Transition from a Metal-Localized Mixed-Valence Compound to a Fully Delocalized and Bridge-Biased Electrophore in a Ruthenium–Amine–Ruthenium Tricenter System

Article abstract of DOI:10.1002/chem.201601806

A series of cyclometalated diruthenium complexes with a redox-active amine bridge were synthesized. Depending on the terminal ligands of the ruthenium components and the substituent on the amine unit, the one-electron-oxidized state can be either in the f

Full text of DOI:10.1002/chem.201601806

DOI: 10.1002/chem.201601806
Communication
&
Mixed-Valence Compounds
Transition from a Metal-Localized Mixed-Valence Compound to
a Fully Delocalized and Bridge-Biased Electrophore in
a Ruthenium–Amine–Ruthenium Tricenter System
Jian-Hong Tang,[a, b] Jiang-Yang Shao,[a] Yan-Qin He,[a] Si-Hai Wu,[a] Jiannian Yao,[a, b] and Yu-
Wu Zhong*[a, b]
termini or bridge component or delocalized across the whole
molecule. As a continuation of our recent interests in mixed-
valence diruthenium complexes,[23] we present herein a rutheni-
um–amine–ruthenium tricenter system in which a transition
from a metal-localized mixed-valence compound to a fully de-
localized electrophore with extended conjugation, followed by
a bridge-biased electrophore, is realized by simply varying the
terminal ligands of the ruthenium components and the sub-
stituent on the central amine segment. Although known three-
center systems were reported to show different forms of
charge delocalization,[17–22] the realization of the three situa-
tions in one single system has not been documented to date.
For this purpose, seven amine-bridged diruthenium com-
plexes 1(PF6)2–7(PF6)2 were prepared (Figure 1). Each rutheni-
um component contains a RuÀC bond, which makes the RuIII/II
potential comparable to the amine oxidation potential.[24,25]
The bridging amine nitrogen atom is placed on the para posi-
tion of the metalating phenyl ring with respect to the RuÀC
bond. Such a connection mode ensures strong electronic cou-
pling between the ruthenium and amine components.[24,25]
Three terminal ligands with different electronic nature are used
for the ruthenium component, including the electron-rich
ligand 2,6-bis(N-methylbenzimidazolyl)pyridine (Mebip),[26]
2,2’:6’,2’’-terpyridine (tpy), and the electron-deficient ligand tri-
Abstract: A series of cyclometalated diruthenium com-
plexes with a redox-active amine bridge were synthesized.
Depending on the terminal ligands of the ruthenium com-
ponents and the substituent on the amine unit, the one-
electron-oxidized state can be either in the form of
a weakly or strongly coupled mixed-valence diruthenium
complex, a fully charge-delocalized three-center system,
or a bridge-biased electrophore. This transition among dif-
ferent electronic forms was supported by electrochemistry,
near-infrared absorption, electron paramagnetic reso-
nance, and density functional theory analysis.
Diruthenium complexes with a conjugated organic bridge
have received continuous attention since the pioneering work
of Creutz and Taube.[1] The studies on these complexes are
mainly driven by the impetus to rationalize the charge delocal-
ization between mixed-valence redox termini, which is of fun-
damental relevance to the photoinduced electron-transfer pro-
cesses occurring in natural systems and optoelectronic devi-
ces.[2–12] Furthermore, these redox-active complexes are useful
molecular materials for applications such as molecular elec-
tronics,[13] near-infrared electrochromism,[14] redox switches,[15]
and molecular logic gates and memories.[16]
methyl-4,4’,4’’-tricarboxylate-2,2’:6’,2’’-terpyridine
(Me3tctpy).
The electronic nature of the central amine unit is varied by
using different substituents (NO2, Cl, Me, and OMe). The syn-
thesis and characterization of these complexes are given in the
Supporting Information. These complexes were fully character-
ized by NMR spectra, MALDI-TOF mass spectra with consistent
isotope distribution (Figure 1b), and microanalysis. Complexes
6(PF6)2 and 7(PF6)2 have previously been reported by us regard-
ing their applications as molecular logic gates.[16] Complex
3(PF6)3 was isolated as the one-electron-oxidized form owing
to its low oxidation potential. Furthermore, some monoruthe-
nium complexes were prepared for the purpose of comparison
(see details in the Supporting Information).
