Encapsulation of TCNQ and the acridinium ion within a bisporphyrin cavity: Synthesis, structure, and photophysical and HOMO-LUMO-gap-mediated electron-transfer properties

Article abstract of DOI:10.1002/chem.201200034

The encapsulation of tetracyanoquinodimethane (TCNQ) and fluorescent probe acridinium ions (AcH⁺) by diethylpyrrole-bridged bisporphyrin (H ₄DEP) was used to investigate the structural and spectroscopic changes within the bisporphyrin cavity upon substrate binding. X-ray diffraction studies of the bisporphyrin host (H₄DEP) and the encapsulated host-guest complexes (H₄DEP·TCNQ and [H₄DEP· AcH]ClO₄) are reported. Negative and positive shifts of the reduction and oxidation potentials, respectively, indicated that it was difficult to reduce/oxidize the encapsulated complexes. The emission intensities of bisporphyrin, upon excitation at 560 nm, were quenched by about 65 % and 95 % in H₄DEP·TCNQ and [H₄DEP·AcH]ClO₄, respectively, owing to photoinduced electron transfer from the excited state of the bisporphyrin to TCNQ/AcH⁺; this result was also supported by DFT calculations. Moreover, the fluorescence intensity of encapsulated AcH ⁺ (excited at 340 nm) was also remarkably quenched compared to the free ions, owing to photoinduced singlet-to-singlet energy transfer from AcH⁺ to bisporphyrin. Thus, AcH⁺ acted as both an acceptor and a donor, depending on which part of the chromophore was excited in the host-guest complex. The electrochemically evaluated HOMO-LUMO gap was 0.71 and 1.42 eV in H₄DEP·TCNQ and [H₄DEP·AcH] ClO₄, respectively, whilst the gap was 2.12 eV in H₄DEP. The extremely low HOMO-LUMO gap in H₄DEP·TCNQ led to facile electron transfer from the host to the guest, which was manifested in the lowering of the CN stretching frequency (in the solid state) in the IR spectra, a strong radical signal in the EPR spectra at 77 K, and also the presence of low-energy bands in the UV/Vis spectra (in the solution phase). Such an efficient transfer was only possible when the donor and acceptor moieties were in close proximity to one another. Copyright

Full text of DOI:10.1002/chem.201200034

FULL PAPER
DOI: 10.1002/chem.201200034
Encapsulation of TCNQ and the Acridinium Ion within a Bisporphyrin
Cavity: Synthesis, Structure, and Photophysical and HOMO–LUMO-Gap-
Mediated Electron-Transfer Properties
Arvind Chaudhary and Sankar Prasad Rath*[a]
Abstract: The encapsulation of tetra-
cyanoquinodimethane (TCNQ) and
fluorescent probe acridinium ions
(AcH+) by diethylpyrrole-bridged bis-
porphyrin (H4DEP) was used to inves-
tigate the structural and spectroscopic
changes within the bisporphyrin cavity
upon substrate binding. X-ray diffrac-
tion studies of the bisporphyrin host
(H4DEP) and the encapsulated host–
guest complexes (H4DEP·TCNQ and
[H4DEP·AcH]ClO4) are reported. Neg-
ative and positive shifts of the reduc-
tion and oxidation potentials, respec-
tively, indicated that it was difficult to
reduce/oxidize the encapsulated com-
plexes. The emission intensities of bis-
porphyrin, upon excitation at 560 nm,
were quenched by about 65% and
[H4DEP·AcH]ClO4, respectively, owing
to photoinduced electron transfer from
the excited state of the bisporphyrin to
TCNQ/AcH+; this result was also sup-
ported by DFT calculations. Moreover,
the fluorescence intensity of encapsu-
lated AcH+ (excited at 340 nm) was
also remarkably quenched compared to
the free ions, owing to photoinduced
singlet-to-singlet energy transfer from
AcH+ to bisporphyrin. Thus, AcH+
acted as both an acceptor and a donor,
depending on which part of the chro-
mophore was excited in the host–guest
complex. The electrochemically evalu-
ated HOMO–LUMO gap was 0.71 and
1.42 eV
in
H4DEP·TCNQ
and
[H4DEP·AcH]ClO4, respectively, whilst
the gap was 2.12 eV in H4DEP. The ex-
tremely low HOMO–LUMO gap in
H4DEP·TCNQ led to facile electron
transfer from the host to the guest,
which was manifested in the lowering
of the CN stretching frequency (in the
solid state) in the IR spectra, a strong
radical signal in the EPR spectra at
77 K, and also the presence of low-
energy bands in the UV/Vis spectra (in
the solution phase). Such an efficient
transfer was only possible when the
donor and acceptor moieties were in
close proximity to one another.
Keywords: donor–acceptor
sys-
tems · electron transfer · host–guest
systems · porphyrins · structure elu-
cidation
95%
in
H4DEP·TCNQ
and
Introduction
the binding and activation of a variety of substrates.[4–14] The
cooperative interaction that was derived from the two por-
phyrins plays a crucial role in these functions. The type of
linker that is used to connect the two porphyrin units influ-
ences the electronic communication in a bisporphyrin and
thus a variety of bisporphyrin arrays have been explored.
Efficient molecular recognition of the bisporphyrin host to-
wards guest molecules or ions requires high structural- and
binding-site complementarity between the host and the
guest. Covalently linked bisporphyrin architectures act as
a good receptor that can accommodate both neutral as well
as electron-rich/-deficient guests in its clefts through changes
in their photophysical properties.
Simple synthetic receptors with molecular pockets or cavi-
ties can act as model compounds for many complicated bio-
logical systems, such as protein folding, the molecular recog-
nition of substrates by enzymes, and the formation of mem-
branes. The development of synthetic hosts that are capable
of binding substrates that mimic various chemical processes
in nature has long been an important goal.[1–3] Encapsulation
of a molecular container within the inner core can typically
accelerate a reaction, alter the course of a reaction in limit-
ed quarters, perturb the equilibrium, contort conformations,
and also sometime stabilize reactive reagents or intermedi-
ates.[1–3]
Herein, we report the efficient encapsulation of tetracya-
noquinodimethane (TCNQ)/acridinium ions (AcH+) into di-
ethylpyrrole-bridged bisporphyrin (H4DEP) through strong
Two porphyrins that are linked in a face-to-face arrange-
ment through rigid/flexible linkers form molecular clefts for
ꢀ
p p interactions to form host–guest complexes that can pro-
vide information about the chemical environment in the in-
terior of the host–guest supramolecular assembly. However,
interactions of the porphyrin with TCNQ[15,16] or with AcH+
have been reported previously.[17] TCNQ is a well-known
multiredox-active neutral organic molecule that can act as
a prominent acceptor and it is also considered to be “non-
innocent” in coordination chemistry because of its very low-
[a] A. Chaudhary, Dr. S. P. Rath
Department of Chemistry
Indian Institute of Technology Kanpur
Kanpur-208016 (India)
Fax: (+91)512-259-7436
E-mail: sprath@iitk.ac.in
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201200034.
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lying p* orbital.[15,16,18] On the other hand, AcH+ is known
to be suitable for fast photoinduced electron transfer but ex-
tremely slow back electron transfer.[17,19] Moreover, TCNQ
is a non-fluorescent molecule whilst AcH+ shows high fluo-
rescent activity. Complexation studies between H4DEP and
TCNQ/AcH+ have been carried out in both the solid and so-
lution phases. Theoretical studies based on DFT calculation
have also been performed for improving the understanding
of the sandwich architecture.
X-ray diffraction studies of the bisporphyrin host and the
encapsulated host–guest complexes enabled us to investigate
the changes in structure, properties, and conformation upon
substrate binding. The stability of the host–guest complexes
also allowed for their isolation as analytically pure solids in
good yields. Crystallographic evidence of specific host–guest
interactions in the literature has been scarce and detailed
knowledge of the solid- and solution-phase interactions
would offer substantial insight towards the rational control
of guest selectivity and also the reactivity therein. We have
recently reported the formation of host–guest complex be-
tween dizinc(II) bisporphyrin (host) and fluorescent probe
pyrene (guest) in which significant photoinduced singlet–sin-
glet energy transfer from the excited state of pyrene to por-
phyrin took place.[13]
Figure 1. UV/Vis spectra (at 298 K) of H4DEP (1) in CH2Cl2 upon addi-
tion of various amounts of A) TCNQ and B) AcH+ in air; arrows indi-
cate the increasing or decreasing trend in intensity. C) Absorption spec-
trum (curved line, left axis) in CH2Cl2 and oscillator strengths (vertical
bar, right axis) from TD-DFT calculations for H4DEP·TCNQ (2).
