Materials
All chemicals were commercially available and were used as received. All the solvents were dehydrated and deoxygenated by Solvent Purification Systems prior to use. All manipulations were performed under a dry and oxygen-free argon atmosphere by using Schlenk techniques or in a glovebox.
Syntheses
For [Dy(1-AdO)2(py)5][BPh4] (1)
In an argon glovebox, reactants of DyCl3 (0.5 mmol, 134 mg), 1-AdOH (1mmol, 156 mg) and NaBPh4 (0.5 mmol, 171 mg) are added into about 8 mL THF in Schlenk tube and a cloudy solution forms. After stirring for 12 h at 85℃ oil bath, the cloudy solution is filtrated and the solvent of the filtrate is removed by vacuum to get a white powder of the solids. Then 2 mL pyridine is used to dissolve the white powders and filtrated the solution. Crystals suitable for X-ray diffraction are grown by slow diffusion of hexane to the saturated pyridine solution of 1 at room temperature for three days. Yield 226 mg, 36% (based on Dy). Elemental analysis calcd (%) for C74H81N6O2DyB: C 70.49, H 6.43, N 6.67; found: C 70.46, H 6.41, N 6.65. IR spectra (cm−1): 2,905 s, 2,808 m, 2,716 w, 1,697 m, 1,568 m, 1,420 s, 1,120 s, 1,025 s, 1,002 m, 916 m, 743 m, 721 s, 687 s, 623 m, 521 w.
For [Dy(2-AdO)2(py)5][BPh4] (2)
The similar procedure as 1 is used to synthesize 2 with 1-AdOH replaced by 2-AdOH (1mmol,156mg). Yield 228mg, 35% (based on Dy). Elemental analysis calcd (%) for C77H88N6O2DyB: C 70.96, H 6.68, N 6.45; found: C 70.94, H 6.65, N 6.43. IR spectra (cm−1): 2,907 s, 2,809 m, 2,718 w, 1,695 m, 1,564 m, 1,418 s, 1,123 s, 1,027 s, 1,004 m, 918 m, 745 m, 718 s, 683 s, 625 m, 518 w.
Solution preparation for 1s and 2s
125 mM solutions of 1 (1s) and 2 (2s) were prepared by dissolving block crystals of 1 (ca. 157mg) and 2 (ca. 163mg) in 1 mL pyridine, respectively, in an argon glovebox.
X-ray crystallography data
All data were recorded on a Bruker SMART CCD diffractometer with MoKα radiation (λ = 0.71073 Å). The structures were solved by direct methods and refined on F2 using SHELXTL. CCDC 2073309 (1) and 2073311 (2) contain the supplementary crystallographic data for this paper mainly including Table S1–S3. These datas can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (see Supplementary Materials).
Magnetic properties measurements
Magnetic susceptibility measurements have been carried out with a Quantum Design MPMS-XL7 SQUID magnetometer upon cooling from 300 to 2 K in variable applied fields. Ac susceptibility measurements have been performed at frequencies of between 1 and 1500 Hz with an oscillating field of 3.5 Oe and with variable dc applied field. Powder samples were embedded in eicosane to avoid any field induced crystal reorientation. Crystalline powders were fixed with eicosane, wrapped with film, and placed in the center of a straw. For the frozen solution sample 1s and 2s, a 125 mM pyridine solution of 1 and 2 were added into an NMR tube, which was sealed with paraffin, wrapped with Kapton tape, then the straw was put into magnetometer with the system temperature at 100 K in order to flash-freeze the solution. A diamagnetic correction has been calculated from Pascal constants and embedding eicosane has been applied to the observed magnetic susceptibility (see Supplementary Materials).
Electronic structure calculations
Ab initio calculations at SA-CASSCF/RASSI level were performed on program MOLCAS 8.0 and the structure was originally taken from the X-Ray structure. The basis sets were chosen from the ANO-RCC library as have been used in many works. The Dy atom was treated with VTZP quality, then the related B, C and O atoms with VDZP quality and others with VDZ quality. The state-averaged CASSCF orbitals of the sextets, quartets and doublets were optimized with 21, 224 and 490 states, respectively, with the RASSCF module. 21, 128 and 130 sextets, quartets and doublets chosen to construct and diagonalize in spin-orbit (SO) coupling Hamiltonian with the RASSI module. These computed SO states were written into the SINGLE_ANISO program to compute the g-tensors, crystal field parameters and magnetic energy levels for the doublets of the ground J = 15/2 multiple of the 6H15/2 term for Dy(III). The two electron integrals were Cholesky decomposed with a threshold of 1 × 10− 8 to account for the accuracy (see Supplementary Materials).
DFT calculations
In order to compare the molecular vibrations of distinctive compounds, we used Gaussian 09D to optimize their geometry and calculate their vibration frequencies. The element of dysprosium was substituted to yttrium to avoid convergence problem owing to the similar radius of their trivalent ions. Meanwhile, the atomic mass of yttrium was set as 162.5 (the natural abundance-weighted mass of dysprosium) to acquire more accurate harmonic vibrational modes. The geometry we used are from X-ray single crystal structure. The PBE density functional together with Grimme’s D3 dispersion correction was employed in all calculations. We applied the cc-pVDZ basis set for carbon, hydrogen, oxygen, nitrogen and boron atoms, while for yttrium, the Stuttgart RSC 1997 effective core potential (ECP) was employed for its 28 core electrons and the rest of valence electrons were expressed using corresponding valence basis set (see Supplementary Materials).