Axial coordination of porphyrinatocobalt(II) complexes with bis(pyridinolato)silicon(IV) phthalocyanines

Article abstract of DOI:10.1002/ejic.200700451

Treatment of dichlorosilicon(IV) phthalocyanine with 3- or 4-hydroxypyridine in the presence of pyridine in toluene gave the corresponding bis(pyridinolato)silicon(IV) phthalocyanine complexes SiPc(3-OPy)₂ (1) or SiPc(4-OPy)₂ (2), re

Full text of DOI:10.1002/ejic.200700451

FULL PAPER
DOI: 10.1002/ejic.200700451
Axial Coordination of Porphyrinatocobalt(II) Complexes with
Bis(pyridinolato)silicon(IV) Phthalocyanines
Xuebing Leng[a] and Dennis K. P. Ng*[a]
Keywords: Phthalocyanines / Porphyrins / Axial coordination / UV/Vis spectroscopy
Treatment of dichlorosilicon(IV) phthalocyanine with 3- or 4-
hydroxypyridine in the presence of pyridine in toluene gave
two pyridyl ligands forming the corresponding mixed phthalo-
cyanine–porphyrin triads. The binding constants K1 be-
the corresponding bis(pyridinolato)silicon(IV) phthalocyan- tween the 4-pyridyl phthalocyanine 2 and the porphyrinato-
ine complexes SiPc(3-OPy)2 (1) or SiPc(4-OPy)2 (2), respec-
tively, which were spectroscopically and structurally charac-
terized. As shown by electronic absorption spectroscopy,
these compounds axially bind to meso-tetraphenylporphy-
cobalt(II) complexes (1.1–1.2ϫ104 –1) are about threefold
M
higher than those for the 3-pyridyl counterpart 1. The hetero-
dyads 2·3 and 2·4 were isolated by column chromatography
and characterized by mass and absorption spectroscopy.
rinatocobalt(II) [Co(TPP) (3)] and meso-tetrakis(3,5-di-tert- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
butylphenyl)porphyrinatocobalt(II) [Co(TBPP) (4)] with the
Germany, 2007)
been reported recently.[7] Although axial coordination has
been widely used to construct various multiporphyrin sys-
tems,[8] the use of this strategy to build mixed phthalocyan-
ine–porphyrin scaffolds remains little studied.[9] We have re-
cently prepared the bis(4-pyridinolato)silicon(IV) phthalo-
cyanine (2), which can axially bind to various tetrapyr-
rolatozinc(II) derivatives forming the corresponding 1:2 or
1:1 molecular assemblies.[9b] We describe herein an exten-
sion of this work using 2 as well as the 3-pyridyl analogue
1 as the cores to complex with porphyrinatocobalt(II) com-
plexes. The relatively strong cobalt–pyridine binding inter-
actions allow the isolation of the heterodyads.
Introduction
Phthalocyanines and porphyrins are two important
classes of functional dyes. Owing to their unique and intri-
guing properties, these macrocycles have found widespread
applications in various disciplines ranging from materials
science, catalysis, nanotechnology to medicine.[1] Despite
their structural similarities, these two classes of π systems
exhibit very different optical and electronic properties mak-
ing them useful in different areas. A hybrid system contain-
ing both of these macrocycles may combine their advan-
tageous properties and improve the overall performance.
