A2B type copper(III)corroles containing zero-to-five fluorine atoms: Synthesis, electronic structure and facile modulation of electrocatalyzed hydrogen evolution

Article abstract of DOI:10.1016/j.dyepig.2016.10.044

Four low symmetric A₂B meso-substituted Cu(III)corroles with electron withdrawing meso-aryl rings have been synthesized and characterized. A detailed analysis of the optical and redox properties has been carried out by comparing their optical s

Full text of DOI:10.1016/j.dyepig.2016.10.044

Accepted Manuscript
A B type copper(III)corroles containing zero-to-five fluorine atoms: Synthesis,
2
electronic structure and facile modulation of electrocatalyzed hydrogen evolution
Minzhi Li, Yingjie Niu, Weihua Zhu, John Mack, Gertrude Fomo, Tebello Nyokong, Xu
Liang
PII:
S0143-7208(16)30551-4
10.1016/j.dyepig.2016.10.044
DYPI 5560
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 24 August 2016
Revised Date: 2 October 2016
Accepted Date: 29 October 2016
Please cite this article as: Li M, Niu Y, Zhu W, Mack J, Fomo G, Nyokong T, Liang X, A B type
2
copper(III)corroles containing zero-to-five fluorine atoms: Synthesis, electronic structure and facile
modulation of electrocatalyzed hydrogen evolution, Dyes and Pigments (2016), doi: 10.1016/
j.dyepig.2016.10.044.
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ACCEPTED MANUSCRIPT
A2B type Copper(III)corroles Containing Zero-to-Five Fluorine Atoms: Synthesis,
Electronic Structure and Facile Modulation of Electrocatalyzed Hydrogen Evolution
Minzhi Li,a,† Yingjie Niu,a,† Weihua Zhu,a,* John Mackb,* Gertrude Fomo,b Tebello Nyokongb and Xu
Lianga,*
a. School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, P. R. China.
E-mail: liangxu@ujs.edu.cn (X. Liang); sayman@ujs.edu.cn (W. Zhu), Tel&fax: +86-511-8879-1928
b. Department of Chemistry, Rhodes University, Grahamstown 6140, South Africa. E-mail:
j.mack@ru.ac.za, fax: +27-46-622-5109
† These authors are contributed equally.
Abstract
Four low symmetric A2B meso-substituted Cu(III)corroles with electron withdrawing meso-aryl
rings have been synthesized and characterized. A detailed analysis of the optical and redox
properties has been carried out by comparing their optical spectroscopy, electrochemistry and
spectroelectrochemistry to a series of DFT and TD-DFT calculations. A series of experiments
demonstrate that these Cu(III)corroles can be used as highly effective catalysts for hydrogen
evolution reactions (HERs). Moreover, when the number of fluorine atoms at B meso-position is
increased, there is a marked enhancement in the catalytic ability of the corrole complexes, which
demonstrates that modification to the structures of low symmetry corroles is a useful strategy for
developing new HER catalysts.
Key words
Cu(III)corrole; Electronic Structure; TD-DFT calculation; Hydrogen Evolution
1

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1. Introduction
In recent years, increased energy demands and serious environmental concerns, have made
research on clean energy sources one of the most important tasks for modern society.[1] Hydrogen
has many advantages in this regard and is widely considered to be the next generation energy
source that will replace the use of fossil fuels.[2] In addition, there has been increasing interest in
hydrogen evolution reactions (HERs) that involve the electrochemical reduction of protons, due to
the convenient procedures that are involved and the availability of catalytic materials to convert
electrical energy to chemical energy through the generation of H2.[3] Although platinum enables
highly efficient electrocatalysis, less-expensive and more abundant transition metal complexes
would be preferable for use as catalysts in HERs. Additionally, recent research interest has
identified complexes containing transition metal-centers such as iron,[4] cobalt,[5] nickel,[6] and
molybdenum[7] that are redox active for HER catalysis, but their low catalytic efficiencies and
insufficient stability in the concentrated acid environments that are used in this context has limited
the further development of this field of research.[8]
The development of new and stable molecular catalysts with high-valent metal centers that
can provide highly efficient and robust HER catalysts remains a significant challenge in the energy
research community. Corroles are porphyrin analogues with a direct pyrrole-pyrrole bond and an
extra NH proton on the inner ligand perimeter.[9] In recent decades, there has been a strong
research focus on the use of corroles as functional ligands, largely due to their ability to stabilize
higher oxidation states of the coordinated central metal.[10] Metallo-corroles with central ions in
unusual valence states can be rationally prepared through structural modifications to the corrole
rings.[11] These complexes have been used in various kinds of catalytic reactions including organic
synthesis,[12] the removal of environmental harmful pollutants[13] and HERs.[14]
The enhancement of the efficiency of the HERs through structural modifications to the corrole
ligand has not been studied in depth. A2B type low symmetry corroles (Scheme 1) are obvious
candidates for study in this regard, since they can be easily modified by changing only one of the
meso-substituents. In this manuscript, the synthesis, characterization, spectroscopy, redox
properties and spectroelectrochemistry of a series of copper(III) corroles with zero, one, two and
five fluorine atoms on the B meso-aryl ring (Scheme 1) will be described, along with an investigation
of their potential utility for use as catalysts in HERs. Cu(III)corroles were selected for study, since
2

