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Supporting Information ph-controlled Assembly of Organophosphonate-Bridged Dy(III) Single-Molecule Magnets Based on Polyoxometalates Yu Huo, Yan-Cong Chen, Si-Guo Wu, Jian-Hua Jia, Wen-Bin Chen, Jun-Liang Liu* and Ming-Liang Tong* MOE Key Lab of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China. E-mail: liujliang5@mail.sysu.edu.cn, tongml@mail.sysu.edu.cn CONTENTS 1. Experimental... 2 2. Crystal Data and Structures... 3 3. Magnetic Characterization... 10 4. Reference... 14 1

1. Experimental 1.1 Materials and methods All chemicals used for synthesis were purchased and without any further purification. The FT-IR spectra were recorded from KBr pellets in the range 4000 400 cm 1 on an EQUINOX 55 spectrometer. Thermogravimetric analysis was carried out on a NETZSCH TG209F3 thermogravimetric analyzer. The CHN elemental analyse was carried out with an Elementar Vario-EL CHNS elemental analyzer. X-ray powder diffraction (XRPD) performed on polycrystalline samples were measured at 293 K on Bruker D8 Advance Diffratometer (Cu-Kα, λ = 1.54056 Å) by scanning over the range of 5-45. Simulated patterns were generated with Mercury. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) for Cs, Dy, K, Na, P, and W were performed with TJA IRIS(HR) spectrometry. Magnetic susceptibility measurements were performed with a Quantum Design MPMS XL-7 SQUID and a Quantum Design PPMS VSM. Polycrystalline samples were embedded in vaseline to prevent torqueing. AC magnetic susceptibility data measurements were performed with a 5 Oe ac oscillation field. All data were corrected for the diamagnetic contribution calculated using the Pascal constants. 1.2. Synthesis Scheme S1. The structure of (aminomethyl)phosphonic acid (amph 2 ) ligand. K 14 [P 2 W 19 O 69 (H 2 O)] 24H 2 O: The precursor was prepared according to the literature. S1 Synthesis of [Dy 6 (amph) 4 (H 2 O) 23 (amph 2 )(PW 11 O 39 ) 2 ] 21H 2 O (compound 1): Solid K 14 [P 2 W 19 O 69 (H 2 O)] 24H 2 O (0.566 g, 0.1 mmol) and (aminomethyl)phosphonic acid (amph 2 )(0.022 g, 0.2 mmol) were dissolved in H 2 O (10 ml), and heated to 80 ºC for 1.5 h. Then DyCl 3 6H 2 O (0.113 g, 0.3 mmol) and 0.25 ml 1M CsCl solution were added to this solution. The resultant mixture was re-adjusted to ph = 2.9 by 2 M HCl solution, and heated and stirred at 80 ºC for another 1 h. The final colorless crystalline product was obtained by slow evaporation at room temperature after about 1 week. Yield: 85 mg (13%) for 1 based on W. IR (KBr pellets): υ = 3459(br), 1623(s), 1494(m), 1259(m), 1164(vs), 1124(vs), 1099(vs), 1041(vs), 956(vs), 898(s), 848(vs), 805(vs), 726(vs), 590(vs), 503(s). Elemental analysis (%) calcd C, 0.78; H, 1.59; N, 0.90; P, 2.80; Dy, 12.59; W, 52.22. Found: C, 1.09; H, 1.41; N, 0.75; P, 2.83; Dy, 12.83; W, 52.46. 2