One obvious example is the complementary major absorp-
tions of phthalocyanines (650–700 nm) and porphyrins
(400–450 nm) in the visible region. Mixed phthalocyanine–
porphyrin assemblies can absorb strongly over a large part
of the solar spectrum, which can facilitate various light-
induced processes. This property is important in applica-
tions such as light harvesting, photovoltaics, and molecular
photonics.[2] A substantial number of mixed phthalocyan-
ine–porphyrin arrays have been reported.[3] Apart from a
covalent linkage the two types of macrocycles can also be
linked by a metal center in the form of sandwich-type com-
plexes,[4] by a bridging nitrido, oxo, chloro, or hydroxo li-
gand to form cofacial complexes[5] or by electrostatic inter-
actions to form face-to-face aggregates.[3,6] The use of host-
guest interactions to assemble these macrocycles has also
Results and Discussion
The preparation of bis(3-pyridinolato)silicon(IV) phthalo-
cyanine complex 1 was similar to that of the 4-pyridyl ana-
logue 2 (Figure 1).[9b] It involved a ligand-substitution reac-
tion of dichlorosilicon(IV) phthalocyanine with 3-hydroxy-
pyridine in the presence of pyridine in toluene. Both 1 and
2 were soluble in common organic solvents and could be
purified readily by column chromatography giving a com-
parable yield (75% and 72%, respectively). The porphyrin-
atocobalt(II) complexes Co(TPP) (3) and Co(TBPP) (4)
(Figure 1) were prepared by cobaltation of the correspond-
ing metal-free porphyrins.[10]
Both compounds 1 and 2 were fully characterized by
using various spectroscopic methods and X-ray diffraction
analyses. Single crystals of 1 were grown by slow diffusion
of nitrobenzene into a CHCl3 solution of 1. The compound
cocrystallized with two molecules of nitrobenzene in the tri-
clinic system. As shown in part a of Figure 2, the structure
contains an inversion center at the silicon center relating
[a] Department of Chemistry and Center of Novel Functional
Molecules, The Chinese University of Hong Kong,
Shatin, N.T., Hong Kong, China
Fax: +852-2603-5057
E-mail: dkpn@cuhk.edu.hk
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2007, 4615–4620
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4615

X. Leng, D. K. P. Ng
FULL PAPER
cyanine ring and two oxygen atoms of the pyridinolato li-
gands. The Si–O [1.740(2) Å] and average Si–N [1.912(4) Å]
bond lengths as well as the other structural parameters are
unexceptional.
Single crystals of 2 were grown by slow diffusion of
MeOH into a CHCl3 solution of 2. The compound crys-
tallized in the monoclinic system. The molecular structure
of 2 (Figure 2, b) also contains an inversion center. The Si–
O [1.715(2) Å] and average Si–N [1.910(4) Å] bond lengths
are comparable with those of 1. The phthalocyanine rings
of 1 and 2 are essentially planar with a dihedral angle of
42.5° and 57.5°, respectively, between the phthalocyanine
N(isoindole)4 plane and the pyridyl ring. In both structures,
particularly for 2, the pyridyl-nitrogen atoms point outward
favoring the complexation process.
The complexation of SiPc(4-OPy)2 (2) and Co(TPP) (3)
was first studied by electronic absorption spectroscopy. Fig-
ure 3 shows the UV/Vis spectra of mixtures of these two
compounds in different ratios in CHCl3, where the total
concentration was fixed at 5.0 µ. It can be seen that as the
mole fraction of SiPc(4-OPy)2 (2) increases, the phthalocy-
anine B band at 354 nm, Q band at 684 nm, and vibronic
band at 614 nm all increase in intensity. The porphyrin So-
ret band at 410 nm becomes attenuated and a new band at
Figure 1. Structures of the bis(pyridyl) phthalocyanines 1 and 2,
and the porphyrinatocobalt(II) complexes 3 and 4.
the two halves of the molecule. The silicon center is hexaco-
ordinate with four isoindole nitrogen atoms of the phthalo-
Figure 3. Absorption spectra of mixtures of SiPc(4-OPy)2 (2) and
Co(TPP) (3) in CHCl3. The total concentration of the two com-
pounds was fixed at 5.0 µ.
Figure 2. Molecular structures of (a) SiPc(3-OPy)2 (1) and
(b) SiPc(4-OPy)2 (2) showing the 30% probability thermal ellip-
soids for all non-hydrogen atoms.
Figure 4. Job’s plot for the complexation of SiPc(4-OPy)2 (2) and
Co(TPP) (3) in CHCl3 obtained by monitoring the band at 410 nm.
