Synthesis, structures, optical and electrochemical properties, and complexation of 2,5-bis(pyrrol-2-yl)phospholes

Article abstract of DOI:10.1016/j.crci.2010.03.017

2,5-Bis(pyrrol-2-yl)phosphole derivatives were prepared using the reaction of titanacycles, generated in situ from a Ti^II reagent and pyrrole-capped 1,6-heptadiynes, with dichloro(phenyl)phosphine. The 2,5-bis(pyrrol-2-yl)phosphole derivatives

Full text of DOI:10.1016/j.crci.2010.03.017

C. R. Chimie 13 (2010) 1035–1047
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´
Full paper/Memoire
Synthesis, structures, optical and electrochemical properties, and
complexation of 2,5-bis(pyrrol-2-yl)phospholes
a
a
a,b,c
Yoshihiro Matano a, , Masato Fujita , Arihiro Saito , Hiroshi Imahori
*
a Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
b Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
c Fukui Institute for Fundamental Chemistry, Kyoto University, Sakyo-ku, Kyoto 606-8103, Japan
A R T I C L E I N F O
A B S T R A C T
Article history:
2,5-Bis(pyrrol-2-yl)phosphole derivatives were prepared using the reaction of titana-
cycles, generated in situ from a TiII reagent and pyrrole-capped 1,6-heptadiynes, with
dichloro(phenyl)phosphine. The 2,5-bis(pyrrol-2-yl)phosphole derivatives were found to
possess narrower optical HOMO–LUMO gaps and less positive oxidation potentials than
those of previously reported 2,5-diarylphosphole analogs. This demonstrates that the
Received 30 January 2010
Accepted after revision 18 March 2010
Available online 8 May 2010
Keywords:
intrinsic nature of the electron excessive pyrrole subunits as well as the effective
p-
conjugation over the coplanar heterole rings. The s3-P type 2,5-bis(5-phenylpyrrol-2-
yl)phosphole underwent complexation with AuCl(SMe2) and PtCl2 to yield the respective
AuCl–monophosphine and PtCl2–bisphosphine complexes. In the square planar PtII
complex, the pyrrolic NH protons were found to form intramolecular hydrogen bonds with
Phosphorus heterocycles
Nitrogen heterocycles
Metallacycles
Gold
Platinum
the chlorine atoms that gave rise to symmetrically split, parallel
p-chromophores linked
by two Pt–P bonds. Density functional theory calculations on a PtII model complex
suggested that this cooperative interaction induces a significant split of the original
LUMOs of the symmetrical
p-conjugated ligands.
´
ß 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
of type
phenylene) [2], pyridine (2-pyridyl) [3], and thiophene
(2-thienyl, 3-thienyl, etc) [4] moieties as the -substitu-
A compounds include benzene (phenyl or
Phosphole, the phosphorus analog of pyrrole, possesses
a
a low-lying LUMO due to effective
s
*–
p
* orbital interac-
ents, where synergetic effects derived from each compo-
nent have been exhibited in the optical and
tion between the phosphorus center and the polarizable
1,3-diene unit. In addition, the LUMO and HOMO energy
levels of phosphole can be controlled by chemical
functionalizations at the phosphorus center. These char-
acteristic properties of phosphole are beneficial for the
construction of unprecedented classes of optical and
electrochemical properties of the entire
p-systems. It is
well known that HOMO of pyrrole is located at a higher
energy level than HOMOs of benzene, thiophene, and
pyridine.1 In this regard, pyrrole–phosphole–pyrrole
p-
systems are expected to release electrons easily as
compared with known arene–phosphole–arene hybrids
of type A. Such properties would be promising to construct
electronic materials [1]. In fact, phosphole-linked
conjugated systems of general formula A have recently
p-
received increasing attention, and their fundamental
a new class of redox active hybrid heterole p-systems. It is
properties have proven to depend strongly on the
p
-
also anticipated that pyrrolic NH groups may act as
conjugative substituents. Most of the preceding examples
1
HOMO energies of pyrrole, benzene, thiophene, pyridine, and
* Corresponding author.
phosphole calculated at B3LYP/6-31G* level are ꢀ5.48, ꢀ6.70, ꢀ6.33,
ꢀ6.87, and ꢀ6.25 eV, respectively.
E-mail address: matano@scl.kyoto-u.ac.jp (Y. Matano).
1631-0748/$ – see front matter ß 2010 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2010.03.017

1036
Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
hydrogen-bond donors toward Lewis basic functions
attached to the phosphorus center. To our knowledge,
solid in 28% yield based on 2b, whereas the a-free
derivative 4a was difficult to completely purify due to
its instability in atmospheric environment. Therefore, 4a
was used for subsequent transformations without isola-
however, the utilization of pyrrole as the
a-substituent has
gained quite a little attention in phosphole chemistry [5].2
In 2006, we established a convenient method for the
synthesis of
a0-difunctionalized phospholes via titana-
cycles generated from Sato-Urabe’s TiII reagent [6] and the
corresponding terminal-substituted 1,6-heptadiynes
[7,8].3 This protocol has proven to be effective for the
construction of arene-capped phosphole–vinylene [9],
phosphole–acetylene [10], and phosphole–triazole [11]
tion. On treatment with hydrogen peroxide or m-chlor-
operbenzoic acid (mCPBA), each s3-phosphorus center of
4a,b was readily oxygenated, affording the corresponding
P-oxides 5a,b. When treated with elemental sulfur, 4a,b
were converted to P-sulfides 6a,b.
The pyrrole–phosphole–pyrrole hybrids 3–6 were
characterized by conventional spectroscopic techniques
(1H, 13C, 31P NMR, high-resolution MS, IR) and elemental
analysis. Although 4a gradually decomposed in solution,
its structure was confirmed by NMR spectroscopy and MS
spectrometry. The 31P peaks of the s4 derivatives 6a,b (dP
63.4, 63.6) and 5a,b (dP 54.3, 55.6) were observed at
a
,
p
-systems with characteristic properties derived from the
respective components. Herein, we report a new short-
step synthesis of 2,5-bis(pyrrol-2-yl)phosphole derivatives
based on the titanacycle protocol and their optical,
electrochemical, and coordinating properties. In this study,
we aimed to elucidate the characteristic features of the
pyrrole substituents by comparison with those of the other
arene substituents in type A phosphole derivatives. Both
experimental and theoretical results demonstrate that the
attachment of the pyrrole substituents is highly promising
downfield compared to those of 4a,b (dP 28.1, 28.5), which
clearly reflects differences in the electronic character and
the oxidation state of phosphorus. In the 1H NMR spectra,
3–6 showed only one set of pyrrolic CH and NH protons,
indicating that all of these compounds have Cs symmetry
for developing a new class of
p
-conjugated phosphole
in solution. The NH protons of
and 6a appeared at 8.01, 9.09, and 9.61, respectively. The
same holds true for series of the phenyl-capped
derivatives 4b ( 8.26), 5b ( 9.28), and 6b ( 9.96).
Judging from the downfield appearance of the NH peaks of
5 and 6 relative to those of 4 and free pyrrole ( 8.0), there
a,
a0-free derivatives 4a, 5a,
derivatives with multiple functions derived from these two
group 15 heteroles.
d
a
d
d
d
2. Results and discussion
d
may exist hydrogen-bonding interaction between the NH
protons and the chalcogen atoms bound to phosphorus in 5
and 6. To get some insight into relative conformation
between the pyrrole and phosphole rings in solution, we
also measured NOESY spectra for 4b and 5b in CD2Cl2. In
2.1. Synthesis of 2,5-bis(pyrrol-2-yl)phosphole derivatives
Scheme 1 illustrates the synthesis of 2,5-bis(pyrrol-2-
yl)phosphole derivatives and 2,5-bis(5-phenylpyrrol-2-
yl)phosphole derivatives. The starting materials, pyrro-
lyl-capped 1,6-heptadiynes 2a,b, were prepared by Sono-
gashira coupling of terminal-free 1,6-heptadiyne and the
corresponding 1-Boc-2-iodopyrroles (Boc = t-butoxycar-
both cases, the NH proton and one of the b-CH protons of
the pyrrole ring show nuclear Overhauser effects (NOE)
toward allylic methylene protons of the trimethylene
bridge fused to the phosphole ring. This result implies that
bonyl) 1a,b [12,13]. Reactions of 2a and 2b with (h2
-
0
the inter-ring C –C bonds between pyrrole and phosp-
propene)Ti(Oi-Pr)2, generated in situ from Ti(Oi-Pr)4 and 2
equiv of i-PrMgCl [6], followed by treatment with PhPCl2
gave N-Boc-protected 2,5-bis(pyrrol-2-yl)phosphole 3a
(43%) and 2,5-bis(5-phenylpyrrol-2-yl)phosphole 3b, re-
spectively. Compound 3b could not be separated from
unreacted 2b and was used as a mixture in the following N-
Boc deprotection step. The N-Boc groups of 3a,b were
successfully removed by the reaction with sodium
methoxide in methanol to give s3 derivatives 4a,b. The
phenyl-capped derivative 4b was isolated as an air stable
a
a
hole rings rotate rapidly in solution on the NMR timescale.
In the IR spectra of 5a and 5b, P O stretching frequencies
were observed at
value of 5a is somewhat smaller than that
n
1165 and 1180 cmꢀ1, respectively. The
nP
O
(
nP O = 1178 cmꢀ1) of a similar trimethylene-fused 2,5-
diphenylphosphole P–oxide [14].4
The crystal structure of 5b was elucidated by X-ray
crystallography. The ORTEP diagram is shown in Fig. 1 with
selected bond lengths and bond angles. The phosphorus
center forms a tetrahedral geometry with average C–P–C
and C–P–O angles of 101.98 and 116.48, respectively. The
2
In 1998, Mathey et al. reported the synthesis of 2-(1-methyl-2-
pyrrolyl)phospholes via a base-promoted [1,5]-sigmatropic shift of the
pyrrolyl group from the phosphorus atom to the
a carbon.
3
4
Tomita et al. and Tanaka et al. used a similar protocol for the synthesis
of phosphole–phenylene copolymers and phosphole-cored dendrimers,
respectively.
Optical data (lab/nm, lem/nm, and Ff; measured in CH2Cl2) for 3,4-
trimethylene-1,2,5-triphenylphosphole P–oxide are 386, 491, and 0.19,
respectively.

Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
1037
Scheme 1.
C–C bond length alternation of the phosphole subunit
differs considerably from that of two pyrrole subunits,
which reflects the difference in aromaticity between these
two kinds of heterole rings. The relatively narrow dihedral
angles between the central phosphole and adjacent pyrrole
rings (4.7–18.38) indicate efficient
p-conjugation through
the pyrrole–phosphole–pyrrole linkage. As for the stereo-
chemistry at the inter-ring bonds, one pyrrole ring adopts
an S-trans (anti) conformation against the phosphole ring,
whereas the other adopts an S-cis (syn) conformation. The
N(2)–H group of the syn pyrrole ring is directed to the P–
˚
oxo group with NꢁꢁꢁO distance of 3.20 A, indicating that
weak hydrogen-bonding interaction is present between
the NH proton and the oxygen atom in 5b [15].5 The P
O
˚
distance of 1.4871(11) A is almost identical to that
˚
[1.489(1) A] of Tanaka’s 2,5-diphenyl-1-phenylphosphole
P–oxide [16].
2.2. Optical and electrochemical properties of 2,5-bis(pyrrol-
2-yl)phosphole derivatives
Fig. 1. Top view (upper) and side view (lower) of 5b (30% probability
To investigate the optical and electrochemical proper-
ellipsoids). Hydrogen atoms except for NH are omitted for clarity.
ties of
hole–pyrrole
a, a,
a0-free and a0-phenyl-capped pyrrole–phosp-
˚
Selected bond lengths (A) and angles (deg): C(1)–C(2), 1.375(2); C(2)–
C(3), 1.411(2); C(3)–C(4), 1.387(2); C(4)–C(5), 1.431(2); C(5)–C(6),
1.362(2); C(6)–C(7), 1.466(2); C(7)–C(8), 1.356(2); C(8)–C(9),
1.4394(19); C(9)–C(10), 1.386(2); C(10)–C(11), 1.406(2); C(11)–C(12),
1.380(2); P–C(5), 1.8116(15); P–C(8), 1.8019(15); P–C(16), 1.8061(16);
P–O, 1.4871(11); C(5)–P–C(8), 94.35(7); C(5)–P–C(16), 105.41(7); C(8)–
P–C(16), 105.80(7); C(5)–P–O, 120.34(7); C(8)–P–O, 116.75(7); C(16)–P–
O, 112.00(7).
p-systems, we measured UV-vis absorption
and fluorescence spectra and redox potentials of 4–6 in
5
The N–O distances for typical NH–O hydrogen bonds were reported to
˚
˚
be ca. 3 A (max 3.25 A).