Synthesis of Cs 9 K 13 Na 13 [Dy 9 (H 2 O) 12 (CO 3 ) 3 (amph) 2 (PW 10 O 37 ) 6 ] 66H 2 O (compound 2): Solid K 14 [P 2 W 19 O 69 (H 2 O)] 24H 2 O (0.566 g, 0.1 mmol) and amph 2 (0.022 g, 0.2 mmol) were dissolved in H 2 O (10 ml), and heated to 80 ºC for 1.5 h. The resulting solution was stirred, and solid DyCl 3 6H 2 O (0.113 g, 0.3 mmol) and 0.25 ml 1 M CsCl solution was added, raising the ph to ca. 7.4 by addition of 1 M NaOH solution. The resulting suspension was heated and stirred at 80 ºC for another 1 h, and then allowed to stand at room temperature until the precipitate had settled at the bottom of the beaker and was then removed by filtration. The final colorless crystalline product was obtained by slow evaporation at room temperature after about 2 weeks. Yield: 107 mg (17%) for compound 2 based on W. IR (KBr pellets): υ = 3432(br), 1626(s), 1532(m), 1426(m), 1121(s), 1090(s), 1152(s), 1020(s), 938(vs), 825(vs), 794(s), 727(s), 680(s), 590(m), 512(m). Elemental analysis (%) calcd H, 0.82; Cs, 5.99; K, 2.53; Na, 1.50; P, 1.24; Dy, 7.33; W, 55.28. Found: H, 1.09; Cs, 5.75; K, 2.38; Na, 1.65; P, 1.45; Dy, 7.32; W, 54.69. Scheme S2. The schematic synthetic process of compounds 1 and 2. 2. Crystal Data and Structures 2.1. X-ray Crystallography The crystallographic data for compounds 1 and 2 were given in Table S1. Diffraction data were collected on Bruker D8 QUEST diffractometer with Mo-Kα radiation (λ = 0.71073 Å) at 120(2) K. The Data indexing and integration were carried out using a Bruker APEX3 program. The structures were solved by dual-space algorithm (SHELXT), S2 and all non-hydrogen atoms were refined anisotropically by least-squares on F 2 using the SHELXTL 2014 program suite. S3 Anisotropic thermal parameters were assigned to all non-hydrogen atoms, except oxygens of lattice waters. The hydrogen atoms of the organic ligands were placed in idealised positions and refined using a riding model to the atom to which they were attached; no attempt has made to locate hydrogen atoms of water molecules. During the refinement, the restraint command ISOR was used to restrain a number of non-h atoms with ADP problems. In compound 1, the water molecule O33 was disposed to disorder over two positions with an occupancy factor of 0.750/0.250 (O33 and amph 2 ). The disordered solvent molecules in 2 were squeezed S4 and determined by the elemental analysis and thermogravimetric analysis. Crystallographic data for the structures reported in this paper have been deposited in the Cambridge Crystallographic Data Center. 3

Table S1. Crystal data and structure refinement for compounds 1 and 2. 1 2 Empirical formula H 114 C 5 Dy 6 N 5 O 137 P 7 W 22 H 166 C 5 Cs 9 Dy 9 K 13 N 2 Na 13 O 310 P 8 W 60 Mr (g.mol 1 ) 7673.21 19959.18 T (K) 120(2) 120(2) Crystal system monoclinic monoclinic Space group C2/m C2/c a (Å) 27.7371(8) 19.1059(16) b (Å) 21.1467(6) 40.407(4) c (Å) 11.7893(3) 41.245(4) α (deg) 90 90 β (deg) 111.751(1) 92.6158(13) γ (deg) 90 90 V (Å 3 ) 6422.7(3) 31808(5) Z 2 4 Dc (g. cm 3 ) 3.922 4.068 µ (mm 1 ) 23.264 25.030 Data/restraints/parameters 7561/794/460 31249/3718/1803 Reflns collected 34916 234089 GOF 1.156 1.066 R 1, wr 2 [I>2σ(I)] a R 1 = 0.0233, wr 2 = 0.0550 R 1 = 0.0847, wr 2 = 0.1771 R 1, wr 2 [all data] b R 1 = 0.0270, wr 2 = 0.0561 R 1 = 0.1593, wr 2 = 0.2228 CCDC 1590468 1590469 a R 1 = F o - F c / F o, wr 2 = [ w(f 2 o - F 2 c ) 2 / w(f 2 o ) 2 ] 1/2 Table S2. BVS values for W, Dy and P atoms in 1. Bond Length / Å Bond Valence Bond Length / Å Bond Valence W(1)-O(7) 1.729(4) 1.680 W(2)-O(12) 1.719(3) 1.726 W(1)-O(4) 1.760(3) 1.545 W(2)-O(9) 1.866(4) 1.160 W(1)-O(6) 1.9287(17) 0.979 W(2)-O(14) 1.9(3(4) 1.050 W(1)-O(10) 1.946(4) 0.935 W(2)-O(11) 1.9106(12) 1.029 W(1)-O(9) 2.056(3) 0.694 W(2)-O(13) 1.917(4) 1.011 W(1)-O(8) 2.450(3) 0.239 W(2)-O(8) 2.489(3) 0.215 v(w1) = 6.072 v(w2) = 6.191 W(3)-O(15) 1.714(5) 1.749 W(4)-O(18) 1.704(4) 1.797 W(3)-O(13)#1 1.909(4) 1.033 W(4)-O(20) 1.822(4) 1.307 W(3)-O(13) 1.909(4) 1.033 W(4)-O(25)#1 1.919(4) 1.005 W(3)-O(17)#1 1.912(4) 1.025 W(4)-O(19) 1.925(3) 0.989 W(3)-O(17) 1.912(4) 1.025 W(4)-O(17) 1.977(4) 0.859 W(3)-O(16) 2.425(5) 0.256 W(4)-O(16) 2.434(3) 0.250 v(w3) = 6.120 v(w4) = 6.208 4

