Ligand Redox Non-innocence in the Stoichiometric Oxidation of Mn 2 (2,5-dioxidoterephthalate) (Mn-MOF-74)

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1 Ligand Redox Non-innocence in the Stoichiometric Oxidation of Mn 2 (2,5-dioxidoterephthalate) (Mn-MOF-74) Supporting Information Anthony F. Cozzolino, Carl K. Brozek, Ryan Palmer, Junko Yano, Minyuan Li, and Mircea Dincă* mdinca@mit.edu Table of Contents S1.1. Materials.... S3 S1.2. Large scale synthesis of Mn 2((CO 2) 2O 2C 6H 2) (Mn 2DOBDC).... S3 S1.3. Auto-oxidized/low-quality Mn 2DOBDC.... S3 S1.4. Treatment of Mn 2DOBDC with O S4 S1.5. Treatment of Mn 2DOBDC with Cl 2 gas.... S4 S1.6. Treatment of Mn 2DOBDC with 1 or 2 equivalents of PhICl 2 in DCM at 20 C.... S4 S1.7. Cl 2Mn 2DOBDC.... S4 S1.8. Treatment of Mn 2DOBDC with 1 eq. PhICl 2 for NMR Study.... S5 S1.9. Treatment of Mg 2DOBDC with 1 eq. Cl 2IPh.... S6 S1.10. Treatment of Mn 2DOBDC and Mg 2DOBDC with 1 eq. Cl 2IPh NMR Study... S6 S1.11. Magnetic measurements.... S7 S1.12. X-ray absorption spectroscopy.... S8 S1.13. Other physical measurements.... S8 Figure S1. Comparison of PXRD data for Mn 2DOBDC prepared under aerobic and anaerobic conditions.... S4 Figure S2. 1 H NMR spectrum 1 h after treating Mn 2DOBDC with PhICl 2 (*) showing formation of IPh (#).... S5 Figure S3. 1 H NMR spectrum 12 h after treating Mn 2DOBDC with a stoichiometric amount of PhICl 2(*) showing formation of IPh (#). Quantitative consumption of PhICl 2 was observed.... S6 Figure S4. 1 H NMR of PhICl 2 neat, in the presence of Mn 2DOBDC, and Mg 2DOBDC after 2 h or 6 h.... S7 Figure S5. Diamond ATR FT-IR spectra of (top) as-synthesized, (middle) methanol-exchanged and (bottom) desolvated Mn 2DOBDC.... S9 Figure S6. Diamond ATR FT-IR spectra of activated (black) air oxidized Mn 2DOBDC, (grey) pristine Mn 2DOBDC. The only visible difference, a shoulder at 1600 cm 1, is indicated by an arrow.... S9 Figure S7. Isotherms for the adsorption of N 2 in Mn 2DOBDC (solid line, closed circles) and airoxidized Mn 2DOBDC (hashed line, open circles).... S10 Figure S8. PXRD of (top) ozone-treated Mn 2DOBDC and (bottom) simulated Mn 3O S10 S1

2 Figure S9. Diamond ATR FT-IR spectra of Cl 2-treated Mn 2DOBDC (top) and pristine Mn 2DOBDC (bottom).... S11 Figure S10. Isotherms for the adsorption of N 2 in Cl 2-treated Mn 2DOBDC (blue line) and PhICl 2- treated Mn 2DOBDC (green line is 2:1 20 C, red line is 1:1 20 C, purple line is 1:1 35 C).... S11 Figure S11. Diamond ATR FT-IR Infrared spectra of activated DCM/PhICl 2-treated Mn 2DOBDC (top 40 C, 1:1 stoichiometry; middle 20 C, 2:1 stoichiometry) and pristine Mn 2DOBDC(bottom)... S12 Figure S12. XPS spectra of Mn 2DOBDC (bottom) and Cl 2Mn 2DOBDC (top) indicating elementspecific binding energies.... S12 Figure S13. Far-IR difference spectrum obtained by subtracting the spectrum of pristine Mn 2DOBDC from that of PhICl 2-treated Mn 2DOBDC.... S13 Figure S14. Depiction of two different orientations of PhICl 2 6 in the channels of Mn 2DOBDC 7. Colors represent Mn (orange), O (red), and C (grey), H (light grey), I (purple), Cl (green).... S13 Figure S15. Variable temperature magnetic susceptibility of Mn 2DOBDC in an applied field of 1 koe.... S14 References... S15 S2

