Synthesis of one-dimensional metal-containing insulated molecular wire with versatile properties directed toward molecular electronics materials

Article abstract of DOI:10.1021/ja411665k

We report, herein, the design, synthesis, and properties of new materials directed toward molecular electronics. A transition metal-containing insulated molecular wire was synthesized through the coordination polymerization of a Ru(II) porphyrin with an insulated bridging ligand of well-defined structure. The wire displayed not only high linearity and rigidity, but also high intramolecular charge mobility. Owing to the unique properties of the coordination bond, the interconversion between the monomer and polymer states was realized under a carbon monoxide atmosphere or UV irradiation. The results demonstrated a high potential of the metal-containing insulated molecular wire for applications in molecular electronics.

Full text of DOI:10.1021/ja411665k

Communication
pubs.acs.org/JACS
Synthesis of One-Dimensional Metal-Containing Insulated Molecular
Wire with Versatile Properties Directed toward Molecular Electronics
Materials
Hiroshi Masai,† Jun Terao,*,† Shu Seki,‡ Shigeto Nakashima,§ Manabu Kiguchi,§ Kento Okoshi,∥
Tetsuaki Fujihara,† and Yasushi Tsuji†
†Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto
615-8510, Japan
‡Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
§Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku,
Tokyo 152-8551, Japan
∥Department of Bio- and Material Photonics, Chitose Institute of Science and Technology, 758-65 Bibi, Chitose, Hokkaido 066-8655,
Japan
S
* Supporting Information
connected to functionalized molecular wires could exhibit not
ABSTRACT: We report, herein, the design, synthesis,
and properties of new materials directed toward molecular
electronics. A transition metal-containing insulated molec-
ular wire was synthesized through the coordination
polymerization of a Ru(II) porphyrin with an insulated
bridging ligand of well-defined structure. The wire
displayed not only high linearity and rigidity, but also
high intramolecular charge mobility. Owing to the unique
properties of the coordination bond, the interconversion
between the monomer and polymer states was realized
under a carbon monoxide atmosphere or UV irradiation.
The results demonstrated a high potential of the metal-
containing insulated molecular wire for applications in
molecular electronics.
only conductivity but also physical property change by external
stimuli.5
Therefore, we have focused on one-dimensional coordination
polymers containing transition metals,6 which combine the
advantages of organic IMWs mentioned above, with those of
transition metal complexes. In the field of molecular electronics,
they are expected to form wiring materials with novel
properties including: (3) various characteristics derived from
the transition metal complexes such as redox behavior,7 triplet
state properties,8 and the Kondo effect;9 and (4) enhanced
processability such as recyclability and self-healing through
reversible monomer−polymer interconversion brought on by
the reversible nature of the noncovalent bonds as opposed to
covalently bonded molecular wires.10 In spite of their potential
utility, however, there are no suitable examples of organic−
inorganic wiring materials that display rigidity, linearity, and
especially, conductivity, probably owing to their weak
connections and/or localized molecular orbitals at the
organic−inorganic bonding interfaces. Herein, we present the
successful synthesis of a transition metal-containing IMW with
desirable properties for wiring materials including high rigidity,
linearity, and high charge mobility as compared to conventional
π-conjugated polymers. We accomplished this through the
coordination polymerization of Ru(II) porphyrin complexes
with insulated bridging ligands having well-defined structures,11
and this IMW displayed novel processability as a result of its
noncovalent bonding motif.
nsulated molecular wires (IMWs),1 composed of π-
Iconjugated polymer chains covered with protective sheaths
that limit π−π interactions between the conjugated backbones,
have received particular attention due to their potential
applications as wiring materials in molecular electronics. For
use as wiring materials, π-conjugated polymers must satisfy two
requirements: (1) compatible processability resulting from high
solubility and defined molecular structure, and (2) appropriate
material properties such as high linearity, rigidity, and, in
particular, high conductivity. We previously succeeded in the
synthesis of IMWs which adequately satisfied properties (1)
and (2); in these wires, the conjugated moieties were isolated
through insulation using α-cyclodextrin (α-CD) derivatives.2
We also clarified the utility of IMWs for molecular electronics
by achieving highly efficient wiring to nanoelectrodes as
compared with the corresponding uninsulated molecular
wires.3,4 However, it is not necessary for IMWs to strictly
mimic their conventional inorganic wiring materials. In other
words, molecular wires that contain stimuli-responsive units in
their polymer chains are expected to perform as higher-order
nanodevices owing to their functionalities; i.e., electrodes
We first prepared an insulated bridging ligand 3 with high
coverage, structural regularity, and conductivity, and demon-
strated its applicability as a component of molecular wires.
