Supramolecular effects on the potential of redox units - Nanoscaffolds internally functionalised with ferrocene units

Article abstract of DOI:10.1039/b703633g

Redox-active nanoscale racks and nanoladders were prepared as proof of principle in a directional heteroleptic approach towards internally functionalised aggregates. Using the HETTAP concept, zinc(ii) phenanthroline terpyridine nanoladder and nanorack str

Full text of DOI:10.1039/b703633g

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www.rsc.org/obc | Organic & Biomolecular Chemistry
Supramolecular effects on the potential of redox units—nanoscaffolds
internally functionalised with ferrocene units†
Michael Schmittel,*a Bice He,a Venkateshwarlu Kalsania and Jan W. Batsb
Received 9th March 2007, Accepted 4th June 2007
First published as an Advance Article on the web 26th June 2007
DOI: 10.1039/b703633g
Redox-active nanoscale racks and nanoladders were prepared as proof of principle in a directional
heteroleptic approach towards internally functionalised aggregates. Using the HETTAP concept,
zinc(II) phenanthroline terpyridine nanoladder and nanorack structures with internal ferrocene units
were prepared. Proximal effects exerted by the ferrocene units in the nanoladders could be read out by
comparison of their redox potentials with those of nanorack R1 and of the parent ligand. The
increasing compression of the ferrocene units when going from the larger nanoladder L1 to the smaller
aggregate L2 manifested itself in an enlarged anodic shift. Thus, the redox potential series (vs. DMFc:
E1/2 = 0.462 V for R1, 0.480 V for L1 and 0.491 V for L2) reveals convincingly the supramolecular
effect on a redox transition. At cathodic potentials the zinc(II) phenanthroline terpyridine complexes
were decomposed due to a reduction of the ligands, as could be detected from an evaluation of the
ferrocene redox potential.
motifs.13 This approach, requiring heteroleptic aggregation, goes
along with a conformational re-orientation of the functional units
Introduction
Due to their great potential as novel redox-active, catalytic,
in the linear ligand.
optical, and mechanical materials,1 the construction of functional
Recently, we have developed a strategy for multicomponent
supramolecular assemblies is a topic of current interest.2,3 While
ladder assemblies using the HETTAP (HETeroleptic Terpyridine
And Phenanthroline complexes) concept,14 which was used to en-
over the years substantial progress has been made to fabricate
impressive structures,4 the focus has recently turned towards
the interplay of energy- and electron-harvesting units, such as
multiple chromophore or redox relay systems, in supramolecular
aggregates.5,6 As indicated in Scheme 1, metallosupramolecular
assemblies are usually constructed by one of two main strategies
in order to set up polyfunctional aggregates. For some time,
approach A, positioning functional units as ligands on the
metal fragments, was the method of choice, mainly due to its
simplicity and flexibility.7 More recently, Hupp,8 Lehn,9 Stang,10
and Wu¨rthner11 have explored approach B1 leading to square
motifs, in which functional units were introduced along with the
organic spacer ligands. However, due to free rotation11c about
the central ligand axis these examples11 lack any directionality,
as either external or internal positions may be occupied. As a way
out, functional units were placed both externally and internally
(Scheme 1; eqn (2)). The problem is better addressed by the
directional approach B2 developed by Fujita et al.12 Using the
concept depicted in eqn (3), they have prepared diverse 3D self-
assembled spherical complexes with endohedral functional units.
To supplement this, we now disclose strategy B2, eqn (4), providing
a way of incorporating highly-aligned functional units into ladder
2
gineer 2-dimensional nanoscaffolds14,15 with 2D cavities ≥290 A .
˚
The nanoscaffolds were readily prepared from linear shielded
bisphenanthrolines16 and linear bisterpyridines15 in the presence of
various metal ions, such as Zn2+, Cu+, and Hg2+. As this concept
provides an entry both to multicomponent aggregates17 whose
size can be varied depending on the length of the ligands, and
to directional attachment of various internal units (Scheme 1;
eqn (4)), we decided to explore its use for the preparation of
nanoscaffolds functionalised internally with redox relays. Based on
this conception, two nanoladders of different size were prepared
from bisphenanthroline 5 carrying two ferrocene units and from
bis-terpyridines 6 and 7 of varying length (Chart 1). Ferrocene
was chosen as a redox-active building block in 5 due to its well
defined redox properties. A flexible linkage was incorporated to
ensure some degree of self-organisation of the ferrocene group. The
length of the linkage was optimised from force field modelling of
the ladder structures. Accordingly, ferrocene units attached to a
hexamethylene linker should allow for easy arrangement within
the cavity of the suggested nanoscaffold L2 (see Fig. 1). Filling the
cavity with redox-active units should enable us to investigate the
supramolecular effect on the redox potential.18
aCenter of Micro- and Nanochemistry and Engineering, Organische Chemie,
Universita¨t Siegen, Adolf-Reichwein-Strasse, 57068 Siegen, Germany.
