Maximizing the electron exchange in a [Fe 3 ] cluster

Transcription

1 Supplementary Information for: Maximizing the electron exchange in a [Fe 3 ] cluster Raúl Hernández Sánchez, Amymarie K. Bartholomew, Tamara M. Powers, Gabriel Ménard, and Theodore A. Betley* Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts USA. betley@chemistry.harvard.edu S1

2 Table of Contents Experimental section. Table S1: Crystallographic data for [(18 C 6)K(thf) 2 ][( tbs )LFe 3 ] (1) and [(crypt 222)K][( tbs L)Fe 3 ] (2). Table S2: Structural metrics of ( tbs L)Fe 3 (thf), 1 and 2. Figure S1: Solid state molecular structure of [( tbs L)Fe 3 ], anion in 1. Figure S2: Solid state molecular structure of [( tbs L)Fe 3 ], anion in 2. Figure S3: 1 H NMR spectrum of [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1). Figure S4: 1 H NMR spectrum of [(crypt 222)K][( tbs L)Fe 3 ] (2). Figure S5: Electrochemical behavior of the first one electron oxidation event of 1. Figure S6: 57 Fe Mössbauer spectrum of [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1) at 90 K. Figure S7: 57 Fe Mössbauer spectrum of [(crypt 222)K][( tbs L)Fe 3 ] (2) at 90 K. Figure S8: 57 Fe Mössbauer spectrum of ( tbs L)Fe 3 (thf) at 4.2 K. Figure S9: Magnetization data for [(crypt 222)K][( tbs L)Fe 3 ] (2) at 100 K. Figure S10: χ M T and χ M T vs. T for [(crypt 222)K][( tbs L)Fe 3 ] (2). Figure S11: VTVH magnetization data for [(crypt 222)K][( tbs L)Fe 3 ] (2). Figure S12: Near infrared spectrum of [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1). Figure S13: FTIR of [2.2.2]cryptand, ( tbs L)Fe 3 (thf) and [(crypt 222)K][( tbs L)Fe 3 ] (2). References S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S2

3 Experimental Section Modified synthesis for ( tbs L)Fe 3 (thf). A 100 ml thick-walled Schlenk flask equipped with a Teflon screw cap and a magnetic stirbar was charged with tbs LH 6 (390 mg, 0.52 mmol), Fe 2 (NTMS 2 ) 2 (631 mg, 0.84 mmol), and THF (ca. 20 ml). The flask was sealed and heated to 120 C for 72 h with rapid stirring. The solvent was thoroughly removed in vacuo. The solids were mixed in pentane (ca. 10 ml) and filtered on Celite. The filter was then washed with THF in a separate flask until the eluent was colorless (ca ml). The THF fraction was brought to dryness and the crude compound was recrystallized from Et 2 O at 35 C to afford the pure title complex (335 mg, 0.34 mmol, 65%). 1 H NMR spectrum is silent as previously reported. 1 Zero-field 57 Fe Mössbauer (100 K) [, E Q (mm/s): component 1 (36%): 0.46, 1.52 ( = 0.47 mm/s); component 2 (36%): 0.37, 1.99 ( = 0.31 mm/s); component 3 (28%): 0.88, 1.29 ( = 0.38 mm/s)]. S3

4 Table S1. Crystallographic data for [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1) and [(crypt 222)K][( tbs L)Fe 3 ] (2). Chemical formula C 62 H 106 Fe 3 KN 6 O 8 Si 3 Et 2 O C 60 H 102 Fe 3 KN 8 O 6 Si 3 Formula weight Space group Pbca P a (Å) (4) (3) b (Å) (3) (5) c (Å) (4) (6) (deg) (deg) (deg) V (Å 3 ) (4) 6624 (3) Z 8 4 (mm -1 ) T (K) R1 a (wr2 b ) (0.161) (0.109) Reflections Radiation type Mo K Mo K a R1 = [ w(f o F c ) 2 / wf 2 o ] 1/2 ; b wr2 = [ [w(f 2 o F 2 c ) 2 ]/ w(f 2 o ) 2 ] 1/2 ], w = 1/[ 2 (F 2 o ) + (ap) 2 + bp], where P = [max(f 2 o,0) + 2(F 2 c )]/3 S4