1038
Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
Table 1
Optical and electrochemical data for 4a,b, 5a,b, 6a,b, 7, and trans-8a.
Compound
l
ab/nmb (log
e)
l
em/nm (Ff
)
Eox/Ve,f
4a
416 (n.d.)g
459 (4.54)
458 (4.22)
506 (4.38)
454 (4.24)
507 (4.36)
504 (4.48)
506 (n.d.)g
536 (0.78)c
n.d.g
4b
ꢀ0.07 (r), +0.22 (r)
+0.20 (ir)
5a
581 (0.002)d
620 (0.002)d
576 (0.01)d
5b
+0.12 (r), +0.44 (r)
+0.22 (ir)
6a
6b
607 (0.02)d
606 (0.09)d
+0.14 (r), +0.38 (r)
n.d.g
n.d.g
7
trans-8
450 (4.36), 533 (4.40)
Non-fluorescent
a
Measured in CH2Cl2.
b
The longest absorption maxima.
c
d
e
f
Absolute fluorescence quantum yield.
Fluorescence quantum yield relative to 4b.
Redox potentials (vs. Fc/Fc+) determined by DPV. For details, see Experimental section.
r: reversible; ir: irreversible.
g
Not determined.
CH2Cl2. The results are summarized in Table 1 and Fig. 2. In
the absorption spectra, the
a0-free derivatives 4a, 5a, and
6a display the lowest * transitions at ab 416, 458, and
454 nm, respectively. As typically observed for phosphole
derivatives, chemical functionalizations at the phosphorus
center from s3 to s4 induce red-shifts of lab values
lyte in CH2Cl2 (Table 1). Although reduction processes
were not observed in the measurement window (ꢀ2.6 V
to +1.0 V vs. Fc/Fc+), oxidation processes were observed
a,
p
–p
l
for all compounds examined. The a,
a0-free derivatives 5a
and 6a showed irreversible voltammograms accompa-
nied by deposition of insoluble substances, whereas the
a,
a0-phenyl-capped derivatives 4b, 5b, and 6b showed
(Dlab = 38–42 nm). The same trend was observed for the
phenyl-capped series, 4b, 5b, and 6b (Dlab = 47–48 nm).
The s3 derivatives 4a,b are fluorescent, whereas the s4
derivatives 5a,b and 6a,b are weakly fluorescent. Notably,
4b emits intense yellowish green fluorescence at lem
two reversible oxidation processes in CV measurements.
In the cases of 5a and 6a, subsequent chemical reactions
such as an electropolymerization may occur at the a-free
pyrrole rings when electrochemically oxidized. The P-
functionalizations (from 4b to 5b and 6b) make a definite
impact on the first and second oxidation processes, both
of which are shifted to lower potentials by 0.16–0.22 V. It
is worthy to note that the electrochemical oxidations of
4, 5, and 6 occur at much lower potentials than those
reported for related 2,5-diarylphospholes (aryl = 2-thie-
nyl, phenyl, 2-pyridyl).8 For instance, the difference in
the first oxidation potentials between 5a and 2,5-
diphenylphosphole P–oxide [14] of the same trimethy-
lene-fused type reaches 1 V. These experimental results
demonstrate that the pyrrole components play a key role
in fine-tuning of the redox properties, especially elec-
trochemical oxidation properties, of type A phosphole
derivatives.
536 nm with fluorescence quantum yield (Ff) of 0.78. To
our knowledge, this is the highest Ff value ever reported
for type A 2,5-diarylphospholes.6 Nonradiative pathways
from the S1 state of 4b may be suppressed and/or a
radiative pathway may be accelerated by the effective
conjugation through the pyrrole–phosphole–pyrrole
linkage.7 The absorption/emission maxima of 4a, 5a, and
6a are appreciably red-shifted compared to those of the
previously reported 2,5-diarylphosphole analogs. In other
words, the introduction of the pyrrolyl groups narrows
p
p
-
HOMO–LUMO gaps of p-conjugated phospholes of type A.
For instance, the optical HOMO–LUMO gaps of the
respective s3-P and s4-P–oxo derivatives are 2.69 eV
(Ar = 2-pyrrolyl) vs. 2.72–3.02 eV (2-thienyl, phenyl, 2-
pyridyl, measured in THF) [4d] and 2.39 eV (Ar = 2-
pyrrolyl) vs. 2.51–2.83 eV (2-thienyl, phenyl, measured
in THF) [4b, 8b, 14].
Redox potentials of 4b, 5a,b, and 6a,b were measured
by using cyclic voltammetry (CV) and differential pulse
voltammetry (DPV) with 0.1 M nBu4NPF6 as an electro-
To get more insight into electronic structures of the
phosphole–pyrrole hybrid
p-systems, we performed
density functional theory (DFT) calculations on model
compounds 4m and 5m in three forms, anti–anti, anti–syn,
and syn–syn (Fig. 3). At the optimized structures, inter-ring
torsion angles are small (10.1–21.78) for all models. This
indicates that the effective
p-conjugation is attained over
the three heterole rings. There is negligible difference in
6
Optical data (
l
ab/nm,
lem/nm,
F
f; measured in THF) for selected 2,5-
relative energies of the three conformers for 4m
E < 0.3 kcal molꢀ1), implying that all forms are equally
diaryl-3,4-tetramethylene-1-phenylphosphole derivatives reported by
(
D
3
´
Reau’s group [4d] and Tanaka’s group [8b]: The O -P series: Ar = phenyl
(354, 466, 0.143); Ar = 2-thienyl (412, 501, 0.050); Ar = 2-pyridyl (390,
463, 0.011). The O4-P O series: Ar = phenyl (370, 505, 0.0012); Ar = 2-
thienyl (434, 556, 0.0069). The O4-P S series: Ar = 2-thienyl (432, 548,
0.046); Ar = 2-pyridyl (364, 470, 0.00004). For details on the measure-
8
Redox potentials (Epa /V, Epc/V; measured in THF) for selected 2,5-
diaryl-3,4-tetramethylene-1-phenylphosphole derivatives reported by
Re´au’s group [4d]: The s3-P series: Ar = phenyl (+0.69, ꢀ2.88); Ar = 2-