E-mail: schmittel@chemie.uni-siegen.de; Fax: +49 271-740-3270
Results and discussion
Synthesis of ligand 5
bInstitute fu¨r Organische Chemie und Chemische Biologie, Johann Wolfgang
Goethe-Universita¨t, Marie-Curie-Strasse 11, D-60439, Frankfurt am Main,
Germany
As a starting point for the preparation of the ferrocene-containing
bisphenanthroline 5 we resorted to phenanthroline 1 (Scheme 2).19
After removal of both protecting groups using 3 N KOH as
base, phenanthroline 2 was afforded in 89% yield. Following
† Electronic supplementary information (ESI) available: Numbering of
formulae for NMR assignments; NMR spectra; crystal data for 5; 3D
structure representations. See DOI: 10.1039/b703633g
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Scheme 1 Cartoon representation of the various approaches currently used for setting up supramolecular aggregates with functional units.
a Sonogashira cross-coupling protocol with [Pd(PPh3)2Cl2] and
CuI, the desired bisphenanthroline 3 was always accompanied
by a minor amount of the homo-coupling product of 2 (5%),
which caused major problems in the chromatographic purification.
Luckily, when [Pd(PPh3)4] was used as catalyst system, 3 was af-
forded in 90% yield after purification. Finally, a double Williamson
reaction of 1-(6-bromohexyl)ferrocene (4)20 with 3 generated the
bisferrocene-functionalised bisphenanthroline 5 in 80% yield.
exhibiting a distance between the two iron atoms of 2.95 nm.
The structure is centrosymmetric with a centre of inversion at the
midpoint of the central benzene ring. The distance of the two
terminal phenanthrolines is 1.75 nm. The crystal packing shows a
number of weak intermolecular C–H · · · p interactions.
Self-assembly of the ferrocene nanoladders L1 and L2 based on the
HETTAP concept
X-Ray structure of 5
With ligand 5 at hand and ligands 6–8 available through
earlier work15 and commercial suppliers, all ingredients for
the HETTAP synthesis14 were available. The synthesis of lad-
ders L1 ([Zn4(5)2(6)2)]8+) and L2 ([Zn4(5)2(7)2)]8+) and rack R1
(Zn(5)(8)2)]4+) was readily accomplished by treating (for example,
in the case of L1) 1 equiv. of 6 with a mixture of 1 equiv. of 5 and
2 equiv. of Zn(CF3SO3)2 in DCM–methanol (8 : 2) (Scheme 3).
Following a full (NMR, IR, MS) solution-state characterisation,
the formation of single crystals obtained by slow evaporation of
a DCM–acetonitrile (9 : 1) solution of 5 allowed for an X-ray
crystallographic analysis. Due to its conformational flexibility,
5 was present in a transoid conformation in the solid state. As
depicted in Fig. 2, the two ferrocene groups are well separated,
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Chart 1 Ligands used in the present study.
All 1H NMR spectral data point to the successful formation of
R1, L1 and L2. For example, the spectra of L1 and L2 in CD2Cl2–
CD3OD (8 : 2) (see ESI†) showed only one set for each ligand,
suggesting that a single species was obtained. Characteristic
upfield shifts of the mesityl protons (from d ∼ 6.7 and 6.9 ppm
in 5 to 5.8 and 6.2 ppm in R1, to 5.9 and 6.3 ppm in L1, and
to 5.9 and 6.2 ppm in L2 (see Table 1) and downfield shifts of
the phenanthroline protons (Dd ∼ 1.0 ppm) are in strong support
of the formation of the phen-Zn(II)-terpy complex units. Upon
complexation, the 1H NMR signals of the ferrocenyl protons
for R1 and L1 were shifted slightly downfield from d = 4.08 to
4.22 and 4.24 ppm, respectively, but the splitting patterns changed
dramatically in both cases. In contrast, the signals of ferrocenyl
protons in L2 showed that the splitting pattern was similar to that
of 5, except that the 10ꢀꢀꢀ-H were shifted upfield slightly rather than
downfield by 0.22 ppm.
Rewardingly, the ESI-MS spectra of L1 and L2 showed the
complete pattern of signals corresponding to 3+ to 8+ charged
species of L1 (Fig. 3) and L2, with the isotopic distribution of all
fragments exactly matching with the calculated ones after loss of
the counter-anions.
Electroanalytical investigations
While the combination of the spectroscopic data furnished strong
evidence for the proposed structures of L1 and L2, direct proof for
supramolecular interaction between ferrocene groups were derived
Fig. 1 Side (a) and top (b) views of space-filling presentations of
nanoladder L2 [Zn4(5)2(7)2)]8+ as generated from force field modelling
(HyperChemꢀR ). The atoms/groups are colour coded for clarity: carbon:
cyan; nitrogen: blue; oxygen: red; zinc: (hidden); ferrocene group: green.
Scheme 3 Cartoon representation of the preparation of nanorack R1 and
nanoladders L1 and L2.
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Scheme 2 Preparation of 5.
