Synthetic, cyclic voltammetric, structural, EPR and UV-vis spectroscopic studies of thienyl-containing meso-A2B-cor(Crv=0) systems: Consideration of three interrelated molecular detection modalities

Article abstract of DOI:10.1021/ic9021432

We report eight new A₂B-type (Mⁿ⁺) corrolate compounds (two structural studies) that include the oxo[5,15- bis(pentafluorophenyl)-10-R-corrolatochromium(V)] [R = 2-/3-thienyl (1a/2a), 3-thianaphthyl (3a)] species. The first examples of meso-A₂ (thienyl)- and Cr-A₂B-corrole types are represented herein. Characterization includes cyclic voltammetry, electron paramagnetic resonance, 2D (¹H and ¹³C) NMR, and UV-vis spectroscopy, mass spectrometry, and elemental analysis. Compounds 1a-3a have enabled analyte binding capacity studies. [Cu²⁺...O=Cr(cor)] binding represents a new selective mode of corrole-based detection, whereas free-base A ₂B-corroles exhibited limited Mⁿ⁺ selectivity. The 10-position substitution affects optical profiles In analyte titrations. A limited amount of PPh₃ O-atom uptake from [O=Cr(cor)] was also demonstrated.

Full text of DOI:10.1021/ic9021432

502 Inorg. Chem. 2010, 49, 502–512
DOI: 10.1021/ic9021432
Synthetic, Cyclic Voltammetric, Structural, EPR, and UV-Vis Spectroscopic
Studies of Thienyl-Containing meso-A2B-cor(CrVdO) Systems: Consideration of
Three Interrelated Molecular Detection Modalities
Olga A. Egorova,†,‡ Olga G. Tsay,†,‡ Snehadrinarayan Khatua,†,‡ Bhupal Meka,†,‡,§ Nilkamal Maiti,†,‡,^
Min-Kyu Kim,z Seong Jung Kwon,‡ Jung Oh Huh,‡ Daniela Bucella, Sa-Ouk Kang,z Juhyoun Kwak,‡ and
David G. Churchill*,†,‡
†Molecular Logic Gate Laboratory, ‡Department of Chemistry, and School of Molecular Science (BK 21), Korea
Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu,
Daejeon 305-701, Republic of Korea, zSchool of Biological Sciences, Seoul National University, Seoul, Korea,
and Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027. § Former
BK-21 postdoctoral fellow in the laboratory of D. G. Churchill. Current address: Suven Life Sciences Ltd.,
Jeedimetla, Hyderabad 500055, India. ^ Former BK-21 postdoctoral fellow in the laboratory of D. G. Churchill.
Current address: Department of Chemistry, Midnapore College, Midnapore 721101, West Bengal, India.
Received July 30, 2009
We report eight new A2B-type (Mnþ) corrolate compounds (two structural studies) that include the oxo[5,15-
bis(pentafluorophenyl)-10-R-corrolatochromium(V)] [R = 2-/3-thienyl (1a/2a), 3-thianaphthyl (3a)] species. The first
examples of meso-A2 (thienyl)- and Cr-A2B-corrole types are represented herein. Characterization includes cyclic
voltammetry, electron paramagnetic resonance, 2D (1H and 13C) NMR, and UV-vis spectroscopy, mass spectro-
metry, and elemental analysis. Compounds 1a-3a have enabled analyte binding capacity studies.
[Cu2þ OdCr(cor)] binding represents a new selective mode of corrole-based detection, whereas free-base
3 3 3
A2B-corroles exhibited limited Mnþ selectivity. The 10-position substitution affects optical profiles in analyte titrations. A
limited amount of PPh3 O-atom uptake from [OdCr(cor)] was also demonstrated.
Introduction
axial site chemistry, there may be possibilities other than
those catalytic for such derivatives. In this paper, we have
synthesized new A2B-corroles1b and report novel CrdO
species. Importantly, we endeavor to expand the potential
of these contracted porphyrins as possible useful solution-
based polypyrrolic probes through considerations of the
interrelationships of the free base, the metal complex, and
the terminal oxo derivative.
We propose that the limited number of corrole-based
molecular detection systems reflected previously in the lit-
erature can now be grouped conveniently into interrelated
types as provided in Scheme 1: “Type I”, or cavity-centered
detection (metallations/protonations), includes chemical
Corrolate (cor) systems, especially A3-tris(pentafluoro-
phenyl)corrole-or (tpf)cor-basedones, are, by now, relatively
well-known ligands, with many reports relating to metal-
mediated catalysis.1a This foray has reaped various related
ligands and metal complex derivatives alike, as well as
subsequent metal-based axial ligands (e.g., MdO, Md
N-R), which, in corrole chemistry, possess properties and
reactivities that, unlike in the porphyrin literature, are still
being studied and established. The terminal oxo and closely
related derivatives are of great research interest as potential
motifs in “compound I” modeling with small molecules. It is
clear that while there continues to be vigorous interest in
further exploring the reactive biorelevant porphyrinoid-type
(2) He, C.-L.; Ren, F.-L.; Zhang, X.-B.; Han, Z.-X. Talanta 2006, 70,
364–369.
(3) Zhang, X.-B.; Han, Z.-X.; Fang, Z.-H.; Shen, G.-L.; Yu, R.-Q. Anal.
Chim. Acta 2006, 562, 210–215.
(4) (a) Li, C. Y.; Zhang, X. B.; Han, Z. X.; Akermark, B.; Sun, L. C.; Shen,
G. L.; Yu, R. Q. Analyst 2006, 131, 388–393. (b) For a resource for
collaborating with Chinese chemical colleagues, see: Chao, H.-Y.; Churchill,
D. G. J. Chem. Educ. 2008, 85, 1210.
(5) Radecki, J.; Dehaen, W. Comb. Chem. High Throughput Screening
2006, 9, 399–406.
*To whom correspondence should be addressed. E-mail: dchurchill@
kaist.ac.kr. Tel.: þ82-42-350-2845. Fax: þ82-42-350-2810.
(1) (a) Aviv, I.; Gross, Z. Chem. Commun. 2007, 1987. (b) Alemayehu,
A. B.; Gonzalez, E.; Hansen, L. K.; Ghosh, A. Inorg. Chem. 2009, 48, 7794–
7799. (c) Meier-Callahan, A. E.; Di Bilio, A. J.; Simkhovich, L.; Mahammed, A.;
Goldberg, I.; Gray, H. B.; Gross, Z. Inorg. Chem. 2001, 40, 6788–6793. (d) For an
excellent review of valence and related concepts, see:Parkin, G. J. Chem. Educ.
