SUPPLEMENTARY INFORMATION

Transcription

1 DOI: /NCHEM.1067 Light-induced spin-crossover magnet Shin-ichi Ohkoshi, 1,2, * Kenta Imoto, 1 Yoshihide Tsunobuchi, 1 Shinjiro Takano, 1 and Hiroko Tokoro 1 1 Department of Chemistry, School of Science, The University of Tokyo Hongo, Bunkyo-ku, Tokyo , JAPAN 2 CREST, JST, 5 Sanbancho, Chiyoda-ku, Tokyo , JAPAN Correspondence should be addressed to S. O. ohkoshi@chem.s.u-tokyo.ac.jp Contents Page 1. XRD pattern, crystal structure, and hydrogen-bonding network of Fig. S1-S3 S2-S4 Table S1 2. Crystal structure and magnetic properties of a reference sample, Mn 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O Fig. S4-S5 S5-S6 Table S ESR spectrum of K 4 [Nb(CN) 8 ] 2H 2 O Temperature dependence of the visible absorption spectrum in Fig. S6 Fig. S7 S7 S8 5. Temperature dependence of the crystallographic data in Fig. S8-S9 S9-S11 Table S Fe Mössbauer spectra of Fitting of M T T curve for Magnetization vs. external field curve under the irradiation for Time dependence of magnetization after light irradiation for Fig. S10 Fig. S11 Fig. S12 Fig. S13 S12 S13-S14 S15 S Change in the visible absorption spectra of upon light irradiation 11. Change in the 57 Fe Mössbauer spectra of upon light irradiation 12. Magnetization vs. temperature curves before and after the irradiation for Fig. S14 Fig. S15 Fig. S16 S17 S18 S M T vs. T plots after light-irradiation for Fig. S17 S20 NATURE CHEMISTRY 1

2 1. XRD pattern, crystal structure, and hydrogen-bonding network of Figure S1. XRD pattern at 300 K and Rietveld analysis. Red dots, black line, and blue line represent the observed plots, calculated pattern, and their difference, respectively. Green bars represent the calculated positions of the Bragg reflections. Table S1. Crystallographic data of. Data include the lattice parameters and atomic coordinates obtained by Rietveld refinement of the powder XRD pattern at 300 K. Crystal system Space group a (Å) c (Å) V (Å 3 ) Z R wp / R p (%) Tetragonal I 4 1 /a (4) (5) (3) / 1.52 x/a y/b z/c x/a y/b z/c C(1) C(14) C(2) N(1) C(3) N(2) C(4) N(3) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) N(4) N(5) N(6) O(1) O(2) O(3) Fe Nb NATURE CHEMISTRY 2

3 Crystal structure of a Fe Nb c a b b Fe Nb a b c Figure S2. Crystal structure of. a, Cyano-bridged Fe Nb 3-dimensional framework viewed from the a-axis and b, b-axis. Red and green ball-sticks denote [FeN 6 ] and [NbC 8 ] moieties, respectively. Light blue frames are 4-pyridinealdoxime molecules. Zeolitic water molecules are omitted for clarity. NATURE CHEMISTRY 3

4 Hydrogen-bonding network in In this crystal, three types of hydrogen-bonds exist (Fig. S3), i.e. hydrogen bonds between (a) the hydroxyl group of 4-pyridinealdoxime and non-bridged cyano nitrogens of Nb(CN) 8, (b) hydroxyl group of 4-pyridinealdoxime and non-coordinated water molecules, Fe H O H N CH N O H (c) hydroxyl group of 4-pyridinealdoxime and the nitrogen atoms of other 4-pyridinealdoxime. In addition to the Fe NC Nb CN Fe 3-D main network frame,these three types of sub-3d networks may contribute to the stabilization of the structure. (a) N4(non-bridged CN) O2(4-pyridinealdoxime) N4 O2 N5 O1 N4 O2 N5 O3 O3 O2 N5 N4 O1 N5 O2 O3 N4 O3 N5 N4 O2 (b) O1(non-coordinated water) O2(4-pyridinealdoxime) (c) O3(4-pyridinealdoxime) N5(4-pyridinealdoxime) Figure S3. Hydrogen-bonding network in. NATURE CHEMISTRY 4