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copper is a naturally abundant element with a redox chemistry that may be suitable for modulating
HERs in a simple manner
2. Results and discussions
2.1 Synthesis and Characterizations
The synthetic procedure is shown in Scheme 1, H3-corrole
1
was synthesized according
2d were
to literature through so-called water-methanol system.[17] Cu(III)corroles 2a
-
finally synthesized by metal insertion reactions, and all details about experimental parts are
described in the supporting information (see ESI). The MALDI-TOF-mass spectra of 2a
reveals a strong parent peak at m/z = 675.22 (Calcd [M]+ = 675.15), providing direct
evidence that the target Cu(III)-5,15-(m-nitrophenyl)-10-phenylcorrole was successfully
obtained. Similar MALDI-TOF-mass peaks were also observed for Cu(III)corroles 2b
-
2d
.
1
The proton signals for the meso-substituents and pyrrole rings in the H NMR spectra of
2
are similar to those reported previously for high symmetry triarylcorroles (Figure S1).[9] 19
NMR spectra contain a singlet peak at 111.83 ppm for 2b, a triplet peak at 109.92 ppm
for 2c, and a group of peaks at 137.42~ 138.05, 151.99, and 160.57 ppm for 2d which is
F
−
−
−
−
−
−
consistent with the presence of one, two, and five fluorine atoms, respectively (Figure S2).
Optimized geometries were calculated for 2a-d by using the B3LYP functional of the
Gaussian 09 software package[15] with 6-31G(d) basis sets. TD-DFT calculations were
carried out in a similar manner by using the CAM-B3LYP functional, which includes an
increasing fraction of Hartree-Fock (HF) exchange as the interelectronic separation increases
so that a long-range correction is introduced. This is expected to provide more accurate
results for porphyrinoid transitions in which there is significant charge transfer in the
electronic excited states,[16] as is likely to be the case in the spectra of 2a-d
.
2.2 Optical spectra and TD-DFT calculations
3