2006, 83, 791–799. (e) Czernuszewicz, R. S.; Mody, V.; Czader, A.; Galezowski,
M.; Gryko, D. T. J. Am. Chem. Soc. 2009, 131, 14214–14215.
r
pubs.acs.org/IC
Published on Web 12/17/2009
2009 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 503
Scheme 1. Modes of Analyte Detection Previously Reported and Presented Here, Shown Schematically for a Tri-Meso-Substituted Corrolate System
sensing of (metal) cations, such as Hg2þ,2 Agþ,3 and, of
course, Hþ.4-6 “Type II”, or Lewis base analyte binding
involves (i) volatile analytes7-12 such as CO,11,12 (ii) anions,
e.g., salicylate/salicylic acid,13 and (iii) neutral binding mole-
cules such as (nitro)phenolic species,5 pyridine,11,12 and
organophosphonates.14 The meso-C6H5,2,3 A3,9,10 and A2B
types,8-10,4,13 β-substituted7,10-12 and (2,17-di)-sulfonated
versions,6 have been represented to date. The spectroscopic
sensing mode in these reports is, e.g., fluorescence,2,6 UV-vis
absorption,11,12,14 and IR.10 Potentiometry13,5 has also been
featured, along with electrochemical speciation,13-15 having
been pursued elegantly by, e.g., Kadish and co-workers.11,12
More intricate corrole-based designs such as bis-corroles and
linked porphyrin/corrole systems highlight that there is still
much latitude in continued exploits in molecular sensing with
corroles.11 “Type III”, or oxo-ligand-mediated binding inter-
actions, can first be considered seriously herein because of
their growing prevalence and simplicity (i.e., the MdO
group). These derivatives are often prepared for/from O-
atom transfer. In this potential sensing platform, which
would be akin to “Fe-O-Fe”-type dimers,16 it would be
important to avoid derailment of metal ion sensing by, e.g.,
PR3 and SR2 atoms or via olefin oxidation.17 In real sensing
matrixes, the rigorous absence of these substrates may be
difficult, however, but a less reactive oxide could be prepared
from peripheral porphyrinoid modifications that would in-
volve tuning via the incorporation of various meso groups
(vide infra).
In this report, we detail the synthesis and characterization of
eight new A2B-type (Mnþ) corrolate compounds that include
oxo[5,15-bis(pentafluorophenyl)-10-R-corrolatochromium(V)]
[R = 2-/3-thienyl (1a/2a), 3-thianaphthyl (3a)]. These deriva-
tives represent the first examples of meso-A2 (thienyl)- and Cr-
A2B-corrole types. The formal replacement of one -C6F5
group with one thienyl substitution18,19 was expected to change
the extreme electron-withdrawing nature known for the tris-
C6F5-A3-type tpf(cor) species. This thienyl substitution also
allows for an adjacent ligand-based oxidation site at the sulfur.
Chromium was selected for incorporation because of its redox
utility. The first synthesis, full characterization, and detailed
research on a chromium A3-triarylcorrolate were performed by
Meier-Callahan and co-workers.20 Our research laboratory has
also recently reported a thienyl-containing ABC-type CrdO
derivative.18e The structures of compounds have been charac-
terized by a number of physical methods including UV-vis, 2D
(1H and 13C) NMR, electron paramagnetic resonance (EPR)
spectroscopy, mass spectrometry, elemental analysis, and cyclic
voltammetry (CV). Also, two single-crystal X-ray crystallo-
graphic studies were performed, in addition to obtaining a
measure of the catalytic reactivity of the new corroles. Interest-
ingly, complexes 1a-3a represent type III corrole-based detec-
tion platforms for the copper(II) ion.
(6) Mahammed, A.; Weaver, J. J.; Gray, H. B.; Abdelas, M.; Gross, Z.
Tetrahedron Lett. 2003, 44, 2077–2079.
(7) Di Natale, C.; Goletti, C.; Paolesse, R.; Drago, M.; Macagnano, A.;
Mantini, A.; Troitsky, V. I.; Berzina, T. S.; Cocco, M.; D’Amico, A. Sens.
Actuators, B 1999, B57, 183.
ꢀ
(8) Barbe, J.-M.; Canard, G.; Brandes, S.; Guilard, R. Angew. Chem., Int.
Ed. 2005, 44, 3103–3106.
(9) Barbe, J. M.; Canard, G.; Brandes, S.; Guilard, R. Eur. J. Org. Chem.
2005, 4601–4611.
Experimental Section
ꢁ
ꢁ ^
(10) Barbe, J.-M.; Canard, G.; Brandes, S.; Jerome, F.; Dubois, G.;
Materials and Physical Measurements. All chemicals (e.g., 2-/
3-thiophene carboxaldehyde, benzo[b]thiophene-3-carboxalde-
hyde, copper(II) acetate monohydrate, chromium hexacarbonyl,
Guilard, R. Dalton Trans. 2004, 1208–1214.
(11) Kadish, K. M.; Ou, Z. P.; Shao, J. G.; Gros, C. P.; Barbe, J. M.;
Jerome, F.; Bolze, F.; Burdet, F.; Guilard, R. Inorg. Chem. 2002, 41, 3990–
4005.
(12) Guilard, R.; Gros, C. P.; Bolze, F.; Jerome, F.; Ou, Z. P.; Shao, J. G.;
Fischer, J.; Weiss, R.; Kadish, K. M. Inorg. Chem. 2001, 40, 4845–4855.
(13) Radecki, J.; Wona, S. T. A.; Eddy, D. B.; Dehaen, W. Electrochim.
Acta 2006, 51, 2282–2288.
(14) Kim, K.; Kim, I.; Maiti, N.; Kwon, S. J.; Bucella, D.; Egorova, O. A.;
Lee, Y. S.; Kwak, J.; Churchill, D. G. Polyhedron 2009, 28, 2418–2430.
(15) Radecki, J.; Stenka, I.; Dolusic, E.; Dehaen, W.; Plavec, J. Comb.
Chem. High Throughput Screening 2004, 7, 375–381.
(18) (a) Maiti, N.; Lee, J.; Do, Y.; Shin, H. S.; Churchill, D. G. J. Chem.
Crystallogr. 2005, 35, 949–955. (b) Maiti, N.; Lee, J. S.; Kwon, S. J.; Kwak, J.;
Do, Y.; Churchill, D. G. Polyhedron 2006, 25, 1519–1530. (c) Churchill, D. G.;
Maiti, N.; Choi, S. H. Repub. Korean Kongkae Taeho Kongbo KR 2007049466,
2007. (d) Maiti, N.; Kim, K.; Meka, B.; Churchill, D. G. Unpublished results,
2005-2007. (e) Egorova, O. A.; Tsay, O. G.; Khatua, S.; Huh, J. O.; Churchill,
D. G. Inorg. Chem. 2009, 48, 4634–4636.
(16) Harischandra, D. N.; Lowery, G.; Zhang, R.; Newcomb, M. Org.
Lett. 2009, 11, 2089–2092.
(17) Liu, H.-Y.; Yam, F.; Xie, Y.-T.; Li, X.-Y.; Chang, C. K. J. Am.
Chem. Soc. 2009, 131, 12890–12891.
(19) Choi, S. H.; Pang, K.; Kim, K.; Jeon, J.; Meka, B.; Bucella, D.; Pang,
K.; Khatua, S.; Lee, J.; Churchill, D. G. Inorg. Chem. 2008, 47, 11071–11083.
(20) Meier-Callahan, A. E.; Gray, H. B.; Gross, Z. Inorg. Chem. 2000, 39,
3605–3607.

