Alkyl- and aryl-substituted corroles. 5. Synthesis, physicochemical properties, and X-ray structural characterization of copper biscorroles and porphyrin-corrole dyads

Article abstract of DOI:10.1021/ic049651c

The synthesis and characterization of cofacial copper biscorroles and porphyrin-corroles linked by a biphenylenyl or anthracenyl spacer are described. The investigated compounds are represented as (BCA)Cu₂ and (BCB)Cu₂ in the case of the biscorrole (BC) derivatives and (PCA)Cu₂ and (PCB)Cu₂ in the case of porphyrin (P)-corrole (C) dyads, where A and B represent the anthracenyl and biphenylenyl bridges, respectively. A related monomeric corrole (Me₄Ph₅Cor)Cu and monomeric porphyrin (Me₂Et₆PhP)Cu that comprise the two halves of the porphyrin-corrole dyads were also studied. Electron spin resonance (ESR), ¹H NMR, and magnetic measurements data demonstrate that the copper corrole macrocycle, when linked to another copper corrole or copper(II) porphyrin, can be considered to be a Cu(III) complex in equilibrium with a Cu(II) radical species, copper(III) corrole being the main oxidation state of the corrole species at all temperatures. The cofacial orientation of (BCB)Cu₂, (BCA)Cu₂, and (PCB)Cu₂ was confirmed by X-ray crystallography. Structural data: (BCB)Cu₂(C ₁₁₀H₈₂N₈Cu₂·3CDCl ₃), triclinic, space group P1, a = 10.2550-(2) A, b = 16.3890(3) A, c = 29.7910(8) A, α = 74.792(1)°, β = 81.681(1)°, γ = 72.504(2)°, Z = 2; (BCA)Cu₂-(C ₁₁₂H₈₄N₈Cu₂·C ₇H₈·1.5H₂O), monoclinic, space group P2₁/c, a = 16.0870(4) A, b = 35.109(2) A, c = 19.1390(8) A, β = 95.183(3)°, Z = 4; (PCB)Cu₂(C ₈₉H₇₁N₈Cu₂·CHCl₃), monoclinic, space group P2₁/n, a = 16.7071(3) A, b = 10.6719(2) A, c = 40.8555(8) A, β = 100.870(1)°, Z = 4. The two cofacial biscorroles, (BCA)Cu₂ and (BCB)Cu₂, both show three electrooxidations under the same solution conditions. The reduction of (BCA)Cu₂ involves a reversible electron addition to each macrocycle at the same potential of E_1/2 = -0.20 V although (BCB)Cu₂ is reversibly reduced in two steps to give first [(BCB)Cu₂]^- and then [(BCB)Cu₂]^2-, each of which was characterized by ESR spectroscopy as containing a Cu(II) center. These latter electrode reactions occur at E_1/2 = -0.36 and -0.51 V versus a saturated calomel reference electrode. The half-reduced and fully reduced (BCB)Cu₂ show similar Cu(II) ESR spectra, and no evidence of a triplet signal is observed. The two well-separated reductions of (BCB)Cu₂ to give [(BCB)Cu₂]^2- can be attributed to a stronger π-π interaction between the two macrocycles of this dimer as compared to those of (BCA)Cu₂. The copper porphyrin-corrole dyads, (PCA)Cu₂ and (PCB)Cu₂, show five reversible oxidations and two reversible reductions, and these potentials are compared with corresponding values for electrochemical reactions of the porphyrin and corrole monomers under the same solution conditions.

Full text of DOI:10.1021/ic049651c

Inorg. Chem. 2004, 43, 7441−7455
Alkyl- and Aryl-Substituted Corroles. 5. Synthesis, Physicochemical
Properties, and X-ray Structural Characterization of Copper Biscorroles
and Porphyrin Corrole Dyads
−
Roger Guilard,* Claude P. Gros, Jean-Michel Barbe, Enrique Espinosa, Franc
Alain Tabard
¸
ois Je´roˆme,† and
UniVersite´ de Bourgogne, LIMSAG UMR 5633, Faculte´ des Sciences Gabriel, 6,
bouleVard Gabriel, 21000-Dijon, France
Jean-Marc Latour
CEA Grenoble, Laboratoire DRDC/PMB, UMR 5155 CEA-CNRS-UJF,
38056-Grenoble Cedex 09, France
Jianguo Shao, Zhongping Ou, and Karl M. Kadish*
UniVersity of Houston, Department of Chemistry, Houston, Texas 77204-5003
Received March 16, 2004
The synthesis and characterization of cofacial copper biscorroles and porphyrin
anthracenyl spacer are described. The investigated compounds are represented as (BCA)Cu2 and (BCB)Cu2 in the
case of the biscorrole (BC) derivatives and (PCA)Cu2 and (PCB)Cu2 in the case of porphyrin (P) corrole (C) dyads,
where A and B represent the anthracenyl and biphenylenyl bridges, respectively. A related monomeric corrole
−corroles linked by a biphenylenyl or
−
(Me4Ph5Cor)Cu and monomeric porphyrin (Me2Et6PhP)Cu that comprise the two halves of the porphyrin−corrole
dyads were also studied. Electron spin resonance (ESR), 1H NMR, and magnetic measurements data demonstrate
that the copper corrole macrocycle, when linked to another copper corrole or copper(II) porphyrin, can be considered
to be a Cu(III) complex in equilibrium with a Cu(II) radical species, copper(III) corrole being the main oxidation state
of the corrole species at all temperatures. The cofacial orientation of (BCB)Cu2, (BCA)Cu2, and (PCB)Cu2 was confirmed
by X-ray crystallography. Structural data: (BCB)Cu2(C110H82N8Cu2
(2) Å, b 16.3890(3) Å, c 29.7910(8) Å, R ) 74.792(1) â ) 81.681(1)
(C112H84N8Cu2 C7H8 1.5H2O), monoclinic, space group P 21/c, a 16.0870(4) Å, b
Å, â ) 95.183(3) , Z 4; (PCB)Cu2(C89H71N8Cu2 CHCl3), monoclinic, space group P21/n, a
10.6719(2) Å, c 40.8555(8) Å, â ) 100.870(1) , Z 4. The two cofacial biscorroles, (BCA)Cu2 and (BCB)Cu2,
‚
3CDCl3), triclinic, space group P1
γ ) 72.504(2) , Z
35.109(2) Å, c
16.7071(3) Å, b )
h
)
, a
2; (BCA)Cu2-
19.1390(8)
) 10.2550-
)
)
°
,
°
,
°
‚
‚
)
)
)
°
)
)
‚
°
)
)
both show three electrooxidations under the same solution conditions. The reduction of (BCA)Cu2 involves a reversible
electron addition to each macrocycle at the same potential of E1 2 ) −0.20 V although (BCB)Cu2 is reversibly reduced
/
in two steps to give first [(BCB)Cu2] and then [(BCB)Cu2]2 , each of which was characterized by ESR spectroscopy
-
-
as containing a Cu(II) center. These latter electrode reactions occur at E1 2 ) −0.36 and −0.51 V versus a saturated
/
calomel reference electrode. The half-reduced and fully reduced (BCB)Cu2 show similar Cu(II) ESR spectra, and no
-
evidence of a triplet signal is observed. The two well-separated reductions of (BCB)Cu2 to give [(BCB)Cu2]2 can
be attributed to a stronger π−π interaction between the two macrocycles of this dimer as compared to those of
(BCA)Cu2. The copper porphyrin−corrole dyads, (PCA)Cu2 and (PCB)Cu2, show five reversible oxidations and two
reversible reductions, and these potentials are compared with corresponding values for electrochemical reactions of
the porphyrin and corrole monomers under the same solution conditions.
Introduction
reported in the mid 1960s1-3 but not investigated in any detail
until several facile syntheses for the preparation of these
compounds had become available.4-23 The first attempts to
The last 10 years have shown a renaissance of interest in
the study of corroles and metallocorroles that were first
* Authors to whom correspondence should be addressed. E-mail:
Roger.Guilard@u-bourgogne.fr (R.G.); kkadish@uh.edu (K.M.K.).
† Present address: Universite´ de Poitiers, LACCO-ESIP, UMR 6503
CNRS, 40, avenue du Recteur Pineau, 86022 Poitiers, France.
(1) Johnson, A. W.; Kay, I. T. J. Chem. Soc. 1965, 1620-1629.
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(3) Johnson, A. W.; Kay, I. T. Proc. Chem. Soc., London 1964, 89-90.
10.1021/ic049651c CCC: $27.50
Published on Web 10/22/2004
© 2004 American Chemical Society
Inorganic Chemistry, Vol. 43, No. 23, 2004 7441

Guilard et al.
synthesize corroles with many different transition-metal ions
were carried out by Boschi and co-workers24-26 using
octamethyl derivatives, and this was followed several years
later by detailed studies of complexes with other macrocy-
cles such as octaethylcorroles,27-33 pentafluorotriphenyl
corroles,11,12,34-38 and triarylcorroles,10,14-16,39,40 thus estab-
lishing a good database of information on corroles with
different metal ions and different macrocycles.
Our own research interest has been directed toward the
study of aryl-substituted corroles in their mononuclear or
binuclear form.4,41-48 These latter compounds can be linked
via one of several different spacer groups to give face-to-
face dyads.41-47 One key interest of these dyads is their ability
to bind small molecules such as CO or nitrogenous bases,41,42,44
and another is the interaction that can occur between the
two corrole units as has often been seen for similar linked
bisporphyrins.4,49,50 Furthermore, we have been able to
synthesize heterobimetallic dyads where a porphyrin and a
corrole are linked together in a cofacial arrangement by a
rigid spacer.41,44-46,51 These porphyrin-corrole derivatives
have the possibilities for displaying versatile complexation
properties whereas both mono- and bimetallic complexes
have been isolated.41,44-46,51 Monocobalt derivatives with the
cobalt atom inside the corrole moiety can be easily obtained,
thus allowing for the further insertion of a large variety of
metals into the porphyrin macrocycle.51
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This paper describes the synthesis, structural characteriza-
tion, and properties of four homobimetallic copper dyads
represented as (BCA)Cu2 and (BCB)Cu2 in the case of
biscorrole derivatives and (PCA)Cu2 and (PCB)Cu2 in the
case of porphyrin (P)-corrole (C) dyads, where A and B
represent the anthracenyl and biphenylenyl bridges, respec-
tively (Chart 1). This work builds upon earlier studies
involving cobalt complexes of bisporphyrins,49 biscor-
roles,41,42,45,47 and porphyrin-corrole dyads.41,44-46 The
properties of the herein reported face-to-face linked metallo-
macrocycles that can exhibit interaction between the two
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7442 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
Chart 1
EG&G model 173 potentiostat. Time-resolved UV-vis spectra were
recorded with a Hewlett-Packard model 8453 diode array rapid-
scanning spectrophotometer.
