An unprecedented porphyrin-pillar[5]arene hybrid ditopic receptor

Article abstract of DOI:10.1039/c5ra05913e

A novel porphyrin-pillar[5]arene host compound ZnPor-P5 was designed and prepared for the first time. A 1:1 supramolecular complex (ZnPor-P5)·C4 was formed with the neutral guest 1,4-bis(imidazol-1-yl)butane (C4) depending on the cooperative interactions

Full text of DOI:10.1039/c5ra05913e

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An unprecedented porphyrin-pillar[5]arene hybrid
ditopic receptor†
Cite this: RSC Adv., 2015, 5, 43218
a
ab
a
a
a
*
*
Chenxi Liu, Chao Chen and Jianzhuang Jiang
Nana Sun, Xin Xiao,
A novel porphyrin-pillar[5]arene host compound ZnPor-P5 was designed and prepared for the first time. A
1 : 1 supramolecular complex (ZnPor-P5)$C4 was formed with the neutral guest 1,4-bis(imidazol-1-yl)-
butane (C4) depending on the cooperative interactions between the coordination of the zinc ion
locating at the center of the porphyrin moiety and the inclusion complexation of the pillar[5]arene cavity
with the guest molecule according to a range of NMR, mass, electronic absorption, and fluorescence
spectroscopic results in addition to ITC, demonstrating the ditopic receptor nature of this porphyrin-
pillar[5]arene hybrid compound. The addition of CdI2 into (ZnPor-P5)$C4 in chloroform induced the
dissociation of the guest molecule from the zinc ion locating at the center of the porphyrin moiety due
Received 2nd April 2015
Accepted 6th May 2015
DOI: 10.1039/c5ra05913e
to the stronger coordination of imidazole with Cd2+ than with the zinc ion, yielding
a new
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supramolecular system ZnPor-(P5)$C4$Cd with a different conformation.
and other supramolecular systems12 with fascinating properties
and application potentials have been developed. However, the
pillarene-based ditopic receptors and in particular the
pillarene-containing hetero-ditopic receptors still remain
extremely rare. In 2013, Huang used pillar[5]arene and crown
ether to construct a dynamic [1]catenane showing pH-respon-
siveness.13 In 2014, Wen and co-workers constructed a bicyclic
host molecule using pillar[5]arene and crown ether with its two
cyclic subunits selectively recognizing two different guest
molecules.14 Obviously, novel pillarene-based ditopic receptors
with interesting supramolecular system formation properties
are highly desired for the purpose of mimicking the biological
recognition events.
It is well known that porphyrins are of signicant biological
importance and widely used in supramolecular chemistry to
mimic the porphyrin-containing active sites of proteins and
enzymes.15 In addition to the large number of metal porphyrin
monotopic receptors usually with the central metal ion as the
sole biding site,16 cyclodextrins,17 crown ethers,18 and calix[4]-
arenas19 were also incorporated onto the porphyrin periphery as
additional binding site, resulting in a number of porphyrin-
containing ditopic receptors. However, pillar[n]arene-
containing porphyrin-based ditopic receptor still remains
unreported thus far, to the best of our knowledge.
Introduction
Oligo- and multitopic receptors are omnipresent in nature
because multivalent binding1 and cooperative binding2 are two
major concepts to ensure the necessary efficiency and selectivity
in biological recognition events as well as the complicated
cascades of processes coupled to these events. Due to different
binding sites employed for the receptors to the substrate, the
receptors usually exhibit different conformational changes
upon binding with different guests.3 Such kinds of conforma-
tional changes in biological systems have been well employed to
control the function of proteins and enzymes during cellular
metabolism.4 As a result, a conformational change of the host
upon binding with different guest and/or external stimulation
has attracted increasing research interests in supramolecular
chemistry in the past three decades through the development of
various kinds of articial ditopic and multitopic receptor
systems based on crown ether,5 cyclodextrin,6 calixarene,7 and
cucurbit[n]uril8 macrocyclic hosts.