504 Inorganic Chemistry, Vol. 49, No. 2, 2010
Egorova et al.
CH2Cl2, chloroform, hexane, toluene, and Mnþ perchlorates)
used herein were of analytical grade and were used as received
from commercial suppliers (Aldrich, TCI and Junsei chemical
companies) except for pyrrole. Pyrrole was distilled over CaH2
under vacuum prior to use. Plates for thin-layer chromatogra-
phy (TLC) were cut from the original plates (20 ꢀ 20 cm, 60 F
silica gel, Merck Co.). A Vilber Lourmat-4LC UV lamp (4 W,
365 nm, 50/60 Hz) was used to probe the fluorescence of reaction
“spots” assayed by TLC. The silica gel used in column chroma-
tography was of diameter 0.04-0.063 mm. The silica gel used for
dry-column vacuum chromatography was of diameter
0.015-0.040 mm (Merck). All solvents used in NMR spectral
analyses were purchased commercially and were of spectrosco-
py grade. 1D 1H and 13C NMR spectra and 2D COSY, NOESY,
HMBC, and HMQC NMR spectra were measured on a Bruker
Avance 400 MHz spectrometer with tetramethylsilane used as
the internal standard. Elemental analyses of samples were
obtained by using a Vario EL III elemental analyzer. UV spectra
were recorded with a Jasco V-503 UV-vis spectrometer (1000
nm/min). Emission spectra were obtained using a Shimadzu
RF-5310 pc spectrofluorophotometer. EPR spectra were
obtained on a Bruker EMX ER 082 spectrometer. High-resolu-
tion MALDI-TOF mass spectrometry was performed on an
Applied Biosystem Voyager 4394 (ionization method, N2 laser
(337 nm, 3 ns pulse): analyzer 2.0 m linear mode; 3.0 reflector
mode.) CV was carried out with a BAS 100B instrument
(Bioanalytical Systems, Inc.) under ambient conditions. A
three-electrode system was used and consisted of a gold disk
working electrode, a platinum wire counter electrode, and an
Ag/Agþ electrode (MF-2026 kit, Bioanalytical Systems, Inc.) as
the reference electrode. The Ag/Agþ electrode contained 0.1 M
tetrabutylammonium perchlorate (TBAP) and 0.01 M AgNO3
in acetonitrile. In 0.1 M TBAP, E1/2 of the ferrocene/ferroce-
nium ion couple was taken to be 0.13 V vs Ag/Agþ in acetoni-
trile. The values in electrochemical experiments are reported
versus the ferrocene/ferrocenium ion redox couple.
MALDI-TOF (M þ Hþ): m/z 712.56 (calcd), 713.36 (obsd). Anal.
Calcd for C35H14N4SF10: C, 58.99; H, 1.98; N, 7.86; S, 4.50. Found:
C, 58.90; H, 1.98; N, 7.72; S, 4.45. λabs (CH2Cl2, log ε = 5.2) = 415
nm. ΦF = 0.003.23
Synthesis of 5,15-Bis(pentafluorophenyl)-10-(3-thienyl)corrole,
[3THC] (2). The reaction mixture was filtered through a silica
pad (CH2Cl2). After solvent evaporation, subsequent dry-column
vacuum chromatography (silica, CH2Cl2/hexane, 1:1) gave a pink-
violet band, which contains corrole as well as traces of porphyrin.
Recrystallization from n-hexane/CHCl3 afforded pure corrole
1
(40 mg, ca. 4.5%) as a purple solid. H NMR (CD2Cl2): δ 7.77
(dd, 3JH-H = 4.85 and 3.02 Hz, Hc), 7.98 (dd, 3JH-H = 4.81 Hz,
4JH-H = 0.83 Hz, Hb), 8.05 (dd, 3JH-H = 2.72 Hz, 4JH-H = 0.95
=
Hz, Hd), 8.60 (d, 3JH-H = 4.18 Hz, H3 and H17), 8.76 (d, 3JH-H
3
4.76 Hz, H7 and H13), 8.86 (d, JH-H = 4.75 Hz, H8 and H12),
3
9.14 (d, JH-H = 4.27 Hz, H2 and H18). 13C NMR (CD2Cl2):
δ 147.8 (s), 145.3 (s), 143.4 (br), 141.9 (s, Ca or 10), 140.3 (br), 139.6
(m), 137.1 (m), 135.8 (br), 134.4 (s, Cb), 132.0 (br), 128.6 (s, Cd),
127.9 (s, C8 and C 12), 125.8 (s, C7 and C13), 124.6 (s, Cc), 122.2 (br),
118.0 (s, C2 and C18), 114.4 (t), 108.0 (s), 96.9 (br). MALDI-TOF
(M þ Hþ): m/z 712.56 (calcd), 713.37 (obsd). Anal. Calcd for
C35H14N4SF10: C, 58.99; H, 1.98; N, 7.86; S, 4.50. Found: C, 59.80;
H, 2.10; N, 7.92; S, 4.53. λabs (CH2Cl2, log ε = 5.1) = 416 nm.
ΦF = 0.004 (this is time-dependent: vide infra).
Synthesis of 5,15-Bis(pentafluorophenyl)-10-(3-thianaphthyl)-
corrole, [TNPC] (3). The reaction mixture was filtered through
a pad of silica gel (CH2Cl2). After solvent evaporation, corrole
purification was carried out by using dry-column vacuum chro-
matography (CH2Cl2/hexane, 0.7:1.0), and a green-violet band
exhibiting red fluorescence was collected. Subsequent recrystalli-
zation from hexane/CH2Cl2 afforded a pure purple solid com-
pound (3). Yield: 76 mg, ca. 7%. 1H NMR (CDCl3): δ 7.51
(m, He and Hf), 8.02 (m, Hd and Hg), 8.30 (s, Hb), 8.53 (d, 3JH-H
=
2.18 Hz, H3 and H17), 8.71 (d, 3JH-H = 4.47 Hz, H7 and H13),
8.98(d, 3JH-H = 4.68 Hz, H8 and H12), 9.03 (d, 3JH-H = 4.02 Hz,
H2 and H18). 13C NMR (CDCl3): δ 147.35 (br, s), 144.9 (m),
143.1 (br, CPFP), 142.9 (s, Ca or 10), 142.0 (s, C10), 140.6 (m, CPFP),
139.6 (s), 139.3 (tr, CPFP), 136.64 (m, CPFP), 134.8 (br, CPFP),
131.0 (br, CPFP), 130.0 (s, 1Cb), 127.8 (s, 2C8,12), 126.1 (s, 2C7,13),
124.8 (d, 3JC-F = 14.5 Hz, Ce and Cf), 124.0 (s, Cg or d), 121.8 (s,
General Procedure for the Preparation of Free-Base meso-
A2B-trans-corroles Starting from 5-(Pentafluorophenyl)dipyrro-
methane. The details for the synthesis of 5-(pentafluorophenyl)
dipyrromethane have been reported previously.21 Sample of
5-(pentafluorophenyl)dipyrromethane22a (1.00 g, 3.20 mmol)
and aldehyde (1.60 mmol) were dissolved in a mixed solution
of trifluoroacetic acid (1.3 mM)/CH2Cl2 (100 mL). The reaction
mixture was stirred under nitrogen and left at room tempera-
ture. After ∼5 h, a portion of dichlorodicyanoquinone (DDQ;
0.726 g, 3.20 mmol) was added dropwise as a toluene (10 mL)
solution; the reaction mixture was stirred at room temperature
for a further 15 min. Then, the reaction mixture was purified as
described below.
