There is nothing wrong with being soft: using sulfur ligands to ...There is nothing wrong with being soft: using sulfur ligands to increase axiality in a Dy(III) Single-Ion Magnet†
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ELECTRONIC SUPPLEMENTARY INFORMATION
There is nothing wrong with being soft: using sulfur ligands to increase
axiality in a Dy(III) Single-Ion Magnet†
Angelos B. Canaj,a Sourav Dey,b Oscar Cespedes,c Claire Wilsona, Gopalan Rajaraman*b and Mark
Murrie*a
a School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK. E-mail:
[email protected] b Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra,
400076, India. E-mail: [email protected] c School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK.
Scheme S1. Synthesis of N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine, HLON3.
Synthetic strategy for 1:
A Schlenk flask containing N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-bis(2-
pyridylmethyl)amine (43 mg, 0.18 mmol) and Dy(CF3SO3)3 (55 mg, 0.09 mmol) was heated
under vacuum using a moderate Bunsen burner flame up to the point that the N-(3,5-di-tert-
butyl-2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine ligand (HLON3) was melted in the
presence of Dy(CF3SO3)3. The hot flask was allowed to reach room temperature under argon.
The brown precipitate was treated with 5 ml of dry THF. The clear brown solution formed was
stirred for 2h at room temperature. Evaporation of the brown THF solution under vacuum
afforded an oily precipitate. The precipitate was treated with 2 ml of anhydrous pyridine. The
clear brown pyridine solution was left stirring under argon for 24 h producing a yellow
precipitate. The precipitate was filtered and transferred into a Schlenk flask containing
diethyldithiocarbamic acid diethylammonium salt (28 mg, 0.125 mmol). 3 ml of dry THF was
added and the reaction was stirred at 45 °C for 1 h under argon. After 1 h the reaction was left
stirring until it reached room temperature. Single crystals of [DyIIILON3(C5H10NS2)2].0.5THF (1)
were isolated by slow diffusion of dry pentane into the THF solution.
Elemental Anal. calcd (found) for 1.0.3H2O: C 51.29 (51.33), H 6.45 (6.49), N 7.64 (7.68) %.
Crystallographic details
The structure of 1 was solved using ShelxT (SHELXT: Sheldrick, G. M. (2015). Acta Cryst. A71, 3-8.) and
refined using ShelXL (Sheldrick, G.M. (2015). Acta Cryst. C71, 3-8) within the program Olex2
(Dolomanov, O.V., Bourhis, L.J., Gildea, R.J, Howard, J.A.K. & Puschmann, H. (2009), J. Appl. Cryst. 42,
339-341). All non-hydrogen atoms were refined with anistropic atomic displacement parameters
(ADPs), except the partially occupied lattice THF molecule which was refined with isotropic adps.
Hydrogen atoms were placed in geometrically calculated positions and included as part of a riding
model or as a rigid rotor for Me groups. Disorder in one t-Butyl group was modelled with all Me
carbon over two partially occupied sites with occupancy 0.57:0.43 and a 0.5 occupied molecule of THF
was included with 3 atoms modelled over two 0.25 occupied sites, suitable distance restraints were
applied. Further details are given in the CI, deposited with the CCDC number 1950766 and the Table
below.