5 2. Crystal structure and magnetic properties of a reference sample, Mn 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O (This is a new compound.) Mn 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O a O Nb C N Mn b Mn Nb c Mn c b Nb a b c a Figure S4. Crystal structure of Mn 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O. a, Coordination environment of Mn 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O. Displacement ellipsoids are drawn at a 30% probability level. Blue, green, gray, dark gray, and light blue ellipsoids represent Mn, Nb, C, N, and O, respectively. b, Cyano-bridged Mn Nb 3- dimensional framework viewed from the a-axis and c, from the c-axis. Blue and green balls and sticks denote [MnN 6 ] and [NbC 8 ] moieties, respectively. Light blue wire frames indicate 4-pyridinealdoxime molecules. Zeolitic water molecules and hydrogen atoms are omitted for clarity. NATURE CHEMISTRY 5

6 Table S2. Crystallographic data of Mn 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O by X-ray single crystal analysis. Empirical Formula Mn 2 NbH 48.4 C 56 N 24 O 8.2 M Crystal size Crystal system Tetragonal Space group I 4 1 /a (No. 88) a / Å (15) c /Å (13) V /Å (9) d calcd /gcm T /K 293 Z 4 (Mo-K ) /cm Reflections collected Unique 3642 (R int = 0.034) R / wr2 (all data) / GOF on F Magnetic properties In the ESR spectrum at 293 K, the g-value of Mn 2 [Nb IV (CN) 8 ] (4-pyridinealdoxime) 8 0.2H 2 O is The product of the molar magnetic susceptibility ( M ) and temperature, M T, is 8.57 K cm 3 mol 1 at 300 K, which is consistent with the estimated value of 8.80 K cm 3 mol 1 for 2 Mn II (S = 5/2) and Nb IV (S = 1/2) calculated from molecular field theory. The field-cooled magnetization (FCM) curve at 10 Oe showed a spontaneous magnetization with a Curie temperature (T C ) of 40 K. The remanent magnetization (RM), and zero-field-cooled ldmagnetization i (ZFCM) curves supported this T C value. The magnetization i versus external magnetic field curve at 3K exhibits a saturation magnetization (M s ) value of 8.6 B. Assuming the compound is a ferrimagnet, the observed M s value corresponds to the expected value of 9.0 B. This indicates that an antiferromagnetic interaction occurrs between the Mn II and Nb IV. a b J < 0 Mn II NC Nb IV Figure S5. a, FCM curve in an external magnetic field of 10 Oe. b, Saturation magnetization curve at 3 K. (inset) Magnetic hysteresis loop at 3 K. NATURE CHEMISTRY 6

7 3. ESR spectrum of K 4 [Nb(CN) 8 ] 2H 2 O g = 1.99 Figure S6. ESR spectrum of K 4 [Nb(CN) 8 ] 2H 2 O measured at room temperature. NATURE CHEMISTRY 7

8 4. Temperature dependence of the visible absorption spectrum in The variable-temperature UV-vis absorption spectra exhibit optical absorptions at 480 nm (Band I) and 650 nm (Band II) as the temperature decreases (Fig. 2b, Fig. S7). These absorptions are assigned to the 1 A 1 1 T 2 and the 1 A 1 1 T 1 transitions on the Fe II LS site, respectively. Band I 1 A 1 1 T 2 Fe II (LS) Band II 1 A 1 1 T K 300 K Figure S7. Temperature dependence of the UV-vis absorption spectra in Fe 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 2H 2 O measured from 300 K to 100 K in 20 K intervals. NATURE CHEMISTRY 8