1
Scheme 1 shows the synthetic route to obtain 3. Using H
NMR, we confirmed the quantitative self-inclusion of precursor
1,2a oligo(phenylene ethynylene) (OPE) containing two
permethylated (PM) α-CDs in CH3OH/H2O (2:1),2e resulting
Received: November 19, 2013
Published: January 15, 2014
© 2014 American Chemical Society
1742
dx.doi.org/10.1021/ja411665k | J. Am. Chem. Soc. 2014, 136, 1742−1745

Journal of the American Chemical Society
Communication
Scheme 1. Synthesis of the Insulated Bridging Ligand 3
Figure 1. Single crystal structure of 5: (a) lateral (space-filling model)
view; (b) top (ball and stick model) view. Hydrogen atoms and
porphyrin 4 are omitted.
which prevented their shuttling and rotation, inhibited the
disordering of the components of 5 (Figure 1).14 The two PM
α-CDs clearly insulated the OPE skeleton in the absence of
solvent molecules at their interface. The similar diameters of
the PM α-CDs and TTPs resulted in a pillar-like structure. It
was apparent that the three insulated benzene rings of the π-
conjugated guest were almost planar as the torsion angles
between adjacent benzene rings were 11.1° and 12.8°. The
dihedral angle between the TTP planes at both ends of 5 was
nearly parallel (178°), resulting in the high linearity of the π-
conjugated guest unit of 5. As shown above, 3 revealed
considerable potential as a bridging ligand for a one-
dimensional coordination polymer because of its high solubility,
structural stability, conductivity, and linearity.
To synthesize a one-dimensional metal-containing insulated
molecular wire with strong coordinate bonds, we carried out a
complexation of 3 with Ru(II) porphyrin, which was generated
in situ from Ru(II) carbonyl porphyrin 6 by UV irradiation with
a mercury lamp to release the coordinated carbon monoxide
(Scheme 3).15,16 Since the Ru-pyridyl coordinate bonds were
in the inclusion complex 2. Using the same solvent
combination, we reacted the intermediate pseudorotaxane
structure of 2 with p-iodopyridine via Sonogashira coupling
to form 3 bearing coordinating groups at both ends, in good
yield. The fixed [3]rotaxane structure of 3 could be constructed
by elongation of the π-conjugated unit of 2 without the
introduction of bulky stopper groups at both ends due to its
linkages between the axis and rings. The structure of 3 was
confirmed using ROESY NMR spectroscopy (Figure S2). 3
displayed high solubility in various organic solvents because of
the insulating PM α-CDs. The thermal stability of the rotaxane
1
structure was validated using H NMR, as the insulation was
retained in toluene under reflux (Figure S3).
We then investigated the electron transport properties of the
monomeric insulated bridging ligand 3 using the scanning
tunneling microscopy breakjunction (STM BJ) method.12 We
anticipated that the pyridyl groups of 3 would be suitable for
STM BJ because they could act as anchoring units on gold
electrodes via Au-N coordination. The insulation of monomer
3 revealed a fixed conductance value (Figure S5) due to the
restricted intramolecular motion in the conjugated system.
Clear steps in the conductance traces could be observed
because of the limited intermolecular π−π interactions due to
shielding from the PM α-CDs.4 The resulting conductance of 3
was 7 × 10−6 G0, which was high enough to be considered as a
potential component of conducting molecular wires.13
To examine the detailed structure of 3 using X-ray crystal
structure analysis, the heavy atom-bearing coordination
complex 5 was synthesized by the reaction of 3 with
Rh(TTP)Cl (TTP: tetratolylporphyrin) 4 in high yield
(Scheme 2).
