Reversible cargo shipping between orthogonal stations of a nanoscaffold upon redox input

Article abstract of DOI:10.1039/c4dt00849a

The sterically shielded terpyridine 5 was prepared, both as a new ligand and as part of the four-station nanoscaffold 2. Mixing of terpyridine 5, the parent phenanthroline 4 and the shielded phenanthroline 3 in the presence of Zn²⁺ (1:1:1:1) fu

Full text of DOI:10.1039/c4dt00849a

Volume 43 Number 25 7 July 2014 Pages 9365–9796
Dalton
Transactions
An international journal of inorganic chemistry
www.rsc.org/dalton
ISSN 1477-9226
PAPER
Michael Schmittel et al.
Reversible cargo shipping between orthogonal stations of a nanoscaffold
upon redox input

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Reversible cargo shipping between orthogonal
stations of a nanoscaffold upon redox input†
Cite this: Dalton Trans., 2014, 43,
9438
Soumen K. Samanta, Anup Rana and Michael Schmittel*
The sterically shielded terpyridine 5 was prepared, both as a new ligand and as part of the four-station
nanoscaffold 2. Mixing of terpyridine 5, the parent phenanthroline 4 and the shielded phenanthroline 3 in
the presence of Zn2+ (1 : 1 : 1 : 1) furnished quantitatively the inverse HETTAP complex [Zn(4)(5)]2+ by self-
sorting, while in the presence of Cu+ the HETPHEN complex [Cu(3)(4)]+ was preferred (89%). Due to the
akin coordination preferences of Cu2+ and Zn2+, the above self-sorting was implemented for Cu+/Cu2+
on nanoscaffold 2, the latter equipped with the binding motifs of 3 (PhenAr2) and 5 (TerpyAr2). When 2
was reacted with Cu+ and phenanthroline (4) in a 1 : 2 : 2 ratio, only the PhenAr2 stations became involved
in complex formation (= Cu1phen). In contrast, upon oxidative formation of Cu2+, ligand 4 was exclusively
moved to the TerpyAr2 stations (Cu1terpy). Electrochemical oxidation–reduction prompted the cargo to be
shipped reversibly on a subsecond time scale between the two different stations of 2.
Received 20th March 2014,
Accepted 6th May 2014
DOI: 10.1039/c4dt00849a
www.rsc.org/dalton
complex [M(3)2]n+ with Mn+ = Cu+, Ag+, Zn2+. In presence of a
Introduction
sterically slim counterpart, like the parent phenanthroline (for
Many enzymes use translocation processes1 (ligand and metal) HETPHEN)12a,b or terpyridine (for HETTAP),12c,d 3 and Mn+
to initiate fascinating biological protocols. Likewise, shifting will afford quantitatively the heteroleptic complex.
subcomponents in either supramolecular2 or molecular3 struc-
For the present study, structural aspects known from the
tures has been ingeniously utilised in fascinating abiological HETTAP and HETPHEN protocols guided our design of the
devices.4,5 To control reversible motion in multistable devices new terpyridine 5 that is sterically shielded by aryl groups
by switching, the binding of the movable part (Kassoc) has to (TerpyAr2). The shielding does not prevent, but slows down
favour a particular site over the other depending on the given formation of the homoleptic complex [M(TerpyAr2)2]n+ thus
input, such as chemicals,6 redox equivalents7 or light.8
favouring heteroleptic complexation. The new scaffold 2 arises
As reported by Sauvage and coworkers,9 changing the oxi- by attaching the binding motifs of both PhenAr2 and TerpyAr2
dation state of copper from +I to +II leads to an altered coordi- sites to a zinc(II) porphyrin core. Depending on the oxidation
nation preference: the copper(I) ion prefers tetracoordination, state of the copper ions a switch in the self-sorting13 should
while the copper(II) ion is best accommodated in a penta- or lead to cargo shuffling (cargo = copper + ligand 4) between the
hexacoordination. Remodeling this principle, we present here PhenAr2 and TerpyAr2 stations on the scaffold (Fig. 1). As such,
the reversible shipping of cargo between two different sites on our example is a very rare case of redox initiated self-sorting14
a scaffold by applying electrochemical stimuli (Fig. 1). Our in solution.
design of reversible cargo shipping relies on two heteroleptic
binding algorithms developed in our group, i.e. the HETPHEN
and HETTAP concepts,10 instead of using topological con-
straints, as is amply done in rotaxanes and catenanes.11 Our
concepts are based on the use of a bulky 2,9-diaryl substituted
phenanthroline (PhenAr2), e.g., ligand 3 (Chart 1),12 whose
front-side shielding prevents the formation of the homoleptic
Center of Micro- and Nanochemistry and Engineering, Organische Chemie I,
Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany.
E-mail: schmittel@chemie.uni-siegen.de
†Electronic supplementary information (ESI) available: 1H, 1H–1H COSY, 13C
NMR, ESI-MS, cyclic voltammograms, DOSY and DFT optimised structures. See
DOI: 10.1039/c4dt00967c
Fig. 1 Controlling cargo transport between two stations via self-sorting
by oxidation/reduction. Cu1phen = [Cu2(2)(4)2]2+ Cu1terpy = [Cu2(2)(4)2]4+
.
.
9438 | Dalton Trans., 2014, 43, 9438–9447
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Chart 1 Scaffold 2 and ligands 3–5 used in the present study.
Results and discussion
Synthesis
The new compounds 2 and 5 (Scheme 1) were prepared via
established protocols. First, 2,4,6-trimethylphenylboronic acid
was treated with 2,6-dibromopyridine via Suzuki coupling to
furnish compound 6, which was reacted further on with
2-(2,4,6-trimethylphenyl)-[1,10]-phenanthroline
ligand 5.
to
afford
Scheme 1 Synthesis of ligands 2, 5 and 8. (a) Zinc(II)-5,15-bis(4-iodo-
phenyl)-10,20-bis(4-trimethylsilylethynylphenyl)porphyrin,
Pd(PPh3)4,
For the preparation of scaffold 2 with two different kinds of
stations, pyridine was subjected to bromo/lithium
NEt3, DMF, 90 °C, 12 h, 58%. (b) KOH, THF, MeOH, room temperature,
90%. (c) Pd(PPh3)4, NEt3, DMF, 90 °C, 12 h, 35%.
6
a
exchange and then reacted with [1,10]-phenanthroline to
afford the terpyridine-analog 7. A follow-up reaction with 1,4-
diiododurene/n-BuLi furnished 8 serving as the direct precur-
sor for the preparation of scaffold 2. To finalise the synthesis,
zinc(II)-5,15-bis(4-iodophenyl)-10,20-bis(4-trimethylsilylethynyl-
phenyl)porphyrin was first treated with the known shielded
phenanthroline 912d in presence of Pd(PPh3)4 to afford 10,
which after deprotection of the trimethylsilyl groups furnished
11. In the final step, 11 was reacted with ligand 8 in a second
Sonogashira coupling to provide the desired target
2
(Scheme 1). Scaffold 2 was easily and fully characterised by
spectroscopic means.
Complexation properties of 5
Fig. 2 Partial 1H NMR spectra of (a) 5 in CD2Cl2, (b) 3 in CDCl3, (c) [Cu-
(5)2]PF6 in CD2Cl2, (d) equimolar mixture of 4, 5 and Cu+ in CD2Cl2 and
(e) equimolar mixture of 4, 5 and Zn2+ (in CD2Cl2–CD3CN = 3 : 1).
Insight into the binding properties of 5 was received by react-
ing 0.5 equiv. of [Cu(CH3CN)4]PF6 with 5 in CD2Cl2. H NMR
1
and ESI-MS of the resulting yellow solution revealed formation
of the homoleptic complex [Cu(5)2]+ by showing two different
sets of upfield shifted mesityl protons at 5.62 and 6.19 ppm
(Fig. 2) and a mass peak at 1051.0 Da. Assuming a coordi-
nation number 4 for Cu+, [Cu(5)2]+ may actually form in three
isomeric structures, i.e. iso-I, iso-II & iso-III (Charts 2 and 3)
due to six nitrogen atoms being available from two ligands 5.
In iso-I, Cu+ engages exclusively with the phenanthroline nitro-
gen atoms (N2, N3, N2′ and N3′), while the pyridyl nitrogen
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 9438–9447 | 9439

View Article Online
Paper
Dalton Transactions
likely, steric crowding by the mesityl groups prevents Cu2+ to
extend its coordination number from 4 to 5/6.
Heteroleptic complexes with ligand 5
When a 1 : 1 : 1 mixture of 4, 5 and copper(I) ions was reacted
in CD2Cl2, the homoleptic complexes [Cu(4)2]+ and [Cu(5)2]+ as
well as the heteroleptic complex [Cu(4)(5)]+ were observed in
the ESI-MS, with the latter generating the major peak (at 745.5
Da). The 1H NMR data corroborate the formation of both com-
plexes [Cu(4)(5)]+ and [Cu(5)2]+ (Fig. 2), with peaks at 5.63 &
5.69 ppm being diagnostic for [Cu(4)(5)]+ and those at 5.62
and 6.19 ppm (Fig. 2) for [Cu(5)2]+. Unfortunately, character-
istic signals for [Cu(4)2]+ were obscured in the aromatic region.