C
C
g or d), 121.6 (br, C3 and C17), 117.34 (s, 2C2 and C18), 113.84 (m,
PFP), 104.4(s, 1Ca). MALDI-TOF (M þ Hþ): m/z 762.62
(calcd), 763.17 (obsd). Anal. Calcd for C35H14N4SF10: C, 58.99;
H, 1.98;N, 7.86;S, 4.50. Found:C, 59.80;H, 2.10;N, 7.92;S, 4.53.
λabs (CH2Cl2, log ε = 5.04) = 421 nm. ΦF = 0.004.
General Procedure for the Preparation of Oxocorrolatochromium-
(V) Species. A detailed synthesis of oxocorrolatochromium species
was adapted from a report in the literature.20 Chromium hexacar-
bonyl (excess) was added to 20 mL of a boiling toluene solution of a
free-base corrole (∼45 mg). The reaction mixture was stirred for 2 h,
during which time the solution changed from green (reactant) to
reddish-brown (product). Product formation was also monitored by
TLC assay. After cooling to room temperature, the crude mixture
was filtered using a water aspirator to remove an excess of chromium
hexacarbonyl crystals. The remaining toluene was removed by
rotary evaporation. The dry crude product was then dissolved in a
minimum volume of dichloromethane and purified by silica gel
column chromatography (CH2Cl2/hexane). The blood-red fraction
containing the oxochromium(V) species was collected. Subsequent
recrystallization afforded a pure compound. Detailed crystallization
systems for individual compounds are given below.
Synthesis of 5,15-Bis(pentafluorophenyl)-10-(2-thienyl)corrole,
[2THC] (1). The reaction mixture was filtered through a silica
pad (CH2Cl2) and evaporated. Subsequent dry-column vacuum
chromatography (silica, CH2Cl2/hexane, 0.7:1.0) afforded pure
corrole (113 mg, ca. 10%), which was recrystallized (hexane/
1
CH2Cl2, 1:1 by volume) to give dark-purple crystals. H NMR
3
(CD2Cl2): δ 7.52 (dd, JH-H = 5.2 and 3.4 Hz, 1Hc), 7.87 (dd,
3JH-H = 5.36 Hz, 4JH-H = 1.04 Hz, Hd), 7.90 (dd, 3JH-H = 3.46
Hz, 4JH-H = 1.08 Hz, Hb), 8.59 (d, 3JH-H = 3.85 Hz, H3 and H17),
8.75 (d, 3JH-H = 4.68 Hz, H7 and H13), 8.91 (d, 3JH-H = 4.77 Hz,
H8 and H12), 9.14 (d, 3JH-H = 4.27 Hz, H2 and H18). 13C NMR
(CD2Cl2): δ 147.8 (s), 145.3 (s), 142.9 (s, 1Ca or 10), 140.9 (br),
139.5 (m), 137.2 (br), 133.5 (s, 1Cb), 131.5 (br), 128.4 (s, 1Cd), 128.0
(s, C8 and C12), 127.0 (s, Cc), 126.1 (s, C7 and C13), 121.6 (br, C3 and
C17), 117.9 (s, C2 and C18), 114.3 (tr), 104.9 (s, C9 and C11).
Synthesis of Oxo[5,15-bis(pentafluorophenyl)-10-(2-thienyl)-
corrolato]chromium(V), [2THC CrVO] (1a). Recrystallization
of complex 1a from CH2Cl2/hexane afforded a pure com-
pound. Yield: ∼70%. MALDI-TOF (Mþ): m/z 777.53
(calcd), 777.24 (obsd). λabs (CH2Cl2, log ε = 4.87) = 402 nm.
(21) Laha, J. K.; Dhanalekshmi, S.; Taniguchi, M.; Ambroise, A.;
Lindsey, J. S. J. Org. Process Res. Dev. 2003, 7(6), 799–812.
(22) (a) Simkhovich, L.; Galili, N.; Saltsman, I.; Goldberg, I.; Gross, Z.
Inorg. Chem. 2000, 39, 2704–2705. (b) Gryko, D. T.; Koszarna, B. Org. Biomol.
Chem. 2003, 1, 350–357.
(23) Quantum yields were calculated using fluorescein as a reference.

Article
Synthesis of Oxo[5,15-bis(pentafluorophenyl)-10-(3-thienyl)-
Inorganic Chemistry, Vol. 49, No. 2, 2010 505
Table 1. Crystal Data for Compounds 1 and 2b
corrolato]chromium(V), [3THC CrVO] (2a). Dark-red crystals
of complex 2a were obtained by recrystallization from CH2Cl2/
hexane. Yield: ∼70%. MALDI-TOF (Mþ): m/z 777.53 (calcd),
777.18 (obsd). λabs (CH2Cl2, log ε = 4.86) = 403 nm.
Synthesis of Oxo[5,15-bis(pentafluorophenyl)-10-(3-thianaphthyl)-
corrolato]chromium(V), [TNPC CrVO] (3a). A dark-red solid ma-
terial signifying complex 3a was obtained by recrystallization from
CH2Cl2/hexane. Yield: 98%. MALDI-TOF (Mþ): m/z 827.62
(calcd), 827.21 (obsd). λabs (CH2Cl2, log ε = 4.80) = 404 nm.
Synthesis of Oxo[5,10,15-tris(pentafluorophenyl)corrolato]-
chromium(V) (4a). This compound has been previously prepared
in the literature20 and was resynthesized for comparison in these
studies.
1
2b
empirical formula
fw
temperature (K),
C35 H14 F10 N4 S
712.56
243(2), 0.710 73
C35 H11 Cu F10 N4 S
773.08
293(2), 0.710 73
˚
wavelength (A)
cryst syst, space
group
unit cell dimens
monoclinic, P21/n
monoclinic, P21/n
˚
a (A)
14.4873(18)
7.7533(8)
25.313(3)
95.370(2)
2830.8(6)
4
14.9807(11)
10.7772(7)
18.7525(13)
100.179(5)
2979.9(4)
4
˚
b (A)
˚
c (A)
β (deg)
3
Vol (A )
˚
Synthesis of Oxo(5,10,15-tri-3-thienylcorrolato)chromium(V)
(5a). Dark-violet crystals of complex 5a were obtained by
recrystallization from CH2Cl2/hexane. Yield: 37 mg, ∼70%.
MALDI-TOF (Mþ): m/z 609.12 (calcd), 609.71 (obsd). λabs
(CH2Cl2, log ε = 4.64) = 407 nm.
