ttingen, Germany, 2014. (b) Sheldrick, G. M. SHELXL-2014, Program for structure refinement; Universität of Göttingen: Göttingen, Germany, 2014. (17) (a) Patrascu, A. A.; Calancea, S.; Briganti, M.; Soriano, S.; Madalan, A. M.; Cassaro, R. A. A; Caneschi, A.; Totti, F.; Vaz, M. G. F.; Andruh, M. A chimeric design of heterospin 2p−3d, 2p−4f, and 2p−3d−4f complexes using a novel family of paramagnetic dissymmetric compartmental ligands. Chem. Commun. 2017, 53, 6504−6507. (b) Zhu, M.; Li, Y. G.; Ma, Y.; Li, L. C.; Liao, D. Z. Unprecedented NitronylNitroxide Bridged 3d−4f Complexes: Structure and Magnetic Properties. Inorg. Chem. 2013, 52, 12326−12328. (c) Wang, X. F.; Li, H. D.; Sun, J.; Yang, M.; Li, C.; Li, L. C. LnIII−CoII heterometallic chains based on pyridine substituted nitronyl nitroxides. New J. Chem. 2017, 41, 2973−2979. (d) Yang, M.; Sun, J.; Guo, J. N.; Sun, G. F.; Li, L. C. Cu−Ln compounds based on nitronyl nitroxide radicals: synthesis, structure, and magnetic and fluorescence properties. CrystEngComm 2016, 18, 9345−9356. (18) (a) Casanova, D.; Llunell, M.; Alemany, P.; Alvarez, S. The Rich Stereochemistry of Eight-Vertex Polyhedra: A Continuous Shape Measures Study. Chem. - Eur. J. 2005, 11, 1479−1494. (b) Lluncll, M.; Casanova, D.; Circra, J.; Bofill, J. M.; Alcmany, P.; Alvarez, S.; Pinsky, M.; Avnir, D. SHAPE, version 2.1; University of Barcelona and Hebrew University of Jerusalem: Barcelona, Spain, and Jerusalem, Israel, 2005. (19) Gatteschi, D.; Laugier, J.; Rey, P.; Zanchini, C. Crystal and molecular structure and magnetic properties of the adducts of copper(II) hexafluoroacetylacetonate with the nitroxide ligand 2phenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl 3-oxide. Inorg. Chem. 1987, 26, 938−943. (20) Cabello, C. I.; Caneschi, A.; Carlin, R. L.; Gatteschi, D.; Rey, P.; Sessoli, R. Structure and magnetic properties of ferromagnetic alternating spin chains. Inorg. Chem. 1990, 29, 2582−2587. (21) Caneschi, A.; Gatteschi, D.; Laugier, J.; Rey, P. Ferromagnetic alternating spin chains. J. Am. Chem. Soc. 1987, 109, 2191−2192. (22) Caneschi, A.; Gatteschi, D.; Grand, A.; Laugier, J.; Pardi, L.; Rey, P. Moderate ferromagnetic exchange between copper(II) and a nitronyl nitroxide in a square-pyramidal adduct. MO interpretation of the mechanism of exchange in copper (II)-nitroxide complexes. Inorg. Chem. 1988, 27, 1031−1035. (23) Wang, X. F.; Hu, P.; Li, Y. G.; Li, L. C. Construction of Nitronyl Nitroxide Based 3d−4f Clusters: Structure and Magnetism. Chem. Asian J. 2015, 10, 325−328. (24) Hiller, W.; Strahle, J.; Datz, A.; Hanack, M.; Hatfield, W. E.; ter Haar, L. W.; Gütlich, P. Synthesis, Structure, and Magnetic Properties of catena-(μ-Oxo)(hemiporphyrazinato)iron(IV), the First Polymeric μ-Oxo-Bridged Complex of Iron. J. Am. Chem. Soc. 1984, 106, 329− 335. (25) (a) Benelli, A.; Caneschi, D.; Gatteschi, L.; Pardi, P.; Rey, P. One-dimensional magnetism of a linear chain compound containing yttrium (III) and a nitronyl nitroxide radical. Inorg. Chem. 1989, 28, 3230−3234. (b) Sutter, J.