Subscriber access provided by The University of British Columbia Library
Communication
“Doping” of Polyyne with An Organometallic Fragment Leads to Highly Conductive Metallapolyyne Molecular Wire Yuya Tanaka, Yuya Kato, Tomofumi Tada, Shintaro Fujii, Manabu Kiguchi, and Munetaka Akita J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b04484 • Publication Date (Web): 02 Jul 2018 Downloaded from http://pubs.acs.org on July 2, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 11 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Journal of the American Chemical Society
“Doping” of Polyyne with An Organometallic Fragment Leads to Highly Conductive Metallapolyyne Molecular Wire Yuya Tanaka,*† Yuya Kato,† Tomofumi Tada,*‡ Shintaro Fujii,§ Manabu Kiguchi,*§ Munetaka Akita,*† †
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, 226-8503, Japan ‡ Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, 226-8503, Japan. §
Department of Chemistry, School of Science, Tokyo Institute of Technology, Ookayama, Tokyo, 152-8551, Japan
ABSTRACT: Exploration of highly conductive mole-
cules is essential to achieve single-molecule electronic devices. The present paper describes the results on single-molecule conductance study of polyyne wires doped with the organometallic Ru(dppe)2 fragment, X(C≡C)n-Ru(dppe)2-(C≡C)n-X. The metallapolyyne wires end-capped with the gold fragments (X = AuL) are subjected to single-molecule conductance measurements with the STM break junction technique, which reveal the high conductance (10–3–10–2 G0; n = 2-4) with the low attenuation factor (0.25 Å–1) and the low contact resistance (33 kΩ). A unique ‘‘doping’’ effect of Ru(dppe)2 fragment was found to lead to the high performance as suggested by the hybrid DFT-NEGF (non equilibrium green function) calculation.
conductance performance, because the metal fragment with the d-electron system, just like a “dopant”, influences the energy levels of the frontier orbitals of the MMM junction6 and hinders cross-linking thanks to the bulky fragment.7 Herein we report synthesis of a series of metallapolyyne MMM junctions with the difunctional Ru(dppe)2 fragment, M-(C≡C)n-Ru(dppe)2(C≡C)n-M,8 which turn out to be highly conductive and even better than relevant organic polyyne systems as revealed by single molecule conductance study with the STM break-junction technique. theoretical prediction
this study organometallic metallapolyyne wire
polyyne wire doping Au Au Au
n
Au Au Au
Au Au Au
n
M
n
Au Au Au
M
highly conductive
Highly conducting molecules are essential to achieve reliable molecular devices, and much attention has been paid to development of efficient single metal electrode-molecule-metal electrode (MMM) junction.1 As a typical example of 1D (one-dimensional) compounds, carbyne, an allotrope of carbon, has attracted interest of many scientists, because theoretical calculations of the highly p-conjugated materials predict their high conductance.2 But an MMM junction with a polyyne linker, M-(C≡C)n-M (M: metal electrode), has not been subjected to experimental study3 due to the thermally cross-linkable polyyne unit and the potentially explosive nature of the precursors,4 e.g. H-(C≡C)n-H. In addition to the highly p-conjugated linker in MMM junction, effective electronic interaction between the molecule and the metal electrodes is another key factor realizing a highly conducting MMM junction.5 The interaction could be tuned by frontier orbital engineering via controlling the energy-levels of the conducting orbitals with respect to the Fermi energy level of the electrodes. We envisioned that insertion of an organometallic fragment into the polyyne linker improves the
no experimental study due to instablity
M Ph 2P
highly conductive stable precursor for break-junction study
PPh 2
Ru Ph 2P
PPh 2
Figure 1. An organic polyyne molecular wire and a metallapolyyne wire attached to Au electrodes.
