Zinc-induced fluorescence enhancement of the 5,10-porphodimethene-type thiophene-containing calixphyrins

Article abstract of DOI:10.1080/10426501003773431

The synthesis, structure, and electrochemical/optical properties of the zinc complexes of 5,10-porphodimethene-type thiophene-containing (S,N ₃-) and phosphole-containing (P,N₃-) calixphyrins are reported. The S,N₃- and P,N₃-calixphyrin free bases react with zinc(II) salts to give the corresponding zinc complexes in good yields. The S,N₃-calixphyrin-ZnI complex adopts a distorted square pyramidal geometry, with the S and N atoms at the basal positions. The S,N ₃-calixphyrin-ZnX complexes emit red fluorescence with fluorescent quantum yields up to 23%, whereas the P,N₃-calixphyrin-ZnCl complex is weakly fluorescent. Among the first-row transition metals (Fe²⁺, Cu²⁺, and Zn²⁺) examined, the chelation-enhanced fluorescence is observed specifically for the Zn²⁺ ion. These results indicate that the 5,10-porphodimethene-type S,N₃-hybrid calixphyrin is a promising turn-on fluorescent probe for Zn²⁺ sensing. Copyright Taylor & Francis Group.

Full text of DOI:10.1080/10426501003773431

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Phosphorus, Sulfur, and Silicon and the
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Zinc-Induced Fluorescence Enhancement
of the 5,10-Porphodimethene-Type
Thiophene-Containing Calixphyrins
Yoshihiro Matano a , Masato Fujita a , Tooru Miyajima a & Hiroshi
Imahori a b c
a Department of Molecular Engineering, Graduate School of
Engineering , Kyoto University , Kyoto, Japan
b Institute for Integrated Cell-Material Sciences (iCeMS) , Kyoto
University , Kyoto, Japan
c Fukui Institute for Fundamental Chemistry , Kyoto University ,
Kyoto, Japan
Published online: 27 May 2010.
To cite this article: Yoshihiro Matano , Masato Fujita , Tooru Miyajima & Hiroshi Imahori (2010)
Zinc-Induced Fluorescence Enhancement of the 5,10-Porphodimethene-Type Thiophene-Containing
Calixphyrins, Phosphorus, Sulfur, and Silicon and the Related Elements, 185:5-6, 1098-1107, DOI:
10.1080/10426501003773431
To link to this article: http://dx.doi.org/10.1080/10426501003773431
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Phosphorus, Sulfur, and Silicon, 185:1098–1107, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003773431
ZINC-INDUCED FLUORESCENCE ENHANCEMENT
OF THE 5,10-PORPHODIMETHENE-TYPE
THIOPHENE-CONTAINING CALIXPHYRINS
Yoshihiro Matano,1 Masato Fujita,1 Tooru Miyajima,1
and Hiroshi Imahori1–3
1Department of Molecular Engineering, Graduate School of Engineering,
Kyoto University, Kyoto, Japan
2Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University,
Kyoto, Japan
3Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto, Japan
The synthesis, structure, and electrochemical/optical properties of the zinc complexes of
5,10-porphodimethene-type thiophene-containing (S,N3-) and phosphole-containing (P,N3-)
calixphyrins are reported. The S,N3- and P,N3-calixphyrin free bases react with zinc(II) salts
to give the corresponding zinc complexes in good yields. The S,N3-calixphyrin–ZnI complex
adopts a distorted square pyramidal geometry, with the S and N atoms at the basal posi-
tions. The S,N3-calixphyrin–ZnX complexes emit red fluorescence with fluorescent quantum
yields up to 23%, whereas the P,N3-calixphyrin–ZnCl complex is weakly fluorescent. Among
the first-row transition metals (Fe2+, Cu2+, and Zn2+) examined, the chelation-enhanced
fluorescence is observed specifically for the Zn2+ ion. These results indicate that the 5,10-
porphodimethene-type S,N3-hybrid calixphyrin is a promising turn-on fluorescent probe for
Zn2+ sensing.