The DFT optimised structure of [Cu(4)(5)]+ predicts that the
metal ion is engaged in coordination with both phenanthro-
line nitrogens (N2 and N3) of 5, while the pyridyl nitrogen
atom (N1) remains nonbonded. Strong π⋯π interactions (C⋯C
= 4.033 Å and 4.043 Å) between the two mesityl units of 5 and
4 are observed. Other isomers of [Cu(4)(5)]+ involving N1(pyri-
dyl)→Cu interactions were not located computationally.
Chart 2 Cartoon representations of compound
5 and the three
isomers (iso-I, iso-II & iso-III) of the homoleptic complex [Cu(5)2]+.
Superscript letters A, B and C denote conformations.
When an equimolar mixture of 4, 5 and Cu(I) was oxidised
in CV, a broad wave at 540–713 mV was observed corres-
ponding to oxidation of all three copper complexes, [Cu(4)2]+,
[Cu(5)2]+ and [Cu(4)(5)]+. In contrast, the cathodic scan gener-
ated a single, irreversible peak at Epc = 251 mV assigned to the
reduction of [Cu(4)(5)]2+ exclusively. Indeed, the independently
prepared complex [Cu(4)(5)]2+ (vide infra) showed a reduction
wave at Epc = 245 mV. Apparently, upon oxidation, both
homoleptic complexes [Cu(5)2]2+ and [Cu(4)2]2+ reorganised to
[Cu(4)(5)]2+ so that each copper(II) ion would realise pentacoor-
dination in the heteroleptic complex.
Chart 3 Possible complexes resulting from ligands 3, 4, 5 and the
When a 1 : 1 mixture of 4 and 5 was treated with 1 equiv. of
Zn(OTf)2 in CD2Cl2–CD3CN = 3 : 1, the heteroleptic complex
[Zn(4)(5)]2+ formed quantitatively as documented by spectro-
scopic data. The ESI mass spectrum shows peaks at 370.0 Da
and 888.3 Da diagnostic for the doubly charged [Zn(4)(5)]2+
and singly charged [Zn(4)(5)](OTf)+ after loss of two and one
counteranion(s) (OTf−), respectively (Fig. S37, ESI†). No mass
metal ions Cu+, Cu2+ and Zn2+
.
atoms (N1 and N1′) remain unbound. In iso-II, Cu+ is bound
to N2, N3, N2′, N1′ whereas N1, N3′ are left uncoordinated. In
contrast, iso-III deals with coordination at N2, N1, N2′, N1′
with nitrogens N3, N3′ remaining nonbonded. The unbound
pyridyl unit (N1 or N1′) of 5 may undergo rotation about the
single C–C bond thereby generating various conformations in
iso-I and iso-II of [Cu(5)2]+. For instance, iso-I may have three
major conformers – iso-IA (out–out = N1 and N1′ directed away
from Cu+ center), iso-IB (out–in), and iso-IC (in–in). Similarly
iso-II may have two conformers – iso-IIA (in) and iso-IIB (out).
Obviously, in iso-III both pyridyl units are conformationally
fixed as they are involved in bonding with Cu+. DFT15 compu-
tations suggest that iso-IB has lowest energy. The relative
energy of the isomers follows the order: iso-IB (0) < iso-IA (3.94)
1
peaks of homoleptic complexes are visible. The H NMR spec-
trum displays two diagnostic signals at 5.64 & 5.69 ppm for the
heteroleptic species (Fig. 2).
Due to the similarity in its coordination behaviour to that
of Zn2+, Cu2+ also afforded cleanly the heteroleptic complex
[Cu(4)(5)]2+, as evidenced by ESI-MS and CV. The DFT opti-
mised structure of [Cu(4)(5)]2+ suggests that ligand 5 is tilted
toward the phenanthroline unit in a square pyramidal rather
than trigonal bipyramidal geometry presumably due to the
strong pyridyl→Cu binding (Cu⋯N1 = 2.27 Å). The latter inter-
action draws the two mesityl groups of 5 toward each other
and leaves little space for ligand 4. Upon irreversible reduction
of the freshly prepared [Cu(4)(5)]2+ at Epc = 245 mV a follow-up
reaction occurs that is visible in the reverse anodic scan: the
broad waves at Epa = 538 & 720 mV may be assigned to the oxi-
dation of a mixture of homo- and heteroleptic complexes (alike
the complex mixture from 4, 5 and Cu+, vide supra).
< iso-IIB (4.04) < iso-IIA (6.62) kcal mol−1 16
.
Experimental information about the coordination mode in
[Cu(5)2]+ was obtained from cyclic voltammetry (CV). Complex
[Cu(5)2]+ exhibits
a high oxidation potential at E1/2 =
634 mVSCE (quasireversible: ΔEp = 164 mV, see ESI†) clearly
excluding the possibility of penta- or hexa-coordination. Most
9440 | Dalton Trans., 2014, 43, 9438–9447
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Cu
Fig. 4 Preparation of complex
1
phen
.
Fig. 3 Partial 1H NMR spectra of equimolar mixtures (a) of 3, 4, 5 and
Cu+ (CD2Cl2) and (b) of 3, 4, 5 and Zn2+ (CD2Cl2–CD3CN = 3 : 1).
Sevcik plots yield a linear dependence of the anodic peak
intensity ipa with the square root of the scan rate (ν1/2), thus
attesting a diffusion-limited electron-transfer process. This
study clearly indicates fast metal ligand reorganisation upon
changing the oxidation state of copper (Cu+ → Cu2+ → Cu+) or
changing from copper(I) to zinc(II) ions both resulting in a self-
sorting between heteroleptic complexes.
Self-sorting
To study self-sorting,17 a mixture of 3, 4, 5 and Cu+ (1 : 1 : 1 : 1)
was sonicated in CD2Cl2. Although six copper(I) complexes
may be expected, the ESI mass spectrum shows only two peaks
at 800.3 Da and 1051.0 Da suggesting the exclusive formation
of the complexes [Cu(3)(4)]+ and [Cu(5)2]+, respectively
(Fig. S36, ESI†). In full agreement, the 1H NMR spectrum
Self-sorting on scaffold 2
displays diagnostic peaks at 6.00 ppm for the heteroleptic To use the redox-triggered switching of the self-sorting process
complex [Cu(3)(4)]+ and at 5.62 & 6.19 ppm for the homoleptic for cargo shipping between two different stations, the new
complex [Cu(5)2]+ (Fig. 3). Two sharp singlets at 5.64 and
ligand 2 is used as a nanoscaffold. At the outset, 2, 4 and Cu+
5.69 ppm would have been diagnostic for [Cu(4)(5)]+, but those (1 : 2 : 2) were reacted in CD2Cl2 to afford the complex Cu1phen
=
signals are absent. NMR integration suggests that complexes [Cu2(2)(4)2](PF6)2, in which both PhenAr2 stations of 2 are
[Cu(3)(4)]+ and [Cu(5)2]+ are present in 89% : 11% along with
unused ligands 3, 4 and 5.
quantitatively occupied by [Cu(4)]+, while the TerpyAr2 stations
remain unloaded (Fig. 4). The complex was characterised by
1
1
When 3, 4, 5 and Zn(OTf)2 (1 : 1 : 1 : 1) were sonicated for 1H NMR, H–1H COSY and ESI-MS. H NMR (Fig. 5) reveals that
30 min in CD2Cl2–CD3CN (3 : 1), quantitative formation of the
protons 9-H are upfield shifted from 6.94 to 6.00 ppm while
heteroleptic complex [Zn(4)(5)]2+ was observed. The 1H NMR protons 15′-H remain unchanged at 6.97 ppm (as in compound 2).
spectrum shows singlets at 5.64 & 5.69 ppm that are diagnostic Other protons of the PhenAr2 stations also undergo major shifts
for the heteroleptic complex along with a CHMes signal at
due to formation of the heteroleptic complex while protons of the
6.94 ppm indicative for the ligand 3 (Fig. 3). The two peaks at TerpyAr2 units remain unchanged (see Table S3†). Formation
370.0 and 888.3 Da in the ESI mass spectrum correspond to of the complex is ascertained by a peak at 1565.1 Da in the ESI
the doubly charged [Zn(4)(5)]2+ and singly charged [Zn(4)(5)]-
mass spectrum (Fig. S40, ESI†) corresponding to the doubly
(OTf)+, respectively (Fig. S38, ESI†). Due to the analogous d10 charged species [Cu2(2)(4)2]2+ after loss of two counteranions
configuration of Zn2+ and Cu2+, similar self-sorting phenom- (PF6−). Finally, the 1H DOSY trace proves that assembly Cu1phen
ena are expected for both metal ions suggesting quantitative
complex formation of [Cu(4)(5)]2+ with 3 remaining untouched
in solution.
exists in solution as a single species (Fig. S50, ESI†).