-P.; Kahn, M. L.; Golhen, S.; Ouahab, L.; Kahn, O. Synthesis and magnetic behavior of rare-earth complexes with N,O-chelating nitronylnitroxidetriazole ligands: Example of a [GdIII{organic radical}2] compound with an S = 9/2 ground state. Chem. - Eur. J. 1998, 4, 571. (c) Sutter, J.-P.; Kahn, M. L. In Magnetism: molecules to materials; Miller, J. S., Drillon, M., Eds.; WileyVCH, 2005; Vol. 5, pp 161−188. (d) Jung, J.; Puget, M.; Cador, O.; Bernot, K.; Calzado, C. J.; Le Guennic, B. Analysis of the Magnetic Exchange Interactions in Yttrium (III) Complexes Containing Nitronyl Nitroxide Radicals. Inorg. Chem. 2017, 56, 6788−6801. (26) Hu, P.; Zhang, C. M.; Gao, Y. Y.; Li, Y. G.; Ma, Y.; Li, L. C.; Liao, D. Z. Lanthanide−radical linear chain compounds based on 2,4,4,5,5-pentamethylimidazoline-1-oxyl-3-oxide: Structure and magnetic properties. Inorg. Chim. Acta 2013, 398, 136−140. (27) (a) Hu, P.; Wang, X. F.; Ma, Y.; Wang, Q. L.; Li, L. C.; Liao, D. Z. A new family of Ln−radical chains (Ln = Nd, Sm, Gd, Tb and Dy): synthesis, structure, and magnetic properties. Dalton Trans. 2014, 43, 2234−2243. (b) Han, T.; Shi, W.; Niu, Z.; Na, B.; Cheng, P. Magnetic

featuring alternate high-and low-spin manganese (III) porphyrins. Chem. Commun. 2014, 50, 2120−2122. (9) (a) Wu, Y. L.; Guo, F. S.; Yang, G. P.; Wang, L.; Jin, J. C.; Zhou, X.; Zhang, W. Y.; Wang, Y. Y. Two Isostructural Metal−Organic Frameworks Directed by the Different Center Metal Ions, Exhibiting the Ferrimagnetic Behavior and Slow Magnetic Relaxation. Inorg. Chem. 2016, 55, 6592−6596. (b) Liu, T. F.; Fu, D.; Gao, S.; Zhang, Y. Z.; Sun, H. L.; Su, G.; Liu, Y. J. An azide-bridged homospin singlechain magnet:[Co(2,2′-bithiazoline)(N3)2]n. J. Am. Chem. Soc. 2003, 125, 13976−13977. (c) Chen, M.; Zhao, H.; Sanudo, E. C.; Liu, C. S.; Du, M. Two Isostructural Coordination Polymers Showing Diverse Magnetic Behaviors: Weak Coupling (NiII) and an Ordered Array of Single-Chain Magnets (CoII). Inorg. Chem. 2016, 55, 3715−3717. (d) Zhang, X. M.; Wang, Y. Q.; Wang, K.; Gao, E. Q.; Liu, C. M. Metamagnetism and slow magnetic dynamics in an antiferromagnet composed of cobalt(II) chains with mixed azide−carboxylate bridges. Chem. Commun. 2011, 47, 1815−1817. (e) Su, L.; Song, W. C.; Zhao, J. P.; Liu, F. C. Crystal engineering to control the magnetic interaction between weak ferromagnetic single-chain magnets assembled in a 3D framework. Chem. Commun. 