3 Experimental Section S1.1. Materials. Iodobenzene (98%, Sigma-Aldrich), MnCl 2 4H 2O (>98%, Sigma-Aldrich), N,N - dimethylethylenediamine (99%, Sigma-Aldrich), dichloromethane (DCM, HPLC grade, Honeywell), methanol (MeOH, 99.9%, VWR), tetrahydrofuran (THF, ACS grade, BDH), pentane (Reagent Grade, BDH), C 6D 6 (Cambridge Isotopes), CD 2Cl 2 (Cambridge Isotopes), CDCl 3 (Cambridge Isotopes), and DMSO-d 6 (Cambridge Isotopes) were used as received. N,N-dimethylformamide (DMF), MeOH, DCM, THF and pentane, when noted as dry, were dried in a Glass Contour solvent purification system. PhICl 2, 1 H 4DOBDC, 2 and Mg 2DOBDC 3 were prepared according to published procedures. Cl 2 was prepared by the treatment of potassium permanganate with hydrochloric acid and passed through H 2SO 4 prior to use. S1.2. Large scale synthesis of Mn 2((CO 2) 2O 2C 6H 2) (Mn 2DOBDC). An oven-dried 500 ml round-bottom flask was charged with MnCl 2 4H 2O (10.7 g, 54.1 mmol) and H 4DOBDC (2.7 g, 13 mmol). An N 2-sparged mixture of EtOH/DMF (1:15, 320 ml) was added to the flask and sparged for 10 min. The flask was fitted with an N 2-flushed reflux condenser and the solution was heated at 135 C for 3 days with stirring. After several hours, a bright orange solid began to form. Upon completion, the reaction was cooled to room temperature and the solids were quickly filtered in air, rinsed with clean DMF and transferred into an N 2 purged Soxhlet apparatus. Dry and air-free MeOH was used to extract the sample for 2 days. Following the extraction, excess MeOH was removed under N 2 and the solids were dried under vacuum. The exchange and activation process could be followed by IR spectroscopy, which revealed the absence of methanol and DMF in activated Mn 2DOBDC (Figure S5). The sample was transferred to an N 2-filled glove box and inserted into a heating tube with a male 24/40 ground glass joint in order to eliminate potential for contact with grease. The tube was connected to a high vacuum line through a female-to-female ground glass adapter with a glass wool plug and heated to 200 C in a custom-made heating mantle until a pressure of 10 5 torr could be maintained for 2 min. This yielded 2.5 g of analytically pure product. Anal. Calcd for Mn 2C 8H 2O 4: C, 31.61; H, 0.66; N, 0. Found: C, 31.49; H, 1.05; N, 0. IR (ATR, neat): 1541 (s), 1410 (s), 1359 (m), 1236 (m), 1197 (s), 1121 (w), 910 (w), 882 (m), 812 (m), 575 (w), 471 (w) cm -1. The N 2 adsorption isotherm (Figure S7) gave BET and Langmuir apparent surface areas of SA BET = 1353(4) m 2 /g and SA Langmuir = 1478(3) m 2 /g S1.3. Auto-oxidized/low-quality Mn 2DOBDC. The same procedure that was used above was followed with the exception that the solvents and the reaction mixture were not sparged with N 2 and that the heating was performed open to air. The sample was activated in an analogous manner. This yielded 2.25 g of a dark brown crystalline material. Anal. Calcd for Mn 2O 6C 8H 2: C, 31.61; H, 0.66; N, Found: C, 32.1; H, 1.02; N, IR (neat): 1597 (sh, w) 1541 (s), 1410 (s), 1359 (m), 1236 (m), 1197 (s), 1121 (w), 910 (w), 882 (m), 812 (m), 575 (w), 471 (w) cm -1. Note that despite the differences in the elemental analysis and the infrared spectra (Figure S6), there are no obvious differences in the PXRD (Figure S1). PXRD cannot be used to confirm the purity of the sample. S3