There are several reports on formation of metal electrode-acetylide covalent bondings in the MMM junction through various in situ reactions including desilylative9 or dehydrogenative C-Au(electrode) bond formation10 and transmetallation.11,12 We, then, designed metallapolyyne molecular wires with the AuP(OMe)3 end groups 1n (n = 2-4). The terminal gold fragment is known to act as a leaving group to form a C-Au(electrode) covalent bond upon contacting with a gold electrode surface.11 Metallapolyyne wires 1n (n = 24) were prepared in 48-86% yields from the corresponding trimethylsilyl (TMS) protected precursors 2n (n = 2-4) by treatment with AuClP(OMe)3 in the presence of NaOMe (Figure 1). The N-heterocyclic carbene (NHC) gold complex 1NHC with the two butadiyne chains (n = 2) was also prepared in 37% yield in an analogous manner. The solid-state molecular structures of 1NHC, 23, and 24 are shown in Figure 2.13 The C≡C, ≡C–C≡, and ≡C-Au bond lengths are found to be within the ranges of 1.21–1.24, 1.36–1.37, and 1.98 Å, respectively, indicating
ACS Paragon Plus Environment
Journal of the American Chemical Society (a)
(b)
Individual traces
2x 1x
40
Au
C4
Ru
C4
Si
Au
C6
Ru
Si
86% 48% 49% 37% )
Si
60
2.0
50
3x
1.5
2x
1.0 0.5
1x 0
1.0 2.0 stretch length / nm
0
1
2 Δz / nm
3
4
0
1
2 Δz / nm
3
4
0
13
40
1x
30
5.0 x 10 –3 G 0
20
–1
–2
10 –3 0
0.5 1.0 1.5 Conductance / 10 -2 x G 0
2.0
–2
100
5.0
3x
4.0
2x
3.0 2.0
1x 1.0
80
14
1x
1.6 x 10 –3 G 0
60
2x
40
–3
20 0
NHC
0
3.0
0.0
24
n
0.10
Conductance / G 0
0
C8
Ru
–3 0.05
0.00
2.5
Si
23
1NHC
C8
AuL
C6
3.0
–2
log(G/G 0)
PPh 2
1 2 (n= 2, L = P(OMe) 3) 1 3 (n= 3, L = P(OMe) 3) 1 4 (n= 4, L = P(OMe) 3) ( 1NHC (n= 2, L = NHC)
n
2.0
log(G/G 0)
2n (n= 2-4)
n Ph P 2
Ru
1.0
stretch length / nm
Occurrence / a.u.
PPh 2
n
LAu
TMS
–1
0 0
PPh 2
2x
20
Occurrence / a.u.
n Ph P 2
Ru
Ph 2P
2.1 x 10 –2 G 0
1x
log(G/G 0)
0.04
0.02
Occurrence / a.u.
3x
0.06
Conductance / 10 -2 x G 0
TMS
NaOMe AuClL
PPh 2
2D histogram
0
12
0.08
0
Ph 2P
(c)
1D histogram linear scale
60 0.10 Conductance / G 0
clear bond alternation.14 The distances between the terminal acetylide carbon atoms are determined to be 1.16 (1NHC), 1.68 (23), and 2.17 nm (24) (Figure 2). Metallapolyynes wires 12-14 and 1NHC are stable under ambient conditions (air, moisture, and light) both in solutions and in solid states.15
Conductance / 10 -3 G 0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 11
1.0 2.0 3.0 stretch length / nm
4.0
0 0
4 1 2 3 Conductance / 10 -3 G 0
5
–4 0
1
2 Δz / nm
3
4
Figure 2. Synthetic scheme of 1 (n = 2-4), and 1 , and NHC 3 4 ORTEP drawings of 1 , 2 , and 2 with thermal ellipsoids drawn at the 50% probability level. Solvent molecules are omitted for clarity.
Figure 3. Single-molecule conductance studies of 1 -1 observed under ambient conditions (bias voltage; 100 mV). From the left to the right; individual traces, 1D histogram (linear scale), and 2D histogram.
Single molecule conductance study was performed using the STM-break junction technique16 with the bias voltage of 100 mV. When a tetraglyme solution of 12 was soaked onto the gold electrode, steps around 10–2 G0 were observed for the individual conductance traces (Figure 3a top). The molecular conductance of 12 has been determined to be 2.1 (±0.3) × 10–2 G0 on the basis of the 1D histogram, which shows the features of the single and double MMM junction formation as indicated by the allows in Figure 3b (top).17 The 2D histogram features the signals observed in the ranges from 10–1 to 10–2 G0 and up to 1 nm (Figure 3c (top), circled). The conductance of NHC complex 1NHC turns out to be almost identical to that of 12 (1NHC: 2.1 (±0.4) × 10–2 G0), suggesting that 12 and 1NHC form essentially the same MMM junctions. Furthermore, we also performed the STM-BJ measurement for the terminal bis(butadiynyl) complex 32, (dppe)2Ru(C≡C-C≡C-H)2, but no evidence of formation of an MMM junction has been obtained (See Supporting Information). These results indicate that the terminal Au functionalization is essential to form a reliable MMM junction in contrast to the previous reports on oligophenylene compounds with terminal acetylene units.10,18 This difference may be ascribed to the less acidic terminal acetylene parts in 32 due to the electron-donating Ru(dppe)2 fragments. STM-BJ studies reveal the conductance of 13 and 14 to be 5.0 (±0.9) × 10–3 (13) and 1.6 (±0.3) × 10–3 G0 (14) (Figure 3).