X-ray Data Collection and Structure Determination Details
for (BCB)Cu2, (BCA)Cu2, and (PCB)Cu2. Single-crystals suitable
for X-ray diffraction analysis were obtained from (BCB)Cu2,
(BCA)Cu2, and (PCB)Cu2, exhibiting prismatic-plate morphologies
and dark-red colors. The dimensions of the selected specimens were
0.25 × 0.12 × 0.08 mm3 for (BCB)Cu2, 0.30 × 0.20 × 0.04 mm3
for (BCA)Cu2, and 0.25 × 0.18 × 0.05 mm3 for (PCB)Cu2. Data
were collected at low temperature (T ) 112, 173, and 110 K for
(BCB)Cu2, (BCA)Cu2, and (PCB)Cu2, respectively) on two Nonius
Kappa CCD diffractometers54 using Mo KR graphite monochro-
matic radiation (λ ) 0.71073 Å) from a sealed tube. In the three
crystal structure determinations, lattice parameters were obtained
by a least-squares fit to the optimized setting angles of all reflec-
tions in the full θ-range data collection. Intensity data were recorded
as æ scans for (BCA)Cu2 and as æ and ω scans with κ offsets for
(BCB)Cu2 and (PCB)Cu2, respectively. Data reductions were done
using the DENZO software.55 The structures were solved by di-
rect methods using the SIR92 program.56 Refinements were carried
out by full-matrix least squares on F with I > 3σ(I) data using
the LSFM OpenMoleN program 57 for (BCA)Cu2, and on F2 with
all data using the SHELXL97 program58 for (BCB)Cu2 and
(PCB)Cu2.
(Me2Et6PhP)Cu (Chart 1), are also presented, and the data
are utilized as references to identify clearly the contribution
of each counterpart in the overall properties of the bismac-
rocycles.
Experimental Section
X-ray crystallographic files, in CIF format, for the structure
determination of (BCB)Cu2, (BCA)Cu2, and (PCB)Cu2 have been
deposited at the CCDC and are available on request from the
Director of the Cambridge Crystallographic Data Center, 12 Union
Road, GB-Cambridge CN2 1EZ, U.K., on quoting the full journal
citation.
Instrumentation. UV-vis spectra were recorded on a Varian
Cary 1 spectrophotometer. Mass spectra were obtained on a Bruker
ProFLEX III spectrometer in the matrix-assisted laser desorption
ionization time-of-flight (MALDI-TOF) mode using dithranol as a
matrix. Microanalyses were performed at the Universite´ de Bour-
1
gogne on a Fisons EA 1108 CHNS instrument. H NMR spectra
Crystal Data for (BCB)Cu2(C110H82N8Cu2‚3CDCl3). Experi-
mental and crystal data of (BCB)Cu2 are given in Table 1.
Anisotropic thermal parameters were used for non-H atoms.
Hydrogens and deuteriums were placed at calculated positions as
riding atoms. They were refined with two different global isotropic
thermal factors, corresponding to either H or D atoms. One of the
three CDCl3 solvent molecules belonging to the asymmetric unit
was found to be disordered between two positions very close to
each other. The corresponding sites occupation factors were refined,
leading to the values 0.81(1)/0.19(1). The final agreement factors
are R(F) ) 0.1011 and Rw(F2) ) 0.2368 for I > 2σ(I) data. At
convergence, the maximum and minimum residual electron densities
(1.25/-1.90 eÅ-3) were found in the asymmetric unit region
occupied by the disordered solvent molecule, indicating that its
modeling was not accurately achieved.
Crystal Data for (BCA)Cu2(C112H84N8Cu2‚C7H8‚1.5H2O).
Experimental and crystal data of (BCA)Cu2 are given in Table 1.
Anisotropic thermal parameters were used for non-H atoms except
for the oxygens of the disordered water molecules (Ow), which
were refined with an isotropic thermal factor. Hydrogens were
placed at calculated positions as riding atoms, except those
corresponding to the water molecules, which were not found. Their
isotropic thermal parameters were fixed at Uiso(H) ) 1.3Uequiv(C)
were recorded on a Bruker DRX-500 AVANCE Fourier transform
spectrometer at the “Centre de Spectrome´trie Mole´culaire de
l’Universite´ de Bourgogne”; chemical shifts are expressed in ppm
relative to toluene-d8 (2.09, 6.98, 7.00, and 7.09 ppm). The electron
spin resonance (ESR) spectra were recorded at the X band (9.6
GHz) in solution on a Bruker ESP 300 spectrometer, from the
“Centre de Spectrome´trie Mole´culaire de l’Universite´ de Bour-
gogne”, equipped with a liquid nitrogen cooling accessory. ESR
spectra are referenced to 2,2-diphenyl-1-picrylhydrazyl (DPPH, g
) 2.0036).
The magnetic susceptibility of the five compounds was measured
over the temperature range 5-300 K at 0.5 and 5 T with a
superconducting quantum interference device (SQUID)
magnetometer SHE 700 and at 0.5, 1, 2.5, and 5 T with a SQUID
magnetometer Quantum Design MPMS. The samples (5-26 mg)
were contained in a kel-F bucket that had been independently
calibrated at the same fields and temperatures. The data were
corrected from diamagnetism using Pascal’s constants.52
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 reference electrode (SCE).
The SCE electrode was separated from the bulk of the solution by
a fritted-glass bridge of low porosity that contained the solvent/
supporting electrolyte mixture. Half-wave potentials were calculated
as E1/2 ) (Epa + Epc)/2 and are referenced to SCE.
(53) Lin, X. Q.; Kadish, K. M. Anal. Chem. 1985, 57, 1498-1501.
(54) COLLECT: Data Collection Software; Nonius BV: Delft, The
Netherlands, 1998.
(55) Otwinowski, Z.; Minor, W. In Methods Enzymol. 1997, 276, 307-
UV-vis spectroelectrochemical experiments were performed
with an optically transparent platinum thin-layer electrode of the
type described in the literature.53 Potentials were applied with an
326 (DENZO software).
(56) Sheldrick, G. M. SHELXS97: Program for the Solution of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(57) OpenMoleN, I.S.S.; Nonius BV: Delft, The Netherlands, 1997.
(58) Sheldrick, G. M. SHELXL97: Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(52) Kahn, O. Molecular Magnetism; VCH: New York, 1993.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7443

Guilard et al.
Table 1. Selected Crystallographic Experimental Data
(BCB)Cu2
(BCA)Cu2
(PCB)Cu2
.
.
.
.
chemical formula
formula weight
temperature, K
wavelength, Å
crystal system
space group
a, Å
C110H82N8Cu2 3CDCl3
2001.02
112(2)
0.71073
triclinic
C112H84N8Cu2 C7H8 1.5H2O
1788.22
173(2)
0.71073
C89H71N8Cu2 CHCl3
1498.99
110(2)
0.71073
monoclinic
P21/c
16.0870(4)
35.109(2)
19.1390(8)
90
95.183(3)
90
10765(1)
4
monoclinic
P21/n
16.7071(3)
10.6719(2)
40.8555(8)
90
100.870(1)
90
7153.7(2)
4
P1h
10.2550(2)
16.3890(3)
29.7910(8)
74.792(1)
81.681(1)
72.504(2)
4596.3(2)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
volume, Å3
Z
µ, mm-1
0.782
0.446
0.762
crystal size, mm3
collected reflections
unique reflections
Rint
0.25 × 0.12 × 0.08
0.30 × 0.20 × 0.04
0.25 × 0.18 × 0.05
28 293
20 205
0.085
46 974
12 733
0.087
28 418
11 613
0.045
θ
max, deg
28.9
24.1
27.4
refinement method
data/parameters
full-matrix least-squares on F2
20 205/1236
1.022
full-matrix least-squares on F
8804/1178
1.124
0.094/0.104
1.15/-0.25
full-matrix least-squares on F2
11 613/944
1.072
goodness-of-fit on F2
R1/wR2a (I > 2σ(I))b
∆Fmax/∆Fmin, eÅ-3
0.101/0.237
1.25/-1.90
0.067/0.135
0.78/-0.71
2
2
2
a R1 ) ∑|Fo - Fc|/∑|Fo| and wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2
.
b I > 3σ(I) for (BCA)Cu2.
(C ) carbon atom bonded to H). One water molecule belonging to
the asymmetric unit was found to be disordered among three
positions, showing Ow‚‚‚Ow distances of 2.30, 2.59, and 3.39 Å.
The corresponding Ow sites occupation factors (sof’s) were fixed
at 1/3 each. A second water molecule was found in the asymmetric
unit partially occupying a unique site and the sof of the Ow atom
was fixed at 1/2. The final agreement factors are R(F) ) 0.094 and
Rw(F2) ) 0.104 for I > 3σ(I) data. The maximum and minimum
rin-5-yl)-8-(2,3,17,18-tetraphenyl-7,8,12,13-tetramethylcorrol-10-
yl)biphenylene, (PCB)H5,41,44,45 2,3,7,8,12,18-hexaethyl-13,17-
dimethyl-5-phenylporphyrin (Me2Et6PhP)H2,41,42 and 7,8,12,13-
tetramethyl-2,3,10,17,18-pentaphenylcorrole (Me4Ph5Cor)H3.41-43
Copper Complexes. The molecular schemes of the copper
derivatives are shown in Chart 1.
(BCA)Cu2, 1,8-Bis-[copper-7,13-diethyl-8,12-dimethyl-2,3,-
17,18-tetraphenylcorrol-10-yl]anthracene. A solution of 400 mg
(0.26 mmol) of the biscorrole dyad (BCA)H6 and 300 mg (2.23
mmol) of copper(II) dichloride in 40 mL of pyridine was stirred
under argon at 40 °C for 2 h, the metalation reaction being
monitored by UV-vis spectroscopy. The solvent was then evapo-
rated under vacuum, and the crude solid thus obtained was dis-
solved in dichloromethane. The organic solution was washed
four times with water to remove any trace of copper salt and then
dried over magnesium sulfate. Chromatography on basic alumina
using CH2Cl2/heptane (60/40) afforded the title product (m )
0.100 g; 23%) which corresponds to the first eluted compound.
MS (MALDI-TOF): m/z ) 1668.99 [M]+•, 1669.04 calcd for
residual electron densities are 1.15/-0.25 eÅ-3
.
Crystal Data for (PCB)Cu2(C89H71N8Cu2‚CHCl3). Experimen-
tal and crystal data of (PCB)Cu2 are given in Table 1. Anisotropic
thermal parameters were used for non-H atoms. Hydrogens were
placed at calculated positions as riding atoms. They were refined
with a global isotropic thermal parameters. The final agreement
factors are R(F) ) 0.0668 and Rw(F2) ) 0.1350 for I > 2σ(I) data.
The maximum and minimum residual electron densities are
0.78/-0.71 eÅ-3
.