When a 1 : 2 mixture of 2 and 4 was treated with 2 equiv. of
Cu
Cu(ClO4)2·6H2O, complex
1
terpy
= [Cu2(2)(4)2](ClO4)4 formed
The effect of changing the metal’s oxidation state on self-
quantitatively as derived from the ESI-MS data. They (Fig. S42,
sorting was studied by CV. In the anodic scan of an equimolar ESI†) show two peaks at 782.7 Da and 1076.8 Da corres-
mixture of 3, 4, 5 and Cu+, the irreversible peak at Epa
763 mV is assigned to the oxidation of [Cu(3)(4)]+. The oxi-
=
ponding to the quadruply-charged ([Cu2(2)(4)2]4+) and triply-
charged species ([Cu2(2)(4)2](ClO4)3+) after loss of four and
three-counter anions (ClO4−), respectively. Strong paramag-
dation wave of the homoleptic complex [Cu(5)2]+ (Epa
=
720 mV, vide supra) is hardly detectable due to its small netic broadening by Cu2+ prevented us from characterising the
complex by 1H NMR. However, expecting a similar coordi-
amount (11%, see NMR). In the reverse scan, the irreversible
reduction wave at Epc = 242 mV indicates that the complex nation behaviour of zinc(II) and copper(II) ions (vide supra for
must have undergone a major reorganisation. Apparently, both the model study), we reacted Zn2+ with 1 and 4 (2 : 1 : 2). As a
[Cu(3)(4)]2+ and [Cu(5)2]2+ undergo fast ligand shuffling in
Zn
result, complex
1
was afforded, in which the [Zn(4)]2+
terpy
solution to afford exclusively the heteroleptic complex [Cu(4)- units quantitatively occupy the TerpyAr2 stations with the
(5)]2+. After reduction of [Cu(4)(5)]2+, the anodic back scan PhenAr2 stations remaining unloaded. Diagnostically, the 1H
again shows the oxidation waves corresponding to complexes
NMR (see Fig. 5, Table S4†) showed protons 15′-H (TerpyAr2) to
[Cu(3)(4)]+ and [Cu(5)2]+ at Epa = 763 mV. No oxidation wave be shifted upfield to 5.69 ppm while protons 9-H of both
was observed corresponding to [Cu(4)(5)]+. In fact, both peaks PhenAr2 units remain unaltered at 6.91 ppm. A similar behaviour
did not show reversibility at any of chosen scan rates (from 50
was observed for other protons of the PhenAr2 and TerpyAr2
to 200 mV s−1) at this concentration (c = 0.65 mM). Randles– units. In the ESI mass spectrum (Fig. S41, ESI†), Zn1terpy exhibited
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 9438–9447 | 9441

View Article Online
Paper
Dalton Transactions
Cu
Similarly, when HETPHEN complex
1
phen
= [Cu2(2)(4)2]-
(PF6)2 is electrochemically oxidised at v = 500 mV s−1, the oxi-
dation wave is irreversible (Epa = 844 mV). The wave overlaps
with the first oxidation potential of the zinc(II) porphyrin (por/
por•+; Fig. 6, left). In the reverse reductive scan, an irreversible
peak is observed at Epc = 174 mV that is assigned to
the reduction of electrochemically produced Cu1terpy indicating
metal and ligand translocation from PhenAr2 to TerpyAr2
stations. A time delay of 5 s at the first switching potential
(E1 = 900 mV) increases the current of the Cu2+/Cu+ redox
couple (E1/2 = 269 mV) at the TerpyAr2 station. Hence, CV
studies clearly establish the reversible interconversion between
the two stable species Cu1phen and Cu1terpy through cargo trans-
port (Fig. 1).
Zn
Fig. 5 Partial 1H NMR spectra of (a) 2 (CD2Cl2), (b)
CD3CN = 3 : 1) and (c) Cu1phen (CD2Cl2).
1
(CD2Cl2–
terpy
The CV behaviour can be understood as an EC process.
Electron transfer is followed by fast translocation of both
metal ion and ligand between the two different stations. Simu-
lation of the mechanism by DigiSim® was possible using a
simplified scheme. Due to the fact that the rate constants for
both cargo transport processes are hidden in each individual
CV trace, one is able to even cross-check the data. Accordingly,
three peaks at 783.5 Da, 1094.4 Da and 1716.1 Da that are
assigned to quadruply-charged ([Zn2(2)(4)2]4+), triply-charged
([Zn2(2)(4)2](OTf)3+) and doubly-charged ([Zn2(2)(4)2](OTf)2
)
2+
species after loss of four, three and two counter anions (OTf−),
respectively. Finally, 1H DOSY suggests that
1
exists in
terpy
Zn
solution as a single species (Fig. S51, ESI†).
the best agreement for Cu2+
→ Cu2+
was K = 10
TerpyAr2
was K = 20 and
PhenAr2
PhenAr2
Electrochemical cargo shipping
and k = 10 s−1 and for Cu+
→ Cu+
TerpyAr2
Inspired by the reversible interconversion of two heteroleptic
k = 5 s−1 (Fig. S49, ESI†). Using the same rate constants, also
the redox-mediated shuttling between [Cu(3)(4)]+ + 5 and [Cu-
(4)(5)]2+ + 3 (Fig. S44†) was successfully simulated, lending
Cu
complexes via electrochemical means, both complexes
1
phen
Cu
and
1
terpy
were tested for cargo shipping between the two
different stations (PhenAr2 and TerpyAr2) on scaffold 2. In the
further credibility to the above values. Moreover, a concen-
Cu
CV, complex
1
= [Cu2(2)(4)2](ClO4)4 (scan rate = 100 mV
terpy
Cu
tration-dependent CV study of
1
indicated negligible
phen
s−1) exhibits an irreversible reduction wave at Epc = 246 mV
(Fig. 6, right) that is characteristic for a pentacoordinated
copper(II) complex (inverse HETTAP complex). On the reverse
scan, the oxidation of the reduced species displays an irrevers-
ible peak at Epa = 786 mV that is characteristic for oxidation of
a copper(I/II) HETPHEN complex (unfortunately, the peak is
merged with the first reversible oxidation peak of the zinc(II)
porphyrin unit with Epa = 830 mV and E1/2 = 790 mV). Shifting
the cathodic switching potential towards negative potential (by
ΔE1 = −100 mV) and thus increasing the time for rearrange-
ment increases the anodic current (ipa) at Epa = 786 mV (see
ESI†) clearly arguing for ligand translocation from the
TerpyAr2 to PhenAr2 stations upon reduction of Cu2+ to Cu+.
Anodic peak current (ipa) enhancement at Epa = 786 mV is also
observed when using a 5 s delay at the first switching potential
(E1 = −100 mV). Moreover, both peaks show hardly any revers-
ible behaviour in the scan rate range (50 to 1000 mV s−1).
effects on the reversibility at E1/2 = 263 mV (Fig. S48, ESI†),
suggesting that dissociation is rate-limiting. A plausible mech-
anism for shipping is thus the rate-determining release of the
labilised metal ions (after oxidation/reduction) on the sub-
second time scale along with their phenanthroline cargo from
a particular station followed by fast reassociation at the other
station (a bimolecular process), which can be either intra- or
intersupramolecular.
Conclusion
In conclusion, we have shown that two heteroleptic complexes
can be interconverted by changing the oxidation state of the
copper ions. Using this redox-triggered self-sorting, cargo
(ligand 4 and copper) may be shipped reversibly between two
different stations (PhenAr2 and TerpyAr2) on platform 2. If the
redox state at copper is +I, ligand 4 occupies quantitatively the
PhenAr2 stations, whereas for copper(II), the TerpyAr2 stations
are engaged with the cargo molecules. Electrochemical oxi-
dation and reduction leads to reversible shipping of the cargo
between the two different stations. Concentration-dependent
CV studies advocate that dissociation of the cargo from the
scaffold is the rate determining step.
Experimental procedure
Cu
(scan rate = 500 mV s−1
)
phen
Commercial reagents were used without further purification.
Solvents were dried with appropriate desiccants and distilled
Fig. 6 Cyclic voltammogram of (left)
1
and (right) Cu1terpy (scan rate = 100 mV s−1) in dry CH2Cl2.
9442 | Dalton Trans., 2014, 43, 9438–9447
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
prior to use. 1H and 13C NMR spectra were recorded at (2.65 g, 30.5 mmol). After stirring for 12 h at room tempera-
400 MHz or 600 MHz using a deuterated solvent as the lock ture, the solution was filtered through a pad of celite. The
and residual protiated solvent as internal reference. The fol- solvent was evaporated to dryness. Finally, the compound was
lowing abbreviations are utilised to describe NMR peak pat- purified by column chromatography (SiO2, hexane–ethyl
terns: s = singlet, d = doublet, t = triplet, dd = doublet of acetate = 9 : 1, Rf = 0.4). Yield: 54%, mp: 236 °C. 1H NMR
doublets. The following abbreviations are used to describe (CD2Cl2, 400 MHz): δ = 2.10 (s, 6 H, CH3), 2.26 (s, 6 H, CH3),
peak patterns of IR spectra: s = sharp, m = medium, w = weak. 2.35 (s, 3 H, CH3), 2.40 (s, 3 H, CH3), 6.98 (s, 2 H, [15 or 15′]-
The numbering of the carbon skeleton in molecular formulae H), 7.04 (s, 2 H, [15′ or 15]-H), 7.25 (dd, 3J = 7.4 Hz, 4J = 1.0 Hz,
as shown in the manuscript does not comply with the IUPAC 1 H, 14-H), 7.62 (d, 3J = 8.4 Hz, 1 H, 4′-H), 7.84 (s, 2 H, 5′-,
3
3
nomenclature rules; it is only used for assignments of NMR 6′-H), 7.92 (t, J = 7.4 Hz, 1 H, 13-H), 8.29 (d, J = 8.4 Hz, 1 H,
3
3
signals. Electrospray ionisation (ESI) mass spectra were 3′-H), 8.31 (d, J = 8.4 Hz, 1 H, 8′-H), 8.78 (d, J = 8.4 Hz, 1 H,
recorded on a Thermo-Quest LCQ deca. Melting points were 7′-H), 8.81 (dd, J = 7.4 Hz, 4J = 1.0 Hz, 1 H, 12-H) ppm. 13C
3
measured on a Büchi SMP-20 and are uncorrected. Infrared NMR (CD2Cl2, 100 MHz): δ = 19.6, 20.7, 20.9, 21.7, 118.4,
spectra were recorded on a Varian 1000 FT-IR instrument. 118.8, 118.9, 127.6, 130.5, 130.8, 130.9, 131.1, 131.2, 131.7,
Elemental analysis measurements were made using the EA 132.4, 132.7, 134.8, 135.6, 136.0, 136.5, 137.4, 138.9, 139.2,
3000 CHNS. Cyclic voltammetry (CV) was measured on a 142.5, 149.4, 149.7, 149.9, 160.2, 160.8 ppm. IR (KBr): ˜ν = 3001,
Parstat 2273. CV of millimolar solutions was carried out in dry 2943, 2913, 1583, 1541, 1477, 1374, 1355, 1158, 1134, 909, 862,
CH2Cl2 (2.0 mL) with 0.1 M n-Bu4NPF6 as electrolyte against a 847, 752, 637, 629 cm−1. ESI-MS: m/z (%) 494.4 (100) [M + H]+.