9 5. Temperature dependence of the crystallographic data in Table S3. Temperature dependence of the lattice parameters of Fe 2 [Nb(CN) 8 ] (4-pyridinealdoxime) 8 2H 2 O T (K) a (Å) c (Å) V (Å 3 ) R wp / R p (%) Fe-N(1) (Å) Fe-N(2) (Å) Fe-N3 (Å) (4) (5) (3) 1.98 / (5) (5) (3) 9(3) 2.18 / (5) (5) (3) 2.03 / (5) (6) (3) 2.16 / (5) (6) (3) 2.14 / (6) (6) (3) 2.19 / (6) 0392(6) (7) (4) / (6) (7) (4) 2.26 / (5) (6) (3) 2.12 / (6) (7) (4) 2.32 / (6) (6) (3) 2.18 / (6) (7) (4) 2.22 / (5) (6) (3) 2.12 / (6) (7) (4) 2.43 / (6) (7) (4) 2.26 / Crystal system: tetragonal, space group: I4 1 /a, Z = 4. NATURE CHEMISTRY 9

10 Temperature dependence of the lattice constants and cell volume in a a-(or b-)axis b c-axis c Volume Figure S8. Temperature dependence of the lattice constants and cell volume. a, a-(or b-)axis, b, c-axis, and c, volume. NATURE CHEMISTRY 10

11 Temperature dependence of the bond lengths around the Fe ion in N(2) Fe N(3) N(1) C Nb Figure S9. Temperature dependence of the bond lengths around the Fe ion in. Bond lengths around the Fe ion, Fe N(1) ( ), Fe N(2) ( ), and Fe N(3) ( ). Fe N bond lengths compress as the temperature decreases: 2.03 Å (300 K) 1.90 Å (20 K) (Fe N(1)), 2.26 Å 2.12 Å (Fe N(2)), and 2.29 Å 2.07 Å (Fe N(3)). NATURE CHEMISTRY 11

12 6. 57 Fe Mössbauer spectra of K Fe II (HS) Tra ansmittance K Fe II (HS) Fe II (LS) Velocity (mm s -1 ) Figure S Fe Mössbauer spectra of at 300 K (upper) and 10 K (lower). High-T form has a doublet peak due to the Fe II (HS) (isomer shift (IS) = 1.03 mm s 1 and quadrupole splitting (QS) = 1.85 mm s 1 ), whereas the low-t form has peaks due to Fe II (LS) (78%, IS = 0.52 mm s 1 and QS = 0.68 mm s 1 ) and the remaining Fe II (HS) (22%, IS = 1.12 mm s 1 and QS = 2.72 mm s 1 ). S12 NATURE CHEMISTRY 12

13 7. Fitting of M T T curve for Based on the molecular-field (MF) model, the M value of the II II IV (Fe II HS) x (Fe II LS) 2-x [Nb IV (CN) 8 ] (4-pyridinealdoxime) 8 2H 2 O system can be expressed as the following equation. This model is for ternary cyano-bridged metal compound was used, which was derived in the paper (S. Ohkoshi, et al., Phys. Rev. B, 12820, 60 (1999)) S1. In the MF model, molecular fields H i can be expressed as,, and, where H F F II II IV FeHS, H FeLS, and H Nb are the molecular fields acting on the Fe HS, Fe LS, and Nb sites, and various n ij are the molecular-field coefficients, and M FeHS, M FeLS, and M Nb are sublattice magnetizations per unit volume for the Fe II HS, Fe II LS, andnb IV sites, respectively. On the basis of the Curie Weiss law, sublattice magnetization in a paramagnetic region can be express as,, and, where H II 0 is the external magnetic field, C FeHS, C FeLS, and C Nb are Curie constants of Fe HS, Fe II LS, andnb IV sublattices, respectively. is defined as =(M FeHS + M FeLS + M Nb )/ H 0. Thus, the value can be evaluated using Curie constants and molecular-field coefficients as The n ij are related to the exchange coefficients (J ex,ij ) by.,,, and. In addition, C i can be represented as,, and, where B is the Bohr magneton, Z ij is the number of the nearest-neighbor j-site ions surrounding an i-site ion: Z FeHS Nb= Z FeLS Nb= 2; Z NbFeHS =4x; Z NbFeLS = 4(1 x); x is the fraction of Fe II HS, N is Avogadro number, and other quantities are as follows: S FeHS = 2; S FeLS = 0; S Nb = 1/2; and g Nb = From the T C value of the photo-induced d phase, the estimated J ex,fehs Nb value is -6.9 cm -1 (See Methods). In contrast, J ex,fels Nb value does not have a value because Fe II LS is diamagnetic. NATURE CHEMISTRY 13