thienyl (+0.40, ꢀ); Ar = 2-pyridyl (+0.83, ꢀ2.45). The s4-P O series:
Ar = 2-thienyl (+0.63, ꢀ2.03). The s4-P S series: Ar = 2-thienyl (+0.68,
ꢀ1.95); Ar = 2-pyridyl (+1.43, ꢀ1.88). For details on the measurement
conditions, see the original references.
ment conditions, see the original references.
7
The fluorescent lifetimes (
t
f) of 4b and 7 in CH2Cl2 were determined
f and f values (Table 1),
to be 3.50 ns and 1.54 ns, respectively. With the
t
F
radiative rate constants from the S1 states of 4b and 7 were determined as
2.2 ꢂ 108 sꢀ1 and 5.8 ꢂ 107
s
ꢀ1, respectively.

Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
1039
Fig. 2. UV-Vis absorption and fluorescence spectra (
lex = 450 nm) in CH2Cl2: blue, 4b; green, 5a; red, 5b; black, 7; brown, trans-8. The fluorescence spectra
are normalized to the corresponding absorption spectra for comparison.
Fig. 3. HOMO (lower) and LUMO (upper) of (a) 4m and (b) 5m: anti–anti (left), anti–syn (middle), syn–syn (right). The calculated orbital energies (in eV) are
shown in parentheses.

1040
Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
Scheme 2.
conceivable. In contrast, anti–syn and syn–syn conformers
of 5m are more stabilized by 3.5 and 6.1 kcal molꢀ1
platinum(II) salts (Scheme 2). Treatment of 4b with one
equiv of AuCl(SMe2) in CH2Cl2 at room temperature
yielded AuCl–phosphine complex 7 in 80% yield. When
,
respectively, than anti–anti isomer. Considering the fact
that the stabilization energy of the syn–syn conformer is
about twice as that of the anti–syn one, the origin of this
energetic stabilization is attributable mainly to the
intramolecular NHꢁꢁꢁO ¼ P hydrogen-bonding interac-
tion. Indeed, the NꢁꢁꢁO distance calculated for 5m (anti–
treated with
a half equiv of PtCl2 under the same
conditions, PtCl2–bis(phosphine) complex 8 was formed
as a trans/cis mixture (ca. 1:1). Metal complexes 7 and 8
were characterized by spectroscopy and X-ray crystallog-
raphy. The 31P chemical shifts of 7, trans-8, and cis-8 are dP
˚
syn) (3.067 A) is within the range of this type of hydrogen
51.4,
respectively. The downfield appearance of the NH protons
of 8 ( 9.73–9.79) relative to those of 7 ( 8.48) suggests
dP 51.6 (JP–Pt = 2244 Hz), and dP 31.5 (JP–Pt = 3177 Hz),
bonds [15]. In each model, HOMO consists of conjugated
polyene-derived
p
-networks, whereas LUMO possesses a
d
d
significant character of central phosphole units. The P-
oxygenation from 4m to 5m lowers LUMO and HOMO
levels by 0.62–0.68 eV and 0.25–0.29 eV, respectively. Note
that LUMOs are more stabilized than HOMOs for all
conformers. This is a typical trend for phosphole deriva-
tives and has been rationalized by considering effective
that the pyrrolic NH groups spatially interact with the
chlorine atoms in 8 (vide infra). High-resolution mass
spectra of 7 and trans-8 showed respective parent ion
peaks (M+) at m/z 714.1267 (calcd. 714.1266) and m/z
1229.2854 (calcd. 1229.2849).
The crystal structures of 7 and trans-8 were success-
fully determined by X-ray crystallography. The ORTEP
diagrams are shown in Figs. 4 and 5 with selected bond
lengths and bond angles. In each complex, the phosphorus
center forms a tetrahedral geometry with average C–P–C
and C–P–M angles of 101.9–103.38 and 115.2–114.78,
respectively. The C–P–C bond angles of 7 and 8 are almost
identical to those of 5b. In complex 7, the gold(I) center
adopts a linear geometry with P–Au–Cl bond angle of
176.53(8)8, and both the pyrrole rings adopt anti–anti
conformation against the phosphole ring with small
dihedral angles between the two adjacent heterole rings
(6.2–9.98). Judging from the packing structure, neither
intramolecular nor intermolecular interaction between
the pyrrolic NH protons and the chlorine atoms is present
in 7.
s*(P–X)–p* orbital interaction including the dienic p-
systems as depicted in Fig. 3b. The LUMO levels of the P–
oxo models 5m are more stabilized in the order anti–anti
(ꢀ1.93 eV) > anti–syn (ꢀ2.00 eV) > syn–syn (ꢀ2.06 eV),
which displays a key contribution of the NHꢁꢁꢁO ¼ P
hydrogen-bonds in the stabilization of LUMO. Time-
dependent DFT (TD-DFT) calculation on 4m in the syn–
syn form revealed that the lowest excitation band observed
for the s3-P derivatives 4 is based on a HOMO ! LUMO
p–
p
* transition.
2.3. Coordination behavior of 2,5-bis(5-phenylpyrrol-2-
yl)phosphole
Recently, the structure–optical property relationship of
metal-bridged phosphole-containing -systems has re-
ceived growing interest [17].9 To investigate the coordina-
tion behavior of 2,5-bis(pyrrol-2-yl)phosphole as
p
In trans-8, the platinum(II) atom is the center of Ci
symmetry and forms a square planar geometry (SP–Pt–Cl
= 1808). As shown in Fig. 5a, the Pt–P coordination bonds
a
phosphine ligand, 4b was reacted with gold(I) and
link two pyrrole–phosphole–pyrrole
p-planes as slipped,
parallel fashion, and each system adopts anti–syn
p
conformation with dihedral angles between the two
adjacent heterole rings of 12.9–19.58. Note that the syn
9
Re´au et al. and Baumgartner et al. investigated this topic extensively.

Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
1041
Fig. 4. Top view (upper) and side view (lower) of 7 (30% probability
ellipsoids). Hydrogen atoms except for NH are omitted for clarity.
˚
Selected bond lengths (A) and angles (deg): C(1)–C(2), 1.383(10); C(2)–
C(3), 1.403(10); C(3)–C(4), 1.377(10); C(4)–C(5), 1.439(9); C(5)–C(6),
1.365(9); C(6)–C(7), 1.458(10); C(7)–C(8), 1.351(10); C(8)–C(9),
1.426(10); C(9)–C(10), 1.380(10); C(10)–C(11), 1.394(11); C(11)–C(12),
1.371(10); P–C(5), 1.801(7); P–C(8), 1.820(7); P–C(16), 1.802(7); P–Au,
2.2302(18); Au–Cl, 2.276(2); C(5)–P–C(8), 94.6(3); C(5)–P–C(16),
109.1(3); C(8)–P–C(16), 105.6(3); C(5)–P–Au, 113.1(2); C(8)–P–Au,
119.1(2); C(16)–P–Au, 113.4(2); P–Au–Cl, 176.53(8).
Fig. 5. Top view (upper) and side view (lower) of 8 (30% probability
ellipsoids). Hydrogen atoms except for NH are omitted for clarity.
pyrrole rings direct their NH groups toward the chlorine
˚
Selected bond lengths (A) and angles (deg): C(1)–C(2), 1.368(8); C(2)–
atoms bound to platinum with an intramolecular NꢁꢁꢁCl
C(3), 1.406(8); C(3)–C(4), 1.389(8); C(4)–C(5), 1.442(7); C(5)–C(6),
1.360(7); C(6)–C(7), 1.442(7); C(7)–C(8), 1.357(7); C(8)–C(9), 1.454(7);
C(9)–C(10), 1.387(8); C(10)–C(11), 1.417(8); C(11)–C(12), 1.374(9); P–
C(5), 1.827(5); P–C(8), 1.814(5); P–C(16), 1.827(5); P–Pt, 2.3315(16); Pt–
Cl, 2.3105(15); C(5)–P–C(8), 93.4(2); C(5)–P–C(16), 107.8(2); C(8)–P–
C(16), 109.3(2); C(5)–P–Pt, 112.78(17); C(8)–P–Pt, 114.34(17); C(16)–P–
Pt, 116.75(18); P–Pt–Cl(1), 88.68(5); P–Pt–Cl(1a), 91.32(5).
10
˚
distance of 3.31 A [18], indicating there exists coopera-
tive hydrogen-bonding interaction between the NH pro-
tons and the chlorine atoms. Such a coordinating property
cannot be produced by other conventional aryl substitu-
ents and shows the characteristic structural features of the
˚
pyrrole ligands. A relatively short distance (ca. 3.3 A)
between the center of anti-pyrrole ring and the nearest
ortho-proton of the facing
a
-phenyl group implies that
weak CHꢁꢁꢁ
p
interaction is also present at least in the solid
induces red-shifts of the absorption and fluorescence
maxima (Dlab = 45 nm; Dlem = 70 nm) and decreases of Ff
value (from 0.78 to 0.09) and fluorescence lifetime (from
3.50 ns to 1.54 ns). A small difference in the observed
Stokes shift (Dl) between 7 (Dl = 3.34 ꢂ 103 cmꢀ1) and 4b
state.
2.4. Optical properties of metal complexes of 2,5-bis(1-
phenylpyrrol-2-yl)phosphole
(
Dl = 3.13 ꢂ 103 cmꢀ1) may suggest that the attachment of
Finally, we measured absorption and fluorescence
spectra of the metal complexes, 7 and trans-8.11 Fig. 2
clearly displays that these two complexes show different
optical properties. The AuCl complexation (from 4b to 7)
the AuCl moiety does not affect the intrinsic character of
the HOMO ! LUMO transition significantly. In sharp
contrast, the PtCl2 complexation (from 4b to trans-8)
varies optical properties of the free phosphine ligand
dramatically. In the absorption spectrum of trans-8, two
separated, broad bands were observed at lab 450 and
533 nm with similar intensity. The high-energy band is
slightly blue-shifted (Dlab = ꢀ9 nm) relative to lab of 4b
(459 nm), whereas the low-energy band is largely red-
shifted (Dlab = 74 nm). It is likely that two slipped, parallel
10
The NꢁꢁꢁCl distances of trans-PtCl2 complexes of phosphole-contain-
˚
ing calix[4]pyrroles having N-HꢁꢁꢁCl-Pt hydrogen bonds are 3.18–3.52 A.
11
We could not isolate cis-8 in a completely pure form and hence its
spectrum is not included in Fig. 2. It should be mentioned, however, that
cis-rich 8 (> 95%, determined by 1H NMR) showed one broad absorption
p
-planes with Ci symmetry linked by the Pt–P and NHꢁꢁꢁCl
band at
lab 541 nm in CH2Cl2. In this paper, we do not discuss the
bonds play a crucial role in the unusual splitting observed
observed difference in spectral shape between cis-8 and trans-8 because
no structural information is available for the former complex at present.
for trans-8. No fluorescence was observed for trans-8.