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When compared to the Q band absorption of Cu(III)-meso-triphenyl-corroles,[13a] the electron
deficient Cu(III)corrole 2a exhibits a blue-of Q band; 2b: 621 nm, 2c: 608 nm, 2d: 593 nm (Figure 1),
which is proportional to the electron-withdrawing ability. The electronic structures and optical
spectroscopy of porphyrinoids can be readily understood by using Gouterman’s 4-orbital model[18]
and Michl’s perimeter model[19] as conceptual frameworks, through a consideration of the
2−
structural perturbations that are made to the molecular orbitals (MOs) of a C16H16 parent
hydrocarbon perimeter. The MOs are arranged in an ML = 0, ±1, ±2, ±3, ±4, ±5, ±6, ±7, 8 sequence in
ascending energy in terms of their angular nodal properties. The highest occupied molecular
orbital (HOMO) and lowest occupied molecular orbital (LUMO) have ML values of ±4 and ±5.
Michl[19] referred to π-MOs derived from the HOMO and LUMO of the parent perimeter with
angular nodal planes that lie on the y-axis as a and −a, respectively, while the corresponding MOs
that have y-axis atoms with significant MO coefficients are referred to as the s and −s MOs (Figure
2). This terminology facilitates the comparison of trends observed in the MO energies of complexes
of differing symmetries. The four spin-allowed transitions between the a, s, −a and −s MOs provide
the basis for Gouterman’s 4-orbital model, which consists of an allowed B transition (∆ML = ±1) and
a forbidden Q transition (∆ML = ±9).
In the context of 2a-d, introduction of a Cu(III) ion with a d8 metal ion is predicted to introduce
an MO with significant 3d
character asthe LUMO, while the s and a MOs are the HOMO and
2
x -y
2
HOMO−1. In shift of the Q bands at 543 and 624 nm. As the number of fluorine atoms on the B
meso-aryl ring increases there is a further blue shift addition to the −a and −s MOs, two MOs
associated primarily with the B2 meso-aryl rings also lie within 1.5 eV of the LUMO. The
introduction of different A phenyl groups is predicted to make relatively little difference to the
energies of the frontier MOs and hence the magnitudes of the HOMO-LUMO gaps, as is anticipated
when minor differences in the inductive effects of the aryl groups are involved. The trends
observed in the predicted MO energies are therefore consistent with the relatively minor changes
that are observed in the experimental and calculated optical spectra of 2a-d (Figures 1 and 3).
The weaker absorption bands and the coupled pair of Faraday B0 in the 500-700 nm region can
be assigned to the Q transitions (Figure 1), while the main absorption band at ca. 409 nm can be
readily assigned to the B (or Soret) transitions, on the basis of TD-DFT calculations (Figure 4).
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Forbidden ligand-to-metal charge transfer (LMCT) bands are predicted to lie beyond 1000 nm, so
fluorescence emission is not anticipated in the Q band region. The +/- sign sequence in ascending
energy terms observed in the Faraday B0 terms in the Q band region (Figure 1) is the pattern
typically observed for corroles,[9a] since the separation of the MOs derived from the LUMO of the
parent perimeter (referred to as the ΔLUMO value to use Michl’s terminology[19] is greater than
those derived from the HOMO level of the parent perimeter (the ΔHOMO value).[19] The more
complex +/-/+ sign sequence is probably due to configurational interaction with a close-lying
excited state with LMCT character. The weaker bands to the blue of the B band at ca. 409 nm can
also be assigned as being primarily LMCT in origin, along with transitions to the ππ* states
associated with the low-lying MOs that are associated with the B2 meso-aryl rings (Figure 2).
2.3 Electrochemistry
To gain further insight into the electronic structures of Cu(III)corrole 2a-2b and the effect of
solvent polarity on the electronic properties, electrochemical measurements were carried out in
o-dichlorobenzene (o-DCB) as a typical low-polar solvent, and high-polar dimethylformamide (DMF)
and PhCN containing 0.1M tetra-n-butylammonium perchlorate ([NtBu]ClO4; TBAP). The redox
potentials (E ) values derived from both CV and DPV measurements (Figure 4). When
½
electron-withdrawing substituents are introduced at the meso-positions of Cu(III)corroles, there is a
decrease in the electron density of the metallo-corrole π-conjugation system, thereby leading to
significantly easier reduction and more difficult oxidation.[20] The cyclic voltammogram for 2a
consists of a reversible first reduction step at E = 0.02 V (in o-DCB), which can be assigned to the
½
[Cu(III)Corrole]/[Cu(II)Corrole]- [20b,c]. When the number of fluorine atoms on the B meso-aryl ring is
increased, a positive shift of the E value is observed in o-DCB at 0.01 V for 2b, 0.04 V for 2c, and
½
0.09 V for 2d. In addition, the first oxidation step of 2a-2d in o-DCB can be assigned as
[Cu(III)Corrole]/[Cu(III)Corrole]+ [20b,c] with E values of 1.01 V for 2a, 1.04 V for 2b, 1.03 V for 2c,
½
and 1.09 V for 2d. The 2nd reduction processes are quite similar since it is associated with the
reduction of a nitro-unit at the m-positions of the A2 meso-aryl rings.[21] Although similar
electrochemical curves are observed, the E1/2 values change significantly due to the effect of
solvent polarity on the electronic structure of the Cu(III)corroles, and the positive-shift of the E
½
5

