Self-assembly of supramolecular architectures and polymers by orthogonal metal complexation and hydrogen-bonding motifs

Article abstract of DOI:10.1002/chem.201100171

A modular construction kit with two orthogonal noncovalent binding sites for self-assembly of supramolecular architectures is presented. The heteroditopic building blocks contain a terpyridine (tpy) unit for coordination of metal ions and a Hamilton receptor for multiple H-bonding of cyanuric acid derivatives. The association constants of ligand binding of M^II complexes (M=Ru, Zn, Fe, and Pt) with a dendritic end cap were determined to be in the range of 10² and 10⁴ L mol^-1 in chloroform. The capabilities for binding of metal ions were investigated by ¹H NMR and UV/Vis spectroscopy. The Fe complexes are most appropriate for the generation of discrete and high-ordered architectures due to their strong tendency to form FeL₂ complexes. Superstructures are readily formed in a one-pot procedure at room temperature. No mutual interactions between the orthogonal binding motifs were observed, and this demonstrates the highly specific nature of each binding process. Decomplexation experiments were carried out to examine the reversibility of Fe-tpy coordination. Substitution of the terminal end cap with a homoditopic bis-cyanurate linkage leads to formation of an iron-containing supramolecular strand. Formation of coordination polymers was confirmed by viscosity measurements. The supramolecular polymer strands can be reversibly cleaved by addition of a terminating cyanuric acid building block, and this proves the dynamic nature of this noncovalent polymerization process. Copyright

Full text of DOI:10.1002/chem.201100171

DOI: 10.1002/chem.201100171
Self-Assembly of Supramolecular Architectures and Polymers by Orthogonal
Metal Complexation and Hydrogen-Bonding Motifs
Felix Grimm,[a] Nadine Ulm,[a] Franziska Grçhn,[b] Jasmin Dꢀring,[b] and
Andreas Hirsch*[a]
Dedicated to Prof. Michael Hanack on the occasion of his 80th birthday
Abstract: A modular construction kit
with two orthogonal noncovalent bind-
ing sites for self-assembly of supra-
molecular architectures is presented.
The heteroditopic building blocks con-
tain a terpyridine (tpy) unit for coordi-
nation of metal ions and a Hamilton
receptor for multiple H-bonding of cy-
anuric acid derivatives. The association
constants of ligand binding of MII com-
plexes (M=Ru, Zn, Fe, and Pt) with a
dendritic end cap were determined to
be in the range of 102 and 104 Lmolꢀ1
in chloroform. The capabilities for
binding of metal ions were investigated
The Fe complexes are most appropri-
ate for the generation of discrete and
high-ordered architectures due to their
strong tendency to form FeL2 com-
plexes. Superstructures are readily
formed in a one-pot procedure at room
temperature. No mutual interactions
between the orthogonal binding motifs
were observed, and this demonstrates
the highly specific nature of each bind-
ing process. Decomplexation experi-
ments were carried out to examine the
reversibility of Fe–tpy coordination.
Substitution of the terminal end cap
with a homoditopic bis-cyanurate link-
age leads to formation of an iron-con-
taining supramolecular strand. Forma-
tion of coordination polymers was con-
firmed by viscosity measurements. The
supramolecular polymer strands can be
reversibly cleaved by addition of a ter-
minating cyanuric acid building block,
and this proves the dynamic nature of
this noncovalent polymerization pro-
cess.
Keywords: coordination polymers ·
hydrogen bonds · self-assembly ·
supramolecular chemistry · terpyri-
dine ligands
1
by H NMR and UV/Vis spectroscopy.
Introduction
on supramolecular dendrimers bearing two orthogonal non-
covalent binding sites, namely, the Hamilton receptor and
metal–ligand complexation of Ru and bipyridine. To expand
this concept and to enlarge the number of modular building
blocks, we employ now also the terpyridine (tpy) ligand,
which has been known for nearly a century to form stable
Supramolecular organization[1,2] is one of the most impor-
tant concepts of modern chemical research. Noncovalent in-
teractions facilitate spontaneous, thermodynamically con-
trolled self-assembly[3] of building blocks to multicomponent
architectures including supramolecular polymers. Among
the most common binding motifs for generating supramolec-
ular structures are hydrogen-bonding interactions[4–6] and
metal–ligand coordination.[7–9] A well-established hydrogen-
bonding building block is the Hamilton receptor[5,10] (see
Scheme 2 below), which forms stable complexes with cyanu-
ric acid derivatives with association constants ranging from
103 to 106 mꢀ1 in apolar solvents.[11] We recently[12] reported
complexes with
a
wide range of transition metals.[13]
2,2’:6’,2’’-Terpyridine became a key building block in supra-
molecular chemistry over the last decade and has been in-
corporated into polymers and copolymers.[14,15] Interesting
examples of terpyridines combined with hydrogen-bonding
units were reported by Lehn et al.,[16] Schubert et al.,[17] and
Schmuck et al.[18] Since the applied hydrogen-bonding sites
are self-complementary, these building blocks form single-
stranded polymers in solution or in the solid state. We
report here for the first time on the design of building
blocks bearing terpyridine units and an orthogonal hetero-
complementary hydrogen-bonding motif, namely, the Hamil-
ton receptor. Combination with suitable counterparts ena-
bles spontaneous self-assembly of ordered metal-centered
superstructures or supramolecular polymers (Scheme 1).
[a] F. Grimm, N. Ulm, Prof. Dr. A. Hirsch
Department of Chemistry and Pharmacy & Interdisciplinary Centre
for Molecular Materials (ICMM)
Friedrich-Alexander Universitꢀt Erlangen-Nꢁrnberg
Henkestrasse 42, 91054 Erlangen (Germany)
Fax : (+49)9131-85-26864
E-mail: andreas.hirsch@chemie.uni-erlangen.de
[b] F. Grçhn, J. Dꢁring
Department of Chemistry & Interdisciplinary Centre for Molecular
Materials (ICMM), Institute of Physical Chemistry
Friedrich-Alexander Universitꢀt Erlangen-Nꢁrnberg (Germany)
Results and Discussion
Supporting information (details of titration experiments) for this arti-
cle is available on the WWW under http://dx.doi.org/10.1002/
chem.201100171.
Heteroditopic ligand 1 is formed by coupling of 2,2’:6’,2’’-ter-
pyridine-4’-carboxylic acid (2) with amine-functionalized
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FULL PAPER
Scheme 1. Generation of supramolecular architectures and supramolec-
ular polymers by combining an orthogonal building block with suitable
counterparts.
the solubility of the target molecule. The resulting diethyl
ester was hydrolyzed to corresponding diacid 12 as de-
scribed in the literature.[20–21]
Bis-cyanurate 9 was obtained
by Steglich condensation with
dicyclohexylcarbodiimide
(DCC), 4-dimethylaminopyri-
dine (DMAP), and 1-hydroxy-
benzotriazole (HOBt) as cou-
pling reagents and 1-(6-hydrox-
yhexyl)-1,3,5-triazin-2,4,6-
trione[19] (13) as the corre-
sponding appropriate alcohol
at moderate temperatures. Pu-
rification by column chroma-
tography afforded 9 in accepta-
ble yield (57%).
In first attempts to generate
a homoleptic bis-tpy-contain-
ing metal complex we chose
RuII as central metal ion, be-
cause it is known to form ki-
netically inert complexes with
tpy[22] and also proved to be an
appropriate metal for related
RuACTHNUTRGENUG(N bpy)3 superstructures that
Scheme 2. Synthesis of orthogonal tpy ligands 1 and 7. a) EDC, THF (RT!508C, 72 h), yield: 52%; b) EDC,
we synthesized previously.[12]
We used RuCl3·xH2O (in the
presence of MeOH, EtOH, or
DMF (0!508C, 20 h), yield: 73%; c) 1m NaOH (RT, 14 h), yield: 80%; d) EDC, THF (508C, 14 h), yield:
68%.
4-ethylmorpholine as reducing
[23]
Hamilton receptor 3[5] (Scheme 2). Due to the poor solubili-
ty of the ligand and the resulting complexes in aprotic sol-
vents, we modified the building block by introduction of
Me-protected aminohexanoic acid 4 as linker. After depro-
tection of methyl ester 5, carboxylic acid 6 can be converted
to orthogonal bis-receptor 7 by 1-ethyl-3-(3-dimethylamino-
propyl) carbodiimide (EDC) coupling (Scheme 2). As ex-
pected, modified heteroditopic ligand 7 is very soluble in
chloroform and dichloromethane, and also in more polar
solvents like acetonitrile or methanol.
agent) and [RuACTHNGUTERNNUG
(DMSO)4]Cl2 as sources of RuII. Addition-
ally, AgPF6 was added to the reaction mixture to provide
the PF6 counterion. Reactions with the two tpy ligands af-
ACHUTTNGERN(NUG PF6)2 (14) and [Ru(7)2]ACHTUNGTRENNUNG(PF6)2
(15),which could be fully characterized.
