Article
Inorganic Chemistry, Vol. 50, No. 4, 2011 1369
properties, a combined experimental and theoretical analysis
is often required to differentiate between the two possible
configurations.20 Short Fe-N distances and an unperturbed
macrocyclic scaffold in pentafluorophenyl and octaethyl
corroles support a Fe(IV)-corrole formulation.21-24 Subse-
quent studies have revised this view.20,25-29 Chemical shifts
Absorption spectral measurements were made on DCM
solutions of each compound using a Cary 5000 UV-vis-NIR
spectrometer from Varian employing the software Cary Wi-
nUV. Quartz cells with a 10 mm path length were used. Steady
state emission spectra were recorded on an automated Photon
Technology International (PTI) QM 4 fluorimeter equipped
with a 150-W Xe arc lamp and a Hamamatsu R928 photomul-
tiplier tube. Excitation light was wavelength selected with glass
filters. Solution samples for absorption and emission experi-
ments were prepared under ambient conditions in DCM and
contained in screw-cap quartz fluorescence cells. Lifetime mea-
surements were performed on THF solutions prepared under
nitrogen atmosphere and then subject to freeze-pump cycles.
10-(4-(5-Bromo-2,7-di-tert-butyl-9,9-dimethylxanthenyl))-5,
15-bis(tert-butyl-phenyl) Corrole (4a). Method 1. Bromoxanthene
aldehyde 1 (129 mg, 0.30 mmol) and 4-tert-butylphenyldipyrro-
methane 3a (209 mg, 0.75 mmol) were dissolved in 10 mL of DCM.
The condensation reaction commenced with the addition of 10 mL
of 1.3 mM solution of TFA in DCM followed by stirring at room
temperature for 7 h. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone
(DDQ, 170 mg, 0.75 mmol) was then added, and the reaction
mixture was stirred for an additional 15 min. The solution was
loaded directly onto a silica gel column and eluted with DCM,
and the first luminescent band was collected. Further purification
by column chromatography on silica was accomplished using
DCM/hexane (4:5). The resulting dark violet solid was suspended
in methanol, filtered and dried in vacuo (58 mg, 20% yield based
on 1). 1H NMR (500 MHz, CDCl3, 25ꢀC): δ=8.97 (d, J= 4.0 Hz,
2H), 8.89 (d, J = 5.0 Hz, 2H), 8.65 (s(br), 2H), 8.51 (d, J = 4.5 Hz,
2H), 8.35 (s(br), 4H), 8.04 (d, J = 2.5 Hz, 1H), 7.83 (d, J = 8.5 Hz,
4H), 7.80 (d, J = 2.5 Hz, 1H), 7.42 (d, J = 2.5 Hz, 1H), 7.10 (d, J =
2.5 Hz, 1H), 1.90 (s, 6H), 1.59 (s, 18H), 1.53 (s, 9H), 1.27 (s, 9H).
HR(ESI)-MS (MHþ) (M = C62H65N4OBr): Calcd m/z =
963.4429, found 963.4404. MS(MALDI-TOF) (Mþ): 962.45.
UV-vis, nm (ε ꢀ 10-3 M-1 cm-1): 421 (132), 568 (17), 617 (15),
1
of the H NMR signals, EPR spectra of reduced species,
magnetic susceptibility measurements, 57Fe Mossbauer spec-
€
troscopy, and theoretical calculations of corrolates support
the radical dianion state of the corrole macrocycle and an
intermediate-spin ferric center.
We report here the preparation of xanthene-modified
corroles (XC) and HCX macrocycles of iron and show that
these species possess a redox non-innocent XC and HCX
57
€
ligand. Fe Mossbauer spectroscopy in conjunction with
Density Functional Theory (DFT) calculations indicate that
these iron chloride xanthene corroles are best described as
[Fe(III)Cl-corroleþ•].20,30 The redox chemistry of iron chlo-
ride XC and HCX platforms has been exploited to drive the
catalytic dismutation of hydrogen peroxide. The turnover
frequency of the initial dismutation reaction indicates the
ease of the reduction of the high valent iron oxo corrole.
Experimental Section
General Methods. Silica gel for column chromatography was
obtained from Whatman Inc. (Silica Gel 60, 230-400 μm mesh).
All solvents (tetrahydrofuran (THF), toluene, dichloromethane
(DCM), dimethylformamide (DMF), hexane, and methanol)
and most starting materials were obtained from Sigma-Aldrich
and used without further purification. Compounds 1,12 2,12
3a-3c,31 5a,17 and 6a17 were prepared according to literature
procedures.
1H NMR spectra were recorded at ambient temperature on a
Varian Mercury 300 or 500 MHz spectrometer. All spectra were
referenced to tetramethylsilane (TMS) or deuterated chloro-
form (CDCl3) as an internal standard (measured values for δ are
given in parts per million (ppm) and for J in Hertz (Hz)).
