English

• 0   Introduction

  Single-molecule magnets (SMMs) have attracted many scientists attention in the past two decades^[1-4]. This type of materials are characterized as slow magnetization relaxation caused by the association of large ground state spin (S_T) value with a significant uniaxial (Ising-like) magnetic anisotropy (D), which leads to a significant energy barrier to magnetization reversal (U)^[5-7]. The SMMs have been found potential applications for the uses of high-density magnetic memories, magnetic refrigeration, quantum computing devices and spintronics at the molecular level^[8-11]. Recently 4f metal ions were considered to be good candidates for the construction of SMMs due to their significant magnetic anisotropy arising from the large, unquenched orbital angular momentum. Up to now, a variety of 4f metal ions based SMMs have been reported^[12-17].

  Apart from the choice of the metal ions, the ligand design also plays an important role. The use of organic radical ligands in the creation of new magnetic molecular compounds have attracted much attention since the discovery of the first radical-4f SMM by Gatteschis group^[18]. As is well known, the stable radical ligands can generate typically stronger intramolecular magnetic exchange coupling. The strong exchange coupling between lanthanides and radicals generally leads to superior SMMs. Recently, a binuclear Tb (Ⅲ) complex bridged by a N₂^3- radical has been reported with a record blocking temperature of 13.9 K^[19-20]. So far various organic radicals such as nitronyl nitroxide, verdazyl and semiquinone radicals have been reported^[21-25]. However, researches are focused in particular on the nitronyl nitroxide (NIT) family of radicals, because these type of radicals are relatively stable and easy to obtain derivatives with substituents containing donor atoms. Nitronyl nitroxide radicals can act as bidentate ligands through their identical N-O coordination groups and give rise to complexes with different structures. Unfortunately, NIT radicals are poorly donating ligands, thus utilization of strong electron-withdrawing coligands such as hexafluoroace-tylacetonate (hfac) and trifluoroacetylacetonate (tfac) are necessary. However, the steric demand of these coligands restrict the dimensionality of the resulting metal-radical compounds. So, it is easier to get zero-and one-dimensional compounds by this strategy.

  To further study the magnetic properties of NIT radical-lanthanide compounds, in this paper we report a novel nitronyl nitroxide radical (Scheme 1) and its corresponding Ln-nitronyl nitroxide compounds Ln (hfac)₃(NIT-Ph-4-OCHCH₃CH₃)₂(Ln=Gd (1), Tb (2), Dy (3); hfac=hexafluoroacetylacetonate; NIT-Ph-4-OCHCH₃CH₃=2-(4-isopropoxyphenyl)-4, 4, 5, 5-tetramet-hyl-imidazoline-1-oxyl-3-oxide), their crystal structures and magnetic properties were described in detail.

  Figure Scheme 1.  Molecule structure of NIT-Ph-4-OCHCH₃CH₃

  图选项

  下载全尺寸图像

  下载幻灯片

  1   Experimental

  1.1   Materials and physical measurements

  All the starting chemicals were obtained from Aldrich and used without further purification. The radical ligand NIT-Ph-4-OCHCH₃CH₃ was prepared according to literature method^[26]. Elemental analyses (C, H, N) were determined by Perkin-Elmer 240 elemental analyzer. The infrared spectra was recorded from KBr pellets in the range of 4 000~400 cm^-1 with a Bruker Tensor 27 IR spectrometer. The magnetic measurements were carried out with MPMSXL-7 SQUID magnetometer. Diamagnetic corrections were made with Pascals constants for all the constituent atoms.

  1.2   Synthesis of Complex 1

  A solution of Gd (hfac)₃·2H₂O (0.05 mmol) in 25 mL dry heptane was heated to reflux for 2 h. Then the solution was cooled to about 60 ℃, a solution of NIT-Ph-4-OCHCH₃CH₃ (0.1 mmol) in 2 mL of CH₂Cl₂ was added. The resulting solution was stirred for about 3 min and then cooled to room temperature. The filtrate was allowed to stand at room temperature for slow evaporation. After three days, some blue crystals were collected. Yield: 31.4 mg (45.5% based on Gd). Elemental analysis calculated for C₄₇H₄₉F₁₈N₄O₁₂Gd (%): C: 41.47; H: 3.63; N: 4.12. Found (%): C: 41.88; H: 3.69; N: 4.22.