Keywords Calixphyrin; chelation; fluorescence; thiophene; zinc
INTRODUCTION
Calixphyrins1 are a class of reduced porphyrin analogs involving both sp2- and
sp3-hybridized bridging meso carbon atoms. According to the number of sp3-hybridized
carbons, calixphyrins are divided to porphomethenes, porphodimethenes, and por-
photrimethenes, all of which possess reasonably flexible frameworks as well as rather
rigid π-conjugated networks. Due to this structural diversity, the calixphyrin family has
attracted increasing attention in coordination chemistry and supramolecular chemistry.2
Received 6 December 2008; accepted 13 January 2009.
Dedicated to Professor Naomichi Furukawa on the occasion of his 70th birthday.
This work was supported by a Grant-in-Aid for Science Research on Priority Areas (No. 20036028, Synergy
of Elements) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We thank Prof.
Yoshifumi Kimura (Kyoto University), Dr. Kengo Suzuki (Hamamatsu Photonics K.K.), and Dr. Takahiro Sasamori
(Kyoto University) for the measurements and analyses of fluorescence lifetimes, an absolute fluorescence quantum
yield, and X-ray crystal structures of 5a, respectively.
Address correspondence to Yoshihiro Matano, Department of Molecular Engineering, Graduate School of
Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan. E-mail: matano@scl.kyoto-u.ac.jp
1098

HYBRID CALIXPHYRIN–ZINC COMPLEXES
1099
X
X
Cl
N
N
NH
HN
N
N
N
N
Zn
N
H
N
H
N
S
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
1P (X = PPh)
1S (X = S)
2P (X = PPh)
2S (X = S)
3
4
Figure 1 Core-modified 5,10-porphodimethenes reported by us3 and by Huang et al.5
We have recently reported the first examples of the 5,10-porphodimethene-type hybrid
calixphyrins containing phosphole and/or thiophene rings3 and disclosed the coordination
properties of P,X,N2-hybrid calixphyrins including 1P and 2P (Figure 1) with palladium,
rhodium, and gold salts.3a,b It is noteworthy that the oxidation state, charge, and catalytic
activity at the metal center as well as the optical and electrochemical properties of the
complexes vary significantly depending on the combination of the π-conjugated heterole
units. In contrast to the P,X,N2-hybrids 1P and 2P, however, the S,X,N2-hybrids 1S
and 2S did not produce complexes with the above transition metals, probably due to
the weak coordinating property of the thiophene unit as compared to the phosphole
unit.3c
In 2008, Huang et al. reported that m-benziporphodimethene4 behaved as a long-
wavelength Zn2+ specific chemosensor.5 Interestingly, compound 3 shows fluorescence
switch-on upon Zn2+ binding with no apparent background fluorescence. Huang et al.’s
findings represent the important role of the rigid and coplanar π-conjugated tripyrrin unit
chelating to the central zinc ion of 4 in exhibiting strong emission. With this encourag-
ing result in mind, we aimed to investigate the coordination chemistry of the thiophene-
and phosphole-containing core-modified calixphyrins with Zn2+ ions and to reveal the
effects of the core substituents on their light-emitting ability. In this article, we report
the synthesis, structure, and electrochemical/optical properties of zinc complexes of the
5,10-porphodimethene-type S,N3- and P,N3-hybrid calixphyrins. It has been found that the
efficiency of chelation-enhanced fluorescence is intrinsically dependent on the combination
of heterole components of the calixphyrin platforms. The S,N3-calixphyrin–zinc(II) com-
plexes exhibit intense red fluorescence, whereas the P,N3-calixphyrin–zinc(II) complex is
weakly fluorescent.
RESULTS AND DISCUSSION
Thiophene- and phosphole-containing hybrid calixphyrins 1S, 1P, and 2S were pre-
pared according to the reported procedure.3 As depicted in Figure 1, the oxidation states
and the available charges of the π-conjugated tripyrrin units of 1S and 2S differ from
each other; 1S is regarded as a monoanionic ligand with the 16π network, whereas 2S is
a dianionic ligand with the 14π network.6 The reaction of 1S with ZnCl2 in the presence
of slight excess 2,6-lutidine in CH2Cl2–MeCN proceeded instantaneously at room tem-
perature to give S,N3-calixphyrin–ZnCl complex 5a in 93% isolated yield. Similarly, 1S
underwent complexation with ZnBr2, ZnI2, Zn(OAc)2, and Zn(OCOCF3)2 in the presence

1100
Y. MATANO ET AL.
of 2,6-lutidine to give the corresponding ZnX complexes 5b–e (X = Br, I, OAc, OCOCF3)
in 62–82% isolated yields. When the S2,N2-type free base 2S was used in place of 1S, no
reaction took place with Zn(OAc)2. These results imply that the coordination behavior of
the core-modified calixphyrins is deeply related to the components of the tripyrrin units.