On the basis of the tunneling model, the relationship between the conductance (G) and the molecular length (L) can be described as follows,19,20
2 4
G = A exp(–b· L) where A and b represent the contact resistance and attenuation factor, respectively. The larger the A value and the smaller the b value, the better the performance of the molecular wires. The plots for log(G/G0) against the molecular lengths for 12-14 and related polyynyl wires are presented in Figure 4. It is notable that the conductance of the metallapolyyne molecular wires 1n is significantly larger than those of the common organic polyyne molecular wires with the similar molecular lengths having pyridine (4n) or thioether anchoring groups (5n). On the basis of the plots, the contact resistance of metallapolyyne wires 12-14 is determined to be 33 kW, which is considerably smaller than those of 4n (1.9 MW) and 5n (54 kW). The b value for the series of the ruthenium complexes 1n is 0.25 Å–1, which is somewhat smaller than those obtained for 4n (0.29 Å–1) and 5n (0.35 Å–1).
ACS Paragon Plus Environment
Page 3 of 11
Journal of the American Chemical Society 0
Ph 2P
Au Au Au
n
PPh 2
Ru Ph 2P
PPh 2
n
Au Au Au
Au Au Au
12 7
–3
Au Au Au
9
–4 N
1 2 molecular length / nm
Et 2P
Et 2P
PEt 2 Fe
Et 2P
Et 2P
PEt 2
Au Au Au
PEt 2
8
n
5n
3
PEt 2 Fe
S
S
4n
0
1
Au Au Au
7
14 8
n
1
Transimission / a.u.
13 6
N
(a)
Au Au Au
–2
–5
Au Au Au
6
Au Au N Au
Ph 2P
PPh 2
Ru Ph 2P
Au N Au Au
0.10.1
0.010.01
Au-1' 2-Au Au-1' 3-Au Au-1' 4-Au
PPh 2
9
Figure 4. Comparisons of the single-molecule conductance and molecular lengths of representative organic polyyne wires.
Furthermore, comparison is made with related molecular wires having covalent C-Au(electrode) bonds, which are regarded as the best organic molecular wires as estimated by single molecule measurements. When the conductance of the phenylene-ethynylene wire 6 (2.0 × 10–3 G0, dc-c = 1.7 nm)10 and the tetraphenylene wire 7 with the C(benzylic)-Au junctions (2.2 × 10–3 G0, dc-c = 1.9 nm)21 is compared with that of the metallopolyyne wire 13 with the similar molecular length (1.68 nm), the latter shows the performance slightly better than that of 6 and 7. The closely related molecular wire containing two iron units 8 shows conductance (1.1 × 10–3 G0, dc-c = 1.9 nm) comparable to that of 13 when the bias voltage is set to 50–200 mV.12 In order to clarify the origin of the high conductance of 1n, theoretical study on the basis of the hybrid density functional theory (DFT) and Non-equilibrium Green Function (NEGF) method has been carried out.22 The MMM junctions connected to the pyramidal Au35 clusters (abbreviated as Au-1’n-Au, where 1’n (n = 2-4) represents the -(C≡C)n-Ru(dppe)2-(C≡C)n- linkages) are chosen as models for the theoretical study and the terminal carbon atoms are attached to the Au electrodes with the on-top structures.23 The transmission spectra for Au-1’n-Au are shown in Figure 5a. The conductance value for them at the Fermi level can be estimated from the y intercepts (dots in Figure 5a) and determined to be 1.4 × 10–2 (n = 2), 7.7 × 10–3 (n = 3), and 3.4 × 10–3 G0 (n = 4), respectively, which are well coincident with the experimental values. For Au-1’2-Au, there are transmission peaks (indicated by the arrows) closely located at the Fermi energy level both for the occupied and unoccupied orbital regions. The separation between the transmission peaks, which corresponds to the HOMOLUMO gap, is found to be 0.34 eV, being much smaller than those for the model butadiynyl complex 32 estimated by the UV-Vis spectroscopy (4.23 eV) and the DFT calculation (3.65 eV). This feature indicates that the electronic structure of the molecular wire is significantly perturbed by the formation of the MMM junction. When the conduction orbitals are inspected, surprisingly, both of the conduction orbitals responsible for the transmission peaks found at –0.23 and 0.11 eV are akin to the HOMO of 32 (Figure 5b and
0.0010.001 -0.5 –0.5
occupied orbital -0.4
–0.4
-0.3
–0.3
-0.2
–0.2
unoccupied orbital
-0.1
–0.1
0
0.1
0
0.1
0.2
0.2
0.3
0.3
0.4
0.5
0.5
0.4
E-EF / eV
(b)
(c)
unoccupied orbital
32
LUMO (–0.84 eV) occupied orbital
Au-1' 2-Au (d)
orbital energy / eV
–1
log(G/G 0)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
HOMO (–4.49 eV)
HOMO–1 (–4.58 eV)
LUMO (–0.84)
3.65 eV
unoccupied conduction orbital 0.34 eV
HOMO (–4.49) occupied conduction orbital
Au
32
Au
Au-1'2-Au