4616
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4615–4620

Bis(pyridinolato)silicon(IV) Phthalocyanines
435 nm appears, which can be attributed to the axially where b is the optical path length (1 cm); ∆A is the change
bound species. The corresponding Job’s plot[11] (Figure 4), in absorbance at 435 nm, where the largest change was ob-
obtained by monitoring the band at 410 nm, shows a mini- served; St is the total concentration of substrate (i.e. 3); [L]
mum when the mole fraction of 2 is about 0.34. This sug- is the concentration of ligand [i.e. 2, which can be approxi-
gests a 1:2 stoichiometry for 2 and 3, and the formation of mated as Lt (the total concentration of ligand) where
the heterotriad 2·(3)2.
Lt ϾϾSt]; and ∆ε = ε11 – εS – εL, where ε11, εS, and εL are
Figure 5 shows the changes of the Soret band of the molar absorptivities of the 1:1 complex, 3, and 2 at
Co(TPP) (3), fixed at a concentration of 4.5 µ, upon ti- 435 nm, respectively. A plot of 1/∆A vs. 1/[2] (inset of Fig-
tration with SiPc(4-OPy)2 (2) (from 75 to 260 µ) in CHCl3. ure 5) gave a straight line from which the value of K1 was
The corresponding solution of 2 with the same concentra- determined to be (1.2Ϯ0.1)ϫ104 –1. Similarly, a linear re-
tion was used as the reference in recording the spectra. Un- lationship was also found in the Scott or Scatchard plot
der these conditions the phthalocyanine SiPc(4-OPy)2 (2) giving virtually the same K1 value.[12]
was in great excess. Therefore, the 1:1 complex was pre-
The complexation of other systems including SiPc(4-
dominantly formed and the Benesi–Hildebrand equation OPy)2 (2) with Co(TBPP) (4), as well as the 3-pyridyl ana-
[Equation (1)] could be applied to determine the binding logue 1 with these two porphyrinatocobalt(II) complexes,
constant K1.[12]
was investigated by the same approach. All the systems gave
very similar spectral changes except the complexation of
SiPc(3-OPy)2 (1) with Co(TBPP) (4), for which the band
ascribed to the axially bound species appeared as a shoul-
der at ca. 440 nm instead of a distinct signal (see Figure S1
in the Supporting Information). The results showed that
both phthalocyanines 1 and 2 bind to porphyrinato-
cobalt(II) complexes 3 and 4 in a 1:2 manner proceeding in
a stepwise fashion as shown in Figure 6.
(1)
Table 1 summarizes the binding constants (K1) for these
systems determined by absorption spectroscopy. The corre-
sponding data for the complexation of 3- and 4-hydroxy-
pyridine (3-OHPy and 4-OHPy) with Co(TPP) (3) were also
determined by the same method and are included for com-
parison. It can be seen that the values for the 4-pyridinolato
complex 2 are about three times larger than those of the 3-
pyridinolato counterpart 1. The addition of tert-butyl
groups on the meso-phenyl substituents of porphyrin does
not have a significant influence on the binding constants.
The stronger binding for 2 compared with that of 1 can be
attributed to the fact that the 4-pyridinolato ligand is a bet-
ter σ donor than the 3-pyridinlolato analogue (because of
the presence of the resonance form A as shown in Figure S2
in the Supporting Information). In addition, the 4-pyridin-
Figure 5. Changes in the UV/Vis spectrum of Co(TPP) (3) (4.5 µ)
upon titration with SiPc(4-OPy)2 (2) (from 75 to 260 µ) in CHCl3.
The inset shows the corresponding Benesi–Hildebrand plot ob-
tained by monitoring the change in absorbance at 435 nm.
Figure 6. A schematic diagram showing the axial coordination porphyrinatocobalt(II) complexes 3 and 4 with bis(pyridyl) phthalocyanines
1 and 2.