Table S1. Crystallographic data for complex 1.2
1
Formula C37H54DyN5OS4·0.5(C4H8O)
MW 911.64
Crystal System Monoclinic
Space group P21/c
a/Å 16.4260 (8)
b/Å 14.4027 (7)
c/Å 20.5958 (9)
α/o 90
β/o 111.107 (2)°
γ/o 90
V/Å3 4545.6 (4)
Z 4
T/K 150
λ/Å 0.71073
Dc/g cm-3 1.332
μ(Mo-Kα)/ mm-1 1.86
Meas./indep.(Rint) refl. 47454/10374 (0.024)
Obs. refl. [I>2σ(I)] 9509
wR(F2) 0.067
R[F2 > 2s(F2)] 0.023
S 1.04
Δρmax,min/ eÅ-3 0.85, -0.45
Table S2. Selected bond distances and angles for complex 1 (Å, º).2
Dy1—O1 2.1591 (16) Dy1—S1C 2.8133 (5)
Dy1—N1 2.5403 (18) Dy1—S2C 2.8567 (6)
Dy1—N2 2.5711 (17) Dy1—S3C 2.9647 (6)
Dy1—N3 2.5237 (18) Dy1—S4C 2.8407 (6)
O1—Dy1—N1 76.67 (6) N3—Dy1—S1C 143.51 (4)
O1—Dy1—N2 77.52 (6) N3—Dy1—S2C 85.22 (4)
O1—Dy1—N3 89.15 (6) N3—Dy1—S3C 73.91 (4)
O1—Dy1—S1C 102.04 (4) N3—Dy1—S4C 106.26 (5)
O1—Dy1—S2C 80.94 (4) S1C—Dy1—S2C 62.960 (16)
O1—Dy1—S3C 154.39 (5) S1C—Dy1—S3C 82.240(16)
O1—Dy1—S4C 144.43 (4) S1C—Dy1—S4C 84.570 (18)
N1—Dy1—N2 65.64 (6) S2C—Dy1—S3C 78.667 (17)
N1—Dy1—S1C 85.98 (4) S4C—Dy1—S2C 131.143 (18)
N1—Dy1—S2C 136.60 (4) S4C—Dy1—S3C 60.638 (16)
N1—Dy1—S3C 128.94 (4) N2—Dy1—S4C 80.37 (4)
N1—Dy1—S4C 68.90 (4) N3—Dy1—N1 130.51 (6)
N2—Dy1—S1C 151.11 (4) N3—Dy1—N2 65.04 (6)
N2—Dy1—S2C 143.14 (4) N2—Dy1—S3C 110.83 (4)
Fig. S1 Selected bond distances for complex 1 in Å.
Table S3. Shape measures of complex 1. The lowest CShMs value, is highlighted.3
Dy Symmetry Ideal polyhedron
OP-8 31.667 D8h Octagon
HPY-8 22.926 C7v Heptagonal pyramid
HBPY-8 17.490 D6h Hexagonal bipyramid
CU-8 12.071 Oh Cube
SAPR-8 2.803 D4d Square antiprism
TDD-8 2.790 D2d Triangular dodecahedron
JGBF-8 12.680 D2d Johnson gyrobifastigium J26
JETBPY-8 25.910 D3h Johnson elongated triangular bipyramid J14
JBTPR-8 2.950 C2v Biaugmented trigonal prism J50
BTPR-8 2.707 C2v Biaugmented trigonal prism
JSD-8 4.508 D2d Snub diphenoid J84
TT-8 12.546 Td Triakis tetrahedron
ETBPY-8 21.144 D3h Elongated trigonal bipyramid
Fig. S2 The powder X-ray diffraction pattern of 1 (Inset: diffraction of 1 from 5-300). The black line represents the simulated powder X-ray diffraction pattern generated from single-crystal data collected at 150 K, and the red line represents the experimental data measured at ambient temperature.
Fig. S3 Comparison of the calculated (with SHAPE3) and experimental biaugmented trigonal prism
coordination sphere for the Dy(III) ion in complex 1 . Dy, gold; N, dark blue; O, red; S, brown.
Fig. S4 (Upper) The crystal packing of 1 looking down the b axis, (Lower) with the shortest Dy···Dy
distance of 8.394 Å highlighted. Hydrogen atoms and disorder components are omitted for clarity. Dy,
yellow; N, dark blue; O, red; S, brown; C, grey.
3. Magnetic Properties
Fig. S5 χMT vs. T data for 1 in a field of 1000 Oe from 290 – 2 K. Inset: Magnetisation vs. Field
plot at temperatures 2, 4 and 6 K for 1 from 0.1-5 T.
Fig. S6 The Field cooled (FC) and Zero-Field cooled (ZFC) magnetic susceptibility of 1 at 1000 Oe.
Fig. S7 Powder magnetic hysteresis measurements for 1 at 2-8 K, with an average sweep rate of 20 mTs−1.
Fig. S8 Temperature dependence of the in-phase, χ′Μ (upper), and out-of-phase, χ″Μ (lower) ac
susceptibility, in zero dc field, for 1 with ac frequencies of 5−940 Hz.