Mixed-valence diruthenium complexes are normally treated
as two-center systems. However, when a redox-active or -non-
innocent bridge is used,[17–19] a three-center diruthenium com-
plex is obtained. Three-center mixed-valence systems are the
focus of a number of studies and they are interesting from
both a theoretical and applied perspective.[17–22] Depending on
the relative redox energy of the metal site and the bridge
component, the free spin can be either localized on the redox
[a] J.-H. Tang, Dr. J.-Y. Shao, Y.-Q. He, Dr. S.-H. Wu, Prof. J. Yao,
Prof. Y.-W. Zhong
Figure 2 shows the anodic cyclic voltammograms (CV) of
1(PF6)2–7(PF6)2 and differential pulse voltammogram (DPV) of
1(PF6)2. Three consecutive one-electron redox couples (E1, E2,
and E3) in the region of +0.1–+1.2 V vs Ag/AgCl are observed
(Supporting Information, Table S1). These waves are chemically
and electrochemically reversible, except those of 7(PF6)2, which
may have somewhat sluggish heterogeneous electron-transfer
kinetics judging from the relatively large potential splitting be-
Beijing National Laboratory for Molecular Sciences
CAS Key Laboratory of Photochemistry
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P. R. China)
E-mail: zhongyuwu@iccas.ac.cn
[b] J.-H. Tang, Prof. J. Yao, Prof. Y.-W. Zhong
University of Chinese Academy of Sciences, Beijing 100049 (P.R. China)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201601806.
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Figure 1. a) The compounds studied. b) Experimental (upper) and theoretical (lower) isotope distributions of each compound after (partial) loss of counteran-
ions.
show two redox waves (E1 and E2) with DE in the range of
360–520 mV (Supporting Information, Figures S1 and S2). The
E1 of monoruthenium complexes is generally higher than the
E1 but lower than the E2 of diruthenium complexes. Similarly,
the E2 of monoruthenium complexes is higher than the E2 but
lower than the E3 of diruthenium complexes. The reason for
this variation is complicated. Factors such as electronic delocal-
ization and electrostatic interaction may play important roles.
Owing to the relatively low oxidation potentials of 1(PF6)2–
7(PF6)2, the four available redox states of each complex are
readily available by stepwise chemical oxidation (Supporting
Information, Figures S3–S9) or by stepwise electrolysis using an
indium–tin oxide glass electrode (Supporting Information, Fig-
ures S10–S16). Each redox state of these complexes shows sig-
nificantly different absorption spectra, which makes them
useful in sophisticated logic gates.[16] We are particularly inter-
ested in the electronic structure and charge delocalization of
the one-electron-oxidized state of these complexes (13+–73+).
It is surprising and interesting that these open-shell complexes
show a set of absorption spectra in the near infrared (NIR)
region with significant difference in energy, shape, and intensi-
ty (Figure 3 in wavenumber scale; Supporting Information, Fig-
ure S17 in wavelength scale, see also Table S2).
Figure 2. Anodic CVs of 1(PF6)2–7(PF6)2 in 0.1m Bu4NClO4/CH3CN. The red
curve shown on the top is the DPV of 1(PF6)2. For details, see the Supporting
Information, Table S1.
tween the anodic and cathodic peaks of each redox couple
(ca. 100 mV). The redox waves of 1(PF6)2–3(PF6)2 with Mebip
progressively shift to the less-positive potential from 1(PF6)2–
3(PF6)2 when the substituent on the amine unit changes from
NO2 to Cl and OMe. The potential separation between E1 and
E2 (DE2À1) of 1(PF6)2–3(PF6)2 increases from 90 to 170 and
220 mV, respectively (Supporting Information, Table S1). Com-
plexes 4(PF6)2–6(PF6)2 with tpy show a very similar set of redox
potentials as 2(PF6)2. The redox waves of 7(PF6)2 with Me3tctpy
shift to the more positive potential region with respect to
those of 6(PF6)2.