Synthesis of 5,15-Bis(pentafluorophenyl)-10-(3-thienyl)corrolato-
copper(III), [3THC Cu] (2b). Copper(II) acetate monohydrate
(excess) was added to a 10 mL volume of a pyridine solution of
[3THC] (2; 40 mg, 0.056 mmol). The reaction mixture was stirred
for ∼2 h at room temperature. The crude reaction mixture was
filtered directly through a pad of silica gel (CH2Cl2).Thefirstbrown
fraction was collected and purified through the use of flash column
chromatography (silica; CH2Cl2/hexane, 1:1). Solvent evaporation
afforded a violet-red solid of 2b. Yield: 30.5 mg, ∼70%. MALDI-
TOF (M þ Hþ): m/z 773.9 (calcd), 774.9 (obsd). λabs (CH2Cl2, log
ε = 4.94) = 402 nm.
Z
density
1.672
1.723
(calcd, Mg/m3)
abs coeff (mm-1
F(000)
)
0.217
1432
0.901
1536
cryst size (mm3)
0.15 ꢀ 0.15 ꢀ 0.02
0.20 ꢀ 0.10 ꢀ
0.10
1.61-20.49
θ range for data
collection
reflns colld
indep reflns
1.34-19.34
14 505
13 394
6390 [R(int) = 0.0846]
6390 [R(int) =
0.0846]
empirical
abs corrn
max and min
transmn
empirical
0.8403 and 0.9153
0.9957 and 0.9682
data/restraints/
param
6390/0/448
6390/0/448
GOF on F2
final R indices
[I > 2σ(I)]
R indices
0.979
1.071
Crystallographic Studies. X-ray diffraction measurements
were performed at 293 K with a Bruker SMART 1K CCD
diffractometer using graphite-monochromated Mo KR radia-
R1 = 0.0736,
wR2 = 0.1068
R1 = 0.2125,
wR2 = 0.2275
R1 = 0.0502,
wR2 = 0.0970
R1 = 0.1236,
wR2 = 0.1622
˚
(all data)a
tion (λ = 0.710 73 A). Cell parameters were determined and
refined by the SMART program.24 Data reduction was per-
formed through the use of SAINT software.24 The data were
corrected for Lorentz and polarization effects. An empirical
absorption correction was applied using the SADABS pro-
gram.25 All intensity data were corrected for Lorentz and
polarization effects. The structures were solved by direct meth-
ods using the program SHELXS-974 and refined by full-matrix
least-squares calculations (F2) by using SHELXL-97 software.26
All non-H atoms were refined anisotropically against F2 for all
reflections. All H atoms were placed at their calculated positions
and refined isotropically. Crystal data for compounds 1 and 2b
are given in Table 1. Selected bond lengths and angles for 2b are
listed in Table 2. The CIF files were deposited with the Cam-
bridge Crystallographic Data Centre, and the following codes
were allocated: CCDC 684998 (1) and 720659 (2b). These data
can be obtained free of charge via the Internet at www.ccdc.cam.
ac.uk/data_request/cif.
P
P
P
P
a R1 = (
Fo| - |Fc )/ |Fo|; wR2 = [( (Fo2 - Fc2)2)/ w(Fo2)2]1/2
.
˚
Table 2. Comparative Selected Bond Lengths [A] and Angles [deg] for Copper-
(III) Corrolate Complexes
3THC(cor)CuIII (2b)
tris(2TH)(cor)CuIIIa
Bond Lengths
N(1)-Cu(1)
N(2)-Cu(1)
N(3)-Cu(1)
N(4)-Cu(1)
1.888(6)
1.894(6)
1.907(6)
1.873(6)
1.888(5)
1.891(4)
1.886(2)
1.889(4)
Bond Angles
N(4)-Cu(1)-N(2)
N(1)-Cu(1)-N(3)
166.9(3)
169.1(3)
168.28(16)
168.40(16)
a Reference 18b. b The plane of the macrocycle is defined by the four
pyrrolic N atoms.
Results and Discussion
Synthesis. The corrolate synthesis was initiated by the
preparation of dipyrromethane via InCl3-catalyzed con-
densation conditions.21 Then, a one-pot acid-catalyzed
condensation, followed by DDQ oxidation, afforded the
meso-A2B free-base corrole22b through which the 5-/15-
meso-aryl groups are derived from those of aryldipyrro-
methane. The [CrdO] moiety was formally incorporated
into the corrole throughaerobic metallation of Cr(CO)6 to
give the respective chromium(V) species 1a-5a (Scheme 2).
Corrole resistance to oxidation occurs via such meta-
llation. The Cu3þ complex 2b and A3-type compounds 4 and
4a21,22a were also prepared to facilitate data compar-
ison.
X-ray Crystallography. We have undertaken single-
crystal X-ray diffraction studies of the free-base corrole
1 and the copper(III) corrolate species 2b (Table 1 and the
Supporting Information). Suitable single crystals for the
X-ray diffraction study of 1 were obtained from a
CH2Cl2/hexane (1:2) solvent mixture. The compound
crystallized in the monoclinic space group P21/n. The
structure of 1 (Figure 1a) confirms the existence of the
(24) SMART and SAINT, Area Detector Software Package and SAX Area
Detector Integration Program; Bruker Analytical X-ray: Madison, WI, 1997.
(25) SADABS, Area Detector Absorption Correction Program; Bruker
Analytical X-ray: Madison, WI, 1997.
(26) Sheldrick, G. M. SHELXL-97; Universitat Gottingen: Gottingen,
Germany, 1999.
€
€
€

506 Inorganic Chemistry, Vol. 49, No. 2, 2010
Egorova et al.
Scheme 2. Synthesis of A2B-metallocorroles from Commercially Available Starting Materials
expected three meso-aryl groups and four constituent
pyrrolyl groups, which are non-coplanar with the mean
macrocyclic plane: one is bent downward, while another
is bent upward. The meso-aryl groups are located toward
the corrole core with dihedral values of ∼121ꢀ. For the
thienyl group, there is a ∼124ꢀ dihedral angle value,
signifying a slightly greater rotational flexibility for this
moiety.18b
with previously published data for, e.g., 5,10,15-tri-2-
thienylcorrolatocopper(III) (Table 2). The structure of
2b, in comparison with the oxochromium(V) species, does
not possess out-of-[N4]-plane metal atom displacement
(vide infra).20 Macrocyclic puckering is evident generally
for the corroles, especially in the structure for 1, in which
the pyrrolyl ring mean planes are clearly non-coplanar
with the corrole [N4] mean plane.
X-ray-diffraction-quality single crystals of 2b were
obtained via the slow evaporation of a CH2Cl2/hexane
(1:1) mixture under ambient conditions. The molecular
structure is consistent with the expected major synthetic
product. The copper center adopts a distorted square-
pyramidal environment in which four corrole N atoms
occupy the equatorial position and the metal occupies
the axial position (Figure 1b). The Cu-N bond lengths
While there are many literature examples available for
comparison of the copper-containing structure of 2b
(refer to the Cambridge Structural Database), a very
recent and intriguing report by Ghosh et al. focuses on
the phenomenon of copper corrolate saddling.1b In this
paper, it is asserted that “copper corroles are inherently
nonplanar, even in the absence of sterically hindered
substituents” because of Cu d-cor π orbital interactions.
