A High-Energy Charge-Separated State of 1.70 eV from a High-Potential Donor–Acceptor Dyad: A Catalyst for Energy-Demanding Photochemical Reactions

Article abstract of DOI:10.1002/anie.201606112

A high potential donor–acceptor dyad composed of zinc porphyrin bearing three meso-pentafluorophenyl substituents covalently linked to C₆₀, as a novel dyad capable of generating charge-separated states of high energy (potential) has been develo

Full text of DOI:10.1002/anie.201606112

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201606112
German Edition: DOI: 10.1002/ange.201606112
Charge-Separated States
A High-Energy Charge-Separated State of 1.70 eV from a High-
Potential Donor–Acceptor Dyad: A Catalyst for Energy-Demanding
Photochemical Reactions
Gary N. Lim, Christopher O. Obondi, and Francis D’Souza*
Abstract: A high potential donor–acceptor dyad composed of
zinc porphyrin bearing three meso-pentafluorophenyl sub-
stituents covalently linked to C60, as a novel dyad capable of
generating charge-separated states of high energy (potential)
has been developed. The calculated energy of the charge-
separated state was found to be 1.70 eV, the highest reported for
a covalently linked porphyrin–fullerene dyad. Intramolecular
photoinduced electron transfer leading to charge-separated
states of appreciable lifetimes in polar and nonpolar solvents
has been established from studies involving femto- to nano-
second transient absorption techniques. The high energy stored
in the form of charge-separated states along with its persistence
of about 50–60 ns makes this dyad a potential electron-
transporting catalyst to carry out energy-demanding photo-
chemical reactions. This type of high-energy harvesting dyad is
expected to open new research in the areas of artificial
photosynthesis especially producing energy (potential)
demanding light-to-fuel products.
modular donor–acceptor systems, long-lived charge-sepa-
rated states have been achieved, however, at the cost of
lowering the energy of the charge-separated states due to the
energy loss encountered during the processes of sequential
electron-transfer events.[1–3] Such charge-separated states
although long-living may not carry enough energy (potential)
to perform fuel-producing chemical reactions, for example,
oxidation of water to produce protons. Consequently, there is
a great need for donor–acceptor systems capable of generat-
ing high-energy charge-separated states with appreciable
lifetimes.
Herein, we have synthesized a donor–acceptor dyad using
a difficult to oxidize electron donor, that is, zinc porphyrin
having pentafluorophenyl substituents and fullerene, C60 as
the acceptor (Figure 1). Fullerene owing to its favorable
A
rtificial photosynthesis holds great promise to meet the
growing energy needs by providing renewable solar energy
and fuels.[1–7] Elegantly designed multi-modular donor—
acceptor systems capable of producing charge-separated
states upon photoexcitation are key in building energy-
harvesting devices. The stored energy in the charge-separated
species (electrochemical potential) could be used to produce
solar fuels in a catalytic fashion. This process is analogous to
natural photosynthesis in which the chemical energy pro-
duced via trans-membrane charge separation via a multistep
electron-transfer process is converted into other forms of
biologically useful energy stored in the chemical bonds of the
products.[8] Two factors mandate the applicability of the
charge-separated states for their catalytic applications, these
are, their persistence prior to the relaxation to the ground
state (lifetime of charge-separated states) and the amount of
stored energy as electrochemical potential. Often, using the
concept of electron/hole migration in well-designed multi-
Figure 1. Structure of the high potential zinc porphyrin–fullerene dyad
developed to generate high-energy charge-separated states.
reduction potential and low reorganization-energy demand is
a preferred choice of an electron acceptor.[9] As shown herein,
owing to the presence of fluorine substituents, zinc porphyrin
((F15P)Zn) oxidation becomes harder by 430 mV compared to
the traditionally used zinc porphyrin,[10] however, without
drastically compromising its spectral (absorption and emis-
sion) properties. The constructed energy level diagram shows
[*] G. N. Lim, C. O. Obondi, Prof. Dr. F. D’Souza
Department of Chemistry
1
that photoinduced electron transfer from the (F15P)Zn* to
University of North Texas
1155 Union Circle, #305070, Denton, TX 76203-5017 (USA)
E-mail: Francis.DSouza@UNT.edu
fullerene is indeed possible to yield high energy charge-
separated states. The calculated energy of the charge-
separated state was as high as 1.70 eV enough to drive most
of the catalytic processes (for example, water oxidation
potential is 1.23 V). Evidence for the formation of such high-
energy charge-separated state and kinetics of forward and
reverse charge-separation processes have been secured from
studies involving transient absorption studies ranging from
femto- to nanosecond timescales.