Scheme 3. Synthesis of Molecular Wire 7
fixed in the trans-configuration at the six-coordinate Ru center,
we expected that a stable linear coordination polymer would be
formed without isomerization. The formation of coordination
polymer 7 (Mw = 7.1 × 104, Mn = 2.7 × 104)17 was confirmed
using size-exclusion chromatography (SEC) and IR spectro-
scropy.18 The coordination polymer exhibited high solubility in
organic solvents such as toluene and CHCl3 as well as high
stability. Decomplexation was not observed in coordinating
solvents such as THF and pyridine at room temperature
(Figure S8).
Single crystals suitable for X-ray crystallography were grown
through vapor diffusion of MeOH into a solution of 5 in THF.
In the solid state, 5 clearly exhibited a fixed [3]rotaxane
structure due to the linkages between the PM α-CDs and OPE,
Scheme 2. Synthetic Route To Obtain Coordination
Complex 5
Next, we evaluated the rigidity and linearity of molecular wire
7. Figure 2a displays a polarized optical micrograph of 7 in a
concentrated CHCl3 solution. Notably, 7 formed a cholesteric
liquid crystal phase as confirmed by its clear fingerprint texture.
We confirmed that this observed phase arose from the rigidity
of the insulating bridging ligand and chirality of the
cyclodextrins because the corresponding uninsulated coordina-
tion reference wires, 7′ and 7″ (Figure 2c), did not form
cholesteric phases, but rather formed isotropic liquids (Figure
S9). In addition, according to the unperturbed wormlike
1743
dx.doi.org/10.1021/ja411665k | J. Am. Chem. Soc. 2014, 136, 1742−1745

Journal of the American Chemical Society
Communication
transient absorption of triplet states and radical cations strongly
suggest that the major charge carriers are positive holes on the
backbone of 7 as indicated by the identical kinetic traces of the
latter in the conductivity transients. On the basis of the molar
absorption coefficient of the radical cations (7 × 104 mol−1 dm3
cm−1), the estimates of charge carrier generation yield (ϕ) as
1.0 × 10−2 lead the intramolecular charge mobility (μ+ = 0.22
cm2 V−1 s−1) along the conjugated backbone of 7. This
intramolecular charge mobility is comparable to that of the
insulated all-organic poly(phenylene ethynylene) wire (insu-
lated PPE: structure, see Figure S15b), which we reported
previously (0.52 cm2 V−1 s−1).2b Notably, 7 exhibited the same
order (10−1 cm2 V−1 s−1) of intramolecular hole mobility as
Figure 2. (a) Polarized optical micrograph of 7 in CHCl3. (b) Section
analysis of white line in tapping-mode AFM image of 7. (c) Structures
of uninsulated wires 7′ and 7″.
insulated π-conjugated polymers measured by TRMC.2d,21
7
was probably better at “relaying” charges, which led to
enhanced charge transport and mobility.22 This was because
the Ru-pyridyl coordinate bonds were efficiently hybridized due
to compatible energy levels and strong π-back-donation
between the metal and ligand in the organic−inorganic hybrid
orbitals. The observed conductivity of 7′ and 7″, however,
dropped over 2 orders of magnitude despite their identical
backbone structures (Figure S17−S19). The jump of L in 7
(43.4 nm) from 7′ (8.10 nm) suggests a 5-fold higher locking
(elongation) energy (ε) of the backbone of 7 based on the
wormlike chain model (L = ε/kT),19 and hence higher tensile
stress (dξ) in the conjugated backbone of 7. The electronic
transmission and β value over the elongated conjugated
backbone has been interpreted in terms of dξ,23 and this
gives the higher mobility of holes along the backbone of 7. In
addition, the lifetime of the charge carriers was 10-fold longer
than that of insulated PPE (Figure S15a). The extremely long
lifetime might come from the confinement of charges along the
conjugated backbone by not only α-CD units2b but also the
ring-peripherals of porphyrin units16a leading to the shielded
conjugated backbones from an access of counter superoxide
anions and/or hole scavengers such as amines.