Ag wire as a quasi-reference electrode and triphenylpyrylium Anal Calcd for C35H31N3·0.2H2O: C, 84.54; H, 6.36; N, 8.45.
tetrafluoroborate (TPP) as internal standard. All CV spectra are Found: C, 84.46; H, 6.15; N, 8.82.
calibrated against the standard calomel electrode (SCE).
2-(2,4,6-Trimethylphenyl)-6-bromopyridine (6)
2-(6-(2,4,6-Trimethylphenyl)pyrid-2-yl)-[1,10]-
phenanthroline (7)
2,6-Dibromopyridine (2.16 g, 9.12 mmol), 2,4,6-trimethyl-
phenylboronic acid (1.60 g, 6.10 mmol) and Pd(PPh3)4 (70.0 mg,
60.6 µmol) were dissolved in a degassed solution of MeOH Under N2 atmosphere, 2.5 M n-BuLi (1.45 mL, 3.62 mmol) in
(40 mL), THF (100 mL) and aqueous K2CO3 (2 M, 30 mL), then hexane was added dropwise to a solution of 6 (1.00 g,
the solution was refluxed for 12 h at 90 °C. The solvent was 3.62 mmol) in dry diethyl ether (80 mL) at −78 °C over a
evaporated and the residue redissolved in DCM. The organic period of 15 min. The reaction mixture was stirred at −40 °C
phase was washed with water thrice and then dried over anhy- for 2 h, then [1,10]-phenanthroline (489 mg, 2.72 mmol) was
drous Na2SO4. The product was further purified by column added under N2 atmosphere. The solution turning immedi-
chromatography (SiO2, hexane–EtOAc = 9 : 1, Rf = 0.3) to afford ately to a dark violet was stirred for another 12 h at room temp-
a liquid. Yield: 90%, 1H NMR (CDCl3, 400 MHz): δ = 2.04 (s, erature. Saturated aqueous NH4Cl (100 mL) was then added
6 H, CH3), 2.31 (s, 3 H, CH3), 6.92 (s, 2 H, 15′-H), 7.18 (dd, 3J = and the reaction slurry was stirred for 1 h. Thereafter, the solu-
7.8 Hz, 4J = 0.8 Hz, 1 H, 14-H), 7.45 (dd, 3J = 7.8 Hz, 4J = 0.8 Hz, tion was extracted with DCM (3 × 100 mL). After drying over
1 H, 12-H), 7.61 (t, 3J = 7.8 Hz, 1 H, 13-H) ppm. 13C NMR anhydrous Na2SO4, the solvent was removed. The solid orange
(CDCl3, 100 MHz): δ = 20.1, 21.0, 123.7, 125.9, 128.3, 135.6, residue was dissolved in DCM (100 mL) and treated with MnO2
136.2, 137.9, 138.5, 141.7, 161.1 ppm. IR (KBr): ˜ν = 3944, 3690, (3.15 g, 36.2 mmol). After stirring for 12 h at room tempera-
3055, 2986, 2306, 1571, 1425, 1265, 741 cm−1. ESI-Ms: m/z (%) ture, the solution was filtered through a pad of celite. The
277.1 (100) [M + H]+. Anal Calcd for C14H14BrN·0.2H2O: solvent was evaporated to dryness. Finally, the compound was
C, 60.10; H, 5.19; N, 5.01. Found: C, 60.06; H, 5.17; N, 5.20.
purified by column chromatography (SiO2, DCM–ethyl acetate
= 1 : 3, Rf = 0.25). Yield: 61%, mp: 165 °C. 1H NMR (CD2Cl2,
400 MHz): δ = 2.01 (s, 6 H, CH3), 2.34 (s, 3 H, CH3), 6.91 (s,
2-(6-(2,4,6-Trimethylphenyl)pyrid-2-yl)-9-(2,4,6-
trimethylphenyl)-[1,10]-phenanthroline (5)
3
4
2 H, 15-H), 7.23 (dd, J = 7.6 Hz, J = 1.2 Hz, 1 H, 14-H), 7.55
To a solution of 6 (841 mg, 3.05 mmol) in dry diethyl ether (d, 3J = 8.0 Hz, 1 H, 8′-H), 7.63 (dd, 3J = 8.0 Hz, 3J = 4.4 Hz, 1 H,
(80 mL), 2.5 M n-BuLi (1.22 mL, 3.05 mmol) in hexane was 3′-H), 7.82 (d, J = 8.8 Hz, 1 H, [5′ or 6′]-H), 7.86 (d, 3J = 8.8 Hz,
3
3
3
added dropwise at −78 °C under N2 atmosphere over a period 1 H, [6′ or 5′]-H), 7.94 (t, J = 7.6 Hz, 1 H, 13-H), 8.28 (d, J =
3
4
of 15 min. The reaction mixture was stirred at −40 °C for 2 h, 8.0 Hz, 2 H, 4′-, 7′-H), 8.83 (dd, J = 7.6 Hz, J = 1.2 Hz, 1 H,
then 2-(2,4,6-trimethylphenyl)-[1,10]-phenanthroline (605 mg, 12-H), 9.21 (dd, 3J = 4.4 Hz, 3J = 1.6 Hz, 1 H, 2′-H) ppm. 13C NMR
2.03 mmol) was added under N2 atmosphere. The solution (CD2Cl2, 100 MHz): δ = 19.6, 20.7, 124.8, 125.0, 127.6, 128.5,
turned immediately dark violet. After stirring for another 12 h 130.5, 130.8, 130.9, 131.7, 132.6, 135.6, 135.9, 136.0, 136.0,
at room temperature, saturated aqueous NH4Cl (100 mL) was 137.4, 137.6, 138.0, 141.4, 146.1, 146.1, 160.3, 160.9 ppm. IR
added. The reaction slurry was stirred for 1 h, then the solu- (KBr): ˜ν = 2967, 2923, 1583, 1521, 1447, 1374, 1365, 1158, 1134,
tion was extracted with DCM (3 × 100 mL). After drying over 919, 856 cm−1. ESI-MS: m/z (%) 376.4 (100) [M + H]+. Anal
anhydrous Na2SO4, the solvent was removed. The solid orange Calcd for C26H21N3·CH2Cl2: C, 70.44; H, 5.04; N, 9.13. Found:
residue was dissolved in DCM (100 mL) and treated with MnO2 C, 70.67; H, 5.15; N, 8.82.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 9438–9447 | 9443

View Article Online
Paper
Dalton Transactions
2-(6-(2,4,6-Trimethylphenyl)pyrid-2-yl)-9-(4-iodo-2,3,5,6-
tetramethylphenyl)-[1,10]-phenanthroline (8)
3J = 4.8 Hz, 4 H, β-H) ppm. 13C NMR (100 MHz, CD2Cl2): δ =
0.1, 19.6, 20.5, 21.0, 27.6, 93.9, 94.0, 95.4, 95.5, 105.0, 111.8,
119.9, 120.6, 122.4, 124.8, 125.0, 126.1, 126.4, 127.2, 127.2,
128.4 (2C), 130.2, 131.9, 132.0, 132.0, 132.6, 134.2, 135.7,
135.8, 136.0, 136.0, 137.5, 137.6, 141.4, 142.1, 142.8, 146.0,
149.8, 149.9, 149.9, 160.2, 160.8 ppm. IR (KBr): ˜ν = 2947, 2928,
2815, 2320, 2343, 1609, 1556, 1490, 1416, 1380, 1356, 1185,
1099, 1025, 998, 884 cm−1. ESI-MS: m/z (%) 1774.5 (100) [M +
H]+. Anal Calcd for C120H100N8Si2Zn·2H2O: C, 79.55; H, 5.79;
N, 6.18. Found: C, 79.92; H, 6.19; N, 6.22.