4 Figure S1. Comparison of PXRD data for Mn 2DOBDC prepared under aerobic and anaerobic conditions. S1.4. Treatment of Mn 2DOBDC with O 3. Ozone from a Pacific Ozone L series ozone generator was introduced into a flask containing activated Mn 2DOBDC (0.1 g). The experiment was performed either at room temperature or with cooling using a dry ice/acetone bath. At both of these temperatures the sample spontaneously combusted and left a black residue which was recovered for further analysis. IR revealed the absence of all organic components and PXRD revealed that the sample contained only Mn 3O 4 as a crystalline phase. S1.5. Treatment of Mn 2DOBDC with Cl 2 gas. A volume of 0.2 ml (4.5 mmol, assuming ideal gas) of Cl 2 was added by syringe to a N 2 atmosphere flask containing 0.5 g (1.3 mmol) of Mn 2DOBDC. Upon addition of Cl 2 the sample immediately turned black. The sample was evacuated and refilled with N 2 three times to remove any residual Cl 2 gas and the black solid was recovered for further analysis. S1.6. Treatment of Mn 2DOBDC with 1 or 2 equivalents of PhICl 2 in DCM at 20 C. A DCM solution (10 ml) of PhICl 2 (0.37 g, 1.0 mmol or 0.54 g, 2.0 mmol; 1 or 2 eq.) was added dropwise over the course of a minute to a stirring suspension (10 ml DCM) of Mn 2DOBDC (0.3 g, 1.0 mmol). The orange material turned dark upon addition and stayed dark as the mixture was stirred for 12 h. The mixture was centrifuged and the solution decanted. The material was washed three times with DCM, stirring 6 hours per wash, and three times with pentane, also stirring for 6 h per wash. The material was activated at 100 C until a pressure of 10 5 torr could be maintained for 2 min. Higher temperature activation strategies resulted in loss of porosity and crystallinity according to PXRD analysis and N 2 gas sorption analysis. S1.7. Cl 2Mn 2DOBDC. A DCM solution (10 ml) of PhICl 2 (0.37 g, 1.0 mmol, 1.00 eq.) was cooled to 35 C and added dropwise over the course of two minutes to a stirring suspension (10 ml DCM) of Mn 2DOBDC (0.3 g, 1.0 mmol) that had been cooled to 35 C. The reaction mixture was maintained at this temperature in a cooled aluminum block. The orange material darkened slightly upon the addition of the oxidant, and gradually became darker as the sample and aluminum block warmed to room temperature. After 12 h, the mixture was centrifuged and the solution decanted. In a similar way, the material was washed three times with DCM, stirring 6 hours per wash, and three times with pentane, also stirring for 6 h per wash. The material was activated at 100 C until a pressure of 10 5 torr could be maintained for 2 min. Higher temperature activation strategies resulted in loss of porosity and crystallinity according to PXRD S4

5 analysis and N 2 gas sorption analysis. Anal. Calcd for Cl 2Mn 2C 8H 2O 4: C, 25.63; H, 0.54; N, 0; Cl, Found: C, 25.71; H, 0.72; N, 0; Cl, S1.8. Treatment of Mn 2DOBDC with 1 eq. PhICl 2 for NMR Study. A similar procedure to that described in S1.7 was followed. A deuterated DCM (CD 2Cl 2) solution (1.5 ml) of PhICl 2 (0.042 g, 0.15 mmol, 1.00 eq.) was cooled to 35 C and added dropwise over the course of two minutes to a stirring suspension (1.5 ml deuterated DCM) of Mn 2DOBDC (0.047 g, 0.15 mmol) that had been cooled to 35 C. The reaction was kept cool in a pre-cooled aluminum block, and allowed to warm to room temperature over the course of 12 h. The mixture was then centrifuged, and the solution decanted. The material was washed three times in a similar manner with deuterated DCM, and the decanted solutions were collected and combined. Mesitylene (0.05 ml, 0.3 mmol) was added to the combined solutions as an internal standard, and a 1 H NMR was collected. The reaction was subsequently repeated, but stopped after only 1 h. NMR of Cl 2IPh and IPh were also collected. * # # * * # Figure S2. 1 H NMR spectrum 1 h after treating Mn 2DOBDC with PhICl 2 (*) showing formation of IPh (#). S5

