Alkyl and aryl substituted corroles. 1. Synthesis and characterization of free base and cobalt containing derivatives. X-ray structure of (Me4Ph5Cor)Co(py)2

Article abstract of DOI:10.1021/ic010177+

The synthesis, spectroscopic properties, and electrochemistry of six different alkyl- and aryl-substituted Co(III) corroles are presented. The investigated compounds contain methyl, ethyl, phenyl, or substituted phenyl groups at the eight β-positions of the corrole macrocycle and four derivatives also contain a phenyl group at the 10-meso position of the macrocycle. Each cobalt corrole undergoes four reversible oxidations in CH₂Cl₂ containing 0.1 M tetra-n-butylammonium perchlorate and exists as a dimer in its singly and doubly oxidized forms. The difference in potential between the first two oxidations is associated with the degree of interaction between the two corrole units of the dimer and ranges from an upper value of 0.62 V, in the case of (Me₆Et₂Cor)Co, to a lower value of about 0.17 V, in the case of four compounds which have a phenyl group located at the 10-meso position of the macrocycle. These Co(III) corroles strongly coordinate two pyridine molecules or one carbon monoxide molecule in CH₂Cl₂ media, and ligand binding constants were evaluated using spectroscopic and electrochemical methods. The structure of (Me₄Ph₅Cor)Co(py)₂ was also determined by X-ray diffraction. Crystal data: (Me₄Ph₅Cor)Co(py)₂ ·3CH₂Cl₂·H₂O, orthorhombic, a = 19.5690(4) A, b = 17.1070(6) A, c = 15.9160(6) A, V = 5328.2(5) A³, space group Pna2₁, Z = 2, 35 460 observations, R(F) = 0.069.

Full text of DOI:10.1021/ic010177+

Inorg. Chem. 2001, 40, 4845-4855
4845
Alkyl and Aryl Substituted Corroles. 1. Synthesis and Characterization of Free Base and
Cobalt Containing Derivatives. X-ray Structure of (Me4Ph5Cor)Co(py)2
Roger Guilard,*,† Claude P. Gros,† Fre´de´ric Bolze,† Franc¸ois Je´roˆme,† Zhongping Ou,‡
Jianguo Shao,‡ Jean Fischer,§ Raymond Weiss,§ and Karl M. Kadish*,‡
LIMSAG UMR 5633, Faculte´ des Sciences Gabriel, Universite´ de Bourgogne, 6, Boulevard Gabriel,
21000 Dijon, France, Department of Chemistry, University of Houston, Houston, Texas 77204-5641,
and Institut Le Bel, Universite´ Louis Pasteur, 4 Rue Blaise Pascal, 67000 Strasbourg, France
ReceiVed February 9, 2001
The synthesis, spectroscopic properties, and electrochemistry of six different alkyl- and aryl-substituted Co(III)
corroles are presented. The investigated compounds contain methyl, ethyl, phenyl, or substituted phenyl groups
at the eight â-positions of the corrole macrocycle and four derivatives also contain a phenyl group at the 10-meso
position of the macrocycle. Each cobalt corrole undergoes four reversible oxidations in CH2Cl2 containing 0.1 M
tetra-n-butylammonium perchlorate and exists as a dimer in its singly and doubly oxidized forms. The difference
in potential between the first two oxidations is associated with the degree of interaction between the two corrole
units of the dimer and ranges from an upper value of 0.62 V, in the case of (Me6Et2Cor)Co, to a lower value of
about 0.17 V, in the case of four compounds which have a phenyl group located at the 10-meso position of the
macrocycle. These Co(III) corroles strongly coordinate two pyridine molecules or one carbon monoxide molecule
in CH2Cl2 media, and ligand binding constants were evaluated using spectroscopic and electrochemical methods.
The structure of (Me4Ph5Cor)Co(py)2 was also determined by X-ray diffraction. Crystal data: (Me4Ph5Cor)Co-
(py)2·3CH2Cl2·H2O, orthorhombic, a ) 19.5690(4) Å, b ) 17.1070(6) Å, c ) 15.9160(6) Å, V ) 5328.2(5) Å3,
space group Pna21, Z ) 2, 35 460 observations, R(F) ) 0.069.
Introduction
in cleavage of the 1,19-direct pyrrole-pyrrole bond.6-8 Interest-
ingly, and in contrast to what is observed in porphyrin systems,
A number of different corroles and metallocorroles have now
been synthesized. These include the well-known octaethyl- and
octamethylcorroles as well as several derivatives with mixed
ethyl and methyl substituents at the eight â-pyrrole positions
of the macrocycle.1,2 Corroles containing meso-substituted C6H5,
C6F5, or C6H4X groups where X is an electron-donating or
electron-withdrawing substituent are also known.3-6
The 5- or 10-phenyl substituted corroles with alkyl substit-
uents in the â-pyrrole positions often exhibit a reduced stability
in solution; these compounds undergo an oxidative ring opening
when left in solution in the presence of air and light and are
converted to the corresponding biliverdin among other decom-
position products.6 However, the introduction of aryl groups at
the 2, 3, 17, and 18 â-pyrrole positions of the corrole macrocycle
helps to prevent oxidative attack of the ring which would result
steric crowding about the periphery of a corrole macrocycle does
not prevent the corrole from retaining a planar conformation as
was demonstrated in the case of a cobalt(III) meso-phenyl
substituted complex.9
A recent electrochemical study of (Et8Cor)M where M ) Co,
Cu, or Ni showed the formation of singly and doubly oxidized
dimers upon the abstraction of one or two electrons in CH2Cl2
and other noncoordinating media.10 The interaction between the
two corrole units in the oxidized (Et8Cor)M complexes will
depend on the specific metal ion and its oxidation state as well
as upon the degree of coordination of the metal ion. It should
also depend on the specific substituents on the corrole macro-
cycle, but no report of dimer formation from monomeric
metallocorroles has ever appeared for complexes other than
those having an (Et8Cor)M structure. Thus, to examine the
influence of peripheral crowding on the chemistry, electro-
chemistry, and dimerization of other related corroles, we have
synthesized a series of derivatives with phenyl and anisyl
substituents at the 2, 3, 10, 17, and 18 â-pyrrole positions of
the corrole macrocycle. These compounds, which are described
in the present paper, are shown in Chart 1. This paper also
reports the ligand binding properties of each cobalt corrole in
† Universite´ de Bourgogne.
‡ University of Houston.
§ Universite´ Louis Pasteur.
(1) Paolesse, R. In The Porphyrin Handbook; Kadish, K. M., Smith, K.
M., Guilard, R., Eds.; Academic Press: San Diego, CA, 2000; Vol.
2, pp 201-232.
(2) Erben, C.; Will, S.; Kadish, K. M. In The Porphyrin Handbook;
Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: San
Diego, CA, 2000; Vol. 2, pp 233-300.
(3) Adamian, V. A.; D’Souza, F.; Licoccia, S.; Di Vona, M. L.; Tassoni,
E.; Paolesse, R.; Boschi, T.; Kadish, K. M. Inorg. Chem. 1995, 34,
532-540.
(7) Je´roˆme, F.; Gros, C. P.; Tardieux, C.; Barbe, J.-M.; Guilard, R. Chem.
Commun. 1998, 2007-2008.
(8) Je´roˆme, F.; Gros, C. P.; Tardieux, C.; Barbe, J.-M.; Guilard, R. New
J. Chem. 1998, 22, 1327-1329.
(4) Gross, Z.; Simkhovich, L.; Galili, N. Chem. Commun. 1999, 599-
600.
(9) Paolesse, R.; Licoccia, S.; Bandoli, G.; Dolmella, A.; Boschi, T. Inorg.
Chem. 1994, 33, 1171-1176.
(5) Simkhovich, L.; Galili, J.; Saltsman, I.; Goldberg, I.; Gross, Z. Inorg.
Chem. 2000, 39, 2704-2705.
(6) Tardieux, C.; Gros, C. P.; Guilard, R. J. Heterocycl. Chem. 1998, 35,
965-970.
(10) Kadish, K. M.; Adamian, V. A.; Van Caemelbecke, E.; Gueletii, E.;
Will, S.; Erben, C.; Vogel, E. J. Am. Chem. Soc. 1998, 120, 11986-
11993.
10.1021/ic010177+ CCC: $20.00 © 2001 American Chemical Society
Published on Web 09/04/2001

4846 Inorganic Chemistry, Vol. 40, No. 19, 2001
Guilard et al.