The NIR absorption of 13+ is weak (emax =3900 LmolÀ1 cmÀ1),
abroad (Dn˜1/2 =3780 cmÀ1), and low in energy (Emax
=
5210 cmÀ1; lmax =1920 nm). In stark comparison, the NIR ab-
sorptions of 63+ and 73+ are very intense (emax
30000 LmolÀ1 cmÀ1), sharp (Dn˜1/2 around 2000 cmÀ1), and
higher in energy (Emax =6040, 6770 cmÀ1, respectively; lmax
>
=
1660 and 1480 nm, respectively). Complexes 23+–53+ show NIR
absorptions with intermediate intensity, broadness, and energy
(Emax: 5490–5890 cmÀ1; lmax: 1700–1820 nm). Furthermore, the
NIR absorptions of 43+ and 53+ are highly asymmetric. The
ratio between the bandwidth at the high and low energy side
is around 2.5 for 43+ and 53+, while this ratio is around 2.0 for
In comparison, the central bridging ligands show some irre-
versible oxidations around +1.0 V and the model monoruthe-
nium complexes 8(PF6)2–14(PF6) with an amine substituent
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Figure 3. NIR absorption spectra of 13+–73+ in CH2Cl2 as a function of wave-
numbers. ? artifacts. Spectra with the x-axis in wavelength scale are shown
in the Supporting Information, Figure S17; the spectroscopic data are sum-
marized in Table S2.
13+ and 63+, and 1.6 for 23+, 33+, and 73+, respectively. Some
weak absorption bands at around 8700 cmÀ1 (1100 nm) seem
to be buried in the higher-energy side of these NIR transitions.
In the two-electron-oxidized states (14+–74+), all complexes
show intense absorptions at this region. They are assigned to
the bridge to metal charge transfer transitions.
Figure 4. EPR signals of 13+-73+ at room temperature (black curves) and
77 K (red curves).
Based on the spectroelectrochemical results, the NIR absorp-
tions of 13+–73+ have different nature of solvent dependence.
Complexes 23+–63+ show very similar NIR absorptions (in term
of shape and energy) in CH2Cl2, CH3CN, and DMF. However,
those of 13+ and 73+ show a large and small solvent depend-
ence, respectively (Supporting Information, Figure S18). Fur-
thermore, the one-electron-oxidized states of the model mono-
ruthenium complexes, 82+–142+, show absorptions with much
higher energies (Emax: 9030–12270 cmÀ1; lmax: 815–1110 nm,
see the Supporting Information, Table S2 and Figures S19 and
S20).
type weakly coupled mixed-valence compound (EPR inactive
at room temperature but with rhombic signal at low tempera-
ture; weak, broad, low-energy, and solvent-dependent interva-
lence charge-transfer (IVCT) band). The electronic coupling Vab
of 13+ is estimated to be 520 cmÀ1 according to the Hush for-
mula, Vab =(mgeEmax)/eRab (see details in the Supporting Informa-
tion), where mge is the transition dipole moment, e is the ele-
mentary charge, and Rab is the diabatic electron-transfer dis-
tance, which is taken to be the geometrical RuÀRu distance
(10.7 ꢁ).
Complexes 23+–73+ show intense, asymmetric, and solvent-
independent NIR transitions. They are assigned to class II–III or
fully delocalized class III compounds. On the basis of the EPR
results, these compounds may have somewhat different
degree of spin density distribution. The spin densities of 23+
and 33+ are possibly more biased toward the ruthenium com-
ponents, while those of 63+ and 73+ are more biased toward
the bridge.