Indeed, there is a semblance of saddeling for derivative
˚
of 2b are in the range of 1.873-1.907 A, comparable

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 507
Figure 1. Crystal structures of compounds 1 (a) and 2b (b).
Figure 2. (a) EPR spectrum of 2a in CH2Cl2 at 298 K. (b) EPR spectrum of 2b upon the addition of 4 equiv of NaBH4 in CH2Cl2 at 298 K. The microwave
frequency, power, and modulation amplitude were 9.768 MHz, 5.0 mW, and 1.00 G, respectively.
2b, which can be appreciated when looking along the
approximate trans-[N-Cu-N] vector, whereupon the
distal ends of the pyrrolyl are clearly seen to bow to the
same side away from the copper center. A greater version
of analysis considering all pyrrolyl mean planes for all
structurally known copper corrole species would be in
order at a later time, to more comprehensively analyze the
extent of saddling per peripheral substitution.
Table 3. EPR Parameters for the Series of Oxochromium(V) Corrole Complexes
complex
giso
A
53Cr/mT
A
14N/mT
ref
1a
2a
3a
5a
1.986
1.985
1.988
1.988
1.989
1.986
1.61
1.62
1.61
1.55
1.59
1.64
2.67
2.18
2.18
0.30
0.30
0.30
0.30
0.30
0.30
0.27
0.31
0.31
this work
this work
this work
this work
18e
[ABC](cor)CrVO
tris(pfp)(cor)CrVO
tris(pfp)(cor)CrVN
tris(pfp)(cor)CrV(NAr)
20
27a
27b
27b
Unfortunately, suitable single crystals of the oxo-
chromium(V) species 1a-4a were not obtained. How-
ever, the X-ray diffraction study of meso-ABC-oxo-
chromium(V) corrolate species has recently been publish-
ed,18e demonstrating a relatively larger displacement
1.987
tris(pfp)(cor)CrV(NMes) 1.985
abundance; Figure 2 and the Supporting Information). The
isotropic hyperfine coupling constants of 1a-3a and 5a were
obtained via computer simulation; these values are summar-
ized in Table 3 and are presently compared with data of
known literature compounds. The data of these new com-
pounds fall within the range of those found for other corrole
chromium(V) species, e.g., oxo[5-(4-bromophenyl)-10-(penta-
fluorophenyl)-15-(2-thianaphthyl)corrolato]chromium(V).18e
The hyperfine coupling constants of oxochromium(V)
species reflected a relative spin density of metal (low) and
ligand (high), which have previously been rationalized via
a strong N f M σ donation, followed by transfer of that
density to the axial ligand by way of π donation.20 In the
˚
(0.58 A) of the Cr atom from the center of the tetrapyrro-
lyl macrocycle and exhibiting shorter Cr-N bond dis-
tances in line with strong σ donation from the N atoms of
the corrole ring to the central metal atom (Table 2). This is
in accordance with an enhanced benchtop stability found
for the oxochromium(V) complexes.
EPR Study. The room temperature EPR spectra of
oxochromium(V) species 1a-3a and 5a in dichloromethane
display a sharp isotopic signal at g0 around 1.98, confirming a
1
3dxy ground-state electronic configuration for the oxo-
chromium(V) complex. This signal is split into nine lines
attributable to the coupling of the unpaired electron with four
equivalent 14N nuclei whose nuclear spin is 1 (I = 1); there
are also satellite signals due to primary coupling with the less
abundant 53Cr nucleus, which possesses a spin of 3/2 (9.5%
(27) (a) Golubkov, G.; Gross, Z. Angew. Chem., Int. Ed. 2003, 42, 4507–
4510. (b) Edwards, N. Y.; Eikey, R. A.; Loring, M. I.; Abu-Omar, M. M. Inorg.
Chem. 2005, 44, 3700–3708.

508 Inorganic Chemistry, Vol. 49, No. 2, 2010
Egorova et al.
Figure 3. (a) Cyclic voltammograms of 1-3 in acetonitrile (1 mM) with 0.1 M TBAP. (b) Cyclic voltammograms of 1a, 2a, 2b, 3a, and 4a in acetonitrile
(1 mM), with 0.1 M TBAP at a scan rate of 100 mV/s (only second scans are provided). E1/2 (V) values are provided for each species.
case of closely related nitrido27a and imido27b complexes,
a similar situation exists, but in these cases, the strong
π-donating ability of the axial ligand somewhat negates
the σ-donating effect of pyrrolic N atoms; the relative spin
density is thus much higher on the metal.
Information). In the case of metal complexes, there are
two one-electron reversible redox processes: a ligand-
based oxidation corresponding to the corrole/corrole
π-radical cation (ligand/ligand•þ) couple and a metal-
based reduction corresponding to the metaln/metaln-1
couple.
14N
The A
coupling constant, reflecting the order of
σ donation of the pyrrolic N atoms to the metal is greatest
for the oxo species; this leads to the observed short
metal-nitrogen pyrrole distances. These facts, together
with the presence of a larger metal atom displacement
from the plane of corrole macrocycle observed for CrVO
and CrVN complexes (Table 3) when compared to non-
axially ligated systems, are the main factors for stabiliza-
tion of these complexes. Table 3 shows that the value of
(53Cr) decreases upon going from the strong tris-
(C6F5)corrole electron-withdrawing ligand to 1a-3a
and finally to the tri-3-thienylcorrole (4a). This variation
corresponds with the fact that the electronegativity of the
meso substituents of the corrole ring decreases the elec-
tron density on chromium(V) and makes the π-bonding
character of the CrV=O moiety stronger.28
One-electron oxidation potentials of thienyl- and thia-
naphthyl-containing free-base corroles are similar to each
other and can be compared with tri-2-thienyl- and tri-3-
thienyl-meso-A3-corroles;18b the electrochemical oxida-
tion potentials of 1 and 3 are positively shifted by ∼0.5 V.
This observation can be explained in terms of a difference
of the electron-withdrawing strength of meso substituents
in the corrole ring. This notion corresponds to the oxida-
tion potentials of oxochromium(V) complexes 1a-3a,
which demonstrate quite similar values for the thienyl-
and thianaphthyl-containing ligands, but in the case of
the tri-3-thienylcorrole ligand (4a), its oxidation potential
is negatively shifted by ∼0.2 V.
A comparison of the electrochemical measurements
between the CuIII-containing compound 2b and tri-3-
thienylcorrole18b shows that the oxidation potential for
the ligand with two C6F5 groups is positively shifted by
0.23 V [0.50 vs 0.23 V, Fc/Fcþ, for 2b and tri-3-
thienylcorrolatocopper(III), respectively], also consistent
with patterns of the substituent electron-withdrawing
capacity.