ꢀ
forded complexes [Ru(1)2]
For the binding Hamilton receptors, a variety of end caps
with a cyanuric acid moiety has been investigated previous-
ly.[11,19] We decided to use first-generation dendritic ligand 8
as an end cap.[12]
Synthesis of homoditopic building block 9 (Scheme 3)
started from diethyl 2,5-dihydroxyterephthalate (10). Con-
version of the hydroxyl groups of the terephthalate to corre-
sponding bis(dodecyl ether) 11 was carried out to improve
Scheme 3. Synthesis of bis-cyanurate 9. a) 1-Dodecylbromide, K2CO3,
acetone (reflux, 4 d), yield: 70%; b) 30% KOH (aq) (reflux, 8 h), yield:
87%; c) DCC, DMAP, HOBt (508C, 7 d), yield: 57%.
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A. Hirsch et al.
Despite many attempts to alter the reaction conditions or
increase the reaction time, the ruthenium complexes could
be obtained only in low yields (<10%), and formation of
several unidentified byproducts was observed. However, for
self assembly of our desired supramolecular architectures,
complete conversion and well-defined structures are a basic
requirement. Therefore, we also investigated complexation
of a series of additional transition metal ions. Bis-complexes
of tpy are known to be formed
The capability to form complexes with cyanuric acid de-
rivatives was investigated by titration of 7 with end cap 8.
As expected, the NH signals of the Hamilton receptor are
significantly shifted downfield[19] on complexation, and the
graph depicts saturation when all available binding sites are
occupied (Figure 1). The determined association constant
K
ass =7.2ꢃ103 Lmolꢀ1 is in good agreement with those for
other Hamilton receptor/cyanuric acid complexes reported
with a wide range of different
transition metal ions including
CuII, CoII, NiII, ZnII, and FeII.
The resulting complexes of Cu,
Co, and Ni could be generated
and detected by UV/Vis spec-
troscopy and mass spectrome-
try, but have not been isolated
and characterized in detail yet
and will not be discussed here.
The zinc and iron complexes
[Zn(1)2]
(OTf)2 (17), [Fe(1)2]
(18), and [Fe(7)2](PF6)2 (19),
however, are readily available
under moderate reaction temperatures. They could be isolat-
ed in pure form and good yields (>70%). Moreover, under
stoichiometric reaction conditions, no substantial formation
of byproducts was observed. In the case of iron, also the
complexes with chloride counterions [Fe(1)2]Cl2 (20) and
ACHTUNGTRENNUNG
Figure 1. NMR titration (300 MHz, CDCl3) of 7 with end cap 8. a) Chemical resonance shift. b) Species distri-
bution.
G
E
ACHTUNGTRENNUNG
previously.[12,19] Orthogonal building block 1 is virtually in-
soluble in chloroform. Nevertheless, on addition of end cap
8, the solubility increases considerably. After addition of
one equivalent, the NH signals of the Hamilton receptor are
shifted from d=8.58 and 8.78 ppm to d=9.36 and 9.61 ppm,
respectively, and the resulting structure is readily soluble in
chloroform at room temperature. Addition of more than
one equivalent of end cap 8 leads only to a slight downfield
shift, indicating formation of a 1:1 hydrogen-bonding motif.
1
[Fe(7)2]Cl2 (21) were formed and characterized by H NMR
spectroscopy. In summary, Zn and Fe proved to be promis-
ing candidates for further investigations of the targeted-as-
sembly concept. In addition, the mono-coordinated platinu-
m(II) complexes [Pt(1)Cl]Cl (22) and [Pt(7)Cl]Cl (23) could
also be isolated by treating one equivalent of the ligand
1
The H NMR spectra of ligand 7 and its ZnII, RuII, and FeII
complexes are depicted in Figure 2. Although the tpy signals
are broadened on complexation (especially for the Zn com-
plex), all peaks could be as-
signed unambiguously by 2D
NMR techniques and compari-
son with related literature
data.[24,25] All coordination
shifts of the metal complexes
are summarized in Tables 1
and 2.
with [PtACHTUNGTRENNUNG(DMSO)4]Cl2.
The signal shifts of both li-
gands are very similar. As ex-
pected,[26] the H6A and H3B pro-
tons are most sensitive to com-
plex formation. The resonance
of the H3B signal is distinctly
shifted downfield by the pres-
ence of the metal center [Dd=
0.50 ppm for ZnII to 1.09 ppm
for FeII (as chloride)]. Even
more noticeable are the ob-
served upfield shifts for the
H6A protons, ranging between
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Self-Assembly of Supramolecular Architectures and Polymers
FULL PAPER
Figure 2. Parts of the 1H NMR spectra (300 MHz, [D6]DMSO). a) Uncoordinated ligand 7. b) [Zn(7)2]
(19). e) [Fe(7)2]Cl2 (21).
ACHTGNUNERT(NUNG OTf)2 (17). c) [Ru(7)2]AHCTUNREGTNNG(UN PF6)2 (15). d) [Fe(7)2]ACHTUNGTRENNUNG(PF6)2
Table 1. Coordination shifts[a] [ppm] of ligand 1.
0.82 ppm for Zn to 1.25 ppm (Ru) and 1.54 ppm (Fe). The
H5A protons are also slightly upfield shifted. The main
tpy
[ZnL2]
R
E
E
G
A
R
ACHTUNGTRENUN[G PtLCl]Cl
proton (16)
(22)
reason for this characteristic upfield shift in MACTHUNRGTNEUNG(tpy)2 struc-
tures is the position of the H6A protons in the complex: the
H6A (and, to a lesser extent, the H5A) protons of one ligand
are shielded by the adjacent tpy unit. The p electrons of the
central pyridine ring cause areas of shielding and deshield-
ing around the ring, and due to the octahedral structure of
the homoleptic complexes, the terminal pyridine units of
one ligand are located in the shielding cone of the second
tpy ligand. Therefore, mono- and disubstituted metal com-
plexes of diamagnetic first-row transition metals can be dis-
tinguished by 1H NMR spctroscopy.[27] The measured data
clearly prove formation of homoleptic bis-tpy complexes
with ZnII, RuII, and FeII. The observed shifts increase from
ZnII to RuII to FeII, which is very likely a result of the differ-
ent bond lengths. The average metal–nitrogen bond length
3B
3A
4A
5A
6A
0.51
0.30
0.28
0.00
ꢀ0.79
0.61
0.30
0.06
0.77
0.28
0.03
1.03
0.36
0.01
0.26
0.13
0.47
0.00
0.03
ꢀ0.07
ꢀ0.30
ꢀ0.34
ꢀ1.23
ꢀ1.53
ꢀ1.50
[a] Dd=dcomplexꢀdligand (300 MHz, [D6]DMSO).
Table 2. Coordination shifts[a] [ppm] of ligand 7.
tpy
[ZnL2]
(OTf)2
G
N
G
N
N
ACHTUNGTRENUNG
proton (17)
3B
3A
4A
5A
6A
0.50
0.25
0.24
0.05
ꢀ0.82
0.60
0.23
0.02
0.85
1.09
0.20
0.23
ꢀ0.01
ꢀ0.35
ꢀ1.54
0.35
ꢀ0.04
ꢀ0.38
ꢀ1.54
ꢀ0.08
0.30
ꢀ0.25
0.26
ꢀ0.25
in MII
(tpy2) complexes decreases from ZnII to RuII to
ACHTUNGTRENNUNG
ꢀ1.25
[a] Dd=dcomplexꢀdligand (300 MHz, [D6]DMSO).
FeII,[24,27,28] and this leads to a stronger shielding effect. In
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9481

A. Hirsch et al.
the case of platinum(II), which is known to form complexes
of the type [Pt
(tpy)X]+,[29] the situation is different: all tpy
ACHTUNGTRENNUNG
protons are slightly shifted downfield on coordination of 1.
For ligand 7, the H3A and H6A signals are shifted downfield
by 0.08 ppm and 0.25 ppm, but the observed coordination
shifts are less pronounced than is the case for M
tures.
ACHTUNGRTENUN(NG tpy)2 struc-
1H NMR titrations of the obtained metal complexes
reveal their ability to form supramolecular architectures
such as 24 with suitable end caps like 8 in CDCl3 by hydro-
gen bonding.