The open-shell complexes 13+–73+ are paramagnetic. They
show an interesting trend of electron paramagnetic resonance
(EPR) signal changes (Figure 4). Complexes 13+ and 23+ did
not show any EPR signals at room temperature. Complex 33+
shows a weak EPR signal at room temperature. However, the
signals of 43+–73+ at room temperature are sharp and intense
(g=2.05), suggesting a large proportion of organic radicals. All
complexes are EPR active at 77 K in frozen CH3CN. However,
the shape of the signal is very different. Complex 13+ display
a rhombic signal at 77 K, with g1, g2, and g3 of 2.330, 2.127,
1.930, respectively. Complexes 23+ and 33+ display axial EPR
signals at 77 K. Rhombic or axial EPR signals at low tempera-
ture are suggestive of low-spin RuIII species.[27] The EPR signals
of 43+ and 53+ at 77 K are much broader with respect to those
at room temperature. The EPR signals of 63+ and 73+ at 77 K
are only slightly broader with respect to corresponding signals
at room temperature. Overall, a trend from EPR inactive to
a sharp single-line EPR signal was observed at room tempera-
ture from 13+ through 73+. At low temperature, the EPR sig-
nals change from rhombic to axial and single-line signals with
The above transition from a metal-localized mixed-valence
compound to a delocalized electrophore with varied spin den-
sity distribution can be understood by comparing the amine
oxidation potential of the mono-substituted triarylamines 15–
18[28] and the RuIII/II potential of the monoruthenium complexes
19(PF6)–21(PF6)[25] with
a different NNN auxiliary ligand
(Figure 5). Complex 19(PF6) with Mebip has a much lower RuIII/II
potential with respect to the amine oxidation potential of 15–
17 with NO2, Cl, or Me substituents. In this sense, the free spin
of 13+–33+ should be biased toward the ruthenium compo-
nents. When tpy or Me3tctpy NNN ligand is used, the RuIII/II po-
tential becomes comparable to the N(+/0) potential and a tran-
sition to fully delocalized or bridge-biased electrophores is ex-
pected.
the g anisotropy descending from 13+–73+
.
On the basis of the above electrochemical, NIR absorption,
and EPR data, complex 13+ is considered to be a [RuIII-N-RuII]-
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Figure 5. Comparison of the amino oxidation potential of the mono-substi-
tuted triarylamines 15–18 (vs SCE) and RuIII/II potential of the monorutheni-
um complexes 19(PF6)–21(PF6) (vs. Ag/AgCl). Potential conversion rule: E(vs
Ag/AgCl)=E(vs SCE)+0.04 V.
The structures of 13+–73+ were optimized with different
hybrid functional. The method of UB3LYP/LANL2DZ/6-31G*/
CPCM(CH3CN) (see details in the Supporting Information) was
firstly used. All complexes show rather delocalized spin density
(aÀb) distribution (Supporting Information, Figure S21). When
the long-range-corrected functional UCAM-B3LYP was used,
the spin density of 13+–63+ is largely dominated by one ruthe-
nium component with minor distributions from the central
amine bridge, while the spin density of 73+ is dominated by
the amine bridge (Supporting Information, Figure S22). Stimu-
lated by the recent reports by Kaupp and Lambert,[29,30] we
used the custom-defined UBLYP functional with 30% Hartree–
Fock (H-F) exchange to find that a transition from the rutheni-
um-localized to bridge-biased spin density distribution could
be partially reproduced (Figure 6). Using this method, the spin
density of 13+, 23+, and 43+ was calculated to be dominated
by one ruthenium component with minor contributions from
the amine bridge, while that of 33+, 53+, 63+, and 73+ was
rather delocalized. The spin density of 33+ and 53+ is more
biased toward one ruthenium component, while that of 63+
and 73+ is more biased toward the amine bridge.
Figure 7. TDDFT results of 13+, 33+, and 73+. Others are shown in the Sup-
porting Information, Figure S23 and Table S3.