Fig. S9 Frequency dependence of the in-phase ac susceptibility for 1 up to 40 K in zero dc field.
The solid lines correspond to the best fit.
Fig. S10 Frequency dependence of the out-of-phase ac susceptibility for 1 up to 40 K in zero dc
field. The solid lines correspond to the best fit.
Fig. S11 χ″Μ vs χ′Μ plot of the AC magnetic susceptibility of 1 in zero dc field. The solid lines
correspond to the best fit to Debye’s law.4
Fig. S12 Frequency dependence of the in-phase (upper) and out-of-phase (lower) susceptibility
at 15 K measured at different dc fields for complex 1. The solid lines correspond to the best fit.
(Upper Inset) Relaxation times (τ) as a function of the applied field (Oe) for 1, showing the
optimum dc field as 1200 Oe.
Fig. S13 Frequency dependence of the in-phase (upper) and out-of-phase (lower) susceptibility
at 30 K measured at different dc fields for complex 1. The solid lines correspond to the best fit.
(Upper Inset) Relaxation times (τ) as a function of the applied field (Oe) for 1, showing the
optimum dc field as 1200 Oe.
Fig. S14 Frequency dependence of the in-phase ac susceptibility for 1 up to 40 K under 1200
Oe dc field. The solid lines correspond to the best fit.
Fig. S15 Frequency dependence of the out-of-phase ac susceptibility for 1 up to 40 K under
1200 Oe dc field. The solid lines correspond to the best fit.
Fig. S16 χ″Μ vs χ′Μ plot of the AC magnetic susceptibility of 1 under 1200 Oe dc field. The solid
lines correspond to the best fit to Debye’s law.4
Fig. S17 Log-Log plot of the relaxation times, τ−1 versus T for 1 in zero dc field. The data were analysed
using the equation: τ−1= τQTM−1 + CTn + τ0
−1 exp(-Ueff/T). The best fit (red line) gives n = 3.24, C = 0.02
K−n s−1, τQTM = 0.017 s , τ0 = 2.99 x 10-12 s,5 and Ueff = 638 K.6
Fig. S18 Log-Log plot of the relaxation times, τ−1 versus T for 1 under 1200 dc field. The data were
analysed using the equation: τ−1= CTn + τ0−1 exp(-Ueff/T). The best fit (red line) gives n = 3.96, C =
3.95x10-5 K−n s−1, τ0 = 1.94 x 10-12 s,5 and Ueff = 656 K.6
4. Ab initio calculations
Computational Details:
To find the magnetic anisotropy of the metal centre in 1 and the model systems ab initio CASSCF+SO-RASSI calculations have been performed using the MOLCAS 8.2 7 program package on the X-ray crystal structures of 1. The relativistic effect of the Dy centre has been taken into account by the DKH Hamiltonian. Disk space for calculation of two-electron integrals has been reduced by the Cholesky decomposition technique.8 The basis set for all the atoms has been taken from the ANO-RCC library implemented in the MOLCAS 8.2 program package. The basis set of VTZP quality was used for Dy, O, N, S, Se, Te atoms. The basis set of VDZ quality was used for the C and H atoms. The active space for the Dy(III) ion contains nine electrons in seven orbitals; i.e. CAS (9.7). The sextet, quartet and doublet states of Dy(III) were optimised with 21, 224 and 490 roots respectively. The 21 sextets, 128 quartets and 130 doublets have been mixed via SO-RASSI to calculate the spin-orbit coupling of the Dy(III) center. Finally, the g tensors and blocking barriers were calculated using the SINGLE_ANISO program which uses the energy of the spin orbit states generated from RASSI-SO.9 The Dy-O/Se/Te and O/Se/Te-C distances in the first set of in silico models 1-O, 1-Se and 1-Te have been fixed from the literature values.10 The geometry optimization in the second set of in silico models (labeled Optimized model in Table S5) has been performed with the UB3LYP12 functional using Gaussian09.13 The Dy atom of 1 and its model systems has been substituted by Gd to simplify the calculation. We have used Ahlrichs split valence basis set (SVP) for C and H, triple-ξ plus polarization (TZVP) for O and N, triple-ξ basis set (TZV) for S,14 and LANL2DZ ECP with its corresponding basis set for Gd.15 We have also performed NBO11 analysis with the UB3LYP12 functional using the Gaussian0913 suite to investigate the covalency of 1 and the model systems.