14 When the observed M T value for HT form (x= 1) is fitted by the equation for M, the calculated curve is consistent with the observed curve at g Fe II HS = Next when the LT form is fitted by M equation with g Fe II HS = 2.17 and g Nb = 1.99, the M T vs. T plots of x= 0.22 show best fit with the observed M T T plots. Hence, the LT form is confirmed to be (Fe II HS) 0.44 (Fe II LS) 1.56 [Nb IV (CN) 8 ] (4-pyridinealdoxime) 8 2H 2 O. It should be note that the 2nd order Zeeman effect on Fe II LS was calibrated in this fitting. Figure S11. Fittings of the M T T curves for the HT and LT forms using molecular field theory. Red and blue lines represent the best fit curves for the HT and LT forms. 2nd order Zeeman effect on Fe II LS was calibrated in this fitting S2. S1. S2. Ohkoshi, S. & Hashimoto, K. Theoretical treatment of the mixed ferro-ferrimagnets composed of ternary-metal Prussian blue analogs in a paramagnetic region. Phys. Rev. B 60, (1999). Figgis, BN&Hitchman B. N. Hitchman, M. A. ed. Ligand Field Theory and Its Applications (Wiley- VCH, 2000). NATURE CHEMISTRY 14

15 8. Magnetization vs. external field curve under the irradiation for 7.4 B Figure S12. Magnetization vs. external magnetic field curve under light irradiation at 2 K. Dotted line is eye-guide. NATURE CHEMISTRY 15

16 9. Time dependence of magnetization after light irradiation for 70 % (asymptotic state) Figure S13. Time dependence of magnetization after light irradiation at 2 K. NATURE CHEMISTRY 16

17 10. Change in the visible absorption spectra of upon light irradiation Upon irradiation with 473-nm light (17 mw cm 2 ), the absorption bands of the 1 A 1 1 T 2 and 1 A 1 1 T 1 transitions in Fe II LS decrease, suggesting the observed magnetization is due to the photo-induced spin-crossover from Fe II LS to Fe II HS. Decrease of Fe II (LS) h h Figure S14. Photo-induced change in the UV-visible absorption spectra at 3K. NATURE CHEMISTRY 17

18 11. Change in the 57 Fe Mössbauer spectra of upon light irradiation A transition from Fe II LS to Fe II HS was observed by the irradiation in 57 Fe Mössbauer spectra of, indicating that the observed magnetization is due to a photo-induced spin-crossover from Fe II LS to Fe II HS. Fe II (LS) Transmittance Fe II (HS) h reduced Fe II (LS) h generated Fe II (HS) Velocity (mm s -1 ) 4 6 Figure S15. Change in 57 Fe Mössbauer spectra upon light irradiation at 10 K (black circle). Black line is fitted line composed of Fe II HS (red line) and Fe II LS (blue line). NATURE CHEMISTRY 18

19 12. Magnetization vs. temperature curves before and after the irradiation for 6 M (10 3 Oe cm 3 mol -1 ) 4 2 T C = 20 K Temperature (K) 25 Figure S16. Magnetization vs. temperature curves with increasing temperature above T C, and then going back to low temperature in the external magnetic field of 100 Oe. Black diamonds, black circles, and white circles represent the M T curves before irradiation, after irradiation in the warming, and going back to low temperature, respectively. NATURE CHEMISTRY 19

20 13. M T vs. T plots after light irradiation for a 20 b 20 (K cm 3 mol -1 ) T p = 58 K (K cm 3 mol -1 ) T p = 58 K M T ( 5 M T ( Temperature (K) Temperature (K) Figure S17. M T vs. T plots after light-irradiation with a sweeping rate of 3 K min -1 ( ) and 1Kmin -1 ( ) in the temperature region of a, 0 80 K and b, K. As a reference, the M T vs. T plots before irradiation ( ) are shown. NATURE CHEMISTRY 20