Results and Discussion
Diethylpyrrole-bridged bisporphyrin (H4DEP, 1) was synthe-
sized according to a literature procedure[13,20] and character-
ized by spectroscopy and MS (ESI; see the Supporting In-
formation, Figure S1). The UV/Vis spectrum of compound
1 showed an intense Soret band at 407 nm and four Q bands
at 511, 545, 583, and 630 nm. The complexation between re-
ceptor 1 and the guest was investigated in CH2Cl2 by UV/
Vis/NIR and ESR spectroscopy. The addition of 1 equiva-
lent of TCNQ to a solution of compound 1 in CH2Cl2 result-
ed in the appearance of two charge transfer (CT) absorption
bands, centered at lmax =769 and 851 nm, owing to the for-
mation of host–guest sandwich p-complex H4DEP·TCNQ
(2), which was isolated as a solid in good yield and structur-
ally characterized. However, TCNQ alone did not give any
notable absorption at lꢁ500 nm, whilst receptor 1 also did
not give any notable absorption at lꢁ650 nm. The progres-
sive emergence of low-energy bands between 650–900 nm
(Figure 1A) were due to the formation of the porphyrin
cation radical and the [TCNQ]·ꢀ anion radical in solution
(see below), as reported previously.[16,21] An EPR spectrum
of the isolated complex (in CH2Cl2) showed a radical signal,
centered at g=2.005, which was in the characteristic region
for both a porphyrin radical cation and a TCNQ radical
anion.[16,22] Under UV light, the red solution of compound
1 became green owing to the formation of host–guest com-
plex 2.
absorption bands also appeared between 650–900 nm, al-
though no radical signal was detected in the EPR spectrum
at 77 K. These results showed some CT between the bispor-
phyrin and AcH+ in solution. Upon encapsulation of the
highly fluorescent AcH+ within the bisporphyrin cleft in
complex 3, the complex became non-fluorescent. The com-
plex was also isolated and structurally characterized in the
solid state. Figure 1A and Figure 1B show the changes in
the UV/Vis spectra of H4DEP in CH2Cl2 at room tempera-
ture in air upon progressive addition of TCNQ and AcH+,
respectively. Scheme 1 shows the structures of complexes 1–
3 and their abbreviations; the insets show the respective
colors of the samples in CH2Cl2 under UV illumination at
room temperature.
The UV/Vis absorption spectrum of supramolecular com-
plex 2 was simulated on the basis of the computed vertical
excitation energies by using time-dependent DFT (TD-
DFT);[23] all of the spectroscopic measurements were carried
out in CH2Cl2. The excitation energies and oscillator
strengths were obtained from TD-DFT calculations, which
were also in close agreement with experimental data (Fig-
ure 1C). Under identical experimental conditions, the Soret
and Q bands of compound 2 are in almost the same posi-
tions as those for H4DEP (1); the most-pronounced effect
was observed in the low-energy bands at 769 and 851 nm,
owing to interactions between H4DEP (1) and TCNQ. How-
A similar observation was obtained when an ionic guest,
such as AcH+, was used instead of TCNQ, to form host–
guest complex [H4DEP·AcH]ClO4 (3). Broad low-energy
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Encapsulation within a Bisporphyrin Cavity
FULL PAPER
computed frontier MOs of
these transitions are shown in
the Supporting Information,
Figure S2.
Figure 2 shows the Jobꢁs con-
tinuous-variation plot to deter-
mine the stoichiometry of the
complex formation by using
UV/Vis spectroscopy. The bis-
porphyrin absorption band that
was used for such measure-
ments was at 509 and 512 nm
for TCNQ and AcH+, respec-
tively. The optimal formation of
complexes 2 and 3 was with
equimolar concentrations of the
porphyrin host and the guest
(i.e., 0.5 mole fractions), which
confirmed 1:1 complex forma-
tion in solution; this result was
further confirmed by MS (ESI)
1
and H NMR spectroscopy (see
below). MS of complex 2 re-
vealed a signal at m/z 1422.92,
which
was
assigned
as
[2+2H]2+. The isotopic distribu-
tion patterns of the experimen-
tal mass exactly matched with
Scheme 1. Structures of bisporphyrin 1 and its complexes with TCNQ (2) and AcH+ (3). Insets show the
colour in solution under UV light.
the
theoretical
pattern
ever, the computed simulated species showed two absorp-
tion bands in the low-energy region: one at 762 nm (oscilla-
tor strength fꢂ0.0017), which corresponded to transitions
from HOMOꢀ10 (ꢀ4.38 eV) and HOMOꢀ6 (ꢀ4.13 eV) to
the LUMO, and the other at 835 nm (oscillator strength f
ꢂ0.0032), which corresponded to the transition from
HOMOꢀ5 (ꢀ4.05 eV) to the LUMO. All of the possible
(Figure 3). X-ray structures of bisporphyrin host 1 and host–
guest complexes 2 and 3 enabled us to make a direct struc-
tural and spectroscopic comparison upon substrate binding.
For detailed synthetic procedures and spectroscopic charac-
terization of the products, see the Experimental Section.
Figure 2. Jobꢁs plot to establish the 1:1 stoichiometry of the binding be-
Figure 3. Isotopic distribution of the A) experimental and B) theoretical
tween the host molecule (1) and A) TCNQ and B) AcH+ at 298 K.
MS (ESI) of [2+2H]2+
.
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S. P. Rath and A. Chaudhary
ure 4A and selected bond distances and angles are listed in
Table 1. The porphyrin rings were almost planar with a face-
to-face arrangement but the bridging meso carbons, C20 and
C120, were considerably out of the mean porphyrin plane,
with a Cmeso···Cmeso nonbonding distance of 4.98 ꢂ, which
was presumably to minimize the nonbonding contact be-
tween the two rings. Two porphyrin macrocycles were not
perfectly co-facial, the term “slipped dimer” would be more
appropriate, whilst the mean plane-separation between two
cores was 3.66 ꢂ. Figure 4B shows the packing of the mole-
cule.
Of further interest were the intramolecular interplanar in-
teractions between the porphyrin macrocycles. Scheidt and
Lee[24] proposed a semiquantitative scheme that was based
on lateral shifts to classify the porphyrin–porphyrin interac-
tions in the solid state. Their results revealed three classes
of compounds: those with lateral shifts of about 1.5 ꢂ
(group S, small lateral shifts), those with lateral shifts of
about 3.5 ꢂ (group I, moderate lateral shifts), and those
with lateral shifts of between 4–8 ꢂ (group W). It has been
observed that compounds in groups S and I contained
ꢀ
strong p p interactions. Herein, an intramolecular mean
plane separation of 3.66 ꢂ was observed along with a lateral
shift of 2.87 ꢂ, which suggests very strong interactions be-
tween the two co-facial porphyrin cores.
Figure 4. A) H4DEP (1); thermal ellipsoids set at 50% for all non-hydro-
gen atoms (at 100 K), hydrogen atoms were omitted for clarity. B) Pack-
ing of compound 1 in the unit cell.
Crystallographic characterization of H4DEP·TCNQ (2):
Dark-brown crystals of complex 2 were grown by the slow
diffusion of MeCN into a solution of the molecule in CHCl3.
The complex crystallized in the triclinic crystal system with
the P-1 space group; a perspective view is shown in Fig-
ure 5A and selected bond distance and angles are listed in
Table 1. A TCNQ molecule was wedged into the opening
between the two rings and it was stabilized by attractive
Crystallographic characterization of H4DEP (1): Single-crys-
tals suitable for X-ray analysis were obtained by the slow
diffusion of MeCN into a solution of the complex in CHCl3.
The complex crystallized in a triclinic crystal system with
the P-1 space group; a perspective view is shown in Fig-
ꢀ
p p interactions with the rings; Figure 5B shows the molec-
Table 1. Selected bond lengths [ꢂ] and angles [8].[a]
ular packing of the complex. One TCNQ molecule entered
into the opening between two rings of H4DEP with an aver-
age TCNQ···porphyrin distance of about 3.27 ꢂ. The other
TCNQ molecule entered into the opening between two ad-
jacent molecules, as shown in the molecular packing (Fig-
ure 5B). However, both the TCNQ and porphyrin macrocy-
cles were nearly coplanar, with a small offset that facilitated
Bond length
H4DEP (1) H4DEP·TCNQ (2) [H4DEP·AcH]ClO4 (3)
Ct1–N1
Ct1–N2
Ct1–N3
Ct1–N4
Ct2–N1A
Ct2–N2A
Ct2–N3A
Ct2–N4A
2.038
2.102
2.052
2.103
2.110
2.040
2.112
2.028
2.081
2.074
2.083
2.075
2.097
2.035
2.110
2.033
2.108
2.039
2.115
2.041
2.121
2.032
2.126
2.030
ꢀ
strong p p interactions. Complexation of the TCNQ mole-
cules both internally and external to the receptor cavity re-
sulted in a continuous donor–acceptor stack in the solid
state.