A remarkable property of coordination polymer 7 is its
interconversion between monomer and polymer states under
certain conditions due to the reversibility of its coordinate
bonds. Carbon monoxide (CO) underwent ligand exchange
with the pyridyl groups on Ru(II) porphyrin complexes24 of 7,
because of its stronger coordination ability, thereby yielding
monomers 3 and 8. The resulting monomeric porphyrin
complex was expected to subsequently release CO upon UV
irradiation to reform molecular wire 7. Although molecular wire
7 was stable in toluene/EtOH at 55 °C,25 decomplexation into
monomers 3 and 8 occurred with 1 atm of CO, as confirmed by
SEC. Recomplexation of the air stable monomers could
subsequently be induced by UV irradiation of the resulting
solution (Figure 4). The degree of polymerization after
recomplexation (Mn = 2.7 × 104) was perfectly consistent
with that before decomplexation (Mn = 2.7 × 104). Thus, in
spite of the stability of molecular wire 7 and its monomeric
components under normal conditions, monomer-to-polymer
interconversion could be induced under specific conditions, i.e.,
either 1 atm of CO or UV irradiation. This property is unique
to metal-containing molecular wires bearing coordinate bonds,
and may be applied in molecular wiring applications such as
recycling and self-healing of wiring materials, in addition to as
sensory materials for CO.
cylinder model,19 the persistence length (L) of 7 was estimated
to be 43.4 nm, while the uninsulated wire 7′ exhibited a lower
persistence length (8.10 nm) confirming that the rigidity of the
backbone in 7 was significantly enhanced by the insulation. The
linearity of molecular wire 7 was investigated by atomic force
microscopy (AFM) experiments on cleaved graphite substrates.
The morphology of the singly dispersed molecular wires 7 was
highly linear, whereas 7′ exhibited aggregated structures
(Figures 2b and S11−S14). This suggested that the high
independency and linearity of 7 were reinforced by the
insulation, which inhibited π−π interactions and prevented the
backbone of the polymer from bending, and by the trans-
configuration of Ru−porphyrin complex. These results
suggested that through appropriate coordination polymer
design, rigid and linear transition-metal-containing IMWs
comparable to organic IMWs could be obtained.
We then examined the intramolecular charge mobility
characteristics of molecular wire 7 in the solid state by
combining the electrode-free transient conductivity measure-
ments throughtime-resolved microwave conductivity (TRMC),
with transient absorption spectroscopy (TAS).20 Upon
excitation, clear conductivity transients were observed as
shown in Figure 3a, with a delayed evolution of 10 μs and
Figure 3. (a) Conductivity transient observed for 7 upon excitation at
355 nm with 2.3 × 1015 photons cm−2. (b) Transient absorption
spectra of 7 at 0.2 (blue), 1 (violet), 3 (red), 10 (green), and 25 μs
(turquoise) after pulse irradiation at 355 nm with 2.4 × 1016 photons
cm−2.
ultralong lifetime over 1 ms. The delayed evolution is due to
triplet−triplet annihilation processes on the conjugated back-
bones, which is addressed clearly and quantitatively by the
conversion of the triplet state of 7 with Ru−porphyrin (400
nm) into the radical cations (620 nm) with an isosbestic point
as shown in Figure 3b. The effects of oxygen on the triplet
states were also observed for the transients, in addition to the
second-order kinetic analysis of the triplet states under a variety
of excitation conditions. (Figure S16). The complementary
In conclusion, we successfully synthesized a well-defined
insulated bridging ligand 3, which was a suitable building block
for the metal-containing molecular wire 7. Molecular wires
1744
dx.doi.org/10.1021/ja411665k | J. Am. Chem. Soc. 2014, 136, 1742−1745

Journal of the American Chemical Society
Communication
(4) Kiguchi, M.; Nakashima, S.; Tada, T.; Watanabe, S.; Tsuda, S.;
Tsuji, Y.; Terao, J. Small 2012, 8, 726.
(5) Yan, X.; Wang, F.; Zheng, B.; Huang, F. Chem. Soc. Rev. 2012, 41,
6042.
(6) (a) Leong, W. L.; Vittal, J. J. Chem. Rev. 2011, 111, 688.
́
(b) Gomez-Herrero, J.; Zamora, F. Adv. Mater. 2011, 23, 5311.
(7) Tam, A. Y.-Y.; Yam, V. W.-W. Chem. Soc. Rev. 2013, 42, 1540.
(8) (a) Zhao, Q.; Li, F.; Huang, C. Chem. Soc. Rev. 2010, 39, 3007.