Equilibrium Measurements. The binding of pyridine to each
Co(III) corrole was carried out in CH2Cl2 and the room temperature
(296 K) reaction monitored by UV-visible spectroscopy. The absor-
bance data were then fitted to the Hill equation:13
Chart 1
log((Ai - A0)/(Af - Ai)) ) log K + p log [py]
(1)
where Ai ) absorbance at a specific concentration of pyridine; A0 )
initial absorbance where [py] ) 0, and Af ) final absorbance where
the fully ligated corrole is the only species present. Values of log K
were obtained from the intercept of the regression line in a plot of
log((Ai - A0)/(Af Ai)) vs log [py]. The slope, p, should be equal to
-
the number of axially coordinated ligands. The concentration of the
corroles for these measurements was 5 × 10-6 M, and that of pyridine
was in the range of 10-5 to 0.5 M.
A calibrated gas tight syringe was used to introduce CO into solutions
of CH2Cl2. The pressure of CO within the gas tight syringe (Pinjected
)
was read from the barometer before each injection. The volume of the
titration vessel above the solution (Vvessel) was 175 mL. Thus, by
systematically injecting into the vessel a known volume (Vinjected) of
CO gas, we were able to calculate the partial pressure of CO (PCO) at
each step in the titration as being equal to (Vinjected/Vvessel)Pinjected. The
vessel was vigorously shaken for 3 min after introducing CO to ensure
equilibrium before recording each UV-visible spectrum at a given
partial pressure of CO, and the Hill equation was used to analyze the
data as a function of CO partial pressure. P1/2CO, the pressure of CO
when the ligand binding reaction had proceeded halfway, was used to
represent the formation constant. The solubility coefficient of CO in
CH2Cl2 was taken as 6.7 × 10-3 M/atm,14 and this value was used to
calculate the formation constant, K.
Chemicals and Reagents. Basic alumina (Merck; usually Brock-
mann Grade III, i.e. deactivated with 6% water) was used for column
chromatography. Absolute dichloromethane (CH2Cl2) was obtained from
Fluka Chemical Co. and used as received. Tetra-n-butylammonium
perchlorate (TBAP, Fluka Chemical Co.) was twice recrystallized from
absolute ethanol and dried in a vacuum oven at 40 °C for a week prior
to use.
CH2Cl2, and these data serve as the basis for understanding the
ligand binding and electrochemical reactions of related linked
bis-corroles whose synthesis and properties are described in the
following paper in this issue.11 In addition, an X-ray structure
of one complex, (Me4Ph5Cor)Co(py)2, is presented.
2,3,7,13,17,18-Hexamethyl-8,12-diethylcorrole (1),15-17 7,13-di-
methyl-8,12-diethyl-2,3,17,18-tetraphenylcorrole (2),6 5,5′-dicarboxy-
3,3′,4,4′-tetramethyldipyrryltoluene (3),16 3,4-diethyl-2-formylpyrrole
(4),15 ethyl 4-methyl-3-phenyl-1H-pyrrole-2-carboxylate (5),8 3,4-di-
(p-anisil)pyrrole (7b)7 were synthesized as described in the literature.
3,4-Di(m-anisyl)pyrrole-2,5-dicarboxylic Acid (6a). Sodium (14
g) was dissolved in 150 mL of absolute methanol under an atmosphere
of nitrogen in a 500 mL three-necked flask equipped with a nitrogen
inlet and reflux condenser. The solution was cooled to room temper-
ature, and 12 g of dimethyl N-acetyliminodiacetate (0.06 mol) dissolved
in 50 mL of dry methanol was added to the sodium methoxide solution
while the mixture was being stirred by means of a mechanical stirrer.
Solid 3,3′-dimethoxybenzyl (11 g, 0.040 mol) was then added in
fractions. Stirring was continued at room temperature until all of the
3,3′-dimethoxybenzyl was dissolved. The reaction mixture was slowly
heated to the boiling point, then refluxed for 4 h, and poured into 1 L
of cold water after which the unreacted 3,3′-dimethoxybenzyl (yellow
precipitate) was filtered off. The cooled aqueous solution was extracted
four times to remove any trace of dissolved 3,3′-dimethoxybenzyl. The
dissolved ether and methanol were evaporated, and 200 mL of 10%
sodium hydroxyde solution was added. The reaction mixture was then
refluxed for 1 h, cooled in an ice bath, and acidified to pH 1.0 with
cold 6 M HCl. The precipitated pyrrole was filtered off immediately
and recrystallized from methanol-water (1:1) to give 1.5 g (22% yield)
of 6a as brown solid. 1H NMR (DMSO): δ 12.70 (s, 2H, acid), 11.91
Experimental Section
Instrumentation. 1H NMR spectra were recorded on a Bruker AC
200 Fourier transform spectrometer at the Centre de Spectrome´trie
Mole´culaire de l’Universite´ de Bourgogne. Chemical shifts are ex-
pressed in parts per million relative to chloroform (7.258 ppm).
Microanalyses were performed at the Universite´ de Bourgogne on a
Fisons EA 1108 CHNS instrument. UV-visible spectra were recorded
on a Varian Cary 1 spectrophotometer or on an HP 8453 UV-visible
spectrophotometer in the case of spectroelectrochemistry. Mass spectra
were obtained with a Kratos Concept 32 S spectrometer in EI mode.
Cyclic voltammetry was carried out with an EG&G model 173
potentiostat. A three-electrode system was used and consisted of a glassy
carbon or platinum disk working electrode, a platinum wire counter
electrode, and a saturated calomel electrode (SCE) as the reference
electrode. The SCE was separated from the bulk of the solution by a
fritted-glass bridge of low porosity which contained the solvent/
supporting electrolyte mixture. All potentials are referenced to the SCE.
Cyclic voltammetry under different CO partial pressures was carried
out in a sealed cell. UV-vis spectroelectrochemical experiments were
performed with a home-built platinum thin-layer cell of the type
described in the literature.12 Potentials were applied and monitored with
an EG&G Princeton Applied Research model 173 potentiostat.
Infrared spectra were recorded on an FTIR Nicolet Magna-IR 550
spectrometer. The background was obtained by recording the IR
spectrum of CH2Cl2 saturated by CO, and the IR spectrum of the
compound under CO was obtained after bubbling CO through the
solution.
(13) Ellis, J., P. E.; Linard, J. E.; Szymanski, T.; Jones, R. D.; Budge, J.
R.; Basolo, F. J. Am. Chem. Soc. 1980, 102, 1889-1896.
(14) Rougee, M.; Brault, D. Biochemistry 1975, 14, 4100-4106.
(15) Barton, D. H. R.; Kervagoret, J.; Zard, S. Z. Tetrahedron 1990, 46,
7587-7598.
(16) Conlon, M.; Johnson, A. W.; Overend, W. R.; Rajapaksa, D. J. Chem.
Soc., Perkin Trans. 1 1973, 2281-2288.
(17) Hitchcock, P. B.; McLaughlin, G. M. J. Chem. Soc., Dalton Trans.
1976, 1927-1930.
(11) Guilard, R.; Je´roˆme, F.; Gros, C. P.; Barbe, J.-M.; Ou, Z.; Shao, J.;
Fischer, J.; Weiss, R.; Kadish, K. M. Inorg. Chem. 2001, 40, 4856-
4865.
(12) Lin, X. Q.; Kadish, K. M. Anal. Chem. 1985, 57, 1498-1501.

Alkyl and Aryl Substituted Corroles
Inorganic Chemistry, Vol. 40, No. 19, 2001 4847
(s, 1H, NH), 7.12 (dd, 2H, J1 ) J2 ) 5.6 Hz, 5-anis.), 6.76 (d, 2H, J
) 5.6 Hz, 6-anis.), 6.73 (d, 2H, J ) 5.6 Hz, 4-anis.), 6.67 (s, 2H,
2-anis.), 3.63 (s, 6H, OMe). IR: ν 1675 cm-1 (CO). MS (EI): m/z (%)
367 (100) [M]+, 323 [M - CO2]+., 305 [M - 2OMe]+., 279 [M -
2CO2]+.. Anal. Calcd for C20H17NO6,H2O: C, 62.32; H, 4.97; N, 3.64.
Found: C, 62.34; H, 5.17; N, 3.57.
and the resulting orange solution was stirred for 10 min at room
temperature. 3,4-Diphenyl-2-formylpyrrole (4) (7.0 g, 28.3 mmol) in
methanol (500 mL) was added dropwise, and the red solution was stirred
for 15 min. Evaporation of the solvent led to a green solid which was
not further purified and used as a crude compound in the next reaction.
a,c-Biladiene, previously obtained, was dissolved in methanol (1.00
L) saturated with sodium hydrogen carbonate and stirred at room
temperature for 10 min. p-Chloranil (4.3 g) was then added, and the
solution stirred for 15 min after which 43 mL of 50% hydrazine in
water was added. After 15 min, the solvent was evaporated under
vacuum to give a crude solid. The latter was redissolved in methylene
chloride, washed with water, and dried with magnesium sulfate.