The association constant for the mono-coordinated
[Pt(7)Cl]Cl (23) was determined to be 4.5ꢃ103 Lmolꢀ1 and
resembles the complexation behavior of the free ligand 7.
The development of the NH shifts of the [M(7)2]2+ struc-
tures during titration are shown in Figure 3, and the corre-
sponding complexation constants of the bis-complexes are
listed in Table 3.
1
Figure 3. a) NH shifts in H NMR spectra (300 MHz, CDCl3) of [M(7)2]2+
on titration with end cap 8.
Table 3. Stepwise formation constants of [M(7)n] upon complexation
with end cap 8.
Complex [Zn(7)2]CATHGNURTEN(NNGU OTf)2 [Ru(7)2]AHCNUTGTREGN(NNU PF6)2 [Fe(7)2]ACHTNGUTREN(GUNN PF6)2 [Pt(7)]Cl2
To illustrate these data, the resulting species distribution
is depicted in Figure 4 for the iron complex. For a stoichio-
metric mixture with two equivalents of 8, more than 95% of
the metal complex exists as discrete {[Fe(7)22+](8)2} struc-
ture 24. Less than 5% exists as mono-coordinated species
{[Fe(7)22+](8)}, and when a slight excess of end cap is added,
complexation of the Hamilton receptors is complete.
In the case of iron(II) and zinc(II) as central metal ions,
the supramolecular target structures are even accessible by
spontaneous self-assembly of the isolated parent building
blocks (Scheme 1). For this purpose, the corresponding
metal salt, orthogonal building block 1 or 7, respectively,
and end cap 8 were mixed in chloroform with a few drops of
methanol to provide solubility of the metal salt. After stir-
ring at room temperature for 8 h, the solvent was removed
and the residue redissolved in CDCl3. The recorded
1H NMR spectra are identical with those obtained from the
stepwise-assembled architectures described above. Again,
hydrogen bonding of the end caps at the termini provides
high solubility of the supramolecular complexes in chloro-
(17)
(15)
(19)
(23)
lgK1
lgK2
3.92
2.30
3.90
2.53
3.88
2.64
3.65
–
Figure 4. Species distribution for titration of 19 with end cap 8 in di-
chloromethane.
2+
form, even for the M(1)2 complexes, which are intrinsical-
ly insoluble without end caps.
UV/Vis titrations to follow the metal-ligand assembly pro-
cess were carried out by stepwise addition of ZnACTHUNRGTNEUNG(OTf)2 or
pounds in acetonitrile are shown in Figure 5. Up to
0.5 equiv of Zn (solid lines), a clear isosbestic point at
319 nm indicates that there is only one equilibrium between
two species, presumably free ligand and Zn(7)22+. However,
at Zn/tpy ratios above 1/2, the absorbance suddenly changes
and a new isosbestic point at 346 nm emerges. This indicates
FeCl2 (62.5 mm in acetonitrile and methanol, respectively) to
2+
a 0.031 mm solution of ligand 7. The resulting M(7)2 com-
plexes were expected to form quickly even at room temper-
ature, and the spectra were recorded 10 min after each addi-
tion, as no further changes in the electronic absorption were
observable beyond this time. The spectra of the ZnII com-
2+
reversible formation of Zn(7)2 and involvement of a new
2+
equilibrium, apparently between Zn(7)2 and Zn(7)2+
.
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Self-Assembly of Supramolecular Architectures and Polymers
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The complex formation constants in chloroform were cal-
culated with HypSpec to be lgb1 =7.8 and lgb2 =16.9. Thus,
the stepwise association constant lgK2 is 9.1 for coordina-
tion of a second tpy ligand and therefore higher than the
constant of the first complexation step. Hence, formation of
bis-complex Fe(7)22+is favored even if the Fe/7 ratio is
higher than 0.5. The resulting species distribution is shown
in Figure 7. At an Fe/tpy molar ratio of 0.5, more than 99%
Figure 5. UV/Vis titration of ligand 7 with ZnACTHNUTRGNEU(GN OTf)2 (acetonitrile). a) Ti-
tration data; solid lines: 0.0 to 0.5 equiv; dotted lines: 0.6 to 2.0 equiv.
b) Absorbance at 343 nm.
The ZnII titration spectra show no absorbance at wave-
lengths higher than 400 nm, in contrast to the titration
bands of FeII (Figure 6). The resulting purple complex shows
Figure 7. Species distribution of 7 for titration with Fe2+ in chloroform.
of the ligand is present as 2:1 complex Fe(7)22+. Similar
values were determined for the coordination of iron by pris-
tine building block 1 in methanol (MLCT band at 571 nm;
lgb1 =8.9 and lgb2 =21.1; >99% of 1 as Fe(1)2 for nACHTUNGTRENNUNG
(Fe2+)/
n(1)=1/2), proving the suitability of the prepared building
blocks for the generation of supramolecular architectures.
After successfully generating the desired metal–ligand
motif in a two-component mixture, the ability to coordinate
to Fe in the presence of a hydrogen-bound counterpart was
examined. If the hydrogen-bonding site of orthogonal build-
ing block 7 is coordinated with two-headed bis-cyanurate 9,
supramolecular polymer 25 should be formed. Therefore, a
2:1 mixture of 7 and 9 (0.031 mm and 0.016 mm, respective-
ly) in chloroform was titrated with a methanolic solution of
FeCl2 (62.5 mm) in the manner described above. The result-
ing titration curves resemble the plots depicted in Figure 7.
The maximum of the MLCT band at 568 nm is reached at
an Fe/7/9 ratio of 1/2/1, and again no significant change is
observable for higher molar ratios (Figure 8a). Also, the Job
plot analysis (Figure 8b ) verifies the formation of a stable
1:2 complex stoichiometry between FeII and tpy derivative
7, which is unaffected by the presence of orthogonal hydro-
gen bonds to 9.
Figure 6. UV/Vis titration of ligand 7 with FeCl2 (chloroform). a) Titra-
tion data. b) Development of MLCT band at 568 nm. c) Job plot.
a distinct metal to ligand charge transfer (MLCT) band at
568 nm in chloroform. After the maximum absorbance is
reached at an Fe/7 molar ratio of 0.5, no significant change
of the absorption band is observed after overtitration. The
stoichiometry of the iron complex was confirmed by Jobꢄs
method of continuous variation.[30] The resulting triangular
Job plot (Figure 6c) confirms formation of a single, stable
2:1 complex which is not appreciably dissociated.
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A. Hirsch et al.
mation of the 1:1 ligand:metal complex. The molecular
weight and viscosity rapidly decrease even for metal ions
with a high degree of cooperativity. Addition of FeCl2 to a
solution containing just receptor 7, on the other hand, re-
sults only in a small change of viscosity (Figure 9, dotted
line).
The dynamic behavior of the polymer can be demonstrat-
ed by addition of a monotopic end cap. Minute quantities of
8 (0.1% relative to 7) result in a sharp decline in viscosity
(Figure 10), because end capping of the cyanuric acid moiet-
ies leads to instant shortening of the supramolecular poly-
mer strands.
Figure 8. a) Absorption changes of a 2/1 mixture of 7 and 9 at 586 nm on
addition of Fe2+. b) Job plot of the UV data.
Formation of a supramolecular polymer like 25 is expect-
ed to be accompanied by changes in viscosity after self-as-
sembly. Solutions of the polymer in chloroform show gel-
like behavior after standing for several hours. Formation of
large polymeric aggregates can also be attested to by dy-
namic light scattering (DLS):
A solution containing
[Fe(7)2]Cl2 (21) and homoditopic building block 26 in a
molar ratio of 1/1 shows two processes. One corresponds to
particles with a hydrodynamic radius of RH =45 nm and one
to RH ꢁ5 mm (1–8 mm). As the large particles of several mi-
crometers in size rebuild after removal through filtration
and can not be separated, both species are formed in equi-
librium. For the sole components, only particle sizes of less
than1 nm can be detected.
Stepwise addition of FeCl2 to a 2/1 mixture of building
blocks 7 and 9 in chloroform leads to increasing viscosity
(Figure 9, solid line). A plateau is reached at an Fe2+/7/9
molar ratio of 1/2/1 and indicates formation of polymeric
species. Further addition of metal beyond the stoichiometric
point considerably decreases viscosity. Calculations show
that only 5% of 1:1 complex Fe(7) is formed after addition
of 0.6 equiv of FeCl2, whereas 95% of ligand 7 still exists as
ML2 species. However, Monte Carlo simulations and analyt-
ical modeling[31] of supramolecular polymer formation by
tpy–metal complexation verify that effective depolymeriza-
tion occurs above the stoichiometric composition due to for-
Figure 10. Changes in viscosity of supramolecular polymer 25 on addition
of end cap 8.