Pillar[n]arenes, as a new class of supramolecular host
system, have also received considerable attention since their
rst synthesis in 2008.9 Thanks to their excellent host-guest
binding ability with a number of guests, different pillar[n]-
arenes-based supramolecular polymers,10 functional vesicles,11
In the present paper, we describe the preparation and
characterization of unprecedented porphyrin-pillar[5]arene
host compound ZnPor-P5. This novel hybrid compound forms
a stable 1 : 1 supramolecular complex (ZnPor-P5)$C4 with
neutral guest 1,4-bis(imidazol-1-yl)butane (C4) depending on
the cooperative interactions between the coordination of zinc
ion locating at the center of porphyrin moiety and the inclusion
complexation of the pillar[5]arene cavity with the guest
aBeijing Key Laboratory for Science and Application of Functional Molecular and
Crystalline Materials, Department of Chemistry, University of Science and
Technology Beijing, Beijing, 100083, China. E-mail: jianzhuang@ustb.edu.cn
bKey Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province,
Guizhou University, Guiyang, 550025, China
† Electronic supplementary information (ESI) available: NMR, MALDI-TOF mass
spectrum, electronic absorption and uorescence spectra for ZnPor-P5. See DOI:
10.1039/c5ra05913e
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molecule according to a range of NMR, mass, electronic
absorption, and uorescence spectroscopic results in addition
to ITC, demonstrating the ditopic receptor nature of this
porphyrin-pillar[5]arene hybrid compound. Addition of CdI2
into (ZnPor-P5)$C4 in chloroform induces the dissociation of
the guest molecule from the zinc ion locating at the center of
porphyrin moiety due to the stronger coordination of imidazole
with Cd2+ than with zinc ion, leading to a new supramolecular
system ZnPor-(P5)$C4$Cd with different conformation.
NMR spectroscopy
The complexation of ZnPor-P5 with the guest C4 was rst
studied by 1H NMR spectroscopy. For comparative study, the
host-guest complexation between P5 and Zn(TTBP) with C4 was
also investigated.
As shown in Fig. S5 (ESI†), the 1H NMR spectrum of the guest
C4 in CDCl3 experiences obvious change upon the addition of
the host P5, indicating the effective host-guest interaction
between the two species. The signals for the methylene protons
of C4 exhibit substantial upeld shi in comparison with the
free guest C4 due to the shielding effect of the electron-rich
cavities of P5 (Dd ¼ ꢀ2.48 and ꢀ2.92 ppm for Hd and He,
respectively, Fig. S5 (ESI†)). Meanwhile, the signals correspond-
ing to the protons Ha and Hc of the imidazole moiety attributed
to C4 also experience pronounced upeld shi, and the proton
Hb takes a slight downeld shi. The above results revealed that
the alkyl chain protons and partial iminazole protons of guest C4
were threaded into the cavity of P5 forming pseudorotaxane,9e
Fig. S5 (ESI†). This is also true for host molecule Zn(TTBP). As
shown in Fig. S6 (ESI†), upon adding Zn(TTBP) into the solution
of C4 in CDCl3, the resonances of all the protons for C4 undergo
signicant upeld shi due to the intense shielding effect from
the porphyrin ring current, revealing the coordination between
zinc ion locating at the center of porphyrin and the N atom of
one of the two imidazole units in C4.
Results and discussion
Synthesis and characterization
Reaction of bromobutyl bis-substituted pillar[5]arene with the
hydroxyl group of H2(TTBP) promoted by K2CO3 and KI in DMF
led to the formation of unprecedented porphyrin-pillar[5]arene
hybrid compound H2Por-P5, which further reacted with
Zn(OAc)2 in chloroform afforded the zinc complex ZnPor-P5,
Scheme 1. Satisfactory elemental analysis result was obtained
for this newly prepared porphyrin-functionalized pillar[5]arene
derivative aer repeated column chromatography. Its MALDI-
TOF mass spectrum displayed intense signal at m/z
¼
1774.42, corresponding to the molecular ion [M]+. Nevertheless,
this compound was further characterized with a range of
spectroscopic methods including NMR, electronic absorption,
and uorescence spectroscopy in addition to elemental anal-
ysis, Fig. S1–S4, (ESI†).