  1.3   Synthesis of Complex 2

  Complex 2 was synthesized with the same procedure for complex 1 using Tb (hfac)₃·2H₂O instead of Gd (hfac)₃·2H₂O. Yield: 32.7 mg (47.9%). Elemental analysis calculated for C₄₇H₄₉F₁₈N₄O₁₂Tb (%): C: 41.42; H: 3.62; N: 4.11. Found (%): C: 40.69; H: 3.57; N: 4.22.

  1.4   Synthesis of Complex 3

  Complex 3 was synthesized with the same procedure for complex 1 using Dy (hfac)₃·2H₂O instead of Gd (hfac)₃·2H₂O. Yield: 29.3 mg (42.9%). Elemental analysis calculated for C₄₇H₄₉F₁₈N₄O₁₂Dy (%): C: 41.31; H: 3.61; N: 4.10. Found (%): C: 40.91; H: 3.77; N: 4.17.

  1.5   Crystal Structure Determination and Refine-ment

  X-ray single-crystal diffraction data for complexes 1, 2 and 3 were collected using a Rigaku Saturn CCD diffractometer at 113(2) K with Mo Kα radiation (λ=0.071 073 nm). The structure was solved by direct methods by utilizing the program SHELXS-97^[27] and refined by full-matrix least-squares methods on F² with the use of the SHELXL-97 program package^[28]. Anisotropic thermal parameters were assigned to all non-hydrogen atoms. The hydrogen atoms were set in calculated positions and refined as riding atoms with a common fixed isotropic thermal parameter. Disordered carbon atoms were observed in the hfac ligands for both compounds and disorders were also observed for some fluorine atoms. Pertinent crystallographic data and structure refinement parameters for these complexes were listed in Table 1. Selected bond lengths and bond angles of complexes 1, 2 and 3 are listed in Table 2.

  Table 1.  Crystal data and structure refinement for 1, 2 and 3

  表选项

  导出Excel

  下载全尺寸表图像

  Complex	1	2	3
  Empirical formula	C47H49F18Gd1N4O12	C47H49F18Tb1N4O12	C47H49F18Dy1N4O12
  Formula weight	1 361.15	1 362.82	1 366.40
  Crystal system	Triclinic	Monoclinic	Triclinic
  Space group	P1	P21/c	P1
  a/nm	1.219 5(6)	1.987 2(4)	1.214 6(10)
  b/nm	1.491 9(7)	1.255 6(3)	1.489 1(12)
  c/nm	1.738 6(7)	2.282 1(5)	1.727 6(13)
  α/(°)	98.890(5)	90	98.842(6)
  β/(°)	103.057(5)	98.865(5)	102.753(6)
  γ/(°)	111.943(3)	90	111.987(14)
  V/nm3	2.756(2)	2.731(4)	2.728(4)
  Z	2	4	2
  Dc/(g•cm-3)	1.64	1.609	1.664
  μ/mm-1	1.325	1.377	1.493
  Rint	0.062 2	0.073 6	0.027 2
  F (000)	1 362	2 728	1 366
  Reflections collected	22 857	46 848	23 418
  Independent reflections	9 649	9 876	9 822
  GOF on F2	1.017	1.032	1.021
  R1a [I > 2σ(I)]	0.026 8	0.053 2	0.037 8
  wR2b [I > 2σ(I)]	0.062 5	0.144 5	0.091 1
  aR1=Σ(‖Fo|-|Fc‖)/Σ|Fo|; bwR2=[Σw (Fo2-Fc2)2/Σw (Fo)2]1/2.