Characteristic of supramolecular interactions is their re-
versibility, because noncovalent bonds are usually weaker
than covalent bonds and therefore can be opened under
much milder conditions. Various investigations of the com-
plexation and decomplexation behavior of M
ACHTUNGRTEN(NUNG tpy)2 architec-
tures have been reported. Either metal-complexing ligands
such
as
hydroxyethylethylenediaminetriacetic
acid
(HEEDTA)[32] or variations of the pH value[33–34] can be
used in most cases to cleave the coordinative bonds in tpy
complexes. We found that in the case of Fe(7)22+, addition
of one equivalent of 1,8-diazabicycloACTHNUTRGNEUNG[5.4.0]undec-7-ene
(DBU) in chloroform is sufficient for complete decomplexa-
tion within 12 h at room temperature. The MLCT band at
568 nm is no longer observable (Figure 11).
Neutralization of the alkaline solution with one equiva-
lent of formic acid completely restores the MLCT band.
Larger amounts of DBU increase the rate of decomplexa-
tion (up to a few minutes in the case of 100 equiv), and the
process remains fully reversible. Changing the pH value
allows the equilibrium between free and assembled struc-
tures to be shifted and can therefore be used to “switch” be-
tween uncoordinated single components and highly ordered
1
architectures. As the H NMR signals of the NH group are
Figure 9. Viscosity titration of a 2/1 mixture of 7 and 9 (solid line) with
FeCl2 (in chloroform).
no longer detectable after addition of base/acid (fast proton
9484
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 9478 – 9488

Self-Assembly of Supramolecular Architectures and Polymers
FULL PAPER
tives are highly specific and almost exhaustively occupied
under stoichiometric conditions, making them ideal candi-
dates for generation of supramolecular architectures. By
changing the terminal end caps to a homoditopic bis-cyanu-
rate such as 9, metal-containing supramolecular polymer 25
is formed. The Fe polymer was not only examined by spec-
troscopic methods, but also by viscosity titrations. Supra-
molecular strands with high viscosity are formed in a 1/2/1
mixture of FeII, 1, and 9. Addition of small amounts of 8
leads to a sharp decline in viscosity because the strands are
broken due to the binding of the end cap. This competitive
complexation between the cyanuric acid derivatives demon-
strates the dynamic behavior of the system. The intermolec-
ular architectures can be disassembled by changing the pH
value of the solution. Addition of base (DBU) leads to com-
plete decomplexation of FeII. The metal–ligand coordina-
tion, however, is fully reversible, and neutralization restores
the original MLCT band of the complex. This allows the
equilibrium between the free building blocks and assembled
structures to be controlled. Furthermore, demetalation by
complexing agents such as HEEDTA facilitates recovery of
the parent disassembled building blocks or transformation
into other supermolecular structures.
2+
Figure 11. Alternating UV/Vis spectra of Fe(7)2 in chloroform. 1) Pris-
tine complex (dashed line). 2) After addition of 1 equiv DBU (dotted
line). 3) After neutralization with 1 equiv HCO2H (solid line).
exchange on the timescale of NMR), further experiments
are required to investigate the influence on the hydrogen
bonding arrays.
Addition of HEEDTA (in methanol) to Fe(7)2+ structures
also leads to complete decoloration. The uncoordinated
building block 7 can be recovered by precipitation with di-
ethyl ether. The recovery of the original structure was veri-
1
fied, for example, by H NMR spectroscopy. Further addi-
tion of metal salt allows for regeneration of the pristine
metal complex, or even conversion to a different metal spe-
cies if another metal is added. This opens the possibility to
disassemble superstructures and to recover the parent build-
ing block or to transform them into other supramolecular ar-
chitectures.
Experimental Section
General: All chemicals were obtained from Sigma-Aldrich and Acros Or-
ganics or prepared according to known literature procedures. 4’-(2-
Furyl)-2,2’:6’,2’’-terpyridine was obtained from 2-acetylpyridine and 2-fur-
[36]
aldehyde as described by Constable et al.[35] Oxidation by KMnO4
leads to 2,2’:6’,2’’-terpyridine-4’-carboxylic acid (2). 5-Amino-N,N’-bis[6-
(3,3-dimethylbutyrylamino)pyridin-2-yl]isophthalamide[5]
(Hamilton
amine 3), 6-aminohexanoic acid methyl ester hydrochloride (4),[37] diethyl
2,5-didodecyloxyterephthalate (11),[20,21] 2,5-didodecyloxyterephthalic
Conclusion
acid (12),[20,21] [Ru(DMSO)4]Cl2,[23] and [Pt(DMSO)2Cl2][38] were prepared
ACTHNUTRGENNUG CAHTUNGTRENNUGN
as described in the literature; syntheses of 1-(6-hydroxyhexyl)-1,3,5-tria-
zine-2,4,6-trione) (13)[19] and di-tert-butyl 4-(3-tert-butoxy-3-oxopropyl)-4-
[6-(2,4,6-trioxo-1,3,5-triazinan-1-yl)hexanamido]heptanedioate (8)[12] were
previously reported by us. HPLC was performed with Varian 940-LC and
The synthesis and complexation behavior of terpyridine-de-
rived building blocks 1 and 7 was presented. Both modules
were designed to form a coordinative metal–ligand bond on
the one hand, and heterocomplementary hydrogen bonds on
the other. Metal complexes of 7 with RuII, ZnII, FeII, and PtII
were isolated and their binding capability with cyanuric acid
derivatives like 8 to form supramolecular architectures was
investigated. The corresponding association constants of
free 7 and the metalated ligand lie between 102 and
104 Lmolꢀ1 in chloroform. Ligand 1 is intrinsically insoluble
in chloroform, but can be solubilized by intermolecular in-
teractions on addition of a complementary cyanuric acid de-
rivative. 1H NMR and UV/Vis experiments revealed that
the orthogonal metal–ligand binding site and the hydrogen
bonding arrays are independent of each other; therefore,
the entire self-assembly processes of three-component
supramolecular architectures can be achieved by simply
mixing the building blocks in a one-pot procedure in the
case of Zn and Fe. Especially FeII constitutes an appropriate
1
a Nucleodur 100 (5 mm, C18 end capped) column by Macherey-Nagel. H
and 13C NMR spectra were recorded on Bruker Avance 300, JEOL JNM
EX 400, JEOL JNM GX 400, and JEOL A 500. IR spectra were record-
ed on Bruker-FT-IR Tensor 27 and Pike Miracle ATR unit. Mass spectra
were measured with a Micromass Lab Spec (FAB) on a Finnigan MAT
900 spectrometer with 3-nitrobenzyl alcohol as matrix or Varian MAT
311A (EI). MALDI-TOF measurements were made with an AXIMA-
CFR plus instrument (Kratos Analytical) or a Shimadzu AXIMA Confi-
dence. Elemental analysis was performed by combustion and gas-chroma-
tographic analysis with an EA 1110 CHNS analyzer (CE Instruments).
UV/Vis spectra were recorded on a Varian CARY 5000 UV/Vis/NIR
spectrophotometer. The association constants were determined from ti-
tration data with the programs HypNMR[39] (1H NMR) and HypSpec[40–41]
(UV/Vis). Viscosity experiments where performed on a Schott AVS 470
viscosimetry system.
5-(2,2’:6’,2’’-Terpyridine-4’-carboxamido)-N,N’-bis[6-(3,3-dimethylbutan-
AHCTUNGTRENGNaUN mido)pyridin-2-yl]isophthalamide (1): 2,2’;6’,2’’-Terpyridine-4’-carboxylic
acid (2, 1.49 g, 5.36 mmol) was suspended in dry THF (300 mL). 1-Ethyl-
3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC, 2.06 g,
10.72 mmol) and Hamilton amine 3 (1.50 g, 2.68 mmol) were added and
the suspension stirred at room temperature for 24 h. After stirring for a
further 48 h at 508C, TLC (dichloromethane/methanol 9/1) indicated full
conversion of the Hamilton amine. Therefore, the clear yellow solution
core for such architectures, because the FeACTHNURGTNEUNG(tpy)2 complexes
are characterized by very high complexation constants (K1 =
6.3ꢃ107 Lmolꢀ1, K2 =1.2ꢃ109 Lmolꢀ1). Both binding mo-
Chem. Eur. J. 2011, 17, 9478 – 9488
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9485

A. Hirsch et al.
was filtered to remove possible undissolved residues and evaporated to
dryness. The residue was taken up in ethyl acetate/water (1/1, 200 mL).