As can be expected, when adding the two active centers host
compound ZnPor-P5 into the solution of guest C4 in CDCl3,
inclusion complexation of one of the two imidazole units with
the pillar[5]arene cavity moiety, and coordination between the
nitrogen atom of the remaining imidazole unit of C4 and the
central zinc ion locating at the porphyrin moiety take place
simultaneously, resulting in signicant changes in the 1H NMR
spectrum of the guest C4, Fig. 1.
It is worth noting that during the past few years, pillar[n]-
arenes have been recognized as an exceptionally versatile host
for a wide variety of guests. Although the initial studies
primarily focused on the cationic species,20 the host-guest
complexation of pillar[n]arene derivatives with neutral guests
like bis(imidazole) derivatives in organic media has also
However, compared to the situation for mixing the guest C4
with single active center host P5/Zn(TTBP), the chemical shis
received considerable attention in recent years.21 As
a
consequence, in the present case the neutral molecule
1,4-bis(imidazol-1-yl)butane (C4) was selected as the guest to
establish the binding relationship with the hybrid host
compound ZnPor-P5.
Fig. 1 1H NMR spectra of C4 in CDCl3 at 25 ꢁC upon addition of
ZnPor-P5 with the molar ratio of ZnPor-P5 and C4 changing from (A)
Scheme 1 Schematic molecular structures of the host ZnPor-P5 and pure C4, (B) 0.1, (C) 0.2, (D) 0.4, (E) 0.6, (F) 0.8, (G) 1.0, and (H) pure
guest C4.
ZnPor-P5.
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due to the protons of ZnPor-P5 host also experience signicant
changes, Fig. 1, suggesting the enhanced interaction between
the guest and host molecule due to the cooperative interactions
between the coordination of zinc ion locating at the center of
porphyrin moiety and the inclusion complexation of the pillar
[5]arene cavity moiety with the guest molecule C4. The above
information also demonstrates the ditopic receptor nature of
this novel porphyrin-pillar[5]arene hybrid compound.
Electronic absorption and uorescence spectroscopy
Both the electronic absorption and uorescence emission
spectroscopy were utilized to collect additional information
about the host-guest interaction between ZnPor-P5 and C4.
According to the electronic absorption spectroscopic results,
Fig. 3, upon gradual addition of guest C4 into ZnPor-P5 at a
xed concentration of 2.0 ꢃ 10ꢀ6 M in CHCl3, the porphyrin
Soret absorption underwent bathochromic shi from 422 to
433 nm due to the formation of supramolecular complex
(ZnPor-P5)$C4. A sharp isosbestic point appears at 427 nm,
which veries the 1 : 1 stoichiometry of host with guest and
allows the determination of the association constants (Ka) by
applying a non-linear curve-tting method. The association
constant Ka, (5.02 ꢂ 0.50) ꢃ 104 Mꢀ1, thus deduced is consistent
with that deduced from the ITC analysis as detailed above,
Fig. 2. Further support for this point comes from the uores-
cence spectroscopic result with the observation of decrease in
the emission intensity, accompanied by a 13 nm bathochromic
shi due to the porphyrin Q band, aer gradually adding guest
C4 into the solution of ZnPor-P5, Fig. S10, (ESI†).
Mass spectrometry
MALDI-TOF mass spectroscopic result provides further
evidence for the supramolecular complex formed between
ZnPor-P5 and C4. Observation of the major signal at m/z ¼
1964.28, corresponding to (ZnPor-P5)$C4 (calculated 1964.60),
in the MALDI-TOF MS spectrum, Fig. S8 (ESI†), directly
conrms the formation of this 1 : 1 supramolecular complex.
Isothermal titration calorimetry
Isothermal titration calorimetry (ITC) measurements are able to
give the quantitative information for the host-guest complex
including both the binding affinity and thermodynamic origin.
As a result, a solution of C4 (1.0 mM) was consecutively at 25 ꢁC
to record the exothermic binding isotherm, Fig. 2, resulting in
the resolution of the binding molar ratio value of N ¼ 1.041.