Figure 5. (a) Transmission spectra of Au-1’n-Au (n = 2-4). (b) A part of the orbitals of Au-1’2-Au located at the transmission peaks around –0.29 eV and 0.10 eV (indicated by arrows), respectively. (c) A part of Kohn-Sham orbitals of 32. (d) Schematic orbital energy diagrams for 32 and Au-12’-Au. 5c), which is fully delocalized over the Ru(dppe)2(C≡CC≡C)2 chain. Considering that the energy level of the theoretically estimated HOMO of 32 (–4.49 eV)24,25 is higher than that of the Fermi level of gold (usually considered to be between –4.9 to –5. 3 eV from the vacuum level), charge transfer from the molecule to the metal electrodes may occur and the electron in the original filled HOMO orbital of the Ru(dppe)2(C≡C)2 moiety is partly removed to generate a new unoccupied orbital of Au-1’2-Au (Figure 5d). Therefore, the occupied and unoccupied conduction orbitals for Au-1’2-Au are derived from the same HOMO orbital as a result of the orbital splitting. Similar features are also noted for Au-1’3-Au and Au- 1’4-Au (See Supporting information). To the best of our knowledge, such an orbital splitting behavior has not been reported to date for any MMM junctions including 8 and 9.
ACS Paragon Plus Environment
Journal of the American Chemical Society 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
To clarify the effect of the metal fragments, hybrid DFT-NEGF study for the organic polyyne chains Au(C≡C)n-Au (n = 4, 6, 8, see Supporting information for details) has been performed. Interestingly, no orbital splitting behavior has been noted and the conductance values are inferior to those of Au-1’n-Au (n =2-4), suggesting that the ruthenium fragment is vital for the orbital splitting behavior and high conductance. Furthermore, the pyridine-anchored metallapolyyne 9 having the frontier orbital energies similar to that of 32 does not show the orbital splitting behavior but shifts of the frontier orbitals to lower energies upon MMM junction formation,6c indicating that the terminal anchor groups are also an essential factor. Although the detailed role of the terminal anchor groups are currently unclear, Au-1’n-Au can form Ru+=(C=C)n=Au– (electrode) type cumulenic canonical structures,26 which may enhance interactions between the Ru wires and the electrodes. It is noted that the orbital splitting behavior is caused by the orbital interactions (i.e., orbital hybridization) between the Ru-complexes and the Au clusters and is different from the recently reported observation of the redox27 or bias28 dependent switching behavior through MMM junctions, where the charge and the spin state play an important role. Generally, the narrow HOMO-LUMO gap is an important factor to achieve high conductance,29 and the present study reveals a new strategy to realize the molecular wire with an extremely narrow HOMO-LUMO gap via the MMM junction formation. To summarize, the synthesis and single molecule conductance of the metallapolyyne molecular wires with the Ru fragments are reported. The goldfunctionalized precursors are essential to achieve reliable formation of the MMM junctions. In contrast to organic polyyne wires, the organometallic metallapolyyne wires are stable enough to be subjected to the STM-BJ study. In addition, the highly conductive features of 1n (n = 2-4) with the low attenuation factor (0.25 Å–1) and the low contact resistance (33 kΩ) are found as a result of the covalent Au-C bond formations and fully delocalized conduction orbitals. The theoretical study reveals the unprecedented charge transfer interactions from the metal unit to the metal electrodes, which lead to orbital splitting behavior. As a result, the unique ‘‘doping’’ effect of the Ru(dppe)2 fragment has been unveiled. ASSOCIATED CONTENT
AUTHOR INFORMATION Corresponding Authors
*
[email protected] *
[email protected] *
[email protected] *
[email protected] Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT The present paper is dedicated to Professor Isao Saito on the occasion of his 77th birthday. We thank Prof. Ken Motokura (Tokyo Tech.) for assistance of XPS measurements. This work was supported by JSPS KAKENHI Grant Number 18K05139 and a research granted from The Murata Science Foundation. T. T. acknowledges the support by Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (Grant-in-Aid for Scientific Research on Innovative Areas, p-figuration: no. 26102017). The computations were performed by using the facility of the Research Center for Computational Science, Okazaki, Japan and the TSUBAME3.0 supercomputer in the Tokyo Tech.