Chemicals and Reagents. Absolute dichloromethane (CH2Cl2)
and pyridine (py) were obtained from Fluka Chemical Co. and used
as received. Benzonitrile (PhCN) was purchased from Aldrich
Chemical Co. and distilled over P2O5 under vacuum prior to use.
Neutral alumina (Merck; usually grade III, i.e., deactivated with
6% water) and silica gel (Merck; 70-120 mm) were used for
column chromatography. Analytical thin-layer chromatography was
performed using Merck 60 F254 silica gel (precoated sheets, 0.2
mm thick). Reactions were monitored by thin-layer chromatography
and UV-vis spectroscopy. 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.
C
112H84N8Cu2. UV-vis (CH2Cl2), λmax, nm (ꢀ × 10-3, M-1 cm-1
)
) 410 (130), 570 (25.1). Anal. Calcd for C112H84N8Cu2: C, 80.60;
H, 5.07; N, 6.71. Found: C, 80.71; H, 5.61; N, 6.37.
(BCB)Cu2, 1,8-Bis-[copper-7,13-diethyl-8,12-dimethyl-2,3,17,-
18-tetraphenylcorrol-10-yl]biphenylene. This compound was
prepared in 17% yield (65 mg) as described for (BCA)Cu2, starting
from (BCB)H6 (350 mg, 0.23 mmol). MS (MALDI-TOF): m/z )
1642.70 [M]+•, 1643.00 calcd for C110H82N8Cu2. UV-vis
(CH2Cl2), λmax, nm (ꢀ × 10 -3, M-1 cm-1): 404 (118), 570 (20.8).
Anal. Calcd for C110H82N8Cu2: C, 80.41; H, 5.03; N, 6.82. Found:
C, 80.23; H, 5.36; N, 6.48.
Starting Compounds. The following free-base compounds were
synthesized according to previously described procedures: 1,8-bis-
(7,13-diethyl-8,12-dimethyl-2,3,17,18-tetraphenylcorrol-10-yl)-
anthracene (BCA)H6,42,45,47 1,8-bis-(7,13-diethyl-8,12-dimethyl-
2,3,17,18-tetraphenylcorrol-10-yl)biphenylene (BCB)H6,42,45,47 1-(13,-
17-diethyl-2,3,7,8,12,13,18-hexamethylporphyrin-5-yl)-8-(7,8,-
12,13-tetramethyl-2,3,17,18-tetraphenylcorrol-10-yl)anthracene
(PCA)H5,41,44-46 1-(13,17-diethyl-2,3,7,8,12,18-hexamethylporphy-
(PCA)Cu2,
1-(Copper-2,3,7,8,12,18-hexamethyl-13,17-
diethylporphyrin-5-yl)-8-(copper-2,3,17,18-tetraphenyl-
7,8,12,13-tetramethylcorrol-10-yl)anthracene. This compound
was prepared in 38% yield (150 mg) in pyridine under reflux as
described for (BCA)Cu2, starting from (PCA)H5 (350 mg, 0.27
mmol). MS (MALDI-TOF): m/z ) 1405.19 [M]+•, 1405.73 calcd
for C91H73N8Cu2. UV-vis (CH2Cl2), λmax, nm (ꢀ × 10-3, M-1
cm-1): 403 (198), 533 (16.9), 566 (20.7). Anal. Calcd for
7444 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
Scheme 1
corrole nor of any monometallic derivative could be observed
1
by H NMR or mass spectrometry.45
The copper complexes of the corresponding porphyrin-
corrole, (PCA)H5 and (PCB)H5, were synthesized by heating
the free-base ligand with excess copper(II) chloride in
refluxing pyridine under argon as described in Scheme 1b.
When the metalation was carried out under air and in the
presence of light, a significant decomposition of the complex
was observed. Attempts to isolate the decomposition products
were unsuccessful. Conversely, no decomposition occurs
when the bismacrocycle is metalated under an inert argon
atmosphere, and the copper complexes are obtained in 38
and 27% yields for (PCA)Cu2 and (PCB)Cu2, respectively.
The electronic absorption spectra of (PCA)Cu2 in CH2Cl2
(λmax ) 403 (Soret band), 533, 566 nm) and (PCB)Cu2 in
CH2Cl2 (λmax ) 397 (Soret band), 528, 563 nm) show a
slightly blue-shifted Soret and Q band as compared to the
biscorrole counterparts (BCA)Cu2 (λmax ) 410 (Soret band),
570 nm) and (BCB)Cu2 (λmax ) 404 (Soret band), 569 nm,
see Experimental Section), the wavelength differences be-
tween the Soret band of the porphyrin-corrole and its
biscorrole analogue being equal to 7 nm, independent of the
spacer type (A or B). This slight blue shift in λmax indicates
a larger ring current for the porphyrin chromophore than for
the corrole macrocycle. As already observed in the case of
bimetallic Pacman bisporphyrins,50,60,61 the biphenylenyl
complex (PCB)Cu2 exhibits an electronic absorption spec-
trum with a more blue-shifted Soret band than the anthracenyl
(PCA)Cu2 analogue. This feature is in good agreement with
the cofacial geometry of the porphyrin and corrole rings and
is due to a larger π-π interaction in the case of the PCB
derivative that has a smaller interplanar distance between
the two macrocycles (see following X-ray crystallography
section).41,42
The mass spectral data of the porphyrin-corrole copper
complexes are given in the Experimental Section. The
molecular peak of the biscopper complex, (PCA)Cu2 or
(PCB)Cu2, was observed at m/z ) 1405 and 1379 for
(PCA)Cu2 and (PCB)Cu2, respectively, and the data are in
perfect agreement with the expected molecular formula. No
additional major peaks are seen.
ESR and 1H NMR Characterizations. Further indications
of the nature of the biscopper complexes are provided by
ESR and 1H NMR spectroscopies (in toluene solutions) and
also by the magnetic susceptibility determination on pow-
dered samples in the 5-300 K temperature range as
discussed in the next section.
C91H73N8Cu2: C, 77.75; H, 5.23; N, 7.97. Found: C, 77.81; H,
5.71; N, 7.54.
(PCB)Cu2,
1-(Copper-2,3,7,8,12,18-hexamethyl-13,17-di-
ethylporphyrin-5-yl)-8-(copper-2,3,17,18-tetraphenyl-7,8,12,13-
tetramethylcorrol-10-yl)biphenylene. This compound was pre-
pared in 27% yield (45 mg) in pyridine under reflux as described
for (BCA)Cu2, starting from (PCB)H5 (150 mg, 0.12 mmol).
MS (MALDI-TOF): m/z ) 1379.27 [M]+•, 1379.69 calcd for
C89H71N8Cu2. UV-vis (CH2Cl2), λmax, nm (ꢀ × 10-3, M-1 cm-1):
397 (247), 528 (16.4), 563 (21.3). Anal. Calcd for C89H71N8Cu2:
C, 77.48; H, 5.19; N, 8.12. Found: C, 77.67; H, 4.88; N, 7.86.
(Me2Et6PhP)Cu, Copper-2,3,7,8,12,18-hexaethyl-13,17-dimethyl-
5-phenylporphyrin. This compound was prepared in 38% yield
(42 mg), as described for (BCA)Cu2, starting from (Me2Et6PhP)H2
(100 mg, 0.17 mmol). MS (MALDI-TOF): m/z ) 644.11 [M]+•,
644.36 calcd for C40H44N4Cu. UV-vis (CH2Cl2), λmax, nm (ꢀ ×
10-3, M-1 cm-1): 403 (318), 529 (15.0), 565 (20.0). Anal. Calcd
for C40H44N4Cu: C, 74.56; H, 6.88; N, 8.69. Found: C, 74.95; H,
6.39; N, 8.38.
(Me4Ph5Cor)Cu, Copper-7,8,12,13-tetramethyl-2,3,10,17,18-
pentaphenylcorrole. This compound was prepared in 37%
yield (48 mg), as described for (BCA)Cu2, starting from
(Me4Ph5Cor)H3 (120 mg, 0.16 mmol). MS (MALDI-TOF): m/z )
795.11 [M]+•, 795.46 calcd for C53H39N4Cu. UV-vis (CH2Cl2),
λ
max, nm (ꢀ x 10-3, M-1 cm-1): 410 (101), 569 (17.3). Anal. Calcd
for C53H39N4Cu: C, 80.03; H, 4.94; N, 7.04. Found: C, 79.67; H,
4.76; N, 6.88.
Results and Discussion
Synthesis and Physicochemical Characterization. The
complexes (BCA)Cu2 and (BCB)Cu2 were synthesized by
heating the corresponding free-base ligand, (BCA)H6 or
(BCB)H6, with excess CuCl2 in pyridine at 40 °C under argon
(Scheme 1a).59 The Soret band of (BCA)Cu2 is located at
410 nm, and a Q band is observed at 570 nm as com-
pared to 410 and 569 nm for the monocorrole derivative,
(Me4Ph5Cor)Cu, in CH2Cl2. The UV-vis spectra of
(BCA)Cu2 and (BCB)Cu2 display an intense Soret band
indicating that the aromatic system of both bismacrocycles
remains unaltered after metalation. Conversely, it should be
noted that, under the same reaction conditions, nickel
bisoxocorroles are formed by metalation of the same bis-
corroles with a nickel salt.45
The ESR spectrum of the porphyrin-corrole derivative,
(PCA)Cu2, in frozen toluene solution at 100 K (see Sup-
porting Information) is centered at g| ) 2.21 and g ) 2.05
and shows a four-line hyperfine splitting due to the Cu
nucleus (I ) /2, a|Cu ) 203 G) as well as a nine-line
3
Mass spectral analysis confirms the structures of
(BCA)Cu2 and (BCB)Cu2 by exhibiting a single ion pattern
at m/z ) 1669 for the anthracenyl derivative and at m/z )
1643 for the biphenylenyl derivative. No trace of a bisoxo-
superhyperfine splitting due to the four porphyrin nitrogens,
which is clearly observed in the high-field part of the
(60) Bolze, F.; Gros, C. P.; Drouin, M.; Espinosa, E.; Harvey, P. D.; Guilard,
R. J. Organomet. Chem. 2002, 89-97.
(61) Bolze, F.; Drouin, M.; Harvey, P. D.; Gros, C. P.; Guilard, R. J.
Porphyrins Phthalocyanines 2003, 7, 474-483.
(59) Will, S.; Lex, J.; Vogel, E.; Schmickler, H.; Gisselbrecht, J.-P.;
Haubtmann, C.; Bernard, M.; Gross, M. Angew. Chem., Int. Ed. Engl.