Chromatography on basic alumina (methylene chloride elution) afforded
the title product 7 (m ) 932 mg, 12.7%), which corresponds to the
first purple eluted compound. 1H NMR (CDCl3): δ 9.32 (s, 2H, meso
5, 15), 6.96-7.78 (m, 25H, Ph), 3.14 (s, 6H, Me), 2.21 (s, 6H, Me).
UV-vis (CH2Cl2; λmax, nm (ꢀ, L mol-1 cm-1)): 419 (85 000), 567
(15 000), 607 (13 000), 640 (7000). MS (EI): m/z (%) 734 (100) [M]+..
Anal. Calcd for C53H42N4: C, 86.61; H, 5.76, N, 7.63. Found: C, 86.25;
H, 6.01; N, 7.60.
2,3,17,18-Tetra(m-anisyl)-7,8,12,13-tetramethyl-9-phenylcor-
role (Me4PhTm-OCH3PCor)H3 (9). This corrole was similarly pre-
pared in 9% yield (m ) 105 mg) from 3 (m ) 570 mg, 1.56 mmol)
and 6c (m ) 1.0 g, 3.2 mmol). 1H NMR (CDCl3): δ 9.40 (s, 2H, meso
5, 15), 7.93 (d, 2H, J ) 6 Hz, 2,6-Ph), 7.69 (m (dd+s), 2H, 3,4,5-Ph),
7.49 (d, 2H, J ) 5 Hz, 4-anis.), 7.30 (d, 2H, J ) 3 Hz, 4-anis.), 7.11
(d, 2H, J ) 6 Hz, 6-anis.), 6.99 (m, 8H, 6-anis., 5-anis., 2 × 2-anis.),
6.59 (dd, 2H, J ) 3 and 6 Hz, 5-anis.), 3.74 (s, 6H, OMe), 3.62 (s, 6H,
OMe), 3.18 (s, 6H, Me), 2.23 (s, 6H, Me). UV-vis (CH2Cl2; λmax, nm
(ꢀ, L mol-1 cm-1)): 410 (63 000), 422 (71 000), 535 (13 000), 566
(16 000), 607 (14 000), 638 nm (8000). MS (EI): m/z (%) 854 (100)
[M]+. . Anal. Calcd for C57H50N4O4, MeOH: C, 78.52; H, 6.14; N, 6.32.
Found: C, 79.00; H, 6.51; N, 6.36.
3,4-Di(m-anisyl)pyrrole (6b). A 3.0 g (8.2 mmol) amount of the
diacid derivative 6a was refluxed under argon in 75 mL of freshly
distilled ethanolamine for 4 h. The hot ethanolamine solution was then
poured into 200 mL of cold water and the aqueous solution extracted
four times with 100 mL of methylene chloride. The combined organic
layers were thoroughly washed with water in order to remove any trace
of ethanolamine and then dried over magnesium sulfate. Evaporation
of the solvent led to a crude solid which was recrystallized from
methylene chloride-cyclohexane (1:1) to give 1.0 g of 6b as a brown
solid (yield 44%). 1H NMR (CDCl3): δ 8.38 (s, 1H, NH), 7.18 (d, 2H,
J ) 7 Hz, 6-anis.), 6.94 (s, 2H, 2-anis.), 6.91 (d, 2H, J ) 2.4 Hz,
4-anis.), 6.88 (d, 2H, J ) 2 Hz, R-free), 6.78 (dd, 2H, J ) 2.4 and 7
Hz, 5-anis.), 3.70 (s, 6H, OMe). MS (EI): m/z (%) 279 (100) [M]+..
Anal. Calcd for C18H17NO2: C, 77.38; H, 6.14; N, 5.02. Found: C,
77.48; H, 6.23; N, 5.32.
2-Formyl-3,4-di(m-anisyl)pyrrole (6c). In a typical experiment, 3,4-
di(m-anisyl)pyrrole 6b (2.1 g, 7.5 mmol) was dissolved, under argon
and with shielding from light, in 100 mL of dry dimethylformamide
(DMF). The solution was cooled to 0 °C by using an ice-water bath,
and 4 mL of freshly distilled POCl3 (43 mmol) was then slowly added.
After addition, the stirring was kept at room temperature for 3 h after
which the reaction mixture was poured into a 10% aqueous sodium
hydroxyde solution (200 mL). The reaction mixture was refluxed for
1 h (under nitrogen), and the brown precipitate thus obtained was filtered
off and washed thoroughly with water. Recrystallization from methanol
led to 6c as a brown solid (1.6 g, yield 69%).1H NMR (CDCl3): δ
9.94 (s, 1H, NH), 9.45 (s, 1H, CHO), 7.10-7.30 (m, anis.), 6.79-6.91
(m, anis.), 6.69 (d, 1H, R free), 3.71 (s, 3H, OMe), 3.62 (s, 3H, OMe).
MS (EI): m/z (%) 307 (100) [M]+., 279 [M - CHO]+. Anal. Calcd for
C19H17NO3: C, 74.24; H, 5.58; N, 4.56. Found: C, 73.75; H, 5.57; N,
4.64.
2,3,17,18-Tetra(p-anisyl)-7,8,12,13-tetramethyl-9-phenylcorrole
(Me4PhTp-OCH3PCor)H3 (10). This corrole was similarly prepared
in 20% yield (m ) 450 mg) from 3 (m ) 1.0 g, 2.74 mmol) and 7c (m
1
) 1.7 g, 5.5 mmol). H NMR (CDCl3): δ 9.31 (s, 2H, meso 5, 15),
2-Formyl-3,4-di(p-anisyl)pyrrole (7c). The title compound was
prepared from 7b (3.0 g, 10 mmol) using the above procedure described
for 6c (m ) 2.0 g, yield 72%). 1H NMR (CDCl3): δ 9.93 (s, 1H, NH),
9.40 (s, 1H, CHO), 7.20 (d, 2H, J ) 8.8 Hz, 2,6-anis.), 7.17 (d, 1H, J
) 2.9 Hz, R-free), 7.07 (d, 2H, J ) 8.8 Hz, 2,6-anis.), 6.87 (d, 2H, J
) 8.8 Hz, 3,5-anis.), 6.77 (d, 2H, J ) 8.8 Hz, 3,5-anis.), 3.82 (s, 3H,
OMe), 3.77 (s, 3H, OMe). IR: ν 1639 cm-1 (CO). MS (EI): m/z (%)
307 [M]+. (100). Anal. Calcd for C19H17NO3: C, 74.24; H, 5.58; N,
4.56. Found: C, 74.11; H, 5.32; N, 4.44.
7.95 (d, 2H, J ) 5 Hz, 2,6-Ph), 7.77 (dd, 2H, J ) 4 and 5 Hz, 3,5-Ph),
7.67 (d, 1H, J ) 4 Hz, 4-Ph), 7.37 (d, 4H, J ) 8.5 Hz, 2,6-anis.), 7.12
(d, 4H, J ) 9.1 Hz, 2,6-anis.), 6.95 (d, 4H, J ) 8.5 Hz, 3,5-anis.), 6.53
(d, 4H, J ) 9.1 Hz, 3,5-anis.), 3.95 (s, 6H, OMe), 3.79 (s, 6H, OMe),
3.15 (s, 6H, Me), 2.22 (s, 6H, Me). UV-vis (CH2Cl2; λmax, nm (ꢀ, L
mol-1 cm-1)): 413 (70 000), 422 (73 000), 520 (16 000), 559 (16 000),
609 (13 000), 638 nm (8000). MS (EI): m/z (%) 854 (100) [M]+.. Anal.
Calcd for C57H50N4O4, MeOH: C, 78.52; H, 6.14; N, 6.32. Found: C,
78.22; H, 5.92; N, 6.56.
5,5′-Dicarboxy-3,3′-dimethyl-4,4′-diphenyldipyrryltoluene (11b).
Benzaldehyde (1.70 g, 16 mmol) and pyrrole 5 (7.35 g, 32 mmol)
were dissolved in absolute ethanol (170 mL). The mixture was refluxed
under nitrogen, and 2.5 mL of concentrated HCl (12 M) was then added
to the solution. The reflux was maintained for 1 h, and the reaction
mixture was then evaporated on a rotary evaporator. During evaporation,
a white solid precipitated which was further filtered off. The solid thus
obtained was washed 3 times with cold methanol and dried. This diethyl
ester derivative 11a was not further purified and was used directly in
the saponification step (4.4 g, yield 50.3%). 1H NMR (CDCl3): δ 9.32
(s, 2H, NH), 7.21-7.36 (m, 15H, Ph), 5.69 (s, 1H, CH), 4.00 (q, 4H,
O-CH2), 1.83 (s, 6H, Me), 0.99 (t, 6H, CH3). MS (EI): m/z (%) 545
(100) [M]+..