The P,N3-type free base 1P reacted with ZnCl2 in the presence of 2,6-lutidine to give
P,N3-calixphyrin–ZnCl complex 6 in 87% yield (Scheme 1).
S
X
ZnX2, 2,6-lutidine
1S
Zn
N
N
N
CH2Cl2–MeCN
Ph
Ph
5a (X = Cl; 93%)
5b (X = Br; 62%)
5c (X = I; 68%)
5d (X = OAc; 77%)
5e (X = OCOCF3; 82%)
P
Cl
Ph
N
ZnCl2, 2,6-lutidine
CH2Cl2–MeCN
1P
Zn
N
N
Ph
Ph
6 (87%)
Scheme 1
All the zinc complexes 5a–e and 6 are air-stable, dark blue or purple solids, and are
soluble in common organic solvents such as CH2Cl2, CHCl3, THF, toluene, and MeCN. The
structures of 5a–e and 6 were characterized by NMR spectroscopy and mass spectrometry.
Complex 5a displays one set of pyrrole-β protons at δ 6.19 (s, 2H), 6.65 (d, 2H), and
6.80 (d, 2H) as sharp peaks. Complexes 5b and 5d show their pyrrole-β protons at almost
the same resonance frequencies as those of 5a, implying that the axial anions (X) do not
significantly influence the magnetic and electronic environments of the tripyrrin unit. On
the other hand, 5c, 5e, and 6 exhibit two sets of pyrrole-β protons at slightly different
frequencies in CDCl3, suggesting that two diastereomers are present in solution. It seems
likely that in 5c, 5e, and 6, the apical ligands coordinate to the zinc center from both sides
of the macrocyclic planes (vide infra).7 In the mass spectra, fragment ions ([M–X]+) were
observed as the most intense peaks.
The structures of 5a and 5c were further elucidated by X-ray crystallography. Recrys-
tallization of 5c from CH2Cl2–hexane afforded single crystals of one of the diastereomers.
The top and side views of 5c are depicted in Figure 2 with selected bond lengths and
bond angles.8 The zinc center adopts a square pyramidal geometry coordinated by a sulfur

HYBRID CALIXPHYRIN–ZINC COMPLEXES
1101
Figure 2 Top and side views of 5c (30% probability ellipsoids). Hydrogen atoms and dichloromethane are
omitted for clarity. Selected bond lengths (Å) and bond angles (deg): Zn I, 2.4703(9); Zn N(1), 2.162(5);
Zn N(2), 2.007(5); Zn N(3), 2.170(5); Zn S, 2.6724(16); S Zn N(1), 82.40(14); S Zn N(3), 78.97(14);
N(2) Zn N(1), 90.4(2); N(2) Zn N(3), 91.73(19); I Zn N(1), 101.64(14); I Zn N(2), 110.95(16);
I
Zn N(3), 102.83(14).
atom and three nitrogen atoms at the basal positions. Due to the S-to-Zn coordination, the
thiophene ring is inclined toward a mean tripyrrin plane with a dihedral angle of 67.4◦, and
the iodine atom is located on the same side of the thiophene-fused trimethylene unit with a
relatively short Zn-I distance [2.4703(9) Å]. The Zn N distances of 5c [2.007(5)–2.170(5)
Å] are comparable to those of Huang et al.’s ZnCl complex 4 [1.995(4)–2.130(4) Å]. The
calixphyrin platform of 5c displays a ruffled structure, and the zinc atom is displaced
above the mean plane composed of the basal four heteroatoms by 0.61 Å with the sum
of X Zn Y bond angles (X = S, N2; Y = N1, N3) of 343.5◦. As a consequence, the
π-conjugated tripyrrin unit in 5c is slightly distorted with dihedral angles of 0.3–10.6◦. The
C C bond alternation at the tripyrrin units observed for 5c (Table I) reasonably explains
a significant contribution of the canonical structures depicted in bold lines in Scheme 1.