(b) Dul, M.-C.; Pardo, E.; Lescouezec, R.; Journaux, Y.; Ferrando-
̈
Soria, J.; Ruiz-García, R.; Cano, J.; Julve, M.; Lloret, F.; Cangussu, D.;
Pereira, C. L. M.; Stumpf, H. O.; Pasan
Rev. 2010, 254, 2281.
́ ́
, J.; Ruiz-Perez, C. Coord. Chem.
(9) (a) Liang, W.; Shores, M. P.; Bockrath, M.; Long, J. R.; Park, H.
Nature 2002, 417, 725. (b) Ciszek, J. W.; Keane, Z. K.; Cheng, L.;
Stewart, M. P.; Yu, L. H.; Natelson, D.; Tour, J. M. J. Am. Chem. Soc.
2006, 128, 3179.
(10) (a) Wojtecki, R. J.; Meador, M. A.; Rowan, S. J. Nat. Mater.
2011, 10, 14. (b) Aida, T.; Meijer, E. W.; Stupp, S. I. Science 2012, 335,
813.
Figure 4. Schematic and SEC monitoring of polymer−monomer
interconversion (eluent: THF).
prepared by complexation of the bridging ligand with Ru(II)
porphyrins showed high intramolecular charge mobility in
addition to high rigidity and linearity. To our knowledge, this is
the first example of a one-dimensional coordination polymer
that displays this level of charge mobility. Finally, we
demonstrated the monomer-to-polymer interconversion of 7.
Such a transition is not feasible for conventional organic
molecular wires based on covalent bonds, and this feature could
be applied in efficient molecular wiring processes. These results
indicated that metal-containing insulated molecular wires have
potential for other applications beyond wiring materials.
(11) (a) Liu, Y.; Song, S.-H.; Chen, Y.; Zhao, Y.-L.; Yang, Y.-W.
Chem. Commun. 2005, 1702. (b) Yang, Y.-W.; Chen, Y.; Liu, Y. Inorg.
Chem. 2006, 45, 3014. (c) Han, C.; Zhang, L.; Li, H. Chem. Commun.
2009, 3545. (d) Chen, G.; Xia, J.; Li, Z.; Yu, G.-A.; Jin, S.; Liu, S. H. J.
Organomet. Chem. 2010, 695, 323. (e) Knight, L. K.; Vukotic, N.;
Viljoen, E.; Caputo, C. B.; Loeb, S. J. Chem. Commun. 2009, 5585.
(12) Xu, B.; Tao, N. J. Science 2003, 301, 1221.
(13) 7 × 10−6 G0 is slightly higher than that for carotenoids measured
by the same technique. Tao, N. J. Nat. Nanotechnol. 2006, 1, 173.
(14) Akae, Y.; Arai, T.; Koyama, Y.; Okamura, H.; Johmoto, K.;
Uekusa, H.; Kuwata, S.; Takata, T. Chem. Lett. 2012, 41, 806.
(15) This motif was reported by Collman et al. using Ru(II)
porphyrin dimer. (a) Collman, J. P.; McDevitt, J. T.; Yee, G. T.;
Leidner, C. R.; McCullough, L. G.; Little, W. A.; Torrance, J. B. Proc.
Natl. Acad. Sci. U.S.A. 1986, 83, 4581. (b) Collman, J. P.; McDevitt, J.
T.; Leidner, C. R.; Yee, G. T.; Torrance, J. B.; Little, W. A. J. Am.
Chem. Soc. 1987, 109, 4606.
ASSOCIATED CONTENT
* Supporting Information
Detailed synthetic procedures, chromatogram and spectral data.
This material is available free of charge via the Internet at
http://pubs.acs.org.
■
S
(16) Molecular wires were synthesized following a modified version
of the methods previously reported. (a) Marvaud, V.; Launay, J.-P.
Inorg. Chem. 1993, 32, 1376. (b) Endo, A.; Tagami, U.; Wada, Y.;
AUTHOR INFORMATION
Corresponding Author
terao@scl.kyoto-u.ac.jp
■
̂
Saito, M.; Shimizu, K.; Sato, G. P. Chem. Lett. 1996, 25, 243.
(17) Mw and Mn were calculated by polystyrene standard calibration.
(18) IR-vibration at 1936 cm−1, which stemmed from the carbonyl
stretching vibration of the Ru(CO) complex and disappeared as the
reaction proceeded.