8,12-Dimethyl-2,3,7,10,13,17,18-heptaphenylcorrole (Me2Ph7Cor)-
H3 (12). This corrole was similarly prepared in 11.2% yield (m ) 285
mg) from 11b (m ) 1.584 g, 3.23 mmol) and 4 (m ) 1.58 g, 6.39
1
mmol). H NMR (CDCl3): δ 9.32 (s, 2H, meso 5, 15), [6.62-7.85]
(m, 35H, Ph), 3.05 (s, 6H, Me). UV-vis (CH2Cl2; λmax, nm (ꢀ, L mol-1
cm-1)): 418 (62 000), 426 (62 000), 567 (15 000), 611 (12 000). MS
(EI): m/z (%) 858 (100) [M]+.. Anal. Calcd for C63H46N4, MeOH: C,
86.25; H, 5.66; N, 6.29. Found: C, 86.51; H, 5.91; N, 6.53.
Synthesis of Cobalt Derivatives. Synthesis of the various cobalt
corroles was carried out as described below:
(8,12-Diethyl-7,13-dimethyl-2,3,17,18-tetraphenylcorrolato)-
cobalt(III), (Me2Et2Ph4Cor)Co (14). A solution of 50 mg (0.058
mmol) of (Me2Et2Ph4Cor)H3 (2) and 120 mg of Co(OAc)2‚4H2O in 40
mL of dimethylformamide was heated under argon at 50 °C for 10
min. The solvent was then evaporated in a vacuum, and the residue
was passed through a column of alumina using methylene chloride as
eluent. After crystallization from methylene chloride-methanol (1:1),
the title compound was obtained in 20% yield (11 mg). UV-vis (CH2-
Cl2; λmax, nm (ꢀ, L mol-1 cm-1)): 394 (66 000), 526 (15 000). MS
(EI): m/z (%) 742 (100) [M]+.. Anal. Calcd for C49H39N4Co, MeOH:
C, 77.49; H, 5.60; N, 7.23. Found: C, 77.39; H, 5.48; N, 7.47.
(7,8,12,13-Tetramethyl-2,3,10,17,18-pentaphenylcorrolato)-
cobalt(III), (Me4Ph5Cor)Co (15). This corrole was similarly pre-
pared in 20% yield from 50 mg of (Me4Ph5Cor)H3 (8) and 120 mg of
Co(OAc)2‚4H2O. UV-vis (CH2Cl2; λmax, nm (ꢀ, L mol-1 cm-1)): 398
To a suspension of 4.3 g of the previously obtained triphenyldipyr-
romethane 11a in absolute ethanol (200 mL) was added 1.8 g of sodium
hydroxide dissolved in 10 mL of water. The reaction mixture was
refluxed under argon, shielded from light for 4 h, and then cooled to
room temperature. Acetic acid (500 mL) was then added until
precipitation of a pink powder. The resulting solid was filtered, washed
several times with water, and dried to give the title product 11b (2.6 g,
1
yield 67%). H NMR (CDCl3): δ 10.23 (s, 2H, COOH), 8.85 (s, 2H,
NH), 7.14-7.43 (m, 15H, Ph), 5.70 (s, 1H, CH), 1.94 (s, 6H, Me).
7,8,12,13-Tetramethyl-2,3,10,17,18-pentaphenylcorrole (Me4Ph5-
Cor)H3 (8). 5,5′-Dicarboxy-4,4′-diethyl-3,3′-dimethyldipyrryltoluene (3)
(4.72 g, 12.9 mmol) was dissolved in trifluoroacetic acid (200 mL)

4848 Inorganic Chemistry, Vol. 40, No. 19, 2001
Guilard et al.
(45 000), 529 (11 000). MS (EI): m/z (%) 789 (100) [M]+.. Anal. Calcd
for C53H39N4Co, MeOH: C, 78.81; H, 5.27; N, 6.81. Found: C, 78.87;
H, 5.26; N, 6.60.
Scheme 1
(2,3,17,18-Tetra(m-anisyl)-7,8,12,13-tetramethyl-9-phenylcorro-
lato)cobalt(III) (Me4PhTm-OCH3PCor)Co (16). This corrole was
similarly prepared in 31% yield from 50 mg of (Me4PhTm-OCH3PCor)-
H3 (9) and 120 mg of Co(OAc)2‚4H2O. UV-vis (CH2Cl2; λmax, nm (ꢀ,
L mol-1 cm-1)): 404 (52 000), 533 (17 000). MS (EI): m/z (%) 909
(100) [M]+.. Anal. Calcd for C57H47N4O4Co, MeOH: C, 73.88; H, 5.41;
N, 5.94. Found: C, 73.80; H, 5.74; N, 5.72.
(2,3,17,18-Tetra(p-anisyl)-7,8,12,13-tetramethyl-9-phenylcorro-
lato)cobalt(III) (Me4PhTp-OCH3PCor)Co (17). This corrole was
similarly prepared in 31% yield from 200 mg of (Me4PhTp-OCH3-
PCor)H3 (10) and 480 mg of Co(OAc)2‚4H2O. UV-vis (CH2Cl2; λmax
,
nm (ꢀ, L mol-1 cm-1)): 398 (59 000), 533 (16 000). MS (EI): m/z
(%) 909 (100) [M]+.. Anal. Calcd for C57H47N4O4Co, MeOH: C, 73.88;
H, 5.41; N, 5.94. Found: C, 74.33; H, 5.44; N, 6.12.
(8,12-Dimethyl-2,3,7,10,13,17,18-heptaphenylcorrolato)-
cobalt(III) (Me2Ph7Cor)Co (18). This corrole was similarly pre-
pared in 21% yield from 100 mg of (Me2Ph7Cor)H3 (12) and 250 mg
of Co(OAc)2‚4H2O. UV-vis (CH2Cl2; λmax, nm (ꢀ, L mol-1 cm-1)):
406 (53 000), 538 (14 000). MS (EI): m/z (%) 911 (100) [M]+.. Anal.
Calcd for C57H47N4Co, MeOH: C, 81.33; H, 4.80; N, 5.93. Found: C,
81.57; H, 5.12; N, 6.23.
Crystallographic Determination of (Me4Ph5Cor)Co(py)2. Single
crystals of (Me4Ph5Cor)Co(py)2‚3CH2Cl2‚H2O suitable for X-ray dif-
fraction were obtained by slow diffusion of methanol into a concentrated
dichloromethane solution of 15 containing a few drops of pyridine.
Data were collected on a Nonius KappaCCD diffractometer at -100
°C using Mo-KR graphite monochromated radiation (λ ) 0.7107 Å),
φ scans. The structure was solved using direct methods and refined
against |F|. For all computations the OpenMoleN package18 was used.
Crystal Data for (Me4Ph5Cor)Co(py)2‚3CH2Cl2‚H2O. Dark red
crystals, crystal dimensions 0.20 × 0.15 × 0.10 mm: C129H106Cl6-
Co2N12O ) 2(C63H49CoN6)‚3CH2Cl2‚H2O, M ) 2170.95, orthorhombic,
space group Pna21,
a ) 19.5690(4) Å, b ) 17.1070(6) Å,
c ) 15.9160(6) Å, V ) 5328.2(5) Å3, Z ) 2, Dc ) 1.35 g cm-3, µ(Mo-
KR) ) 0.522 mm-1. A total of 35 460 reflections were collected,
2.5° < θ < 30.5°, 4791 independent reflections having I > 3σ(I), 693
parameters. One of the three CH2Cl2 molecules is disordered with a
water molecule. All non-hydrogen atoms were refined anisotropically.
The hydrogen atoms, with the exception of CH2Cl2 and water protons,
intermediate was not isolated and used as obtained in the
cyclization reaction, this later step being carried out by the in-
situ addition of sodium hydrogen carbonate and p-chloranil,
followed by addition of 50% hydrazine in water. The crude
corroles were further purified by column chromatography after
solvent removal.