Table I Selected bond lengths (Å) and dihedral angles (deg) of 5c
S
a
c
a'
c'
I
b
b'
Zn
N
N
N
d
d'
e
e'
Ph
Ph
f
f'
g
a, aꢁ
1.444(9), 1.448(9)
1.333(10), 1.356(9)
1.443(8), 1.445(9)
1.365(8), 1.386(8)
176.2(7), 169.4(6)
179.7(7), 176.3(7)
e, eꢁ
f, fꢁ
g
1.419(8), 1.419(9)
1.423(8), 1.430(8)
1.377(10)
b, bꢁ
c, cꢁ
d, dꢁ
c–d–e, cꢁ–dꢁ–eꢁ
d–e–f, dꢁ–eꢁ–fꢁ

1102
Y. MATANO ET AL.
Table II Reduction potentials and optical properties of 5a–e and 6a
b
Complex
Ered
λabs/nmc
log ε
λem/nmd
ꢀf
5a
5b
5c
5d
5e
6
−0.76
−0.78
−0.75
−0.78
−0.78
N. D.g
632
633
634
632
633
618
4.52
4.51
4.52
4.50
4.52
4.53
661
662
662
661
663
656
0.22e
0.15f
0.12f
0.23f
0.22f
0.002f
aMeasured in CH2Cl2.
bReduction potentials vs. Fc∗/Fc∗+
cThe longest absorption maxima.
dExcited at 580 nm.
.
eAbsolute fluorescence quantum yield determined by a calibrated integrating sphere system.
fFluorescence quantum yield relative to 5a.
gNot determined.
The observed structural features of 5a are close to those of 5c, although the quality of
diffraction data for 5a is not satisfactory. We have not succeeded in obtaining good single
crystals of 6 so far.
To reveal apical-ligand effects on the electronic properties of the hybrid calixphyrin
platforms, we measured electrochemical reduction processes of 5a–e by cyclic voltammetry
(CV) and differential pulse voltammetry (DPV). All the complexes showed reversible
voltammograms in the CV measurements. As summarized in Table II, the electrochemical
reduction occurred at almost the same potentials (Ered = −0.75 to −0.78 V vs. Fc∗/Fc∗+
;
Fc∗ = decamethylferrocene, determined by DPV), suggesting that the apical ligands do not
perturb the LUMO level significantly. The Ered values of 5a–e are shifted to the positive side
by comparison with that of the free base 1S (Ered = −0.93 V vs. Fc∗/Fc∗+). Presumably, the
Lewis acidic Zn2+ center enhances the electron-accepting ability of the S,N3-calixphyrin
platform.
To disclose the optical properties of the S,N3- and P,N3-calixphyrin–zinc com-
plexes, we measured UV-vis absorption and fluorescence spectra of 5a–e and 6 in solution
(Table II). The ZnCl complex 5a displays intense, broad absorptions with absorption max-
ima at λabs 348, 585, and 632 nm in CH2Cl2 and at λabs 345, 580, and 624 nm in MeCN,
due to π–π∗ transitions of the tripyrrin unit. The zinc coordination induces a bathochromic
shift of the lowest transition band by 92 nm (λabs = 540 nm for 1S to λabs = 632 nm for 5a
in CH2Cl2). The spectral shape and extinction coefficients of 5b–e are very close to those of
5a, suggesting that the character of π–π∗ transitions is little perturbed by the apical ligands
in the S,N3-calixphyrin–ZnX complexes. The P,N3-calixphyrin–ZnCl complex 6 shows
absorption bands at λabs 354 and 618 nm in CH2Cl2 and at λabs 351 and 612 nm in MeCN.
The longest λabs values of 5a and 6 in MeCN are appreciably blue-shifted as compared to
those of 4 (λabs 350, 593, and 639 nm in MeCN), indicating that the coordination of the
sp3-carbon-bridged heteroles influences on the electronic properties of the π-conjugated
tripyrrin unit. The basal coordination of S (5a) and P (6) atoms to the zinc center may cause
a deviation from planarity of the tripyrrin unit.