Notes
The authors declare no competing financial interest.
(19) (a) Yamakawa, H.; Fujii, M. Macromolecules 1974, 7, 128.
(b) Yamakawa, H.; Yoshizaki, T. Macromolecules 1980, 13, 633.
(20) Saeki, A.; Koizumi, Y.; Aida, T.; Seki, S. Acc. Chem. Res. 2012,
45, 1193.
ACKNOWLEDGMENTS
■
This research was supported by the Funding Program for Next
Generation World-Leading Researchers and the PRESTO
program of the Japan Science and Technology Agency. H.M.
is grateful to JSPS for the Research Fellowship Program for
Young Scientists. We thank Dr. Hiroyasu Sato (Rigaku
Corporation) for his help in X-ray crystallographic analysis of 5.
(21) Sugiyasu, K.; Honsho, Y.; Harrison, R. M.; Sato, A.; Yasuda, T.;
Seki, S.; Takeuchi, M. J. Am. Chem. Soc. 2010, 132, 14754.
(22) There are a few reports about metal-containing polymers having
high charge mobility (>10−1 cm2 V−1 s−1) and bearing either 2D or 3D
motifs. (a) Grozema, F. C.; Houarner-Rassin, C.; Prins, P.; Siebbeles,
L. D. A.; Anderson, H. L. J. Am. Chem. Soc. 2007, 129, 13370.
(b) Feng, X.; Liu, L.; Honsho, Y.; Saeki, A.; Seki, S.; Irle, S.; Dong, Y.;
Nagai, A.; Jiang, D. Angew. Chem., Int. Ed. 2012, 51, 2618.
(23) (a) Franco, I.; Solomon, G. C.; Schatz, G. C.; Ratner, M. A. J.
Am. Chem. Soc. 2011, 133, 15714. (b) Bergfield, J. P.; Ratner, M. A.
Phys. Status Solidi B 2013, 250, 2249.
REFERENCES
■
(1) (a) Frampton, M. J.; Anderson, H. L. Angew. Chem., Int. Ed. 2007,
46, 1028. (b) Wenz, G. Inclusion Polymers; Springer-Verlag: Berlin,
2009.
(2) (a) Terao, J.; Tsuda, S.; Tanaka, Y.; Okoshi, K.; Fujihara, T.;
Tsuji, Y.; Kambe, N. J. Am. Chem. Soc. 2009, 131, 16004. (b) Terao, J.;
Tanaka, Y.; Tsuda, S.; Kambe, N.; Taniguchi, M.; Kawai, T.; Saeki, A.;
Seki, S. J. Am. Chem. Soc. 2009, 131, 18046. (c) Terao, J. Polym. Chem.
2011, 2, 2444. (d) Terao, J.; Ikai, K.; Kambe, N.; Seki, S.; Saeki, A.;
Ohkoshi, K.; Fujihara, T.; Tsuji, Y. Chem. Commun. 2011, 47, 6816.
(e) Terao, J.; Masai, H.; Fujihara, T.; Tsuji, Y. Chem. Lett. 2012, 41,
652. (f) Terao, J.; Wadahama, A.; Matono, A.; Tada, T.; Watanabe, S.;
Seki, S.; Fujihara, T.; Tsuji, Y. Nat. Commun. 2013, 4, 1691.
(3) Taniguchi, M.; Nojima, Y.; Yokota, K.; Terao, J.; Sato, K.; Kambe,
N.; Kawai, T. J. Am. Chem. Soc. 2006, 128, 15062.
(24) (a) Paulson, D. R.; Bhakta, S. B.; Hyun, R. Y.; Yuen, M.; Beaird,
C. E.; Lee, S. C.; Kim, I.; Ybarra, J., Jr. Inorg. Chim. Acta 1988, 151,
149. (b) Barley, M. H.; Dolphin, D.; James, B. R. J. Chem. Soc., Chem.
Commun. 1984, 1499.
(25) Decomplexation was also achieved using only toluene at 50 °C;
subsequently, recomplexation generated the molecular wire 7 with the
same degree of polymerization (Figure S1).
1745
dx.doi.org/10.1021/ja411665k | J. Am. Chem. Soc. 2014, 136, 1742−1745