Supporting information (synthetic details and scheme, general
experimental section, spectroelectrochemical data on (F15P)Zn in
benzonitrile, femtosecond and nanosecond transient spectra of the
control compounds, 1H and 13C NMR and MALDI-mass spectra of
the dyad) and the ORCID identification number(s) for the author(s)
of this article can be found under http://dx.doi.org/10.1002/anie.
201606112.
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Synthesis of the (F15P)Zn-C60 was accom-
plished according to Scheme S1 in the Support-
ing Information. This involved first synthesis of
meso-tris(pentafluorophenyl)-(4-hydroxy-
phenyl)-porphyrin. This compound was subse-
quently reacted with 4-carboxy benzaldehyde
to obtain meso-tris(pentafluorophenyl)-(4’-for-
mylphenyl benzoate)porphyrin. Reaction of
formyl functionalized porphyrin with C60 and
sarcosine according to Pratoꢀs reaction yielded
the free-base porphyrin (F15P)–C60 dyad. The
free-base porphyrin was subsequently metal-
lated using zinc acetate to obtain (F15P)Zn–C60
dyad. The purity of the compound was checked
by running thin-layer chromatography, and the
structural identity was established from 1H and
13C NMR spectroscopy and MALDI-mass spec-
trometry techniques. The dyad was stored in
dark prior to performing photochemical stud-
ies.
Figure 2a,b show the absorption and fluo-
rescence spectra of the dyad along with the
control compounds, (F15P)Zn and fulleropyrro-
lidine, in benzonitrile. The absorption spectral
pattern of porphyrin was typical of that of
metalloporphyrin, however, the peak maxima
were red-shifted by 4–5 nm compared with
tetraphenylporphyrin due to the presence of
Figure 2. a) Optical absorbance and b) steady-state fluorescence spectra (lex =552 nm)
of the indicated compounds in benzonitrile at room temperature. c) Time-resolved
emission spectra of indicated compounds monitored at porphyrin emission wavelength.
Control=(F15P)Zn, prompt=light scatter. The decay curve fits are shown in solid lines.
d) Phosphorescence spectrum of (F15P)Zn control in methyl cyclohexane containing 5%
CH3I at liquid-nitrogen temperature.
3
electron-withdrawing fluoro substituents on the phenyl rings.
Covalent attachment of C60 had virtually no effect, meaning
absence of appreciable intramolecular interactions between
them. The fluorescence spectrum of the control (F15P)Zn
revealed two bands at l = 600 and 650 nm which were
quenched by 46% in benzonitrile and 38% in toluene for
the (F15P)Zn–C60 dyad suggesting the occurrence of excited
state events in the dyad. Scanning the wavelength into the
1C60* emission range of 720 nm revealed no emission of C60
suggesting absence of singlet–singlet energy transfer from the
excited 1(F15P)Zn* to C60. This is conceivable since full-
eropyrrolidine virtually had no absorbance in the 575–675 nm
1.64 eV. This value compares with a ET value for C60* of
1.55 eV.
The differential pulse voltammogram (DPV) of the dyad
in benzonitrile is shown in Figure 3. Well defined redox waves
corresponding to both oxidation and reduction were
observed. The first two oxidation processes corresponding
+
to the (F15P)ZnC and (F15P)Zn2+ formation were located at
0.71 and 0.95 V vs. Fc/Fc+, respectively, while the first
reduction corresponding to the (F15P)ZnCꢀ formation was
located at ꢀ1.77 V vs. Fc/Fc+. The fulleropyrrolidine in the
dyad revealed the first three reductions at ꢀ1.01, ꢀ1.40, and
ꢀ1.97 V vs. Fc/Fc+. There was no appreciable shift in the
redox potentials of the dyad when compared to that of the
corresponding control compounds suggesting lack of ground
state interactions between the entities. Importantly, the
1
range where (F15P)Zn* fluoresce.