Bond angle
N1-Ct1-N2
N1-Ct1-N3
N1-Ct1-N4
N2-Ct1-N4
N2-Ct1-N3
N3-Ct1-N4
N1A-Ct2-N2A 97.2
N1A-Ct2-N3A 178.3
N1A-Ct2-N4A 82.7
N2A-Ct2-N4A 178.3
N2A-Ct2-N3A 83.2
N3A-Ct2-N4A 97.0
95.8
96.7
96.5
178.5
83.8
179.7
83.3
178.4
83.3
Crystallographic characterization of [H4DEP·AcH]ClO4 (3):
Dark-brown crystals of complex 3 were grown by the slow
diffusion of MeCN into a solution of the molecule in CHCl3.
The complex crystallized in the triclinic crystal system with
the P-1 space group; a perspective view is shown in Fig-
ure 6A in which AcH+ was encapsulated within the bispor-
phyrin cleft with an average AcH+···porphyrin distance of
about 3.34 ꢂ. However, both the AcH+ and porphyrin mac-
rocycles were nearly coplanar, with a small offset that facili-
178.5
84.2
179.7
83.3
178.4
83.5
96.2
96.8
96.7
96.4
96.8
176.6
83.3
178.8
83.1
176.5
83.8
178.7
83.3
96.7
96.9
[a] The macrocyclic center (Ct) was calculated as the center point of the
porphyrinato core.
ꢀ
tated strong p p interactions with the rings. Selected distan-
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Encapsulation within a Bisporphyrin Cavity
FULL PAPER
Figure 6. A) [H4DEP·AcH]ClO4 (3); thermal ellipsoids set at 50% for all
non-hydrogen atoms (at 100 K), ClO4 counteranion and hydrogen atoms
were omitted for clarity. B) Packing of complex 3 in the unit cell.
Figure 5. A) H4DEP·TCNQ (2); thermal ellipsoids set at 50% for all
non-hydrogen atoms (at 100 K), hydrogen atoms were omitted for clarity.
B) Packing of complex 2 in the unit cell.
ces and angles are listed in Table 1 and the molecular pack-
ing of the complex is shown in Figure 6B. Table 2 shows the
crystal data and data-collection parameters of complexes
1–3.
The salient structural features
of complexes 1–3 are compared
Table 2. Crystal data and data-collection parameters.
in Table 3, along with the relat-
H4DEP (1)
H4DEP·TCNQ (2)
[H4DEP·AcH]ClO4 (3)
ed encapsulated complexes re-
T [K]
100(2)
100(2)
100(2)
ported earlier by using the
same bisporphyrin ligand. In all
cases, the rings were co-facial.
However, the average core-size
of the free ligand (1) decreased
substantially (by about 0.04 ꢂ)
upon complexation with Zn. In
host–guest complexes 2 and 3,
the two porphyrin rings were
not perfectly parallel, with in-
terplanar angles between the
two co-facial rings of 38.5 and
37.18, respectively. The intramo-
lecular Ct···Ct nonbonding dis-
tance, which was 4.63 ꢂ in com-
plex 1, increased to 6.17 and
6.21 ꢂ upon encapsulation of
TCNQ (in 2) and AcH+ (in 3),
respectively. Moreover, the
bridging Cmeso···Cmeso nonbond-
ing distance increased from
4.98 ꢂ (in 1) to about 5.28 ꢂ
formula
Mw
color
crystal system
space group
a [ꢀ]
b [ꢀ]
c [ꢀ]
a [8]
b [8]
C82H105N9
1216.75
dark brown
triclinic
P-1
11.168(5)
15.075(5)
21.711(5)
104.823(5)
101.703(5)
94.936(5)
3423 (2)
Mo Ka (0.71073)
2
1.180
0.069
1320
12454
0
857
0.998
0.0673
C106H113N17
1625.13
dark brown
triclinic
P-1
13.488(5)
17.449(5)
21.143(5)
90.278(5)
105.653(5)
108.455(5)
4523(2)
Mo Ka (0.71073)
2
1.193
0.072
1736
16442
0
1126
1.011
0.0659
C95H115ClN10O4
1496.42
dark brown
triclinic
P-1
13.813(5)
14.792(5)
21.613(5)
99.933(5)
102.965(5)
103.407(5)
4067(2)
Mo Ka (0.71073)
2
1.222
0.107
1608
14889
0
1036
1.042
0.0913
g [8]
V [ꢀ3]
radiation (l, [ꢂ])
Z
dcalcd [gcmꢀ3
]
m [mmꢀ1
(000)
]
F
A
unique reflns
no. of restraints
no. of parameters, refined
GOF on F2
R1[a] [I> 2s(I)]
R1[a] (all data)
0.1129
0.1872
0.0991
0.1846
0.1378
0.2758
wR2[b] (all data)
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P
P
2
½wðFo2 ꢀFc2
Þ
ꢃ
[a] R1 ¼ kFojꢀjFck. [b] wR2 ¼
P
P
2
jFoj
½wðFo2Þ ꢃ
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S. P. Rath and A. Chaudhary
Table 3. Selected geometric parameters of the encapsulated complexes with DEP ligand.
showed linear relationships be-
tween the nitrile stretching fre-
quencies and the negative
charges on TCNQ, whilst XRD
also revealed a similar correla-
tion between the charges and
the bond lengths. Although cor-
relation of the charges on
TCNQ based on bond length
often shows significant discrep-
ancies,[25] correlations using IR
stretching frequencies[22,25] gen-
erally provide good agreement.
Analysis of the IR spectrum of
Complex
Ct–Np D24
MPS Cm···Cm Ct···Ct
[ꢂ][a]
q
f
Lateral
Ref.
[ꢂ][a]
[ꢂ][b] [ꢂ][c] [ꢂ][d]
[8][e] [8][f]
shift [ꢂ][g]
Zn2DEP
Zn2DEP·2pyrene
H4DEP (1)
H4DEP·TCNQ (2)
[H4DEP·AcH]ClO4 (3) 2.076
2.035
2.049
2.073
2.073
0.11
0.05
0.09
0.10
0.11
3.64
6.09
3.66
6.11
6.08
4.85
5.38
4.98
5.28
5.23
4.64
6.25
4.63
6.17
6.21
4.2 38.6
2.92
0.73
[13]
[13]
this work
this work
this work
13.2
6.8
3.2 37.95 2.87
38.5
37.1
7.05 0.75
7.72 0.82
[a] Average value. [b] Average displacement from the least-squares plane of the C20N4 porphyrinato core.
[c] Average distance of two least-squares planes of the C20N4 porphyrinato core. [d] Non-bonding distance be-
tween two covalently connected meso carbon atoms; [e] Angle between two least-squares planes of the C20N4
porphyrinato core. [f] Slip angle (average angle between the vector joining two macrocyclic centers and the
unit vectors normal to the two macrocyclic C20N4 porphyrinato cores). [g] Lateral shift: [sin(f)ꢃ(Ct···Ct)].
upon guest encapsulation, whilst the furthest meso carbon
atoms were separated by 6.75 and 6.76 ꢂ in complexes 2
and 3, respectively. The mean plane separations between the
two co-facial macrocycles were 3.66, 6.11, and 6.08 ꢂ in
complexes 1, 2 and 3, respectively. However, the slip angle
between the co-facial porphyrin units decreased substantial-
ly upon encapsulation of the guest (Table 3).
complex 2 shows two CN stretching frequencies at 2180 and
2215 cmꢀ1, which corresponded to ꢀ1.00eꢀ and ꢀ0.46eꢀ on
TCNQ molecules that were inside and outside the cavity, re-
spectively. However, Cs+, K+, and Na+ salts of TCNQ also
showed a single nitrile stretching band at 2180 cmꢀ1,[25]
which further authenticated the charge of ꢀ1.0eꢀ on the en-
capsulated TCNQ molecule.
Infrared spectroscopy: IR spectra has been a very useful
source of information on the nature of TCNQ in the com-
plex.[16,22] The most-characteristic band of neutral TCNQ is
the CN band (n˜ =2228 cmꢀ1). In the radical anion, the CN
band was shifted to lower frequency. The IR spectrum of
the crystal of complex 2 that was used for X-ray diffraction
(XRD) analysis (Figure 7) showed characteristic CN stretch-
ESR spectroscopy: Electron spin resonance (ESR) spectros-
copy is one of the most-sensitive techniques for detecting
paramagnetism. The EPR spectrum, which was recorded by
dissolving a pure crystal of complex 2 in degassed CH2Cl2 at
77 K, showed a sharp radical signal at around g=2.005
(Figure 8). A similar radical signal was also observed when
H4DEP (1) was chemically oxidized by ferrocenium hexa-
fluorophosphate (FcPF6). These line-widths and g values
were consistent with the presence of a bisporphyrin radical
cation and also a TCNQ radical anion.