This result is very much close to the expected value of 1.0,
indicating the binding stoichiometry is 1 : 1 between ZnPor-P5
and C4. In addition, the association constant of Ka ¼ (6.83 ꢂ
0.23) ꢃ 104 Mꢀ1 was also afforded on the basis of the experi-
mental result. Such a high binding constant suggests the rela-
tively strong host-guest interaction between ZnPor-P5 and C4
due to the cooperative interactions between coordination and
inclusion complexation as detailed above, indicating the
construction of stable supramolecular system. Meanwhile, the
relatively large negative enthalpy value of (ZnPor-P5)$C4 reveals
that the assembly process of supramolecular complex of ZnPor-
P5 with C4 is typically driven by a favorable enthalpy change,
Table S1, (ESI†).
Supramolecular complex mediated by Cd2+
Due to the stronger coordination ability of imidazole with Cd2+
than with the zinc ion,22 as shown in Fig. 4, upon addition of
Fig. 3 Electronic absorption spectra of ZnPor-P5 (2 ꢃ 10ꢀ6 M) upon
addition of C4 in CHCl3 at 25 ꢁC with the C4/ZnPor-P5 molar ratio
changing from 0 to 25. Arrows indicate the absorbance change along
with increasing the guest concentration (Inset: the isosbestic point
appears at 427 nm) (A). According to the plot of DA vs. C4/ZnPor-P5 at
422 nm, the non-linear fitting curve gives the association constant Ka
¼ (5.02 ꢂ 0.50) ꢃ 104 Mꢀ1 and the correlation coefficient of R2
¼
Fig. 2 ITC data for the binding of ZnPor-P5 with C4 in CHCl3 at 25 ꢁC. 0.99518, where R2 was used to judge the fit to the date (B).
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(ZnPor-P5)$C4 system, the electronic absorption and uores-
cence spectra completely recovered to the state of the ZnPor-P5
system, conrming the dissociation of coordination between
zinc ion locating at the center of porphyrin moiety and one
imidazole unit of guest C4 in (ZnPor-P5)$C4 system, Fig. 5 and
S13, (ESI†).
Binding mode of ZnPor-P5 with C4
Briey summarizing above, according to the above-described
NMR, mass, electronic absorption, and uorescence spectra
as well as ITC results, ZnPor-P5 provides two binding sites,
namely the pillar[5]arene cavity moiety and zinc site locating at
the center of porphyrin moiety, to efficiently bind with the
neutral guest C4 molecule and form inclusion complex.
However, the alkyl chain that links pillar[5]arene moiety and
porphyrin moiety in the host (ZnPor-P5) molecule has to be bent
to some degree to simultaneously accommodate the ditopic
binding of (ZnPor-P5) with C4 molecule using both binding
sites due to the shorter length of the guest molecule, Fig. 6.
Nevertheless, adding Cd2+ into the supramolecular system in
CHCl3 results in the dissociation of the guest C4 molecule from
the zinc site, accompanied by the cavity of pillar[5]arence site
still bound with the guest molecule, leading to the alkyl chain
that links the pillar[5]arene moiety and porphyrin moiety in the
host molecule stretching back to the original conformation of
ZnPor-P5 before forming the supramolecular complex with C4,
Fig. 6.
Fig. 4 1H NMR spectra of (H2Por-P5)$C4 (A), upon addition of 1.0
equiv. Cd2+ to the solution of (ZnPor-P5)$C4 (B), and (ZnPor-P5)$C4
(C) recorded in CDCl3 at 25 ꢁC.
At the end of this section, it is worth noting that despite
numerous attempts, all the efforts thus far paid failed to grow
X-ray quality single crystals of the supramolecular complex. As a
result, molecular modeling was employed to provide the
supramolecular architecture information by density functional
theory (DFT) calculations at the B3LYP/6-31G (D, P) level, Fig. 6.
Fig.
5 Electronic absorption spectra of (ZnPor-P5)$C4 with the
C4/ZnPor-P5 molar ratio of 25 recorded in CHCl3 at 25 ꢁC, upon
addition of Cd2+ with the Cd2+/C4 molar ratio changing from 0 to 0.5,
0.6, 0.7, 1.0.