Fig. 2 Molecular structure of the ferrocene-appended rigid bisphenanthroline 5 as a stick representation. Carbon: gray, hydrogen: white, nitrogen: blue,
oxygen: red, iron: yellow. CCDC reference number 639848. For crystallographic data in CIF or other electronic format see DOI: 10.1039/b703633g
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Table 1 1H NMR shifts (in ppm, in CD2Cl2–CD3OD (8 : 2) at 400 MHz) of the ligand 5 and nanoscaffolds R1, L1 and L2
Bisphenanthroline protons
Ferrocene protons
8ꢀꢀꢀ,9ꢀꢀꢀ-H (m)
Compound
Mes2-H (s)
Mes1-H (s)
8-H (d)
7-H (d)
4-H (s)
10ꢀꢀꢀ-H (s)
4.08
5a
6.67
5.86
5.93
5.91
6.94
6.18
6.27
6.21
7.57
8.03
8.05
8.09
8.33
9.04
9.08
9.09
8.49
9.07
9.16
9.21
4.01–4.07
Rack R1
Ladder L1
Ladder L2
4.22 (br s)
4.24 (br s)
3.92–3.98
3.86
a In CD2Cl2.
Fig. 3 Left: ESI-MS spectrum of the nanoladder L1. Right: Isotopic distributions in the ESI-MS of L1 (black = experimental, red = calculated) showing
all charged species from 3+ to 8+.
from cyclic voltammetry (CV) and differential pulse voltammetry
(DPV) investigations.
All measurements were performed in acetonitrile using de-
camethylferrocene (DMFc) as internal standard. In contrast to
Wu¨rthner’s squares, for which a peak splitting of redox wave of
ferrocene units had been reported, suggesting the presence of
internal and external ferrocene units,11 a single oxidation wave
was observed for the Fc0,+ couple in 4, R1, L1 and L2 in CV
measurements (Fig. 4). This result suggests that ferrocene units
in the various structures are all placed in identical environments
on the time scale of the experiment.21 As indicated in Table 2, the
ferrocene unit of 4 shows an oxidation potential of 0.451 VDMFc
,
while that of R1 is 0.463 VDMFc. This small anodic shift22 of 12 mV
is most likely caused by formation of the phen-Zn(II)-terpy coordi-
nation unit, which ought to have some influence on the ferrocenes’
oxidation potential. Less likely is an intramolecular interaction
of the two ferrocene units, as we expect the conformation of R1
to correspond to that of 5. Accordingly, the ferrocenes should
be separated by 3 nm. The oxidation of the ferrocenes in ladders
L1 and L2 (0.483 VDMFc and 0.487 VDMFc) was effected at higher
anodic potentials (20–24 mV) than that in R1. The anodic shift
is attributed to the ladder structure, which should lead to a
compression of the four ferrocenes inside its inner void. As a result,
the “intramolecular” interaction of ferrocenes should become
perceptible. From the molecular structure of 5, we derive a distance
Fig. 4 CVs of compound 4, R1, L1 and L2 recorded in 0.10 M nBu4NPF6
in acetonitrile at a scan rate of 100 mV s−1
.
R1 has the same conformation as 5, the two ferrocene units in
R1 should be separated by the same distance. Evaluation of the
average distances of the four ferrocene iron atoms in the two
R
phen-Zn(II)-terpy ladders as obtained from HyperChemꢀ energy-
˚
˚
minimised structures provided values of 18.5 A and 15.2 A for
˚
between the two ferrocene iron atoms of 29.5 A. Assuming that
L1 and L2, respectively (see ESI† and Fig. 1). The short average
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Table 2 Reversible redox potentials of compounds vs. DMFc by cyclic voltammetry at a scan rate 100 mV s−1
ox
red
Compound
E1/2 (Fc2+/3+
)
DEp
E1/2 (terpy0/−
)
DEp
4
0.451 V
0.463 V
0.483 V
0.487 V
68 mV
67 mV
87 mV
77 mV
N/A
N/A
110 mV
88 mV
R1
L1
L2
−1.162 V
−1.135 V
−1.079 V, −0.941 V
94 mV, 64 mV
distance between the four iron atoms in L1 and L2 is enforced
by the supramolecular framework and should be the dominating
effect for the above-described anodic shifts.
anodic than those of R1, the 2 + 2 ladder frameworks seem to
resist dissociation of the reduced coordination sites much more
than R1, most likely due to cooperative effects. But when more
negative DPV starting potentials of −1.80 V and −2.00 V were
applied to L1 and L2, the ferrocene potentials now showed up
at 0.451 V for L1 and 0.462 V for L2 (Fig. 6). Under these
conditions, as for R1, reduction seems to lead to a disintegration
of the ladders. There are, however, differences between L1 and L2.
Upon starting the DPV investigation for L1 at −1.80 V, the ladder
showed disintegration as evidenced by an oxidation potential of
the ferrocene units at 0.451 V. The sweep does not only entail
reduction of the terpyridine, but also of the phenanthroline unit,
thereby causing irreparable dissociation of the phen-Zn(II)-terpy
coordination centres. L2 proved to be less susceptible to negative
starting potentials. Even when the DPV scan was initiated at
−2.00 V, the oxidation potential of the ferrocenes emerged at
0.462 V. We assign this small shift of 10 mV tentatively to a partially
broken ladder of L2. Due to its smaller size, ladder L2 suffers
probably less dissociation upon reduction than L1, as cooperative
effects are more pronounced.
