Rigid bisphenanthrolines: Synthesis, structure and self-assembly at a solid-liquid interface

Article abstract of DOI:10.1002/ejoc.200600174

Several rigid linear bisphenanthrolines with and without bulky groups at the bisimine sites were synthesized. For three representatives, the solid-state structures were elucidated. Their potential for self-assembled monolayers was explored by scanning tun

Full text of DOI:10.1002/ejoc.200600174

FULL PAPER
DOI: 10.1002/ejoc.200600174
Rigid Bisphenanthrolines: Synthesis, Structure and Self-Assembly at a Solid–
Liquid Interface
Michael Schmittel,*[a] Venkateshwarlu Kalsani,[a][‡] Frank Jäckel,[b][‡‡] Jürgen P. Rabe,[b]
Jan W. Bats,[c] and Dieter Fenske[d]
Dedicated to Prof. Dr. Dr. h.c. mult. S. Hünig on the occasion of his 85th birthday
Keywords: Synthesis / Phenanthrolines / Self-assembly / Solid–liquid interface / X-ray diffraction
Several rigid linear bisphenanthrolines with and without
bulky groups at the bisimine sites were synthesized. For
three representatives, the solid-state structures were eluci-
dated. Their potential for self-assembled monolayers was ex-
plored by scanning tunneling microscopy (STM) at the solid–
liquid interface, and the resulting architectures were found
to be promising candidates for templating metal-ion nano-
patterns.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
which cannot be solved by simply using self-recognition and
positive cooperativity principles.[5] Recently, Schmittel et al.
have proposed two general strategies to engineer hetero-
ligand, metallo-supramolecular structures, using the
HETPHEN[6] (heteroleptic phenanthroline complexes) and
the HETTAP[7] (heteroleptic terpyridine and phenan-
throline complexes) concept. Ligands designed along those
notions will exclusively lead to dynamic heteroleptic aggre-
gation in solution when combined with the appropriate
metal ions.
Introduction
Various self-assembly strategies have paved the way for
the exploration of structural and functional supramolecular
architectures over the past decade.[1,2] Apart from hydrogen
bonding as a directing supramolecular motif, the coordina-
tion driven approach has assumed a particular standing in
the preparation of complex aggregates.[1,2] The latter ap-
proach most often relies on the coordination of transition-
metal cations to multisite ligands, such as polypyridines, for
example in oligomeric strands.
Amid the rigid, multisite ligands, oligo-2,2Ј-bipyridines,
oligo-1,10-phenanthrolines, and oligo-terpyridines are the
most commonly used systems because of their strong coor-
dination by various metal ions and because of their rodlike
shape that allows them to assemble in a predictable fash-
ion.[3,4] While there are numerous grids[2c] amongst the
known supramolecular (dynamic) motifs, racks[4e] and lad-
ders[5] have received much less coverage because of the
problems with their inherent heteroleptic construction,
As both the HETPHEN and HETTAP concept[6,7] criti-
cally depend on the proper fine tuning of steric hindrance
and π–π interactions, the linear bisphenanthrolines[8] must
be equipped with bulky substituents[9] at the bisimine bind-
ing sites. Several oligo-phenanthrolines have already been
prepared earlier[10] and used in the self-assembly of nano-
scale structures such as heteroleptic grids,[4c] racks,[4e] ring-
in-ring structures,[11] and nanobasket,[4d] nanobox,[5b] and
nanoladder motifs.[7] In this paper, we present the synthesis
of several new rigid bisphenanthrolines, some of which have
anthracenyl and alkylaryl[6] groups as steric stoppers, their
structures, and their self-assembly at the solid–liquid inter-
face.
[a] Center of Micro and Nanochemistry and Engineering, Organi-
sche Chemie I, Universität Siegen,
Adolf-Reichwein-Str., 57068 Siegen, Germany,
Fax: +49-271-740-3270
E-mail: schmittel@chemie.uni-siegen.de.