  Table 2.  Selected bond distances (nm) and Angles (°) for 1, 2 and 3

  表选项

  导出Excel

  下载全尺寸表图像

  1
  Gd (1)-O (6)	0.233 0(8)	Gd (1)-O (7)	0.233 3(8)	O (2)-N (l)	0.127 1(3)
  Gd (1)-O (3)	0.234 5(7)	Gd (1)-O (9)	0.235 0(8)	O (6)-N (3)	0.130 7(3)
  Gd (1)-O (8)	0.252 9(8)	Gd⑴-O (12)	0.239 97(18)	O (3)-N (2)	0.130 4(2)
  O (6)-Gd (1)-O (7)	93.24(7)	O (7)-Gd (1)-O (3)	105.83(7)	O (11)-Gd (1)-O (9)	148.80(6)
  O (6)-Gd (1)-O (11)	102.93(7)	O (11)-Gd (1)-O (3)	88.67(7)	O (3)-Gd (1)-O (9)	73.27(6)
  0(7)-Gd (l)-0(ll)	l36.79(6)	0(6)-Gd (l)-0(9)	76.52(6)	0(6)-Gd (l)-0(l0)	69.66(7)
  0(6)-Gd (l)-0(3)	l37.62(6)	0(7)-Gd (l)-0(9)	73.74(6)	0(7)-Gd (l)-0(l0)	l45.23(6)
  0(ll)-Gd (l)-0(l0)	77.69(6)	0(3)-Gd (l)-0(l0)	73.46(6)
  2
  Tb (l)-0(4)	0.234 0(3)	Tb (l)-0(ll)	0.236 0(3)	0(5)-N (4)	0.l27 4(5)
  Tb (l)-0(2)	0.234 5(3)	Tb (l)-0(8)	0.237 4(3)	0(2)-N (2)	0.l3l 7(5)
  Tb (l)-0(7)	0.234 6(3)	Tb (l)-0(l2)	0.238 l (4)	N (3)-0(4)	0.l3l 7(5)
  0(4)-Tb (l)-0(2)	l37.l0(l2)	0(2)-Tb (l)-0(ll)	l03.35(l2)	0(7)-Tb (l)-0(8)	72.69(l3)
  0(4)-Tb (l)-0(7)	l03.62(l3)	0(7)-Tb (l)-0(ll)	l37.94(l2)	0(ll)-Tb (l)-0(8)	74.0l (l2)
  0(2)-Tb (l)-0(7)	90.96(l3)	0(4)-Tb (l)-0(8)	75.98(l2)	0(4)-Tb (l)-0(l2)	l49.6l (l2)
  0(4)-Tb (l)-0(ll)	92.38(l3)	0(2)-Tb (l)-0(8)	l46.60(l2)	0(2)-Tb (l)-0(l2)	73.00(l2)
  0(7)-Tb (l)-0(l2)	74.68(l3)	0(ll)-Tb (l)-0(l2)	72.28(l3)
  3
  Dy (l)-0(2)	0.232 l (3)	Dy (l)-0(8)	0.235 0(3)	0(4)-N (4)	0.l26 9(4)
  Dy (l)-0(9)	0.233 5(3)	Dy (l)-0(ll)	0.235 l (3)	0(5)-N (3)	0.l29 7(4)
  Dy (l)-0(l2)	0.234 6(3)	Dy (l)-0(5)	0.235 4(3)	0(2)-N (2)	0.l30 4(5)
  0(2)-Dy (l)-0(9)	92.77(ll)	0(9)-Dy (l)-0(8)	l36.97(ll)	0(l2)-Dy (l)-0(ll)	74.09(ll)
  0(2)-Dy (l)-0(l2)	69.99(l2)	0(l2)-Dy (l)-0(8)	76.9l (l2)	0(8)-Dy (l)-0(ll)	l49.09(ll)
  0(9)-Dy (l)-0(l2)	l45.80(ll)	0(2)-Dy (l)-0(ll)	76.58(l2)	0(2)-Dy (l)-0(5)	l37.83(ll)
  0(2)-Dy (l)-0(8)	l03.30(l2)	0(9)-Dy (l)-0(ll)	73.22(ll)	0(9)-Dy (l)-0(5)	l05.9l (l2)
  0(l2)-Dy (l)-0(5)	73.72(ll)	0(8)-Dy (l)-0(5)	88.47(l2)

  CCDC: 985443, 1; 1043098, 2; 985444, 3.

  2   Results and discussion

  2.1   Crystal Structure of Complex 1

  Single-crystal X-ray diffraction analyses reveal that all these three compounds show similar radical-Ln (Ⅲ)-radical structures, which are composed of one Ln (hfac)₃ unit and two NIT-Ph-4-OCHCH₃CH₃ radicals. Compounds 1 and 3 are isostructural and crystallize in the P1 space group, while compound 2 crystallizes in the P2₁/c space group.