1997, 36, 357-361.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7445

Guilard et al.
spectrum (a N ) 17.7 G). No forbidden transition is observed
in the half-field part of the ESR spectrum, indicating the
absence of any Cu-Cu interaction62 and the presence of a
“pure” Cu(II) porphyrin and diamagnetic Cu(III) corrole
species as expected. The shape of the ESR spectrum of
(PCB)Cu2 is relatively close to that of (PCA)Cu2. The signal
of (PCB)Cu2 is centered at g| ) 2.18 and g ) 2.05 and
exhibits the same four-line hyperfine splitting due to the Cu
nucleus (I ) /2, a|Cu ) 208 G) and the nine-line superhy-
3
perfine splitting from the four porphyrin nitrogens at high
field (a N ) 17.2 G). Those data clearly indicate the presence
of one ESR-active Cu(II) species in the cofacial porphyrin-
corrole system, and this would be in the porphyrin macro-
cycle. The ESR spectra of (PCA)Cu2 and (PCB)Cu2 do not
significantly differ from those of Cu(II) porphyrins and other
N-donor ligand complexes for which a broad resonance
signal at g ) 2.2-2.3 is typical.62 However, in the case of
(PCB)Cu2, extra lines appear at 3117 and 3600 G that could
indicate the presence of a small amount of a radical (i.e., a
Cu(II)• corrole species). As for (PCA)Cu2, no forbidden half-
field transition was observed, indicating the absence of any
Cu-Cu interaction.
Figure 1. 1H NMR spectra (500 MHz, toluene-d8, δ) of (BCB)Cu2
recorded at different temperatures.
of two types of 1H NMR spectra (i.e., a diamagnetic spectrum
and a paramagnetic spectrum, the first one being attributable
to the Cu(III) derivative and the second one, to a Cu(II)•
species). The strongest temperature effect is clearly observed
for the alkyl resonances at around 4.0 ppm with a low-field
chemical shift change of +0.7 ppm between 183 and 360 K
for the (BCB)Cu2 complex (see Figure 1). Also the signifi-
cant signal broadening above 320 K indicates a stronger
The ESR spectrum of (BCA)Cu2 clearly indicates the
presence of a Cu(II)• corrole species (g| ) 2.18, a|Cu ) 201
1
N
G; g ) 2.08, a ) 17.0 G), the two Cu(II)• corrole
paramagnetism when increasing the temperature. These H
NMR results are in good agreement with the presence of
unpaired spin density on some proton sites. No clear-cut
assignment is possible due to the overlapping resonances and
poorly resolved signals.
macrocycles being in the same environment, which is not
the case for (BCB)Cu2. Two types of resonances for the
Cu(II)• corrole species are observed in the ESR spectrum of
(BCB)Cu2. However, the overlap of the signals and their
very low intensity do not allow assignment of the ESR
resonances, and the presence of the diamagnetic Cu(III)
corrole complex has to be considered as the major contribu-
tion.
The observed shifts are reversible upon cooling the sample
back to 183 K. A similar trend is also observed in the case
of (BCA)Cu2 as well as in the case of the monocorrole
species. These results suggest a developing paramagnetism
upon raising the temperature. A similar result was earlier
observed in the case of copper octafluorocorroles,17 copper
triphenylcorroles,39 and copper â-octaalkylcorroles.59 In all
cases, the authors attributed their observations to a thermally
accessible copper(II) π-cation radical excited state, the
diamagnetic Cu(III) ground state being the dominant species
whatever the temperature.
In summary, the variable-temperature ESR and NMR
experiments carried out with the four cofacial biscopper
derivatives show the presence of an equilibrium between
(Cor)Cu(II)• and (Cor)Cu(III), the (Cor)Cu(III) species being
the major one, as clearly evidenced by the NMR studies (i.e.,
the diamagnetic NMR spectra).
Magnetic Properties of the Porphyrin-Corrole and
Biscorrole Derivatives. A similar trend can be seen from
the magnetic susceptibility experiments in the solid state.
The magnetic susceptibility of all compounds has been
investigated in the temperature range 5-300 K at four
fields from 0.5 to 5 T. It is illustrated in Figure 2 as the
temperature dependence of the product of the molar magnetic
susceptibility (øM) by temperature. All compounds exhibit
the same behavior characterized by a constant value of øMT
from room temperature down to ca. 10 K. This excludes the
presence of a noticeable magnetic exchange coupling be-
tween the two copper centers in the biscorrole and porphy-
The (Me4Ph5Cor)Cu complex is also ESR-active, but the
signal-to-noise ratio, as observed for biscorrole derivatives,
is very weak compared to that of the monocopper porphyrin
Cu(II) complexes such as (Me2Et6PhP)Cu or (TPP)Cu. This
result indicates that the amount of Cu(II)• corrole is small
compared to the amount of the major Cu(III) complex and
that the presence of a non-ESR active species such as a
Cu(III) derivative has to be considered mainly at low
temperature. The ESR spectra for each derivative were also
recorded at variable temperatures up to 373 K. The isotropic
spectra give no further indication of an increasing ratio of
paramagnetic species at higher temperature.
The influence of temperature on the distribution of species
in each oxidation state is more evident from the variable-
temperature NMR studies (in toluene solution). The shape
of the 1H NMR spectrum is in agreement with the presence
of a dominant diamagnetic species, but heating of the sample
in the NMR magnet from 183 to 360 K causes line shifts
and line broadening. This is shown in Figure 1 in the case
of the (BCB)Cu2 derivative. Line broadening and a chemical
shift temperature dependence are not observed for each
resonance. This behavior can be understood as an overlapping
(62) Eaton, S. S.; Eaton, G. R.; Chang, C. K. J. Am. Chem. Soc. 1985,
107, 3177-3184.
7446 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
Figure 2. Temperature dependence of øMT for (Me4Ph5Cor)Cu, (BCB)-
Cu2, (BCA)Cu2, (PCA)Cu2, and (PCB)Cu2. Data collected in the temperature
range 5-300 K.
rin-corrole derivatives. In addition, a small decrease is
observed at low temperatures (T < 10 K) that can be
attributed to intermolecular interactions in the solid. The
monocorrole complex presents a constant øMT at 0.1 cm3 K
mol-1 over the whole temperature range, which illustrates
the occurrence of a small paramagnetic contribution. The
two biscorroles exhibit a plateau at øMT ) 0.17 and 0.27
cm3 K mol-1 for the BCB and BCA complexes, respectively.
Consistent with the dinuclear nature of the compounds, these
values are roughly double that of the monocorrole derivative.
Nevertheless, they show a significant dependency on the
nature of the spacer for the biscorrole complexes, which may
be ascribed to their different abilities to mediate π-π
interactions as revealed in ESR and electrochemistry (see
below). In addition, the two porphyrin-corroles exhibit very
similar behavior with øMT values of 0.49(2) cm3 K mol-1.
The latter value can be explained by considering that it
corresponds to the addition of the copper(II) porphyrin
contribution to that of the copper corrole. Indeed, from the
g values measured by ESR spectroscopy one can estimate
that the copper porphyrin will contribute to a value of 0.41
cm3 K mol-1 for the product øMT. A contribution of 0.08(2)
cm3 K mol-1 from the copper corrole moiety to the product
øMT can therefore be estimated, consistent with that measured
for the monocorrole. In this case, the nature of the spacer
has no effect because the copper(II)-porphyrin moiety has
no radical character.
The weak paramagnetism exhibited by the copper cor-
role moiety is not consistent with a solely Cu(III) descrip-
tion, which would be diamagnetic. Similarly, it is also
not consistent with a (Cor)Cu(II)• formulation because this
species would exhibit either a spin of S ) 1 (strong
ferromagnetic coupling), a spin of S ) 0 (strong antiferro-
magnetic coupling), or a temperature-dependent spin (inter-
mediate magnetic coupling). Thus, the results of magnetic
measurements are in accordance with those of the ESR and
NMR experiments. The monocorrole copper, biscorrole
biscopper, and porphyrin-corrole biscopper derivatives have
to be considered as an equilibrium between compounds with
a major Cu(III) metal center and a minor Cu(II) radical one,
Figure 3. ORTEP view of the (BCB)Cu2 dimer: (a) lateral and (b) apical
views. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn
at the 50% probability level.
Figure 4. ORTEP view of the (BCA)Cu2 dimer: (a) lateral and (b) side
views. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn
at the 50% probability level.
independent of temperature. No significant temperature
dependence is observed in the solid state.
Description of the (BCB)Cu2, (BCA)Cu2, and
(PCB)Cu2 Molecular Structures. Lateral and apical views
of the (BCB)Cu2, (BCA)Cu2, and (PCB)Cu2 molecular
structures are given in Figures 3-5, respectively. Table 1
gives crystal data and some experimental and refinement
details for the three crystal structures. Selected Cu-N bond
distances and geometrical parameters describing the
molecular conformations of the reported complexes are sum-
marized in Tables 2 and 3. Along with these data are given
Inorganic Chemistry, Vol. 43, No. 23, 2004 7447

Guilard et al.
mean plane, the relative position of the nitrogen atoms (lying
above and below the plane at 0.07/0.16 Å and at 0.01/0.02
Å, by pairs of opposite pyrrole groups, respectively) indicates
an approximate saddle conformation. In (BCA)Cu2, the
corrole rings are slightly wave-shaped, exhibiting two
adjacent C-meso atoms at the same side of the least-squares
mean plane (at 0.02/0.03 Å and 0.03/0.06 Å, for each
macrocycle) and a third one at the other side of the calculated
plane (at 0.04 and 0.17 Å, for the corresponding macro-
cycles). The macrocyclic rings of (DPB)Cu2 and (DPA)Ni2
are saddle-shaped, although for (DPX)Cu2 and (DPX)Ni2
they are ruffle-shaped and in (BOCA)Ni2 they are a mixture
of irregular saddle, ruffle, and doming distortions. Comparing
these face-to-face complexes, the corrole, and porphyrin rings
show a large spread of distortions between the four com-
monly identified conformations, namely, saddle, wave, ruffle,
and dome. Obviously, ring conformations are the result of
several kinds of interactions, including coordination bonds,
steric repulsions between substituents, packing forces, and
the eventual macrocyclic π-π and metal-metal interactions.
As expected, because of the mixture of all of these contribu-
tions, there is no direct evidence of any correlation between
the observed ring conformations and the metals, macrocycles,
or aromatic spacers. Thus, for instance, even if (DPX)Zn2,
(DPX)Cu2, and (DPX)Ni2 have the same two porphyrin
macrocycles and the same identical aromatic spacers, the
(DPX)Zn2 derivatives show for both porphyrin macrocycles
a wave conformation, although (DPX)Cu2 and (DPX)Ni2
both exhibit ruffle conformations.65
Aromatic Spacers. Although the biphenylenyl spacer is
almost planar in (PCB)Cu2 and slightly distorted in
(BCB)Cu2 (the largest and the mean deviations from their
respective mean planes being 0.05 and 0.03 Å, and 0.09 and
0.06 Å, respectively), the anthracenyl spacer exhibits a
more significant distortion in (BCA)Cu2 (the corresponding
deviations being 0.13 and 0.07 Å). Throughout the series
(PCB)Cu2, (BCB)Cu2, and (BCA)Cu2, the observed defor-
mations increase and lead to a concomitant increasing of the
torsion angle between the Cmeso,1, Canch,1, Canch,2, and Cmeso,2
atoms, reflecting the twisted degree of the spacer (see Figure
6). The angle values are 5.0, 11.2, and 20.4° for (PCB)Cu2,
(BCB)Cu2, and (BCA)Cu2, respectively. This deformation
correlates with the relative position of the macrocycles in
each complex, going from a closely eclipsed conforma-
tion for (PCB)Cu2 to a twisted conformation for (BCA)Cu2;
the average values of the four smallest torsion angles
N1j-M1-M2-N2k with j, k ) 1 to 4 are 7.0, 7.9, and 17.6°,
for (PCB)Cu2, (BCB)Cu2, and (BCA)Cu2, respectively.