DPV investigations on compounds 4, R1, L1 and L2 provided
further strong support for the above hypothesis (Table 3). When
the voltage was scanned from −0.30 V to 1.00 V, the peak values
corresponding to ferrocene units in 4, R1, L1 and L2 were 0.452,
0.462, 0.480 and 0.491 VDMFc, respectively (Fig. 5). These results are
in perfect agreement with those from CV measurements. Intrigu-
ingly, upon recording DPVs for 4 and R1 from −1.60 V to 1.00 V,
the oxidation potentials of ferrocene units for both compounds
nearly coincided at 0.452 and 0.454 V, respectively. Clearly, the ca.
10 mV anodic shift observed for R1 as compared to 4, attributed
to the formation of the phen-Zn(II)-terpy coordination unit, has
disappeared in this experiment. This suggests, that upon starting
the measurement at −1.60 V, the terpyridine unit of R1 is reduced,
leading to a dissociation of the coordination complex, which is not
repaired on the DPV time scale. As a consequence, the released
ligand 5 is then detected in the DPV of R1, quite obviously
exhibiting the same oxidation potential for the ferrocene unit as
4. In contrast, DPVs of L1 and L2 starting from −1.60 V showed
no change compared to those starting from −0.30 V. Since the
reduction potential of the terpyridine units in L1 and L2 is more
Fig. 6 DPVs of compounds 4, R1, L1 and L2 recorded in 0.10 M
nBu4NPF6 in acetonitrile. Step potential 2 mV, starting scan in between
−2.00 and −1.60 V, finishing scan at 1.00 V.
Fig. 5 DPVs of compounds 4, R1, L1 and L2 recorded in 0.10 M
nBu4NPF6 in acetonitrile. Step potential 2 mV, scan range from −0.30 V
to 1.00 V.
Conclusion
Table 3 DPV measurements. Step potential 2 mV, scan range from
−0.30 V to 1.00 V
Employing a directional approach using the HETTAP concept,
we have achieved the synthesis of three internally functionalised
supramolecular aggregates: the nanoscale rack R1, and nanolad-
ders L1 and L2, containing two and four ferrocenes, respectively.
The redox potential of the ferrocene units in R1 was slightly
Compound
4
R1
L1
L2
ox
E1/2 (Fc2+/3+
)
0.452 V
0.462 V
0.480 V
0.491 V
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anodically shifted by ca. 10 mV compared with that of 4, due
to the influence of the remote phen-Zn(II)-terpy coordination
centre. In contrast, the ladder structure of L1 and L2 forces four
ferrocene units into close proximity, thereby dramatically increas-
ing their through-space interaction as demonstrated by the redox
1,4-Bis[(2-(4-hydroxy-2,6-dimethylphenyl)-9-mesityl-
[1,10]phenanthroline-3-ylethynyl]benzene (3)
Phenanthroline 2 (91.2 mg, 206 lmol), 1,4-diiodobenzene
(34.0 mg, 103 lmol) and [Pd(PPh3)4] (11.5 mg, 10.0 lmol) were
dissolved in dry DMF (15 mL) and dry triethylamine (15 mL).
After deoxygenating the reaction mixture with nitrogen for 15 min,
it was heated to 60 ◦C for 4 h. Then the solvents were removed at
reduced pressure, and the residue was washed with water (30 mL)
and dichloromethane (30 mL) to afford the crude product. It was
recrystallised from DMF to afford a light yellow solid (88.9 mg,
92.7 lmol, 90%). Mp >300 ◦C. IR (KBr): m˜ = 3363 (w), 2963 (w),
2920 (w), 2212 (w), 1614 (s), 1586 (s), 1506 (m), 1458 (s), 1396
(m), 1317 (s), 1159 (s), 1034 (w), 909 (m), 889 (m), 850 (s), 776
potential results. The redox potential series (vs. DMFc: E1/2
=
0.462 V for R1, 0.480 V for L1 and 0.491 V for L2), as determined
by DPV, thus revealed convincingly the supramolecular effect on
a redox process.
Experimental
All reagents were commercially available and used without further
purification. Thin-layer chromatography was performed using
silica gel 60 TLC plates (F254, Merck). Silica gel (0.063–0.2 mm)
was used for column chromatography. Confirmation of structures
was obtained from 1H-NMR and 13C-NMR data (Bruker AC200
and Avance 400 spectrometer) using the deuterated solvent as
the lock and residual solvent as the internal reference. The
numbering of carbon atoms of molecular formulae as provided
below is only used for the assignment and is not in accordance
with the IUPAC nomenclature rules. Melting points were taken
using the melting point apparatus of Dr Tottoli (Bu¨chi) and are
uncorrected. Electrospray mass spectra (ESI-MS) were recorded
on a ThermoQuest LCQ Deca instrument. Infrared spectra were
recorded on a Perkin Elmer 1750 FT-IR spectrometer. Cyclic
voltagram (CV) and differential pulse voltammograms (DPV)
were recorded on a Parstat 2273 instrument from Princeton
Applied Research.