[b] Institut für Physik, Humboldt-Universität zu Berlin,
Newtonstr. 15, 12489 Berlin, Germany
Results and Discussion
[c] Institut für Organische Chemie und Chemische Biologie,
Johann Wolfgang Goethe-Universität,
Synthesis of Bisphenanthrolines 5 and 6
Marie-Curie-Str. 11, D 60439 Frankfurt am Main, Germany
[d] Institut für Anorganische Chemie, Universität Karlsruhe,
Engesserstr. 3045, -76128 Karlsruhe, Germany
[‡] Present address: Department of Chemistry, Tufts University,
Medford, MA 02155, USA
The sterically bulky aryl groups were introduced in the
2- and 9-position of the starting phenanthroline 1a by a
stepwise protocol developed by Sauvage (Scheme 1).[12] The
intermediate addition products were isolated and oxidized
[‡‡] Present address: Department of Chemistry, Stanford Univer-
sity, Stanford, CA 94305, USA
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M. Schmittel, V. Kalsani, F. Jäckel, J. P. Rabe, J. W. Bats, D. Fenske
FULL PAPER
Scheme 1. Synthesis of 3-ethynylphenanthrolines 4a,b as building blocks.
with activated manganese dioxide to afford the diarylated
phenanthrolines 3a,b.[13] Deprotection of 3a,b with aqueous
KOH afforded 4a,b that served as versatile precursors for
the preparation of bisphenanthrolines 5a–c.
Similar to the procedure in a previous report,[10] Pd/Cu-
catalyzed Sonogashira coupling[14] of 4a and 4b with 1,4-
diiodobenzene afforded the corresponding bisphenanthrol-
ines 5a and 5b, respectively, in good to moderate yields
(89% and 31%, see Scheme 2). Homocoupled phenan-
throlines were found in trace amounts even under strin-
gently dry conditions. Hence, for best yields, the reaction
was monitored by ESI-MS spectroscopy. Isolation of pure
5a was readily achieved by column chromatography and
subsequent recrystallization from cyclohexane. 5aЈ was ob-
tained in 95% yield by the deprotection of 5a with Bu4NF
and was isolated after repeated recrystallization from DMF.
The spectra of both 5a and 5aЈ show a broad fluorescence
band extending up to 500 nm with discrete maxima at 391
and 411 nm. All bisphenanthrolines were characterized by
1H- and13C NMR spectroscopy, ESI-MS, UV/Vis spec-
troscopy, and elemental analysis.
In order to realize heteroligand assemblies in combina-
tion with 5a,b, as shown for multi-component grid and rack
Scheme 2. Synthesis of bisphenanthrolines 5a,b by PdCl2(PPh3)2-cata-
lyzed Sonogashira coupling.
Scheme 3. Synthesis of 2,9-unsubstituted bisphenanthrolines 6a–c.
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Rigid Bisphenanthrolines
FULL PAPER
motifs,[4c,4d] access to 2,9-unshielded phenanthroline build-
Suitable single crystals of 6a[17] (Figure 2) and 6b[18] (Fig-
ing blocks is equally warranted.[4c] Grummt and Klemm et ure 3) were obtained by the slow evaporation of a dichloro-
al.[15] have reported on the synthesis of several bisphen- methane solution. The single-crystal structure analysis of
anthrolines, including 6a, and their photophysical proper- 6a provides ample information about intermolecular pack-
ties;[15] however, their self-assembly behavior at the solid– ing as a result of π–π stacking (Ϸ3.5 Å) and parallel align-
liquid interface and in solution had not been explored. Li- ment of the alkyl chains (Figure 2b). In a manner similar
gands 6a–c were synthesized under similar conditions as to that of 5aЈ, this molecule also crystallizes in a cisoid con-
mentioned above through a Sonogashira coupling reaction formation. Ligands 6a and 5aЈ exhibit a length of almost
(Scheme 3).