Bond Coordination Geometries. In (BCB)Cu2,
(BCA)Cu2, and (PCB)Cu2, the copper atoms are tetraco-
ordinated by the four pyrrole nitrogens. Although the
Cu1-Npyr bond coordination distances corresponding to the
corrole ligands range from 1.89 to 1.92 Å (see Table 3),
they are roughly 0.1 Å longer in the porphyrin moiety of
(PCB)Cu2, ranging from 1.99 to 2.01 Å. Similar geometries
to those found in the porphyrin moiety of (PCB)Cu2 are
found for the corresponding coordination distances observed
in the bisporphyrin complexes (DPB)Cu2 and (DPX)Cu2
Figure 5. ORTEP view of the (PCB)Cu2 dimer: (a) lateral and (b) apical
views. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn
at the 50% probability level.
the corresponding values for other face-to-face homo-
bimetallic copper complexes ((DPB)Cu2,63 (BCmS)Cu2,64 and
(DPX)Cu265) as well as the related nickel derivatives
((BOCA)Ni2,45 (DPA)Ni2,63 and (DPX)Ni265) where DPB
represents diporphyrin biphenylenyl, BCmS is bismesocorrole
dibenzothiophene, DPX is diporphyrin 9,9-dimethylxanthene,
BOCA is bisoxocorrole anthracenyl, and DPA represents
diporphyrin anthracenyl; see Chart 2. Data for two mono-
corrole copper complexes ((TPCm)Cu,39 (TETMC)Cu59) are
also listed in Tables 2 and 3 where TPCm represents meso-
triphenylcorrole and TETMC is tetraethyltetramethylcorrole.
Macrocycle Conformation. The macrocycles are slightly
distorted in the three reported complexes, the mean C
deviations from their two least-squares mean planes (MDMP,
see Table 2) being 0.13/0.15 for (BCB)Cu2, 0.12/0.25 for
(BCA)Cu2, and 0.23/0.23(3) Å for (PCB)Cu2. Both corrole
rings are ruffled in (BCB)Cu2, as indicated by the displace-
ments of the meso carbon atoms (C-meso) above and below
the macrocyclic mean planes. Thus, for this complex, the
C-meso atoms anchored to the spacer are 0.12 and 0.18 Å
below their respective planes, although the other two are
0.09/0.18 and 0.12/0.19 Å above each plane. Although
similar features are found in the ruffled corrole moiety of
(PCA)Cu2 (showing the respective C-meso atoms at 0.15 Å
below and at 0.02/0.21 Å above the macrocycle mean plane),
three of them are found above the corresponding plane (at
0.02, 0.02, and 0.07 Å) in its porphyrin moiety, and the fourth
one is observed below the plane (at 0.02 Å). In that case,
where the four C-meso atoms are close to the least-squares
(63) Fillers, J. P.; Ravichandran, K. G.; Abdalmuhdi, I.; Tulinsky, A.;
Chang, C. K. J. Am. Chem. Soc. 1986, 108, 417-424.
(64) Pacholska, E.; Espinosa, E.; Guilard, R. J. Chem. Soc., Dalton Trans.
2004, in press.
(65) Chang, C. J.; Deng, Y.; Heyduc, A. F.; Chang, C. K.; Nocera, D. J.
Inorg. Chem. 2000, 39, 959-966.
7448 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
Table 2. Selected Geometrical Parameters Derived from the Molecular Structures of (BCB)Cu2, (BCA)Cu2, (PCB)Cu2, and Other Related Complexes
a
b
d(Ct-Ct)
(Å)
d(M-M)
(Å)
∆d2
MDMP
(Å)
MPS
(Å)
M-LSMP
θ
(deg)
R
(deg)
L
(Å)
d(a-b)
(Å)
d(c-d)
(Å)
∆d1
(Å)
(Å)
(Å)
refd
(BCB)Cu2
(BCA)Cu2
(PCB)Cu2
4.13
6.34
3.73
4.02
6.35
3.63
-0.11
0.01
-0.10
0.13/0.15
0.12/0.25
0.23/0.23
3.65
6.13
3.48
0.05/0.16
0.10/0.11
0.12/0.10
9.2
18.3
5.3
29.3
9.3
23.5
2.02
1.02
1.49
3.79
4.98
3.79
3.78
5.26
3.79
-0.01
0.28
0.00
c
c
c
(DPB)Cu2
3.86
7.66
3.98
4.80
3.81
7.68
3.91
4.72
-0.05
0.02
-0.07
-0.08
0.23/0.23
0.18/0.19
0.12/0.15
0.07/0.08
3.50
5.91
3.60
3.42
0.02/0.09
0.03/0.14
0.05/0.10
0.05/0.03
4.4
5.2
4.6
0.5
25.0
39.5
25.3
45.1
1.63
4.87
1.74
3.40
3.80
5.25
4.59
3.80
6.27
4.32
0.00
1.02
-0.27
63
64
65
59
(BCmS)Cu2
(DPX)Cu2
[(TETMC)Cu]2
(DPX)Ni2
(BOCA)Ni2
(DPA)Ni2
4.70
4.71
4.59
4.69
4.68
4.57
-0.01
-0.03
-0.02
0.14/0.29
0.17/0.22
0.39/0.43
3.60
4.29
3.87
0.00/0.01
0.05/0.04
0.05/0.02
2.6
7.8
3.9
40.0
24.0
32.5
3.02
1.91
2.47
4.66
4.93
4.96
4.47
4.89
4.93
-0.19
-0.04
-0.03
65
45
63
a ∆d2 ) d(M-M) - d(Ct-Ct). b ∆d1 ) d(c-d) - d(a-b). c This work. d To compare homogeneous quantities, we recalculated selected geometrical
parameters from the literature using the same definitions as indicated in Figure 6.
Table 3. Selected Bond Lengths and Distances from the Least-Squares Mean Plane (LSMP) to the Coordinated Metal Derived from the Molecular
Structures of (BCA)Cu2, (BCB)Cu2, (PCB)Cu2, and Other Related Complexes
63,a
64
65
(BCA)Cu2
(BCB)Cu2
(PCB)Cu2
(DPB)Cu2
(BCmS)Cu2
(DPX)Cu2
(TPCm)Cu39
(TETMC)Cu59,b
Cu1-N (C/P)c
Cu2-N (C/P)c
1.899 (8)
1.893 (9)
1.903 (9)
1.917 (9)
1.887 (5)
1.894 (5)
1.916 (4)
1.916 (4)
1.897 (4)
1.904 (4)
1.909 (4)
1.913 (4)
2.002
1.991
1.996
1.997
1.892 (6)
1.895 (6)
1.883 (6)
1.898 (6)
2.008(9)
2.011(9)
2.001(9)
2.016(9)
1.891 (4)
1.892 (4)
1.893 (4)
1.894 (4)
1.868 (5)
1.872 (6)
1.885 (5)
1.896 (5)
1.898 (9)
1.900 (10)
1.911 (9)
1.911 (9)
1.894 (5)
1.897 (5)
1.901 (5)
1.906 (5)
1.993 (4)
2.004 (4)
2.007 (4)
2.008 (4)
1.993
1.994
1.997
2.002
1.897 (5)
1.889 (6)
1.894 (6)
1.904 (6)
1.980(10)
2.013(9)
1.992(9)
1.995(9)
1.867 (6)
1.879 (6)
1.880 (6)
1.889 (6)
a Estimated standard deviations from average bond lengths are 0.002 and 0.004 Å for shorter and longer geometries, respectively. b Two crystallographically
independent copper corrole molecules are found in the asymmetric unit. c The symbol “C/P” means corrole (C) or porphyrin (P) macrocycle. TPCm
meso-triphenylcorrole, TETMC ) tetraethyltetramethylcorrole.
)
Chart 2
Figure 6. Series of aromatic linking units in this work and in the literature
used to join corrole or porphyrin monomers to form the cofacial biscorrole
or porphyrin-corrole dimers, where the a-b and c-d distances are defined.
The other geometrical parameters are also defined.
than those found in other reported corrole ligands. The
coordination distances shown in the monometallic (TPCm)-
Cu complex, also incorporating a meso-aryl-substituted
corrole, are within the range of values found for (BCmS)-
Cu2. (In (TPCm)Cu, the four Cu-Npyr distances are 1.89 Å.39)
The other metallocorrole complex described in the literature,
namely (TETMC)Cu, exhibits the shortest copper-ligand
(Table 2). In the (BCmS)Cu2 complex, where meso-aryl-
substituted corroles are present,64 the distances range from
1.88 to 1.90 Å, indicating slightly stronger interactions
Inorganic Chemistry, Vol. 43, No. 23, 2004 7449

Guilard et al.
distances for these complexes (1.86-1.87 Å). All of the
reported Cu-Npyr bond lengths lie within the
characteristic copper(III)-N(donor ligand) range of distances
(1.804-1.907 Å),59 supporting the existence of Cu(III)
centers in the monometalated and bimetalated corrole copper
complexes discussed above.
complexes, the centroid-centroid distance (respectively, 4.13
and 3.73 Å) is ∼0.1 Å longer than the related copper-copper
geometry (4.02 and 3.63 Å) (i.e., ∆d2 < 0 and equal to -0.11
and -0.10 for (BCB)Cu2 and (PCB)Cu2, respectively). Thus,
all of these geometrical features indicate an interaction
between both monometalated moieties in (BCB)Cu2 and
(PCB)Cu2. In particular, it should be pointed out that, for
these complexes, the short MPS geometries are not ac-
companied by large lateral shifts (L) between macrocycles,
these two kinds of values being the signature of π-π
interactions only. Thus, along with the short MPS and M-M
geometries, the low lateral shift values found for (BCB)Cu2
and (PCB)Cu2 (L ) 2.02 and 1.49 Å, respectively) further
support both π-π and copper-copper interactions in the
crystal. This contrasts with the case of (BCA)Cu2, where a
solvent molecule is located inside the complex cavity, and
the Ct-Ct and M-M distances are large and similar to each
other (6.34 and 6.35 Å, ∆d2 ) 0.01 Å), thus indicating that
the M-M interactions are weak in (BCA)Cu2.