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values, which follows the number of fluorine atoms on going from 2a to 2d. In the case of 2a in
DMF and acetonitrile, two reversible processes were observed at E = 0.17 and -1.01 V in DMF and
½
E = 0.00 and -1.20 V in acetonitrile. A reversible 1st oxidation process is also observed for 2a at E
½
½
= 0.93 V in PhCN. Similar electrochemical behaviors are observed for 2b-d in the polar solvents
(Figure 4). The trend observed in the gaps between the first reduction and oxidation steps are
consistent with the slight blue-shift of the main Q and B bands that is observed spectroscopically
and predicted in theoretical calculations. The number of fluorine atoms on the meso-substituents
affects their electron-withdrawing properties and hence results in a significant decrease of the
electron density of the Cu(III)corrole π-system in a manner that results in a slight increase in the
magnitude of the HOMO-LUMO gap.
2.4 Spectroelectrochemistry
Thin-layer UV-visible absorption spectroelectrochemical studies were carried out in o-DCB and
DMF containing 0.1 M TBAP to characterize the one-electron oxidized and reduced products in
solvents with both low and high polarity. The spectral data obtained for the neutral, singly reduced
and singly oxidized copper corroles are shown in Figure 5 (left) along with the spectral changes
obtained for the Cu(III)/Cu(II) (first reduction) and Cu(III)/[Cu(III)]+ π-cation (first oxidation)
processes. After the first reduction step of 2a, the B band decreases in intensity while a new band
gains intensity at longer wavelength. The B band of neutral Cu(III)corrole 2a lies at 414 nm in o-DCB,
while that of the singly reduced species lies at 432 nm, with a visible region band also observed at
ca. 600 nm (Figure 5). The reduction can be assigned to a metal-centered electron transfer
process and leads to the formation of the Cu(II)corrole as has previously been reported for other
related Cu(III) corroles.[22] Somewhat different spectral changes are observed for 2b-2d, since the
B bands of 2b-2d undergo almost no shift in the λmax value, but there is an increase in intensity in
the Q band region at ca. 600 nm. The first oxidation steps of 2a-d in o-DCB result in the formation
of a [Cu(III)]+ π-cation species and a similar set of spectral changes are observed in each case, which
is consistent with the formation of a Cu(III) π-cation. The B band intensity decreases while there is
increased intensity in the Q band region beyond 600 nm. When the solvent polarity was increased
by using DMF rather than o-DCB containing 0.1 M TBAP, spectral changes were observed (Figure 5,
6

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left). During the first reduction step, the B bands of 2a-2d at ca. 410 nm decrease in intensity and
is replaced by a new band at ca. 435 nm. In contrast, differing spectral changes are observed
during the first oxidation steps. The B band of 2a decreases in intensity, while new band maxima
only appear in the spectra of 2b-2d. It is noteworthy that substitution with differing numbers of
fluorine atoms results in significant spectral changes in this context.
2.5 Catalysis of HERs
Stability in acidic environments is a key concern when designing new HER catalysts,
although improved acid tolerance has been reported in several systems.[13] The stability of
2a-2d in concentrated solutions of TFA in PhCN has been evaluated
(Figure 6).
Cu(III)corrole 2a-2d and trifluoroacetic acid (TFA, 1:4 molar ratio) were mixed in PhCN, and
care was taken to keep the solutions in the dark, so the stability of 2a-d could be verified by
measuring series of UV-visible absorption spectra over 4h. Only very minor spectral
changes were observed. The HER catalysis properties of 2a-d were examined with the
most important parameters being the kinetic reactivity (icat/ip) and onset potentials. The
addition of TFA to homogeneous PhCN solutions induced catalytic waves, which were
observed at potentials near to the CuIII/CuII couple of the Cu(III)corrole complexes. The first
reduction step for Cu(III)corrole 2a generates [Cu(II)corrole]− anions. A region with
acid-dependent behavior was observed at around E = −0.80 V after 1.0 equiv. of TFA was
5
added to 1 × 10− M solutions of 2a-d in PhCN (Figure 7). In the case of 2b-2d, there is a
clear increase in the icat/ip ratio as the number of fluorine atoms on B meso-ring is increased,
which demonstrates that the electron withdrawing properties of the B meso-aryl ring have a
large influence on the catalysis properties. In addition, the catalytic wave increases in
amplitude when the acid concentration is increased and progressively shifts to more
negative potentials. When various TFA concentrations were added to enable a comparison
of the catalytic activities of 2a-d (Figure S3, Figure 8), 2d with five fluorine atoms was found
to be the most efficient catalyst, followed by 2c and then 2b with 2a being the least
reactive, since it contains no fluorine atoms. On the other hand, the increased
scan-speed-dependent peak current (icat) values determined from CV measurements for
7