Heptaphenyl corrole, 12, was similarly prepared except that
its synthesis required a symmetrical triphenyldipyrromethane,
11b, which was first obtained by acid-catalyzed condensation
of 5 with benzaldehyde (Scheme 3). The asymmetrical ethyl
4-methyl-3-phenyl-1H-pyrrole-2-carboxylate (5) was synthe-
sized as described in the literature20 by base-catalyzed conden-
sation of nitroethane to benzaldehyde, followed by subjecting
the resulting phenylnitropropene derivative to the Barton-Zard
pyrrole synthesis conditions (CNCH2CO2Et, THF, PriOH,
DBU).15
were introduced as fixed contributors (dC-H ) 0.95 Å, BH ) 1.3Bequ
-
(C) Å2). The absolute structure was determined by refining Flack’s x
parameter. Final results R(F) ) 0.069, Rw(F) ) 0.083, GOF ) 1.488,
maximum residual electronic density 0.971 e Å-3. Data for this structure
have been deposited with the Cambridge Crystallographic Data Centre
as Supplementary publication no. CCDC-168247.
Results and Discussion
Synthesis of Aryl Substituted Corroles. The synthesis of
3,4-di(phenyl)- and 3,4-di(p-anisyl)pyrroles was performed as
described in the literature starting from benzyl and dimethyl
N-acetyliminodiacetate in the presence of sodium methoxide,
followed by decarboxylation in refluxing ethanolamine.19
A
The isolated yield of the sterically hindered arylcorroles
ranges from 10 to 12.5% except for 9 which was isolated in
9% yield; the low yield observed in the case of 9 may suggest
steric hindrance of the m-methoxy group in the cyclization step.
The proton NMR spectra of the free base corroles 8-10 and
12 show a singlet corresponding to the meso protons between
9.30 and 9.40 ppm, whereas the aryl groups (phenyl and anisyl)
appear as multiplets in the range of 6.50-7.93 ppm. The methyl
groups resonate as a singlet at 2.22 ppm.
similar procedure was used to access the 3,4-di(m-anisyl)pyrrole,
6a. Standard Vilsmeier-Haack formylation of 3,4-di(aryl)-
pyrrole 6b or 7b with 1 equiv of Vilsmeier reagent (POCl3/
DMF), followed by recrystallization, resulted in the isolation
of 2-formylpyrroles 6c and 7c in 69 and 72% yield, respectively
(Scheme 1).
The free base aryl substituted corroles 8-10 were obtained
in only two steps by condensation of 2 equiv of the correspond-
ing formylpyrrole (4, 6c, or 7c) with 5-phenyldipyrromethane
(3) as described in Scheme 2. The a,c-biladiene formed as an
Mass spectra exhibit similar characteristics for each free base
derivative. The parent peak corresponds in all cases to the
(18) OpenMoleN, InteractiVe Structure Solution; Nonius B. V.: Delft, The
Nederlands, 1997.
(19) Friedman, M. J. Org. Chem. 1965, 30, 859-863.
(20) Dumoulin, H.; Rault, S.; Robba, M. J. Heterocycl. Chem. 1997, 34,
13-16.

Alkyl and Aryl Substituted Corroles
Inorganic Chemistry, Vol. 40, No. 19, 2001 4849
Scheme 2
Scheme 3
molecular ion [M]•+. The Soret bands of the phenyl substituted
derivatives are red-shifted as compared to the well-known free
base (Me6Et2Cor)H3, 1, due to the ring current decrease
generated by the phenyl substituents (see Table 1).
3CH2Cl2‚H2O and details of the diffraction data collection are
given in Table 2. Selected bond distances and angles found in
(Me4Ph5Cor)Co(py)2 are given in Table 3.
The six-coordinate, low-spin central cobalt atom is bound to
six nitrogen atoms, four pyrrole nitrogens Np belonging to the
corrole ring and two axial pyridine-nitrogens Npy (Figure 1).
The four Co-Np bond lengths range from 1.884(6) to 1.915(6)
Å, leading to an average bond distance of 1.894(6) Å. Although,
not significantly different from the other Co-Np bond distances,
the two shortest Co-Np bond lengths of 1.884(6) and 1.886(6)
Å correspond to the Co-Np bonds involving the two Np atoms
belonging to the two pyrrole rings linked directly via a CR-CR
bond. Similar features have been previously observed in the
structures of other metallocorroles.1,2 The average value of the
two axial Co-Npy bond distances (1.991(7) Å) is slightly longer
than the mean value of the four Co-Np distances (1.894(6) Å).
These Co-Np and axial Co-Npy bond distances are significantly
shorter than the corresponding ones present in the low-spin, six-
coordinate cobalt(III) bis-piperidine complex, [(TPP)Co(pip)2]+,
where the average Co-Np and Co-Npip bond distances are
The metallocorroles 13-18 (see Chart 1) were synthesized
according to literature procedures7,16,17,21 which involved reac-
tion of cobalt(II) acetate tetrahydrate with the corresponding
free base corrole in DMF at 50 °C, the metalation reaction in
this case being monitored by UV-visible spectroscopy. The
reaction was complete within 10-15 min as indicated by
disappearance of the characteristic free base absorption at 591-
611 nm (see Table 1). The isolated yields of the cobalt corroles
varied from 20 to 31%, as given in the Experimental Section.
The main features of the electronic absorption spectra for the
investigated cobalt(III) corroles in nonbonding media under N2
are two intense absorptions, one of which is centered at 381-
406 nm and the other at 502-538 nm (see Experimental
Section). The parent peak of the mass spectra corresponds in
each case to the molecular ion [M]•+.
Structure of (Me4Ph5Cor)Co(py)2. Top and side views of
the molecular structure of (Me4Ph5Cor)Co(py)2 are displayed
in Figure 1a,b, together with the labeling scheme used for all
non-hydrogen atoms. Crystal data for (Me4Ph5Cor)Co(py)2‚
(21) Paolesse, R.; Licoccia, S.; Fanciullo, M.; Morgante, E.; Boschi, T.
Inorg. Chim. Acta 1993, 203, 107-114.

4850 Inorganic Chemistry, Vol. 40, No. 19, 2001
Guilard et al.
Table 1. Selected Absorption Maxima and Molar Absorptivities of Representative Free Base Corroles in CH2Cl2
λ
max, nm (ꢀ × 104, L mol-1 cm-1
)
compound
Soret bands
Visible bands
(Me6Et2Cor)H3a (1)
395 (12.9)
395 (12.7)
401 (7.3)
400 (8.3)
406 (9.9)
407 (10.1)
413 (7.0)
413 (7.5)
419 (8.5)
422 (7.1)
422 (7.3)
426 (6.2)
535 (1.5)
537 (1.9)
546 (1.0)
549 (1.5)
549 (1.9)
555 (1.0)
564 (1.9)
567 (1.5)
566 (1.6)
559 (1.6)
567 (1.5)
591 (1.9)
593 (2.4)
598 (1.0)
599 (2.1)
607 (1.3)
607 (1.4)
609 (1.3)
611 (1.2)
b
(Me2Et6Cor)H3
c
(Me2Et6PhCor)H3
(Me2Et2Ph4Cor)H3 (2)d
(Me4Ph5Cor)H3 (8)
640 (0.7)
638 (0.8)
(Me4Ph(m-OMePh)4Cor)H3 (9)
(Me4Ph(p-OMePh)4Cor)H3 (10)
(Me2Ph7Cor)H3 (12)
410 (6.3)
413 (7.0)
418 (6.2)
535 (1.3)
520 (1.6)
a Grigg, R.; Johnson, A. W.; Shelton, G. J. Chem. Soc. C 1971, 2287-2294. b Tardieux, C. Ph.D. Thesis, Universite´ de Bourgogne, Dijon,
France, 1997. c Data taken from ref 6. d Data taken from ref 7.
Table 2. Crystal Data and Structure Refinement Parameters for
(Me4Ph5Cor)Co(py)2•3CH2Cl2•H2O
formula
C129H106Cl6Co2N12O-
2(C63H49CoN6)‚3CH2Cl2‚H2O
MW
2170.95
cryst syst
space group
a (Å)
orthorhombic
Pna21
19.5690(4)
b (Å)
17.1070(6)
c (Å)
15.9160(6)
5328.2(5)
V (Å3)
Z
2
color
dark red
cryst dimen (mm)
D
0.20 × 0.15 × 0.10
calc (g cm3)
1.35
F(000)
2256
0.522
173
µ (mm-1
)
temp (K)
wavelength (Å)
radiation
diffractometer
scan mode
0.710 73
Mo KR graphite monochromated
KappaCCD
φ scans
hkl limits
0,22/0,24/0,21
2.5/30.51
35 460
Θ limits (deg)
no. of data measrd
no. data with I > 3σ(I)
weighting scheme
no. of variables
R
4791
2
2
4
4Fo /(σ2(Fo ) + 0.0004Fo ) + 1.0
693
0.069
0.083
1.488
Rw
GOF
largest peak in final difference (e Å3) 0.971
Table 3. Selected Interatomic Distances (Å) and Angles (deg) for
(Me4Ph5Cor)Co(py)2.