Eur. J. Inorg. Chem. 2007, 4615–4620
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4617

X. Leng, D. K. P. Ng
FULL PAPER
olato ligand can readily complex with the cobalt center, but
for the 3-pyridinolato analogue complexation can only oc-
cur when the nitrogen atom is pointing away from the
phthalocyanine plane (conformation B rather than C as
shown in Figure S3 in the supporting information). How-
ever, since the K1 value for 4-OHPy is also almost three
times larger than that for 3-OHPy it seems that the elec-
tronic factor plays a dominant role. The binding constants
determined for these systems are comparable with those re-
ported for other porphyrinatocobalt(II) complexes and pyr-
idine-type donor ligands.[13]
Table 1. Comparison of the binding constants.[a]
Ligand
Porphyrin
K1 [–1]
SiPc(3-OPy)2 (1)
SiPc(3-OPy)2 (1)
SiPc(4-OPy)2 (2)
SiPc(4-OPy)2 (2)
3-OHPy
Co(TPP) (3)
Co(TBPP) (4)
Co(TPP) (3)
Co(TBPP) (4)
Co(TPP) (3)
Co(TPP) (3)
(3.9Ϯ1.2)ϫ103
(4.3Ϯ0.3)ϫ103
(1.2Ϯ0.1)ϫ104
(1.1Ϯ0.2)ϫ104
(3.6Ϯ0.4)ϫ103
(1.4Ϯ0.1)ϫ104
Figure 7. UV/Vis spectrum of the binary complex 2·3 (_______) and
the addition spectrum of 2 and 3 (-----) in CHCl3. The concentra-
tions of all the species were fixed at 3.2 µ.
4-OHPy
Conclusions
[a] Determined by absorption spectroscopy in CHCl3.
In summary, the bis(pyridyl) phthalocyanines 1 and 2
serve as good building blocks for hetero phthalocyanine–
porphyrin arrays. As shown by absorption spectroscopy,
they formed 1:2 complexes with porphyrinatocobalt(II) 3
and 4 with binding constants K1 in the range of 3.9ϫ103
to 1.2ϫ104 –1. The heterodyads 2·3 and 2·4 could also be
isolated and spectroscopically characterized. It is envisaged
that this axial coordination approach can be extended to
construct larger mixed phthalocyanine–porphyrin arrays.
This work is in progress.
Because of the relatively large binding constants attempts
were made to isolate the complexed species. By stirring a
1:2 (in mole) mixture of SiPc(4-OPy)2 (2) and Co(TPP) (3)
or Co(TBPP) (4) in CHCl3 a new TLC spot with an Rf
value of ca. 0.3 in CHCl3/MeOH (v/v, 5:1) appeared. The
new products could be isolated as a blue solid by silica-gel
column chromatography using CHCl3/MeOH (v/v, 9:1) as
eluent. Mass and UV/Vis spectroscopic methods showed
that they were the binary complexes 2·3 and 2·4. The corre-
sponding ternary complexes 2·(3)2 and 2·(4)2 could not be
isolated, which is probably because of their small quantity
(the binary complexes could only be isolated in ca. 5%
yield). The MALDI-TOF mass spectra of the dyads showed
an envelope peaking at m/z = 1399.0 or 1847.7, assignable
to the corresponding molecular ion. For both signals, the
isotopic pattern was in good agreement with the simulated
spectrum. The identity of these complexes was further con-
firmed by accurate mass measurements (using ESI mass
spectrometry).
Figure 7 compares the UV/Vis spectrum of the dyad 2·3
in CHCl3 and the sum of the spectra of 2 and 3, all at the
same concentration. It can be seen that the porphyrin Soret
band is redshifted from 410 nm to 435 nm upon complex-
ation, while the absorptions of the phthalocyanine compo-
nent are essentially unchanged. Similar results were ob-
tained for the binary complex 2·4 (see Figure S4 in the Sup-
porting Information). These observations supported the
findings that the binary complexes were stable enough to
be isolated, which is in contrast to the porphyrinatozinc(II)
counterparts.[9b] Under the same conditions, the binary
complexes of the 3-pyridyl analogue 1 and the porphyrin-
atocobalt(II) complexes 3 and 4 could not be isolated,
which is in accord with their weaker binding interactions.