2016, 52, 8722−8725. (f) Zeng, M. H.; Yin, Z.; Tan, Y. X.; Zhang, W. X.; He, Y. P.; Kurmoo, M. Nanoporous cobalt (II) MOF exhibiting four magnetic ground states and changes in gas sorption upon post-synthetic modification. J. Am. Chem. Soc. 2014, 136, 4680−4688. (g) Li, X. B.; Zhang, J. Y.; Wang, Y. Q.; Song, Y.; Gao, E. Q. Tricomponent Azide, Tetrazolate, and Carboxylate Cobridging Magnetic Systems: Ferromagnetic Coupling, Metamagnetism, and Single-Chain Magnetism. Chem. - Eur. J. 2011, 17, 13883− 13891. (10) (a) Zheng, Y. Z.; Lan, Y.; Wernsdorfer, W.; Anson, C. E.; Powell, A. K. Polymerisation of the Dysprosium Acetate Dimer Switches on Single-Chain Magnetism. Chem. - Eur. J. 2009, 15, 12566−12570. (b) Bartolomé, E.; Bartolomé, J.; Arauzo, A.; Luzón, J.; Badía, L.; Cases, R.; Luis, F.; Melnic, S.; Prodius, D.; Shova, S.; Turta, C. Antiferromagnetic single-chain magnet slow relaxation in the {Tb(α-fur)3}n polymer with non-Kramers ions. J. Mater. Chem. C 2016, 4, 5038−5050. (11) Visinescu, D.; Madalan, A. M.; Andruh, M.; Duhayon, C.; Sutter, J. P.; Ungur, L.; Van den Heuvel, W.; Chibotaru, L. F. First Heterotrimetallic {3d-4d-4f} Single Chain Magnet, Constructed from Anisotropic High-Spin Heterometallic Nodes and Paramagnetic Spacers. Chem. - Eur. J. 2009, 15, 11808−11814. (12) Wang, Z. X.; Zhang, X.; Zhang, Y. Z.; Li, M. X.; Zhao, H. H.; Andruh, M.; Dunbar, K. R. Single-Chain Magnetic Behavior in a Hetero-Tri-Spin Complex Mediated by Supramolecular Interactions with TCNQF.− Radicals. Angew. Chem., Int. Ed. 2014, 53, 11567− 11570. (13) (a) Zhu, M.; Mei, X. L.; Ma, Y.; Li, L. C.; Liao, D. Z.; Sutter, J. P. Nitronyl nitroxide−metal complexes as metallo-ligands for the construction of hetero-tri-spin (2p−3d−4f) chains. Chem. Commun. 2014, 50, 1906−1908. (b) Zhu, M.; Hu, P.; Li, Y. G.; Wang, X. F.; Li, L. C.; Liao, D. Z.; Durga Prasad Goli, V. M. L.; Ramasesha, S.; Sutter, J. P. Hetero-tri-spin [2p-3d-4f] Chain Compounds Based on Nitronyl Nitroxide Lanthanide Metallo-Ligands: Synthesis, Structure, and Magnetic Properties. Chem. - Eur. J. 2014, 20, 13356−13365. (c) Wang, X. F.; Li, C.; Sun, J.; Li, L. C. Nitronyl nitroxide based 2p−3d−4f chains with the magnetocaloric effect and slow magnetic relaxation. Dalton Trans. 2015, 44, 18411−18417. (d) Yang, M.; Sun, J.; Guo, J. N.; Sun, G. F.; Li, L. C. Cu−Ln compounds based on nitronyl nitroxide radicals: synthesis, structure, and magnetic and fluorescence properties. CrystEngComm 2016, 18, 9345−9356. (14) (a) Zhu, M.; Li, C.; Wang, X. F.; Li, L. C.; Sutter, J. P. Thermal Magnetic Hysteresis in a Cu-Gd-Radical Chain Compound. Inorg. Chem. 2016, 55, 2676−2678. (b) Wang, X. F.; Hu, P.; Li, L. C.; Sutter, J. P. [(Cu-Radical)2-Ln]: Structure and Magnetic Properties of Hetero-tri-spin Chains of Rings (Ln = YIII, GdIII, TbIII, DyIII). Inorg. Chem. 2015, 54, 9664−9669. (15) Ullman, E. F.; Osiecki, J. H.; Boocock, D.; Darcy, R. Stable free radicals. X. Nitronyl nitroxide monoradicals and biradicals as possible small molecule spin labels. J. Am. Chem. Soc. 1972, 94, 7049−7059. 13489