After a few minutes of stirring, the precipitate was collected by filtration,
washed with water and dichloromethane, and dried. Yield 52% (1.15 g)
of 1 as a white solid. 1H NMR (300 MHz, [D6]DMSO): d=1.02 (s, 18H,
CH3), 2.32 (s, 4H, CH2), 7.57 (ddd, J=7.5, 4.8, 1.1 Hz, 2H, H5A), 7.81–
7.89 (m, 6H, Hpyr), 8.07 (td, J=7.8, 1.8 Hz, 2H, H4A), 8.34 (s, 1H, Hphen),
8.67 (s, 2H, Hphen), 8.70 (d, J=7.9 Hz, 2H, H3A), 8.80 (d, J=4.0 Hz, 2H,
H6A), 9.02 (s, 2H, H3B), 10.03 (s, 2H, NH), 10.48 (s, 2H, NH), 11.26 ppm
(s, 1H, NH); 13C NMR (100 MHz, [D6]DMSO): d=30.0 (CH3), 31.3
(CMe3), 49.5 (CH2), 110.6 (CHpyr), 110.9 (CHpyr), 119.2 (CH3B), 121.6
(CH3A), 123.2 (CHphen), 124.0 (CHphen), 125.4 (CH5A), 135.3 (Cqphen), 138.2
(CH4A), 139.9 (Cqphen), 140.7 (CHpyr), 144.6 (Cqpyr/tpy), 150.0 (CH6A), 150.6
(Cqpyr/tpy), 151.1 (Cqpyr/tpy), 155.0 (Cqpyr/tpy), 156.5 (Cqpyr/tpy), 165.7 (CO),
the phases were separated and the aqueous phase was extracted with di-
chloromethane (2ꢃ50 mL). The combined organic layers were washed
with water (2ꢃ30 mL), dried over MgSO4, and evaporated to dryness,
yielding 88% (931 mg) of pale yellow solid. The crude product was puri-
fied by RP-HPLC (Nucleodur C18, MeOH), redissolved in dichlorome-
thane and precipitated by the addition of diethyl ether. Washing with di-
ethyl ether and drying yielded 68% (772 mg) of ligand 7 as white
powder. 1H NMR (300 MHz, [D6]DMSO): d=1.01 (s, 18H, CH3), 1.41
(m, 2H, CH2), 1.60–1.68 (m, 4H, 2ꢃCH2), 2.30 (s, 4H, CH2 tBu), 2.40 (t,
J=7.2 Hz, 2H, CH2CO), 3.32 (m, 2H, CH2N), 7.52 (ddd, J=7.4, 4.9,
0.9 Hz, 2H, H5A), 7.75–7.87 (m, 6H, Hpyr), 8.03 (td, J=7.8, 1.8 Hz, 2H,
H4A), 8.18 (t, J=1.1 Hz, 1H, Hphen), 8.37 (d, J=1.1 Hz, 2H, Hphen), 8.64
(d, J=7.9 Hz, 2H, H3A), 8.75 (dd, J=3.9, 0.9 Hz, 2H, H6A), 8.82 (s, 2H,
H3B), 9.15 (br, 1H, NH), 10.04 (s, 2H, NH), 10.35 (br, 1H, NH),
10.40 ppm (s, 2H, NH); 13C NMR (100 MHz, [D6]DMSO): d=24.7
(CH2), 26.1 (CH2), 28.7 (CH2), 29.6 (CH3), 30.9 (CMe3), 36.3 (CH2), 39.2
(CH2), 49.1 (CH2CMe3), 110.1 (CHpyr), 110.5 (CHpyr), 118.4 (CH3B), 121.1
(CH3A), 121.5 (CHphen), 121.8 (CHphen), 124.8 (CH5A), 134.8 (Cqphen), 137.6
(CH4A), 140.0 (Cqphen), 140.2 (CHpyr), 144.4 (Cqpyr/tpy), 149.5, (CH6A), 150.2
(Cqpyr/tpy), 150.7 (Cqpyr/tpy), 154.8 (Cqpyr/tpy), 155.8 (Cqpyr/tpy), 164.7 (CO),
166.2 (CO), 171.5 ppm (CO); MS (MALDI, 2,5-dihydroxybenzoic acid
+
~
(DHB)): m/z: 819 [M+H] ; IR (ATR): n=415, 558, 616, 747, 795, 1241,
1303, 1446, 1153, 1587, 1667 cmꢀ1; elemental analysis calcd (%) for
C46H46N10O5: C 67.47, H 5.66, N 17.10; found: C 67.43, H 5.73, N 17.15.
6-(2,2’:6’,2’’-Terpyridine-4’-carboxamido)hexanoic acid methyl ester (5):
Terpyridine carboxylic acid 2 (2.56 g, 9.23 mmol) was completely dis-
solved in dry DMF (250 mL) under vigorous stirring in an ultrasonic
bath. 6-Aminohexanoic acid methyl ester hydrochloride (1.68 g,
9.23 mmol) was added and the resulting suspension was cooled to 08C.
After addition of EDC (3.54 g, 18.46 mmol), the reaction mixture was
stirred at room temperature for 12 h and at 508C for an additional 8 h.
The resulting clear yellow solution was filtered to remove possible insolu-
ble materials and the solvent evaporated. The residue was taken up in
ethyl acetate/water/saturated aqueous NaHCO3 solution (2/1/1, 200 mL).
The aqueous phase was separated and extracted twice with ethyl acetate
(50 mL). The combined organic extracts were washed with water (3ꢃ
20 mL), dried over MgSO4, and concentrated in vacuo. The product was
precipitated by addition of petroleum ether as a white solid. Yield: 2.72 g
(73%); 1H NMR (300 MHz, [D6]DMSO): d=1.35 (m, 2H, CH2), 1.58
(m, 4H, 2ꢃCH2), 2.32 (t, J=7.1 Hz, 2H, CH2CO), 3.32 (m, 2H, CH2N),
3.57 (s, 3H, CH3), 7.54 (ddd, J=7.5, 4.7, 1.1 Hz, 2H, H5A), 8.04 (td, J=
7.8, 1.8 Hz, 2H, H4A), 8.65 (d, J=7.8 Hz, 2H, H3A), 8.77 (dd, J=4.4,
1.4 Hz, 2H, H6A), 8.82 (s, 2H, H3B), 9.08 ppm (s, 1H, NH); 13C NMR
(100 MHz, [D6]DMSO): d=24.1, 25.9, 28.5, 33.2, 39.2, 51.13, 118.4, 121.0,
165.3 (CO), 171.1 (CO), 172.0 ppm (CO); MS (MALDI, DHB): m/z: 955
+
~
[M+Na] ; IR (ATR): n=409, 560, 574, 609, 671, 734, 797, 1239, 1296,
1415, 1525, 1584, 1670 cmꢀ1
; elemental analysis calcd (%) for
C52H57N11O6: C 67.01, H 6.16, N 16.53; found: C 67.06, H 6.19, N 16.60.
2’,5’-(Didodecyloxy)-O1,O4-[(2,4,6-trioxo-1,3,5-triazin-1-yl)hexyl] tereph-
thalate (9): A suspension of 2,5-(didodecyloxy)terephthalic acid (93 mg,
0.173 mmol,
1.0 equiv),
1-(6-hydroxyhexyl)-1,3,5-triazin-2,4,6-trione
(79 mg, 0.347 mmol, 2.0 equiv), DMAP (42 mg, 0.347 mmol, 2.0 equiv),
HOBt (46 mg, 0.347 mmol, 2.0 equiv), and DCC (72 mg, 0.347 mmol,
2.0 equiv) in dry DMF (6 mL) was heated to 508C. The mixture was
stirred under these conditions for seven days. The solvent was removed
under reduced pressure; the crude product was suspended in CHCl3 and
filtered. The filtrate was concentrated to a small volume and purified re-
peatedly by column chromatography (silica gel, CHCl3, gradient CHCl3/
MeOH 99/1 to 98/2). Compound 9 was obtained as a colorless solid.