Bond Lengths (Å)
Co-N21
Co-N22
Co-N23
Co-N24
<Co-Np>
Co-N59
Co-N65
1.886(6)
1.915(6)
1.892(6)
1.884(5)
1.894(5)
1.980(7)
2.003(7)
<Np-CR>
1.378(8)
1.441(8)
1.385(8)
1.402(9)
1.484(9)
1.503(9)
1.386(9)
<CR-Câ>
<Câ-Câ>
<Cmeso-CR>
<Câ-Cphen>
<Câ-Cmet>
<Cphe-Cphe>
Figure 1. ORTEP diagrams of (Me4Ph5Cor)Co(py)2 (top) top-view
and (bottom) side view. Thermal ellipsoids are drawn to illustrate 30%
probability surfaces.
1.979 and 2.060 Å, respectively.22 The shortening of the Co-
Np bond lengths in the corrole derivative (Me4Ph5Cor)Co(py)2
can be ascribed to the reduced hole size of the corrole ligand
[Me4Ph5Cor]3- relative to the tetraphenylporphyrin ligand
[TPP]2-, since a similar decrease of the M-Np bond lengths
was observed in several other metallocorroles as different as
(Me8Cor)Rh(AsPh3),23 (Me8Ph3Cor)Co(PPh3)9 (Cor ) â-un-
substituted corrole ring; Me8Ph3Cor ) 5,10,15-triphenyl-2,3,7,8,-
12,13,17,18-octamethylcorrole), and (Me8Cor)Mn.24
Angles (deg)
<CR-Np-CR> 109.2(5) <CR-Cmeso-CR>
124.6(6)
123.2(6)
<Np-CR-Câ>
<CR-Câ-Câ>
108.0(5) <Np-CR-Cmeso>
107.4(5) <Cphe-Cphe-Cphe> 120.0(9)
The central cobalt atom in (Me4Ph5Cor)Co(py)2 lies almost
in the 23-atom core corrole mean plane. Its displacement of
0.002(1) Å relative to this mean plane is not significant. It lies
also at 0.021(1) Å above the 4Np mean plane. The location of
the cobalt atom in the corrole mean plane is probably related
to its six-coordination, that is, the presence of the two axial
pyridine molecules bound to the central metal. In the five-
coordinate cobalt(III) corrole derivatives of known structures,9,17
a larger displacement of the metal atom away from the 23-atom
core mean plane is observed. In the two previously characterized
five-coordinate triphenylphosphine cobalt(III) corrole com-
(22) Scheidt, W. R.; Cunningham, J. A.; Hoard, J. L. J. Am. Chem. Soc.
1973, 95, 8289-8294.
(23) Boschi, T.; Liccocia, S.; Paolesse, R.; Tagliesta, P.; Tehran, M. A.;
Pelizzi, G.; Vitali, F. J. Chem. Soc., Dalton Trans. 1990, 463-468.
(24) Liccocia, S.; Morgante, E.; Paolesse, R.; Polizio, F.; Senge, M. O.;
Tondello, E.; Boschi, T. Inorg. Chem. 1997, 36, 1564-1570.

Alkyl and Aryl Substituted Corroles
Inorganic Chemistry, Vol. 40, No. 19, 2001 4851
Table 4. Half-Wave Potentials (V vs SCE) of Mono-Cobalt Corroles in CH2Cl2, 0.1 M TBAP
red
ox
compound
first
fourth
third
second
first
∆ox(2-1)
(Me6Et2Cor)Co (13)
-0.31
-0.30
-0.16
b
-0.18
-0.15
-0.15
1.21
1.17
1.25
1.26
1.15
1.24
1.26
1.07
0.94
0.94
0.84
0.87
0.85
0.87
0.59
0.57
0.76
0.52
0.55
0.59
0.62
0.03
0.11
0.30
0.34
0.38
0.42
0.45
0.62
0.46
0.46
0.18
0.17
0.17
0.17
(Et8Cor)Coa
(Me2Et2Ph4Cor)Co (14)
(Me2Ph7Cor)Co (18)
(Me4Ph(p-OMePh)4Cor)Co (17)
(Me4Ph(m-OMePh)4Cor)Co (16)
(Me4Ph5Cor)Co (15)
a Data are taken from ref 10. b Broad irreversible process.
plexes, the displacement of the cobalt atom relative to the corrole
mean plane is 0.38 Å in (Cor)Co(PPh3)17 and 0.29 Å in (Me8-
Ph3Cor)Co(PPh3).9 It should also be noted that the two pyridine
molecules are almost perpendicular to the corrole mean plane
(84.6(2) and 89.4(2)°), while the dihedral angle between the
two axial pyridine molecule mean planes is equal to 83.7(2)°
(Figure 1).
The corrole core is essentially planar. The maximum dis-
placement of the carbon and nitrogen atoms relative to corrole
mean plane is 0.20(1) Å (C7), whereas the average displacement
of the carbon and nitrogen atoms from this mean plane is only
0.09(1) Å. The small perpendicular displacements of the geminal
â-carbons above and below the corrole mean plane show that
a very small saddling of the core is present. The average
displacements of the geminal â-carbons corresponding to the
methylated and phenylated pyrroles above and below the corrole
mean plane are 0.16(1) and 0.19(1) Å, respectively. Moreover,
very small ruffling and doming distortions are superimposed
to the saddle deformation, as indicated by the average displace-
ments of the meso-carbons above and below the corrole core
mean plane of 0.02(1) and - 0.07(1) Å and the position of the
4Np mean plane which lies only 0.023(1) Å above the corrole-
core mean plane. Despite a larger steric crowding in this six-
coordinate cobalt(III) species, (Me4Ph5Cor)Co(py)2, the overall
conformation of the corrole core is comparable to that present
in the two five-coordinate triphenylphosphine cobalt(III) cor-
roles, (Cor)Co(PPh3)17 and (Me8Ph3Cor)Co(PPh3),9 where the
average displacements of the carbon and nitrogen atoms away
from the corrole mean planes are 0.05 and 0.14 Å, respectively.
No unusual intermolecular short distances occur in the crystals
of (Me4Ph5Cor)Co(py)2‚3CH2Cl2‚H2O.
Electrochemistry. The Co(III)/Co(II) reaction is reversible
for five of the six investigated compounds. This reduction occurs
at E1/2 ) -0.30 or -0.31 V for the two derivatives with only
ethyl or methyl substituents ((Et8Cor)Co and compound 13) and
the potentials are shifted to an easier reduction located at E1/2
) -0.15 to -0.18 V for the corroles with four or five phenyl
substituents at the â- or meso-positions of the macrocycle
(compounds 14-17) (see Table 4). An irreversible Co(III)/Co(II)
process is seen for (Me2Ph7Cor)Co (compound 18), as indicated
by broad reduction and reoxidation peaks which are separated
by 350 mV for a scan rate of 0.1 V/s.
Similar UV-visible changes are observed during controlled-
potential electroreduction of compounds 13-17 and an example
of the thin-layer spectral changes is shown in Figure 2a for the
case of (Me4Ph5Cor)Co (15). The initial Co(III) corroles are
all characterized by a single absorption band in the visible region
of the spectrum (λmax ) 529 nm for 15), while the Co(II)
reduction products each have two well-defined visible bands,
one of which is located between 535 and 561 nm and the other
between 574 and 641 nm (Table 5 and Figure 2a). The spectrum
of compound 13, which contains only alkyl substituents, differs
Figure 2. UV-visible spectral changes during thin-layer controlled-
potential electrolysis of (Me4Ph5Cor)Co (15) at (a) -0.60 and (b) +0.60
V in CH2Cl2, 0.1 M TBAP.
substantially in its neutral and reduced forms from that of
compounds 14-18, all of which contain phenyl groups at the
â-pyrrole positions of the macrocycle. The thin-layer spectral
changes obtained upon reduction of compound 13 are reversible
and almost identical to spectral changes which have been
reported upon the metal-centered reduction of other Co(III)
corroles under similar solution conditions.1,2,10,25
The electrooxidation of each cobalt corrole was also inves-
tigated by cyclic voltammetry in CH2Cl2 containing 0.1 M
TBAP. The redox potentials for these processes are summarized
in Table 4 and examples of cyclic voltammograms for com-
pounds 13-15 and (Et8Cor)Co are shown in Figure 3 which is
arranged from the most difficult to reduce and easiest to oxidize
(25) Adamian, V. A. Ph.D. Dissertation, University of Houston, TX, 1995.

4852 Inorganic Chemistry, Vol. 40, No. 19, 2001
Guilard et al.