Article

Inorganic Chemistry blocking from exchange interactions: Slow relaxation of the magnetization and hysteresis loop observed in a dysprosium−nitronyl nitroxide chain compound with an antiferromagnetic ground state. Chem. - Eur. J. 2013, 19, 994−1001. (28) Guo, Y. N.; Xu, G. F.; Guo, Y.; Tang, J. K. Relaxation dynamics of dysprosium (III) single molecule magnets. Dalton Trans. 2011, 40, 9953−9963. (29) (a) Guo, Y. N.; Xu, G. F.; Wernsdorfer, W.; Ungur, L.; Guo, Y.; Tang, J. K.; Zhang, H. J.; Chibotaru, L. F.; Powell, A. K. Strong axiality and Ising exchange interaction suppress zero-field tunneling of magnetization of an asymmetric Dy2 single-molecule magnet. J. Am. Chem. Soc. 2011, 133, 11948−11951. (b) Guo, Y. N.; Xu, G. F.; Gamez, P.; Zhao, L.; Lin, S. Y.; Deng, J. K.; Tang, J. K.; Zhang, H. J. Two-step relaxation in a linear tetranuclear dysprosium (III) aggregate showing single-molecule magnet behavior. J. Am. Chem. Soc. 2010, 132, 8538−8539. (c) Lin, P. H.; Burchell, T. J.; Ungur, L.; Chibotaru, L. F.; Wernsdorfer, W.; Murugesu, M. A Polynuclear Lanthanide Single-Molecule Magnet with a Record Anisotropic Barrier. Angew. Chem., Int. Ed. 2009, 48, 9489−9492. (30) (a) Jiang, S. D.; Wang, B. W.; Sun, H. L.; Wang, Z. M.; Gao, S. An organometallic single-ion magnet. J. Am. Chem. Soc. 2011, 133, 4730−4733. (b) Jeletic, M.; Lin, P. H.; Le Roy, J. J.; Korobkov, I.; Gorelsky, S. I.; Murugesu, M. An organometallic sandwich lanthanide single-ion magnet with an unusual multiple relaxation mechanism. J. Am. Chem. Soc. 2011, 133, 19286−19289. (c) Car, P. E.; Perfetti, M.; Mannini, M.; Favre, A.; Caneschi, A.; Sessoli, R. Giant field dependence of the low temperature relaxation of the magnetization in a dysprosium (III)−DOTA complex. Chem. Commun. 2011, 47, 3751−3753. (d) Jiang, S. D.; Wang, B. W.; Su, G.; Wang, Z. M.; Gao, S. A Mononuclear Dysprosium Complex Featuring Single-MoleculeMagnet Behavior. Angew. Chem., Int. Ed. 2010, 49, 7448−7451. (31) (a) Miklovič, J.; Valigura, D.; Boča, R.; Titiš, J. A mononuclear Ni(II) complex: a field induced single-molecule magnet showing two slow relaxation processes. Dalton Trans. 2015, 44, 12484−12487. (b) Rajnák, C.; Titiš, J.; Fuhr, O.; Ruben, M.; Boča, R. Single-Molecule Magnetism in a Pentacoordinate Cobalt(II) Complex Supported by an Antenna Ligand. Inorg. Chem. 2014, 53, 8200−8202. (c) Boča, R.; Stolárová, M.; Falvello, L. R.; Tomás, M.; Titiš, J.; Č ernák, J. Slow magnetic relaxations in a ladder-type Dy(III) complex and its dinuclear analogue. Dalton Trans. 2017, 46, 5344−5351. (32) Cole, K. S.; Cole, R. H. Dispersion and absorption in dielectrics I. Alternating current characteristics. J. Chem. Phys. 1941, 9, 341−351.

13490


Slow Magnetic Relaxation in Ladder-Type and ... - ACS Publications

Recommend Documents