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2a-
2d made at various scan-rates (10, 20, 50, 100, 300 and 500 mV/s) provide further
½
insights (Figure S4). The high linear correlations observed in plots of peak current vs. v for
2a-2d confirm that all of the processes are diffusion controlled (Figure S5).
3. Conclusions
A series of four meso-substituted A2B copper(III)corroles containing zero to five fluorine atoms
on the B meso-substituent have been synthesized and characterized. A detailed analysis of the
UV-visible absorption and MCD spectra, cyclic and differential pulse voltammetry measurements,
and DFT and TD-DFT calculations has been carried out to identify the main trends in the electronic
structures and optical properties. It has been demonstrated that these Cu(III) corroles are highly
effective catalysts for hydrogen evolution. When the number of fluorine atoms at the
meso-position is increased, there is a marked enhancement in the catalysis of HERs, which indicates
that the efficiency of the reaction can be readily enhanced by changing the meso-substituents of
low symmetry corroles.
4. Acknowledgements
Financial support was provided by Natural Science Foundation of China (No. 21171076) and Natural
Science Foundation of Jiangsu Province (No. BK20160499) to XL and WZ and an NRF of South Africa
CSUR grant (uid: 93627) to JM. The theoretical calculations were carried out at the Centre for
High Performance Computing in Cape Town.
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19Gouterman M, In The Porphyrins; D. Dolphin, Ed.; Academic Press: New York, 1978; Vol. III,
Part A, pp 1-165.
20(a) Michl J, J. Am. Chem. Soc. 1978; 100: 6801. (b) Michl J, Pure Appl. Chem. 1980; 52: 1549.
(c) Michl J, Tetrahedron 1984; 40: 3845.
21(a) Paolesse R, In The Porphyrin Handbook; Kadish KM, Smith KM, Guilard R, Eds.; Academic
Press: San Diego, CA, 2000; Vol. 2, pp 201-232; (b) Erben C, Will S, Kadish KM, In The
Porphyrin Handbook; Kadish KM, Smith KM, Guilard R, Eds.; Academic Press: San Diego, CA,
2000; Vol. 2, pp 233-300. (c) Guilard R, Barbe JM, Stern C, Kadish KM, In The Porphyrin
Handbook; Kadish KM, Smith KM, Guilard R, Eds.; Elsevier: San Diego, CA, 2003; Vol. 18, pp
303-349. (d) Shen J, Shao JG, Ou ZP, Koszarna WBEB, Gryko DT, Kadish KM, Inorg. Chem.
2006; 45: 2251.
22(a) Sun B, Ou ZP, Yang SB, Meng DY, Lu GF, Fang YY, Kadish KM, Dalton Trans. 2014; 43: 10809.
(b) Li BH, Ou ZP, Meng DY, Tang JJ, Fang YY, Liu R, Kadish KM, J. Inorg.
Biochem. 2014; 136: 130.
23(a) Ou ZP, Shao JG, Zhao H, Ohkubo K, Wasbotten IH, Fukuzumi S, Ghosh A, Kadish KM, J.
Porphyrins Phthalocyanines 2004; 8: 1236. (b) Pomarico G, Xiao X, Nardis S, Paolesse R,
Fronczek FR, Smith KM, Fang YY, Ou ZP, Kadish KM, Inorg. Chem. 2010; 49: 5766. (c) Lu GF,
Lin WS, Fang YY, Zhu WH, Ji XL, Ou ZP, J. Porphyrins Phthalocyanines 2011; 15: 1265.
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Schemes and Figures
Scheme 1 Synthesis of Cu(III)corrole 2a-2d.
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Figure 1 UV-vis (bottom) and MCD spectra (up) of Cu(III)corroles 2a-2d in CH2Cl2 at room
temperature.
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Figure 2 Angular nodal patterns and energies of the six MOs of 2a that lie between 0 and −8
eV in the TD-DFT calculation with the CAM-B3LYP functional and 6-31G(d) basis sets (TOP).
The MO energies for 2a
(BOTTOM). The and
used for the and
and are denoted with orange diamonds.
-
d
in the TD-DFT calculations with the CAM-B3LYP functional
a
−a MOs are denoted with black triangles, while black crosses are
MOs. The HOMO
s
−s
−LUMO gaps are plotted against a secondary axis
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Figure 3 TD-DFT calculations for 2a-d with the CAM-B3LYP functional and 6-31G(d) basis sets
(TOP). The MO energies for 2a-d in the TD-DFT calculations with the CAM-B3LYP
functional (BOTTOM). The Q and B bands are denoted with red diamonds, while gray and
green diamonds are used for LMCT bands and bands associated with ππ* transitions into
the low-lying MOs that are associated with the B2 meso-aryl rings (Figure 3). Details are
provided in Table S1, ESI.‡
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Figure 4 Cyclic voltammetry measurements of Cu(III)corroles 2a-2d in o-dichlorobenzene
(o-DCB) (left), DMF (middle) and PhCN (right) containing 0.1 M TBAP, scan rate: 100 mV/s.
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Figure 5 Spectroelectrochemistry of 2a-2d during the Cu(III)/Cu(II) (first reduction) and
Cu(III)/[Cu(III)]+ π-cation (first oxidation) processes in o-DCB and DMF containing 0.1 M
TBAP.
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Figure 6 UV-visible absorption spectra of 2a-2d in the presence of 4.0 equiv. of TFA in CH2Cl2
solution over 4h in the dark.
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Figure 7 Electrochemistry of 2a-2d in PhCN in the presence or absence of 1.0 eq TFA containing
0.1M TBAP, scan rate: 100 mV/s.
19