Table 5. UV-Visible Spectral Data for Co(III) and Co(II) Corroles in CH2Cl2 Containing 0.1 M TBAP
λ
max, nm (ꢀ × 104, L mol-1 cm-1
CH2Cl2 under CO
)
metal
ion
CH2Cl2 under N2
pyridine under N2
cpd
13
14
15
16
17
18
Co(III)
Co(II)
381 (7.6)
394 (6.6)
398 (4.5)
404 (5.2)
398 (5.9)
406 (5.3)
502 (0.9)
526 (1.5)
529 (1.1)
533 (1.7)
533 (1.6)
538 (1.4)
378(4.3)
393(4.8)
407(3.3)
406(4.2)
395(3.9)
409(3.9)
540(1.2)
562(1.7)
567(1.3)
564(1.6)
564(1.7)
562(1.5)
425(4.8)
428(5.0)
433(3.5)
435(4.2)
433(3.8)
442(4.1)
538(0.9)
547(0.9)
557(0.7)
554(0.9)
553(0.8)
558(0.8)
576(2.9)
593(3.0)
598(1.7)
598(2.0)
598(2.3)
598(1.5)
13
14
15
16
17
18
405 (8.1)
415 (7.0)
419 (4.4)
423 (5.4)
423 (5.4)
429 (4.7)
535 (1.2)
553 (1.1)
558 (1.0)
559 (1.5)
559 (1.3)
561 (1.4)
574 (0.9)
612 (0.9)
641 (0.7)
641 (0.9)
641 (1.1)
641 (1.1)
for the first two oxidations are approximately half the values
seen for the other three redox reactions (see Figure 3).
The thin-layer spectral changes obtained during the first
oxidation of compounds 13-18 are similar to each other, and
an example of the thin-layer UV-visible spectroelectrochemical
data is shown in Figure 2b for the case of (Me4Ph5Cor)Co (15)
where the first oxidation product at an applied potential of +0.60
+
V is formulated as [(Me4Ph5Cor)Co]2
.
One key feature in the voltammograms of compounds 13-
18 is the absolute potential separation between E1/2 values for
the first and second oxidations, ∆ox(2-1). The ∆ox(2-1)
values are indicated in Figure 3 and summarized in the last
column of Table 4 for each compound. These values range from
0.62 V for compound 13 to a smaller separation of 0.17-0.18
V for compounds 15-18, all four of which contain a phenyl
group at the 10-meso position of the corrole macrocycle.
The larger ∆ox(2-1) values can be associated with a stronger
interaction between the two equivalent redox centers in the
singly oxidized compound,10,26-29 and the data suggest the
following order of interaction between the half-oxidized corrole
dimers.
+
+
[(Me6Et2Cor)Co]2+ > [(Et8Cor)Co]2 ≈ [14]2
+
+
+
+
> [15]2 ≈ [16]2 ≈ [17]2 ≈ [18]2
Figure 3. Cyclic voltammograms of 2.0 × 10-3 M (Me6Et2Cor)Co
(13), 3.0 × 10-3 M (Et8Cor)Co, 2.0 × 10-3 M (Me2Et2Ph4Cor)Co (14),
and 1.5 × 10-3 M (Me4Ph5Cor)Co (15) in CH2Cl2, 0.1 M TBAP.
A detailed electrochemical study of dimer formation as a
function of solvent and corrole macrocyclic structure will be
published elsewhere,30 but it should now be clearly noted that
all of the presently examined corroles exist as unaggregated
monomers in their neutral or singly reduced forms.
Formation of Mono- and Bis-Pyridine Adducts. Each
cobalt corrole was investigated as to its pyridine binding ability
in CH2Cl2/pyridine mixtures. The addition of pyridine to a
CH2Cl2 solution of each corrole leads initially to a decrease in
intensity of the Soret and visible band of the neutral complex,
and this is followed at higher pyridine concentrations by a large
red shift of the Soret band and the appearance of a new intense
compound (13) to the derivative which is easiest to reduce and
hardest to oxidize of the four compounds (15). The electro-
chemistry of (Et8Cor)Co was earlier characterized under similar
solution conditions.10
The electrochemistry of compounds 13-18 in CH2Cl2 is
similar to what has been reported for (Et8Cor)M where M )
Co, Ni, or Cu in noncoordinating or weakly coordinating
media.10 The formally M(III) complexes are all monomeric in
their neutral and singly reduced forms, but all are proposed to
+
(26) (a) Geiger, W. E.; Connelly, N. G. In AdVances in Organometallic
Chemistry; Stone, F. G. A., West, R., Eds.; Academic: Orlando, FL,
1985; Vol. 24, pp 89-97. (b) Kotz, J. C. In Topics in Organic
Electrochemistry; Fry, A. J., Britton, W. E., Eds.; Plenum: New York,
1986; pp 95-109.
exist as π-π dimers which are formulated as [(Et8Cor)M]2
2+
and [(Et8Cor)M]2 after the first two one-electron oxidations
in CH2Cl2. The cyclic voltammograms of (Et8Cor)M under these
solution conditions exhibit four reversible oxidation processes,
the first two of which involve the abstraction of one electron
per two metallocorrole units and have peak currents which are
only half as large as seen for the other electron-transfer
processes. Compounds 13-18 also exhibit five sets of oxidation/
reduction peaks or four sets of oxidation peaks in CH2Cl2 (see
Table 4), and in each case the diffusion controlled peak currents
(27) Yap, W. T.; Durst, R. A. J. Electroanal. Chem. Interfacial Electrochem.
1981, 130, 3.
(28) Kadish, K. M.; Boulas, P.; D’Souza, F.; Aukauloo, M. A.; Guilard,
R.; Lausmann, M.; Vogel, E. Inorg. Chem. 1994, 33, 471-476.
(29) Chang, D.; Cocolios, P.; Wu, Y. T.; Kadish, K. M. Inorg. Chem. 1984,
23, 1629-1633.
(30) Kadish, K. M.; Shao, J.; Ou, Z.; Gros, C. P.; Bolze, F.; Je´roˆme, F.;
Guilard, R. Manuscript in preparation.

Alkyl and Aryl Substituted Corroles
Inorganic Chemistry, Vol. 40, No. 19, 2001 4853
Figure 5. UV-visible spectral changes of 5.0 × 10-6 M (Me4Ph5-
Cor)Co (15) during a titration by pyridine in CH2Cl2 to give (a) (Me4-
Ph5Cor)Co(py) and (b) (Me4Ph5Cor)Co(py)2. The pyridine concentra-
tions for the plots range (a) from 8.7 × 10-6 to 2.1 × 10-5 M and (b)
from 4.8 × 10-3 to 1.5 × 10-2 M.
Table 6. Equilibrium Constants of Cobalt Corroles Binding
Pyridine or CO in CH2Cl2 at 296 K
Figure 4. UV-visible spectra of (Me4Ph5Cor)Co (15) in N2 or CO
pyridine
CO
CO
saturated CH2Cl2 and in N2 saturated pyridine.
log log P1/2
log
νCO
compound
K1
K2 (Torr) Kb (cm-1
)
visible band located close to 600 nm for all of the compounds
containing phenyl substituents at the corrole macrocycle. These
two sets of spectral changes are associated with the stepwise
binding of a pyridine molecule to the cobalt ion as shown in
eqs 2 and 3 for the case of compound 15, (Me4Ph5Cor)Co,
whose UV-visible spectra in CH2Cl2 and neat pyridine under
N2 are illustrated in Figure 4a,c.
(Me6Et2Cor)Co (13)
(Et8Cor)Coa
(Me4Ph5Cor)Co (15)
3.78 2.00 25.3 3.7 2040
4.23 1.58
4.90 2.10
7.1 4.2 2049
6.4 4.3 2045
(Me4Ph(p-OMePh)4Cor)Co (17) 4.95 2.17
(Me2Et2Ph4Cor)Co (14)
(Me4Ph(m-OMePh)4Cor)Co (16) 5.32 2.38
(Me2Ph7Cor)Co (18) 5.48 2.19
5.01 2.19 13.0 3.9 2050
5.2 4.3 2049
1.9 4.8 2050
a Data were taken from reference 31. b [CO] ) kH‚PCO, kH ) 6.7 ×
(Me4Ph5Cor)Co + py h (Me4Ph5Cor)Co(py)
(2)
10-3 M/atm in CH2Cl2, and K ) (P1/2‚kH)-1
.
(Me4Ph5Cor)Co(py) + py h (Me4Ph5Cor)Co(py)2 (3)
alkyl substituents (see summary of spectral data in Table 5).
This intense visible band at close to 600 nm can thus be used
as one diagnostic criterium for the occurrence of a bis-pyridine
adduct for the neutral complex.