REFERENCES (1)
(2) (3)
(4) (5) (6)
Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. Details of NMR, electrochemical and spectroscopic data, NHC and 3, self-assembled monolayer STM-BJ study of 1 2 study of 1 , and theoretical details (PDF) NHC X-ray crystallography for 1 (CIF) 3 X-ray crystallography for 2 (CIF) 4 X-ray crystallography for 2 (CIF)
Page 4 of 11
a) Nitzan, A.; Ratner, M. A. Science, 2003, 300, 1384-1389.; b) Chen, F.: Tao, N. J. Acc. Chem. Res. 2009, 42, 429-438.; c) Xiang, D.; Wang, X.; Jia,C.; Lee, T.; Guo, X. Chem. Rev. 2016, 116, 4318−4440. a) Crljen, Z.; Baranovic, G. Phys. Rev. Lett. 2007, 98, 116801. Single-molecule conductance studies of polyynes are limited to end-capped derivatives (R-(C≡C)n-R, (R = thioether,3a pyridine,3a-3c trimethylsilyl groups3d and others3a)). a) Moreno-García, P.; Gulcur, M.; Manrique, D. Z.; Pope, T.; Hong, W.; Kaliginedi, V.; Huang, C.; Batsanov, A. S.; Bryce, M. R.; Lambert, C.; Wandlowski, T. J. Am. Chem. Soc. 2013, 135, 12228−12240.; b) Milan, D. C.; Krempe, M.; Ismael, A. K.; Movsisyan, L. D.; Franz, M.; Grace, I.; Brooke, R. J.; Schwarzacher, W.; Higgins, S. J.; Anderson, H. L.; Lambert, C. J.; Tykwinski, R. R.; Nichols, R. J. Nanoscale, 2017, 9, 355-361.; c) Wang, C.; Batsanov, A. S.; Bryce, M. R.; Martin, S.; Nichols, R. J.; Higgins, S. J.; GarcíaSuárez, V. M.; Lambert, C. J. J. Am. Chem. Soc., 2009, 131, 15647-15654.; d) Milan, D. C.; Al-Owaedi, O. A.; Oerthel, M.-C.; Marqués-González, S.; Brooke, R. J.; Bryce, M. R.; Cea, P.; Ferrer, J.; Higgins, S. J.; Lambert, C. J.; Low, P. J.; Manrique, D. Z.; Martin, S.; Nichols, R. J.; Schwarzacher, W.; García-Suárez, V. M. J. Phys. Chem. C, 2016, 120, 15666-15674. Baughman, R. H. Science, 2006, 312, 1009–1110. Larade, B.; Taylor, J.; Mehrez, H.; Guo, H. Phys. Rev. B: Condens. Matter, 2001, 64, 075420. a) Schull, T. L.; Kushmerick, J. G.; Patterson, C. H.; George, C.; Moore, M. H.; Pollack, S. K.; Shashidhar, R. J. Am. Chem. Soc. 2003, 125, 3202-3203.; b) Blum, A. S.; Ren, T.; Parish, D. A.; Trammell, S. A.; Moore, M. H.; Kushmerick, J. G.; Xu, G.-L.; Deschamps, J. R.; Pollack, S. K.; Shashidhar, R. J. Am. Chem. Soc. 2005, 127, 10010-10011.; c) Mahapatro, A. K.; Ying, J.; Ren, T.; Janes, D. B. Nano Lett. 2008, 8, 2131-2136. d) Liu, K.; Wang, X.; Wang, F, ACS Nano, 2008, 2, 2315–2323.; e) Marqués-González, S.; Yufit, D. S.; Howard, J. A. K.; Martín, S.; Osorio, H. M.; García-Suárez, V. M.; Nichols, R. J.; Higgins, S. J.; Cea, P.; Low, P. J. Dalton Trans., 2013, 42, 338–341.; f) Sugimoto, K.; Tanaka, Y.; Fujii, S.; Tada, T.; Kiguchi, M.; Akita, M. Chem. Commun., 2016,