Over a period of 15 min, 2.5 M n-BuLi (0.800 mL, 2.00 mmol)
in hexane was added dropwise at −78 °C under N2 atmosphere
to a solution of 1,4-diiodo-2,3,5,6-tetramethylbenzene (770 mg,
2.00 mmol) in dry diethyl ether (80 mL). The reaction mixture
was stirred at −40 °C for 2 h, then 7 (500 mg, 1.33 mmol) was
added under N2 atmosphere. The solution turning immedi-
ately to dark violet was stirred for another 12 h at room temp-
erature. Saturated aqueous NH4Cl (100 mL) was then added
and the reaction slurry was stirred for 1 h. Thereafter, the solu-
tion was extracted with DCM (3 × 100 mL). After drying over
anhydrous Na2SO4, the solvent was removed. The solid orange
residue, redissolved in DCM (100 mL), was treated with MnO2
(1.72 g, 20.0 mmol) for 12 h at room temperature. After
passing the solution through a pad of celite, the solvent was
removed. Finally, the compound was purified by column
chromatography (SiO2, DCM–ethyl acetate = 70 : 30, Rf = 0.4).
Zinc(II) porphyrin 11
KOH (96.0 mg, 1.71 mmol) was added to a solution of zinc(II)
porphyrin 10 (310 mg, 0.175 mmol) in THF (30 mL). Then,
MeOH (15 mL) and H2O (5 mL) were added, and the reaction
mixture was stirred for 12 h at room temperature. After evapor-
ating the solvent, the residue was redissolved in DCM and
washed with water (3 × 100 mL). After drying over anhydrous
Na2SO4, DCM was evaporated and the compound was used
without further purification. Yield: 90%, mp: >300 °C. 1H
NMR (400 MHz, CD2Cl2): δ = 2.04 (s, 12 H, CH3), 2.14 (s, 12 H,
CH3), 2.33 (s, 6 H, CH3), 2.53 (s, 12 H, CH3), 3.61 (s, 2 H,
ethynyl-H), 6.92 (s, 4 H, 9-H), 7.54 (d, 3J = 8.4 Hz, 2 H, 7-H),
1
Yield: 53%, mp: >213 °C. H NMR (CD2Cl2, 400 MHz): δ = 2.09
(s, 6 H, CH3), 2.24 (s, 6 H, CH3), 2.33 (s, 6 H, CH3), 2.40 (s, 3 H,
CH3), 6.97 (s, 2 H, 15′-H), 7.28 (dd, 3J = 7.6 Hz, 4J = 0.8 Hz, 1 H,
14-H), 7.60 (d, 3J = 8.4 Hz, 1 H, 4′-H), 7.87 (s, 2 H, 5′-, 6′-H),
3
3
7.94 (t, J = 7.6 Hz, 1 H, 13-H), 8.34 (d, J = 8.4 Hz, 1 H, 3′-H),
3
3
3
3
7.58 (d, J = 8.4 Hz, 2 H, 4-H), 7.86 (d, J = 8.4 Hz, 4 H, 11-H),
8.35 (d, J = 8.4 Hz, 1 H, 8′-H), 8.75 (d, J = 8.4 Hz, 1 H, 7′-H),
8.77 (dd, 3J = 7.6 Hz, 4J = 0.8 Hz, 1 H, 12-H) ppm. 13C NMR
(CD2Cl2, 100 MHz): δ = 19.3, 20.7, 21.6, 21.9, 118.6, 124.6,
124.9, 127.6, 129.7, 130.5, 130.8, 130.9, 132.4, 132.9, 134.5,
135.1, 135.9, 136.2, 136.9, 137.4, 137.6, 138.5, 141.3, 142.3,
143.5, 146.1, 146.1, 160.3, 160.9 ppm. IR (KBr): ˜ν = 2956, 2916,
3
7.90 (s, 4 H, 5-, 6-H), 7.98 (d, J = 8.4 Hz, 4 H, 17-H), 8.11 (d,
3J = 8.4 Hz, 4 H, 10-H), 8.19 (d, J = 8.4 Hz, 4 H, 16-H), 8.37 (d,
3
3J = 8.4 Hz, 2 H, 8-H), 8.56 (d, J = 8.4 Hz, 2 H, 3-H), 8.90 (d,
3
3J = 4.0 Hz, 4 H, β-H), 8.95 (d, J = 4.8 Hz, 4 H, β-H) ppm. 13C
3
NMR (100 MHz, CD2Cl2): δ = 19.4, 20.7, 21.6, 27.4, 93.1, 94.0,
95.1, 95.6, 105.3, 111.1, 119.9, 120.6, 122.4, 124.8, 125.2, 126.7,
126.8, 127.2, 127.3, 128.6, 128.7, 130.5, 131.8, 132.1, 132.3,
132.6, 134.6, 135.8, 135.9, 136.2, 136.3, 137.6, 137.8, 141.4,
142.5, 142.8, 146.1, 149.8, 149.9, 150.1, 160.2, 160.8 ppm. IR
(KBr): ˜ν = 2998, 2935, 2820, 2345, 2323, 1619, 1565, 1490, 1397,
1353, 1189, 1050, 1025, 945, 895 cm−1. ESI-MS: m/z (%) 1630.3
(100) [M + H]+. Anal Calcd for C116H96N8Zn2: C, 80.48; H, 5.05;
1565, 1521, 1454, 1354, 1324, 1158, 1126, 919, 887 cm−1
.
ESI-MS: m/z (%) 637.4 (100) [M + H]+. Anal Calcd for
C36H32IN3·CH3CO2C2H5: C, 62.62; H, 6.76; N, 3.91. Found: C,
62.46; H, 6.45; N, 3.82.
Zinc(II) porphyrin 10
Zinc(II)-5,15-bis(4-iodophenyl)-10,20-bis(4-trimethylsilylethynyl- N, 6.53. Found: C, 80.67; H, 5.29; N, 6.32.
phenyl)porphyrin (250 mg, 223 μmol) and phenanthroline 9
(203 mg, 446 µmol) were placed in a round-bottomed flask.
Zinc(II) porphyrin 2
Then, Pd(PPh3)4 (25.7 mg, 22.3 μmol), dry NEt3 (10 mL) and Zinc(II) porphyrin 11 (110 mg, 67.4 μmol) and phenanthroline
dry DMF (30 mL) were added under N2 atmosphere. The reac- 8 (85.5 mg, 135 µmol) were put into a round-bottomed flask.
tion mixture was allowed to stir at 90 °C for 12 h. Then, it was Then, Pd(PPh3)4 (15.6 mg, 13.5 μmol), dry NEt3 (10 mL) and
evaporated to dryness, dissolved in DCM (50 mL), and washed dry DMF (30 mL) were added to the reaction mixture under N2
with water (3 × 50 mL). After drying over anhydrous Na2SO4, atmosphere. The reaction mixture was allowed to stir at 90 °C
the solvent was evaporated and the residue was purified by for 12 h. The reaction mixture was evaporated to dryness, dis-
column chromatography (SiO2, hexane–EtOAc = 80 : 20, Rf = solved in DCM (50 mL), and washed with water (3 × 50 mL).