1042
Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
Fig. 6. Frontier orbitals of 7m and 8m. The calculated orbital energies (in eV) are shown in parentheses.
Table 2
Excitation energies and oscillator strengths of 4m (syn–syn), 7m, and 8m calculated by the TD-B3LYP methoda.
State
Excitation energy
(eV)
Oscillator strength
Excitation
Weight (%)
(nm)
420
4m (syn–syn)
11A00
2.95
2.56
0.5865
0.4590
HOMO ! LUMO
HOMO ! LUMO
38
38
7m
11A00
484
8m
21Au
31Au
2.64
2.95
470
420
0.2346
0.6290
HOMO ꢀ 1 ! LUMO + 1
HOMO ! LUMO + 2
39
38
a
The states whose oscillator strengths are less than 0.2 are not included.
To get a deep insight into the character of the observed
absorption bands, we performed TD-DFT calculations on
models of AuI and trans-PtII complexes (Fig. 6 and Table 2).
The structures of 7m and 8m, where all the phenyl
substituents were replaced by hydrogens, were optimized
starting from the X-ray geometries observed for 7 and
trans-8. As shown in Fig. 6a, HOMO and LUMO of 7m
basically maintain the character of the respective orbitals
of 4m (anti-anti) except for their relative energies; LUMO is
more stabilized than HOMO by the AuCl complexation. The
TD-DFT result of 7m (Table 2) implies that the intense
absorption band observed for 7 is based on HOMO -
! LUMO excitation. Fig. 6b shows five frontier orbitals of
8m, HOMO ꢀ 1, HOMO, LUMO, LUMO + 1, and LUMO + 2,
with their orbital energies. Obviously, HOMO and
HOMO ꢀ 1, which are constructed by two original HOMOs
of the free base, do not interact with each other. As a
consequence, HOMO and HOMO ꢀ 1 have almost the same
energies. On the other hand, LUMO and LUMO + 2 consist of
the metal-derived d orbitals and the ligand-derived
p*-
orbitals. Importantly, the coordination to the platinum(II)
center induces a significant split of the original LUMOs of
the symmetrical
p-conjugated ligands probably due to
s
*(M–P)– * orbital interaction. The TD-DFT results of 8m
p
revealed that the two absorption bands observed for trans-
8 are attributable mainly to HOMO ! LUMO + 2 (2.95 eV)
and HOMO ꢀ 1 ! LUMO + 1 (2.64 eV) excitations. The
finding that the lowest excitation state (HOMO ! LUMO)
is not the high-intensity transition for 8m (oscillator
strength is less than 0.1) may also explain the nonfluores-

Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
1043
cent property of the Pt complex 8. These results show that
the metal complexation is a promising approach to make a
large impact on the optical properties of 2,5-bis(pyrrol-2-
yl)phosphole derivatives.
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
noted.
In summary, we established a convenient method for
the synthesis of new
pyrrole substituents, and revealed their optical, electro-
chemical, and coordinating properties. The flat -planes,
p-conjugated phospholes bearing two
3.1. Synthesis of 2a,b
p
low excitation energies, and small oxidation potentials
A mixture of 1a (3.58 g, 12.2 mmol), CuI (212 mg,
1.11 mmol), PdCl2(PPh3)2 (390 mg, 0.55 mmol), 1,6-hepta-
diyne (0.64 mL, 5.6 mmol), triethylamine (12 mL), and 1,4-
dioxane (8 mL) was stirred at room temperature. After
24 h, the reaction mixture was filtrated through a Celite
bed, and the filtrates were concentrated under reduced
pressure. The oily residue was subjected onto alumina
column chromatography (hexane/CH2Cl2 = 1/1) to give 2a
as a pale brown oil (Rf = 0.2, 2.0 g, 85%). 1H NMR (CDCl3,
observed for the s3-P and s4-P derivatives represent the
efficient
p-conjugation through the pyrrole–phosphole–
pyrrole linkage as well as electron excessive nature of the
pyrrole subunits. It is also noteworthy that the gold(I) and
platinum(II) complexes coordinated by the phenyl-capped
s3-P derivative exhibit quite different structural and
optical properties. It is of particular interest that trans-
PtII–bisphosphine complex contains slipped, parallel
planes linked by the Pt–P bonds and the NH–Cl hydrogen
bonds. This cooperative interaction gives rise to split
p-
300 MHz):
CH2CH2CH2), 2.62 (t, 4H, J = 7.0 Hz, CH2CH2CH2), 6.11
(pseudo t, 2H, J = 3.3 Hz pyrrole- ), 6.43 (m, 2H, pyrrole-
), 7.21 (m, 2H, pyrrole-
); 13C{1H} NMR (CDCl3, 75 MHz):
d 1.60 (s, 18H, t-Bu), 1.91 (quint, 2H, J = 7.0 Hz,
p–p*
transitions at the long-wavelength region, which can be
rationalized by considering the orbital interaction between
b
b
a
the Pt–X bonds and the hybrid
tion of phosphole and pyrrole has great synthetic potential,
since these functionalizable heteroles are readily subject to
p
-systems. The combina-
d 18.8, 27.6, 27.7, 73.1, 83.6, 92.4, 110.5, 115.5, 119.7,
121.5, 148.2; HRMS (EI) Calculated for C25H30N2O4 (M+):
422.2206. Found: m/z 422.2203.
new
p
-framework construction. Further studies on mate-
According to a similar procedure, compound 2b was
prepared from 1b and 1,6-heptadiyne. Yield 81%. Pale
rials chemistry of phosphole–pyrrole
tems are now in progress.
p-conjugated sys-
brown oil. 1H NMR (CDCl3, 400 MHz):
d
1.34 (s, 18H, t-Bu),
1.94 (quint, 2H, J = 6.8 Hz, CH2CH2CH2), 2.67 (t, 4H,
J = 6.8 Hz, CH2CH2CH2), 6.13 (d, 2H, J = 3.4 Hz, pyrrole- ),
6.45 (d, 2H, J = 3.4 Hz, pyrrole- ), 7.26–7.38 (m, 10H, Ph);
13C{1H} NMR (CDCl3, 100 MHz):
18.9, 27.17, 27.20, 27.7,
3. Experimental section
b
b
1H, 13C, and 31P NMR spectra were recorded on a JEOL
JNM-EX400 spectrometer using CDCl3 or CD2Cl2. Chemical
shifts are reported in ppm as relative values vs. tetra-
methylsilane (internal reference for 1H and 13C) and
phosphoric acid (external reference for 31P). Matrix-
assisted laser desorption/ionization (MALDI) time-of-flight
mass spectra (TOF) were measured on a SHIMADZU
Biotech AXIMA-CFR spectrometer using 1,8-dihydroxy-
9(10H)-anthracenone (dithranol) as a matrix. High-reso-
lution mass spectra (HRMS) were obtained on a JEOL JMS-
HS110 spectrometer using 3-nitrobenzyl alcohol as a
matrix. IR spectra were recorded on a JASCO FT/IR-470 Plus
spectrometer using KBr pellets. UV-vis absorption spectra
were measured on a PerkinElmer Lambda 900 UV/vis/NIR
spectrometer. Steady-state fluorescence spectra were
recorded with a SPEX Fluoromax-3 spectrofluorometer
(HORIBA). Electrochemical measurements were made with
an ALS 630a electrochemical analyzer using a glassy
d
27.8, 73.0, 83.8, 93.1, 112.4, 117.4, 117.7, 127.0, 127.7,
128.1, 133.9, 135.6, 148.7; MS (EI): m/z 374 ([M ꢀ 2Boc]+).
3.2. Synthesis of 3a,b
To a mixture of 2a (6.3 g, 15 mmol), Ti(Oi-Pr)4 (4.4 mL,
15 mmol), and Et2O (210 mL) was slowly added an ether
solution of i-PrMgCl (2.0 M ꢂ 15 mL, 30 mmol) at ꢀ78 8C,
and the resulting mixture was stirred for 2 h at ꢀ50 8C.
Dichloro(phenyl)phosphine (2.0 mL, 15 mmol) was then
added to the mixture at this temperature, and the resulting
suspension was allowed to warm to 0 8C and stirred for 1 h
at this temperature. After stirring for an additional 2 h at
room temperature, a saturated aq NH4Cl solution was
poured into the reaction mixture, and insoluble substances
were filtrated off through a Celite bed. The Celite bed was
washed with AcOEt repeatedly, and the filtrate was
washed with brine. The aqueous phase was extracted
with AcOEt, and the combined organic extracts were dried
over Na2SO4 and evaporated under reduced pressure. The
oily residue was subjected onto alumina column chroma-
tography (hexane/CH2Cl2 = 2/1). The yellow fraction
(Rf = 0.4) was collected and evaporated to give a yellow
solid (3.4 g, 43%). Mp 46–47 8C; 1H NMR (CDCl3, 400 MHz):
carbon working electrode,
a platinum wire counter
electrode, and an Ag/Ag+ [0.01 M AgNO3, 0.1 M nBu4NPF6
(MeCN)] reference electrode. The potentials were calibrat-
ed with ferrocene/ferrocenium [Emid = +0.20 V vs. Ag/Ag+].
1-Boc-2-iodopyrrole (1a) [12] and 1-Boc-2-iodo-5-phe-
nylpyrrole (1b) [13] were prepared according to the
reported procedures.
The solvents used for the reactions were distilled from
sodium benzophenone ketyl (THF and Et2O) or calcium
hydride (CH2Cl2) under inert atmosphere before use. Other
chemicals and solvents were of reagent grade quality,
purchased commercially and used without further purifi-
cation. Thin-layer chromatography and flash column
d
1.52 (s, 18H, t-Bu), 2.13–2.22 (m, 2H, CH2CH2CH2), 2.31–
2.43 (m, 2H, CH2CH2CH2), 2.50–2.69 (m, 2H, CH2CH2CH2),
5.95 (broad s, 2H, pyrrole- ), 6.07 (pseudo t, 2H, J = 3.4 Hz,
pyrrole- ), 7.22–7.25 (m, 2H, pyrrole- ), 7.15–7.25 (m, 3H,
P-Ph-m,p), 7.34–7.40 (m, 2H, P-Ph-o); 13C{1H} NMR (CDCl3,
100 MHz): 27.9, 28.8, 29.0, 83.2, 110.6, 114.6 (d, JP–
b
b
a
d