Figure 7. IR spectra of a solid polycrystalline sample of H4DEP·TCNQ
(2).
ing frequencies at 2180 and 2215 cmꢀ1 (split band). The pres-
ence of two different nitrile absorptions was indicative of
the presence of two different TCNQ moieties, as was also
observed in the single-crystal X-ray structure of the mole-
cule. These data suggested that charge-transfer also took
place between H4DEP and TCNQ in the solid state.
Figure 8. X-band EPR spectrum in CH2Cl2 (at 77 K) of A) poly-crystal-
line H4DEP·TCNQ (2) and B) H4DEP, upon one-electron oxidation with
ferrocenium hexafluorophasphate (FcPF6).
1
1H NMR spectroscopy: H NMR titration experiments were
Both crystallographic analysis and IR spectroscopy could
be used to analyze the extent of charge-transfer that in-
volved TCNQ in the crystals. By comparing the values with
those for neutral and anionic TCNQ molecules, we estimat-
ed the amount of negative charge-transfer and its distribu-
tion within the couples.[25] The IR stretching frequencies
carried out at 298 K in CDCl3 to investigate the nature of
the host–guest complexation process. The formation of
p-complexes 2 and 3 was also confirmed by H NMR spec-
troscopy (Figure 9 and Figure 10). Figure 9A shows a region
of the well-resolved spectrum of complex 1 alone (in
CDCl3) and Figure 9B shows free AcH+ (in CDCl3). Upon
1
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Encapsulation within a Bisporphyrin Cavity
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Figure 9. 1H NMR spectra in CDCl3 (at 298 K) of A) H4DEP (1),
B) AcH+ClO4ꢀ, and C) polycrystalline [H4DEP·AcH]ClO4 (3). For the
atom labeling, see the Supporting Information, Figure S3.
Figure 10. 1H NMR spectra in CDCl3 (at 298 K) of A) H4DEP (1),
B) TCNQ, and C) polycrystalline H4DEP·TCNQ (2). For the atom label-
ing, see the Supporting Information, Figure S3.
encapsulation of AcH+ within the bisporphyrin cavity (3),
the spectrum changed completely. Figure 9C shows a region
1
of the H NMR spectrum of polycrystalline samples of com-
1 was determined by measuring the intensity of the signal at
512 nm during the titration.
plex 3 (in CDCl3) in which guest protons were shifted up-
field because of the close proximity to the porphyrin sub-
units and hence the strong ring-current effect. Moreover, no
peaks were observed in the free guest ligand regions. Similar
spectroscopic features were also expected in the titration
with TCNQ. However, the resonances owing to the bispor-
phyrin moiety of complex 2 were very broad, whilst the en-
capsulated TCNQ protons were too broad to be observed
(Figure 10); such broadening was due to the radical nature
of complex 2 in solution, which was also manifested by
a strong EPR signal (at 77 K) at g=2.005 and by the pres-
ence of low-energy bands in the UV/Vis spectrum. These re-
sults further confirmed that the host–guest assemblies in
complexes 2 and 3 were robust in solution.
For 1:1 complexation, Equation (1) was used for fitting
the linear curve.[26]
ðAꢀA0Þ=ðA1ꢀAÞ ¼ K½Lꢃ
ð1Þ
A0 and A are the absorbance of complex 1 in the absence
and presence of guest molecules, respectively. The changes
in absorbance were plotted against the concentration of the
guest (Figure 11), which was then best-fit for 1:1 binding of
H4DEP with the guest. The association constants (Kasso
were 1.3
(ꢄ0.2)ꢃ104 mꢀ1
for AcH+ with H4DEP.
)
A
ACHTUNGTRENNUNG
Cyclic voltammetry: Cyclic voltammetry (CV) and differen-
tial pulse voltammetry (DPV) were performed at 258C
under a nitrogen atmosphere in CH2Cl2 with 0.1m tetrabu-
tylammonium hexafluorophosphate (TBAH) as the support-
ing electrode; the potentials are summarized in Table 4. For
the free bisporphyrin ligand (1), the electrochemical re-
sponse revealed four consecutive ring-centered oxidations
Association constant: The association constant of TCNQ
with bisporphyrin host 1 was calculated by measuring the
changes in intensity of the peak at 509 nm in the UV/Vis
spectrum of complex 1 during the titration with TCNQ,
which eventually formed H4DEP·TCNQ (2). Similarly, the
association constant of the acridinium ion with complex
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S. P. Rath and A. Chaudhary
and oxidation potentials, re-
spectively, indicated that it was
more difficult to reduce/oxidize
the encapsulated complex (2)
because of the formation of the
charged complex (bisporphyrin
ꢀC
p-cation radical and TCNQ ).
Similar situations were also ob-
served for the AcH+-encapsu-
lated complex (3). For the
DPVs of all the complexes re-
ported herein, see the Support-
ing Information, Figure S5.
Figure 12. CVs
CH2Cl2) of A) free TCNQ and
B) H4DEP·TCNQ (2) with
0.1m tetraACTHNUTRGNEU(GN n-butyl)ammonium
hexafluorophosphate as the
supporting electrolyte. The ref-
erence electrode was Ag/AgCl,
(298 K,
in
Photophysical properties: The scan rate: 100 mVsꢀ1
photochemical behavior of
.
complexes 1–3 was studied by
steady-state fluorescence spectroscopy. H4DEP (1, in
CH2Cl2, excitation: 560 nm) showed two emission bands at
640 and 697 nm. However, upon excitation at the same
wavelength, complexes 2 and 3 also produced two emission
bands: one underwent a blue-shift to 630 nm whilst the
other remained at the same position (697 nm). Moreover,
upon photoexcitation at 560 nm, the emission intensities of
complexes 2 and 3 were quenched by 65% and
Figure 11. Linear plot for the determination of the association constant
(at 298 K) for the binding of H4DEP with A) TCNQ and B) AcH+. The
solid lines represent the best fit.
95%, respectively (Figure 13). These results indi-
cated the occurrence of excited-state events in the
Table 4. Electrochemical data.[a]
Compound
Eox (I) [V]
Eox (II) [V]
0.81[b]
Ered (I) [V]
Ered (II) [V]
supramolecular assembly and that efficient photo-
induced electron transfer (PET) took place from
the singlet state of H4DEP to TCNQ (in 2) and
AcH+ (in 3), which were further supported by
DFT calculations (see below).
H4DEP (1)
TCNQ
0.69[b]
–
ꢀ1.43[b]
–
–
–
–
0.19(65)[c]
0.14(60)[c]
ꢀ0.49[b]
ꢀ0.35(70)[c]
H4DEP·TCNQ (2)
0.85[b]
–
ꢀ0.42(65)[c]
ꢀ
AcH+ClO4
–
–
[H4DEP·AcH]ClO4 (3)
0.81[b]
0.90[b]
ꢀ0.61[b]
The thermodynamic feasibility of the excited-
state electron-transfer reaction was also examined
by using the Rehm–Weller expression (Equa-
tion (2)),[27] which is based on electrochemical and
fluorescence data.
[a] In CH2Cl2, the reference electrode was Ag/AgCl; [b] irreversible process; [c] half-
wave potentials, E1/2 =(Epa+Epc)/2, peak potential differences (in mV) given in paren-
theses.
(see the Supporting Information, Figure S4). At 0.69 V, one
+
ox
red
C
porphyrin unit was oxidized to generate radical 1 . Howev-
DGET ¼ E1=2 ꢀE1=2 ꢀEð0,0ÞþC
ð2Þ
er, owing to the presence of strong inter-macrocyclic interac-
tions and also to the close proximity of the first 1e-oxidized
ring, the second ring was oxidized at a significantly higher
ox
red
E1/2 is the oxidation potential of donor 1, E1/2 is the re-
duction potential of the acceptor (TCNQ/AcH+), and E(0,0)
potential (0.81 V) to produce 12( +). A similar situation arose
C
for the third- and fourth-electron-oxidized species, which oc-
curred at 1.16 and 1.39 V, respectively. Thus, the overall oxi-
dation process demonstrated the strong communication
between the two redox-active porphyrin macrocycles in
complex 1.
Neutral TCNQ showed two reversible redox waves at
+0.19 and ꢀ0.35 V, which corresponded to the reduction of
Cꢀ
TCNQ into TCNQ and TCNQ2ꢀ, respectively. Upon en-
capsulation of TCNQ within the bisporphyrin cavity, the
effect was clearly observed in the CV of complex 2
(Figure 12). The first and second reduction potentials were
50 and 70 mV more negative, respectively, whilst the first
oxidation potential was shifted to a more-positive potential
(at 0.85 V). The negative and positive shifts of the reduction
Figure 13. Normalized emission spectra (in CH2Cl2) of A) 1, B) 2, and
C) 3 (excited at 560 nm).