The TDDFT calculations of 13+–73+ using the same UBLYP
with 30% H-F exchange method reproduce the NIR transitions
in the similar wavelength region (Figure 7; Supporting Informa-
tion, Figure S23 and Table S3). All calculated transitions are do-
minated by the b spin transition from the highest-occupied
spin orbital (HOSO) to the lowest-unoccupied spin orbital
(LUSO). In agreement with the experimental results, the calcu-
lated NIR transition of 13+ and 73+ has the smallest and largest
oscillator strength, respectively (f=0.3673 and 0.6513, respec-
tively). The calculated NIR transitions of 13+, 23+, and 43+ have
a dominant IVCT character. In contrast, the calculated NIR tran-
sitions of 33+–73+ are best described as charge resonance tran-
sitions and those of 63+ and 73+ have a big contribution from
the charge transfer transition from two ruthenium components
Figure 6. DFT-calculated spin density distribution of 13+–73+. The numbers below the structures shows the contributions of two ruthenium ions, the central
nitrogen atom, and three phenyl rings of the triarylamine group (Ru1, Ph1, N, Ph3, Ph2, and Ru2 as dictated by the structure in the left upper corner). Calcula-
tion method: UBLYP with 30% H-F exchange/LANL2DZ/6-31G*/CPCM in CH3CN solvent.
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[5] S. Heckmann, C. Lambert, Angew. Chem. Int. Ed. 2012, 51, 326; Angew.
Chem. 2012, 124, 334.
[6] P. J. Low, Coord. Chem. Rev. 2013, 257, 1507.
[7] M. Yoshida, M. Kondo, T. Nakamura, K. Sakai, S. Masaoka, Angew. Chem.
Int. Ed. 2013, 52, 13597; Angew. Chem. 2013, 125, 13842.
[8] Z. Cao, B. Xi, D. S. Jodoin, L. Zhang, S. P. Cummings, Y. Gao, S. F. Tyler,
P. E. Fanwick, R. J. Crutchley, T. Ren, J. Am. Chem. Soc. 2014, 136, 12174.
[9] M. Parthey, J. B. G. Gluyas, M. A. Fox, P. J. Low, M. Kaupp, Chem. Eur. J.
2014, 20, 6895.
[10] G. E. Pieslinger, P. Albores, L. D. Slep, L. M. Baraldo, Angew. Chem. Int. Ed.
2014, 53, 1293; Angew. Chem. 2014, 126, 1317.
[11] D.-D. Kong, L.-S. Xue, R. Jang, B. Liu, X.-G. Meng, S. Jin, Y.-P. Ou, X. Hao,
S.-H. Liu, Chem. Eur. J. 2015, 21, 9895.
[12] T. Cheng, Y. N. Tan, Y. Zhang, Y. Y. Zhang, M. Meng, H. Lei, L. Chen, C. Y.
Liu, Chem. Eur. J. 2015, 21, 2353.
[13] J.-P. Launay, Coord. Chem. Rev. 2013, 257, 1544.
to the central aminium unit. These results suggest that the
transition from a mixed-valence compound to a delocalized
and bridge-biased electrophore is possible. However, due to
the strong dependence of the DFT and TDDFT calculations on
the functional and parameters used, these results should be
taken with care.
In conclusion, a series of cyclometalated diruthenium com-
plexes with a redox-active amine bridge were prepared and ex-
amined. The most interesting finding is that simple variation of
the terminal ligands of the ruthenium components and the
substituent on the amine segment can completely change the
electronic structures and degrees of charge delocalization of
these complexes in the one-electron-oxidized state. In this
sense, a transition from a weakly coupled mixed-valence com-
pound to a fully delocalized tricenter electrophore, followed
by a bridge-biased electrophore, was realized in a single
system. This finding is of great importance for the design of
new mixed-valence compounds and multi-center redox-active
systems with tunable electronic structures and functions.
[14] a) W. Kaim, Coord. Chem. Rev. 2011, 255, 2503; b) Y.-W. Zhong, C.-J. Yao,
H.-J. Nie, Coord. Chem. Rev. 2013, 257, 1357.
[15] R. Gautam, J. J. Loughrey, A. V. Astashkin, J. Shearer, E. Tomat, Angew.
Chem. Int. Ed. 2015, 54, 14894; Angew. Chem. 2015, 127, 15107.
[16] B.-B. Cui, J.-H. Tang, J. Yao, Y.-W. Zhong, Angew. Chem. Int. Ed. 2015, 54,
9192; Angew. Chem. 2015, 127, 9324.