Experimental Section
General: Reactions were performed under nitrogen. Toluene was
distilled from sodium prior to use. N,N-Dimethylformamide
(DMF) was predried with barium oxide and distilled under reduced
pressure. The chloroform used in the UV/Vis studies was freshly
distilled from CaH2 under nitrogen. All other solvents and reagents
were used as received. Chromatographic purifications were per-
formed with silica gel (Macherey–Nagel, 70–230 mesh) columns
with the indicated eluents. Compounds 2,[9b] 3,[10a] and the metal-
free meso-tetrakis(3,5-di-tert-butylphenyl)porphyrin [H2(TBPP)][10b]
were prepared by previously described methods. 1H and 13C{1H}
NMR spectra were recorded with a Bruker DPX 300 spectrometer
(1H NMR, 300; 13C NMR, 75.4 MHz) in CDCl3. Spectra were ref-
erenced internally using the residual solvent (1H NMR: δ =
7.26 ppm) or solvent (13C NMR: δ = 77.0 ppm) resonances relative
to SiMe4. MALDI-TOF mass spectra were recorded with a Bruker
bench TOF mass spectrometer equipped with a standard UV-laser
desorption source, using α-cyano-4-hydroxycinnamic acid as the
matrix. FAB and ESI mass spectra were measured with a Thermo
Finnigan MAT 95 XL mass spectrometer. UV/Vis spectra were re-
corded with a Cary 5G spectrophotometer. Elemental analyses
were performed by the Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, China.
SiPc(3-OPy)2 (1): A mixture of dichlorosilicon(IV) phthalocyanine
(1.0 g, 1.64 mmol), 3-hydroxypyridine (0.32 g, 3.36 mmol), and pyr-
4618
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4615–4620

Bis(pyridinolato)silicon(IV) Phthalocyanines
idine (2 mL) in toluene (50 mL) was heated at reflux overnight. The
volatiles were then removed under reduced pressure and the residue
was chromatographed on a silica gel column using CHCl3/MeOH
(v/v, 9:1) as eluent to give the product as a blue solid (0.89 g, 75%).
1H NMR: δ = 9.64–9.67 (m, 8 H, Pc-Hα), 8.40–8.43 (m, 8 H, Pc-
Hβ), 6.98 (dd, J = 1.6, 4.8 Hz, 2 H, Py-H), 5.63 (dd, J = 4.8, 8.4 Hz,
2 H, Py-H), 3.92 (d, J = 1.6 Hz, 2 H, Py-H), 2.87 (d, J = 8.4 Hz,
2 H, Py-H) ppm. 13C{1H} NMR: δ = 149.7, 146.2, 139.2, 138.5,
135.2, 131.7, 125.6, 124.1, 122.0 ppm. UV/Vis (CHCl3) [λmax (log
ε)]: 354 (4.89), 614 (4.59), 654 (4.53), 684 (5.36) nm. HRMS (FAB):
calcd. for C42H25N10O2Si [MH+] 729.1931; found 729.1928.
C42H24N10O2Si·MeOH (760.85): calcd. C 67.88, H 3.71, N 18.41;
found C 67.81, H 4.01, N 18.54.
peaking at m/z =
1847.7 [M+]. HRMS (ESI): calcd. for
C118H117CoN14O2Si [MH+] 1848.8584; found 1848.8052.
X-ray Crystallographic Analysis of 1 and 2: Crystal data and details
of data collection and structure refinement are given in Table 2.
For 1, data were collected at 293 K with an MSC/Rigaku RAXIS
IIc imaging-plate system using Mo-Kα radiation (λ = 0.71073 Å)
from a Rigaku RU-200 rotating-anode generator operating at
50 kV and 90 mA (2θmin = 3°, 2θmax = 55°, 2–5° oscillation frames
in the range 0–180°, exposure 12 min per frame).[14] A self-consis-
tent semi-empirical absorption correction based on a Fourier coef-
ficient fitting of symmetry-equivalent reflections was applied by
using the ABSCOR program.[15] Crystallographic data of 2 were
collected with a Bruker SMART CCD diffractometer with a Mo-
Kα sealed tube (λ = 0.71073 Å) at 293 K, using a ω scan mode
with an increment of 0.3°. Preliminary unit-cell parameters were
obtained from 45 frames. Final unit-cell parameters were obtained
by global refinements of reflections obtained from integration of
all the frame data. The collected frames were integrated using the
preliminary cell-orientation matrix. The SMART software was
Co(TBPP) (4): A mixture of H2(TBPP) (100 mg, 0.09 mmol) and
anhydrous cobalt(II) chloride (20 mg, 0.15 mmol) in DMF (10 mL)
was stirred at 120 °C for 8 h. The cooled dark red solution was
then poured into MeOH (100 mL), and the precipitate was filtered
off and washed with MeOH. The crude product was purified by
column chromatography using CHCl3 as eluent (92 mg, 87%). UV/
Vis (CHCl3) [λmax (log ε)]: 411 (5.18), 528 (4.11) nm. HRMS (FAB): used for collecting frames of data, indexing reflections, and deter-
calcd. for C76H92CoN4 [M+] 1119.6653; found 1119.6638.