ACS Paragon Plus Environment
Page 5 of 11 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(7) (8)
(9) (10) (11) (12)
(13) (14)
(15)
Journal of the American Chemical Society 52, 5796-5799.; g) Bock, S.; Al-Owaedi, O. A.; Eaves, S. G.; Milan, D. C.; Lemmer, M.; Skelton, B. W.; Osorio, H. M.; Nichols, R. J.; Higgins, S. J.; Cea, P.; Long, N.; Albrecht, T.; Martin, S.; Lambert, C. J.; Low, P. J. Chem. Eur. J. 2017, 23, 2133–2143.; h) Tanaka, Y.; Kiguchi, M.; Akita, M. Chem. Eur. J., 2017, 23, 4741–4749. Tykwinski, R. R. Chem. Rec. 2015, 15, 1060−1074. For the intramolecular electron transfer studies of metal alkynyl complexes including Ru(dppe)2 or related metal fragments, see a) Bruce, M. I.; Low, P. J. Adv. Organomet. Chem. 2004, 50, 179 – 444.; b) Bruce, M. I.; Le Guennic, B.; Scoleri, N.; Zaitseva, N. N.; Halet, J. F. Organometallics, 2012, 31, 4701-4706.; c) Rigaut. S. Dalton Trans. 2013, 42, 15859-15863. Hong, W.; Li, H.; Liu, S.-X.; Fu, Y.; Li, J.; Kaliginedi, V.; Decurtins, S.; Wandlowski, T. J. Am. Chem. Soc. 2012, 134, 19425−19431 Olavarria-Contreras, I. J.; Perrin, M. L.; Chen, Z.; Klyatskaya, S.; Ruben, M.; van der Zant, H. S. J. J. Am. Chem. Soc. 2016, 138, 8465−8469. Millar, D.; Venkataraman, L.; Doerrer, L. H. J. Phys. Chem. C, 2007, 111, 17635–17639. a) Schwarz, F.; Kastlunger, G.; Lissel, F.; Riel, H.; Venkatesan, K.; Berke, H.; Stadler, R.; Lörtscher, E. Nano Lett. 2014, 14, 5932−5940.; b) Lissel, F.; Schwarz, F.; Blacque, O.; Riel, H.; Lörtscher, E.; Venkatesan, K.; Berke, H. J. Am. Chem. Soc. 2014, 136, 14560-14569. CCDC 1836794—1836796 contain the supplementary crystallographic data for the compounds appearing this paper. a) Bucher, J.; Wurm, T.; Nalivela, K. S.; Rudolph, M.; Rominger, F.; Hashmi, A. S. K. Angew. Chem., Int. Ed. 2014, 53, 3854–3858.; b) Chow, A. L.-F.; So, M.-H.; Lu, W.; Zhu, N.; Che, C.-M.; Chem. Asian J. 2011, 6, 544–553. No significant change of NMR spectra of 12-14 recorded in C6D6 was observed when left for 24 h under ambient conditions.