3 nm (6a: 26.4 Å, 5aЈ: 26.4 Å) along the bisphenanthroline
axis, which might be the reason why it was difficult to ob-
tain suitable quality single crystals for this series of com-
pounds. Intermolecular interactions between dichlorometh-
ane (solvent) and the phenanthroline bisimine site could
also be noticed; however, because of the poor crystal qual-
ity, the role of the solvent was not explored in more detail.
Structures of Bisphenanthrolines 5 and 6
Bisphenanthroline 5aЈ proved to be insoluble in many
solvents [acetone, chlorinated solvents (sparingly soluble),
nitromethane, DMSO, and acetonitrile], while it was solu-
ble in DMF upon heating. When the DMF solution of 5aЈ
was cooled, suitable single crystals for X-ray crystal struc-
ture analysis were obtained (Figure 1).[16] To the best of our
knowledge, 5aЈ is the first single-crystal structure of this
series of rigid bisphenanthrolines.
The stick and space-filling representation of 5aЈ is de-
picted in Figure 1. Surprisingly, this molecule exhibits a
cisoid conformation in the solid state that is most likely
driven by weak intermolecular hydrogen bonding (2.8 Å)
that leads to extended arrays of molecules at the intermo-
lecular level (Figure 1c). An intramolecular hydrogen bond
between the two phenolic OH groups is precluded (O···O
Figure 2. Single-crystal structure of 6a: a) stick representation,
b) solid-state dimer arising from intermolecular π–π stacking
(Ϸ 3.5 Å) between neighboring phenanthrolines.
The single-crystal structure of 6b that shows a transoid
distance: 4.84 Å). From the space-filling representation, the arrangement of the two phenanthroline binding sites is rep-
amount of steric bulk around the phenanthroline binding resented in Figure 3. The molecule is centrosymmetric with
site becomes obvious. It is this shielding that prevents any a crystallographic inversion center at the midpoint of the
homoleptic complex formation even at elevated tempera- central planar benzene ring. The phenanthroline group is
tures.
almost planar, with a mean deviation of 0.021 Å from an
Figure 1. Single-crystal structure of 5aЈ: a) space-filling representation, b) stick representation, c) intermolecular hydrogen bonding (2.8 Å).
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M. Schmittel, V. Kalsani, F. Jäckel, J. P. Rabe, J. W. Bats, D. Fenske
FULL PAPER
Figure 3. Single crystal structure of 6b: a) stick representation, b) intermolecular interactions between the solvent (dichloromethane) and 6b
(N···H Ϸ 2.37–2.52 Å).
ideal plane. The asymmetric unit contains dichloromethane of two bisphenanthrolines (6a and 6c) at the solid–liquid
as solvent. The dichloromethane molecule donates a weak interface. Their self-assembly on surfaces is of special inter-
bifurcated hydrogen bond to the nitrogen atoms N1 and est because of their photophysical properties[28] and their
N2 (Figure 3b). A similar bifurcated interaction involving a potential for the construction of nano-ordered metallo-
chloroform molecule was found in a 1,10-phenanthroline- supramolecular aggregates.[4]
3-ylethynyl compound reported by Lindner et al.[19] The
Figure 4a and b display STM current images of highly
solvent is also involved in six intermolecular C–H···Cl inter- ordered monolayers of 6a,c at the solid–liquid interface be-
actions with H···Cl distances between 2.93 and 3.14 Å. The tween highly oriented pyrolytic graphite (HOPG) and 1,2,4-
crystal packing also shows a number of intermolecular π– trichlorobenzene. The bright areas that correspond to a
π interactions with C···C distances between 3.39 and 3.52 Å high-tunneling probability are attributed to the conjugated,
and a number of weak intermolecular C–H···π(C) interac- rodlike parts of the molecules, since the energy differences
tions.