1
(w), 639 (m). H-NMR (200 MHz, DMF-d7): d = 2.02 (s, 12H,
7ꢀ-, 8ꢀ-H), 2.05 (s, 12H, 7ꢀꢀꢀ-, 9ꢀꢀꢀ-H), 2.32 (s, 6H, 8ꢀꢀꢀ-H), 6.70 (s, 4H,
3ꢀ, 5ꢀ-H), 6.99 (s, 4H, 3ꢀꢀꢀ-, 5ꢀꢀꢀ-H), 7.30 (s, 4H, 4ꢀ-, 5ꢀ-H), 7.78 (d,
J = 8.1 Hz, 2H, 8-H), 8.15 (d, J = 8.8 Hz, 2H, 6-H), 8.20 (d,
J = 8.8 Hz, 2H, 5-H), 8.66 (d, J = 8.1 Hz, 2H, 7-H), 8.87 (s, 2H,
4-H), 9.56 (br s, 2H, 9ꢀ-H). 13C-NMR (50 MHz, DMSO-d6): d =
19.7, 21.0, 21.7, 80.6, 85.6, 113.9, 114.0, 118.7, 121.9, 125.0, 125.7,
126.4, 127.2, 127.5, 128.1, 128.2, 130.7, 135.1, 136.6, 136.9, 137.8,
140.5, 144.3, 145.0, 156.8, 159.6, 160.9. ESI-MS Calcd for [M +
H]+: m/z 959.4, Found: m/z 959.6; ESI-MS Calcd for [M + 2H]2+:
m/z 480.2, Found: m/z 480.3. Anal calcd for C68H54N4O2·H2O: C,
83.58; H, 5.78; N, 5.73; found: C, 83.96; H, 5.71; N, 5.81.
1,4-Bis{2-[2,6-dimethyl-4-(6-ferrocenylhexyloxy)phenyl]-9-
mesityl-[1,10]phenanthroline-3-ylethynyl}benzene (5)
Compound 3 (100 mg, 104 lmol) was dissolved in dry DMF
(30 mL). NaH (60% in mineral oil, 60 mg, 2.50 mmol) was added
and the mixture was then stirred for 1 h at room temperature. After
addition of 6-bromohexylferrocene (4)2◦0 (140 mg, 400 lmol), the
reaction mixture was heated to 80–90 C (oil bath temperature)
for 24 h. The reaction was quenched by careful addition of water
(50 mL) and neutralised with saturated NH4Cl solution. After
extraction with DCM (3 × 50 mL), the organic layer was dried
over MgSO4. Then the solvent was removed at reduced pressure
and the crude product was purified by column chromatography
(SiO2, dichloromethane) to afford the product as a yellow solid
(124 mg, 82.9 lmol, 80%). Mp >300 ◦C. IR (KBr): m˜ = 2924 (s),
2855 (m), 2210 (w), 1605 (s), 1583 (m), 1500 (w), 1459 (s), 1396 (w),
1316 (m), 1160 (s), 1105 (w), 1071 (w), 887 (m), 849 (s), 637 (w),
3-Ethynyl-2-(4-hydroxy-2,6-dimethylphenyl)-9-mesityl-
[1,10]phenanthroline (2)
Compound 119 (7.00 g, 10.4 mmol, 2-(4-triisopropylsilyloxy-2,6-
dimethylphenyl)-9-mesityl-3-(trimethylsilylethynyl)-[1,10]phenan-
throline) was dissolved in a mixture of methanol (100 mL) and
THF (100 mL), and KOH (3 N in H2O, 100 mL) was added slowly.
After stirring for 24 h at room temperature, the solution was
neutralised with sat. NH4Cl and extracted with dichloromethane
(200 mL). The organic layer was dried over MgSO4. After
removal of the solvent at reduced pressure, the crude product was
recrystallised from dichloromethane to afford the product as a
white solid (4.11 g, 9.28 mmol; 89%). Mp 290–291 ◦C. IR (KBr):
m˜ = 3408 (w), 3312 (w), 2918 (w), 1616 (s), 1600 (s), 1583 (s), 1539
(w), 1506 (w), 1458 (s), 1395 (m), 1319 (s), 1152 (s), 1034 (m),
1
485 (w). H-NMR (400 MHz, CD2Cl2): d = 1.40–1.61 (m, 12H,
3ꢀꢀꢀ-, 4ꢀꢀꢀ-, 5ꢀꢀꢀ-H), 1.80–1.87 (m, 4H, 2ꢀꢀꢀ-H), 2.06 (s, 12H, 7ꢀ-, 8ꢀ-H),
2.07 (s, 12H, 7ꢀꢀ-, 9ꢀꢀ-H), 2.34 (s, 6H, 8ꢀꢀ-H), 2.36 (t, J = 7.6 Hz, 4H,
6ꢀꢀꢀ-H), 4.00–4.07 (m, 12H, 1ꢀꢀꢀ-, 8ꢀꢀꢀ-, 9ꢀꢀꢀ-H), 4.08 (s, 10H, 10ꢀꢀꢀ-H),
6.72 (s, 4H, 3ꢀ-, 5ꢀ-H), 6.97 (s, 4H, 3ꢀꢀ-, 5ꢀꢀ-H), 7.15 (s, 4H, 4ꢀ-, 5ꢀ-H),
7.57 (d, J = 8.1 Hz, 2H, 8-H), 7.86 (d, J = 8.8 Hz, 2H, 6-H),
7.91 (d, J = 8.8 Hz, 2H, 5-H), 8.33 (d, J = 8.1 Hz, 2H, 7-H), 8.49
(s, 2H, 4-H). 13C-NMR (100 MHz, CD2Cl2): d = 20.3, 20.4, 21.2,
26.3, 29.6, 29.7, 29.8, 31.5, 67.3, 68.3, 68.4, 68.8, 89.3, 89.8, 94.5,
113.6, 120.0, 123.2, 125.2, 125.9, 127.2, 127.3, 128.0, 128.6, 131.8,
132.9, 136.0, 136.4, 137.8, 138.0, 138.4, 139.0, 145.4, 146.4, 159.0,
160.9, 161.8. ESI-MS Calcd for [M + H]+: m/z 1495.6, Found:
m/z 1495.9, Calcd for [M + 2H]2+: m/z = 748.3, Found: m/z =
748.4. Anal calcd for C100H94Fe2N4O2: C, 80.31; H, 6.34; N, 3.75;
found: C, 80.10; H, 6.34; N, 3.71.