(16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27)
(28) (29)
Xu, B.; Tao, N. J. Science, 2003, 301, 1221–1223. For log scale 1D histogram, see Supporting Information Formation of a self-assembled monolayer of 12 on a gold mica substrate was observed. For details see Supporting Information. Kiguchi, M.; Kaneko, S. Phys. Chem. Chem. Phys., 2013, 15, 2253–2267. Tao, N. J. Nature Nanotech. 2006, 1, 173–181. Chen, W.; Widawsky, J. R.; Vázquez, H.; Schneebeli, S. T.; Hybertsen, M. S.; Breslow, R.; Venkataraman, L. J. Am. Chem. Soc. 2011, 133, 17160−17163. Tada, T.; Kondo, M.; Yoshizawa, K. J. Chem. Phys., 2004, 121, 8050-8057. Our theoretical study indicates that the on top structures are more stable than the hollow and bridge structures for the Au-acetylide contact. DFT calculations were performed at the B3LYP/LanL2DZ(Ru), 6-31G(d) level of theory. Experimentally estimated HOMO levels of 1n (n = 2-4) range from –4.88 to –5.25 eV, as obtained by cyclic voltammetry. Bruce, M. I. Coord. Chem. Rev. 2004, 248, 1603-1625. Liu, J.; Zhao, X.; Al-Galiby, Q.; Huang, X.; Zheng, J.; Li, R.; Huang, C.; Yang, Y.; Shi, J.; Manrique, D. Z.; Lambert, C. J.; Bryce, M. R.; Hong, W. Angew. Chem., Int. Ed. 2017, 56, 13061-13065 Schwarz, F.; Kastlunger, G.; Lissel, F.; Egler-Lucas, C.; Semenov, S. N.; Venkatesan, K.; Berke, H.; Stadler, R.; Lörtscher, E. Nature Nanotech. 2016, 11, 170-176. (a) Kaliginedi, V.; Moreno-García, P.; Valkenier, H.; Hong, W.; García-Suárez, V. M.; Buiter, P.; Otten, J. L. H.; Hummelen, J. C.; Lambert, C. J.; Wandlowski, T. J. Am. Chem. Soc. 2012, 134, 5262–5275.
ACS Paragon Plus Environment
Journal of the American Chemical Society 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 6 of 11
TOC graphic
ACS Paragon Plus Environment
6
theoretical prediction
Page 7 of 11
this study
Journal of the American Chemical Society
polyyne wire 1 2 Au Au 3 Au Au 4 Au Au n 5 6 7 highly conductive 8 9 experimental study no 10 due to instablity 11
organometallic metallapolyyne wire doping Au Au Au
n
M
Au Au Au n
M
M Ph 2P
highly conductive ACS Paragon Plus Environment stable precursor for
break-junction study
PPh 2
Ru Ph 2P
PPh 2
Ph 2P
TMS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
n Ph P 2
PPh 2
Ru PPh 2
Journal of theNaOMe American Chemical Society Ph 2P PPh AuClL 2 LAu Ru TMS n Ph P n 2 PPh 2
2n (n= 2-4)
Au
C4
Ru
1 2 (n= 2, L = P(OMe) 3) 1 3 (n= 3, L = P(OMe) 3) 1 4 (n= 4, L = P(OMe) 3) ( 1NHC (n= 2, L = NHC)
C4
C6
Si
Au
Ru
C8
n
AuL
86% 48% 49% 37% )
C6
23
1NHC
Si
Page 8 of 11
Ru
C8 Si
ACS Paragon Plus Environment
24
Si
(a)
Page 9 of 11
0
0.06
3x
0.04
2x
0.02
1x
40
2.1 x 10 –2 G 0
1x
2x
20
0
–1 log(G/G 0)
0.08
Occurrence / a.u.
0.10
0 1.0
2.0
3.0
0.05
0.00
stretch length / nm
0.10
0
1
2 Δz / nm
3
4
0
1
2 Δz / nm
3
4
Conductance / G 0 60
2.0
50
3x
1.5
2x
1.0 0.5
1x
Occurrence / a.u.
2.5
0
13
40
1x
30
5.0
x 10 –3 G
–1
0
20
log(G/G 0)
0
–2
–3
–2
10
0 1.0 2.0 stretch length / nm
0
3.0
–3 0
0.5 1.0 1.5 Conductance / 10 -2 x G 0
2.0
–2
100
3x
4.0
2x
3.0 2.0
1x 1.0
80
14
1x
1.6 x 10 –3 G 0
60
2x
40
log(G/G 0)
5.0
Occurrence / a.u.
Conductance / 10 -2 x G 0
2D histogram
12
0
Conductance / 10 -3 G 0
(c)
1D histogram linear scale
Journal of the American Chemical Society
60
Conductance / G 0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(b)
Individual traces
–3
20
0.0 0
1.0 2.0 3.0 stretch length / nm
4.0
0 0
4 1 2 3 ACS Paragon Plus Environment Conductance / 10 -3 G 0
5
–4 0
1
2 Δz / nm
3
4
Journal of the American Chemical Society 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
ACS Paragon Plus Environment
Page 10 of 11
Page 11 of 11 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Journal of the American Chemical Society
ACS Paragon Plus Environment