To ascertain that the quenching is due to processes
originated from the singlet excited porphyrin and not static
(lowering lifetime due to ground state complex formation),
fluorescence lifetimes were measured for the control and the
dyad. The decay profiles could be fitted satisfactorily to
a monoexponential decay function (c2 < 1.2) in all of the cases
(see Figure 2c for decay curves and fits). The lifetime of the
(F15P)Zn control was found to be 1.67 and 1.83 ns, respec-
tively, in benzonitrile and toluene. For the (F15P)Zn–C60 dyad,
these lifetimes were found to be 0.76 and 0.82 ns, respectively.
The lowering of the lifetime of 1(F15P)Zn* in the dyad shows
the occurrence of excited state events in both solvents.[11]
It was also important to evaluate the triplet energy level of
(F15P)Zn. The phosphorescence spectrum of (F15P)Zn
recorded in methyl cyclohexane containing 5% CH3I at
liquid nitrogen temperature revealed a peak at 758 nm
(Figure 2d). This resulted in ET value for 3[(F15P)Zn]* of
Figure 3. DPVs of the (F15P)Zn–C60 dyad in benzonitrile, 0.1m (n-
Bu4N)ClO4. Scan rate=5 mVsꢀ1, pulse width=0.25 s, pulse
height=0.025 V. The oxidation wave of ferrocene (Fc/Fc+) used as the
internal reference is shown with an asterisk.
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430 mV anodic shift of the first oxidation of (F15P)Zn
in benzonitrile at an applied potential of 0.80 V vs. Fc/Fc+
corresponding to its first oxidation process. As shown in
compared to (TPP)Zn (TPP = tetraphenylporphyrin, E1/2
=
0.28 V vs. Fc/Fc+)[10] is noteworthy.
Figure S1, during this process, both Soret and visible bands
located at l = 425 and 555 nm revealed diminished intensity
accompanied by new peaks at l = 780 and 905 nm. Isosbestic
points at l = 398, 442, 540, and 575 nm were observed.
Appearance of transient peaks at these wavelengths would
serve as a direct proof for the occurrence of charge separation
in the dyad.
Using the spectral and electrochemical data, free-energy
change associated for charge separation (DGCS) and charge
recombination (DGCR) were calculated according to Rehm
and Weller approach.[12,13] From these calculations, DGCS and
DGCR values of ꢀ0.34 and ꢀ1.70, respectively, in bezonitrile
were obtained. Figure 4 shows the energy-level diagram
Femtosecond differential transient absorption spectro-
scopic method was utilized to secure evidence for the
occurrence of photoinduced charge separation from the
excited singlet state of (F15P)Zn in the high potential dyad.
First, the (F15P)Zn control compound was recorded in
benzonitrile and toluene and the data is shown in Figure S2.
The transient spectra of (F15P)Zn in benzonitrile revealed
instantaneously formed 1(F15P)Zn* with positive peaks at 459,
581, 702 and 1290 nm and negative peaks at 555 and 627 nm.
The 555 nm peak was due to ground state depletion while the
627 nm peak had contributions from both ground state
depletion and stimulated emission. Decay/recovery of the
positive/negative peaks resulted in populating the 3(F15P)Zn*
via intersystem crossing with the triplet peaks located at 463,
671 and 848 nm. Similar spectral features were also observed
in toluene. The decay profile of the 1290 nm peak, shown as
Figure 4. Energy-level diagram depicting the different photochemical
events occurring in the (F15P)Zn–C60 dyad upon photoexcitation
leading to the formation of high-energy charge-separated state. Abbre-
viations: CS=charge separation, CR=charge recombination, ISC=in-
tersystem crossing, T=triplet emission.
constructed to visualize the different photochemical events.
At the excitation wavelength of 400 nm, (F15P)Zn in the dyad
1
is primarily being excited. The (F15P)Zn*–C60 thus formed
could undergo energy transfer to produce (F15P)Zn–1C60*
(minor process), or intersystem crossing to produce
3(F15P)Zn*–C60 or electron transfer to yield the high-energy
+
(F15P)ZnC –C60Cꢀ charge-separated state. Importantly, the
energy of the charge-separated state in benzonitrile is about
1.70 V, the highest ever for a zinc porphyrin–C60 radical ion
pair. The recombination mechanism of these possible photo-
products also deserves special mention. The (F15P)ZnC+–C60Cꢀ
charge-separated state could populate the energetically low
3
3
lying (F15P)Zn* or C60* states within the dyad prior to its
3
relaxation to the ground state. Interestingly, the (F15P)Zn*–
C60 formed either via the intersystem crossing from
1(F15P)Zn* or via charge recombination could undergo
3
triplet–triplet energy transfer to populate C60* within the
dyad. Femtosecond transient spectral studies were performed
to secure evidence for these processes and also to obtain their
kinetic information.