between their frontier orbitals and the Fermi level of
HOPG are rather small.[29] The two-dimensional arrange-
ments can be described by unit cells with parameters a =
(1.39 0.07) nm, b = (2.83 0.20) nm, and α = (75 4)°,
and a = (2.11 0.10) nm, b = (2.37 0.2) nm, and α =
Self-Assembly of 6 at the Solid–Liquid Interface
In recent years we have witnessed the significance of the (58 2)° for 6a and 6c, respectively. Obviously, the length
self-assembly of organic compounds in the context of nano- of the alkyl chains of the two derivatives drastically influ-
materials and nanotechnology. In particular, nanopattern- ences the molecular arrangement. For the longer O–C12
ing has become one of the major topics in these fields.[20] alkyl chains in 6a, the molecules align with their long mo-
Scanning tunneling microscopy (STM) with its sub-molecu- lecular axis parallel to the long unit cell vector, whose
lar resolution has proven to be a useful technique for the length corresponds well to the length of the rodlike part of
analysis of self-assembled monolayers from organic mole- the molecule, as illustrated in Figure 4c. The 2D-model of
cules at solid–liquid interfaces in terms of their structural such an arrangement (Figure 5), however, requires that the
and electronic properties.[21] Several groups have investi- O–C12 side chains are folded to fill the void between the
gated the patterning of organic molecules and supramolec- parallel rows of bisphenanthrolines. For 6c, rows of stag-
ular aggregates, such as hydrogen-bonded assemblies[22] at gered molecules are observed, as depicted in Figure 4d. The
the solid–liquid interface. Organic molecules possessing co- distances between the molecules within a row and in adja-
ordinating functionalities such as pyridine,[23] bipyridine,[24] cent rows are about 0.6 nm and 1.0 nm, respectively, which
phenanthroline or terpyridine,[25] and bis(salicylidene)s[26] allows the shorter C6 alkyl chain to extend in an all-anti
are of particular interest because of their potential use in conformation. In both cases, the distances between neighb-
preparing metallo-supramolecular aggregates.[4,23]
oring phenanthroline units appear large enough for the in-
Recently, DeSchryver[24] and Schubert[25] have reported sertion and complexation of metal ions. Thus, these mono-
on the surface patterning of bipyridines and terpyridines. layers can be envisaged to serve as templates for the nano-
Ordered monolayers of these metal-coordinating ligands patterning of surfaces with metal ions[30] in which the de-
could potentially act as templates to generate highly or- tails of the nanopatterns can be controlled by appropriately
dered metal surfaces.[25,27] In the following part of the pa- chosen alkyl chains. The realization of such patterns will be
per, we report the formation of highly ordered monolayers the focus of future work.
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Rigid Bisphenanthrolines
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Experimental Section
All reagents were commercially available and used without further
purification. The solvents were dried with appropriate desiccants
and distilled prior to use (CH2Cl2 from P2O5, MeCN from P2O5,
1
and NaH, diethyl ether from sodium). H NMR spectra were re-
corded with Bruker AC 200 (200 MHz) and Bruker AC 400
(400 MHz) spectrometers (using the deuterated solvent as the lock
and residual solvent as the internal reference). IR spectra were re-
corded with a Perkin–Elmer 1605 FT-IR instrument. Microanaly-
ses were carried out with a Carlo Erba Elemental Analyzer 1106.
Electrospray mass spectra (ESI-MS) were recorded using
a
ThermoQuest LCQ Deca. The degree of lithiation was readily
monitored by GC, while progress of the substitution at phenan-
throline was best controlled by ESI-MS. Compound 1 was prepared
according to known procedures.[10] For a complete characterization
of 6a, see ref.[15]
STM at the solid–liquid-interface[31] was performed by using a
home-built beetle-type scanning tunneling microscope, interfaced
with a commercial controller (Omicron). STM tips were prepared
by mechanically cutting a 0.25-mm thick Pt/Ir (80%/20%) wire. A
drop of an almost saturated solution of the bisphenanthrolines in
1,2,4-trichlorobenzene was applied to the basal plane of freshly
cleaved, highly oriented pyrolytic graphite (HOPG). The lattice of
the underlying substrate could be visualized during measurements
by simply changing the tunneling parameters to allow small tunnel-
ing impedance. This allows in-situ x-y calibration of the piezo-scan-
ner and drift-correction of the images recorded.