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Figure 8 Plot of icat/ip values of 2a-2d upon addition of TFA in PhCN containing 0.1M TBAP, all
values are derived from CV measurement.
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Supporting Information
A2B type Copper(III)corroles Containing Zero-to-Five Fluorine Atoms: Synthesis,
Electronic Structure and Facile Modulation of Electrocatalyzed Hydrogen Evolution
Minzhi Li,a,† Yingjie Niu,a,† Weihua Zhu,a,* John Mackb,* Gertrude Fomo,b Tebello Nyokongb and Xu
Lianga,*
a. School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, P. R. China.
E-mail: liangxu@ujs.edu.cn (X. Liang); sayman@ujs.edu.cn (W. Zhu), Tel&fax: +86-511-8879-1928
b. Department of Chemistry, Rhodes University, Grahamstown 6140, South Africa. E-mail:
j.mack@ru.ac.za, fax: +27 46-622-5109
† These authors are contributed equally.
Experimental
General
1H NMR spectra were recorded on a Bruker AVANCE 400 spectrometer (operating at 400.03
1
MHz) using the residual solvent as an internal reference for H (
δ
= 7.26 ppm for CDCl3,
δ
= 5.32
ppm for CD2Cl2). All reagents and solvents were of commercial reagent grade and were used
without further purification except where noted. Cyclic voltammetry was performed in a
three-electrode cell using Chi-730D electrochemistry station. A glassy carbon disk electrode was
utilized as the working electrode while a platinum wire and a saturated calomel electrode (SCE)
were employed as the counter and reference electrodes, respectively. UV-visible
spectroelectrochemical measurements were performed with a home-made optically transparent
thin-layer cell with Pt mesh as the working electrode. The potential was applied using a Chi-730D
potentiostat. UV-visible spectra were recorded with a HP 8453A diode array spectrophotometer.
All electrochemical and spectroelectrochemical measurements were carried out under a nitrogen
atmosphere. Magnetic circular dichroism (MCD) spectra were recorded on a JASCO J-815
spectrodichrometer equipped with a JASCO electromagnet, which produces magnetic fields of up to
1.6 T (1 T = 1.0 tesla) with both parallel and antiparallel fields. The conventions of Piepho and
Schatz are used to describe MCD intensity and the Faraday terms[15]
.
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Theoretical calculations
Optimized geometries were calculated for 2a-d by using the B3LYP functional of the Gaussian
09 software package with 6-31G(d) basis sets. TD-DFT calculations were carried out in a similar
manner by using the CAM-B3LYP functional, which includes an increasing fraction of Hartree-Fock
(HF) exchange as the interelectronic separation increases so that a long-range correction is
introduced. This is expected to provide more accurate results for porphyrinoid transitions in which
there is significant charge transfer in the electronic excited states, as is likely to be the case in the
spectra of 2a-d
.
Synthesis and Characterizations
Synthesis of Cu(III)-5,15-(m-nitrophenyl)-10-phenylcorrole
H3-5,15-( -nitrophenyl)-10-phenylcorrole ( , 30.83 mg, 0.05 mmol) and CuAc2·H2O (79.84 mg, 0.4
2a.
A
mixture
of
m
1
mmol, 8.0 eq) was dissolved in a solution of CH2Cl2 (5 mL) and methanol (20 mL). The mixture was
stirred at room temperature until the color changed to yellow-brown, and the temperature was
increased to 75°C for 2h. After removal of solvent, purification by chromatography (CH2Cl2: hexane
= 1:1, v/v) to give pure compound in 86.3% yield (29.2 mg). MALDI-TOF-mass: m/z = 675.22 (Calcd.
[M]+ = 676.15). IR (KBr, , cm-1): 3448 (s), 3082 (m), 2923 (m), 2854 (m), 2367 (m), 1676 (m), 1610
v
(w), 1572 (w), 1529 (vs), 1499 (w), 1425 (w), 1350 (vs), 1309 (m), 1278 (w), 1263 (w), 1225 (w), 1190
(w), 1166 (w), 1097 (w), 1057 (s), 1021 (s), 981 (m), 845 (m), 806 (w), 789 (m), 763 (m), 740 (w), 715
(s), 685 (w). 1H NMR (CD2Cl2, 298K): δH, ppm 8.61 (2H, s), 8.48 (2H, m), 8.11 (2H, d,
(2H, d, = 4.0 Hz), 7.77-7.73 (2H, t, 1 = 8 Hz, 2 = 8 Hz), 7.71-7.67 (5H, dd, 1 = 7.6 Hz,
7.54-7.50 (2H, t, 1 = 7.6 Hz, 2 = 7.6 Hz), 7.32 (4H, t, 1 = 6.4 Hz, 2 = 5.2 Hz).
J
= 7.6 Hz), 7.97
J
J
J
J
J
2 = 15.2 Hz),
J
J
J
J
Synthesis of Cu(III)-5,15-(m-nitrophenyl)-10-(p-fluorophenyl)-corrole 2b. The general synthetic
procedure is same as that of 2a, except H3-5,15-( -nitrophenyl)-10-( -fluorophenyl)-corrole was
used instead. The target compound was finally obtained in 87.2% yield (30.3 mg).
MALDI-TOF-mass: m/z = 693.23 (Calcd. [M]+ = 694.14). IR (KBr, , cm-1): 3423 (s), 3095 (w), 2967 (w),
m
p
v
2924 (w), 2361 (m), 1600 (m), 1529 (vs), 1509 (w), 1425 (m), 1350 (vs), 1310 (m), 1225 (s), 1192 (w),
1158 (s), 1096 (w), 1058 (s), 1022 (s), 981 (m), 845 (m), 806 (w), 789 (m), 768 (w), 741 (w), 714 (s),
685 (w). 1H NMR (CDCl3, 298K): δH, ppm 8.57 (2H, s), 8.41 (2H, m), 8.04 (2H, d,
J = 7.6 Hz), 7.90 (2H,
22