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Encapsulation within a Bisporphyrin Cavity
FULL PAPER
is the singlet excitation energy of H4DEP (2.03 eV), which
was calculated on the basis of fluorescence and the absorp-
tion band.[28] Because one or both the species is/are neutral
and the solvent was slightly polar, the coulombic term (C),
may be neglected herein. The driving force for electron
transfer (DGET) was exergonic by ꢀ1.32 eV for complex 2
and ꢀ0.61 eV for complex 3. The negative value of DGET in-
dicated that these electron-transfer processes were thermo-
dynamically favorable.
3 and was responsible for the quenching of the fluorescent
intensity.[29] However, no spectroscopic overlap was ob-
served between the emission spectrum of H4DEP and the
absorption spectrum of AcH+ (Figure 14C); therefore,
energy transfer from the excited state of the freebase bispor-
phyrin to AcH+ in complex 3 could be easily ruled out.
The extent of energy transfer in complex 3 was calculated
by using Equation (3) to be almost 98% (excitation:
340 nm).[5,7,8]
However, the quenching pathways may involve energy
transfer and/or electron transfer.[5–8,11–13] Energetically, these
two pathways were possible. TCNQ is a non-fluorescent
molecule, whereas AcH+ shows high fluorescence activity.
The steady-state fluorescence spectra of free AcH+ and
complex 3 are compared in Figure 14A. Excitation of free
AcH+ at 340 nm showed an emission maximum at 485 nm
with a shoulder at 462 nm. However, the fluorescence inten-
sity of encapsulated AcH+ in complex 3 (excitation: 340 nm)
was remarkably quenched in comparison to the free AcH+.
There was good overlap between the emission spectrum of
AcH+ (i.e., energy donor) and the absorption spectrum of
H4DEP (i.e., energy acceptor; Figure 14B), which facilitated
the efficient singlet-to-singlet energy transfer[29] from the ex-
cited state of AcH+ to the freebase bisporphyrin in complex
FET ¼ 1ꢀðAd=AdaÞ ꢅ ðIda=IdÞ
ð3Þ
FET is the energy-transfer efficiency, Ada is the absorbance
of the donor–acceptor complexes, Ad is the absorbance of
the donor in the absence of an acceptor, Ida is the emission
intensity of the donor–acceptor complex, and Id is the emis-
sion intensity of the donor in the absence of an acceptor.
However, more studies are required to probe the excited-
state dynamics of such host–guest complexes.
The emission of the free-base bisporphyrin, on excitation
at 560 nm, was also remarkably quenched upon encapsula-
tion of AcH+, due to thermodynamically favorable PET
from the excited state of bisporphyrin to AcH+. Thus,
herein, AcH+ acted as both an acceptor and a donor de-
pending on which part of the chromophore was being excit-
ed in the host–guest complex (3).
Fluorescence lifetime measurements: The fluorescence life-
times (t) of both free- and encapsulated AcH+ ions within
the bisporphyrin cleft in complex 3 were measured by time-
resolved fluorescence spectroscopy in which the samples
were excited at 340 nm whilst the transients were monitored
at 485 nm in CH2Cl2. The fluorescence decay profiles are
shown in Figure 15. Figure 15A shows the time-resolved
fluorescence-decay profile of free AcH+, which showed
a mono-exponential decay with a fluorescence lifetime of
27 ns. Under identical conditions, the fluorescence-decay
profile of encapsulated AcH+ in complex 3 was satisfactorily
fitted by bi-exponential decay, examined through the c2
value (Figure 15B). The major component (>80%) was at-
Figure 14. A) Normalized emission spectra (in CH2Cl2) of free AcH+
(solid line) and complex 3 (dotted line; excited at 340 nm). (B) Normal-
ized absorption spectrum of H4DEP and emission spectrum of free AcH+
in CH2Cl2. C) Normalized absorption spectrum of free AcH+ and emis-
sion spectrum of H4DEP in CH2Cl2.
Figure 15. Fluorescence decay profiles of: A) free AcH+ in CH2Cl2 (lex
=
340 nm), B) encapsulated AcH+ in [H4DEP·AcH]ClO4 (3; lex =340 nm)
in CH2Cl2, and C) the instrument response function.
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S. P. Rath and A. Chaudhary
tributed to an ultrashort time component, t1 =1.6 ns, and
the minor components (<20%) corresponded to t1 =27 ns,
which corresponded to free AcH+. The ultrashort time com-
ponent was responsible for the photoinduced energy transfer
from the excited state of AcH+ to the free-base bisporphyrin
(H4DEP), which also caused the fluorescence quenching in
the steady-state fluorescence measurements. Such an effi-
cient transfer in the excited state could only be possible
once the donor and acceptor moieties were in close proximi-
ty to one another, as demonstrated in complex 3.
0.71 eV, whilst the gap was 2.12 eV in H4DEP (1; Table 4
and the Supporting Information, Figure S4). The extremely
low HOMO–LUMO gap in complex 2 led[31] to facile elec-
tron transfer, even at room temperature, which was mani-
fested in the lowering of the CN stretch in the IR spectrum,
a strong radical signal in the EPR spectrum, and the pres-
ence of low-energy bands in the electronic spectrum (in so-
lution).
In general, the reorganization energy (l) increases linear-
ly with an increase in the distance between the electron
donor and the electron acceptor, where the PET takes
place.[12e] However, the smaller l value in host–guest com-
plex 2 resulted in the acceleration of the forward electron
transfer, but a deceleration of the back electron transfer.
Such an efficient electron transfer could only be possible
once the donor and acceptor moieties were in close proximi-
ty to one another, as demonstrated herein.
Theoretical calculations: Computational studies were per-
formed by using DFT at the B3LYP/6-31G level[30] to sup-
port the charge-separated species in the supramolecular
entity. DFT calculations on the basis of the coordinates
taken from the X-ray structure of the complex indicated
that the HOMO and LUMO of complex 2 were localized on
H4DEP and TCNQ, respectively (Figure 16). These results
further supported the supposition that H4DEP acted as an
electron donor, whilst TCNQ acted as an electron acceptor
in host–guest complex 2. The electrochemically evaluated
HOMO–LUMO (H4DEP–TCNQ) gap (difference between
the first oxidation and first reduction values) was only
The Mulliken charge distributions were also calculated[32]
for free and encapsulated TCNQ (in complex 2). For such
calculations, coordinates were taken directly from the X-ray
structures of neutral[33] and encapsulated TCNQ (in complex
2) using the same basis set. In both cases, charge distribu-
tions are given in Table 5. The charge density for free
Table 5. Mulliken charge distribution in neutral TCNQ and TCNQ in
complex 2.
Atom
Neutral TCNQ
TCNQ in 2
C1
C2
C3
C4
N
C3ꢀH
0.05
0.01
ꢀ0.09
0.094
ꢀ0.16
0.14
0.05
ꢀ0.06
0.04
0.090
ꢀ0.20
0.00
TCNQ only showed that the N and C3 atoms were quite
negative whereas the cyano carbons were positive. As
TCNQ became inserted into the H4DEP cleft in complex 2,
charge transfer took place between the receptor and the ac-
ceptor moieties. Thus, the electron density on the N and C2
atoms decreased, as well as on C3-H because of charge ac-
cumulation whereas almost no change was observed on the
C1 and C4 atoms as compared to neutral TCNQ.
The B3LYP/6-31G-generated frontier HOMO and
LUMO are also shown in Figure 17 for AcH+-encapsulated
complex 3. The HOMO and HOMOꢀ1 were located on one
of the porphyrin macrocycles, whilst the LUMO was located
solely on AcH+. The locations of the HOMO/HOMOꢀ1
and the LUMO also suggested the formation of a charge-
separated state in which H4DEP acted as an electron donor
whilst AcH+ acted as an electron acceptor in host–guest
complex 3. The electrochemically evaluated HOMO–
LUMO (H4DEP–AcH+) gap was 1.42 eV, which was possi-
Figure 16. A) HOMO and B) LUMO of complex 2 calculated by using
DFT at the B3LYP/6-31G level.
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Encapsulation within a Bisporphyrin Cavity
FULL PAPER
enabled us to investigate the changes in structure, proper-
ties, and conformation upon guest binding. Comparative
structural analysis demonstrated the exceptional ability of
this bisporphyrin platform to open its binding pocket for
substrate encapsulations by a vertical displacement of about
2.45 ꢂ. Moreover, the slip angle between the two co-facial
porphyrin units decreased substantially upon guest encapsu-
ꢀ
lation. In compound 1, strong p p interactions had a tenden-
cy to pull the macrocycles into a good degree of overlap
and, as a result, two redox centers strongly interacted with
each other in solution, as shown by the presence of four oxi-
dative signals in the CV spectrum. The negative and positive
shifts of the reduction and oxidation potentials in com-
pounds 2 and 3 indicated that it was difficult to reduce/oxi-
dize the encapsulated complex.