Figure 4. STM current images of highly ordered monolayers at the so-
lid–liquid interface of (a) 6a, and (b) 6c. (c) and (d) are representations
of the respective unit cells; the directions of the long molecular axes
with respect to the unit cell are indicated. In (d), the distances between
the long molecular axes of adjacent molecules are also indicated. Tun-
neling parameters: sample bias Us = –1.0 V and average tunneling cur-
rent It = 330 pA and It = 80 pA for (a) and (b), respectively.
Molecular modeling was performed with Hyperchem 6.02
(www.hyper.com).
General Procedure for the 2,9-Arylation of Phenanthrolines 1 and 2:
In a typical procedure, a 2.5  solution of n-butyllithium in hexane
(8.30 mmol) was slowly added to a solution of the corresponding
bromoarene (8.30 mmol) in diethyl ether (20 mL) at 0 °C. The solu-
tion was stirred for 4 h at room temperature, then a suspension of
1 or 2 (4.15 mmol) in diethyl ether (20 mL) was added at 0 °C over
10 min. The solution immediately turned dark violet. The mixture
was stirred for 24 h at room temperature. Prolonged reaction times
led to the formation of unwanted products. The additions were
very sensitive to moisture. Best yields were obtained by monitoring
the reaction using ESI-MS. After the reaction was complete, satu-
rated NH4Cl (25 mL) was added, and the layers were separated.
The aqueous layer was extracted 3–4 times with dichloromethane
(4×50 mL). The combined organic extracts were stirred with acti-
vated MnO2 (83.1 mmol) for 12 h. The mixture was then filtered
through Celite and dried with MgSO4, and the solvents evaporated.
The resulting solid was separated by column chromatography
(SiO2, initially hexane, then later dichloromethane). The products
were obtained as white to pale yellow solids.
Figure 5. Visualization of the arrangement of 6a (left) and
6c (right) on the HOPG surface (by Hyperchem 6.02;
www.hyper.com).
2-[2,6-Dimethyl-4-(triisopropylsilanyloxy)phenyl]-3-trimethylsilanyl-
ethynyl[1,10]phenanthroline (2a): Yield: 1.40 g (61 %). 1H NMR
(CDCl3, 200 MHz): δ = 9.21 (d, J = 4.5 Hz, 1 H), 8.39 (s, 1 H),
8.23 (d, J = 8.1 Hz, 1 H), 7.77 (s, 2 H), 7.59 (dd, J = 8.1, 4.5 Hz,
1 H), 6.60 (s, 2 H), 2.01 (s, 6 H), 1.16 (m, 21 H, TIPS), 0.06 (s, 9
H, TMS) ppm. 13C NMR (CDCl3, 50 MHz): δ = 163.8, 156.4,
151.6, 147.1, 145.8, 140.0, 139.9, 138.3, 136.8, 130.1, 127.8, 127.4,
126.8, 123.9, 121.3, 118.9 (arom.), 102.8 (2 C, ethynyl), 21.2, 19.1,
Conclusions
Several rigid, linear bisphenanthrolines with and without
bulky aryl groups at the bisimine sites were synthesized
through covalent coupling. For three representatives, the so-
lid-state structures were elucidated. Their potential was ex-
plored for self-assembled monolayers by scanning tunneling
microscopy (STM) at solid–liquid interfaces, and the re-
sulting monolayers were found to be promising candidates
for templating metal-ion nanopatterns. Future studies will
focus on the surface chemistry of these ligands in the pres-
ence of metal cations and on their photophysical studies.