The most diagnostic spectral feature of 5a–e is their highly fluorescent nature
(Table II). In CH2Cl2, the ZnCl complex 5a emits red fluorescence at λem = 661 nm
(λex = 580 nm) with a fluorescence quantum yield (ꢀf) of 0.22. In MeCN, the emission

HYBRID CALIXPHYRIN–ZINC COMPLEXES
1103
is observed at 656 nm, which is blue-shifted by 16 nm compared to that observed for
Huang et al.’s ZnCl complex 4 (λem = 672 nm in MeCN). The ꢀf value of 5a is somewhat
smaller than the reported value of 4 (ꢀf = 0.34) but much larger than that of 5,10,15,20-
tetraphenylporphyrinatozinc(II) (ꢀf = 0.033).9 The ꢀf values of 5a–e vary from 0.12 to
0.23 depending on the nature of apical ligands. Among the halides 5a–c, the chloride 5a
shows the most intense fluorescence. In contrast to 5a–e, the P,N3-calixphyrin ZnCl com-
plex 6 emits very weak fluorescence (ꢀf = 0.002). These results represent an important
role of the sp3-carbon-bridged heterole units in displaying chelation-induced fluorescence.
It is worth mentioning that the S,N3-hybrid free base 1S is nonfluorescent. In this context,
1S is regarded as a new fluorescence turn-on probe for Zn2+ ion.10
To get more insight into the photophysical properties, fluorescence lifetimes (τf) of
5a, 5b, and 5d in CH2Cl2 were determined.11 The fluorescence decays were well fit by the
single exponential component, and τs values were determined to be 4.4 ns (5a), 3.0 ns (5b),
and 4.3 ns (5d). Based on the observed ꢀf and τs values, fluorescence decay rate constants
(kf) of 5a, 5b, and 5d were calculated to be 5.0 × 107 s−1, 5.0 × 107 s−1, and 5.3 × 107 s−1
,
respectively. These data imply that the difference in τs values among 5a, 5b, and 5d is
basically ascribable to the difference in rate constants of nonradiative processes from their
S1 states.
To evaluate the binding ability of 1S as a fluorescent probe for sensing Zn2+ ion,
spectrophotometric titration measurements were performed for the complexation of 1S
with ZnCl2 or Zn(OAc)2. As shown in Figure 3, adding ZnCl2 (7.0 × 10−3 M in MeOH; 1–
20 µL) into a red solution of 1S (2.3 × 10−5 M in CH2Cl2; 3 mL) in the presence of
2,6-lutidine changed the spectral shape with isosbestic points at λ = 430 and 562 nm
in the visible region. With increasing the concentration of Zn2+ ion, the fluorescence
intensity increased. At a saturated condition (in the presence of 1.5 equiv of Zn2+ ion),
the absorption and fluorescence spectra are identical to those independently observed
for 5d. Similar spectral changes were observed for the titration with Zn(OAc)2. The 1:1
complexation between 1S and Zn(OAc)2 was further confirmed by a Job plot. To evaluate
the coordinating ability of 1S toward other transition metals, the titration measurements
were also examined with Fe2+ and Cu2+ ions. Addition of a MeOH solution of FeCl2 or
CuCl2 to a CH2Cl2 solution of 1S (2.3 × 10−5 M) in the presence of 2,6-luridine changed
Figure 3 UV-vis absorption spectra (left) and fluorescence spectra (right, λex = 580 nm) observed for the
titration measurements of 1S (2.3 × 10−5 M in CH2Cl2) with ZnCl2 (7.0 × 10−3 M in MeOH) in the presence of
2,6-lutidine. [Zn2+] = 0, 0.3, 0.5, 0.8, 1.0, 1.2, 1.5 equiv vs. [1S].

1104
Y. MATANO ET AL.
its spectrum with isosbestic points at λ = 438 and 566 nm for Fe2+ and at λ = 438 and
569 nm for Cu2+. The resulting spectra suggested the formation of S,N3-calixphyrin–iron
(λabs = 351 and 645 nm) and –copper (λabs = 356, and 652 nm) complexes. In these
complexations, however, almost no fluorescence (ꢀf < 0.001) was detected, even at the
saturated conditions, probably due to the paramagnetic effects. These results indicate that 1S
is an efficient fluorescence Zn2+ sensor emitting an intense red light. It should be mentioned
again that 1P does not show such a chelation-enhanced fluorescence. It is therefore likely
that the core-modification of calixphyrin platforms impacts on the light-emitting ability of
the Zn-coordinated tripyrrin π system.