  In complex 1, the central Gd (Ⅲ) ions are eight-coordinate with eight oxygen atoms. Two radical ligands bond to one Gd (Ⅲ) ion via the oxygen atoms of N-O coordination groups. The bond length of Gd (1)-O (6) is 0.234 8 nm while the bond length of Gd (1)-O (3) is 0.237 8 nm. The N (2)-O (3) and N (3)-O (6) bond lengths of nitronyl nitroxide radicals are 0.130 4 nm and 0.130 7 nm, respectively. The uncoordinated N (1)-O (2) and N (4)-O (5) bond lengths are 0.127 1 nm and 0.127 2 nm, respectively, which are comparable to those of reported tri-spin radical-Ln (Ⅲ)-radical complexes^[29-35]. The other six oxygen atoms are from three hfacs with the Gd-O bond lengths in the range of 0.236 0~0.242 9 nm. The nearest Gd…Gd distance between the adjacent molecules is 1.024 9 nm (Fig. 1).

  Figure 1.  Molecular structure (left) and crystal packing diagram of complex 1 (right)

  图选项

  下载全尺寸图像

  下载幻灯片

  2.2   Crystal structure of complex 2

  The crystal structure of complex 2 shows that the central Tb (Ⅲ) ions are eight-coordinated with eight oxygen atoms. Two radical ligands bond to one Tb (Ⅲ) ion via the oxygen atoms of N-O coordination groups. The bond length of Tb (1)-O (4) is 0.234 1 nm while the bond length of Tb (1)-O (2) is 0.234 5 nm. The N (3)-O (4) and N (2)-O (2) bond lengths of nitronyl nitroxide radicals are 0.131 6 nm and 0.131 8 nm respectively. The uncoordinated N (1)-O (1) and N (4)-O (5) bond lengths are 0.128 3 nm and 0.127 3 nm, respectively, which are comparable to those of reported tri-spin radical-Ln (Ⅲ)-radical complexes^[29-35]. The other six oxygen atoms are from three hfacs with the Tb-O bond lengths in the range of 0.234 6~0.241 7 nm. The nearest Tb…Tb distance between the adjacent molecules is 1.080 8 nm, which is a little bit longer than that for complex 1 (Fig. 2).

  Figure 2.  Molecular structure (left) and crystal packing diagram of complex 2 (right)

  图选项

  下载全尺寸图像

  下载幻灯片

  2.3   Crystal Structure of Complex 3

  Compound 3 is isostructural to compound 1 and the bond lengths of Dy-O are in the range of 0.232 1~0.239 3 nm, which are a little shorter than the bond lenths of Gd-O.

  2.4   Magnetic Properties of Complex 1

  Variable-temperature magnetic susceptibilities of complexes 1, 2, and 3 were measured from 300 to 2.0 K in an applied field of 1 kOe. The χ_MT vs T plot for 1 are shown in Fig. 3. At 300 K, the χ_MT value is 8.77 cm³·K·mol^-1, close to the theoretical value of 8.63 cm³·K·mol^-1 (Uncoupled one Gd (Ⅲ) ion, f⁷ electron configuration, χ_MT=7.88 cm³·K·mol^-1) plus two organic radicals (S=1/2, χ_MT=0.375 cm³·K·mol^-1)). Upon cooling, the χ_MT value of complex 1 increases steadily to a maximum of 10.04 cm³·K·mol^-1 at 15 K, afterward decreases to 9.28 cm³·K·mol^-1 at 2.0 K.

  Figure 3.  Temperature dependence of χ_MT for complex 1

  图选项

  下载全尺寸图像

  下载幻灯片

  As shown in Scheme 2, there are two kinds of magnetic interactions in this radical-Gd (Ⅲ)-radical complex at the same time. The first one is Gd (Ⅲ)-radical interaction and the second one is radical-radical interaction.

  Figure Scheme 2.  Model of intramolecular interactions

  图选项

  下载全尺寸图像

  下载幻灯片

  The magnetic interactions between Gd (Ⅲ) and the radicals can be described by isotropic exchange interaction. Thus the experimental data for complex 1 can be analyzed with an expression derived from a spin Hamiltonian. Considering the g value range of the radical and Gd (Ⅲ) ion, we assume that the radical and Gd (Ⅲ) ion have the same g value. Thus the variable-temperature magnetic susceptibility data for complex 1 can be analyzed by a theoretical expression (Eq.2) deduced from a spin Hamiltonian (Eq.1)^[30-35].