1
The solution H NMR spectrum of encapsulated complex
3 showed upfield shifts of the AcH+ protons, owing to
a strong ring-current effect. However, the signals owing to
the encapsulated TCNQ (in complex 2) were not observed
because of its radical nature in the complex. The association
constants (Kasso) between the host and guests in solution
were 1.3ꢃ104 and 1.8ꢃ104 mꢀ1 for complexes 2 and 3, re-
spectively. Low-energy bands between 650–900 nm in the
absorption spectra were approved upon addition of one
equivalent of TCNQ to a solution of H4DEP in CH2Cl2,
owing to the radical nature of the complex formed. The
EPR spectrum of complex 2 in CH2Cl2 at 77 K also showed
a radical signal that was centered at g=2.005, which was in
the characteristic region for both a porphyrin radical cation
and a TCNQ radical anion.
TCNQ is non-fluorescent whilst AcH+ shows very high
fluorescence activity. The fluorescence intensity of the en-
capsulated AcH+ in complex 3 (excitation at 340 nm) was
remarkably quenched versus the free ion. Good overlap be-
tween the emission spectrum of AcH+ (i.e., energy donor)
and the absorption spectrum of H4DEP (i.e., energy accept-
or) facilitated the efficient intramolecular energy transfer
from the excited state of AcH+ to the free base bisporphyrin
in complex 3. However, no spectroscopic overlap was ob-
served between the emission spectrum of H4DEP (1) and
the absorption spectrum of AcH+; thus, energy transfer
from the excited state of the freebase bisporphyrin to AcH+
was ruled out. Therefore, the remarkable quenching of the
fluorescence of AcH+ inside the bisporphyrin cavity upon
excitation at 560 nm was due to photoinduced electron
transfer from the excited state of bisporphyrin to AcH+,
which was also thermodynamically favorable. Thus, AcH+
acted as both an acceptor and a donor, depending on which
part of the chromophore was excited in the host–guest com-
plex (3). The location of the electron densities on the
HOMOs and LUMOs further supported the formation of
a charge-separated state in which H4DEP acted as an elec-
tron donor whilst TCNQ/AcH+ acted as an electron accept-
or in the host–guest complexes (2/3).
Figure 17. A) HOMOꢀ1, B) HOMO, and C) LUMO of complex 3 calcu-
lated by using DFT at the B3LYP/6-31G level.
bly the reason behind the charge transfer between the bis-
porphyrin and AcH+ in complex 3, as reflected in the pres-
ence of low-energy bands in the electronic spectra (in solu-
tion).
Conclusion
The electrochemically evaluated HOMO (H4DEP)–
LUMO (TCNQ/AcH+) gaps were 0.71 and 1.42 eV in com-
plexes 2 and 3, respectively, whilst the gap was 2.12 eV in
The synthesis, structures, and photophysical properties of
H4DEP (1), H4DEP·TCNQ (2), and [H4DEP·AcH]ClO4 (3)
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S. P. Rath and A. Chaudhary
Steady-state fluorescence spectra were recorded on a Perkin–Elmer LS
55 fluorescence spectrometer. The samples were prepared in CH2Cl2 and
the concentration was adjusted so that the absorbance was less than 0.1
(excitation at 340 and 560 nm). Absorption correction was done to nor-
malize the data. For the steady-state fluorescence and fluorescence-life-
time measurements, the samples were prepared in CH2Cl2 in air.
H4DEP (1). The extremely low HOMO–LUMO gap in com-
plex 2 led to facile electron transfer, even at room tempera-
ture, which was manifested by the lowering in the shift of
the CN stretch in the IR spectra, a strong radical signal in
the EPR spectra at 77 K, and the presence of low-energy
bands in the UV/Vis spectra (in solution). On the other
hand, partial charge transfer from bisporphyrin to AcH+
took place in complex 3. Such an efficient transfer was only
possible once the donor and acceptor moieties were in close
proximity to one another, as demonstrated herein, which
eventually lowered the reorganization energy (l).
X-ray diffraction and structure refinement: The crystals were coated with
a light-hydrocarbon oil and mounted under a 100 K dinitrogen stream on
a Bruker SMART APEX CCD diffractometer that was equipped with
CRYO Industries low-temperature apparatus; intensity data were collect-
ed by using graphite-monochromated Mo Ka radiation (l=0.71073 ꢂ).
Data integration and reduction were processed with SAINT software.[34]
An absorption correction was applied.[35] Structures were solved by direct
method using SHELXS-97 and were refined on F2 by full-matrix least-
squares using SHELXL-97.[36] Non-hydrogen atoms were refined aniso-
tropically. In the refinement, hydrogen atoms were treated as riding
atoms by using SHELXL default parameters.
Association constant:
A
stock solution of free TCNQ (10ꢀ3 m) and
Experimental Section
H4DEP (10ꢀ4 m) was prepared in CH2Cl2. The H4DEP concentration was
kept constant at 10ꢀ5 m throughout the experiment whilst the concentra-
tion of TCNQ was varied in the range 2ꢃ10ꢀ5–9ꢃ10ꢀ4 m. H4DEP (1 mL,
Materials: H4DEP was prepared according to a literature procedure.[13,20]
Reagents and solvents were purchased from commercial sources and pu-
rified by standard procedures before use.
10ꢀ4 m) was transferred into
a volumetric flask (10 mL), a weighed
amount of TCNQ was added, and the flask was filled to the mark with
CH2Cl2. In case of AcH+, a stock solution of AcH+ (10ꢀ3 m) and H4DEP
(10ꢀ4 m) was prepared in CH2Cl2. The concentration of H4DEP was kept
constant at 10ꢀ5 m throughout the experiment whilst the concentrations of
AcH+ was varied in the range 2ꢃ10ꢀ5–4ꢃ10ꢀ 4 m. H4DEP (1 mL, 10ꢀ5 m)
was transferred into a volumetric flask (10 mL), a weighed quantity of
AcH+ was added, and the flask was filled to the mark with CH2Cl2. All
of the solutions were allowed to stand for 30 min before use.
Preparation of H4DEP·TCNQ (2): To a solution of tetracyanoquinodi-
methane (TCNQ, 40 mg, 0.20 mmol) in CH2Cl2 (50 mL) was added
H4DEP (1, 100 mg, 0.083 mmol) and the mixture was stirred at RT for
10 min. The resulting solution was then evaporated to dryness. The solid
compound was dissolved in a minimum volume of CHCl3, MeCN was
carefully layered on top, and the sample was then left in air. On standing
for 6–7 days, the product was formed as a dark-brown crystalline solid,
which was then collected by filtration and dried under vacuum. Yield:
81 mg (70%); 1H NMR (CDCl3, 298 K): 9.06 (br, 6H; 5,10,15-meso-H),
5.80 (s, 4H; 37-CH2), 4.0–2.8 (m, 32H; CH2), 2.74 (m, 4H; 40-CH2), 1.98
(m, 12H; CH3), 1.75 (m, 12H; CH3), 1.47 (m, 12H; CH3), 1.31 (m, 12H;
Computational details: DFT calculations were carried out by using
a B3LYP hybrid functional and the Gaussian 03, revision B.04, pack-
age.[30] The method used was Becke’s three-parameter hybrid-exchange
functional,[37] the non-local correlation provided by the Lee, Yang, and
Parr expression, and the Vosko, Wilk, and Nuair 1980 correlation func-
tional (III) for local correction.[38] The basis set was 6–31G for C, N, O,
and H atoms. Single-point energy calculations, Mulliken’s charge density,
and TD-DFT calculations were performed in which all of the coordinates
were taken from the single-crystal X-ray structure used herein.
CH3), 1.27 (m, 6H; 41-CH3), ꢀ3.51 ppm (br, 4H; NH
ACHTUNGTREN(NUNG por)); UV/Vis
(CH2Cl2): lmax (e)=406 (3.6ꢃ105), 509 (4.0ꢃ104), 543 (1.9ꢃ104), 578
(1.6ꢃ104), 629 (8.3ꢃ103), 769 (6.1ꢃ103), 851 (6.2ꢃ103 molꢀ1 dm3 cmꢀ1); el-
emental analysis calcd (%) for C94H109N13: C 79.44, H 7.73, N 12.80;
found: C 79.30; H 7.84; N 12.91.
