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Electronic Supplementary Information for
Catalytic and Regiospecific Extradiol Cleavage of Catechol by a Biomimetic Iron Complex
Sayanti Chatterjee, Debobrata Sheet and Tapan Kanti Paine*
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata-700032, India
(positive ion mode, MeCN): m/z = 209.03 (100%, [M+H]+), 231.01 (10%, [M+Na]+]. X-ray crystallographic data collection and refinement and solution of the structure of 1: X-ray
single-crystal data for 1 were collected at 120 K using Mo Kα (λ = 0.7107 Å) radiation on a SMART-
APEX diffractometer equipped with CCD area detector. Data collection, data reduction, structure solution
and refinement were carried out using the software package of APEX II.[2] The structure was solved by
direct method and subsequent Fourier analyses and refined by the full-matrix least-squares method based
on F2 with all observed reflections.[3] The non-hydrogen atoms were treated anisotropically. In each of the
asymmetric unit one methanol molecule was found to be present. The hydrogen atom (O2-H) of methanol
molecule could not be assigned in structure refinement. Crystal data of 1: MF = C19H27Cl2FeN4O2, Mr = 470.2, monoclinic, space group Cc, a = 13.3894(8), b =
14.7280(9), c = 10.9907(7) Å, α = 90.00° β = 96.691(2)°, γ = 90.00°, V = 2152.6(2) Å3, Z = 4, ρ = 1.451
mg m-3, µ Mo-Kα = 0.971 mm-1, F(000) = 980, GOF = 1.180, A total of 12356 reflections were collected
in the range 2.06≤ θ ≤ 24.99, 3507 of which were unique (Rint = 0.0175). R1(wR2) = 0.0205 (0.0786) for
263 parameters and 3507 reflections (I > 2σ(I)).
Table S1. Selected bond distances (Ǻ) and angles (°) for complex 1.
Figure S3. X-band EPR spectrum of complex 2 in dichloromethane and acetonitrile (1:1). (Experimental parameters: temperature = 77 K, microwave frequency = 9.13 GHz, microwave power = 0.998 mW, modulation frequency = 100 kHz, modulation width = 1 mT, time constant = 0.03 s)
Figure S4. Optical spectral changes with time (time interval = 60 s) during the reaction of 2 (0.5 mM) with dioxygen in acetonitrile at 298 K. Inset: ESI-mass spectrum of the catechol-derived product, 4,6-di-tert-butyl-2-pyrone.
Figure S5. 1H NMR spectrum (500 MHz, CDCl3, 295 K) of organic products derived from 3,5-di-tert-butylcatechol after the reaction of 2 with dioxygen in acetonitrile. *-marked peaks are from solvents.
Figure S6. ESI-MS spectra of the catechol-cleavage product in the reaction with (a) 16O2 and (b) 18O2.
Figure S9. Optical spectral changes with time (time interval = 30 s) during the reaction of 2 (0.5 mM solution in acetonitrile and NH4OAc/AcOH buffer mixture (4:1) of pH = 5.5) with dioxygen at 298 K. Inset: plot of absorbance vs time.
Figure S10. Plot of turnover numbers (TON) vs equivalents of H2DBC added.
Figure S11. Time-dependent 1H NMR spectral plot and TON with time for complex 2 in acetonitrile-NH4OAc/AcOH buffer solution (pH = 5.5) at room temperature (*-marked peaks are from residual CHCl3 solvent).
Figure S12. Plot of TON vs reaction time for complex 2.
Figure S13. Optical spectrum of [(TACN)FeIII(DBC)(Cl)] (3) (concentration = 0.5 mM) in a mixture of CH3CN and NH4OAc/AcOH (4:1) buffer of pH = 5.5 at 298 K.
Figure S14. 1H NMR spectra (500 MHz, CDCl3, 295 K) of organic products derived from 3,5-di-tert-butylcatechol after the reaction of 3 with dioxygen in acetonitrile-NH4OAc/AcOH buffer solution (pH = 5.5) in the presence of (i) 100 eqv H2DBC, (ii) 20 eqv N-methyl imidazole and 100 eqv H2DBC, (iii) 1 eqv AgBF4 and 100 eqv H2DBC and (iv) 1 eqv AgBF4, 20 eqv N-methyl imidazole and 100 eqv H2DBC. *-marked peaks are from solvents.
Table S2. Percentage of organic products derived from 3,5-di-tert-butylcatechol after the reaction of 3 with dioxygen in acetonitrile-NH4OAc/AcOH buffer solution (pH = 5.5).
Experimental conditions H2DBC
(D)
Pyrone
(A)
Pyrone
(B)
Quinone
(C)
(i) 3 in CH3CN and NH4OAc/AcOH buffer (4:1) + 100 eqv H2DBC 10 % 5% 2% 83%
(ii) 3 in CH3CN and NH4OAc/AcOH buffer (4:1)+20 eqv N-methyl imidazole + 100 eqv H2DBC
12% 4% 2% 82%
(iii) 3 in CH3CN and NH4OAc/AcOH buffer (4:1) + 1 eqv AgBF4 + 100 eqv H2DBC
References: [1] G. R. Newkome, G. E. Kiefer, Y. A. Frere, M. Onishi, V. K. Gupta and F. R. Fronczek,
Organometallics, 1986, 5, 348. [2] APEX 2 v2.1–0, Bruker AXS, Madison, WI, 2006. [3] G. M. Sheldrick, SHELX97 Programs for Crystal Structure Analysis (Release 97-2), (1998) University of Göttingen, Germany.