  The best fitting leads to g=2.00, J_Rad-Gd=2.57 cm^-1, J_Rad-Rad=-9.98 cm^-1 for complex 1. The positive value of J_Rad-Gd indicates that there is a weak ferromagnetic interaction between the Gd (Ⅲ) and the radicals in the molecule. The negative J_Rad-Rad indicates the antiferromagnetic interaction between the two intramolecular radicals. The obtained J value is comparable with the previously reported Gd^Ⅲ-radicals compounds^[30-35].

  2.5   Magnetic properties of complex 2

  While for complex 2 (Fig. 4), at 300 K, the χ_MT value is 13.08 cm³·K·mol^-1, close to the theoretical value 12.57 cm³·K·mol^-1 in uncoupled system of one Tb (Ⅲ) ion (f⁹ electron configuration, χ_MT=11.82 cm³·K·mol^-1) plus two organic radical (S=1/2, χ_MT=0.375 cm³·K·mol^-1). Upon cooling, the χ_MT value of complex 2 increases steadily to a maximum of 28.62 cm³·K·mol^-1 at 3.0 K, afterward the value decreases to 28.54 cm³·K·mol^-1 at 2.0 K. The increase of χ_MT suggests the presence of ferromagnetic interaction between the Tb (Ⅲ) and the organic radical. The decrease of χ_MT at low temperature indicates the antiferromagnetic interaction between the two intramolecular radicals. The magnetic properties of complex 2 are similar to those of previously reported^[29-35].

  Figure 4.  Temperature dependence of χ_MT for complex 2

  图选项

  下载全尺寸图像

  下载幻灯片

  Alternating current (ac) susceptibility measure-ments for complex 2 were carried out in low temperature regime under a zero dc field to investigate the dynamics of the magnetization. As shown in Fig. 5, there are no obvious frequency dependent out-of-phase signals. We do not think that complex 2 express SMM behavior at low temperature. This may due to the small energy barrier which could not prevent the inversion of spin.

  Figure 5.  Temperature dependence of the in-phase and out-of-phase components of ac susceptibility for 2 in zero dc field with an oscillation of 3.5 Oe

  图选项

  下载全尺寸图像

  下载幻灯片

  2.6   Magnetic properties of complex 3

  Complex 3 shows similar magnetic properties with complex 1 (Fig. 6). At 300 K, the χ_MT value is 15.01 cm³·K·mol^-1, close to the theoretical value of 14.92 cm³·K·mol^-1. Upon cooling, the χ_MT value of complex 3 increases steadily to a maximum of 19.79 cm³·K·mol^-1 at 15.4 K, afterward decreases to 16.97 cm³·K·mol^-1 at 2.0 K. The plot also suggests the presence of ferromagnetic interaction between the Dy (Ⅲ) and the coordinated N-O groups of the organic radicals and the antiferromagnetic interaction between the two intramolecular radicals.

  Figure 6.  Temperature dependence of χ_MT for complexes 3

  图选项

  下载全尺寸图像

  下载幻灯片

  Alternating current (ac) susceptibility measure-ments for complex 3 were also carried out in low temperature regime under a zero dc field. The result (Fig. 7) shows that there are no obvious frequency dependent out-of-phase signals. Like complex 2, complex 3 doesnt express SMMs behavior at low temperature.

  Figure 7.  Temperature dependence of the in-phase and out-of-phase components of ac susceptibility for 3 in zero dc field with an oscillation of 3.5 Oe

  图选项

  下载全尺寸图像

  下载幻灯片

  3   Conclusions

  A novel nitronyl nitroxide radical and its three corresponding mononuclear tri-spin compounds Ln (hfac)₃(NIT-Ph-4-OCHCH₃CH₃)₂ (Ln=Gd (1), Tb (2), Dy (3).) have been synthesized and characterized. The magnetic studies reveal that ferromagnetic interactions (between the intramolecular Ln and radical) and antiferromagnetic interactions (between the intramole-cular radicals) are coexist in these complexes. Complexes 2 and 3 do not have SMMs behavior at low temperature, this may due to the small energy barrier which could not prevent the inversion of spin.

• 1. [1]

     Kahn O. Molecular Magnetism. New York: Wiley-VCH, 1993.