Preparation of [H4DEP·AcH]ClO4 (3): H4DEP (1; 100 mg, 0.083 mmol)
was added to a saturated solution of acridinium perchlorate (58 mg,
0.207 mmol) in CH2Cl2 (25 mL) and the mixture was stirred at RT for
10 min before being evaporated to dryness. The solid was dissolved in
a minimum amount of CHCl3, MeCN was carefully layered on top, and
the sample was then left in air. On standing for 6–7 days, the product was
formed as a dark-brown crystalline, which was then collected by filtration
and dried under vacuum. Yield: 80 mg (65%); 1H NMR (CDCl3, 298 K):
9.51 (s, 2H; 10-meso-H), 9.17 (s, 4H; 5,15-meso-H), 8.46 (s, 1H; AcH-H),
7.90 (d, J=7.6 Hz, 2H; AcH-H), 7.69 (d, J=7.6 Hz, 2H; AcH-H), 7.64
(t, J=7.6 Hz, 2H; AcH-H), 7.34 (t, J=7.9 Hz, 2H; AcH-H), 6.52 (br,
1H; NH-pyrrole), 5.89 (s, 4H; 37-CH2), 4.3–3.1 (m, 32H; CH2); 2.71 (q,
J=7.1 Hz, 4H; 40-CH2), 1.71 (t, J=7.7 Hz, 12H; CH3), 1.62 (t, J=
7.6 Hz, 12H; CH3), 1.48 (t, J=7.5 Hz, 12H; CH3), 1.53 (t, J=7.5 Hz,
12H; CH3), 1.02 ppm (t, J=7.6 Hz, 6H; 41-CH3); UV/Vis (CH2Cl2): lmax
(e)=406 (1.27ꢃ105), 512 (7.56ꢃ104), 543 (7.8ꢃ104), 581 (7.73ꢃ104), 632
The MS (ESI) spectrum of H4DEP (1), the molecular orbitals responsible
for low-energy bands in complex 2, atom labeling for the 1H NMR as-
signments, CV of compound 1 (Figure S4), and DPV of compounds 1–3
are provided in the Supporting Information. CCDC-860298 (H4DEP, 1),
CCDC-860297
(H4DEP·TCNQ,
2),
and
CCDC-860299
([H4DEP·AcH]·ClO4, 3) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
Acknowledgements
(2.5ꢃ103 molꢀ1 dm3 cmꢀ1);
elemental
analysis
calcd
(%)
for
C95H115N10ClO4: C 76.26, H 7.75, N 9.41; found: C 76.33, H 7.82, N 9.36.
We are thankful to the Department of Science and Technology, Govern-
ment of India, and the CSIR (India) for financial support. A.C. thanks
the CSIR (India) for a fellowship. We thank Prof. Anindya Dutta and
Anjali Dhir for the fluorescence lifetime measurements.
Instrumentation: UV/Vis spectra were recorded on a PerkinElmer UV/
Vis spectrometer. Elemental analysis was performed on a CE-440 ele-
mental analyzer. 1H NMR spectra were recorded on a JEOL 400 MHz
spectrometer. The residual solvent peaks were used as a secondary refer-
ence. MS (ESI) spectra were recorded on a Waters Micromass Quattro
Micro triple quadropole mass spectrometer. Cyclic voltammetry was per-
formed on a BAS Epsilon electrochemical workstation in CH2Cl2 with
0.1m tetrabutylammonium hexafluorophoshate as the supporting electro-
lyte, Ag/AgCl as the reference electrode, and Pt wire as the auxiliary
electrode. The concentration of the compounds was of the order 10ꢀ3 m.
The ferrocene/ferrocenium couple was at E1/2 =+0.45(65) V versus Ag/
AgCl under the same experimental conditions.
[1] J.-M. Lehn, Science 2002, 295, 2400–2403.
[2] a) P. Mal, B. Breiner, K. Rissanen, J. R. Nitschke, Science 2009, 324,
1679–1699; b) D. Ajami, J. Rebek, Jr., Nat. Chem. 2009, 1, 87–90;
c) M. D. Piuth, R. G. Bergman, K. N. Raymond, Science 2007, 316,
85–88; d) M. Yoshizawa, M. Tamura, M. Fujita, Science 2006, 312,
251–254; e) J. Kang, J. Jr Rebek, Nature 1997, 385, 50–52; f) D. J.
Cram, Nature 1992, 356, 29–36.
&
12
&
www.chemeurj.org
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Encapsulation within a Bisporphyrin Cavity
FULL PAPER
[3] a) D. M. Vriezema, M. C. Aragones, J. A. A. W. Elemans, J. J. L. M.
Cornelissen, A. E. Rowan, R. J. M. Notle, Chem. Rev. 2005, 105,
1445–1485; b) M. Yoshizawa, T. Kusukawa, M. Fujita, K Yamagu-
chi, J. Am. Chem. Soc. 2000, 122, 6311–6312.
[4] J. P. Collman, P. S. Wagenknecht, J. E. Hutchison, Angew. Chem.
1994, 106, 1620–1639; Angew. Chem. Int. Ed. Engl. 1994, 33, 1537–
1554.
Yamaji, Y. Hama, S. Arai, M. Hoshino, Inorg. Chem. 1987, 26,
4375–4378.
[17] a) H. Kotani, K. Ohkubo, M. J. Crossley, S. Fukuzumi, J. Am. Chem.
Soc. 2011, 133, 11092–11095; b) D. Kim, S. Lee, G. Gao, H. S. Kang,
J. Ko, J. Organomet. Chem. 2010, 695, 111–119; c) M. Tanaka, K.
Ohkubo, C. P. Gros, R. Guilard, S. Fukuzumi, J. Am. Chem. Soc.
2006, 128, 14625–14633.
[5] a) I. Beletskaya, V. S. Tyurin, A. Y. Tsivadze, R. Guilard, C. Stern,
Chem. Rev. 2009, 109, 1659–1713; b) P. D. Harvey, C. Stern, C. P.
Gros, R. Guilard, Coord. Chem. Rev. 2007, 251, 401–428.
[6] a) D. Wrꢄbel, A. Graja, Coord. Chem. Rev. 2011, 255, 2555–2577;
b) P. D. W. Boyd, C. A. Reed, Acc. Chem. Res. 2005, 38, 235–242;
c) K. Lang, J. Mosinger, D. M. Wagnerovꢅ, Coord. Chem. Rev. 2004,
248, 321–350.
[7] a) F. D’Souza, O. Ito, Chem. Commun. 2009, 4913–4928; b) F.
D’Souza, O. Ito, Coord. Chem. Rev. 2005, 249, 1410–1422.
[8] a) J. Rosenthal, D. G. Nocera, Acc. Chem. Res. 2007, 40, 543–553;
b) J. Rosenthal, J. Bachman, J. L. Dempsey, A. J. Esswein, T. G.
Gray, J. M. Hodgkiss, D. R. Manke, T. D. Luckett, B. J. Pistorio,
A. S. Veige, D. G. Nocera, Coord. Chem. Rev. 2005, 249, 1316–1326;
c) V. V. Borovkov, G. A. Hembury, Y. Inoue, Acc. Chem. Res. 2004,
37, 449–459.
[9] a) T. E. Clement, D. J. Nurco, K. M. Smith, Inorg. Chem. 1998, 37,
1150–1160; b) C. J. Medforth, J. D. Hobbs, M. R. Rodriquez, R. J.
Abraham, K. M. Smith, J. A. Shelnutt , Inorg. Chem. 1995, 34,
1333–1341.
[18] a) W. Kaim, B. Schwederski, Coord. Chem. Rev. 2010, 254, 1580–
1588; b) T.-C. Tseng, C. Urban, Y. Wang, R. Otero, S. L. Tait, M.
Alcami, D. Ecija, M. Trelka, J. M. Gallego, N. Lin, M. Konuma, U.
Starke, A. Nefedov, A. Langer, C. Woll, M. A. Herranz, F. Martin,
N. Martin, K. Kern, R. Miranda, Nat. Chem. 2010, 2, 374–379.
[19] S. Fukuzumi, Phys. Chem. Chem. Phys. 2008, 10, 2283–2297.
[20] a) D. V. Yashunsky, D. P. Arnold, G. V. Ponomarev, Chem. Hetero-
cycl. Compd. 2000, 36, 275–280; b) D. V. Yashunsky, D. P. Arnold,
G. V. Ponomarev, Tetrahedron Lett. 1997, 38, 105–108.
[21] a) H. Song, R. D. Orosz, C. A. Reed, W. R. Scheidt, Inorg. Chem.
1990, 29, 4274–4282; b) J. Fajer, D. C. Borg, A. Forman, D. Dolphin,
R. H. Felton, J. Am. Chem. Soc. 1970, 92, 3451–3459; c) J. H. Fuhr-
hop, D. Mauzerall, J. Am. Chem. Soc. 1969, 91, 4174–4181; d) J. H.
Fuhrhop, D. Mauzerall, J. Am. Chem. Soc. 1968, 90, 3875–3876.
[22] a) L. Ballester, A. M. Gil, A. Gutierrez, M. F. Perpinan, A. E. San-
chez, M. Fonari, K. Suwinska, V. Belsky, Eur. J. Inorg. Chem. 2003,
3034–3041; b) J. S. Chappell, A. N. Bloch, W. A. Bryden, M. Max-
field, T. O. Poehler, D. O. Cowan, J. Am. Chem. Soc. 1981, 103,
2442–2443.