Yield: 95 mg (57%). 1H NMR (300 MHz, [D6]DMSO): d=0.86 (t, 3J=
7.08 Hz, 6H, CH3), 1.30–1.24 (m, 36H, CH2), 1.48–1.36 (m, 8H, CH2),
1.67–1.60 (m, 4H, CH2), 1.79–1.72 (m, 8H, CH2), CH2), 3.83 (br, 4H,
CH2N), 3.99 (t, 3J=6.35 Hz, 4H, OCH2), 4.30 (t, 3J=5.37 Hz, 4H,
COOCH2), 7.34 (s, 2H, CHar), 9.86 ppm (s, 4H, NH); 13C NMR
(100 MHz, [D6]DMSO): d=13.99 (2C, CH3), 22.56 (2C, CH2), 25.85 (2C,
CH2), 28.44, 27.67, 26.09, 25.70 (8C, CH2), 29.57, 29.54, 29.30, 29.24,
29.16 (14C, CH2), 31.80 (2C, CH2), 41.72 (2C, CH2N), 65.02 (2C,
COOCH2), 69.79 (2C, CH2O), 116.60 (2C, CHar), 124.64 (2C, Cq), 148.74
(2C, COCy), 149.45 (4C, COCy), 151.73 (2C, Cqchain), 166.30 ppm (2C,
CO); MS (MALDI, trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenyli-
124.9, 137.6, 144.4, 149.6, 154.8, 155.8, 164.7, 173.5 ppm; MS (FAB): m/z:
+
~
405 [M+H] ; IR (ATR): n=447, 669, 731, 764, 1176, 1466, 1551, 1586,
1753 cmꢀ1; elemental analysis calcd (%) for C23H24N4O3: C 68.30, H 5.79,
N 13.80; found: C 68.26, H 5.89, N 13.87.
6-(2,2’:6’,2’’-Terpyridine-4’-carboxamido)hexanoic acid (6): Compound 5
(400 mg, 0.989 mmol) was suspended in 1m NaOH (70 mL) and the reac-
tion mixture stirred for 14 h at room temperature. The resulting clear so-
lution was filtered to remove unconsumed starting material and the pH
adjusted to 5 by addition of concentrated HCl. The precipitate was col-
lected by filtration, washed with water, and dried in vacuo to give the
free acid as white powder. Yield: 307 mg (80%); 1H NMR (300 MHz,
[D6]DMSO): d=1.36 (m, 2H, CH2), 1.56 (m, 4H, 2ꢃCH2), 2.23 (t, J=
7.4 Hz, 2H, CH2CO), 3.32 (m, 2H, CH2N), 7.54 (ddd, J=7.5, 4.8, 1.1 Hz,
2H, H5A), 8.04 (td, J=7.7, 1.9 Hz, 2H, H4A), 8.65 (d, J=7.9 Hz, 2H,
H3A), 8.76 (dd, J=4.2, 1.3 Hz, 2H, H6A), 8.82 (s, 2H, H3B), 9.10 (s, 1H,
NH), 12.0 ppm (br, 1H, CO2H); 13C NMR (100 MHz, [D6]DMSO): d=
24.2, 26.1, 28.7, 33.6, 39.2, 118.3, 121.0, 124.7, 137.6, 144.3, 149.3, 154.6,
dene]malononitrile (DCTB)): m/z 958 [M++H]+, 980 [M+Na]+, 996
+
~
[M+K] ; IR (ATR): n=726, 762, 787, 971, 1054, 1121, 1204, 1229, 1301,
1377, 1416, 1459, 1679, 1745, 2852, 2922, 3066, 3208 cmꢀ1; elemental anal-
ysis calcd (%) for C50H80N6O12: C 62.74, H 8.42, N 8.78; found: C 62.86,
H 8.67, N 8.82.
[Ru(1)2]ACHTUNGRTNENUG(PF6)2 (14): [RuCAHUTGNTREN(NUGN DMSO)4]Cl2 (148 mg, 305 mmol) and ligand 1
(750 mg, 916 mmol) were dissolved in dry chloroform under nitrogen at-
mosphere, and the reaction mixture was heated to reflux for seven days.
After cooling to room temperature and filtration, AgPF6 (463 mg,
1.83 mmol) was added to the liquid and the mixture was stirred for 12 h
until the solution was almost colorless. The reddish brown precipitate
was collected and separated by column chromatography (silica, dichloro-
methane/methanol gradient 99/1 to 95/5, Rf =0.7). Recrystallization from
methanol/dichloromethane yielded the pure complex in 4% yield
155.6, 164.5, 174.5 ppm; MS (MALDI, no matrix): m/z: 391 [M+H]+, 413
+
~
[M+Na] ; IR (ATR): n=618, 657, 671, 794, 1182, 1265, 1368, 1551, 1655,
1722, 3357 cmꢀ1; elemental analysis calcd (%) for C22H22N4O3: C 67.68, H
5.68, N 14.35; found: C 67.52, H 5.75, N 14.40.
1
5-[6-(2,2’:6’,2’’-Terpyridine-4’-carboxamido)hexanamido]-N,N’-bis[6-(3,3-
(56 mg). H NMR (300 MHz, [D6]DMSO): d=1.04 (s, 36H, CH3), 2.34 (s,
8H, CH2), 7.35 (m, 4H, H5A), 7.57 (d, J=5.1 Hz, 4H, H6A), 7.86–7.91 (m,
12H, Hpyr), 8.13 (t, J=7.9 Hz, 4H, H4A), 8.50 (s, 2H, Hphen), 8.77 (s, 4H,
Hphen), 9.00 (d, J=7.9 Hz, 4 H3A), 9.63 (s, 4 H3B), 9.98 (s, 4H, NH), 10.55
(s, 4H, NH), 11.39 ppm (s, 2H, NH); MS (MALDI, DCTB): m/z 1884
dimethylbutanamido)pyridin-2-yl]isophthalamide (7): Compound
6
(1.11 g, 2.84 mmol) was completely dissolved in dry THF (400 mL) under
vigorous stirring in an ultrasonic bath. EDC (1.09 g, 5.76 mmol) and
Hamilton amine 3 (635 mg, 1.135 mmol) were added to the solution, and
the reaction mixture was stirred at 508C for 14 h. The resulting clear
yellow solution was filtered to remove possible residues and the solvent
removed under reduced pressure. The residue was taken up in dichloro-
methane (200 mL) and 1m NaOH (50 mL). After 1 h of vigorous stirring,
[Ru(1)2ACHTUNGTRNEUNG
(PF6)]+; UV/Vis (acetonitrile): lmax =303 nm, 483 nm; IR (ATR):
n=419, 468, 535, 556, 697, 757, 840, 1239, 1445, 1548, 1675 cmꢀ1; elemen-
tal analysis calcd (%) for C92H92F12N20O10P2Ru: C 54.46, H, 4.57, N 13.81;
found: C 54.24, H 4.68, N 13.77.
~
9486
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 9478 – 9488

Self-Assembly of Supramolecular Architectures and Polymers
FULL PAPER
[Ru(7)2]
(PF6)2 (15): Ligand 7 (186 mg, 200 mmol) and ruthenium chloride
elemental analysis calcd (%) for C106H114F6N22O18S2Zn: C 57.15, H 5.16,
N 13.83; found: C 57.27, H 5.22, N 13.93.