Pyridine binding constants were obtained for each Co(III)
corrole, and a summary of the thermodynamic data is given in
Table 6. The values of log K1 range from 3.78 to 5.48, while
log K2 ranges from 2.00 to 2.38. Pyridine binding constants of
a similar magnitude were previously measured for the stepwise
conversion of (Et8Cor)Co to (Et8Cor)Co(py) and then to (Et8-
Cor)Co(py)2 in acetone.31
The spectral changes associated with the conversion of (Me4-
Ph5Cor)Co, 15, to its mono-pyridine form are shown in Figure
5a and when analyzed by a Hill plot of log((Ai - A0)/(Af - Ai))
vs log [py] give a slope of 1.1, consistent with the binding of
one pyridine molecule as shown in eq 2. A more substantial
change in the UV-visible spectra is seen in Figure 5b, where
the Hill plot has a slope of 1.0, consistent with the binding of
a second pyridine molecule to (Me4Ph5Cor)Co(py), thus gen-
erating (Me4Ph5Cor)Co(py)2 as shown in eq 3.
It is important to point out that none of the investigated five-
coordinate Co(III) complexes show major absorption bands
between 550 and 800 nm while the six-coordinate Co(III)
species are in each case characterized by an intense absorption
band at 593-598 nm for compounds 14-18 in pyridine under
N2 and at λmax ) 576 nm for compound 13 which contains only
The log K2 values of 2.00-2.38 for compounds 13-18 are
also close to the values obtained for addition of a single pyridine
ligand to (Me8Cor)Co(PPh3) (log K ) 2.29),3 and these values
(31) Murakami, Y.; Yamada, S.; Matsuda, Y.; Sakata, K. Bull. Chem. Soc.
Jpn 1978, 51, 123-129.

4854 Inorganic Chemistry, Vol. 40, No. 19, 2001
Guilard et al.
Figure 6. UV-visible spectral changes of 6.0 × 10-6 M (Me4Ph5-
Cor)Co (15) during a titration by CO in CH2Cl2. The CO partial pressure
ranges from 1 to 230 Torr for the Hill plot.
are slightly higher than the measured log K ) 1.54 for pyridine
addition to (Me8Ph3Cor)Co(PPh3) or to a variety of (Me8(XPh)3-
Cor)Co(PPh3) complexes, where log K ranges from 1.3 to 1.72
for compounds with X ) p-OMe, p-Me, p-Cl, m-Cl, or o-Cl.3
Carbon Monoxide Binding and Electrochemistry under
a CO Atmosphere. It is now well-known that Co(III) porphy-
rins can axially coordinate one or two CO molecules depending
upon the nature of the solvent and supporting electrolyte,32-35
but little is known about the reaction of the cobalt(III) corroles
with carbon monoxide. Each cobalt(III) corrole was therefore
investigated as to its CO binding ability in CH2Cl2.
Figure 7. Cyclic voltammogramms of 2.0 × 10-3 M (Me4Ph5Cor)Co
(15) under different CO partial pressures in CH2Cl2, 0.1 M TBAP.
The UV-visible spectra of the neutral Co(III) corroles were
measured under N2 and under CO. Table 5 compares these
spectral data for the cobalt(III) complexes, while Figure 4b
shows the spectrum of compound 15 under a CO atmosphere.
The spectra were also measured under a variety of CO partial
pressures and indicated the binding of one and only one CO
molecule to the neutral Co(III) corrole at all CO pressures up
to 1 atm. An example of the spectral changes seen upon
increasing the CO partial pressure from log PCO ) 0.25 to 1.25
is shown in Figure 6 for the case of (Me4Ph5Cor)Co (15), where
the initial corrole has absorption maxima at 398 and 529 nm
and the mono-CO adduct has bands at 407 and 567 nm (see
also Figure 4). Well-defined isobestic points are obtained at 369,
450, 546, and 600 nm in the conversion of (Me4Ph5Cor)Co to
(Me4Ph5Cor)Co(CO). The Hill plot of log((Ai - A0)/(Af - Ai))
vs log PCO (inset of Figure 6) gives a slope of 1.1, thus indicating
the binding of one CO molecule to (Me4Ph5Cor)Co. The
Figure 8. Plot of E1/2 for the first reduction of (Me4Ph5Cor)Co (15) in
CH2Cl2, 0.1 M TBAP, vs the CO partial pressure (log PCO).
specific corrole macrocycle. As in the case of py binding, larger
log K values are obtained for the five corroles having both aryl
and alkyl susbtituents rather than only alkyl substitution (see
Table 6).
CO
calculated log K for this reaction is 4.2 (P1/2 ) 7.1 Torr).
Similar spectral changes were obtained for each of the other
corroles as a function of CO partial pressure, and a summary
of the binding constants, which range between log K ) 3.7 and
log K ) 4.8, are given in Table 6 along with the values of νCO
which range from 2040 to 2050 cm-1, depending upon the
The number of CO molecules bound to compound 15 in
CH2Cl2 under CO was also monitored by electrochemical
methods which plot E1/2 vs the CO partial pressure, and an
example of the current voltage curves at different CO partial
pressure is shown in Figure 7. A plot of E1/2 for the first
reduction of the compound vs log PCO is linear with a slope of
-62 mV shift per each 10-fold increase in CO partial pressure
(see Figure 8), and this result can be compared to a theoretical
slope of -59 mV per log PCO for the case where one CO
molecule binds to the neutral Co(III) corrole but dissociates after
(32) Herlinger, A. W.; Brown, T. L. J. Am. Chem. Soc. 1971, 93, 1790-
1791.
(33) Mu, X. H.; Kadish, K. M. Inorg. Chem. 1989, 28, 3743-3747.
(34) Hu, Y.; Han, B. C.; Bao, L. Y.; Mu, X. H.; Kadish, K. M. Inorg.
Chem. 1991, 30, 2444-2446.
(35) Schmidt, E.; Zhang, H.; Chang, C. K.; Babcock, G. T.; Oertling, W.
A. J. Am. Chem. Soc. 1996, 118, 2954-2961.

Alkyl and Aryl Substituted Corroles
Inorganic Chemistry, Vol. 40, No. 19, 2001 4855
a reversible one-electron reduction to give the Co(II) form of
the complex.
of CO partial pressure from 0.00 to 0.68 atm, the first oxidation
shifts anodically until it is merged with the second oxidation.
When the CO partial pressure is higher than 0.68 atm, only
two oxidations, which have the same peak currents as the
Co(III)/Co(II) reaction, can be observed.
Similar CO and pyridine binding reactions are seen for
compound 15 and for the anthracenyl and biphenylenyl linked
bis-corrole Co(III) complexes having the same macrocycle, and
this is described in the following paper.11
This dissociation of CO from the cobalt corrole after
electroreduction was verified by thin-layer IR spectroelectro-
chemistry. An IR band for CO bound to the Co(III) corrole is
seen at 2049 cm-1 before reduction, and this band disappears
after the formation of [(Me4Ph5Cor)Co]- under CO. Under these
conditions, the electroreduction is proposed to proceed as shown
in eq 4:
In summary, six cobalt corroles with different numbers of
alkyl and aryl substituents were synthesized and investigated
as to their electrochemical and ligand binding properties in
nonaqueous media. One of the compounds, (Me4Ph5Cor)Co (15),
was then utilized as a comparison compound to study the
reactions of face to face bis-corroles whose properties are
reported in the following paper in this issue.
[(Me4Ph5Cor)CoIII(CO)] + e h
[(Me4Ph5Cor)CoII]- + CO (4)
Plots of E1/2 vs CO partial pressure (Figure 8) also enable a
calculation of the CO binding constant for the neutral com-
pound,33 and in the case of (Me4Ph5Cor)Co(CO) the calculated
log K ) 4.4 is comparable with the log K ) 4.2 for CO binding
to the same compound determined using UV-visible spectro-
scopic techniques (see Table 6).
Figure 7 also shows that the first oxidation peak of compound
15 shifts in a positive direction with increasing CO partial
pressure, while the second and third oxidations remain virtually
unchanged in potential upon going from an N2 to a CO
atmosphere above the solution. The first reversible oxidation
of each corrole is associated with formation of the partially
oxidized dimer under a nitrogen atmosphere. With an increase
Acknowledgment. The support of the Robert A. Welch
Foundation (K.M.K., Grant E-680) and the CNRS (Grant UMR
5633) are gratefully acknowledged. The “Re´gion Bourgogne”
and “Air Liquide” are acknowledged for a scholarships (F.J.).
The authors are also grateful to M. Soustelle for assistance in
the synthesis of pyrrole precursors.
Supporting Information Available: Tables of atomic coordinates
and their equivalent isotropic thermal parameters and bond distances
and angles. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC010177+