W(5)-O(21) 1.721(4) 1.717 W(6)-O(24) 1.702(4) 1.807 W(5)-O(5) 1.764(4) 1.528 W(6)-O(26) 1.868(4) 1.154 W(5)-O(23) 1.915(3) 1.016 W(6)-O(25) 1.904(4) 1.047 W(5)-O(26)#1 1.946(4) 0.935 W(6)-O(10) 1.907(4) 1.038 W(5)-O(20) 2.074(4) 0.661 W(6)-O(14) 1.961(3) 0.897 W(5)-O(22) 2.357(3) 0.308 W(6)-O(8) 2.391(3) 0.281 v(w5) = 6.165 v(w6) = 6.225 Dy(1)-O(3)#1 2.302(3) 0.487 Dy(2)-O(28) 2.217(4) 0.613 Dy(1)-O(3) 2.302(3) 0.487 Dy(2)-O(27)#2 2.237(4) 0.581 Dy(1)-O(4)#1 2.323(3) 0.460 Dy(2)-O(33) 2.271(1) 0.530 Dy(1)-O(4) 2.323(3) 0.460 Dy(2)-O(33 ) 2.50(2) 0.285 Dy(1)-O(2) 2.379(5) 0.396 Dy(2)-O(30) 2.413(4) 0.361 Dy(1)-O(5)#1 2.394(4) 0.380 Dy(2)-O(31) 2.414(5) 0.360 Dy(1)-O(5) 2.394(4) 0.380 Dy(2)-O(29) 2.423(4) 0.351 Dy(1)-O(1) 2.553(6) 0.247 Dy(2)-O(32) 2.474(4) 0.306 Dy(2)-O(7)#1 2.550(4) 0.249 v(dy1) = 3.298 v(dy2) = 3.107 P(3)-O(22) 1.523(5) 1.231 P(3)-O(16) 1.542(5) 1.170 P(3)-O(8)#1 1.545(4) 1.160 P(3)-O(8) 1.545(4) 1.160 Symmetry code: v(p3) = 4.721 #1: y+1, -x+y+1,-z;#2: x-y, x-1, -z. Table S3. Selected bond distances (Å) for polyanion 2. Bond Length (Å) Bond Length (Å) Bond Length (Å) Dy(1)-O(4) 2.27(2) Dy(2)-O(40) 2.30(2) Dy(3)-O(3) 2.32(2) Dy(1)-O(24) 2.38(2) Dy(2)-O(59) 2.33(2) Dy(3)-O(13) 2.30(2) Dy(1)-O(27) 2.26(2) Dy(2)-O(64) 2.28(2) Dy(3)-O(18) 2.43(3) Dy(1)-O(112) 2.45(2) Dy(2)-O(116) 2.73(3) Dy(3)-O(41) 2.33(2) Dy(1)-O(113) 2.28(2) Dy(2)-O(117) 2.298(19) Dy(3)-O(50) 2.31(2) Dy(1)-O(114) 2.38(3) Dy(2)-O(118) 2.45(2) Dy(3)-O(54) 2.42(2) Dy(1)-O(115) 2.325(19) Dy(2)-O(119) 2.41(3) Dy(3)-O(115) 2.41(2) Dy(1)-O(116) 2.80(3) Dy(2)-O(120) 2.267(19) Dy(3)-O(117) 2.413(19) Dy(4)-O(77) 2.287(19) Dy(5)-O(78) 2.36(2) Dy(4)-O(95) 2.33(2) Dy(5)-O(78)#6 2.36(2) Dy(4)-O(100) 2.32(2) Dy(5)-O(88)#6 2.33(2) Dy(4)-O(121) 2.28(2) Dy(5)-O(88) 2.33(2) Dy(4)-O(122) 2.46(2) Dy(5)-O(91) 2.43(2) Dy(4)-O(123) 2.38(3) Dy(5)-O(91)#6 2.43(2) Dy(4)-O(124) 2.763(7) Dy(5)-O(125)#6 2.39(2) Symmetry code : Dy(4)-O(125) 2.33(2) Dy(5)-O(125) 2.39(2) #6: 2-X, +Y, 1/2-Z. 5