[10] a) J.-M. Camus, S. M. Aly, C. Stern, R. Guilard, P. D. Harvey, Chem.
Commun. 2011, 47, 8817–8819; b) J. D. Megiatto Jr, D. I. Schuster,
S. Abwandner, G. De Miguel, D. M. Guldi, J. Am. Chem. Soc. 2010,
132, 3847–3861; c) H. Nobukuni, Y. Shimazaki, F. Tani, Y. Naruta,
Angew. Chem. 2007, 119, 9133–9136; Angew. Chem. Int. Ed. 2007,
46, 8975–8978; d) J.-Y. Liu, H.-S. Yeung, W. Xu, X. Li, D. K. P. Ng,
Org. Lett. 2008, 10, 5421–5424.
[11] a) F. D’Souza, A. N. Amin, M. E. EI-Khouly, N. K. Subbaiyan, M. E.
Zandler, S. Fukuzumi, J. Am. Chem. Soc. 2012, 134, 644–654;
b) M. E. EI-Khouly, D. K. Ju, K.-Y. Kay, F. Dꢁsouza, S. Fukuzumi,
Chem. Eur. J. 2010, 16, 6193–6202; c) A. Takai, M. Chkounda, A.
Eggerspiller, C. P. Gros, M. Lachkar, J-M. Barbe, S. Fukuzumi, J.
Am. Chem. Soc. 2010, 132, 4477–4489; d) T. Honda, T. Nakanishi,
K. Ohkubo, T. Kojima, S. Fukuzumi, J. Am. Chem. Soc. 2010, 132,
10155–10163; e) A. Takai, C. P. Gros, J-M. Barbe, R. Guilard, S. Fu-
kuzumi, Chem. Eur. J. 2009, 15, 3110–3122.
[23] a) F. L. Jiang, D. Fortin, P. D. Harvey, Inorg. Chem. 2010, 49, 2614–
2623; b) M. Toganoh, T. Hihara, H. Furuta, Inorg. Chem. 2010, 49,
8182–8184.
[24] W. R. Scheidt, Y. J. Lee, Struct. Bonding (Berlin) 1987, 64, 1–70.
[25] a) X. Qu, J. Lu, C. Zhao, J. F. Boas, B. Moubaraki, K. S. Murray, A.
siriwardana, A. M. Bond, L. L. Martin, Angew. Chem. 2011, 123,
1627–1630; Angew. Chem. Int. Ed. 2011, 50, 1589–1592; b) D. M.
Eichhorn, S. Yang, W. Jarrell, T. F. Baumann, L. S. Beall, A. J. P.
White, D. J. Williams, A. G. M. Barrett, B. M. Hoffman, J. Chem.
Soc. Chem. Commun. 1995, 1703–1704.
[26] S. Fukuzumi, Y. Kondo, S. Mochizuki, T. Tanaka, J. Chem. Soc.
Perkin Trans. 2 1989, 1753–1761.
[27] a) D. Rehm, A. Weller, Isr. J. Chem. 1970, 10, 259–261; b) A.
Weller, Z. Phys. Chem. N. F. 1983, 133, 93–98.
[28] C. Luo, D. M. Guldi, H. Imahori, K. Tamaki, Y. Sakata, J. Am.
Chem. Soc. 2000, 122, 6535–6539.
[12] a) J. W. Leeland, F. J. White, J. B. Love, J. Am. Chem. Soc. 2011, 133,
7320–7323; b) C. P. Gros, S. M. Aly, M. E. Ojaimi, J-M. Barbe, F.
Brisach, A. S. Abd-El-Aziz, R. Guilard, P. D. Harvey, J. Porphyrins
Phthalocyanins, 2011, 15, 467–479; c) P. D. Harvey, C. Stern, C. P.
Gors, R. Guilard, J. Porphyrins Phthalocyanins, 2010, 14, 55–63;
d) P. Chen, H. Lau, B. Habermeyer, C. P. Gros, J-M. Barbe, K. M.
Kadish, J. Porphyrins Phthalocyanins, 2007, 11, 244–257; e) G.
Givaja, M. Volpe, M. A. Edwards, A. J. Blake, C. Wilson, M.
Schroder, J. B. Love, Angew. Chem. 2007, 119, 590–592; Angew.
Chem. Int. Ed. 2007, 46, 584–586.
[13] A. Chaudhary, S. P. Rath, Chem. Eur. J. 2011, 17, 11478–11487.
[14] a) A. Chaudhary, R. Patra, S. P. Rath, Indian J. Chem. 2011, 50A,
1436–1442; b) S. K. Ghosh, S. P. Rath, J. Am. Chem. Soc. 2010, 132,
17983–17985; c) S. Bhowmik, S. K. Ghosh, S. P. Rath, Chem.
Commun. 2011, 47, 4790–4792; d) S. Brahma, Sk. A. Ikbal, S. P.
Rath, Inorg. Chim. Acta 2011, 372, 62–70; e) S. K. Ghosh, R. Patra,
S. P. Rath, Inorg. Chem. 2010, 49, 3449–3460; f) S. K. Ghosh, R.
Patra, S. P. Rath, Inorg. Chim. Acta 2010, 363, 2791–2799; g) S. K.
Ghosh, R. Patra, S. P. Rath, Inorg. Chem. 2008, 47, 10196–10198.
[15] a) L. J. Pace, A. Ulman, J. A. Ibers, Inorg. Chem. 1982, 21, 199–207;
b) H. A. Staab, J. Weikard, A. Ruckemann, A Schwogler, Eur. J.
Org. Chem. 1998, 2703–2712; c) M. M. Olmstead, A. B-Dias, H. M.
Lee, D. Pham, A. L. Balch, Dalton Trans. 2003, 3227–3232.
[16] a) Y. Li, Y. Zhao, A. H. Flood, C. Liu, H. b. Liu, Y. l. Li, Chem. Eur.
J. 2011, 17, 7499–7505; b) W. Hibbs, A. M. Arif, M. Botoshansky,
M. Kaftory, J. S. Miller, Inorg. Chem. 2003, 42, 2311–2322; c) M.
[29] J. R. Lakowicz, Principle of fluorescence spectroscopy; 3rd ed,
Springer: Singapore, 2006.
[30] Gaussian 03, Revision B.04, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgom-
ery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani,
N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C.
Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cio-
slowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, L. Komaro-
mi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wall-
ingford CT, 2004.
[31] a) D. F. Perepichka, M. R. Bryce, C. Pearson, M. C. Petty, E. J. L.
Mcinnes, J. P. Zhao, Angew. Chem. 2003, 115, 4784–4787; Angew.
Chem. Int. Ed. 2003, 42, 4636–4639; b) D. F. Perepichka, M. R.
Bryce, A. S. Batsanov, E. J. L. Mcinnes, J. P. Zhao, R. D. Farley,
Chem. Eur. J. 2002, 8, 4656–4669.
Chem. Eur. J. 2012, 00, 0 – 0
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
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&
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S. P. Rath and A. Chaudhary
[32] J. S. Miller, J. H. Zhang, W. M. Reiff, D. A. Dixon, L. D. Preston,
A. H. Reis Jr, E. Gebert, M. Extine, J. Troup, A. J. Epstein, M. D.
Ward, J. Phys. Chem. 1987, 91, 4344–4360.
[36] G. M. Sheldrick, SHELXL-97: Program for Crystal Structure Refine-
ment; University of Gçttingen: Gçttingen, Germany, 1997.
[37] A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652.
[33] R. E. Long, R. A. Sparks, K. N. Trueblood, Acta Crystallogr. 1965,
18, 932–939.
[38] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789.
[34] SAINT+, 6.02 ed.; Bruker AXS, Madison, WI, 1999.
[35] G. M. Sheldrick, SADABS 2.0, 2000.
Received: January 4, 2012
Published online: && &&, 2012
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These are not the final page numbers!

Encapsulation within a Bisporphyrin Cavity
FULL PAPER
Donor–acceptor complexes, which
were constructed from free base bis-
porphyrin (H4DEP) as a host, strongly
encapsulated two electron-deficient
guests, TCNQ and the acridinium ion,
in its clefts. The extremely low electro-
chemically evaluated HOMO–LUMO
gap in H4DEP·TCNQ led to facile
electron transfer from the host to the
guest at room temperature, whilst par-
tial electron transfer took place in
[H4DEP·AcH]ClO4 (see figure).
Donor–Acceptor Systems
A. Chaudhary, S. P. Rath* . . &&&& — &&&&
Encapsulation of TCNQ and the Acri-
dinium Ion within a Bisporphyrin
Cavity: Synthesis, Structure, and
Photophysical and HOMO–LUMO-
Gap-Mediated Electron-Transfer
Properties
Chem. Eur. J. 2012, 00, 0 – 0
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These are not the final page numbers!