Similar geometrical trends are also found in (DPB)Cu2
and (DPX)Cu2 (∆d1 ) 0 and -0.27 Å, MPS ) 3.50 and
3.60 Å, θ ) 4.4 and 4.6°, d(M-M) ) 3.81 and 3.91 Å, L )
1.63 and 1.74 Å, and ∆d2 ) d(M-M) - d(Ct-Ct) ) -0.05
and -0.07 Å, respectively). The latter case is particularly
interesting due to the fact that the X spacer exhibits a
d(a-b) distance (4.59 Å) greater than that of the three other
examined complexes, (BCB)Cu2, (PCB)Cu2, and (DPB)Cu2,
which incorporate a biphenylenyl linking unit (d(a-b) )
3.79, 3.79, and 3.80 Å, respectively). The short M-M and
MPS distances observed in (DPX)Cu2 are because of
deformation of the long X spacer, which folds on two
equivalent halves through the O‚‚‚C direction and leads to
an angle of 165.9° between them. Thus, the d(a-b) distance
in this complex is significantly shorter than the maximum
allowed value for a planar conformation of the spacer (∼5.0
Å). This folding, along with the reported (DPX)Cu2 geo-
metrical parameters (which are close to those of (BCB)Cu2,
(PCB)Cu2, and (DPB)Cu2, despite the significant difference
between their d(a-b) distances), supports an interaction
between the macrocyclic moieties in (DPX)Cu2 as pointed
for the three other considered compounds.
π-π or Metal-Metal Interactions. In Figure 6, the
distance between the macrocycle meso carbon 1 and meso
carbon 2 and that of the spacer-anchored carbon 1 and
anchored carbon 2 are defined as d(c-d) and d(a-b),
respectively. Table 2 shows selected geometrical parameters
derived from the molecular structures of (BCA)Cu2,
(BCB)Cu2, and (PCB)Cu2. The macrocyclic centers (Ct) were
calculated as the centroids of the four nitrogen atoms
belonging to each macrocycle. The interplanar angles (θ)
were measured as the angle between the two macrocyclic
least-squares mean planes (LSMPs). Plane separations were
measured as the perpendicular distance from one macrocycle
least-squares plane to the center of the other macrocycle;
reported mean plane separations (MPS) were the average of
the two plane separations for each dimer. The slip angles
(R) were calculated as the angle between the vector joining
the two macrocyclic centers and the unit vectors normal to
the two macrocyclic least-squares planes (R ) (R1 + R2)/2,
where Ri ) angle(Ct-Ct, ni), i ) 1, 2). Lateral shift is
defined as L ) d(Ct-Ct) × sin R.
The a-b distance (see Figure 6), which mainly depends
on the spacer nature, is close to 3.79 Å for the biphenylene
group in both (BCB)Cu2 and (PCB)Cu2 and close to 4.98 Å
for the anthracene moiety of (BCA)Cu2. Similar values
(roughly (0.01 Å) are given in the literature for other
face-to-face complexes incorporating these spacers.60,61,66
Molecular structures showing coordinated or inserted
molecules in the complex cavity can lead to significant
differences between the d(c-d) and d(a-b) distances, as is
the case for the (BCA)Co2 complex where ∆d1 ) d(c-d) -
d(a-b) ) 0.30 Å.42 This is also observed in (BCA)Cu2 where
a toluene solvent molecule is placed inside the cavity roughly
parallel to both macrocycles (the dihedral angles between
the macrocycles least-squares mean planes and that of the
inserted molecule are 7.7° and 11.3°, respectively), leading
to a difference of ∆d1 ) 0.28 Å.
Steric interactions between substituents can also play a
role in the positive values ∆d1. However, in both (BCB)Cu2
and (PCB)Cu2, where d(a-b) is shorter than in (BCA)Cu2,
repulsive interactions lead to important deformations in the
macrocycles on the opposite side of the spacer (Figures 3
and 5) rather than induce an open-cavity geometry (∆d1 >
0). In particular, it is noteworthy that the ∆d1 values
calculated for (BCB)Cu2 and (PCB)Cu2 are equal to -0.01
and 0 Å, respectively. Indeed, considering these values along
with both the short MPS distances (3.65 and 3.48 Å,
respectively) and the small θ angles (9.2 and 5.3°) seems to
indicate that an attractive interaction exists between the
macrocycles in each complex. In addition, we note that the
metal centers are slightly displaced from their respective
ligand LSMP toward each other, the Cu-LSMP distances
being close to 0.12/0.10 Å and 0.05/0.16 Å. For these
The other two biscopper complexes included in Table 2,
namely (BCA)Cu2 and (BCmS)Cu2,64 exhibit large M-M and
MPS values and positive ∆d1 and ∆d2 differences. Although
for the former compound this is due to the toluene solvent
molecule inserted inside the complex cavity, the large ∆d1
(0.28 and 1.02 Å, respectively) and lateral shift values (1.02
and 4.87 Å, respectively) for the latter result from the
presence of two methyl groups (each belonging to a mesityl
moiety of one macrocycle) that are inside the complex cavity
and are involved in C-H‚‚‚M contacts. (With the hydrogen
atoms placed at calculated positions, the observed d(H‚‚‚M)
distances are 2.58 and 2.66 Å.)
The three homobimetallic nickel complexes (DPX)Ni2,65
63
(BOCA)Ni2,45 and (DPA)Ni2 present calculated negative
(66) Harvey, P. D.; Proulx, N.; Martin, G.; Drouin, M.; Nurco, D. J.; Smith,
K. M.; Bolze, F.; Gros, C. P.; Guilard, R. Inorg. Chem. 2001, 40,
4134-4142.
7450 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
∆d1 and ∆d2 values as well as small interplanar angles (θ )
2.6, 7.8 and 3.9°) and short interplanar distances (MPS )
3.60, 4.29 and 3.87 Å, see Table 2). Although in (DPA)Ni2
the metal-metal distance is slightly shorter than that found
in (DPX)Ni2 and in (BOCA)Ni2 (4.57 Å compared to 4.69
and 4.68 Å, respectively), these two latter complexes exhibit
an almost equivalent geometry despite both the different
oxocorrolato ligand incorporated in (BOCA)Ni2 (inhibiting
partially the full delocalization of the electrons throughout
the macrocycle) and the different spacer incorporated in
(DPX)Ni2, which does not fold as much as in (DPX)Cu2 (6.4
compared to 14.1°, respectively). As in the case of the four
homobimetallic copper complexes, (BCB)Cu2, (PCB)Cu2,
(DPB)Cu2, and (DPX)Cu2, the similar molecular geometries
found for these three quite different bisnickel complexes
suggest π-π or metal-metal interactions. By comparison
of the MPS and the M-M distances calculated for both
biscopper and bisnickel series, we systematically observe
shorter geometries for the former complexes, indicating
stronger interactions in the homobimetallic copper com-
pounds. An inspection of the ∆(MPS) and ∆(M-M) differ-
ences observed between the complexes of both series shows
that, in all cases, ∆(M-M) is greater than ∆(MPS), leading
to the conclusion that the difference between Cu‚‚‚Cu and
Ni‚‚‚Ni interactions is more important than that between their
corresponding ligands.
Figure 7. Cyclic voltammograms of (a) (BCA)Cu2 (1.5 × 10-3 M), (b)
(Me4Ph5Cor)Cu (1.2 × 10-3 M), and (c) (BCB)Cu2 (1.5 × 10-3 M) in
CH2Cl2 containing 0.1 M TBAP. Scan rate ) 0.1 V/s.
Table 4. Summary of Half-Wave Potentialsa
oxidation
reduction
Despite the absence of a linking spacer, it is noteworthy
that the metallocorrole (TETMC)Cu crystallizes as a dimer,59
showing two crystallographically independent copper corrole
molecules in the dimer moiety. In the crystal structure of
this compound, the macrocycles are planar (MDMP )
0.07/0.08 Å), the metal centers lying on the planes
(M-LSPM ) 0.05/0.03 Å). The interplanar distance (3.42
Å) is shorter and the interplanar angle is smaller (0.5°) than
values observed in (BCB)Cu2, (PCB)Cu2, (DPB)Cu2, and
(DPX)Cu2 (MPS ) 3.65, 3.48, 3.50, and 3.60 Å, θ ) 9.2,
5.3, 4.4, and 4.6°, respectively). In contrast, the metal-metal
distance of the (TETMC)Cu dimer (4.72 Å) is significantly
longer and its lateral shift value (3.40 Å) is larger than in
the face-to-face bimetallic copper complexes reported in this
study (d(Cu-Cu) ) 4.02, 3.63, 3.81, and 3.91 Å, L ) 2.02,
1.49, 1.63, and 1.74 Å, respectively). These geometrical
features therefore suggest that (i) a mainly π-π interaction
takes place between the macrocycles of the [(TETMC)Cu]2
dimer and (ii) a mainly weak interaction exists between the
metal centers of this molecular unit. Weak metal-metal
interactions are consistent with the lack of any detectable
influence on the ESR and magnetic measurement data.
However, the interactions between the two π systems must
be strong as it is reflected in the electrochemistry of the dyads
as discussed below.
metal ion compound
Cu
(Me4Ph5Cor)Cu
(BCA)Cu2
(BCB)Cu2
1.28e
0.69
0.75 0.62
0.85 0.45 -0.36 -0.51
-0.20
-0.20
1.17
1.38e
Cob
Coc
2Hd
Znd
(Me4Ph5Cor)Co
(BCA)Co2
(BCB)Co2
(MPA)Cof
(DPA)Co2
(DPB)Co2
0.72
0.89
0.83
0.47
0.47
-0.16
-0.23
0.44 0.27 -0.31 -0.60
-0.06e
0.05
-1.53
-1.60
0.17 0.00 -1.71 -1.90
g
(C2diE)H2
0.90
0.85
0.92
0.39
0.43 0.31
0.37 0.14
-1.81
-1.92
-2.06
(DPA)H4
(DPB)H4
(C2diE)Zn
(DPA)Zn2
(DPB)Zn2
0.63
0.60
0.22
0.23 0.16
-2.00
-2.11
-2.15
0.85 0.64 0.21 0.06
a Data obtained in CH2Cl2, 0.1 M TBAP for Cu complexes and in PhCN,
0.1 M TBAP for the reminder of the compounds. b From ref 42. c From ref
68. d From ref 70. e Ep for a scan rate of 0.1 V/s. f Monomeric cobalt
porphyrin. g Monomeric free-base porphyrin.