One of the key evidences for the occurrence of charge
separation in a donor–acceptor dyad is to detect the transient
spectral features corresponding to the products of charge-
separated state, that is, (F15P)ZnC+ and C60Cꢀ species. The C60Cꢀ
is known for its absorbance in the near-IR region around
Figure 5. Femtosecond differential transient absorption spectra
(400 nm excitation of 100 fs pulses) of (F15P)Zn–C60 dyad in Ar-
saturated a) benzonitrile and b) toluene at the indicated delay times.
Insets show time profile of the 1290 nm peak corresponding singlet
excited state of (F15P)Zn control (black line), 1290 nm peak of
(F15P)Zn–C60 (red), and the 1020 nm peak corresponding to
C60Cꢀ (blue).
+
1020 nm.[1,2] To seek spectral signature bands of (F15P)ZnC ,
spectroelectrochemical studies were performed on (F15P)Zn
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an inset, agreed well with the expected singlet
lifetime of the (F15P)Zn.
Figure 5 shows the differential transient
absorption spectra of the (F15P)Zn–C60 dyad in
the investigated solvents. The decay of the
instantaneously formed 1(F15P)Zn* was much
faster (see Figure 5 insets for decay profiles of
the 1290 nm peak of (F15P)Zn (black) and
(F15P)Zn-C60 (red)). However, the 1(F15P)Zn*
3
instead of populating the (F15P)Zn* revealed
development of transient peaks corresponding
+
to the (F15P)ZnC –C60Cꢀ charge-separated state.
+
That is, broad spectral features of (F15P)ZnC at
790 and 905 nm, and a peak at 1020 nm corre-
sponding to C60Cꢀ (see spectra recorded at 25 ps
delay time, Figure 5) thus confirming the occur-
rence of photoinduced charge separation. The
[14]
rate constant for charge separation, kCS was
evaluated by monitoring decay of the 1290 nm
peak as this peak is sufficiently away from other
transient peaks.
The kCS thus calculated was found to be 5.7 ꢁ
108 sꢀ1 in benzonitrile and 1.7 ꢁ 108 sꢀ1 in tolu-
ene. The overall kCS is slower compared to the
traditionally
used
ZnP–C60
(kCS
ꢁ 109ꢀ1010 sꢀ1).[1–3] The quantum yield of
charge separation, Ff[15] was also calculated,
and these values were found to be 40% in
benzonitrile and 20% in toluene. These values
are reasonable considering smaller free-energy
change for charge separation and solvent polar-
ity effects. For calculating the rate constant for
Figure 6. Nanosecond differential transient absorption spectra (425 nm of 8 ns pulses)
of (F15P)Zn–C60 dyad in Ar-saturated a) benzonitrile and b) toluene at the indicated
delay times. Insets show the expanded region of 950–1050 nm revealing the signature
peak of C60Cꢀ. Right hand panel shows the time profile of the 840 nm peak.
charge recombination, kCR, the decay of C60Cꢀ peak at 1020 nm
was monitored. However, as seen from Figure 5 inset (blue
trace), the decay lasted beyond the monitoring time window
of our femtosecond transient spectrometer in both solvents
and thus demanded complimentary nanosecond transient
measurements.
corresponding to the charge-separated states (see spectrum
recorded at 35 ns delay time in Figure 6b). The weak signal
strength of C60Cꢀ is conceivable since the quantum yield for
charge separation is only 40% and 20% in benzonitrile and
toluene, respectively, and by the time the first nanosecond
transient spectrum is recorded (ca. 30 ns), most of the radical
ion-pair signal originated from the singlet excited (F15P)Zn is
depleted due to charge recombination. Under these condi-
tions, it is safer to say that the charge-separated state persists
for about 50–60 ns, adequate time to deploy the system for
high energy demanding photocatalytic reactions of appropri-
ate energy states. The decay rate constant, kT of the populated
3(F15P)Zn* (see Figure 6 right hand panel for the decay
curves) was found to be 3.1 ꢁ 104 sꢀ1 in benzonitrile and 4.0 ꢁ
104 sꢀ1 in toluene.