0.4). The compound was further purified by size exclusion After drying over anhydrous Na2SO4, the solvent was evapor-
chromatography over biobeads SX-3 isolating the first moving ated and the residue was purified by column chromatography
1
band in toluene. Yield: 58%, mp: >300 °C. H NMR (400 MHz, (SiO2, DCM–MeOH = 99 : 1, Rf = 0.1). The compound was
CD2Cl2): δ = 0.38 (s, 18 H, TMS-H), 2.04 (s, 12 H, CH3), 2.12 (s, further purified by size exclusion chromatography over bio-
12 H, CH3), 2.31 (s, 6 H, CH3), 2.54 (s, 12 H, CH3), 6.92 (s, 4 H, beads SX-3 isolating the first moving band in toluene. Yield:
3
3
1
9-H), 7.52 (d, J = 8.4 Hz, 2 H, 7-H), 7.59 (d, J = 8.4 Hz, 2 H, 35%, mp: >300 °C. H NMR (400 MHz, CD2Cl2): δ = 2.00 (s, 12
3
4-H), 7.87 (d, J = 8.4 Hz, 4 H, 11-H), 7.88 (s, 4 H, 5-,6-H), 7.93 H, CH3), 2.03 (s, 12 H, CH3), 2.09 (s, 12 H, CH3), 2.16 (s, 12 H,
3
3
(d, J = 8.4 Hz, 4 H, 17-H), 8.10 (d, J = 8.4 Hz, 4 H, 10-H), 8.15 CH3), 2.33 (s, 6 H, CH3), 2.35 (s, 6 H, CH3), 2.41 (s, 12 H, CH3),
3
3
(d, J = 8.4 Hz, 4 H, 16-H), 8.36 (d, J = 8.4 Hz, 2 H, 8-H), 8.54 2.60 (s, 12 H, CH3), 6.95 (s, 4 H, 9-H), 6.98 (s, 4 H, 15′-H), 7.28
(d, 3J = 8.4 Hz, 2 H, 3-H), 8.92 (d, 3J = 4.0 Hz, 4 H, β-H), 8.94 (d, (dd, J = 7.6 Hz, J = 0.8 Hz, 2 H, 14-H), 7.52 (d, J = 8.0 Hz,
3
4
3
9444 | Dalton Trans., 2014, 43, 9438–9447
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
3
2 H, [4 or 7]-H), 7.56 (d, J = 8.0 Hz, 2 H, [7 or 4]-H), 7.60 (d, 1.6 Hz, 2 H, 4″-H), 8.54 (d, 3J = 8.4 Hz, 1 H, 3′-H), 8.60 (dd, 3J =
3
3J = 8.4 Hz, 2 H, 4′-H), 7.86 (d, J = 8.4 Hz, 4 H, [17 or 16]-H), 8.4 Hz, 4J = 1.6 Hz, 2 H, 2″-H), 8.66 (dd, 3J = 7.6 Hz, 4J = 1.2 Hz,
3
3
7.87 (s, 4 H, 5′-, 6′-H), 7.90 (s, 4 H, 5-, 6-H), 7.95 (d, 3J = 8.4 Hz, 1 H, 12-H), 8.97 (d, J = 8.6 Hz, 1 H, 8′-H), 9.08 (d, J = 8.6 Hz,
4 H, [11 or 10]-H), 7.94 (t, J = 7.6 Hz, 2 H, 13-H), 8.12 (d, J = 1 H, 7′-H) ppm. 13C NMR (CD2Cl2–CD3CN = 3 : 1, 100 MHz): δ =
8.4 Hz, 4 H, [10 or 11]-H), 8.16 (d, J = 8.4 Hz, 4 H, [16 or 17]- 19.2, 19.3, 20.2, 20.3, 121.9, 122.7, 126.5, 128.0 (2C), 128.1
H), 8.33 (d, J = 8.0 Hz, 2 H, [3 or 8]-H), 8.34 (d, J = 8.0 Hz, (2C), 128.3, 128.6, 128.9, 129.4, 130.0, 130.0, 134.0, 134.2,
2 H, [8 or 3]-H), 8.34 (d, 3J = 8.4 Hz, 2 H, 3′-H), 8.36 (d, 3J = 134.8, 135.6, 135.9, 139.1, 139.2, 140.3, 140.3, 141.3, 141.4,
8.4 Hz, 2 H, 8′-H), 8.76 (d, J = 8.4 Hz, 2 H, 7′-H), 8.77 (dd, J = 142.5, 149.4, 149.6, 151.1, 151.2, 161.2, 161.6 ppm. IR (KBr):
7.6 Hz, J = 0.8 Hz, 2 H, 12-H), 8.95 (d, J = 4.4 Hz, 4 H, β-H), ˜ν = 3001, 2943, 2913, 1583, 1541, 1477, 1374, 1355, 1158, 1134,
8.96 (d, 3J = 4.4 Hz, 4 H, β-H) ppm. 13C NMR (100 MHz, 909, 862, 847, 752, 637, 629 cm−1. ESI-MS: m/z (%) 370.0
CD2Cl2): δ = 20.0, 20.1, 20.6, 20.8, 21.5, 21.6, 28.0, 28.1, 94.4, (100) [Zn(4)(5)]2+, 888.3 (30) [Zn(4)(5)]+. Anal. Calcd for
94.6, 97.2, 97.4, 112.5, 112.7, 120.2, 120.3, 120.9, 121.0, 122.7, C49H39F6N5O6S2Zn: C, 56.73; 3.79; N, 6.75; S, 6.18. Found: C,
123.4, 124.0, 124.4, 124.9, 125.2, 126.3, 126.6, 126.9 (2C), 56.47; 3.99; N, 6.58; S, 6.43.
3
3
3
3
3
3
3
4
3
127.0, 127.5, 127.6, 127.6, 128.8 (2C), 129.1, 129.2, 130.7,
132.4, 133.1 (2C), 134.7, 136.1, 136.2, 136.4, 136.4, 136.5,
Heteroleptic complex [Cu(4)(5)](ClO4)2
136.6, 136.8, 138.0, 138.3, 138.4, 138.6, 138.6, 139.1 (2C), Compound 5 (3.45 mg, 6.99 µmol), Cu(ClO4)2·6H2O (2.59 mg,
141.5, 141.9, 141.9, 142.3, 142.3, 143.0, 146.4, 146.4, 146.6, 6.99 µmol) and 4 (1.26 mg, 6.99 µmol) were dissolved in
150.1, 150.1, 150.2, 150.6, 160.3, 160.9, 160.9 ppm. IR (KBr): CD2Cl2–CD3CN = 3 : 1 furnishing the desired complex as
˜ν = 2936, 2916, 2836, 2380, 2343, 1619, 1556, 1490, 1425, 1356, characterised by ESI-MS: m/z (%) 368.7 (100) [Cu(4)(5)]2+, 836.8
1326, 1165, 1099 cm−1
.
ESI-MS: m/z (%) 1322.3 (100) (30) [Cu(4)(5)](ClO4)+.
[M + 2H]2+, 881.9 (50) [M + 3H]3+, 661.7 (30) [M + 4H]4+. Anal.
Calcd for C186H146N14Zn·1.5CH2Cl2: C, 81.30; H, 5.42; N, 7.08.
Found: C, 81.45; H, 5.19; N, 7.22.
Complex Cu1phen = [Cu2(2)(4)2]2+
In an NMR tube, platform 2 (2.42 mg, 0.916 µmol), [Cu-
(CH3CN)4]PF6 (0.683 mg, 1.83 µmol) and ligand 4 (0.330 mg,
1.83 µmol) were dissolved in CD2Cl2 affording complex Cu1phen
Homoleptic complex [Cu(5)2](PF6)
In an NMR tube, ligand 5 (0.373 mg, 0.756 µmol) and in quantitative yield. Mp: >300 °C. 1H NMR (CD2Cl2,
[Cu(CH3CN)4]PF6 (0.141 mg, 0.378 µmol) were dissolved in 400 MHz): δ = 1.53 (s, 6 H, CH3), 1.65 (s, 12 H, CH3), 1.66 (s, 12
CD2Cl2 to afford the desired complex in quantitative yield. mp: H, CH3), 1.78 (s, 12 H, CH3), 2.12 (s, 12 H, CH3), 2.28 (s, 12 H,
1
>300 °C. H NMR (CD2Cl2, 400 MHz): δ = 0.70 (s, 6 H, CH3), CH3), 2.30 (s, 6 H, CH3), 2.59 (s, 12 H, CH3), 6.00 (s, 4 H, 9-H),
0.79 (s, 6 H, CH3), 1.97 (s, 12 H, CH3), 2.00 (s, 6 H, CH3), 2.24 6.97 (s, 4 H, 15′-H), 7.27 (dd, 3J = 7.6 Hz, 4J = 1.2 Hz, 2 H,
3
3
3
(s, 6 H, CH3), 5.61 (s, 4 H, [15 or 15′]-H), 6.19 (s, 4 H, [15′ or 14-H), 7.60 (d, J = 8.4 Hz, 2 H, 4′-H), 7.71 (dd, J = 8.2 Hz, J =
15]-H), 6.97 (dd, 3J = 7.6 Hz, 3J = 1.2 Hz, 2 H, 14-H), 7.40 (d, 3J = 8.2 Hz, 4 H, 3″-H), 7.83 (d, 3J = 8.4 Hz, 2 H, [4 or 7]-H), 7.86 (d,
8.0 Hz, 2 H, 4′-H), 7.47 (t, J = 7.6 Hz, 2 H, 13-H), 8.06 (s, 4 H, 3J = 8.0 Hz, 4 H, [10 or 11]-H), 7.89 (d, 3J = 8.4 Hz, 2 H, [7 or 4]-
3
3
3
5′-, 6′-H), 8.44 (d, J = 8.0 Hz, 2 H, 3′-H), 8.49 (d, J = 8.6 Hz, H), 7.91 (s, 4 H, 5′-, 6′-H), 7.92 (s, 4 H, 5″-H), 7.94 (t, 3J =
3
3
3
2 H, 8′-H), 8.58 (d, J = 8.6 Hz, 2 H, 7′-H), 9.41 (dd, J = 7.6 Hz, 7.6 Hz, 2 H, 13-H), 7.95 (d, J = 8.0 Hz, 4 H, [16 or 17]-H), 8.12
3J = 1.2 Hz, 2 H, 12-H) ppm. 13C NMR (CD2Cl2, 100 MHz): δ = (d, J = 8.0 Hz, 4 H, [17 or 16]-H), 8.16 (d, J = 8.0 Hz, 4 H, [11
3
3
3
19.6, 19.8, 20.3, 21.0, 21.0, 122.5, 124.7, 126.1, 126.6, 126.9, or 10]-H), 8.21 (s, 4 H, 5-, 6-H), 8.34 (d, J = 8.4 Hz, 2 H, 3′-H),
127.1, 127.2, 128.3, 128.4, 128.6, 130.1, 133.5, 135.6, 135.8, 8.36 (d, 3J = 8.0 Hz, 2 H, 8′-H), 8.42 (dd, 3J = 8.2 Hz, 4J = 1.6 Hz,
136.0, 137.2, 137.3, 137.6, 137.6, 137.8, 144.1, 145.1, 153.5, 4 H, 4″-H), 8.45 (dd, 3J = 8.2 Hz, 4J = 1.6 Hz, 4 H, 2″-H), 8.69 (d,
154.5, 159.7, 160.0 ppm. IR (KBr): ˜ν = 2965, 2903, 1613, 1585, 3J = 8.4 Hz, 2 H, [3 or 8]-H), 8.70 (d, J = 8.4 Hz, 2 H, [8 or 3]-
3
1454, 1402, 1339, 1138, 1104, 845, 810, 759 cm−1. ESI-MS: m/z H), 8.76 (d, J = 8.0 Hz, 2 H, 7′-H), 8.77 (dd, J = 7.6 Hz, J =
3
3
4
(%) 1051.0 (100) [Cu(5)2]+. Anal Calcd for C70H62CuF6N6P: C, 1.2 Hz, 2 H, 12-H), 8.94 (d, J = 4.0 Hz, 4 H, β-H), 8.95 (d, J =
3
3
70.31; H, 5.23; N, 7.03. Found: C, 70.36; H, 5.45; N, 7.15.