Table S4. Lanthanides geometry analysis by using Continuous Shape Measurements (CShM) α Shape SAPR-8 (D 4d ) TDD-8 (D 2d ) JBTPR-8 (C 2v ) BTPR-8 (C 2v ) JSD-8 (D 2d ) Compound 1 Dy1 0.318 2.769 2.513 2.330 5.160 Dy2 0.851 1.975 1.216 1.347 3.385 Dy1 2.666 2.917 1.456 1.724 3.627 Dy2 2.360 2.837 1.584 1.723 3.741 Compound 2 Dy3 1.123 2.728 3.247 2.505 5.313 Dy4 2.754 2.914 1.466 1.645 3.377 Dy5 1.304 2.894 3.475 2.734 5.607 Coordination environments for Dy centers in 1: Coordination environments for Dy centers in 2: SAPR-8 = Square antiprism; TDD-8 = Triangular dodecahedron; JSD-8 = Snub diphenoid J84; JBTPR-8 = Biaugmented trigonal prism J50; BTPR-8 = Biaugmented trigonal prism. α (a) Alvarez, S., Alemany, P., Casanova, D., Cirera, Llunell, J., M., Avnir, D. Coord. Chem. Rev., 2005, 249, 1693-1708; (b) Casanova, D., Llunell, M., Alemany, P., Alvarez, S. Chem. Eur. J., 2005, 11, 1479-1494. 6

2.2. Additional Structural Figures Figure. S1 a, b) Crystal Structure of 1 viewed along the c axis and b axis. H atoms are omitted for clarity. 7

Figure. S2 Combined the wires and space-filling representation of polyanion 2. Figure. S3 The dihedral angles between the {Dy 3 } triangle (plane 2) and equatorial planes of the {PW 11 O 37 } subunits (plane 1 & 3) in polyanion 2. 8

Figure. S4 Selected Interatomic Distances (Å) and Angles (deg) in the planar triangular unit in polyanion 2. 2.3. Additional measurements Figure. S5 PXRD patterns of compounds 1 (a) and 2 (b) compared with the simulated patterns from the single crystal structures. Figure. S6 Thermogravimetric (TG) curves of compounds 1 (a) and 2 (b) under N 2 atmosphere (10 K min -1 ). 9

Figure. S7 Infrared spectra for compounds 1 (red) and 2 (black). 3. Magnetic Characterization Figure. S8 The temperature dependences of χ M T measure at a 1000 Oe dc field for compounds 1 (a) and 2 (b). Inset: The field dependence of magnetization at 2.0, 3.0, and 5.0 K. The solid lines are guided by eyes. Figure. S9 Plots of M-HT 1 at 2.0, 3.0, and 5.0 K for compounds 1 (a) and 2 (b). The solid lines are guided by eyes. 10

Figure. S10 Temperature dependences of the in-phase (χ M ') and out-of-phase (χ M '') ac susceptibility of compound 1 under the zero dc field. Figure. S11 a, b) Temperature and frequency dependence of the in-phase (χ M T) and out-of-phase (χ M ) products under zero dc field for compound 2 with ac frequencies of 1 1488 Hz. 11

Figure. S12 Frequency dependence of χ M ' and χ M " signals at various fields for compound 2 at 2 K. Figure. S13 The dc field dependence of the relaxation time for compound 2 at 2 K. Figure. S14 Cole Cole plot for the AC susceptibilities under a zero DC field for compound 2. 12

Figure. S15 Fitted Raman and Orbach processes with the experimental data points for 2. Figure. S16 Magnetic hysteresis loops for compound 1 at the indicated field sweep rates (2 K). Figure. S17 Magnetic hysteresis loops for compound 2 at the indicated field sweep rates (2 K). 13

4. Reference S1. C. M. Tourne, G. F. J. Tourne, Chem. Soc., Dalton Trans, 1988, 2411. S2. G. M. Sheldrick, Acta Cryst, 2015, A71, 3-8. S3. G. M. Sheldrick, Acta Cryst, 2015, C71, 3-8. S4. A. L. Spek, Acta Cryst, 2015, C71, 9-18. 14