mination of lattice constants; SAINT-PLUS for the integration of
the intensity of reflections and scaling;[16] SADABS for absorption
corrections;[17] and SHELXL for space group and structure deter-
mination, refinements, graphics, and structure reporting.[18]
Heterodyad 2·3: A mixture of SiPc(4-OPy)2 (2) (20 mg, 0.03 mmol)
and Co(TPP) (3) (37 mg, 0.06 mmol) in CHCl3 (50 mL) was stirred
at room temp. overnight. After removing the solvent in vacuo the
residue was chromatographed with CHCl3/MeOH (v/v, 9:1) as elu-
ent. The third blue band was collected and evaporated to give the
product (2 mg, 5%). UV/Vis (CHCl3) [λmax (log ε)]: 355 (4.96), 435
(5.26), 553 (4.04), 618 (4.51), 686 (5.29) nm. MS (MALDI-TOF):
an isotopic cluster peaking at m/z = 1399.0 [M+]. HRMS (ESI):
calcd. for C86H53CoN14O2Si [MH+] 1400.3577; found 1400.3574.
CCDC-644806 and CCDC-644807 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see also the footnote on the first page of
this article): Absorption spectra of mixtures of SiPc(3-OPy)2 (1)
and Co(TBPP) (4) in CHCl3; different resonance structures of the
3- and 4-pyridinolato ligands; schematic diagrams showing the
complexation of SiPc(3-OPy)2 (1) with porphyrinatocobalt(II)
Heterodyad 2·4: According to the above procedure, SiPc(4-OPy)2
(2) (20 mg, 0.03 mmol) complexed with Co(TBPP) (4) (66 mg,
0.06 mmol) in CHCl3 (50 mL) to give the dyad 2·4 (3 mg, 6%). UV/
Vis (CHCl3) [λmax (log ε)]: 351 (4.95), 437 (5.33), 551 (4.13), 619 complexes. UV/Vis spectrum of the binary complex 2·4 and the
(4.52), 688 (5.28) nm. MS (MALDI-TOF): an isotopic cluster
addition spectrum of 2 and 4 in CHCl3.
Table 2. Crystallographic data for 1 and 2.
1·2C6H5NO2
2
Empirical formula
Formula mass [gmol–1]
Crystal size [mm]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C54H34N12O6Si
975.02
C42H24N10O2Si
728.80
0.25ϫ0.20ϫ0.10
monoclinic
P21/c
9.613(3)
19.394(5)
9.945(3)
90
118.599(4)
90
0.50ϫ0.40ϫ0.20
triclinic
¯
P1
8.6413(17)
11.060(2)
13.297(3)
94.96(3)
101.70(3)
110.34(3)
1149.6(4)
1
γ [°]
V [Å3]
1627.8(8)
2
Z
F(000)
504
1.408
0.120
752
1.487
0.131
Dcalcd. [mgm–3]
µ [mm–1]
θ range [°]
2.33–25.53
3613
3613
2.10–25.02
7044
2867
Reflections collected
Independent reflections
Parameters
331
250
R1 [IϾ2σ(I)]
wR2 [IϾ2σ(I)]
Goodness-of-fit on F2
Largest diff. peak and hole [eÅ–3]
0.0556
0.1541
1.067
0.350 and –0.229
0.0531
0.1138
1.038
0.318 and –0.284
Eur. J. Inorg. Chem. 2007, 4615–4620
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4619

X. Leng, D. K. P. Ng
FULL PAPER
60, 6889–6894; c) A. N. Cammidge, G. Berber, I. Chambrier,
P. W. Hough, M. J. Cook, Tetrahedron 2005, 61, 4067–4074.
[10] a) W. Mikolaiski, G. Baum, W. Massa, R. W. Hoffmann, J.