The monocorrole, (Me4Ph5Cor)Cu, undergoes one
reversible reduction (Figure 7b) at E1/2 ) -0.20 V; there
are also two oxidations at E1/2 ) 0.69 V and Epa ) 1.28 V
for a scan rate of 0.1 V/s. The reversible reduction,
which is metal-centered,30 results in the formation of
[(Me4Ph5Cor)CuII]-, and the reduction potential of -0.20
V is comparable to the E1/2 values of -0.20 to -0.24 V for
the reduction of the related Cu(III) triphenylcorroles,
[T(p-X-P)Cor]Cu where X ) H, CH3, or OCH3.67 The
reduction potential of (Me4Ph5Cor)Cu is also anodically
shifted by 140 mV as compared to that of (OEC)Cu where
Electrochemistry of Mono- and Bis-copper Corroles.
The electrochemistry of the monomeric copper corrole,
(Me4Ph5Cor)Cu, and the corresponding face-to-face copper
biscorroles, (BCA)Cu2 and (BCB)Cu2 (see Chart 1), was
examined in CH2Cl2 containing 0.1 M TBAP. The cyclic
voltammograms for these compounds are illustrated in Figure
7 and the redox potentials are summarized in Table 4.
(67) Wasbotten, I. H.; Wondimagegn, T.; Ghosh, A. J. Am. Chem. Soc.
2002, 124, 8104-8116.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7451

Guilard et al.
E1/2 ) -0.34 V under the same solution conditions. This
shift in half-wave potential is consistent with a decreased
basicity of (Me4Ph5Cor)Cu as compared to (OEC)Cu and is
analogous to what is seen when comparing the more difficult
to reduce octaethylporphyrin (OEP) with tetraphenyl deriva-
tives (TPP) having the same central metal ion.4
The first reduction and first oxidation of (Me4Ph5Cor)Cu
both involve a reversible one-electron transfer, and no
evidence of dimerization is observed upon oxidation as is
the case for (OEC)Cu.30 In this regard, it should be pointed
out that the triphenylcorroles [T(p-X-P)Cor]Cu (X ) H,
CH3, or OCH3) also show no evidence of dimerization.67
From this result, it is clear that the substituents on the corrole
macrocycle must have a significant effect on the electrooxi-
dation mechanism.
The biscorroles and bisporphyrins that possess anthracene
(A) as a spacer group both show weaker π-π interactions
as compared to those of the same macrocycles with biphe-
nylene (B) as a spacer. Generally, these types of anthracene-
bridged compounds show either no splitting at all in the first
oxidation or a small degree of splitting, along with small
potential separations between E1/2 of the first two oxidations
(Table 4). For example, neither (BCA)Co2 nor (DPA)Co2
shows a splitting of the first oxidation. (DPA)H4 and
(DPA)Zn2 have a split first oxidation and a potential
separation of 70-120 mV, which is smaller than in the case
of (DPB)H4 or (DPB)Zn2 where the potential separation is
150-230 mV. The stronger interaction between two corrole
macrocycles or the two porphyrin macrocycles with biphe-
nylene (B) as a spacer is attributed to the shorter distance
between the two linking carbons in the biphenylene group
as compared to that in anthracene (A).
Because of the π-π interaction, both corrole macrocycles
in (BCA)Cu2 and (BCB)Cu2 are stepwise oxidized at
different potentials as compared with the corresponding
monomeric corrole, (Me4Ph5Cor)Cu. The monomer is oxi-
dized at 0.69 V (Figure 7b), and when the wave is split, one
process becomes easier and the other harder. This is shown
in Figure 7a for the case of (BCA)Cu2 and Figure 7c for the
case of (BCB)Cu2. Similar results have been reported for
other face-to-face biscorroles42 or bisporphyrins,68 and the
relevant electrochemical data are listed in Table 4.
The electroreduction of (BCA)Cu2 in CH2Cl2, 0.1 M TBAP
shows only one reversible reduction E1/2 ) -0.20 V, and
this leads to a formal Cu(II) species. The half-wave potential
for this reaction is identical to E1/2 for the reduction of the
monomeric compound, (Me4Ph5Cor)Cu (i.e., -0.20 V). In
contrast, (BCB)Cu2 undergoes two reversible reductions
(a split process) with E1/2 values located at -0.36 and
-0.51 V (Figure 7c). The peak current for each reduction
of (BCB)Cu2 is smaller than the peak current for the single
reduction of (BCA)Cu2 or (Me4Ph5Cor)Cu (Figure 7),
consistent with a splitting of the reduction into two processes.
The two reduction steps correspond to the stepwise addition
of one electron to each of the two copper centers of the
corrole unit. Both reductions of (BCB)Cu2 also occur at more
negative potentials than those for the reduction of monomeric
(Me4Ph5Cor)Cu, consistent with a strong π-π interaction
in (BCB)Cu2. Thus, as seen in Figure 7c, the half-wave
potential of -0.20 V for reduction of (Me4Ph5Cor)Cu shifts
to -0.36 and -0.51 V for the reduction of (BCB)Cu2. The
same trend is seen in Table 4 for the electroreduction of the
other face-to-face biscorroles or bisporphyrins that possess
an anthracene (A) or biphenylene (B) spacer.
Electrochemistry of Porphyrin-Corrole Dyads. Cyclic
voltammograms of the two porphyrin-corrole dyads,
(PCA)Cu2 and (PCB)Cu2, in CH2Cl2 containing 0.1 M
TBAP are illustrated in Figure 8, which includes for
comparison voltammograms for the two monomeric units,
(Me4Ph5Cor)Cu and (Me2Et6PhP)Cu. The electrochemistry
of (Me2Et6PhP)Cu is virtually identical to that of (OEP)Cu
under the same solution conditions. (Me2Et6PhP)Cu under-
goes one reversible reduction at E1/2 ) -1.49 V and two
The biscorrole complex, (BCA)Cu2, undergoes three
reversible oxidations in CH2Cl2 with E1/2 values located at
0.62, 0.75, and 1.17 V. The formation of [(BCA)Cu2]2+
where each macrocycle is singly oxidized is split into
two processes, and the potential separation between the
two E1/2 values is 130 mV. The peak currents of the first
two oxidations are also both lower than that of the third
oxidation or the first reduction, both of which involve the
global abstraction or addition of two electrons, and this is
thus comparable to what was reported for (OEC)Cu30 whose
first two oxidations occur via two stepwise one-electron
abstractions from each macrocycle in the electrogenerated
corrole π-π dimer. The potential separation between the
first two oxidations of (OEC)Cu is 140 mV, a value
comparable to the 130 mV separation observed in the case
of (BCA)Cu2. However in contrast to what is seen for (OEC)-
Cu, the monomeric corrole, (Me4Ph5Cor)Cu with phenyl
substituents does not dimerize during the first oxidation
(Figure 7b).
The electrooxidation of (BCB)Cu2 occurs in three steps,
the first two of which are reversible and the result of a split
oxidation for the formation of [(BCB)Cu2]2+ with E1/2 values
located at 0.45 and 0.85 V. The third oxidation is irreversible
with Epa ) 1.38 V for a scan rate of 0.1 V/s. As in the case
of (BCA)Cu2, the first two oxidations of (BCB)Cu2 can be
assigned to a stepwise abstraction of one electron from each
corrole macrocycle. The potential separation between the first
two oxidations of (BCB)Cu2 is 400 mV, a value much larger
than in the case of (BCA)Cu2 or (OEC)Cu where the
potential separations are 130 and 140 mV, respectively.
The smaller potential separation between the first two
oxidations of (BCA)Cu2 as compared to that of (BCB)Cu2
can be attributed to a smaller π-π interaction between
the two corrole macrocycles in the copper corroles with
anthracene spacers, and this is similar to what was observed
for the two related cobalt complexes, (BCA)Co2 and
(BCB)Co2,42 as well as other linked bisporphyrins68 that
also possess face-to-face macrocycles and the same two
linking spacer groups (anthracenyl or biphenylenyl). These
comparisons are summarized in Table 4.
(68) Le Mest, Y.; L’Her, M.; Collman, J. P.; Kim, K.; Hendricks, N. H.;
Helm, S. J. Electroanal. Chem. 1987, 234, 277-295.
7452 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
The half-wave potentials are located at 0.59, 0.77, 0.88, and
1.16 V for (PCA)Cu2, the latter of which involves two
overlapping one-electron-transfer processes (Figure 8a). The
oxidation potentials of (PCB)Cu2 are located at 0.50, 0.79,
0.90, 1.20, and 1.29 V. Five electrooxidations are also
observed when benzonitrile or tetrahydrofuran is used as the
solvent (data not shown).
Spectroelectrochemistry of Biscorrole Complexes and
Porphyrin-Corrole Dyads. Figure 9, parts a-c, gives a
spectral comparison between the neutral (-) and singly
reduced (- - -) forms of the different copper corroles.
(Me4Ph5Cor)Cu, (BCA)Cu2, and (BCB)Cu2 each exhibit
an intense Soret band at 404-410 nm and a broad, weak
visible band located at 569-570 nm (Table 5). Upon
reduction, the Soret band is red-shifted and located at 426
nm for (Me4Ph5Cor)Cu, 421 nm for (BCA)Cu2, and 423 nm
for (BCB)Cu2. In each case, an intense visible band close to
600 nm is observed for the electrogenerated Cu(II) product.
This type of visible band is not seen in any monomeric
Cu(II) porphyrin (e.g., (OEP)Cu or (Me2Et6PhPor)Cu (see
Table 5)) and can thus be considered as a “marker band”
for the electrogenerated Cu(II) corroles.
Further proof for the stepwise addition of one electron to
each copper center of (BCB)Cu2 is given by ESR spectra
taken during electroreduction of the compound in CH2Cl2,
0.2 M TBAP (Figure 10). The ESR spectrum of neutral
(BCB)Cu2 shows an extremely weak signal in agreement
with a bis-Cu(III) representation of the complex along with
a small contribution of a bis-Cu(II) radical species as
discussed above in the ESR section. However, upon con-
trolled potential reduction of (BCB)Cu2 at -0.45 V to
generate [(BCB)Cu2]-, a well-defined ESR spectrum is
obtained (g| ) 2.151; g ) 2.038) whose features are
characteristic of a copper(II) porphyrin-like species (Figure
10a). Further reduction at -0.70 V leads to the formation
of [(BCB)Cu2]2- with no change in the shape of the ESR
signal (g| ) 2.155; g ) 2.043) in accordance with the
formation of the bis-copper(II) species (Figure 10b). The
signal is not a triplet, indicating little or no interaction
between the two Cu(II) centers in the reduced complex.