In summary, we have revealed that the 5,10-porphodimethene-type S,N3- and P,N3-
calixphyrins coordinate effectively to Zn2+ ions in solution. The S,N3-calixphyrin–ZnX
complexes have been found to adopt a distorted square pyramidal geometry with S and
N atoms at the basal positions and the anionic ligands at the apical position. Most im-
portantly, the coordination of zinc(II) has proven to dramatically increase the fluorescence
intensity of the S,N3-calixphyrin chromophores and to barely perturb the P,N3-calixphyrin
chromophore. The efficiency of the chelation-enhanced fluorescence also depends on the
transition metals coordinated at the core and is selective to Zn2+ among Fe2+, Cu2+, and
Zn2+ ions. The present results demonstrate that the 5,10-porphodimethene-type S,N3-hybrid
calixphyrin could be a promising turn-on fluorescent probe for Zn2+ sensing.
EXPERIMENTAL
1
1H and 31P{ H} NMR spectra were recorded on a JEOL EX-400 or a JEOL AL300
spectrometer using CDCl3 as a solvent. Chemical shifts are reported as the relative values vs.
tetramethylsilane (1H) or phosphoric acid (31P). Matrix-assisted laser desorption/ionization
(MALDI) time-of-flight mass spectra (TOF) were measured on a Shimadzu AXIMA-CFR
spectrometer using α-cyano-4-hydroxycinnamic acid as a matrix. High-resolution mass
spectra (HRMS) were recorded on a JEOL JMS-HX 110A spectrometer (FAB) using
3-nitrobenzylic alcohol as a matrix or a JEOL JMS-700 MStation spectrometer (EI). Elec-
trochemical measurements (CV and DPV) were performed on a BAS 50 W electrochemical
workstation using a glassy carbon working electrode, a platinum wire counter electrode, and
an Ag/Ag+ [0.01 M AgNO3, 0.1 M n-Bu4NPF6 (MeCN)] reference electrode. The potentials
+
were calibrated with FeCp∗ /FeCp∗ [Emid = −0.37 V vs Ag/AgNO3]. UV-vis absorp-
2
2
tion and steady-state fluorescence spectra were measured using a Perkin-Elmer Lambda
900 UV/vis/NIR spectrometer and a SPEX Fluoromax-3 spectrofluorometer, respectively.
Spectroscopy grade CH2Cl2 and MeCN was used for the measurements of UV-visible
absorption and fluorescence spectra. Free bases 1S, 1P, and 2S were prepared according
to the reported procedures.3 Dichloromethane was distilled from calcium hydride under
inert atmosphere before use. Other chemicals and solvents were of reagent grade quality,
purchased commercially and used without further purification. Thin-layer chromatography
and flash column chromatography were performed with Alt. 5554 DC-Alufolien Kieselgel
60 F254 (Merck) and Silica-gel 60N (Kanto Chemicals), respectively. All the reactions were
performed under an argon atmosphere unless otherwise stated.
Synthesis of 5
2,6-Lutidine (ca. 10 µL) was added to a mixture of 1S (15 mg, 0.026 mmol), ZnX2
(0.031 mmol), CH2Cl2 (2 mL), and MeCN (3 mL), and the resulting blue solution was

HYBRID CALIXPHYRIN–ZINC COMPLEXES
1105
stirred for 30 min at room temperature. The reaction mixture was then concentrated under
reduced pressure to leave a solid residue, to which CH2Cl2 (10 mL) and water (10 mL)
were added. The organic phase was separated, and the aqueous phase was extracted with
CH2Cl2 until the blue color of the organic extracts disappeared. The combined organic
extracts were dried over MgSO4 and evaporated under reduced pressure to leave a solid
residue, which was reprecipitated from cold hexane at low temperatures to afford S,N3-ZnX
complex 5 as a blue to purple solid in high purity. When 1P was used as the free base, the
P,N3-calixphyrin–ZnCl complex 6 was obtained in 87% yield as a dark blue solid.