CdI2 into the (ZnPor-P5)$C4 supramolecular complex in CDCl3,
the protons Hd and He of methylene moieties in the supramo-
lecular complex take downeld shi from ꢀ1.73 and ꢀ2.36 ppm
to ꢀ1.01 and ꢀ1.27 ppm, respectively, indicating the dissocia-
tion of coordination between zinc ion locating at the center of
porphyrin moiety and one of the two imidazole units of guest C4
in (ZnPor-P5)$C4 system, accompanied by the formation of a
new supramolecular system ZnPor-(P5)$C4$Cd with the guest
C4 only bound into the pillar[5]arene cavity of the ditopic
receptor ZnPor-P5. Further support for this point comes from
the electronic absorption and uorescence spectroscopic
results. Upon addition of CdI2 into the above-mentioned
Fig. 6 The low-energy molecular conformations of (ZnPor-P5)$C4
and ZnPor-(P5)$C4$Cd obtained by density functional theory (DFT)
calculations at the B3LYP/6-31G (D, P) level with all the hydrogen
atoms omitted for clarity.
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etherate (1.5 mL) under nitrogen atmosphere at room temper-
ature. The solution was then stirred for 4 h. The solution was
precipitated by adding CH3OH. Aer the solid was ltered off,
the residue was puried by ash column chromatography on
silica gel with CH2Cl2/CH3OH (300/1, n/n) as eluent to afford P5
as a white solid with the yield of 300.0 mg, 12.6%. 1H NMR
(400 MHz, CDCl3, 25 ꢁC): d ¼ 6.78 (m, 10H), 3.77 (m, 14H), 3.66
(s, 24H), 3.21 (t, 4H), 1.81 (m, 8H). MS calcd. for C51H60O10Br2:
992.83; found: m/z 993.34. Anal. calcd. for C51H60O10Br2: C,
61.70; H, 6.09; found C, 61.71; H,5.98.
Conclusions
In conclusion, novel hybrid ditopic receptor with pillar[5]arene
and porphyrin covalently linked with alkyl chain was designed
and prepared for the rst time, which forms a stable supra-
molecular complex with neutral guest C4 depending on the
cooperative interactions between the coordination of zinc ion
locating at the center of porphyrin moiety and the inclusion
complexation of the pillar[5]arene cavity with the guest C4
molecule. Addition of Cd2+ into the supramolecular complex
leads to the dissociation of the guest molecule from the zinc site
locating at the center of porphyrin moiety, yielding a new
supramolecular system with different conformation.
Preparation of H2(TTBP). 4-Tert-butylbenzaldehyde (1.6 g,
9.9 mmol), 4-hydroxybenzaldehyde (0.40 g, 3.3 mmol), and
pyrrole (0.89 g, 0.91 mL, 13.2 mmol) were dissolved in propionic
acid (300 mL) and purged with nitrogen whilst stirring for
30 min. The mixture was stirring for 1 h under nitrogen atmo-
sphere at 150 ꢁC. The solvent was removed under reduced
pressure and the crude product was subjected to silica gel
column chromatography using CH2Cl2. Aer removing the
solvent with rotary evaporator, a purple solid was obtained with
Experimental section
General remarks
All reagents were obtained from commercial sources without
further purication. The compounds of metal free 5-(p-hydrox-
ylphenyl)-10,15,20-tris(4-tert-butylphenyl)porphyrin H2(TTBP),
its zinc complex Zn(TTBP), and bromobutyl bis-substituted
pillar[5]arene (P5) were prepared according to the published
procedures.12d,23
1
ꢁ
264.0 mg, 10%. H NMR (400 MHz, CDCl3, 25 C): d ¼ ꢀ2.75
(s, 2H, NH), 1.61 (s, 27H, CH3),7.20 (d, J ¼ 8.0 Hz, 2H, Ar), 7.75
(d, J ¼ 8.0 Hz, 6H, Ar), 8.07 (d, J ¼ 8.0 Hz, 2H, Ar), 8.14 (d, J ¼ 8.0
Hz, 6H, Ar), 8.87 (m, 8H, pyrrole)ppm. MS calcd. for C56H54N4O:
799.05; found: m/z 799.62. Anal. calcd. for C56H54N4O: C, 84.17;
H, 6.81; N,7.01; found C, 84.09; H, 6.92; N, 7.13. UV/vis [in
CHCl3, lmax/nm (log 3)]: 421 (5.64), 518 (4.19), 554 (3.96), 593
(3.66), 649 (3.65).