5 Table S2. Structural metrics of the all-ferrous ( tbs L)Fe 3 (thf) and one-electron reduced clusters 1 and 2. ( tbs L)Fe 3 (thf) [(18 C 6)K(thf) 2 ] [( tbs L)Fe 3 ] (1) [(crypt 222)K] [( tbs L)Fe 3 ] (2) Fe1 Fe (2) (9) (9) Fe2 Fe (2) (8) (9) Fe1 Fe (2) (8) (9) Fe Fe avg 2.577(35) 2.446(9) 2.462(30) Fe N Si, avg 2.029(51) 1.942(2) 1.954(5) Fe N basal, avg 2.048(24) 2.027(12) 2.033(9) Fe N avg 2.040(23) 1.998(16) 2.006(14) Fe N Fe avg 77.5(10) 74.2(4) 74.5(9) N Si Fe N basal (within same OPDA) NA 86.1(1) 86.4(3) N Si Fe N basal NA 158(1) 158(1) N basal Fe N basal NA 100.9(6) 99.9(9) S5

6 Figure S1. Solid state molecular structure of [( tbs L)Fe 3 ], anion in 1. The cation [(18 C 6)K(thf) 2 ] + and all hydrogen atoms have been omitted for clarity. Thermal ellipsoids are set to 50% probability level. S6

7 Figure S2. Solid state molecular structure of [( tbs L)Fe 3 ], anion in 2. The cation [(crypt 222)K] + and all hydrogen atoms have been omitted for clarity. Thermal ellipsoids are set to 50% probability level. S7

8 Figure S3. 1 H NMR of [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1) taken in THF-d 8 and referenced to residual solvent peaks. S8

9 Figure S4. 1 H NMR of [(crypt 222)K][( tbs L)Fe 3 ] (2) taken in THF-d 8 and referenced to residual solvent peaks. S9

10 Scan rate (mv/s) E p (mv) i pa /i pc Figure S5. Electrochemical behavior of the first one electron oxidation event of 1. S10

11 Figure S6. Zero-field 57 Fe Mössbauer spectrum of [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1) at 90 K. S11

12 Figure S7. Zero-field 57 Fe Mössbauer spectrum of [(crypt 222)K][( tbs L)Fe 3 ] (2) at 90 K. S12

13 Figure S8. Zero-field 57 Fe Mössbauer spectrum of ( tbs L)Fe 3 (thf) at 4.2 K. S13

14 Figure S9. (a) Magnetization data for [(crypt 222)K][( tbs L)Fe 3 ] (2) at 100 K from 0 to 7 T. (b) Zoomed in plot of (a) from 0 to 1 T. Used to check for ferromagnetic impurities. S14

15 Figure S10. χ M T and χ M T vs. T for [(crypt 222)K][( tbs L)Fe 3 ] (2). (a) In-phase ac magnetic susceptibility product with temperature (χ M T) collected under an oscillating 4 Oe magnetic field at 1 Hz in the temperature range 1.8 to 9 K. (b) χ M T and χ M T vs. log T. S15

16 Figure S11. Variable-temperature, variable-field reduced (VTVH) magnetization data for [(crypt 222)K][( tbs L)Fe 3 ] (2). Data were collected at increasing magnetic field from 1 to 7 T and on heating from 1.8 to 10 K. The experimental data is shown as open symbols and the fit as continuous traces. The data was fit considering an S = 11 / 2. The fit parameters that best describe the data are: (a) g = 2.06, D = 1.29 cm -1, E/D = 0.33 (residual = ); and (b) g = 2.06, D = 1.19 cm -1, E/D fixed to 0 (residual = ). S16

17 Figure S12. Near infrared spectrum of [(18 C 6)K(thf) 2 ][( tbs L)Fe 3 ] (1) in THF at room temperature. The small dints in the data above 1800 nm correspond to solvent absorptions poorly corrected. S17

18 Figure S13. FTIR of [2.2.2]cryptand (green trace), ( tbs L)Fe 3 (thf) (Blue trace), and [(crypt 222)K][( tbs L)Fe 3 ] (2) (red trace). Data collected as a KBr pellet. S18

19 References. (1) Powers, T. M.; Fout, A. R.; Zheng, S. L.; Betley, T. A. J. Am. Chem. Soc. 2011, 133, S19