1
5a: Mp 244–245◦C; H NMR (CDCl3, 400 MHz) δ 1.72 (s, 6H; Me), 1.93 (s, 6H;
Me), 2.26–2.33 (m, 1H; CH2), 2.42–2.52 (m, 1H; CH2), 2.70–2.89 (m, 4H; CH2), 6.19 (s,
2H; pyrrole-β), 6.65 (d, 2H, J = 4.4 Hz; pyrrole-β), 6.80 (d, 2H, J = 4.4 Hz; pyrrole-β),
7.33–7.47 (m, 10H; Ph); UV-vis (CH2Cl2) λabs (ε): 348 (30800), 585 (17400), 632 (32900);
HRMS (EI): Calcd for C39H34ClN3SZn (M+), 675.1453; Found, 675.1454; Anal. Calcd
for C39H34ClN3SZn•(CH2Cl2)0.5: C, 65.88; H, 4.90; N, 5.84. Found: C, 66.06; H, 5.05; N,
5.84.
1
5b: Mp > 300◦C; H NMR (CDCl3, 400 MHz) δ 1.72 (s, 6H; Me), 1.94 (s, 6H;
Me), 2.24–2.35 (m, 1H; CH2), 2.42–2.52 (m, 1H; CH2), 2.70–2.92 (m, 4H; CH2), 6.21 (s,
2H; pyrrole-β), 6.65 (d, 2H, J = 4.6 Hz; pyrrole-β), 6.82 (d, 2H, J = 4.6 Hz; pyrrole-β),
7.30–7.47 (m, 10H; Ph); UV-vis (CH2Cl2) λabs (ε): 349 (31400), 586 (17300), 633 (32600);
HRMS (FAB): Calcd for C39H34BrN3SZn (M+), 719.0948; Found, 719.0923.
5c: This complex was obtained as a mixture of two diastereomers (A/B = 9/1). Mp >
1
300◦C; H NMR (diastereomer A: CDCl3, 400 MHz) δ 1.71 (s, 6H; Me), 1.94 (s, 6H;
Me), 2.24–2.36 (m, 1H; CH2), 2.40–2.56 (m, 1H; CH2), 2.73–2.93 (m, 4H; CH2), 6.23 (s,
2H; pyrrole-β), 6.65 (d, 2H, J = 4.9 Hz; pyrrole-β), 6.85 (d, 2H, J = 4.9 Hz; pyrrole-β),
7.30–7.50 (m, 10H; Ph); 1H NMR (diastereomer B: CDCl3, 400 MHz) δ 1.71 (s, 6H; Me),
1.94 (s, 6H; Me), 2.24–2.36 (m, 1H; CH2), 2.40–2.56 (m, 1H; CH2), 2.73–2.93 (m, 4H;
CH2), 6.19 (s, 2H; pyrrole-β), 6.65 (d, 2H, J = 4.6 Hz; pyrrole-β), 6.80 (d, 2H, J = 4.6 Hz;
pyrrole-β), 7.30–7.50 (m, 10H; Ph); UV-vis (CH2Cl2) λabs (ε): 350 (31500), 588 (17700),
634 (33300); MS (FAB) m/z 640 ([M–I]+).
1
5d: Mp 173–174◦C; H NMR (CDCl3, 400 MHz) δ 1.57 (s, 3H; Me), 1.72 (s, 6H;
Me), 1.93 (s, 6H; Me), 2.24–2.36 (m, 1H; CH2), 2.42–2.52 (m, 1H; CH2), 2.72–2.91 (m,
4H; CH2), 6.19 (s, 2H; pyrrole-β), 6.65 (d, 2H, J = 4.6 Hz; pyrrole-β), 6.80 (d, 2H, J =
4.6 Hz; pyrrole-β), 7.33–7.50 (m, 10H; Ph); UV-vis (CH2Cl2) λabs (ε): 348 (31000), 586
(17000), 632 (31900); MS (FAB) m/z 640 ([M–OAc]+).