The two neutral (PCA)Cu2 and (PCB)Cu2 complexes have
similar UV-vis spectral characteristics as seen in Figure 9,
parts d and e. (PCA)Cu2 has a strong Soret band at 407 nm
and two visible bands at 531 and 566 nm. (PCB)Cu2 has a
strong Soret band at 401 nm and two visible bands at 528
and 564 nm (Table 5 and Figures 9, parts d and e). These
spectral features can be compared to those of the monomeric
porphyrin, (Me2Et6PhPor)Cu, which has bands at 407, 530,
and 566 nm. A comparison may also be made to (OEP)Cu,
which has bands at 401, 526, and 562 nm. However, despite
a similarity in λmax for all of the above compounds, it must
be pointed out that the molar absorptivities (ꢀ) of the Soret
band in (PCA)Cu2 and (PCB)Cu2 are only about half
those of the monomeric porphyrins, (Me2Et6PhPor)Cu and
(OEP)Cu (Table 5). The ꢀ values of the Soret band in
Figure 8. Cyclic voltammograms of (a) (PCA)Cu2 (1.5 × 10-3 M), (b)
(PCB)Cu2 (1.3 × 10-3 M), (c) (Me4Ph5Cor)Cu (1.2 × 10-3 M), and (d)
(Me2Et6PhPor)Cu (1.2 × 10-3 M) in CH2Cl2 containing 0.1 M TBAP. Scan
rate ) 0.1 V/s.
reversible oxidations at E1/2 ) 0.77 and 1.16 V. (OEP)Cu
undergoes one reversible reduction at E1/2 ) -1.53 V and
two reversible oxidations at E1/2 ) 0.77 and 1.25 V. Each
redox process is assigned as occurring at the porphyrin π-ring
system leading to the formation of a π-anion radical
upon reduction and a π-cation radical and dication upon
oxidation.69
The porphyrin-corrole dyads, (PCA)Cu2 and (PCB)Cu2,
both undergo two well-defined reductions within the cathodic
potential limit of CH2Cl2. The reduction potentials are located
at E1/2 ) -0.19 and -1.52 V for (PCA)Cu2 and at E1/2
)
-0.35 and -1.52 V for (PCB)Cu2. The first electron addition
occurs at the copper center of the corrole ring, and the
second, at the π-ring system of the porphyrin. The latter E1/2
value is comparable to that for the monomeric porphyrin,
(Me2Et6PhP)Cu.
The half-wave potential for the first reduction of
(PCA)Cu2 (-0.19 V vs SCE) is almost the same as that of
the monomeric corrole unit, (Me4Ph5Cor)Cu, and the bis-
corrole, (BCA)Cu2, both of which are located at E1/2 ) -0.20
V. However, like (BCB)Cu2, the (PCB)Cu2 complex is also
harder to reduce than the monomeric unit, and the single
reduction shifts cathodically to E1/2 ) -0.35 V. Again, as
in the case of (BCB)Cu2, the negative shift of E1/2 may be
attributed to an increased π-π interaction between the two
macrocycles. This leads to a harder reduction in the case of
those compounds with B spacers (as opposed to A spacers)
42
and is demonstrated for (BCA)Co2 versus (BCB)Co2 and
70
(DPA)Co2 versus (DPB)Co2 (Table 4).
The electrochemical oxidation of the two porphyrin
complexes is characterized by four and five well-defined one-
electron processes for (PCA)Cu2 and (PCB)Cu2, respectively.
(69) Kadish, K. M. Prog. Inorg. Chem. 1986, 435-605.
(70) Le Mest, Y.; L’Her, M.; Hendricks, N. H.; Kim, K.; Collman, J. P.
Inorg. Chem. 1992, 31, 835-847.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7453

Guilard et al.
Table 5. UV-Visible Spectral Data of Cu Complexes in Nonaqueous Solvents with the Cu(II) Corrole ,Marker Band. Located in the Range
594-604 nm
solvent
macrocycle
compound
λ
max, nm (ꢀ × 10-4, M-1 cm-1
)
neutral species
singly reduced species at corrole center
CH2Cl2
PhCN
corrole
biscorrole
biscorrole
corrole
porphyrin
porphyrin
PCa
(Me4Ph5Cor)Cu
(BCA)Cu2
(BCB)Cu2
(Me4Ph5Cor)Cu
(Me2Et6PhP)Cu
(OEP)Cu
410 (10.1)
410 (13.0)
404 (11.8)
416 (8.9)
407 (38.4)
401 (34.5)
407 (19.0)
401 (18.6)
569 (1.7)
570 (2.5)
570 (2.1)
574 (1.5)
530 (1.5)
526 (1.3)
531 (1.9)
528 (1.7)
426 (12.6)
552 (1.7)
553 (2.6)
558 (4.3)
557 (1.5)
594 (6.0)
421 (15.4)
423 (12.2)
430 (11.6)
595 (6.0)
598 (7.7)
597 (5.5)
566 (2.2)
562 (2.9)
566 (2.3)
564 (2.0)
(PCA)Cu2
(PCB)Cu2
407 (19.2)
401 (18.4)
531 (1.9)
528 (1.7)
566 (2.3)
564 (2.0)
599 (2.2)
604 (1.5)
PCa
singly oxidized species
doubly oxidized species
CH2Cl2
corrole
biscorrole
biscorrole
(Me4Ph5Cor)Cu
(BCA)Cu2
(BCB)Cu2
410 (7.4)
410 (11.7)
404 (10.5)
532 (0.7)
550 (1.8)
569 (0.5)
570 (1.8)
573 (1.3)
416 (9.5)
398 (10.5)
570 (1.1)
880 (1.5)
a PC ) porphyrin-corrole.
Figure 9. Spectral comparison between neutral Cu(III) species (-) and
electrogenerated Cu(II) species (- - -) for (a) (Me4Ph5Cor)Cu, (b) (BCA)-
Cu2, and (c) (BCB)Cu2 in CH2Cl2, 0.2 M TBAP, and (d) (PCA)Cu2 and
(e) (PCB)Cu2 in PhCN, 0.2 M TBAP.
(Me2Et6PhPor)Cu and (OEP)Cu are 38.4 × 104 and 34.5 ×
104 M-1 cm-1, respectively, as compared to 19.0 × 104
M-1 cm-1 for (PCA)Cu2 and 18.6 × 104 M-1 cm-1 for
(PCB)Cu2. Thus, the spectral characteristics of the
corrole unit in (PCA)Cu2 and (PCB)Cu2 are not readily
observable because of the much stronger intensity of the
porphyrin bands that dominate the UV-vis spectrum of the
molecule (Table 5).
The spectral changes upon the first reduction of (PCA)-
Cu2 and (PCB)Cu2 in PhCN, 0.2 M TBAP are shown in
Figure 9, parts d and e. The Soret band of both com-
plexes undergoes no change upon the first reduction, but a
well-defined visible band around 600 nm appears for the
singly reduced species. As in the case of the monomer, this
band is characteristic of the formation of a Cu(II) corrole
product. This result clearly indicates that the first reduc-
tion of both (PCA)Cu2 and (PCB)Cu2 involves the copper
Figure 10. ESR spectra during the electroreduction of (BCB)Cu2 leading
to (a) [(BCB)Cu2]- and (b) [(BCB)Cu2]2- at 120 K in CH2Cl2, 0.2 M TBAP.
center of the corrole and not the porphyrin unit, and this
leads to the formation of a bis-Cu(II) complex (i.e.,
(Por)CuII-[(Cor)CuII]-).
UV-vis spectroelectrochemistry was also carried out for
oxidation of the three corroles in CH2Cl2, 0.2 M TBAP. The
corresponding spectral changes are illustrated in Figure 11,
7454 Inorganic Chemistry, Vol. 43, No. 23, 2004

Copper Biscorroles and Porphyrin-Corrole Dyads
tion of one electron from each corrole macrocycle, and this
leads to the formation of a π-cation radical and dication
(Figure 11b and Table 5). The spectral changes upon the
first oxidation of (BCB)Cu2 (Figure 11c) are characterized
by decreased intensity Soret and visible bands, similar to
what is seen for (Me4Ph5Cor)Cu and (BCA)Cu2. However,
the doubly oxidized corrole displays a blue shift in the Soret
band (with respect to the singly oxidized species), and the
wavelength changes from 404 to 398 nm along with the
appearance of a new broad visible band centered at 880
nm. A similar near-IR band was observed at 890 nm for
+
+ 30
[(OEC)Cu]2 and at 820 nm for [(OEC)Ni]2 . This band
is observed only in (BCB)Cu2 in the biscorrole series and
may be attributed to a strong π-π interaction existing in
the case of [(BCB)Cu2]2+. This result is consistent with
electrochemical results discussed in the previous section.
Conclusions
A comparative study of four cofacial copper bis-corrole
(BC) and porphyrin-corrole (PC) dyads and their related
monomeric corrole and porphyrin units shows that electronic
interaction between the two face-to-face macrocycles of these
cofacial derivatives depends critically on the type and size
of the rigid spacer. For the investigated bismacrocycles, the
copper corrole macrocycle in a face-to-face configuration
with another copper corrole or copper porphyrin can be
considered as a Cu(III) complex in equilibrium with a
Cu(II) radical, the copper(III) species being the main
oxidation state of the corrole at all temperatures as clearly
1
evidenced by H NMR studies. X-ray crystallographic data
suggests weak metal-metal interactions, and this is consis-
tent with the lack of any detectable effect on the ESR or
magnetic measurement data. However, the electrochemistry
of the dyads shows clearly that a strong π-π interaction
exists between the two macrocycles of (BCB)Cu2 as com-
pared to those of (BCA)Cu2, the dimer that has a larger
interplanar distance between the two macrocycles.
Acknowledgment. The support of the Robert A. Welch
Foundation (K.M.K., Grant E-680) and the French Ministry
of Research, CNRS (UMR 5633) is gratefully acknowledged.
The Re´gion Bourgogne and Air Liquide company are
acknowledged for scholarships (F.J.), and we are also grateful
to M. Soustelle for the synthesis of pyrrole and dipyr-
romethane precursors. N. Kiritsakas (Universite´ Louis Pas-
teur, Strasbourg, France) is acknowledged for the resolution
of the X-ray structure of (BCA)Cu2.
Figure 11. Spectral comparison of copper corroles between neutral spe-
cies and the singly or doubly oxidized species for (a) (Me4Ph5Cor)Cu, (b)
(BCA)Cu2, and (c) (BCB)Cu2 in CH2Cl2, 0.2 M TBAP.
and the data are collected in Table 5. Neutral (Me4Ph5Cor)-
Cu (-) has bands at 410 and 569 nm, and these both
decrease in intensity upon the first oxidation, suggesting the
abstraction of an electron from the π system of the corrole.30
The same result is seen in Figure 11b upon the first (- - -)
and second (‚‚‚) oxidations of (BCA)Cu2 where the Soret
and visible bands both decrease in intensity.
Supporting Information Available: Crystallographic data of
(BCB)Cu2, (BCA)Cu2, and (PCB)Cu2, ESR spectra (100 K and
room temperature) of (BCA)Cu2, (PCA)Cu2, (BCB)Cu2, and
(PCB)Cu2. This material is available free of charge via the internet
at http://pubs.acs.org.
As discussed in the electrochemistry section, the first and
second oxidations of (BCA)Cu2 involve a stepwise abstrac-
IC049651C
Inorganic Chemistry, Vol. 43, No. 23, 2004 7455