  2. [2]

     Moller S, Perlov C, Jackson W, et al. Nature, 2003, 426:166-169 doi: 10.1038/nature02070

  3. [3]

     Kahn M L, Sutter J P, Golhen S, et al. J. Am. Chem. Soc., 2000, 122:3413-3421 doi: 10.1021/ja994175o

  4. [4]

     Zhang P, Guo Y N, Tang J K. Coord. Chem. Rev., 2013, 257: 1728-1737 doi: 10.1016/j.ccr.2013.01.012

  5. [5]

     Ruiz-Molina D, Mas-Torrent M, Gómez J, et al. Adv. Mater., 2003, 15:42-49 doi: 10.1002/(ISSN)1521-4095

  6. [6]

     Clemente-León M, Soyer H, Coronado E, et al. Angew. Chem. Int. Ed., 1998, 37:2842-2845 doi: 10.1002/(ISSN)1521-3773

  7. [7]

     Cornia A, Fabretti A C, Pacchioni M, L, et al. Angew. Chem. Int. Ed., 2003, 42:1645-1651 doi: 10.1002/anie.200350981

  8. [8]

     Gatteschi D, Caneschi A, Pardi L, et al. Science, 1994, 265: 1054-1058 doi: 10.1126/science.265.5175.1054

  9. [9]

     Bar A K, Pichon C, Gogoi N, et al. Chem. Commun., 2015, 51:3616-3619 doi: 10.1039/C4CC10182K

  10. [10]

      Liu R N, Li L C, Wang X L, et al. Chem. Commun., 2010, 46:2566-2570 doi: 10.1039/b918554b

  11. [11]

      Bogani L, Wernsdorfer W. Nat. Mater., 2008, 7:179-183 doi: 10.1038/nmat2133

  12. [12]

      Caneschi A, Gatteschi D, Lalioti N, et al. Angew. Chem. Int. Ed., 2001, 40:1760-1793 doi: 10.1002/(ISSN)1521-3773

  13. [13]

      Bogani L, Sangregorio C, Sessoli R, et al. Angew. Chem. Int. Ed., 2005, 44:5817-5821 doi: 10.1002/(ISSN)1521-3773

  14. [14]

      Bernot K, Luzon J, Bogani L, et al. J. Am. Chem. Soc., 2009, 131:5573-5579 doi: 10.1021/ja8100038

  15. [15]

      Liu J L, Wu J Y, Chen Y C, et al. Angew. Chem. Int. Ed., 2014, 53:12966-12970 doi: 10.1002/anie.201407799

  16. [16]

      Chatelain L, Walsh J P S, Pecaut J, et al. Angew. Chem. Int. Ed., 2014, 53:13434-13439 doi: 10.1002/anie.201407334

  17. [17]

      Zhang P, Zhang L, Wang C. J. Am. Chem. Soc., 2014, 136: 4484-4489 doi: 10.1021/ja500793x

  18. [18]

      Poneti G, Bernot K, Bogani L, et al. Chem. Commun., 2007 1807-1809

  19. [19]

      Rinehart J D, Fang M, Evans W J, et al. J. Am. Chem. Soc., 2011, 133:14236-14239 doi: 10.1021/ja206286h

  20. [20]

      Rinehart J D, Fang M, Evans W J, et al. Nat. Chem., 2011, 3:538-542 doi: 10.1038/nchem.1063

  21. [21]

      Chernick E T, Casillas R, Zirzlmeier J, et al. J. Am. Chem. Soc., 2015, 137:857-863 doi: 10.1021/ja510958k

  22. [22]

      Mailman A, Winter S M, Wong J W L, et al. J. Am. Chem. Soc., 2015, 137:1044-1049 doi: 10.1021/ja512235h

  23. [23]

      Wang X F, Hu P, Li Y G, et al. Chem. Asian J., 2015, 10: 325-330 doi: 10.1002/asia.v10.2

  24. [24]

      Zhu M, Hu P, Li Y, et al. Chem. Eur. J., 2014, 20:13356-13364 doi: 10.1002/chem.201403581

  25. [25]

      Wang Z X, Zhang X, Zhang Y Z, et al. Angew. Chem. Int. Ed., 2014, 53:11567-11570 doi: 10.1002/anie.201407628

  26. [26]

      Ullman E F, Osiecki J H, Boocock D G B, et al. J. Am. Chem. Soc., 1972, 94:7049-7059 doi: 10.1021/ja00775a031

  27. [27]

      Sheldrick G M. SHELXS-97: Program for the Solution of Crystal Structures, University of Göttingen, Germany, 1997. http://www.oalib.com/references/16733729