Organomet. Chem. 1989, 376, 397–405; b) S. Takagi, T. K. Mi-
yamoto, Y. Sasaki, Bull. Chem. Soc. Jpn. 1986, 59, 2371–2373.
[11] K. Hirose, J. Inclusion Phenom. Macrocycl. Chem. 2001, 39,
193–209.
Acknowledgments
This work was supported by a strategic investments scheme admin-
istered by The Chinese University of Hong Kong.
[1] The Porphyrin Handbook (Eds.: K. M. Kadish, K. M. Smith,
R. Guilard), Academic Press, San Diego, 2000, vol. 6; 2003,
vol. 14 and 19.
[12]
K. A. Connors, Binding Constants, Wiley, New York, 1987, pp.
141–160.
[13]
a) F. A. Walker, J. Am. Chem. Soc. 1973, 95, 1150–1153; b) J. S.
Summers, A. M. Stolzenberg, J. Am. Chem. Soc. 1993, 115,
10559–10567.
[2] D. Holten, D. F. Bocian, J. S. Lindsey, Acc. Chem. Res. 2002,
35, 57–69.
[3] P.-C. Lo, X. Leng, D. K. P. Ng, Coord. Chem. Rev. 2007,
doi:10.1016/j.ccr.2007.03.007.
[4] a) D. K. P. Ng, J. Jiang, Chem. Soc. Rev. 1997, 26, 433–442; b)
J. W. Buchler, D. K. P. Ng, in The Porphyrin Handbook (Eds.:
K. M. Kadish, K. M. Smith, R. Guilard), Academic Press, San
Diego, 2000, vol. 3, pp. 245–294.
[14]
a) J. Tanner, K. Krause, Rigaku J. 1994, 11, 4–7; b) J. Tanner,
K. Krause, Rigaku J. 1990, 7, 28–32; c) K. Krause, G. N. Phil-
lips Jr, J. Appl. Crystallogr. 1992, 25, 146–154; d) M. Sato, M.
Yamamoto, K. Imada, Y. Katsube, N. Tanaka, T. Higashi, J.
Appl. Crystallogr. 1992, 25, 348–357.
[5] a) B. Floris, M. P. Donzello, C. Ercolani, in The Porphyrin
Handbook (Eds.: K. M. Kadish, K. M. Smith, R. Guilard), Ac-
ademic Press, San Diego, 2003, vol. 18, pp. 1–62; b) G. Kwag,
E. Park, S. Kim, Bull. Korean Chem. Soc. 2004, 25, 298–300;
c) M. P. Donzello, L. Bartolino, C. Ercolani, C. Rizzoli, Inorg.
Chem. 2006, 45, 6988–6995.
[6] T.-H. Tran-Thi, Coord. Chem. Rev. 1997, 160, 53–91.
[7] X. Leng, C.-F. Choi, P.-C. Lo, D. K. P. Ng, Org. Lett. 2007, 9,
231–234.
[15] T. Higashi, ABSCOR – An Empirical Absorption Correction
Based on Fourier Coefficient Fitting, Rigaku Corporation, To-
kyo, 1995.
[16] SMART and SAINT for Windows NT Software Reference Man-
uals, Version 5.0, Bruker Analytical X-ray Systems, Madison,
WI, 1997.
[17] G. M. Sheldrick, SADABS – A Software for Empirical Absorp-
tion Correction, University of Göttingen, Germany, 1997.
[18] SHELXL Reference Manual, Version 5.1, Bruker Analytical X-
ray Systems, Madison, WI, 1997.
[8] Y. Kobuke, Eur. J. Inorg. Chem. 2006, 2333–2351.
[9] a) X.-y. Li, D. K. P. Ng, Eur. J. Inorg. Chem. 2000, 1845–1848;
b) M. T. M. Choi, C.-F. Choi, D. K. P. Ng, Tetrahedron 2004,
Received: April 25, 2007
Published Online: August 13, 2007
4620
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4615–4620