ˇ
[17] S. Zꢂlis, R. F. Winter, W. Kaim, Coord. Chem. Rev. 2010, 254, 1383.
[18] C. P. Kubiak, Inorg. Chem. 2013, 52, 5663.
[19] B. Sarkar, D. Schweinfurth, N. Deibel, F. Weisser, Coord. Chem. Rev. 2015,
293, 250.
Acknowledgements
[20] B. S. Brunschwig, C. Creutz, N. Sutin, Chem. Soc. Rev. 2002, 31, 168.
[21] J.-P. Launay, C. Coudret, C. Hortholary, J. Phys. Chem. B 2007, 111, 6788.
[22] C. Lambert, G. Nçll, J. Schelter, Nat. Mater. 2002, 1, 69.
[23] Y.-W. Zhong, Z.-L. Gong, J.-Y. Shao, J. Yao, Coord. Chem. Rev. 2016, 312,
22.
[24] J.-J. Shen, Y.-W. Zhong, Sci. Rep. 2015, 5, 13835.
[25] C.-J. Yao, H.-J. Nie, W.-W. Yang, J.-Y. Shao, J. Yao, Y.-W. Zhong, Chem. Eur.
J. 2014, 20, 17466.
We thank the National Natural Science Foundation of China
(grants 21271176, 21472196, 21521062, and 21501183), the
Ministry of Science and Technology of China (grant
2012YQ120060), and the Strategic Priority Research Program of
the Chinese Academy of Sciences (grant XDB 12010400) for
funding support.
[26] W.-W. Yang, Y.-W. Zhong, S. Yoshikawa, J.-Y. Shao, S. Masaoka, K. Sakai, J.
Yao, M.-a. Haga, Inorg. Chem. 2012, 51, 890.
[27] S. Patra, B. Sarkar, S. M. Mobin, W. Kaim, G. K. Lahiri, Inorg. Chem. 2003,
42, 6469.
[28] R. F. Nelson, R. N. Adams, J. Am. Chem. Soc. 1968, 90, 3925.
[29] M. Renz, K. Theilacker, C. Lambert, M. Kaupp, J. Am. Chem. Soc. 2009,
131, 16292.
Keywords: density functional calculations · electrochemistry ·
electron transfer · mixed-valence compounds · ruthenium
[1] C. Creutz, H. Taube, J. Am. Chem. Soc. 1969, 91, 3988.
[2] a) D. M. D’Alessandro, F. R. Keene, Chem. Rev. 2006, 106, 2270; b) P.
Aguirre-Etcheverry, D. O’Hare, Chem. Rev. 2010, 110, 4839.
[3] W. Kaim, G. K. Lahiri, Angew. Chem. Int. Ed. 2007, 46, 1778; Angew.
Chem. 2007, 119, 1808.
[30] M. Kaupp, M. Renz, M. Parthey, M. Stolte, F. Wurthner, C. Lambert, Phys.
Chem. Chem. Phys. 2011, 13, 16973.
Received: April 18, 2016
[4] J. Hankache, O. S. Wenger, Chem. Rev. 2011, 111, 5138.
Published online on && &&, 0000
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COMMUNICATION
Controlled at the periphery: Depend-
ing on the terminal ligands of the ruthe-
nium components and the substituent
on the amine unit, the one-electron-oxi-
dized state of the [Ru-N-Ru] three-
center complex (see figure) can be
either in the form of a weakly coupled
mixed-valence diruthenium complex,
a fully charge-delocalized tricenter
system, or a bridge-biased electrophore
supported by two ruthenium compo-
nents.
&
Mixed-Valence Compounds
J.-H. Tang, J.-Y. Shao, Y.-Q. He, S.-H. Wu,
J. Yao, Y.-W. Zhong*
&& – &&
Transition from a Metal-Localized
Mixed-Valence Compound to a Fully
Delocalized and Bridge-Biased
Electrophore in a Ruthenium–Amine–
Ruthenium Tricenter System
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