Elemental analysis was performed by Midwest Microlab La-
boratories, Indiana. Electrospray ionization (ESI) mass spectra
were obtained using a Bruker Daltonics APEXIV 4.7 T FT-
ICR-MS instrument at the DCIF facility of MIT. Matrix-
assisted laser desorption/ionization-time of flight (MALDI-
TOF) spectra were recorded on a Bruker Omniflex instrument
with a reflectron accessory.
650 (14) in DCM. Anal. Calcd for C62H65N4OBr 0.5H2O: C, 76.68;
3
H, 6.85; N, 5.77. Found: C, 76.50; H, 6.90; N, 5.65.
10-(4-(5-Bromo-2,7-di-tert-butyl-9,9-dimethylxanthenyl))-5,
15-bismesityl corrole (4b). Method 1 was followed by using 3b
(198 mg, 0.75 mmol) in place of 3a. Two column chromatographs
(silica, ethylacetate/hexane = 1:25) afforded a violet solid, which
was washed with methanol and dried in vacuo to furnish a purple
solid (64 mg, 23% yield based on 1). 1H NMR (300 MHz, CDCl3,
25 ꢀC): δ = 8.87 (d, J = 4.2 Hz, 2H), 8.42 (m, 4H), 8.32 (d, J = 4.2
Hz, 2H), 8.00 (d, J = 2.4 Hz, 1H), 7.76 (d, J = 2.4 Hz, 1H), 7.37 (d,
J = 2.1 Hz, 1H), 7.25 (m, 4H), 7.03 (d, J = 2.1 Hz, 1H), 2.59 (s,
6H),1.99(s, 6H), 1.91(s, 6H), 1.86(s, 6H), 1.49(s, 9H), 1.23(s, 9H).
HR(ESI)-MS (MHþ) (M = C60H61N4OBr): Calcd m/z =
933.4102, found 933.3979. MS(MALDI/TOF) (Mþ): 932.57.
UV-vis, nm (ε ꢀ 10-3 M-1 cm-1): 409 (125), 424 (109), 567
(14), 603 (11), 634 (7) in DCM. Anal. Calcd for C60H61N4OBr: C,
77.15; H, 6.58; N, 6.00. Found: C, 76.91; H, 6.52; N, 5.86.
(20) Ye, S.; Tuttle, T.; Bill, E.; Simkhovich, L.; Gross, Z.; Thiel, W.;
Neese, F. Chem.;Eur. J. 2008, 14, 10839–10851.
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Gisselbrecht, J.-P.; Gross, M.; Vogel, E.; Kadish, K. M. Inorg. Chem. 1996,
35, 184–192.
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Inorg. Chem. 2000, 39, 2704–2705.
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5439.
10-(4-(5-Bromo-2,7-di-tert-butyl-9,9-dimethylxanthenyl))-5,15-
bis(pentafluorophenyl) corrole (4c). Method 1 was followed by using
3c (234 mg, 0.75 mmol) in place of 3a. Column chromatography
(silica, DCM/hexane = 1:2) afforded a dark purple solid, which
was washed with methanol and dried in vacuo (72 mg, 24% yield
based on 1). 1H NMR (500 MHz, CDCl3, 25 ꢀC): δ = 9.12 (d, J =
4.0Hz, 2H), 8.68(m, 4H), 8.57(s(br),2H), 8.02(d,J= 2.5 Hz, 1H),
7.85 (d, J=2.5 Hz, 1H), 7.40 (d, J=2.5 Hz, 1H), 7.06 (d, J=2.5 Hz,
1H), 1.89 (s, 6H), 1.54 (s, 9H), 1.24 (s, 9H). HR(ESI)-MS
(MHþ) (M=C54H39F10N4OBr): Calcd for m/z=1029.2220, found
1029.2242. MS(MALDI/TOF) (MHþ): 1030.37. UV-vis, nm (ε ꢀ
10-3 M-1 cm-1): 414 (134), 560 (21), 612 (12) in DCM. Anal. Calcd
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V.; Zimmer, B.; Kh. Shokhireva, T.; Walker, F. A. Inorg. Chim. Acta 2002,
339, 171–178.
€
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Walker, F. A.; Trautwein, A. X. J. Am. Chem. Soc. 2002, 124, 6636–6648.
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M. G. H.; Shokhireva, T. K.; Cai, S.; Walker, F. A. Inorg. Chem. 2005,
44, 7030–7046.
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for C54H39F10N4OBr H2O: C, 61.90; H, 3.94; N, 5.35. Found: C,
3
62.07; H, 3.91; N, 5.24.
General Synthesis of FeCl Corroles 8. Method 2. A solution
of 4 (0.15 mmol) and FeCl2 (380 mg, 3.00 mmol) in 20 mL of
dimethylformamide (DMF) was degassed with argon for 20 min.