It is important to note that optimization of the in silico models leads to a decrease in the Ucal values (see Table S5) as the effects of intermolecular interactions / crystal lattice effects are removed, leading to variations in the molecular structure.
In the following tables, the angle between the gzz axis of the ground and excited KDs are higher than ideal collinearity demands, however, it has been shown that inclusion of a dynamic correlation reduces this angle offering relatively a larger window for collinearity, as assumed here.16
Table S4. CASSCF+RASSI-SO computed relative energies of the eight low lying Kramers Doublets (KDs) along with g tensors and deviations from the principal magnetisation axis with respect to the first KD for complex 1. Ucal (K) is shown in bold.
E (K) gxx gyy gzz Angle (°) Composition of mJ levels
Table S5. CASSCF+RASSI-SO computed relative energies of the eight low lying Kramers Doublets (KDs) along with g tensors and deviations from the principal magnetisation axis with respect to the first KD for models 1-O, 1-Te and 1-Se respectively. Ucal (K) is shown in bold.
Model 1-O (changing axial S-atoms for O-atoms)
E (K) gxx gyy gzz Angle (°) Composition of mJ levels
Fig. S19 Ab initio SINGLE_ANISO computed ground state Kramers Doublet for complex 1. Colour code:
Dy, gold; O, red; N, blue; S, brown; C, grey; Hydrogens are omitted for clarity.
Fig. S20 LoProp charges of the atoms attached to the Dy(III) center for complex 1. Colour code: Dy,
gold; O, red; N, blue; S, brown; C, grey.
Fig. S21 Ab initio calculated relaxation dynamics for Models 1-O, 1-Te and 1-Se. The arrows show the
connected energy states with the number representing the matrix element of the transverse moment
(see text for details). Here, the black line indicates the KDs as function of magnetic moments. The red
dashed arrow represents QTM (QTM = quantum tunnelling of the magnetisation) via the ground state
and TA-QTM (TA-QTM = thermally assisted QTM) via excited states. The blue dashed arrow indicates
possible Orbach processes. The pink thick arrow indicates the mechanism of magnetic relaxation. The
numbers above each arrow represent corresponding transverse matrix elements for the transition
magnetic moments.
1-Te 1-Se
1-O
Fig. S22 Ab initio SINGLE_ANISO computed ground state Kramers Doublet for Models 1-O, 1-Te and 1-
Se. Colour code: Dy, gold; O, red; N, blue; Te, lavender; Se, blue-grey; C, grey.
1-Te 1-Se
1-O
Table S8. The composition of the co-ligand Gd-O/S/Se/Te bonds (Note that the Dy atom of 1 and its model systems has been substituted by Gd to simplify the calculations) as computed from natural bond orbital (NBO) analysis, confirming that the Ln-O bonds are strongly ionic and that the covalency increases significantly as we move from O to S, Se and Te.
Bond Contribution from the corresponding elements Gd-O67 0.93% Gd + 99.07% O Gd-O68 0.92% Gd + 99.08% O Gd-O69 0.41% Gd + 99.59% O Gd-O70 0.41% Gd + 99.59% O Gd-S67 13.69% Gd + 86.31% S Gd-S68 13.02% Gd + 86.98% S Gd-S69 11.34% Gd + 88.66% S Gd-S70 12.99% Gd + 87.01% S
Gd-Se67 15.00% Gd + 85.00% Se Gd-Se68 15.10% Gd + 84.90% Se Gd-Se69 15.90% Gd + 84.10% Se Gd-Se70 16.08% Gd + 83.92% Se Gd-Te67 18.39% Gd + 81.61% Te Gd-Te68 18.18% Gd+ 81.82% Te Gd-Te69 19.52% Gd + 80.48% Te Gd-Te70 19.15% Gd+ 80.85% Te
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