In summary, the high potential donor–acceptor dyad
resulted in high-energy charge-separated state carrying
potential of a remarkable 1.70 eV during intramolecular
photoinduced electron transfer, the highest for a zinc por-
phyrin–fullerene dyad reported to date. Coupled with this,
and the persistence of the charge-separated state to 50–60 ns
makes this dyad an potential photocatalyst to carryout high-
energy demanding reactions including light-to-fuel conver-
sion processes. Currently, we are looking into such photo-
catalytic applications.
To evaluate the lifetime of the final charge-separated
state, nanosecond transient spectral measurements were
performed. As pointed out earlier, the energy of the charge-
separated state in the present study is above that of
3
3(F15P)Zn* (1.64 eV) and C60* (1.55 eV) levels. Under these
conditions, the process of charge recombination could pop-
ulate either one of these states. The transient spectra of
3(F15P)Zn* (see Figure S3) revealed peaks at 466, 732 and
835 nm in benzonitrile and at 462, 718 and 835 nm in toluene.
The decay rate constant was found to be kT = 3.5 ꢁ 103 sꢀ1 in
benzonitrile and 1.3 ꢁ 104 sꢀ1 in toluene. Triplet fulleropyrro-
lidine is known to exhibit peaks at 700 and 835(sh) nm.[2]
Interestingly, the nanosecond transient spectra of the dyad in
3
benzonitrile resembled largely that of (F15P)Zn*, however,
+
with signature peaks corresponding to (F15P)ZnC and C60Cꢀ
species (see the spectrum recorded at 28 ns in Figure 6a).
These peaks were not present for 3(F15P)Zn* as seen in
Figure S3a. The decay of the radical ion peaks populated the
3(F15P)Zn*, as witnessed by an increase of the triplet peaks.
By 70 ns, the peak at 1020 nm of C60Cꢀ was completely
vanished. The spectra recorded in toluene also revealed bands
4
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Molecular Level Artificial Photosynthetic Materials, Wiley, New
York, 1997.
Acknowledgements
[9] a) Q. Xie, E. Perz-Cordero, L. Echegoyen, J. Am. Chem. Soc.
1992, 114, 3978 – 3980; b) H. Imahori, K. Tamaki, D. M. Guldi, C.
Luo, M. Fujitsuka, O. Ito, Y. Sakata, S. Fukuzumi, J. Am. Chem.
Soc. 2001, 123, 2607 – 2617.
[10] F. DꢀSouza, G. R. Deviprasad, M. E. Zandler, V. T. Hoang, A.
Klykov, M. VanStipdonk, A. Perera, M. E. El-Khouly, M.
Fujitsuka, O. Ito, J. Phys. Chem. A 2002, 106, 3243 – 3252.
[11] J. R. Lakowicz, Principles of Fluorescence Spectroscopy, 3rd ed.,
Springer, Singapore, 2006.
This work was supported by the National Science Foundation
(Grant No. 1401188 to F.D.).
Keywords: advanced photocatalyst · donor–acceptor dyad ·
fluorinated porphyrin · fullerene · charge-separated states
[12] D. Rehm, A. Weller, Isr. J. Chem. 1970, 8, 259 – 271.
[13] The free-energy change for charge separation (DGCS) from the
singlet excited state 1(F15P)Zn* within the donor–acceptor
system is calculated using spectroscopic, computational, and
[1] a) S. Fukuzumi, K. Ohkubo, T. Suenobu, Acc. Chem. Res. 2014,
47, 1455 – 1464; b) S. Fukuzumi, K. Ohkubo, F. DꢀSouza, J. L.
Sessler, Chem. Commun. 2012, 48, 9801 – 9815.
[2] a) F. DꢀSouza, O. Ito, Chem. Soc. Rev. 2012, 41, 86 – 96, b) C. B.
KC, F. DꢀSouza, Coord. Chem. Rev. 2016, 322, 104 – 141; c) M.
El-Khouly, S. Fukuzumi, F. DꢀSouza, ChemPhysChem 2014, 15,
30 – 47.
electrochemical
data
following
(1)
(2)
Equations (1)–(3).
ꢀDGCR = EoxꢀEred + DGS
ꢀDGCS = DE0,0ꢀ(ꢀDGCR
)
[3] a) H. Imahori, T. Umeyama, S. Ito, Acc. Chem. Res. 2009, 42,
1809 – 1818; b) T. Hasobe, Phys. Chem. Chem. Phys. 2010, 12,
44 – 57.