Measurements
1H NMR spectra were recorded on a Bruker DPX 400 spec-
trometer in CDCl3 and DMSO-d6. Electronic absorption spectra
were recorded on a Hitachi U-4100 spectrophotometer. Steady-
state uorescence spectroscopic studies were performed on an
F4500 (Hitachi). MALDI-TOF mass spectra were taken on a
Bruker BIFLEX III ultra-high resolution Fourier transform ion
cyclotron resonance (FT-ICR) mass spectrometer with a-cyano-
4-hydroxycinnamic acid as matrix. Elemental analysis was per-
formed on an Elementar Vavio El III. Titration experiments were
Preparation of Zn(TTBP). Zn(OAc)2$2H2O (1.7 g, 8.0 mmol)
was added into a solution of 3 (0.32 g, 0.40 mmol) in CHCl3/
CH3OH (2/1, v/v, 100 mL), and the mixture was stirred at room
temperature for 24 h (along with a gradual color change from
dark purple to pink-purple). The metalation progress was
monitored by UV-vis spectroscopy. The solution was diluted
with CHCl3 and washed with saturated NaHCO3 and water. The
organic layer was dried with MgSO4, and the solvent was
removed. The residue was puried by ash column chroma-
tography on silica gel using CH2Cl2 as eluent to afford Zn(TTBP)
as a pink solid with the yield of 335.0 mg, 97%. 1H NMR
ꢁ
carried out on a ITC200 from Microcal Inc. at 25 C.
Synthetic procedures
Preparation of 1,4-bis(4-bromobutoxy)benzene. In a 500 mL (400 MHz, CDCl3, 25 ꢁC): d ¼ 1.62 (s, 27H, CH3), 7.20 (d, J ¼ 8.0
three round-bottom ask, a mixture of anhydrous potassium Hz, 2H, Ar), 7.75 (d, J ¼ 8.0 Hz, 6H, Ar), 8.08 (d, J ¼ 8.0 Hz, 2H,
carbonate (30.0 g, 0.22 mol), 1,4-dibromobutane (216.0 g, Ar), 8.14 (d, J ¼ 8.0 Hz, 6H, Ar), 8.97 (m, 8H, pyrrole) ppm. MS
1.0 mol), KI (1.0 g, 6.0 mmol) were added into dry DMF Calcd. for C56H52N4OZn: 862.45; found: m/z 862.46. Anal. calcd.
(250 mL), and then hydroquinone (11.0 g, 0.1 mol) was added for C56H52N4OZn: C, 77.99; H, 6.08; N, 6.50; found C, 77.91; H,
dropwise into the solution under nitrogen atmosphere at 65 ꢁC. 6.14; N, 6.62. UV/vis [in CHCl3, lmax/nm (log 3)]: 422 (5.80), 550
The reaction mixture was stirred for 72 h. Aer the solid was (4.38), 587 (3.77).
ltered off, the solvent was removed. The residue was precipi-
Preparation of H2Por-P5. In a 500 mL three round-bottom
tated by the mixed solvent CH3OH and H2O (3/2, v/v) to afford ask, a mixture of anhydrous potassium carbonate (304.1 mg,
1,4-bis(4-bromobutoxy)benzene as a white solid with the yield of 2.2 mmol), 3 (120 mg, 0.15 mmol), KI (30.0 mg, 0.18 mmol) are
24.7 g, 65.0%. 1H NMR (400 MHz, CDCl3, 25 ꢁC): d ¼ 6.76 (d, J ¼ added into the dry mixed solvent 1,4-dioxane and DMF (3/1, v/v),
20 Hz, 4H), 3.92 (t, J ¼ 12 Hz, 4H), 3.46 (t, J ¼ 16 Hz, 4H), 2.02 and then 2 (49.6 mg, 0.05 mmol) was added into the solution
(m, 4H), 1.86 (m, 4H). Anal. calcd. for C14H20O2Br2: C, 44.24; H, under nitrogen atmosphere at 65 ꢁC. The reaction mixture was
5.30; found C, 43.98; H, 5.41.