4.0 Hz, 4 H, β-H) ppm. 13C NMR (CD2Cl2, 100 MHz) δ = 19.5,
19.6, 20.2, 20.4, 20.4, 20.6, 21.2, 21.3, 94.1, 94.2, 95.7, 95.9,
105.3, 111.5, 120.3, 120.3, 120.4, 121.0, 122.8, 124.7, 124.8,
Heteroleptic complex [Zn(4)(5)](OTf)2
In an NMR tube, compound 5 (0.550 mg, 1.11 µmol), Zn(OTf)2 124.9, 125.1, 125.4, 126.3, 126.3, 126.4, 126.4, 126.6, 126.7,
(0.405 mg, 1.11 µmol) and 4 (0.201 mg, 1.11 µmol) were dis- 126.9, 127.0, 127.1, 127.3, 127.4, 128.2, 128.3, 128.6, 128.6,
solved in CD2Cl2–CD3CN
= 3 : 1 furnishing the desired 128.8, 129.0, 130.4, 131.5, 132.3, 134.8, 134.9, 135.0, 135.2,
1
complex in quantitative yield. mp: >300 °C. H NMR (CD2Cl2– 135.3, 136.1, 136.2, 136.3, 136.4, 136.5, 136.7, 137.0, 137.3,
CD3CN = 3 : 1, 400 MHz): δ = 0.93 (s, 6 H, CH3), 1.00 (s, 6 H, 137.7, 137.7, 137.8, 138.1, 142.6, 143.2, 143.4, 144.1, 147.8,
CH3), 1.82 (s, 3 H, CH3), 1.87 (s, 3 H, CH3), 5.64 (s, 2 H, [15 or 149.1, 150.2, 150.3, 150.3, 150.3, 151.1, 151.3, 156.6, 156.6,
3
4
15′]-H), 5.69 (s, 2 H, [15′ or 15]-H), 7.04 (dd, J = 7.6 Hz, J = 159.5, 159.6 ppm. IR (KBr): ˜ν = 2975, 2847, 2306, 2196, 1604,
1.2 Hz, 1 H, 14-H), 7.23 (d, 3J = 8.4 Hz, 1 H, 4′-H), 7.67 (dd, 3J = 1595, 1422, 1376, 1340, 1258, 1224, 1203, 1153, 1062, 1030,
3
3
8.4 Hz, J = 8.4 Hz, 2 H, 3″-H), 7.96 (s, 2 H, 5″-H), 8.13 (t, J = 850, 797 cm−1, ESI-MS: m/z (%) 1565.1 (100) [Cu2(2)(4)2]2+.
3
7.6 Hz, 1 H, 13-H), 8.20 (d, J = 8.8 Hz, 1 H, [5′ or 6′]-H), 8.27 Anal. Calcd for C210H162Cu2F12N18P2Zn: C, 73.75; H, 4.77;
(d, 3J = 8.8 Hz, 1 H, [6′ or 5′]-H), 8.52 (dd, 3J = 8.4 Hz, 4J = N, 7.37. Found: C, 73.49; H, 4.87; N, 7.52.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 9438–9447 | 9445

View Article Online
Paper
Dalton Transactions
Complex Zn1terpy = [Zn2(2)(4)2]4+
G. Woehlke, Nature, 2003, 422, 759; (c) M. A. Geeves and
K. C. Holmes, Annu. Rev. Biochem., 1999, 68, 687.
In an NMR tube, platform 2 (3.65 mg, 1.38 µmol), Zn(OTf)2
2 (a) S. J. Cantrill, A. R. Pease and J. F. Stoddart, J. Chem.
Soc., Dalton Trans., 2000, 3715; (b) T. Murahashi, K. Shirato,
A. Fukushima, K. Takase, T. Suenobu, S. Fukuzumi,
S. Ogoshi and H. Kurosawa, Nat. Chem., 2012, 4, 52;
(c) C. Wang, Z. Li, D. Cao, Y.-L. Zhao, J. W. Gaines,
O. A. Bozdemir, M. W. Ambrogio, M. Frasconi, Y. Y. Botros,
J. I. Zink and J. F. Stoddart, Angew. Chem., Int. Ed., 2012,
51, 5460.
3 (a) J.-P. Sauvage, Acc. Chem. Res., 1998, 31, 611;
(b) A. M. Brouwer, C. Frochot, F. G. Gatti, D. A. Leigh,
L. Mottier, F. Paolucci, S. Roffia and G. W. H. Wurpel,
Science, 2001, 291, 2124; (c) V. Amendola, L. Fabbrizzi,
C. Mangano and P. Pallavicini, Acc. Chem. Res., 2001, 34,
488; (d) Y. Liu, A. H. Flood, P. A. Bonvallet, S. A. Vignon,
B. H. Northrop, H.-R. Tseng, J. A. Jeppesen, T. J. Huang,
B. Brough, M. Baller, S. Magonov, S. D. Solares,
W. A. Goddard, C.-M. Ho and J. F. Stoddart, J. Am. Chem.
Soc., 2005, 127, 9745; (e) B. Colasson, N. L. Paul, Y. L. Mest
and O. Reinaud, J. Am. Chem. Soc., 2010, 132, 4393.
(1.00 mg, 2.76 µmol) and ligand 4 (0.498 mg, 2.76 µmol) were
Zn
dissolved in CD2Cl2–CD3CN = 3 : 1 furnishing complex
1
terpy
1
in quantitative yield. Mp: >300 °C. H NMR (CD2Cl2–CD3CN =
3 : 1, 400 MHz): δ = 0.94 (s, 12 H, CH3), 1.02 (s, 12 H, CH3),
1.83 (s, 6 H, CH3), 1.88 (s, 12 H, CH3), 1.94 (s, 12 H, CH3), 1.97
(s, 12 H, CH3), 2.28 (s, 6 H, CH3), 2.49 (s, 12 H, CH3), 5.69 (s,
4 H, 15′-H), 6.91 (s, 4 H, 9-H), 7.05 (dd, 3J = 7.6 Hz, 4J = 1.2 Hz,
3
3
2 H, 14-H), 7.24 (d, J = 8.4 Hz, 2 H, 4′-H), 7.48 (d, J = 8.0 Hz,
3
2 H, [4 or 7]-H), 7.53 (d, J = 8.0 Hz, 2 H, [7 or 4]-H), 7.68 (dd,
3J = 8.4 Hz, 3J = 8.4 Hz, 4 H, 3″-H), 7.79 (d, 3J = 8.0 Hz, 4 H, [16
3
or 17]-H), 7.89 (s, 4 H, 5, 6-H), 7.91 (d, J = 8.4 Hz, 4 H, [10 or
11]-H), 7.92 (s, 4 H, 5″-H), 8.06 (d, J = 8.4 Hz, 4 H, [11 or 10]-
3
3
3
H), 8.12 (d, J = 8.0 Hz, 4 H, [17 or 16]-H), 8.16 (t, J = 7.6 Hz,
3
3
2 H, 13-H), 8.19 (d, J = 8.8 Hz, 2 H, [5′ or 6′]-H), 8.27 (d, J =
3
8.8 Hz, 2 H, [6′ or 5′]-H), 8.33 (d, J = 8.0 Hz, 2 H, [3 or 8]-H),
3
3
8.35 (d, J = 8.0 Hz, 2 H, [8 or 3]-H), 8.51 (d, J = 8.4 Hz, 2 H,
3′-H), 8.53 (dd, 3J = 8.4 Hz, 4J = 1.6 Hz, 4 H, 4″-H), 8.62 (dd, 3J =
8.4 Hz, 4J = 1.6 Hz, 4 H, 2″-H), 8.69 (dd, 3J = 7.6 Hz, 4J = 1.2 Hz,
3
3
2 H, 12-H), 8.83 (d, J = 4.8 Hz, 4 H, β-H), 8.85 (d, J = 4.8 Hz,
4 H, β-H), 8.96 (d, 3J = 8.4 Hz, 1 H, 8′-H), 9.06 (d, 3J = 8.4 Hz, 1 H,
7′-H) ppm. 13C NMR (CD2Cl2–CD3CN = 3 : 1, 100 MHz) δ = 18.5,
18.6, 19.0, 19.8, 20.4, 20.4, 20.6, 27.2, 93.4, 93.6, 96.1, 96.2,
105.0, 111.0, 119.4, 120.0, 122.0, 122.1, 122.5, 124.3, 124.5,
125.9, 126.2, 126.4, 126.5, 127.0, 127.0, 127.1, 127.4, 127.8,
128.0, 128.2 (2C), 128.7, 128.9, 129.2, 129.6, 129.9, 130.2,
131.7, 132.5, 133.6, 133.9, 134.2, 134.5, 135.6 (2C), 136.2 (2C),
136.4, 137.4, 137.5, 137.5, 137.6, 138.2, 139.4, 139.8, 140.0,
140.7, 140.8, 141.1, 141.5, 141.7, 142.3, 142.7, 143.5, 146.1,
148.1, 148.7, 149.5, 149.6, 149.7, 150.5, 160.0, 160.7, 161.3,
161.7 ppm. IR (KBr): ˜ν = 2921, 2200, 1601, 1478, 1277, 1259,
1030, 996, 797, 638 cm−1. ESI-MS: m/z (%) 783.5 (50) [Zn2(2)-
4 V. Balzani, A. Credi and M. Venturi, Molecular Devices and
Machines, Wiley-VCH, Weinheim, 2nd edn, 2008;
B. L. Feringa and W. R. Browne, Molecular Switches 1+2,
Wiley-VCH, Weinheim, 2nd edn, 2011.