1
910 (m), 891 (w), 851 (s), 778 (w), 637 (s), 616 (m). H-NMR
(200 MHz, DMSO-d6): d = 1.86 (s, 6H, 7ꢀ-, 8ꢀ-H), 1.96 (s, 6H,
7ꢀꢀꢀ-, 9ꢀꢀꢀ-H), 2.29 (s, 3H, 8ꢀꢀꢀ-H), 4.32 (s, 1H, 2ꢀ-H), 6.54 (s, 2H, 3ꢀ,
5ꢀ-H), 6.97 (s, 2H, 3ꢀꢀꢀ-, 5ꢀꢀꢀ-H), 7.68 (d, J = 8.1 Hz, 1H, 8-H), 8.03
(d, J = 8.9 Hz, 1H, 6-H), 8.10 (d, J = 8.9 Hz, 1H, 5-H), 8.56 (d,
J = 8.1 Hz, 1H, 7-H), 8.77 (s, 1H, 4-H), 9.35 (br s, 1H, 9ꢀ-H).
13C-NMR (50 MHz, DMSO-d6): d = 19.7, 19.8, 20.8, 80.6, 85.9,
113.9, 118.7, 121.9, 125.0, 125.7, 126.4, 127.1, 127.5, 128.1, 130.7,
135.1, 136.6, 136.9, 137.8, 140.3, 144.3, 145.0, 156.8, 159.6, 160.9.
ESI-MS Calcd for [M + H]+: m/z 443.2, Found: m/z 443.2. Anal
calcd for C31H26N2O·1.5H2O: C, 79.29; H, 6.22; N, 5.97; found:
C, 79.04; H, 5.96; N, 6.16.
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Nanorack R1
m/z 685.0, found: m/z 685.0, calcd. for [M − 6OTf−]6+: m/z 824.1,
found: m/z 823.9, calcd. for [M − 5OTf−]5+: m/z 1018.7, found:
m/z 1018.5, calcd. for [M − 4OTf−]4+: m/z 1310.6, found: m/z
1310.6, calcd. for [M − 3OTf−]3+: m/z 1797.2, found: m/z 1796.9.
Anal calcd for C304H260F24Fe4N20O28S8Zn4·3CH2Cl2: C, 60.51; H,
4.40; N, 4.60; S, 4.21; found: C, 60.78; H, 4.24; N, 4.51; S, 4.33.