stirred for 72 h. Aer the solid was ltered off, the solvent was
Preparation of P5. A mixture of 1,4-dimethoxybenzene (1.3 g, removed. The residue was puried by ash column chroma-
9.6 mmol), 1,4-bis(4-bromobutoxy)benzene (0.9 g, 2.4 mmol), tography on silica gel and gelatum gel to afford H2Por-P5 as a
paraformaldehyde (0.51 g, 17.0 mmol) in 1,2-dichloromethane black red solid with the yield of 15.0 mg, 17.5%. 1H NMR
was stirred about 15 min under nitrogen atmosphere at room (400 MHz, CDCl3, 25 ꢁC): d ¼ ꢀ2.76 (s, 2H), 1.62 (m, 29H), 2.27
temperature. To which was added the boron triuoride diethyl (m, 6H), 3.64 (m, 2H), 3.88 (m, 36H), 4.09 (m, 2H), 4.44 (m, 2H),
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6.82 (m, 10H), 7.26 (d, J ¼ 8.0 Hz, 2H, Ar), 7.76 (d, J ¼ 4.0 Hz, 6H,
Ar), 8.14 (d, J ¼ 16.0 Hz, 8H, Ar), 8.93 (m, 8H, pyrrole) ppm. MS
calcd. for C107H113N4O11Br: 1710.97; found: m/z 1710.81. Anal.
calcd. for C107H113N4O11Br: C, 75.11; H, 6.66; N, 3.27; found C,
75.22; H, 6.58; N, 3.18. UV/vis [in CHCl3, lmax/nm (log 3)]: 422
(5.68), 518 (4.25), 554 (4.04), 593 (3.78), 649 (3.73).
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and R. M. Strongin, Acc. Chem. Res., 2009, 42, 1489; (i)
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5 (a) P. D. Beer and A. S. Rothin, Polyhedron, 1988, 7, 137; (b)
P. D. Beer and S. E. Stokes, Polyhedron, 1995, 14, 2631; (c)
Preparation of ZnPor-P5. Zn(OAc)2$2H2O (88.0 mg,
0.4 mmol) was added to a solution of H2Por-P5 (34.2 mg,
0.02 mmol) in CHCl3/CH3OH (2/1, v/v, 100 mL), and the mixture
was stirred at room temperature for 24 h (along with gradual
color change from dark purple to pink-purple). The metalation
progress was monitored by UV-vis spectroscopy. The solution
was diluted with CHCl3 and washed with saturated NaHCO3 and
water. The organic layer was dried with MgSO4, and the solvent
was removed. The residue was puried by ash column chro-
matography on silica gel using CH2Cl2 to afford ZnPor-P5 as a
´
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1
pink solid with the yield of 34.4 mg, 97%. H NMR (400 MHz,
CDCl3, 25 ꢁC): d ¼ 1.62 (m, 29H), 2.03 (m, 6H), 3.02 (t, 2H),
3.60 (m, 36H), 4.10 (m, 2H), 4.30 (m, 2H), 6.67 (m, 10H), 7.26
(2H, Ar), 7.75 (d, J ¼ 8.0 Hz, 6H, Ar), 8.14 (d, J ¼ 8.0 Hz, 8H, Ar),
8.97 (m, 8H, pyrrole) ppm. MS calcd. for C107H111N4O11BrZn:
1774.36; found: m/z 1774.42. Anal. calcd. for C107H111N4O11
-
BrZn: C, 72.43; H, 6.31; N, 3.16; found C, 72.35; H, 6.41; N, 3.18.
UV/vis [in CHCl3, lmax/nm (log 3)]: 423 (5.73), 550(4.34), 589
(3.80).
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Acknowledgements
Financial support from the National Key Basic Research
Program of China (Grant nos 2013CB933402 and
2012CB224801), Natural Science Foundation of China, Beijing
Municipal Commission of Education, and University of Science
and Technology Beijing is gratefully acknowledged.
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