  28. [28]

      Sheldrick G M. SHELXL-97: Program for the Refinement of Crystal Structures, University of Göttingen, Germany, 1997. http://www.oalib.com/references/13283787

  29. [29]

      Hu P, Zhang C, Gao Y, et al. Inorg. Chim. Acta, 2013, 398: 136-140 doi: 10.1016/j.ica.2012.12.025

  30. [30]

      Zhou N, Ma Y, Wang C, et al. Dalton Trans., 2009:8489-8492

  31. [31]

      Wang C, Wang Y L, Qin Z X, et al. Inorg. Chem. Commun., 2012, 20:112-117 doi: 10.1016/j.inoche.2012.02.030

  32. [32]

      Zhang C X, Chen H W, Wang W M, et al. Inorg. Chem. Commun., 2012, 24:177-181 doi: 10.1016/j.inoche.2012.07.003

  33. [33]

      Du F X, Hu P, Gao Y Y, et al. Inorg. Chem. Commun., 2014, 48:166-170 doi: 10.1016/j.inoche.2014.08.035

  34. [34]

      Zhang C X, Qiao X M, Kong Y K, et al. J. Mol. Struct., 2015, 108:1348-1354

  35. [35]

      Li L L, Liu S, Zhang Y, et al. Dalton Trans., 2015, 44:6118-6125 doi: 10.1039/C4DT03941F

• 

  Scheme 1  Molecule structure of NIT-Ph-4-OCHCH₃CH₃

  下载: 全尺寸图片 幻灯片
  

  Figure 1  Molecular structure (left) and crystal packing diagram of complex 1 (right)

  Thermal ellipsoids are drawn at 30% probability; All hydrogen atoms and fluorine atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Molecular structure (left) and crystal packing diagram of complex 2 (right)

  Thermal ellipsoids are drawn at 30% probability; All hydrogen atoms and fluorine atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 3  Temperature dependence of χ_MT for complex 1

  The solid lines represent the theoretical values based on the corresponding equations

  下载: 全尺寸图片 幻灯片
  

  Scheme 2  Model of intramolecular interactions

  下载: 全尺寸图片 幻灯片
  

  Figure 4  Temperature dependence of χ_MT for complex 2

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Temperature dependence of the in-phase and out-of-phase components of ac susceptibility for 2 in zero dc field with an oscillation of 3.5 Oe

  下载: 全尺寸图片 幻灯片
  

  Figure 6  Temperature dependence of χ_MT for complexes 3

  下载: 全尺寸图片 幻灯片
  

  Figure 7  Temperature dependence of the in-phase and out-of-phase components of ac susceptibility for 3 in zero dc field with an oscillation of 3.5 Oe

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystal data and structure refinement for 1, 2 and 3

  Complex	1	2	3
  Empirical formula	C47H49F18Gd1N4O12	C47H49F18Tb1N4O12	C47H49F18Dy1N4O12
  Formula weight	1 361.15	1 362.82	1 366.40
  Crystal system	Triclinic	Monoclinic	Triclinic
  Space group	P1	P21/c	P1
  a/nm	1.219 5(6)	1.987 2(4)	1.214 6(10)
  b/nm	1.491 9(7)	1.255 6(3)	1.489 1(12)
  c/nm	1.738 6(7)	2.282 1(5)	1.727 6(13)
  α/(°)	98.890(5)	90	98.842(6)
  β/(°)	103.057(5)	98.865(5)	102.753(6)
  γ/(°)	111.943(3)	90	111.987(14)
  V/nm3	2.756(2)	2.731(4)	2.728(4)
  Z	2	4	2
  Dc/(g•cm-3)	1.64	1.609	1.664
  μ/mm-1	1.325	1.377	1.493
  Rint	0.062 2	0.073 6	0.027 2
  F (000)	1 362	2 728	1 366
  Reflections collected	22 857	46 848	23 418
  Independent reflections	9 649	9 876	9 822
  GOF on F2	1.017	1.032	1.021
  R1a [I > 2σ(I)]	0.026 8	0.053 2	0.037 8
  wR2b [I > 2σ(I)]	0.062 5	0.144 5	0.091 1
  aR1=Σ(‖Fo|-|Fc‖)/Σ|Fo|; bwR2=[Σw (Fo2-Fc2)2/Σw (Fo)2]1/2.