6 # # # Figure S3. 1 H NMR spectrum 12 h after treating Mn 2DOBDC with a stoichiometric amount of PhICl 2 showing formation of IPh (#). Quantitative consumption of PhICl 2 was observed. S1.9. Treatment of Mg 2DOBDC with 1 eq. Cl 2IPh. The same procedure that was used for the preparation of Cl 2Mn 2DOBDC (S1.7) was followed. A DCM solution (3 ml) of PhICl 2 (0.082 g, 0.3 mmol, 1.00 eq.) was cooled to 35 C and added dropwise over the course of two minutes to a stirring suspension (3 ml DCM) of Mg 2DOBDC (0.073 g, 0.3 mmol) that had been cooled to 35 C. The reaction mixture was maintained at this temperature in a cooled aluminum block and allowed to slowly warm to room temperature. The yellow material did not appear to change color over the course of the reaction. After 12 h, the mixture was centrifuged and the solution decanted. In a similar way, the material was washed three times with DCM, stirring 6 hours per wash, and three times with pentane, also stirring for 6 h per wash. The material was activated at 100 C until a pressure of 10 5 torr could be maintained for 2 min. Anal. Calcd for Mg 2C 8H 2O 6(DMF) 0.2(H 2O) 1.8: C, 35.64; H, 2.43; N, Found: C, 35.85; H, 3.20; N, S1.10. Treatment of Mn 2DOBDC and Mg 2DOBDC with 1 eq. Cl 2IPh NMR Study. A similar procedure to that used previously (S1.7) was followed. A deuterated DCM (CD 2Cl 2) solution (2 ml) of PhICl 2 (0.046 g, 0.17 mmol, 1.00 eq.) was cooled to 35 C and added dropwise over the course of two minutes to a stirring suspension (1 ml deuterated DCM) of Mn 2DOBDC (0.051 g, 0.17 mmol, 1.00 eq.) or Mg 2DOBDC (0.041 g, 0.17 mmol, 1.00 eq.) that had been cooled to 35 C. The reaction was kept cool in an aluminum block for the desired reaction time (2 hours or 6 hours) at which point an aliquot of the solution was removed and NMR was collected. A control experiment was also performed in tandem where a deuterated DCM solution (3 ml) of PhICl 2 (0.046 g, 0.17 mmol, 1.00 eq.) was treated as described above, without its addition to a MOF suspension, to observe the decomposition of PhICl 2 under the reaction conditions. S6

7 Figure S4. 1 H NMR of PhICl 2 neat, in the presence of Mn 2DOBDC, and of Mg 2DOBDC after 2 h or 6 h. The green-shaded peaks correspond to PhICl 2; theunshaded peaks correspond to PhI, formed by decomposition of PhICl 2. S1.11. Magnetic measurements. Magnetic data were collected using a Quantum Design MPMS-XL SQUID magnetometer. A gelatin capsule was filled with evacuated crystals of Cl 2Mn 2DOBDC or Mn 2DOBDC to obtain susceptibility data. DC susceptibility measurements were obtained under a DC field of 1000 Oe between 5 K 300 K for Cl 2Mn 2DOBDC and 200 K 300 K for Mn 2DOBDC. All data was corrected for diamagnetic contributions from the capsule. Pascal s constants were used to account for diamagnetic corrections for the sample itself. 4 Variable temperature susceptibility for Cl 2Mn 2DOBDC was fit to a model described previously for Fe 2DOBDC, where Fischer s model of Heisenberg 1-D chains was modified to include interchain coupling. 5 J and J' (the coupling constants for intra- and inter-chain magnetic interactions) were varied through a non-linear least-squares minimization method, with J' constrained to lie within 0 > J' > 1.5 cm 1. where = 3 (, ) 8( (, )) (, )= ( +1)(1+ ) (1 ) S7