hydrate (26 mg, 100 mmol) were suspended in dry methanol under nitro-
gen atmosphere (25 mL). After addition of a few drops of 4-ethylmor-
pholine, the mixture was heated to reflux for seven days. Ammonium
hexafluorophosphate (1.304 g, 8.00 mmol) was added to the resulting
dark mixture at room temperature and stirring was continued for an ad-
ditional 12 h. Subsequently, the solvent was removed and the desired red-
brown complex was isolated by column chromatography (silica, acetoni-
trile/water/sat. KNO3 (aq) 36/3/1). The eluents were removed under re-
duced pressure, and the residue extracted with MeOH (3ꢃ10 mL). After
addition of another portion of NH4PF6 (163 mg, 1.00 mmol), the com-
bined methanolic solutions were evaporated to dryness. Purification by
size exclusion chromatography (bio-beads s-x1, THF) yielded pure
[Fe(1)2]ACHTUNGRTNEUNG(PF6)2 (18): Under nitrogen atmosphere, FeCl2 (12.6 mg,
100 mmol) and ligand 1 (164 mg, 200 mmol) were dissolved in absolute
MeOH (30 mL). The resulting dark purple reaction mixture was stirred
at room temperature for two days. The chloride salt precipitated on con-
centrating the solution to a small volume. The purple microcrystals were
filtered off, washed with diethyl ether, and dried in vacuo, resulting in
chloride complex 20. Yield: 98% (173 mg) of purple powder. 1H NMR
(300 MHz, [D6]DMSO): d=1.04 (s, 36H, CH3), 2.34 (s, 8H, CH2), 7.23
(m, 4H, H5A), 7. 30 (d, J=4.9 Hz, 4H, H6A), 7.89 (m, 12H, Hpyr), 8.08 (t,
J=7.8, 4H, H4A), 8.47 (s, 2H, Hphen), 8.89 (s, 4H, Hphen), 9.06 (d, J=
8.2 Hz, 4H, H3A), 10.03 (s, 4H, NH), 10.05 (s, 4H, H3B), 10.57 (s, 4H,
NH), 12.00 ppm (s, 2H, NH). For complete characterization, the complex
was converted to the PF6 salt. NH4PF6 (700 mg, 4.29 mmol) was added to
the solution and the mixture stirred at room temperature for 14 h. The
precipitate was collected by filtration, washed with methanol and diethyl
ether, and dried. Yield: 94% (186 mg) of purple powder. 1H NMR
(300 MHz, [D6]DMSO): d=1.04 (s, 36H, CH3), 2.34 (s, 8H, CH2), 7.27
(m, 8H, H5A, H6A), 7.89 (m, 12H, Hpyr), 8.10 (t, J=7.8, 4H, H4A), 8.48 (s,
2H, Hphen), 8.81 (s, 4H, Hphen), 8.98 (d, J=8.2 Hz, 4H, H3A), 9.79 (s, 4H,
H3B), 10.00 (s, 4H, NH), 10.59 (s, 4H, NH), 11.53 ppm (s, 2H, NH);
13C NMR (100 MHz, [D6]DMSO): d=29.6 (CH3), 30.9 (CMe3), 49.2
(CH2), 110.2 (CHpyr), 110.5 (CHpyr), 117.8 (CH3B), 122.4 (CH3A), 123.9
(CHphen), 124.6 (CHphen), 128.0 (CH5A), 135.0 (Cqphen), 139.2 (CH4A), 139.5
(Cqphen), 140.3 (CHpyr), 142.7 (Cqpyr/tpy), 150.2 (CH6A), 150.7 (Cqpyr/tpy), 151.1
(Cqpyr/tpy), 152.9 (Cqpyr/tpy), 157.5 (Cqpyr/tpy), 160.2 (CO), 165.3 (CO),
[Ru(7)2]ACHTUNGTRENNUNG
(PF6)2 in 6% yield (25 mg). 1H NMR (300 MHz, [D6]DMSO):
d=1.02 (s, 36H, CH3), 1.22 (m, 4H, CH2), 1.57–1.79 (m, 8H, 2ꢃCH2),
2.30 (s, 8H, CH2 tBu), 2.45 (t, J=7.1 Hz, 4H, CH2CO), 3.32 (m, 4H,
CH2N), 7.26 (m, 4H, H5A), 7.50 (d, J=5.2 Hz, 4H, H6A), 7.75–7.86 (m,
12H, Hpyr), 8.05 (t, J=8.0 Hz, 4H, H4A), 8.23 (s, 2H, Hphen), 8.37 (s, 4H,
Hphen), 8.87 (d, J=8.1 Hz, 4 H3A), 9.23 (br, 2H, NH), 9.42 (s, 4 H3B), 9.97
(s, 4H, NH), 10.36 (s, 2H, NH), 10.39 ppm (s, 4H, NH); 13C NMR
(100 MHz, [D6]DMSO): d=24.5 (CH2), 26.3 (CH2), 28.2 (CH2), 29.8
(CH3), 31.1 (CMe3), 36.6 (CH2), 39.2 (CH2), 49.3 (CH2CMe3), 110.5
(CHpyr), 110.6 (CHpyr), 122.1 (CHphen), 122.2 (CH3B), 122.3 (CHphen), 125.3
(CH3A), 128.3 (CH5A), 135.9 (Cqphen), 138.9 (CH4A), 141.3 (Cqphen), 140.7
(CHpyr), 145.6 (Cqpyr/tpy), 150.9 (Cqpyr/tpy), 151.4 (Cqpyr/tpy), 152.9, (CH6A),
155.2 (Cqpyr/tpy), 157.8 (Cqpyr/tpy), 164.9 (CO), 165.5 (CO), 171.3 (CO),
172.0 ppm (CO); MS (MALDI, DCTB): m/z 2110 [Ru(7)2ACTHNUTRGNEUNG
(PF6)]+, 1965
[Ru(7)2ACHTUNGTRENNUNG
(PF6)]2+; UV/Vis (acetonitrile): lmax =304 nm, 486 nm; IR (ATR):
171.1 ppm (CO); MS (MALDI, DCTB): m/z 1839 [Fe(1)
2A
(PF6)]+, 1693
2ACHTUNGTRENNUNG
n=406, 557, 797, 841, 1240, 1296, 1446, 1534 cmꢀ1; elemental analysis
calcd (%) for C104H114F12N22O12P2Ru: C 55.29, H 5.10, N 13.66; found: C
55.49, H 5.21, N 13.60.
[Fe(1)
(PF6)ꢀH]+; UV/Vis (acetonitrile): lmax =305 nm, 571 nm; IR
~
(ATR): n=759, 831, 1238, 1291, 1322, 1443, 1513, 1584, 1673 cmꢀ1; ele-
mental analysis calcd (%) for C92H92F12FeN20O10P2: C 55.71, H, 4.67, N
14.12; found: C 55.64, H 4.59, N 14.00.
~
[Zn(1)2]ACHTUNGTRENNUNG(OTf)2 (16): Under nitrogen atmosphere, zinc(II) triflate
(18.0 mg, 50 mmol) and ligand 1 (82 mg, 100 mmol) were dissolved in dry
acetonitrile (25 mL). The suspension was stirred at room temperature for
2 h and heated to 508C for 10 h. After cooling to room temperature, the
resulting clear yellow solution was filtered, concentrated under reduced
pressure, and the product precipitated by addition of diethyl ether. The
pale yellow powder was collected by filtration, washed with dichlorome-
thane, and dried. Yield 75% (75 mg); 1H NMR (300 MHz, [D6]DMSO):
d=1.04 (s, 36H, CH3), 2.33 (s, 8H, CH2), 7.57 (br, 4H, H5A), 7.88 (m,
12H, Hpyr), 8.01 (br, 4H, H6A), 8.35 (br, 4H, H4A), 8.48 (s, 2H, Hphen),
8.72 (s, 4H, Hphen), 9.00 (br, 4H, H3A), 9.53 (br, 4H, H3B), 9.99 (s, 4H,
[Fe(7)2]ACHTNUGTRENUNG(PF6)2 (19): Under nitrogen atmosphere, FeCl2 (6.80 mg, 54 mmol)
and ligand 7 (100 mg, 107 mmol) were dissolved in absolute MeOH
(30 mL). The resulting dark purple mixture was stirred at room tempera-
ture for two days and filtered. Complete conversion to the homoleptic
complex was confirmed by 1H NMR on chloride salt 21 after removal of
the solvent. Yield: 94% (101 mg) of purple powder. 1H NMR (300 MHz,
[D6]DMSO): d=1.01 (s, 36H, CH3), 1.57 (m, 4H, CH2), 1.80 (m, 8H, 2ꢃ
CH2), 2.30 (s, 8H, CH2 tBu), 2.45 (t, J=7.0 Hz, 4H, CH2CO), 3.60 (m,
4H, CH2N), 7.14 (m, 4H, H5A), 7. 21 (d, J=5.4 Hz, 4H, H6A), 7.72–7.86
(m, 12H, Hpyr), 7.99 (t, J=7.4, 4H, H4A), 8.21 (s, 2H, Hphen), 8.42 (s, 4H,
Hphen), 8.99 (d, J=7.9 Hz, 4H, H3A), 9.91 (s, 4H, H3B), 9.96 (br, 2H, NH),
10.02 (s, 4H, NH), 10.39 (s, 4H, NH), 10.56 ppm (s, 2H, NH). To obtain
the PF6 salt of the complex instead, NH4PF6 (700 mg, 4.29 mmol) was
added to the solution and the mixture stirred at room temperature for
14 h. The precipitate was collected by filtration, washed with methanol
and diethyl ether, and dried. Yield: 92% (110 mg) of purple powder.