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d,
J
= 4.4 Hz), 7.67-7.54 (6H, m), 7.25 (4H, d,
F, ppm -111.83 (1F, s).
J1 = 4.8 Hz), 7.16-7.12 (2H, t, J1 = 6.4 Hz, J
2 = 8 Hz). 19F
NMR (CDCl3, 298K):
δ
Synthesis of Cu(III)-5,15-(m-nitrophenyl)-10-(2,6-difluoro-phenyl)-corrole 2c. The general synthetic
procedure is same as that of 2a, except H3-5,15-( -nitrophenyl)-10-(2,6-difluorophenyl)corrole was
used instead. The target compound was finally obtained in 87.2% yield (30.3 mg).
MALDI-TOF-mass: m/z = 712.65 (Calcd. [M]+ = 712.13). IR (KBr, , cm-1): 3434 (s), 3105 (s), 2966 (w),
m
v
2925 (w), 2363 (m), 1618 (s), 1573 (m), 1529 (vs), 1462 (s), 1425 (w), 1400 (w), 1389 (s), 1350 (vs),
1324 (w), 1306 (w), 1275 (m), 1235 (m), 1193 (w), 1167 (s), 1083 (w), 1059 (s), 1020 (s), 999 (s), 981
1
(m), 877 (w), 846 (m), 821 (w), 805 (m), 782 (s), 714 (s), 684 (w), 571 (m), 510 (w). H NMR (CD2Cl2,
298K): δH, ppm 8.58 (2H, s), 8.46-8.43 (2H, dd,
(2H, t, 1 = 8.0 Hz, 2 = 7.6 Hz), 7.59 (3H, m), 7.34 (2H, d,
m). 19F NMR (CDCl3, 298K): δF, ppm -109.92 (2F, t).
J
1 = 1.2 Hz,
J
2 = 8.4 Hz), 8.10 8.04 (4H, m), 7.77-7.73
= 4.4 Hz), 7.14 (2H,
J
J
J
= 4.4 Hz), 7.25 (2H, d, J
Synthesis of Cu(III)-5,15-(m-nitrophenyl)-10-pentafluoro-phenyl-corrole 2d. The general synthetic
procedure is same as that of 2a, except H3-5,15-( -nitrophenyl)-10-pentaflurophenylcorrole was
used instead. The target compound was finally obtained in 83.1% yield (31.8 mg).
MALDI-TOF-mass: m/z = 767.46 (Calcd. [M+H]+ = 767.10). IR (KBr, , cm-1): 3420 (m), 3087 (w), 2970
m
v
(w), 2925 (w), 1650 (w), 1612 (w), 1574 (w), 1529 (vs), 1499 (w), 1442 (w), 1384 (w), 1350 (vs), 1322
(w), 1302 (w), 1280 (w), 1229 (w), 1194 (w), 1165 (w), 1082 (m), 1058 (s), 1041 (m), 1023 (m) , 987
(s), 951 (s), 910 (w), 846 (m), 821 (w), 805 (m), 773 (s), 760 (m), 740 (w), 708 (s), 684 (w), 648 (w).
1H NMR (CD2Cl2, 298K): δH, ppm 8.59-8.55 (2H, d,
7.75-7.71 (2H, t, 1 = 8.0 Hz, 2 = 7.6 Hz), 7.54 (2H, d,
= 4.4 Hz). 19F NMR (CDCl3, 298K):
J
= 12.4 Hz), 8.45 (2H, d,
J
= 8.4 Hz), 8.04 (4H, m),
= 4.4 Hz), 7.17 (2H, d, J
J
J
J
= 3.2 Hz), 7.31 (2H, d,
J
δ
F, ppm -137.42--138.05 (2F, t), -151.99 (1F, t), -160.57 (2F, t).
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Figure S1 1H NMR spectra of 2a and 2c in CDCl3, and 2b and 2d in CD2Cl2.
24