5e: This complex was obtained as a mixture of two diastereomers (A/B = 2/1). Mp
1
209–210◦C; H NMR (diastereomer A: CDCl3, 400 MHz) δ 1.72 (s, 6H; Me), 1.93 (s,
6H; Me), 2.25–2.53 (m, 2H; CH2), 2.66–2.92 (m, 4H; CH2), 6.19 (s, 2H; pyrrole-β), 6.65
(d, 2H, J = 4.6 Hz; pyrrole-β), 6.80 (d, 2H, J = 4.6 Hz; pyrrole-β), 7.34–7.50 (m, 10H;
1
Ph); H NMR (diastereomer B: CDCl3, 400 MHz) δ 1.72 (s, 6H; Me), 1.90 (s, 6H; Me),
2.25–2.53 (m, 2H; CH2), 2.66–2.92 (m, 4H; CH2), 6.22 (s, 2H; pyrrole-β), 6.65 (d, 2H,
J = 4.6 Hz; pyrrole-β), 6.82 (d, 2H, J = 4.6 Hz; pyrrole-β), 7.34–7.50 (m, 10H; Ph);
UV-vis (CH2Cl2) λabs (ε): 349 (32300), 588 (17700), 633 (32800); HRMS (FAB): Calcd
for C41H34O2N3F3SZn (M+), 753.1615; Found, 753.1578.
6: This complex was obtained as a mixture of two diastereomers (A/B = 3/2).
1
Mp > 300◦C; H NMR (diastereomer A: CDCl3, 400 MHz) δ 1.19 (s, 6H; Me), 1.73 (s,
6H; Me), 2.05–2.45 (m, 2H; CH2), 2.62–2.95 (m, 4H; CH2), 6.29 (s, 2H; pyrrole-β), 6.52
(d, 2H, J = 4.6 Hz; pyrrole-β), 6.84 (d, 2H, J = 4.6 Hz; pyrrole-β), 7.19–7.56 (m, 15H;
1
Ph); H NMR (diastereomer B: CDCl3, 400 MHz) δ 1.18 (s, 6H; Me), 1.85 (s, 6H; Me),

1106
Y. MATANO ET AL.
2.26–2.33 (m, 2H; CH2), 2.62–2.95 (m, 4H; CH2), 6.28 (s, 2H; pyrrole-β), 6.48 (d, 2H, J =
1
4.4 Hz; pyrrole-β), 6.72 (d, 2H, J = 4.4 Hz; pyrrole-β), 7.19–7.56 (m, 15H; Ph); 31P{ H}
NMR (diastereomer A and B: CDCl3, 162MHz) δ 29.4 and 21.2; UV-vis (CH2Cl2) λabs (ε):
354 (30600), 618 (33900); MS (FAB) m/z 716 ([M–Cl]+).
X-Ray Crystal Crystallographic Analysis
Single crystals of 5a and 5c were grown from CH2Cl2–hexane at room tempera-
ture. All measurements were made on a Rigaku Saturn CCD area detector with graphite
monochromated Mo–Kα radiation. The structures were solved by direct methods12 and ex-
panded using Fourier techniques.13 Nonhydrogen atoms were refined anisotropically, and
hydrogen atoms were refined using the rigid model. All calculations were performed using
the CrystalStructure crystallographic software package14 except for refinement, which was
performed using SHELXL-97.15 Although the crystallographic data for 5a are not at the
publishable level, its structure was confirmed by X-ray crystallography. CCDC No. 715502
for 5c contains the supplementary crystallographic data for this article. These data can be
obtained free of charge via the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB21EZ, UK (fax: (+44)1223–336-033; e-mail: deposit@ccdc.cam.ac.uk).
Fluorescence Lifetime Measurements of 5a, 5b, and 5d
The fluorescence lifetimes were measured in CH2Cl2 using a streak camera as a
fluorescence detector. All samples were excited by the second harmonic output (400 nm)
from the amplified Ti:Sapphire laser system.
Titration Measurements of 1S with Transition Metal Salts
A CH2Cl2 solution of 1S (2.3 × 10−5 M; 3 mL) was charged in a quartz cuvette
(pass length = 1 cm), and a MeOH solution of ZnCl2 (7.0 × 10−3 M in MeOH) was added
in portions (0.3, 0.5, 0.8, 1.0, 1.2, 1.5 equiv vs. [1S]). At each step, the absorption and
fluorescence spectra were measured, and the results are shown in Figure 3. The titration
measurements of 1S with Zn(OAc)2, FeCl2, and CuCl2 were examined according to a similar
procedure. The incorporation of the respective metals was confirmed by MS spectrometry,
although the resulting complexes were not isolated. The fragment ion peaks ([M–Cl]+) are
as follows: m/z = 632 (for 1S–Fe complex) and 639 (for 1S–Cu complex).
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