8 where =coth ( +1) Here, k B is the Boltzmann constant, g iso is the istropic Landé g-factor, S is the spin state, J is the intrachain coupling parameter, J' is the interchain coupling parameter, and z is the number of interacting nearestneighbors. S1.12. X-ray absorption spectroscopy. Data from X-ray absorption near edge structure spectroscopy (XANES) were collected at the Advanced Light Source (ALS) on beamline with an electron energy of 1.9 GeV and an average current of 500 ma. The radiation was monochromatized by a Si(111) doublecrystal monochromator. The intensity of the incident X-ray was monitored by an N 2-filled ionization chamber (I0) in front of the sample. The energy was calibrated with a Mn foil ( ev). All data were collected at room temperature. Data reduction of the XAS spectra was performed using custom software. Preedge and postedge contributions were subtracted from the XAS spectra, and the result was normalized with respect to the edge jump. S1.13. Other physical measurements. Infrared spectra were obtained on neat samples using a Bruker Alpha equipped with an attenuated total reflectance (ATR) accessory with a diamond crystals, in a nitrogen purged glovebox. Powder X-ray diffraction patterns were recorded on a Bruker Advance D8 diffractometer using Nickel-filtered Cu-Kα radiation (λ = Å), with accelerating voltage and current of 40 kv and 40 ma, respectively. Elemental (combustion) miroanalyses were performed by Midwest Microlab, LLC or Complete Analysis Laboratories Inc. S8

9 Figure S5. Diamond ATR FT-IR spectra of (top) as-synthesized, (middle) methanol-exchanged and (bottom) desolvated Mn 2DOBDC. Figure S6. Diamond ATR FT-IR spectra of activated (black) air oxidized Mn 2DOBDC, (grey) pristine Mn 2DOBDC. The only visible difference, a shoulder at 1600 cm 1, is indicated by an arrow. S9

10 Figure S7. Isotherms for the adsorption of N 2 in Mn 2DOBDC (solid line, closed circles) and air-oxidized Mn 2DOBDC (hashed line, open circles). Mn 2 DOBDC + O 3 Mn 3 O 4 simulated θ Angle ( ) Figure S8. PXRD of (top) ozone-treated Mn 2DOBDC and (bottom) simulated Mn 3O 4. S10

11 Figure S9. Diamond ATR FT-IR spectra of Cl 2-treated Mn 2DOBDC (top) and pristine Mn 2DOBDC (bottom). Figure S10. Isotherms for the adsorption of N 2 in Cl 2-treated Mn 2DOBDC (blue line) and PhICl 2- treated Mn 2DOBDC (green line is 2:1 20 C, red line is 1:1 20 C, purple line is 1:1 35 C). S11

12 Figure S11. Diamond ATR FT-IR Infrared spectra of activated DCM/PhICl 2-treated Mn 2DOBDC (top 40 C, 1:1 stoichiometry; middle 20 C, 2:1 stoichiometry) and pristine Mn 2DOBDC(bottom) Figure S12. XPS spectra of Mn 2DOBDC (bottom) and Cl 2Mn 2DOBDC (top) indicating element-specific binding energies. S12

13 Figure S13. Far-IR difference spectrum obtained by subtracting the spectrum of pristine Mn 2DOBDC from that of PhICl 2-treated Mn 2DOBDC. Figure S14. Depiction of two different orientations of PhICl 2 6 in the channels of Mn 2DOBDC 7. Colors represent Mn (orange), O (red), and C (grey), H (light grey), I (purple), Cl (green). S13

14 Figure S15. Variable temperature magnetic susceptibility of Mn 2DOBDC in an applied field of 1 koe. S14

15 References (S1) Lucas, H. J.; Kennedy, E. R. Org. Synth. 1942, 22, 69. (S2) Sikkema, Doetze Jakob Reichwein, A. M. Process for dicarboxylating dihydric phenols (S3) Caskey, S. R.; Wong-Foy, A. G.; Matzger, A. J. J. Am. Chem. Soc. 2008, 130, (S4) Bain, G. A.; Berry, J. F. J. Chem. Educ. 2008, 85, 532. (S5) Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Science (New York, N.Y.) 2012, 335, (S6) Archer, E. M.; van Schalkwyk, T. G. Acta Crystallographica 1953, 6, (S7) Geier, S.; Mason, J. A.; Bloch, E.; Queen, W.; Hudson, M.; Brown, C. M.; Long, J. R. Chem. Sci. 2013, 4, S15