1044
Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
C = 6.6 Hz), 122.5, 128.1 (d, JP–C = 7.4 Hz), 128.7, 129.1,
129.7 (d, JP–C = 24.0 Hz), 133.0 (d, JP–C = 15.7 Hz), 133.5 (d,
JP–C = 19.0 Hz), 149.2, 155.5 (d, JP–C = 11.6 Hz); 31P{1H} NMR
3.4. Synthesis of 5a,b
To a THF solution (1.5 mL) of 3a (71.5 mg, 0.135 mmol)
was added MeOH (3 mL) solution of NaOMe (72.8 mg,
1.35 mmol) at room temperature. After stirring at 70 8C for
16 h, water (10 mL) and diethyl ether (10 mL) were added.
The aqueous phase was extracted with diethyl ether and
the combined organic extracts were dried over Na2SO4 and
evaporated under reduced pressure. The residue was
subjected onto alumina column chromatography (hex-
ane/CH2Cl2 = 2/1 to CH2Cl2/acetone = 6/1). The yellow
fraction (Rf = 0.4; hexane/CH2Cl2 = 2/1) was collected. After
removal of solvents under reduced pressure, the resulting
mixture was resolved in CH2Cl2. To the resulting solution
was added hydrogen peroxide (30% solution in H2O,
0.1 mL). After stirring 1 h, the mixture was concentrated
under reduced pressure, and the solid residue was washed
with diethyl ether to give 5a as a red solid (37.1 mg, 79%).
(CDCl3, 162 MHz):
371 nm (10600); HRMS (FAB) calculated for C31H35N2O4P
(M+): 530.2334. Found: m/z 530.2353.
d + 45.9; UV-vis (CH2Cl2): lmax (e)
According to a similar procedure, compound 3b was
prepared from 2b. However, 3b could not be purified
completely, as the remaining 2b was difficult to separate
from the crude product. 1H NMR (CD2Cl2, 400 MHz):
d 1.21
(s, 18H, t-Bu), 2.17–2.27 (m, 2H, CH2CH2CH2), 2.38–2.50
(m, 2H, CH2CH2CH2), 2.68–2.80 (m, 2H, CH2CH2CH2), 6.01–
6.13 (m, 4H, pyrrole-
NMR (CDCl3, 162 MHz):
for C43H43N2O4P (M+): 682.2960. Found: m/z 682.2989.
b
), 7.20–7.40 (m, 15H, Ph); 31P{1H}
+ 45.6; HRMS (FAB) calculated
d
3.3. Synthesis of 4a,b
To a THF solution (1.5 mL) of 3a (100 mg, 0.188 mmol)
was added a MeOH solution (3 mL) of NaOMe (102 mg,
1.88 mmol) at room temperature. After stirring at 70 8C for
16 h, water (10 mL) and diethyl ether (10 mL) were added.
The aqueous phase was extracted with diethyl ether and
the combined organic extracts were dried over Na2SO4.
After removal of solvents under reduced pressure, the
resulting mixture was subjected to alumina column
chromatography (hexane/CH2Cl2 = 2/1 to CH2Cl2/ace-
tone = 6/1). The yellow fraction (Rf = 0.5; hexane/
CH2Cl2 = 2/1) was collected, evaporated, and reprepici-
pated from CH2Cl2/hexane to give 4a (47 mg, 76%) as a
Mp 255 8C (dec); 1H NMR (CDCl3, 400 MHz):
d 2.00–2.10
(m, 1H, CH2CH2CH2), 2.28–2.40 (m, 1H, CH2CH2CH2), 2.66–
2.80 (m, 2H, CH2CH2CH2), 2.81–2.90 (m, 2H, CH2CH2CH2),
6.25 (s, 2H, pyrrole-
pyrrole- ), 7.30–7.45 (m, 3H, P-Ph-m,p), 7.65–7.78 (m, 2H,
P-Ph-o), 9.09 (broad s, 2H, NH); 13C{1H} NMR (CDCl3,
100 MHz): 25.8, 29.3 (d, JP–C = 11.6 Hz), 109.2 (d, JP–
b), 6.32 (s, 2H, pyrrole-b), 6.80 (s, 2H,
a
d
C = 7.4 Hz), 110.1, 116.0, 117.0, 119.9, 126.2 (d, JP–
C = 11.6 Hz), 128.9 (d, JP–C = 12.4 Hz), 130.4 (d, JP–
C = 10.7 Hz), 132.1 (d, JP–C = 3.3 Hz), 149.6 (d, JP–
C = 24.8 Hz); 31P{1H} NMR (CDCl3, 162 MHz):
(KBr): (e)
= 1165 (P O) cmꢀ1; UV-vis (CH2Cl2): lmax
d + 54.3; IR
n
brownish red solid. 1H NMR (CDCl3, 400 MHz):
(m, 2H, CH2CH2CH2), 2.63–2.72 (m, 2H, CH2CH2CH2), 2.78–
2.87 (m, 2H, CH2CH2CH2), 6.17–6.18 (m, 4H, pyrrole- ),
6.65–6.66 (m, 2H, pyrrole- ), 7.26–7.34 (m, 3H, P-Ph-m,p),
7.53–7.57 (m, 2H, P-Ph-o), 8.01 (broad s, 2H, NH); 13C{1H}
NMR (CDCl3, 100 MHz): 28.6, 29.2, 107.3 (d, JP–C = 5.0 Hz),
d
2.33–2.49
458 nm (16700); HRMS (EI) calculated for C21H19N2OP
(M+): 346.1235; Found: m/z 346.1241.
Compound 5b was prepared from 4b and mCPBA. Yield,
93%. Reddish brown solid. Mp 260 8C (dec); 1H NMR (CDCl3,
400 MHz): d 2.00–2.15 (m, 1H, CH2CH2CH2), 2.31–2.42 (m,
1H, CH2CH2CH2), 2.69–2.80 (m, 2H, CH2CH2CH2), 2.80–2.94
(m, 2H, CH2CH2CH2), 6.38 (pseudo t, 2H, J = 2.9 Hz, pyrrole-
b
a
d
109.8, 118.1, 125.7, 129.1 (d, JP–C = 7.4 Hz), 129.5 (d, JP–
C = 22.3 Hz), 130.0, 133.3 (d, JP–C = 14.1 Hz), 133.6 (d, JP–
C = 19.8 Hz), 150.7 (d, JP–C = 8.3 Hz); 31P{1H} NMR (CDCl3,
b
), 6.55 (s, 2H, pyrrole-
7.27–7.49 (m, 11H, Ph), 7.79–7.84 (m, 2H, P-Ph-o), 9.28
(broad s, 2H, NH); 13C{1H} NMR (CDCl3, 100 MHz):
25.8,
b), 7.18–7.21 (m, 2H, P-Ph-m),
162 MHz):
d
+ 28.1; UV-vis (CH2Cl2):
l
max: 416 nm; HRMS
d
(EI) calcd for C21H19N2P (M+): 330.1286. Found: m/z
330.1292.
29.3 (d, JP–C = 11.6 Hz), 108.2, 111.4 (d, JP–C = 7.4 Hz), 115.8,
116.7, 123.8, 126.6, 127.6 (d, JP–C = 12.4 Hz), 128.9, 129.1
(d, JP–C = 12.4 Hz), 130.0, 130.3 (d, JP–C = 10.7 Hz), 130.9,
131.7, 132.2 (d, JP–C = 2.5 Hz), 133.8, 149.8 (d, JP–
According to a similar procedure, compound 4b was
prepared from 3b. Yield: 28% (based on 2b). Red solid. Mp
194–195 8C; 1H NMR (CD2Cl2, 400 MHz):
d
2.40–2.55 (m,
C = 25.6 Hz); 31P{1H} NMR (CDCl3, 162 MHz):
(KBr):
= 1180 (P O) cmꢀ1; UV-vis (CH2Cl2): lmax
(21000), 506 nm (24100); HRMS (EI) calculated for
33H27N2OP (M+): 498.1861; Found: m/z 498.1858.
d
+ 55.6; IR
) 322
2H, CH2CH2CH2), 2.70–2.80 (m, 2H, CH2CH2CH2), 2.85–
2.94 (m, 2H, CH2CH2CH2), 6.25 (pseudo t, 2H, J = 2.9 Hz,
n
(e
pyrrole-
b
), 6.47 (pseudo t, 2H, J = 2.9 Hz, pyrrole-
b
), 7.15–
C
7.19 (m, 2H, P-Ph-m), 7.31–7.37 (m, 11H, Ph), 7.61–7.65
(m, 2H, P-Ph-o), 8.26 (broad s, 2H, NH); 13C{1H} NMR
3.5. Synthesis of 6a,b
(CDCl3, 75 MHz):
d 28.6, 29.1, 107.8, 109.6 (d, JP–
C = 5.6 Hz), 118.2, 123.2, 125.5, 126.0, 128.8, 129.2 (d,
JP–C = 8.1 Hz), 130.2 (d, JP–C = 1.9 Hz), 130.7 (d, JP–
C = 22.3 Hz), 132.02, 132.05, 133.4 (d, JP–C = 14.3 Hz),
133.5 (d, JP–C = 19.8 Hz), 151.1 (d, JP–C = 9.3 Hz), One of
the carbon atoms could not be detected clearly; 31P{1H}
To a THF solution (3 mL) of 4a (198 mg, 0.373 mmol)
was added MeOH solution (6 mL) of NaOMe (204 mg,
3.77 mmol) at room temperature. After stirring at 70 8C for
16 h, water (10 mL) and diethyl ether (10 mL) were added.
The aqueous phase was extracted with diethyl ether and
the combined organic extracts were dried over Na2SO4.
After removal of solvents under reduced pressure, the
resulting mixture was resolved in CH2Cl2. To the resulting
solution was added elemental sulfur (60.3 mg, 1.88 mmol).
After stirring 3 h, the mixture was concentrated under
NMR (CD2Cl2, 162 MHz):
d
+ 28.5; UV-vis (CH2Cl2): lmax
) 330 (15200), 459 nm (34400); HRMS (EI) calcd for
33H27N2P (M+): 482.1912. Found: m/z 482.1905. Anal.
(
e
C
calculated for C33H27N2P: C, 82.14; H, 5.64; N, 5.81. Found:
C, 81.88; H, 5.63; N, 5.75.