1H NMR (300 MHz, [D6]DMSO): d=1.01 (s, 36H, CH3), 1.57 (m, 4H,
CH2), 1.80 (m, 8H, 2ꢃCH2), 2.30 (s, 8H, CH2 tBu 2.45 (t, J=7.0 Hz, 4H,
CH2CO), 3.61 (m, 4H, CH2N), 7.12–7.25 (m, 8H, H5A, H6A), 7.74–7.87
(m, 12H, Hpyr), 8.01 (t, J=7.5, 4H, H4A), 8.22 (s, 2H, Hphen), 8.40 (s, 4H,
Hphen), 8.87 (d, J=7.7 Hz, 4H, H3A), 9.51 (br, 2H, NH), 9.67 (s, 4H, H3B),
10.00 (s, 4H, NH), 10.40 (s, 4H, NH), 10.42 ppm (s, 2H, NH); 13C NMR
(100 MHz, [D6]DMSO): d=24.6 (CH2), 25.9 (CH2), 28.7 (CH2), 29.6
(CH3), 30.9 (CMe3), 36.2 (CH2), 39.5 (CH2), 49.0 (CH2CMe3), 110.3
(CHpyr), 110.6 (CHpyr), 121.6 (CHphen), 121.7 (CH3B), 122.2 (CHphen), 124.3
(CH3A), 127.9 (CH5A), 134.8 (Cqphen), 139.3 (CH4A), 140.2 (Cqphen), 140.3
(CHpyr), 143.3 (Cqpyr/tpy), 150.2, (CH6A), 150.7 (Cqpyr/tpy), 152.9 (Cqpyr/tpy),
157.4 (Cqpyr/tpy), 157.8 (Cqpyr/tpy), 160.1 (CO), 163.5 (CO), 171.1 (CO),
NH), 10.55 (s, 4H, NH), 11.40 ppm (br, 2H, NH); MS (MALDI, DCTB):
+
~
m/z 1719 [Zn(1)2(OH)] ; IR (ATR): n=636, 796, 1029, 1155, 1204, 1282,
1444, 1518, 1583, 1679 cmꢀ1
; elemental analysis calcd (%) for
C94H92F6N20O16S2Zn: C 56.41, H, 4.63, N 14.00; found: C 56.24, H 4.74, N
13.85.
[Zn(7)2]ACHTUNGTRENNUNG(OTf)2 (17): Under nitrogen atmosphere, zinc(II) triflate
(18.0 mg, 50 mmol) and ligand 7 (93 mg, 100 mmol) were dissolved in dry
acetonitrile (25 mL). The suspension was stirred at room temperature for
2 h and heated to 508C for additional 8 h. The resulting clear yellow solu-
tion was filtered, concentrated under reduced pressure, and the product
precipitated by addition of diethyl ether. The pale powder was collected
by filtration, washed with diethyl ether and dried. Yield 70% (78 mg).
1H NMR (300 MHz, [D6]DMSO): d=1.02 (s, 36H, CH3), 1.52 (m, 4H,
CH2), 1.75 (m, 8H, 2ꢃCH2), 2.31 (s, 8H, CH2 tBu), 2.45 (t, J=6.8 Hz,
4H, CH2CO), 3.53 (m, 4H, CH2N), 7.50 (br, 4H, H5A), 7.75–7.87 (m,
12H, Hpyr), 7.93 (m, 4H, H6A), 8.22 (s, 2H, Hphen), 8.27 (br, 4H, H4A),
8.38 (s, 4H, Hphen), 8.89 (br, 4H, H3A), 9.29 (br, 2H, NH), 9.32 (br, 4H,
H3B), 9.97 (s, 4H, NH), 10.34 (s, 2H, NH), 10.36 ppm (s, 4H, NH);
13C NMR (100 MHz, [D6]DMSO): d=24.8 (CH2), 26.2 (CH2), 28.9 (CH2),
29.6 (CH3), 30.9 (CMe3), 36.3 (CH2), 39.5 (CH2), 49.1 (CH2CMe3), 110.1
(CHpyr), 110.4 (CHpyr), 121.5 (CHphen), 121.9 (CHphen), 122.0 (CH3B), 123.6
(CH3A), 128.1 (CH5A), 134.8 (Cqphen), 140.0 (Cqphen), 140.2 (CHpyr), 141.8
(CH4A), 147.3 (Cqpyr/tpy), 148.4, (CH6A), 150.2 (Cqpyr/tpy), 150.7 (Cqpyr/tpy),
154.8 (Cqpyr/tpy), 158.1. (Cqpyr/tpy), 163.2 (CO), 165.3 (CO), 171.1 (CO),
172.0 ppm (CO); MS (MALDI, DCTB): m/z 986 [Fe(7)]2+
,
1919
~
[Fe(7)2]2+; UV/Vis (acetonitrile): lmax =303 nm, 557 nm; IR (ATR): n=
557, 793, 804, 839, 1242, 1299, 1445, 1514, 1584, 1682 cmꢀ1; elemental
analysis calcd (%) for C104H114F12FeN22O12P2: C 56.52, H 5.20, N 13.94;
found: C 56.56, H 5.16, N 13.92.
[Pt(1)Cl]Cl (22): Under a nitrogen atmosphere, [PtACTHUNTRGNEUNG(DMSO)4]Cl2 (42 mg,
100 mmol) and ligand 1 (82 mg, 100 mmol) were dissolved in methanol
(40 mL) and heated at 508C for 12 h. The resulting yellow precipitate
171.9 ppm (CO); MS (MALDI, DCTB): m/z 996 [Zn(7)]2+; IR (ATR):
ꢀ1
~
n=414, 517, 571, 639, 1029, 1157, 1241, 1283, 1445, 1541, 1584, 1669 cm
;
Chem. Eur. J. 2011, 17, 9478 – 9488
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9487

A. Hirsch et al.
was collected by filtration, washed with dichloromethane, and dried.
Yield: 79% (83 mg). 1H NMR (300 MHz, [D6]DMSO): d=1.03 (s, 18H,
CH3), 2.32 (s, 4H, CH2), 7.76 (m, 2H, Hpyr), 7.85 (m, 4H, Hpyr), 7.57 (m,
2H, H5A), 8.36 (s, 1H, Hphen), 8.54 (t, J=8.0 Hz, 2H, H4A), 8.58 (s, 2H,
Hphen), 8.81–8.89 (m, 4H, H3A, H6A), 9.28 (s, 2H, H3B), 9.97 (s, 2H, NH),
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+
~
1050 [PtL2Cl] ; IR (ATR): n=440, 556, 615, 676, 759, 786, 1150, 1234,
1296, 1439, 1517, 1529, 1679 cmꢀ1; elemental analysis calcd (%) for
C46H46Cl2N10O5Pt: C 50.93, H, 4.27, N 12.91; found: C 50.70, H 4.44, N
13.02.
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[Pt(7)Cl]Cl (23): Under nitrogen atmosphere, [PtACTHUNTRGNEUNG(DMSO)4]Cl2 (42 mg,
100 mmol) and ligand 7 (93 mg, 100 mmol) were dissolved in methanol
(40 mL) and heated at 508C for 14 h. The clear yellow solution was con-
centrated to small volume and precipitated by addition of diethyl ether.
The resulting yellow solid was collected by filtration and carefully
washed with chloroform and dried. Yield: 30% (35 mg); 1H NMR
(300 MHz, [D6]DMSO): d=1.02 (s, 18H, CH3), 1.46 (m, 2H, CH2), 1.71
(m, 4H, 2ꢃCH2), 2.32 (s, 4H, CH2 tBu), 2.43 (t, J=7.1 Hz, 2H, CH2CO),
3.36 (m, 2H, CH2N), 7.64 (dd, J=7.4, 1.0 Hz, 2H, Hpyr), 7.73–7.84 (m,
6H, H5A, Hpyr), 8.02 (s, 1H, Hphen), 8.21 (s, 2H, Hphen), 8.33 (t, J=7.9, 2H,
H4A), 8.50 (d, J=5.0 Hz, 2H, H6A), 8.56 (d, J=7.9 Hz, 2H, H3A), 9.02 (s,
2H, H3B), 9.63 (br, 1H, NH), 9.97 (s, 2H, NH), 10.10 (s, 2H, NH),
10.43 ppm (s, 1H, NH); 13C NMR (100 MHz, [D6]DMSO): d=24.5
(CH2), 25.7 (CH2), 28.0 (CH2), 29.6 (CH3), 30.9 (CMe3), 35.9 (CH2), 40.4
(CH2), 49.1 (CH2CMe3), 110.1 (CHpyr), 110.3 (CHpyr), 121.0 (CHphen),
122.0 (CHphen), 122.7 (CH3B), 126.2 (CH3A), 129.4 (CH5A), 134.3 (Cqphen),
139.9 (Cqphen), 140.1 (CHpyr), 142.6 (CH4A), 145.9 (Cqpyr/tpy), 150.0 (Cqpyr/tpy),
150.5 (Cqpyr/tpy), 151.1 (CH6A), 154.3 (Cqpyr/tpy), 157.5 (Cqpyr/tpy), 162.0 (CO),
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~
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1235, 1295, 1445, 1668 cmꢀ1
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Acknowledgements
Financial support from the Collaborative Research Center SFB 583 of
the Deutsche Forschungsgemeinschaft and the Cluster of Excellence
EAM is gratefully acknowledged.
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Received: January 17, 2011
Published online: July 5, 2011
9488
www.chemeurj.org
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 9478 – 9488