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Figure S2 19F NMR spectra of 2c in CDCl3, and 2b and 2d in CD2Cl2.
25

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2b
2a
2d
2c
Figure S3 Electrochemistry of 2a-2d in PhCN in the presence of 0-10.0 eq TFA containing 0.1M TBAP,
scan rate: 100 mV/s.
26

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Figure S4 Electrochemistry of 2a-2d at different scan speeds in PhCN in the presence of 1.0 eq TFA
containing 0.1M TBAP.
27

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Figure S5 The dependence of square root of the scan-rate (v1/2) on the catalytic peak current ( p
HER reactions during cyclic voltammetry measurements of 2a-2d.
i ) for
28

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Tables
Table S1. TD-DFT spectra of the B3LYP optimized geometries for 2a-2d calculated with the CAM-B3LYP functional
and 6-31G(d) basis sets.
2a
Banda #b
Calcc
Expd
Wave Functione =
----
1
4
5
9
---- ---- ----
---- ---- Ground State
20.1 498 (0.13) 16.0 625 74% s → -a
;
13% a → -s; …
22% s → -s; …
Q
21.1 474 (0.03) 18.4 543 62% a → -a
;
26.9 372 (0.51) 23.1 432 35% s → LUMO+2; 28% a→ -a
;
27% s → -s; …
B
10 27.4 365 (0.74) 24.6 407 41% s → LUMO+2; 31% a → -s
; 17% a → -s; …
2b
Banda #b
Calcc
Expd
Wave Functione =
----
1
4
5
9
---- ---- ----
---- ---- Ground State
13% a → -s; …
21% s → -s; 11% s → LUMO+2; …
20.1 498 (0.13) 16.0 625 74% s → -a
21.1 474 (0.03) 18.4 543 62% a → -a
26.9 372 (0.53) 23.1 432 35% s → LUMO+2; 29% a→ -a
;
Q
;
;
26% s → -s; …
B
10 27.4 365 (0.74) 24.6 406 41% s → LUMO+2; 30% a → -s
; 17% a → -s; …
2c
Banda #b
Calcc
Expd
Wave Functione =
----
1
4
5
9
---- ---- ----
---- ---- Ground State
12% a → -s; …
20% s → -s; 13% s → LUMO+2; …
20.1 497 (0.12) 16.0 624 73% s → -a
21.1 474 (0.02) 18.4 543 62% a → -a
26.9 373 (0.58) 23.0 435 36% s → LUMO+2; 30% a→ -a
;
Q
;
;
25% s → -s; …
B
10 27.4 366 (0.75) 24.5 408 43% s → LUMO+2; 27% a → -s
; 18% a → -s; …
2d
Banda #b
Calcc
Expd
Wave Functione =
----
1
4
5
9
---- ---- ----
---- ---- Ground State
12% a → -s; …
20% s → -s; 13% s → LUMO+2; …
20.1 497 (0.12) 16.1 621 73% s → -a
21.1 474 (0.02) 18.5 541 62% a → -a
26.9 373 (0.59) 23.0 435 36% s → LUMO+2; 30% a→ -a
;
Q
;
;
25% s → -s; …
B
10 27.4 366 (0.75) 24.4 409 43% s → LUMO+2; 27% a → -s
; 18% a → -s; …
a − Band assignment described in the text. b − The number of the state assigned in terms of ascending energy within the TD-DFT
calculation. c − Calculated band energies (103.cm−1), wavelengths (nm) and oscillator strengths in parentheses (f). d − Observed
energies (103.cm−1) and wavelengths (nm) in Figure 2. e − The wave funcꢁons based on the eigenvectors predicted by TD-DFT.
One-electron transitions associated with the four frontier
-a and -s nomenclature[S2] for the four frontier
-MOs is used to facilitate comparison of the transition of porphyrinoids with
differing symmetries.
π a,
-MOs of Gouterman’s 4-orbital model[S1] are highlighted in bold. Michl’s
s,
π
29