Y. Matano et al. / C. R. Chimie 13 (2010) 1035–1047
1045
reduced pressure, and the solid residue was subjected to
alumina column chromatography (hexane/CH2Cl2 = 2/1).
The orange fraction (Rf = 0.2) was collected, evaporated,
and reprecipitated from CH2Cl2/hexane to give 6a as an
orange solid (117 mg, 86%). Mp 220 8C (dec); 1H NMR
mixture (ca. 1:1). Recrystallization of trans-rich 8 from
CH2Cl2–hexane by a slow diffusion method afforded single
crystals of trans-isomer as a dark brown solid. trans-8: 1
H
NMR (CD2Cl2, 400 MHz):
2.71–2.74 (m, 8H, CH2CH2CH2), 6.43 (broad s, 2H, pyrrole-
), 6.55 (broad s, 2H, pyrrole- ), 7.12–7.25 (m, 18H, Ph and
d 2.15–2.44 (m, 4H, CH2CH2CH2),
(CDCl3, 400 MHz):
2.47 (m, 1H, CH2CH2CH2), 3.20–3.40 (m, 4H, CH2CH2CH2),
6.21–6.23 (m, 2H, pyrrole- ), 6.30 (s, 2H, pyrrole- ), 6.76–
6.78 (m, 2H, pyrrole- ), 7.33–7.44 (m, 3H, P-Ph-m,p), 7.84–
7.90 (m, 2H, P-Ph-o), 9.61 (broad s, 2H, NH); 13C{1H} NMR
(CDCl3, 100 MHz): 26.9, 29.3 (d, JP–C = 10.7 Hz), 109.7 (d,
JP–C = 8.3 Hz), 109.8, 117.8, 118.6, 119.6, 126.3 (d, JP–
C = 12.4 Hz), 128.9 (d, P–C = 12.4 Hz), 130.2 (d, JP–
C = 11.6 Hz), 132.0 (d, JP–C = 3.3 Hz), 151.0 (d,
C = 22.3 Hz); 31P{1H} NMR (CDCl3, 162 MHz):
+ 63.4;
) 454 nm (17,500); HRMS (EI)
d
2.13–2.25 (m, 1H, CH2CH2CH2), 2.33–
b
b
P-Ph-m,p), 7.39–7.42 (m, 8H, Ph), 7.55–7.71 (m, 4H, P-Ph-
o), 9.73 (broad s, 4H, NH); 31P{1H} NMR (CD2Cl2, 162 MHz):
b
b
a
d
+ 51.6 (JPt–P = 2244 Hz); UV-vis (CH2Cl2): lmax
(23000), 533 nm (25000); HRMS (FAB) calculated for
66H54N4Cl2P2Pt 1229.2849. Found: m/z
(M+):
1229.2854. cis-8 (cis/trans > 95/5): 1H NMR (CDCl3,
400 MHz): 2.05–2.30 (m, 4H, CH2CH2CH2), 2.30–2.61
(m, 8H, CH2CH2CH2), 6.19 (broad s, 2H, pyrrole- ), 6.31
(broad s, 2H, pyrrole- ), 7.05–7.34 (m, 18H, Ph and P-Ph-
m,p), 7.40–7.50 (m, 8H, Ph), 7.61–7.75 (m, 4H, P-Ph-o), 9.79
(broad s, 4H, NH); 31P{1H} NMR (CD2Cl2, 162 MHz):
+ 31.5
) 541 nm; HRMS
(e) 450
d
C
J
d
J
b
P–
d
b
UV-vis (CH2Cl2): lmax (e
calculated for C21H19N2PS (M+): 362.1007; Found: m/z
362.1011.
d
(JPt–P = 3177 Hz); UV-vis (CH2Cl2): lmax (e
According to a similar procedure, compound 6b was
prepared from 4b and elemental sulfur. Yield, 82%. Brown
(FAB) calculated for C66H54N4Cl2P2Pt (M+): 1229.2849.
Found: m/z 1229.2837.
solid. Mp 286 8C (dec); 1H NMR (CD2Cl2, 400 MHz):
d
2.20–
2.35 (m, 1H, CH2CH2CH2), 2.35–2.52 (m, 1H, CH2CH2CH2),
2.75–2.90 (m, 4H, CH2CH2CH2), 6.41 (s, 2H, pyrrole- ), 6.57
(s, 2H, pyrrole- ), 7.20–7.25 (m, 2H, P-Ph-m), 7.30–7.52
(m, 11H, Ph), 7.90–8.05 (m, 2H, P-Ph-o), 9.96 (broad s, 2H,
NH); 13C{1H} NMR (CDCl3, 100 MHz):
27.0, 29.4 (d, JP–
3.8. X-ray structural determination
b
b
Single crystals of 5b, 7, and trans-8 were grown from
CH2Cl2–MeOH (for 5b and 7) or CH2Cl2–hexane (for 8). All
measurements were made on a Rigaku Mercury-8 CCD
d
C = 11.6 Hz), 107.7, 111.7 (d, JP–C = 8.3 Hz), 117.4, 118.2,
123.8, 126.6, 127.6 (d, JP–C = 12.4 Hz), 128.9, 129.0, 129.1
(d, JP–C = 12.4 Hz), 130.2 (d, JP–C = 11.6 Hz), 131.8, 132.1 (d,
JP–C = 3.3 Hz), 133.6, 151.3 (d, JP–C = 21.5 Hz), Two of the
carbon atoms could not be detected clearly; 31P{1H} NMR
area detector with graphite monochromated Mo–Ka
radiation at 143 K. The structures were solved by a direct
method (SIR92) [19] and expanded using Fourier techni-
ques [20]. Non-hydrogen atoms were refined anisotropi-
cally, and hydrogen atoms were refined using the rigid
model. All calculations were performed using Crystal-
Structure12 crystallographic software package except for
refinement, which was performed using SHELXL-97 [21].
Crystal data and structural refinement parameters are as
follows. 5b: C33H27N2OP, red block, 0.30 ꢂ 0.20 ꢂ 0.08 mm,
MW = 498.54, monoclinic, space group = P21/n, a =
(CD2Cl2, 162 MHz):
(20300), 507 nm (22700); HRMS (EI) calculated for
33H27N2PS (M+): m/z 514.1633; Found: m/z 514.1630.
d + 63.6; UV-vis (CH2Cl2): lmax (e) 320
C
3.6. Synthesis of 7
˚
˚
˚
A mixture of 4b (10 mg, 0.021 mmol), AuClꢁSMe2
(6.1 mg, 0.021 mmol), and CH2Cl2 (1 mL) was stirred for
30 min at room temperature. The mixture was then
concentrated under reduced pressure and subjected to
silica gel column chromatography (CH2Cl2). The red
fraction (Rf = 0.7) was collected, evaporated, and repreci-
pitated from CH2Cl2/hexane to give 7 as a dark brown solid
(12.0 mg, 80%). Mp 215–216 8C; 1H NMR (CD2Cl2,
11.092(2)
b
m
A,
b = 18.861(3)
A,
c = 11.952(2)
A,
3
ꢀ3
,
˚
= 98.244(2)8, V = 2474.5(8) A , Z = 4, Dc = 1.338 g cm
= 1.42 cmꢀ1, 28128 observed, 5653 unique, 335 vari-
ables, Rw = 0.1239, R = 0.0495 (I > 2.0 (I)), GOF = 1.152. 7:
33H27AuClN2P, red block, 0.25 ꢂ 0.20 ꢂ 0.08 mm, MW =
s
C
˚
714.95, monoclinic, space group = P21/c, a = 11.116(3) A,
˚
˚
˚
b = 19.045(5)
V = 2793.1(14) A , Z = 4, Dc = 1.700 g cmꢀ3
cmꢀ1
31812 observed, 6257 unique, 344 variables,
Rw = 0.1311, R = 0.0533 (I > 2.0 (I)), GOF = 1.175. trans-8:
66H54Cl2N4P2Pt, dark brown block, 0.25 ꢂ 0.20 ꢂ
0.10 mm, MW = 1231.06, monoclinic, space group = P21/c,
A,
c = 13.303(4)
A,
b
= 97.365(5)8,
3
,
m
= 54.64
400 MHz):
(m, 4H, CH2CH2CH2), 6.46 (broad s, 2H, pyrrole-
(broad s, 2H, pyrrole- ), 7.20–7.26 (m, 2H, P-Ph-m), 7.33–
7.58 (m, 11H, Ph), 7.85–7.91 (m, 2H, P-Ph-o), 8.48 (broad s,
2H, NH); 31P{1H} NMR (CD2Cl2, 162 MHz):
+ 51.4; UV-vis
(CH2Cl2): lmax ) 504 nm (29900); HRMS (FAB) calculated
d
2.47–2.55 (m, 2H, CH2CH2CH2), 2.88–3.02
,
b
), 6.50
s
b
C
˚ ˚ ˚
d
a = 15.424(9) A, b = 11.803(6) A, c = 18.046(10) A,
3
ꢀ3
,
˚
(
e
b
m
= 114.382(8)8, V = 2992(3) A , Z = 2, Dc = 1.366 g cm
= 25.30 cmꢀ1, 19757 observed, 6716 unique, 341 vari-
ables, Rw = 0.1761, R = 0.0653 (I > 2.0 (I)), GOF = 1.087.
for C33H27AuClN2P (M+): 714.1266; Found: m/z 714.1267.
s
3.7. Synthesis of 8
CCDC-762249 (5b), CCDC-762250 (7), and CCDC-763570
(trans-8) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge
A mixture of 4b (10.8 mg, 0.022 mmol), PtCl2 (3.0 mg,
0.010 mmol), and CH2Cl2/MeOH (2:1, 1.5 mL) was stirred
at room temperature. After 3 h, the mixture was concen-
trated under reduced pressure and then filtered off
through a Celite bed. The filtrate was reprecipitated from
CH2Cl2/hexane to afford 8 (8.3 mg, 67%) as a trans/cis
12
Crystal Structure 3.8.2: Crystal Structure Analysis Package, Rigaku
and Rigaku/MSC (2000–2006). 9009 New Trails Dr. The Woodlands TX
77381, USA.

1046
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Acknowledgment
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We thank Dr. Yoshihide Nakao (Kyoto University) for
his valuable suggestions about DFT calculations. We also
thank Prof. Hiroko Yamada and Mr. Daiki Kuzuhara (Ehime
University) for the measurement of absolute fluorescence
quantum yield of 4b and Prof. Yoshifumi Kimura (Kyoto
University) for the measurement of fluorescence lifetimes
of 4b and 7. This work was supported by a Grant-in-Aid for
Scientific Research on Innovative Areas (No. 21108511, ‘‘p-
Space’’) from the Ministry of Education, Culture, Sports,
Science and Technology, Japan.
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