  下载: 导出CSV

  Table 2.  Selected bond distances (nm) and Angles (°) for 1, 2 and 3

  1
  Gd (1)-O (6)	0.233 0(8)	Gd (1)-O (7)	0.233 3(8)	O (2)-N (l)	0.127 1(3)
  Gd (1)-O (3)	0.234 5(7)	Gd (1)-O (9)	0.235 0(8)	O (6)-N (3)	0.130 7(3)
  Gd (1)-O (8)	0.252 9(8)	Gd⑴-O (12)	0.239 97(18)	O (3)-N (2)	0.130 4(2)
  O (6)-Gd (1)-O (7)	93.24(7)	O (7)-Gd (1)-O (3)	105.83(7)	O (11)-Gd (1)-O (9)	148.80(6)
  O (6)-Gd (1)-O (11)	102.93(7)	O (11)-Gd (1)-O (3)	88.67(7)	O (3)-Gd (1)-O (9)	73.27(6)
  0(7)-Gd (l)-0(ll)	l36.79(6)	0(6)-Gd (l)-0(9)	76.52(6)	0(6)-Gd (l)-0(l0)	69.66(7)
  0(6)-Gd (l)-0(3)	l37.62(6)	0(7)-Gd (l)-0(9)	73.74(6)	0(7)-Gd (l)-0(l0)	l45.23(6)
  0(ll)-Gd (l)-0(l0)	77.69(6)	0(3)-Gd (l)-0(l0)	73.46(6)
  2
  Tb (l)-0(4)	0.234 0(3)	Tb (l)-0(ll)	0.236 0(3)	0(5)-N (4)	0.l27 4(5)
  Tb (l)-0(2)	0.234 5(3)	Tb (l)-0(8)	0.237 4(3)	0(2)-N (2)	0.l3l 7(5)
  Tb (l)-0(7)	0.234 6(3)	Tb (l)-0(l2)	0.238 l (4)	N (3)-0(4)	0.l3l 7(5)
  0(4)-Tb (l)-0(2)	l37.l0(l2)	0(2)-Tb (l)-0(ll)	l03.35(l2)	0(7)-Tb (l)-0(8)	72.69(l3)
  0(4)-Tb (l)-0(7)	l03.62(l3)	0(7)-Tb (l)-0(ll)	l37.94(l2)	0(ll)-Tb (l)-0(8)	74.0l (l2)
  0(2)-Tb (l)-0(7)	90.96(l3)	0(4)-Tb (l)-0(8)	75.98(l2)	0(4)-Tb (l)-0(l2)	l49.6l (l2)
  0(4)-Tb (l)-0(ll)	92.38(l3)	0(2)-Tb (l)-0(8)	l46.60(l2)	0(2)-Tb (l)-0(l2)	73.00(l2)
  0(7)-Tb (l)-0(l2)	74.68(l3)	0(ll)-Tb (l)-0(l2)	72.28(l3)
  3
  Dy (l)-0(2)	0.232 l (3)	Dy (l)-0(8)	0.235 0(3)	0(4)-N (4)	0.l26 9(4)
  Dy (l)-0(9)	0.233 5(3)	Dy (l)-0(ll)	0.235 l (3)	0(5)-N (3)	0.l29 7(4)
  Dy (l)-0(l2)	0.234 6(3)	Dy (l)-0(5)	0.235 4(3)	0(2)-N (2)	0.l30 4(5)
  0(2)-Dy (l)-0(9)	92.77(ll)	0(9)-Dy (l)-0(8)	l36.97(ll)	0(l2)-Dy (l)-0(ll)	74.09(ll)
  0(2)-Dy (l)-0(l2)	69.99(l2)	0(l2)-Dy (l)-0(8)	76.9l (l2)	0(8)-Dy (l)-0(ll)	l49.09(ll)
  0(9)-Dy (l)-0(l2)	l45.80(ll)	0(2)-Dy (l)-0(ll)	76.58(l2)	0(2)-Dy (l)-0(5)	l37.83(ll)
  0(2)-Dy (l)-0(8)	l03.30(l2)	0(9)-Dy (l)-0(ll)	73.22(ll)	0(9)-Dy (l)-0(5)	l05.9l (l2)
  0(l2)-Dy (l)-0(5)	73.72(ll)	0(8)-Dy (l)-0(5)	88.47(l2)

  下载: 导出CSV
•