Also, EPR studies were pursued to confirm the high-
oxidation-state nature of copper(III) in 2b. The Cu3þ ion
with a low-spin d8 configuration is EPR-silent but, under
treatment by NaBH4, copper(II), which has an intense
EPR signal and possesses a spin of 1/2, can be seen to form
(d9, I = 1/2)29 (Figure 2b).
Electrochemistry. The cyclic voltammograms of cor-
role ligands 1-3 and their corresponding chromium
complexes 1a-4a have been obtained, and their redox
potentials are also provided (Figure 3 and the Supporting
The reduction potential of the oxochromium(V) species
1a-4a can be discussed, together with the catalytic
activity of obtained compounds in oxygen-transfer reac-
tions; its mechanism suggests a reduction of CrV and oxida-
tion of organic substrates.30 The less positive CrVO/CrVI
(28) Fujii, H.; Yoshimura, T.; Kamada, H. Inorg. Chem. 1997, 36, 1122–
1127.
(29) Fox, J. P.; Ramdhanie, B.; Zabera, A. A.; Czernuszewicz, R. S.;
Goldberg, D. P. Inorg. Chem. 2004, 43, 6600–6608.
(30) Mahammed, A.; Gray, H. B.; Meier-Callahan, A. E.; Gross, Z. J.
Am. Chem. Soc. 2003, 125, 1162–1163.

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 509
Figure 4. (a) Time-dependent UV-vis spectra of 1a during aerobic oxidation of PPh3 to OdPPh3 in MeCN with the addition of 0.7% pyridine. (b)
UV-vis spectra of the oxidation of PPh3 to OdPPh3 during the first 10 min. See ref 18e for comparison with a closely related meso-ABC-corrolate.
potential supports a prediction of low catalytic activity
for the oxochromium(V) species. From this perspective, a
higher catalytic ability is suggested for the 1a and 3a
oxochromium(V) species, owing to a slightly higher po-
sitive reduction potential than that for 2a and a much
higher positive reduction potential than that for 4a. Thus,
the presence of relatively weak electron-withdrawing
groups, such as thienyl, at the periphery of the corrole
core, decreases the reduction potential of the CrV/CrIV
couple and, consequently, worsens the catalytic ability of
oxochromium(V) species toward oxidation of organic
substrates.
UV-Vis Spectroscopy and Titration of Free-Base Cor-
roles and Oxochromium Complexes with Metal Ions. A
UV-vis study for both the free-base corroles and metal-
locomplexes was carried out in methylene chloride be-
cause compounds are more stable in this solvent (see
the solvent stability assays in the Supporting In-
formation). Optical properties for all compounds are
given in Table 4.
Emission and absorption spectra of sulfur-containing
free-base corroles 1-4 were obtained upon the addition
of perchlorate salts32 of Csþ, Naþ, Kþ, Agþ, Ca2þ, Mn2þ
,
Co2þ, Ni2þ, Zn2þ, Cu2þ, Cd2þ, and Pb2þ. Titration data
of these show large absorption changes for the free-base
corroles (Figure 5), with markedly less selectivity for
Cu2þ (see the Supporting Information), demonstrating
strong ligand-metal ion interactions. Solutions of com-
pounds 1-3 changed from violet-green to light-green
upon the addition of Cu2þ, Pb2þ, Hg2þ, and Cd2þ, with
a decrease in λabs,max and bathochromic shifting [415 f
∼425 (1), 416 f ∼421 (2), and 423 f ∼433 (3)]; the
respective “Q bands” also underwent red shifts: 561 f
∼655 (1), 563 f ∼657 (2), and 565 f 657 (3). The greatest
decrease in the Soret band intensity for 1-3 occurred
upon Cu2þ addition. New spectral shoulders formed at
Catalytic Reactivity of Oxochromium(V) Species. We
have examined the catalytic activity of the oxochromium-
(V) species 1a toward PPh3 in acetonitrile. Acetonitrile
was chosen as the solvent because of the large solvent
effect that increases the rate of the oxidation reaction.30
Specifically, we observed an oxidation reaction of PPh3 to
O=PPh3 in the presence of 0.7% pyridine, which inhibits
reoxidation of CrIII to CrV. The catalytic cycle in the
reaction likely includes (i) reduction of CrV to CrIII with
additional coordination of two axial substrates and also
(ii) formation of the CrIV dimer as an intermediate.
UV-vis spectra (Figure 4) reflect that the catalytic reac-
tion is immediate; the new peak appearing at λabs,max of
435 nm corresponds to CrIV. A new shoulder at ∼477 nm
445 (1 and 2) and 453 nm (3) upon the addition of Cu2þ
,
Pb2þ, Hg2þ, or Cd2þ, consistent with the general degree of
thiophilicity of these metals. Deviation from direct cor-
role metallation may occur as a function of increased
sulfur richness, wherein other minor coordination possi-
bilities probably exist but have been pursued herein
neither experimentally nor computationally.
reflects a buildup in the concentration of Cr .
III 30 We can
then suggest that the less electron-withdrawing groups on
the periphery of the corrole ligand have a moderate effect
on decreasing the catalytic strength of the oxochromium-
(V) species. These results can be best placed in context
with respect to a previous comprehensive report by Gross
and co-workers.1c The complexes studied involved chro-
mium centers of closely related corrole complexes that
form, or were prepared, in stepwise valence states:1d
[(tpf)corCr(py)2] (trivalent), [(tpf)corCrdO][Cp2Co] (tetra-
valent), (tpf)corCrdO (pentavalent), and [[(tpf)cor•]Crd
O][SbCl6] (hexavalent). Also, with respect to the presence
of the CrdO bond and its oxidizing strength, there is the
important consideration of the frequency and strength of the
CrdO bond. This has been nicely addressed by a recent
report from Czernuszewicz and co-workers.1e
Type III Mnþ recognition was investigated by way of
screening 1a-5a with the same perchlorate salts32 as
those for free-base corroles. Solutions of 1a-3a (=L)
are not fluorescent, so only titrimetric UV-vis absorp-
tion data were obtained (Figure 6). Significantly, [Cu2þ
]
addition to 1a-3a (1:1 Mnþ/L) afforded a rapid, signifi-
cant, and selective optical response (pink f red-brown;
(31) Ding, T.; Aleman, E. A.; Modarelli, D. A.; Ziegler, C. Phys. Chem. A
2005, 109, 7411–7417.
(32) Churchill, D. G. J. Chem. Educ. 2006, 83, 1798.

510 Inorganic Chemistry, Vol. 49, No. 2, 2010
Egorova et al.
Table 4. Optical Properties for Free-Base and Metallocorrole Complexesa
log ε/(M-1 cm-1
)
λem,max (nm)
Stokes’ shift b (cm-1
)
c
φF
compound
λabs, max (nm)
1
2
3
415
416
421
407
402
403
404
402
407
402
5.20
5.10
5.04
4.51
4.87
4.86
4.80
4.91
4.64
4.94
631
657
631
642
519
1066
546
0.003
0.004
0.004
4d
1a
2a
3a
4ad
5a
2b
1059
a Spectral properties in CH2Cl2 at room temperature. b Stokes’ shifts were calculated from respective absorption and emission wavelengths. c Quantum
yields were calculated using fluorescein dissolved in 0.1 N NaOH as a reference (φ = 0.93). d Published data.20,31
Figure 5. Changes of the absorption spectra of (a) 1, (b) 2, and (c) 3 and emission spectra of (d) 1, (e) 2, and (f) 3 upon the addition of various metal ions.