5 (a) J.-P. Collin, C. Dietrich-Buchecker, P. Gavina,
M. C. Jimenez-Molero and J.-P. Sauvage, Acc. Chem. Res.,
2001, 34, 477; (b) J. D. Badjic, C. M. Ronconi, J. F. Stoddart,
V. Balzani, S. Silvi and A. Credi, J. Am. Chem. Soc., 2006,
128, 1489; (c) T. Song and H. Liang, J. Am. Chem. Soc., 2012,
134, 10803; (d) B. Lewandowski, G. D. Bo, J. W. Ward,
M.
Papmeyer,
S.
Kuschel,
M.
J.
Aldegunde,
P. M. E. Gramlich, D. Heckmann, S. M. Goldup,
D. M. D’souza, A. E. Fernandes and D. A. Leigh, Science,
2013, 339, 189.
(4)2]4+, 1094.4 (100) [Zn2(2)(4)2](OTf)3+, 1716.1 (20) [Zn2(2)(4)2]-
2+
(OTf)2
. Anal Calcd for C214H162F12N18O12S4Zn3·CH2Cl2:
6 (a) R. T. Kelly, H. De Silva and R. A. Silva, Nature, 1999, 401,
150; (b) M. C. Jiménez, C. Dietrich-Buchecker and
J.-P. Sauvage, Angew. Chem., Int. Ed., 2000, 39, 3284;
(c) M. Haga, T. Takasugi, A. Tomie, M. Ishizuya, T. Yamada,
M. D. Hossain and M. Inoue, Dalton Trans., 2003, 2069;
(d) M. Alvarez-Pérez, S. M. Goldup, D. A. Leigh and
A. M. Z. Slawin, J. Am. Chem. Soc., 2008, 130, 1836;
(e) G. Haberhauer, Angew. Chem., Int. Ed., 2010, 49, 9286;
(f) S. K. Samanta and M. Schmittel, J. Am. Chem. Soc., 2013,
135, 18794.
C, 67.69; H, 4.33; N, 6.61; S, 3.36. Found: C, 67.56; H, 4.18; N,
6.47; S, 3.56.
Complex Cu1terpy = [Cu2(2)(4)2](ClO4)4
Compound 2 (3.78 mg, 1.43 µmol), Cu(ClO4)2·6H2O (0.530 mg,
1.43 µmol) and 4 (0.258 mg, 1.43 µmol) were dissolved in
CD2Cl2–CD3CN = 3 : 1 furnishing the desired complex as
characterised by ESI-MS: m/z (%) 782.7 (100) [Cu2(2)(4)2]4+,
1076.8 (50) [Cu2(2)(4)2](ClO4)3+.
7 (a) N. Armaroli, V. Balzani, J.-P. Collin, P. Gaviña,
J.-P. Sauvage and B. Ventura, J. Am. Chem. Soc., 1999, 121,
4397; (b) A. Carella, C. Coudret, G. Guirado, G. Rapenne,
G. Vives and J.-P. Launay, Dalton Trans., 2007, 177;
(c) F. Durola and J.-P. Sauvage, Angew. Chem., Int. Ed., 2007,
46, 3537; (d) Y.-L. Zhao, W. R. Dichtel, A. Trabolsi, S. Saha,
I. Aprahamian and J. F. Stoddart, J. Am. Chem. Soc., 2008,
130, 11294; (e) L. Fang, C. Wang, A. C. Fahrenbach,
A. Trabolsi, Y. Y. Botros and J. F. Stoddart, Angew. Chem.,
Int. Ed., 2011, 50, 1805; (f) T. Avellini, H. Li, A. Coskun,
G. Barin, A. Trabolsi, A. N. Basuray, S. K. Dey, A. Credi,
Acknowledgements
We acknowledge generous funding by the DFG and the Univer-
sität Siegen.
Notes and references
1 (a) L. B. Jilaveanu, C. R. Zito and D. Oliver, Proc. Natl. Acad.
Sci. U. S. A., 2005, 102, 7511; (b) M. Schliwa and
9446 | Dalton Trans., 2014, 43, 9438–9447
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
S. Silvi, J. F. Stoddart and M. Venturi, Angew. Chem., Int. 12 (a) M. Schmittel and A. Ganz, Chem. Commun., 1997, 999;
Ed., 2012, 51, 1611; (g) M. Nishikawa, S. Kume and
H. Nishihara, Phys. Chem. Chem. Phys., 2013, 15, 10549.
8 (a) N. Koumura, R. W. J. Zijlstra, R. A. van Delden,
N. Harada and B. L. Feringa, Nature, 1999, 401, 152;
(b) T. Muraoka, K. Kinbara, Y. Kobayashi and T. Aida, J. Am.
Chem. Soc., 2003, 125, 5612; (c) T. Muraoka, K. Kinbara and
T. Aida, Nature, 2006, 440, 512; (d) S. Kume and
(b) M. Schmittel, U. Lüning, M. Meder, A. Ganz, C. Michel
and M. Herderich, Heterocycl. Commun., 1997, 3, 493;
(c) M. Schmittel, V. Kalsani, R. S. K. Kishore, H. Cölfen and
J. W. Bats, J. Am. Chem. Soc., 2005, 127, 11544;
(d) M. Schmittel and S. K. Samanta, J. Org. Chem., 2010, 75,
5911; (e) S. De, K. Mahata and M. Schmittel, Chem. Soc.
Rev., 2010, 39, 1555.
H. Nishihara, Dalton Trans., 2008, 3260; (e) A. Coskun, 13 (a) M. M. Safont-Sempere, G. Fernández and F. Würthner,
D. C. Friedman, H. Li, K. Patel, H. A. Khatib and
J. F. Stoddart, J. Am. Chem. Soc., 2009, 131, 2493;
(f) M. C. Basheer, Y. Oka, M. Mathews and N. Tamaoki,
Chem. – Eur. J., 2010, 16, 3489; (g) Z. Li, J. Liang, W. Xue,
Chem. Rev., 2011, 111, 5784; (b) K. Osowska and
O. Š. Miljanić, Synlett, 2011, 1643; (c) M. L. Saha and
M. Schmittel, Org. Biomol. Chem., 2012, 10, 4651;
(d) S. Saha and P. Ghosh, J. Chem. Sci., 2012, 124, 1229.
G. Liu, S. H. Liu and J. Yin, Supramol. Chem., 2014, 14 (a) K. Parimal, E. H. Witlicki and A. H. Flood, Angew.
26, 54.
Chem., Int. Ed., 2010, 49, 4628; (b) K. Osowska and
O. Š. Miljanić, J. Am. Chem. Soc., 2011, 133, 724;
(c) A.-M. Stadler, C. Burg, J. Ramírez and J.-M. Lehn, Chem.
Commun., 2013, 49, 5733.
9 (a) A. Livoreil, C. O. Dietrich-Buchecker and J.-P. Sauvage,
J. Am. Chem. Soc., 1994, 116, 9399; (b) J. P. Collin, F. Durola,
J. Lux and J.-P. Sauvage, Angew. Chem., Int. Ed., 2009, 48,
8532; (c) H. Li, A. C. Fahrenbach, A. Coskun, Z. Zhu, 15 (a) DFT computations were performed with the B3LYP
G. Barin, Y.-L. Zhao, Y. Y. Botros, J.-P. Sauvage and
J. F. Stoddart, Angew. Chem., Int. Ed., 2011, 50, 6782.
10 M. L. Saha, S. Neogi and M. Schmittel, Dalton Trans., 2014,
43, 3815.
functional, 6-31G* basis set for all main group elements
and LANL2DZ basis set for copper implemented in
Gaussian 09; (b) M. J. Frisch, et al., Gaussian 09, Revision B.01.
16 In parenthesis, the relative energies are given with respect
to the lowest energy structure. Structures iso-IC and iso-III
could not be optimised in DFT computations due to severe
steric crowding between the mesityl groups.
11 (a) H. Sleiman, P. Baxter, J.-M. Lehn and K. Rissanen,
J. Chem. Soc., Chem. Commun., 1995, 715; (b) J. Frey,
C. Tock, J.-P. Collin, V. Heitz, J.-P. Sauvage and K. Rissanen,
J. Am. Chem. Soc., 2008, 130, 11013; (c) S. Durot, 17 In another experiment when 3 and 5 were mixed with Cu+
F. Reviriego and J.-P. Sauvage, Dalton Trans., 2010, 39,
10557; (d) R. S. Forgan, J.-P. Sauvage and J. F. Stoddart,
Chem. Rev., 2011, 111, 5434.
or Zn2+ at a 1 : 1 : 1 ratio, there was no evidence for the for-
1
mation of the heteroleptic species neither by H NMR nor
ESI-MS.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 9438–9447 | 9447