The ferrocene ligand 5 (5.00 mg, 3.34 lmol) and Zn(CF3SO3)2
(2.43 mg, 6.68 lmol) were dissolved in deuterated
dichloromethane–methanol (8 : 2, 0.6 mL),14 and terpyridine (8)
(1.54 mg, 6.68 lmol) was added. The resulting suspension was
heated for a few minutes until a clear solution had formed. It
was analysed by ESI-MS, H-, 13C-NMR and elemental analysis
1
Nanoladder L2
without any further purification. Mp >300 ◦C. IR (KBr): m˜ =
3422 (w), 3081 (w), 2927 (m), 2855 (m), 2213 (w), 1602 (m),
1579 (m), 1479 (w), 1456 (m), 1407 (w), 1322 (w), 1262 (s), 1223
Ligand 5 (5.00 mg, 3.34 lmol) and Zn(CF3SO3)2 (2.43 mg,
6.68 lmol) were dissolved in deuterated dichloromethane–
methanol (8 : 2, 0.6 mL),14 then bisterpyridine 7 (1.81 mg,
3.34 lmol) was added. The resulting suspension was heated for
a few minutes until a clear solution had formed. It was analysed
1
(m), 1155 (s), 1031 (s), 854 (w), 638 (s). H-NMR (400 MHz,
CD2Cl2–CD3OD (8 : 2)): d = 1.12 (s, 24H, 7ꢀ-, 8ꢀ-, 7ꢀꢀ-, 9ꢀꢀ-H),
1.31–1.37 (m, 8H, 3ꢀꢀꢀ-, 4ꢀꢀꢀ-H), 1.48–1.60 (m, 8H, 2ꢀꢀꢀ-, 5ꢀꢀꢀ-H), 1.79
(s, 6H, 8ꢀꢀ-H), 2.25 (br s, 4H, 6ꢀꢀꢀ-H), 3.46 (t, J = 6.3 Hz, 4H,
1ꢀꢀꢀ-H), 4.22 (br s, 18H, 8ꢀꢀꢀ-, 9ꢀꢀꢀ-, 10ꢀꢀꢀ-H), 5.86 (s, 4H, 3ꢀ-, 5ꢀ-H),
6.18 (s, 4H, 3ꢀꢀ-, 5ꢀꢀ-H), 7.00 (s, 4H, 4ꢀ-, 5ꢀ-H), 7.53 (ddd, J =
7.7 Hz, 5.1 Hz, 1.0 Hz, 4H, b-H), 7.76 (dd, J = 5.1 Hz, 1.0 Hz,
4H, a-H), 8.03 (d, J = 8.1 Hz, 2H, 8-H), 8.27 (dt, J = 7.7 Hz,
1.6 Hz, 4H, c-H), 8.42–8.50 (m, 14H, d-, e-, f-, 5-, 6-H), 9.04 (d,
J = 8.1 Hz, 2H, 7-H), 9.07 (s, 2H, 4-H). 13C-NMR (100 MHz,
CD2Cl2–CD3OD (8 : 2)): d = 19.2, 19.4, 20.7, 26.2, 29.3, 29.6,
29.7, 31.2, 68.2, 68.4 (Fc), 69.3 (Fc), 70.0 (Fc), 86.2, 97.8, 112.7,
122.7, 123.1, 123.6, 124.5, 127.9, 128.0, 128.2, 128.5, 129.0,
129.1, 129.6, 130.0, 132.1, 134.7, 135.3, 137.3, 139.8, 140.5, 141.4,
143.1, 143.2, 144.2, 144.7, 146.8, 147.6, 149.5, 160.1, 161.6, 162.8.
ESI-MS: calcd. for [M − 4OTf−]4+: m/z 523.2, found: m/z 523.2,
calcd. for [M − 3OTf−]3+: m/z 747.3, found: m/z 746.9, calcd. for
[M − 2OTf−]2+: m/z 1195.5, found: m/z 1195.4. Anal calcd for
C134H116F12Fe2N10O14S4Zn2·0.5CH2Cl2: C, 59.14; H, 4.32; N, 5.13;
S, 4.70; found: C, 59.16; H, 4.16; N, 5.10; S, 4.65.
1
by ESI-MS, H-, 13C-NMR and elemental analysis without any
◦
further purification. Mp >300 C. m˜ = 3402 (w), 3094 (w), 2922
(m), 2855 (m), 2212 (w), 1605 (s), 1577 (m), 1477 (w), 1459 (m),
1400 (w), 1279 (s), 1254 (s), 1161 (s), 1031 (s), 854 (w), 639 (s).
1H-NMR (400 MHz, CD2Cl2–CD3OD (8 : 2)): d = 1.10 (s, 24H,
7ꢀ-, 8ꢀ-H), 1.16 (s, 24H, 7ꢀꢀ-, 9ꢀꢀ-H), 1.12–1.37 (m, 32H, 2ꢀꢀꢀ-, 3ꢀꢀꢀ-,
4ꢀꢀꢀ-, 5ꢀꢀꢀ-H), 1.72 (s, 12H, 8ꢀꢀ-H), 2.10 (br s, 8H, 6ꢀꢀꢀ-H), 3.43 (t,
J = 6.4 Hz, 8H, 1ꢀꢀꢀ-H), 3.86–3.98 (m, 36H, 8ꢀꢀꢀ-, 9ꢀꢀꢀ-, 10ꢀꢀꢀ-H), 5.91
(s, 8H, 3ꢀ-, 5ꢀ-H), 6.21 (s, 8H, 3ꢀꢀ-, 5ꢀꢀ-H), 7.00 (s, 8H, 4ꢀ-, 5ꢀ-H),
7.53 (td, J = 5.1 Hz, 1.2 Hz, 8H, b-H), 7.76 (d, J = 5.1 Hz,
8H, a-H), 8.08 (d, J = 8.1 Hz, 4H, 8-H), 8.30 (td, J = 8.1 Hz,
1.2 Hz, 8H, c-H), 8.48 (d, J = 8.8 Hz, 4H, 6-H), 8.52 (d, J =
8.8 Hz, 4H, 5-H), 8.60 (s, 8H, e-H), 8.92 (d, J = 8.1 Hz, 8H,
d-H), 9.03 (s, 8H, f-H), 9.08 (d, J = 8.1 Hz, 4H, 7-H), 9.21 (s,
4H, 4-H). 13C-NMR (100 MHz, CD2Cl2/CD3OD (8:2)): d = 19.4,
19.5, 20.7, 25.4, 26.0, 29.5, 29.9, 31.3, 67.7, 68.3, 68.6, 70.0, 86.4,
97.79, 101.4, 109.2, 112.9, 116.4, 119.5, 120.6, 122.8, 124.5, 125.9,
128.1, 128.5, 129.3, 130.1, 132.4, 134.9, 135.4, 137.6, 138.0, 140.0
(2C), 140.8, 141.5, 142.2, 143.5, 144.7, 146.8, 147.3 (2C), 148.5,
149.4, 155.5 (2C), 161.4, 161.9, 162.8. ESI-MS: calcd. for [M −
8OTf−]8+: m/z 541.7, found: m/z 541.6, calcd. for [M − 7OTf−]7+:
m/z 640.4, found: m/z 640.3, calcd. for [M − 6OTf−]6+: m/z 772.0,
found: m/z 772.2, calcd. for [M − 5OTf−]5+: m/z 956.2, found: m/z
955.9, calcd. for [M − 4OTf−]4+: m/z 1232.5, found: m/z 1232.2,
calcd. for [M − 3OTf−]3 m: m/z 1693.1, found: m/z 1692.8. Anal
calcd for C280H236F24Fe4N20O28S8Zn4·CH2Cl2: C, 60.15; H, 4.28; N,
4.99; S, 4.57; found: C, 59.89; H, 4.16; N, 4.87; S, 4.77.