The ligand/metal ion ratio is 1:1. The concentration of the ligand in CH2Cl2 is 1 ꢀ 10-5 M, and that of the Mnþ solution in CH3CN is 1 ꢀ 10-3 M. Excitation
wavelengths: 631 (1), 657 (2), and 631 nm (3).
Supporting Information). In the case of other metal ions,
very little change was observed.
using the Benesi-Hildebrand equation. These similar values
support the same proposed mode of binding, i.e., via the
The observed Cu2þ selectivity prompted us to carry out
titration experiments for 1a-3a with Cu(ClO4)2 (Figure 7).
The limit of quantification for [Cu2þ] in solutions of 1a-3a
was 1.0 ꢀ 10-5 M. The Job plot analysis confirmed 1:1
Cu2þ/L stoichiometry; Ka values for Cu2þ (1a, 6.9 ꢀ 104
M-1; 2a, 8.6 ꢀ 104 M-1; 3a, 6.9 ꢀ 104 M-1) were obtained
terminal oxo group, i.e., [MdO Cu2þ].
3 3 3
To pursue a fuller understanding of the meso-A2B-
oxocorrolate of chromium(V) and the nature of Mnþ
binding, we have considered comparisons between addi-
tional corrolato species (the CrVO-free moiety, 2b; the
“S-free” version, 4a; the C6F5-free version, 5a) and have

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 511
Figure 6. Changes of the absorption spectra of (a) 1a, (b) 2a, and (c) 3a upon the addition of various metal ions. The ligand/metal ion ratio is 1:1. The
concentration of the ligand in CH2Cl2 is 1 ꢀ 10-5 M, and that of the Mnþ solution in CH3CN is 1 ꢀ 10-3 M.
absorption band arising at ∼460 nm. These data indicate
a vastly different nature of interaction of 5a with Cd2þ
versus 5a with Cu2þ, Hg2þ, and Pb2þ. In the latter case, a
significant reconfiguration occurred at the sensing mole-
cule, suggestive that displacement of the CrVO moiety has
occurred. To investigate the Mnþ binding further, stoi-
chiometry and Ka values were obtained (Job plot and
Benesi-Hildebrand methods, respectively). In all cases,
L/Mnþ binding stoichiometry was 1:1, except for Hg2þ
,
which reflects a 1:2 binding ratio (see the Supporting
Information). Thus, taking all of the observations above
together allow us to suggest that (i) the contribution of the
CrVO moiety and the thienyl group S atom could be
operating together in varying degrees in metal ion chela-
tion andthus in metalrecognition and(ii) the combination
of one thienyl group with two C6F5 rings allows for the
retention of Cu2þ selectivity. Accordingly, the structure of
the thienyl meso-A2B oxocorrolates of chromium(V) is
more effective as a potential sensor when compared to A3
compounds (4a and 5a) or to the copper complex (2b).
Figure 7. UV-vis titration spectrum obtained by titration of a Cu2þ
solution in CH3CN to a solution of 1a (1 ꢀ 10-5 M) in CH2Cl2.
carried out a series of experiments (UV-vis, CV, and
EPR spectroscopy; see the Supporting Information).
Solutions of 2b, 4a, and 5a were treated with various
mono- and divalent metal ions for obtaining a 1:1 ratio of
L (2b, 4a, and 5a): Mnþ in solution (Supporting In-
formation). In comparison, through the use of UV titra-
tion data of 1a-3a, it should be noted that the S-free (4a)
and CrVO-free species (2b) also possess selectivity to
cupric ions, but in the case of 4a, the intensity of the
Soret band decreases with a retention of the Q-band
maximum upon the addition of Cu2þ. The spectrum of
the CrVO-free corrole (2b) possesses a sizable diminution
of the Soret band. These changes are comparable with the
transformations of 1a-3a upon Cu2þ addition. UV-
titration data of 5a revealed a significant interaction of
the compound with divalent ions, particularly upon
treatment with Hg2þ and Cu2þ (the Soret band disap-
pears; new λabs, max = 460 nm) and Cd2þ and Pb2þ [the
intensity of the Soret band decreases considerably; new
Conclusion
Herein, we provide the first examples of thienyl-meso-A2B-
and A2B-oxochromium(V) corrolates, which have been pre-
pared by standard methods and characterized by techniques
that include EPR spectroscopy, single-crystal X-ray diffrac-
tion, CV, UV-vis, and 2D NMR spectroscopy. This paper
also delineates three potential detection types (types I-III).
Rapid and selective type III (MdO Mnþ) detection was
3 3 3
fruitful for Cu2þ, known for its biological role in neurode-
generation. The MdO group in porphyrin-(un)like systems
has been carefully considered as the active portion of the real
“compound I” or in structural/reactive mimics of it.1 While
chromium was explored here, studies of more metal-contain-
ing systems will help broaden the understanding of type II
sensing capabilities. A type I detection potential was also
catalogued herein, whereas results pertaining to a type II
detection potential were briefly discussed only (Scheme 1).
We emphasize the potential in integrating detection “types
I-III”, which should prove very interesting, based on the
many previous catalytic investigations of corroles reported so
far. Subtleties of type I-III optics can be addressed through
future theoretical calculations as well.
λ
abs, max = ∼460 nm (Pb2þ) or a shoulder (Cd2þ) forms].
Additionally, we titrated 5a by Cu2þ, Hg2þ, Pb2þ, and
Cd2þ separately for a final analysis of the behavior of 5a
upon the addition of excess metal ion (Supporting
Information). Titration data for 5a by Cd2þ did not
show large spectral changes: the intensity of the Soret
band decreased slightly; new shoulders at ∼460 and
625 nm did form. For the Cu2þ, Hg2þ, and Pb2þ titra-
tions, the spectrum of 5a transformed dramatically: the
Soret band disappeared completely, with a new concomitant
Acknowledgment. D.G.C. acknowledges support from
the Korea Science and Engineering Foundation (KOSEF;

512 Inorganic Chemistry, Vol. 49, No. 2, 2010
Egorova et al.
Grant R01-2008-000-12388-0) and the National Research
Foundation of Korea (Grant N01090203). O.A.E. was
supported in the Molecular Logic Gate Laboratory by
a BK-21 postdoctoral fellowship. J.K. acknowledges
support from the Nano/Bio Science & Technology Pro-
gram (Grant 2005-01333) of the Ministry of Education,
Science and Technology. Hack Soo Shin helped greatly
in acquiring NMR spectroscopic data. Teresa Linstead
(CCDC) is acknowledged for aiding in the structural data
deposition.
Supporting Information Available: Details of syntheses,
NMR and UV-vis spectra, additional discussion, CV plots,
EPR spectra, and crystallographic data in CIF format. This
material is available free of charge via the Internet at http://
pubs.acs.org.