[4] a) N. S. Lewis, D. G. Nocera, Proc. Natl. Acad. Sci. USA 2006,
103, 15729 – 15735; b) P. V. Kamat, J. Phys. Chem. C 2007, 111,
2834 – 2860.
[5] a) M. R. Wasielewski, Acc. Chem. Res. 2009, 42, 1910 – 1921;
b) D. Gust, T. A. Moore, A. L. Moore, Acc. Chem. Res. 2009, 42,
1890 – 1898.
[6] a) V. Balzani, A Credi, M. Venturi, ChemSusChem 2008, 1, 26 –
58; b) G. Ulrich, R. Ziessel, A. Harriman, Angew. Chem. Int. Ed.
2008, 47, 1184 – 1201; Angew. Chem. 2008, 120, 1202 – 1219; c) E.
Schwartz, S. Le Gac, J. J. L. M. Cornelissen, R. J. M. Nolte, A. E.
Rowan, Chem. Soc. Rev. 2010, 39, 1576 – 1599.
[7] a) D. M. Guldi, A. Rahman, V. Sgobba, C. Ehli, Chem. Soc. Rev.
2006, 35, 471 – 487; b) J. N. Clifford, G. Accorsi, F. Cardinali, J. F.
Nierengarten, N. Armaroli, C. R. Chem. 2006, 9, 1005 – 1013;
c) N. Martin, L. Sanchez, M. A. Herranz, B. Illesca, D. M. Guldi,
Acc. Chem. Res. 2007, 40, 1015 – 1024; d) G. Bottari, G.
de la Torre, D. M. Guldi, T. Torres, Chem. Rev. 2010, 110,
6768 – 6816; e) D. M. Guldi, V. Sgobba, Chem. Commun. 2011,
47, 606 – 610; f) D. Gonzꢂlez-Rodrꢃguez, E. Carbonell, D. M.
Guldi, T. Torres, Angew. Chem. Int. Ed. 2009, 48, 8032 – 8036;
Angew. Chem. 2009, 121, 8176 – 8180.
where DE0,0 and DGCS correspond to the energy of excited
singlet state and electrostatic energy, respectively. The Eox and
Ered represent the oxidation potential of the electron donor,
(F15P)Zn and the reduction potential of the electron acceptors,
C60), respectively. The term DGs refers to the static Coulombic
energy, calculated by using the “dielectric continuum model”
according to Equation (3):
hꢁ
ꢂ
i
ꢀ
e2
1
1
1
1
DGs ¼
=
þ =
Dð = Þ ꢀ
(3)
eR
R
CCeR
4pe0
2Rþ
2Rꢀ
The symbols e0, and eR represent vacuum permittivity and
dielectric constant of the solvent used for photochemical and
electrochemical studies, respectively. RCC is the center-to-center
distance between donor and acceptor entities. The symbols R+
and Rꢀ refer to radii of the cation and anion species, respectively.
The calculated DGS was found to be 0.07 eV for the present
donor–acceptor system.
[14] kCS = 1/t(F15P)Zn-C60ꢀ1/t(F15P)Zn), where t(F15P)Zn-C60 and t(F15P)Zn
)
refer to decay time constant of the dyad and control, respec-
tively.
[15] Ff (= [1/t(F15P)Zn-C60ꢀ1/t(F15P)Zn]/1/t(F15P)Zn-C60), for abbreviations,
see Ref. [14].
[8] a) J. S. Connolly, Photochemical Conversion and Storage of Solar
Energy, Academic Press, New York, 1981; b) G. J. Meyer,
Received: June 23, 2016
Published online: && &&, &&&&
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Communications
Charge-Separated States
Keep ’em separated: A donor–acceptor
dyad composed of a high oxidation
potential zinc porphyrin covalently linked
to C60 has been synthesized and shown to
generate a high-energy charge-separated
state on the order of 1.70 eV and a life-
time in the range of 50–60 ns during
photoinduced electron transfer, which is
sufficient to carry out many energy
(potential) demanding photocatalytic
reactions.
G. N. Lim, C. O. Obondi,
F. D’Souza*
&&&& — &&&&
A High-Energy Charge-Separated State of
1.70 eV from a High-Potential Donor–
Acceptor Dyad: A Catalyst for Energy-
Demanding Photochemical Reactions
6
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