Nanoladder L1
Ligand 5 (5.00 mg, 3.34 lmol) and Zn(CF3SO3)2 (2.43 mg,
6.68 lmol) were dissolved in deuterated dichloromethane–
methanol (8 : 2, 0.6 mL),14 and bisterpyridine 6 (2.33 mg,
3.34 lmol) was added. The resulting suspension was heated for
a few minutes until a clear solution had formed. It was analysed
1
by ESI-MS, H-, 13C-NMR and elemental analysis without any
◦
further purification. Mp >300 C. m˜ = 3083 (w), 2926 (m), 2854
(m), 2211 (w), 1603 (s), 1577 (m), 1476 (m), 1420 (w), 1261 (s),
1
1223 (m), 1160 (s), 1031 (s), 852 (w), 797 (w), 638 (s). H-NMR
Acknowledgements
(400 MHz, CD2Cl2–CD3OD (8 : 2)): d = 1.18 (s, 24H, 7ꢀ-, 8ꢀ-H),
1.22 (s, 24H, 7ꢀꢀ-, 9ꢀꢀ-H), 1.17–1.40 (m, 24H, 2ꢀꢀꢀ-, 3ꢀꢀꢀ-, 4ꢀꢀꢀ-H), 1.54
(br s, 8H, 5ꢀꢀꢀ-H), 1.90 (s, 12H, 8ꢀꢀ-H), 2.19–2.26 (m, 32H, 6ꢀꢀꢀ-, g-H),
3.53 (t, J = 6.3 Hz, 8H, 1ꢀꢀꢀ-H), 4.24 (br s, 36H, 8ꢀꢀꢀ-, 9ꢀꢀꢀ-, 10ꢀꢀꢀ-H),
5.93 (s, 8H, 3ꢀ-, 5ꢀ-H), 6.27 (s, 8H, 3ꢀꢀ-, 5ꢀꢀ-H), 7.05 (s, 8H, 4ꢀ-, 5ꢀ-H),
7.55–7.58 (m, 16H, b-, f-H), 7.81 (d, J = 4.8 Hz, 8H, a-H), 8.05
(d, J = 8.3 Hz, 4H, 8-H), 8.24–8.28 (m, 16H, c-, e-H), 8.40 (d,
J = 8.1 Hz, 8H, d-H), 8.48 (d, J = 9.4 Hz, 4H, 6-H), 8.53 (d,
J = 9.4 Hz, 4H, 5-H), 9.08 (d, J = 8.3 Hz, 4H, 7-H), 9.16 (s, 4H,
4-H). 13C-NMR (100 MHz, CD2Cl2–CD3OD (8 : 2)): d = 19.3,
19.6, 20.9, 21.0, 26.1, 29.4, 29.6, 29.7, 31.2, 68.4, 69.5 (Fc), 86.2,
90.2, 97.8, 112.8, 119.3, 122.4, 122.8, 123.6, 124.1, 124.6, 124.8,
128.0, 128.5, 128.9, 129.1, 129.3, 129.7, 130.0, 131.7, 132.2, 134.7,
135.5, 135.9, 137.1, 137.6, 140.0, 140.4, 141.6, 143.4, 144.7, 146.5,
148.0, 149.6, 158.7, 160.3, 161.8, 162.7. ESI-MS: calcd. for [M −
8OTf−]8+: m/z 580.8, found: m/z 580.7, calcd. for [M − 7OTf−]7+:
We are grateful to the Deutsche Forschungsgemeinschaft and the
Fonds der Chemischen Industrie. In addition, we are indebted to
Dr Mal for providing us with ligand 6.
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