13.8, 0.49 ppm. IR (KBr): ν = 2945, 2868, 2152, 1601, 1466, 1397,
˜
1319, 1249, 1160, 1047, 996, 858, 843, 812, 686, 608 cm–1. ESI-
MS [C34H44N2OSi2 +H]+: calcd. m/z = 553.3; found m/z = 553.6.
C34H44N2OSi2 (552.90): calcd. C 73.86, H 8.02, N 5.07; found C
73.75, H 7.94, N 4.95.
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2-Anthracen-9-yl-3-trimethylsilanylethynyl[1,10]phenanthroline (2b): and H2O (12 mL) was stirred for 12 h under argon at room tempera-
1
Yield: 0.88 g (47%). H NMR (CD2Cl2, 200 MHz): δ = 9.07 (d, J ture. An aqueous buffer solution (pH 7.0) was added until a solid
= 4.5 Hz, 1 H), 8.64 (s, 1 H, anthracene), 8.57 (s, 1 H), 8.31 (d, J
= 8.4 Hz, 1 H), 8.11–8.16 (m, 2 H, anthracene), 7.95 (s, 2 H), 7.63
(dd, J = 8.4, 4.5 Hz, 1 H), 7.46–7.53 (m, 4 H, anthracene), 7.29–
7.38 (m, 2 H, anthracene), 0.54 (s, 9 H, TMS) ppm. 13C NMR
(CD2Cl2, 50 MHz): δ = 160.4, 150.7, 139.0, 138.9, 136.0, 131.4,
130.2, 129.4, 128.5, 127.7, 127.6, 127.5 (2 C), 126.0, 125.9, 125.7,
125.6, 125.1, 123.3, 121.4 (arom.), 88.2, 77.2 (ethynyl), –1.4 ppm.
ESI-MS [C31H24N2Si+H]+: calcd. m/z = 453.2; found m/z = 453.4.
C31H24N2Si (452.62): calcd. C 82.26, H 5.34, N 6.19; found C
82.30, H 5.43, N 6.17.
began to precipitate. THF and water were then evaporated under
vacuum. The resulting solid was washed with water several times to
afford phenol 5aЈ (146 mg) as a light yellow solid in 95% yield. Data
for 5aЈ is given below.
General Procedure for Sonagashira Coupling Reactions (5a–b, 6a–c): 3-
Ethynyl-phenanthrolines 1Ј or 4 (1.66 mmol), CuI (1.66 mmol), 1,4-
diiodobenzenes (0.83 mmol), and [PdCl2(PPh3)2] (0.166 mmol) were
stirred in dry benzene (15 mL) and NEt3 (15 mL) under argon at 80 °C
for 24 h. The reaction was monitored by ESI-MS or TLC. After re-
moval of the solvents, the remaining solid was dissolved in CH2Cl2 and
washed with aqueous KCN (50 mL, 2% w/v). The residue was purified
by column chromatography (SiO2, hexane at first and CH2Cl2 later) to
furnish a white crystalline product.
2-[2,6-Dimethyl-4-(triisopropylsilanyloxy)phenyl]-9-(2,4,6-trimeth-
ylphenyl)-3-trimethylsilanylethynyl[1,10]phenanthroline (3a): Yield:
1
1.84 g (66%). H NMR (CDCl3, 200 MHz): δ = 8.39 (s, 1 H), 8.25
(d, J = 8.3 Hz, 1 H), 7.81 (s, 2 H), 7.56 (d, J = 8.3 Hz, 1 H), 6.92
(s, 2 H), 6.57 (s, 2 H), 2.30 (s, 3 H), 2.12 (s, 6 H), 2.03 (s, 6 H),
1.21 (m, 21 H, TIPS), 0.09 (s, 9 H, TMS) ppm. 13C NMR (CD2Cl2,
100 MHz): δ = 145.3, 144.9, 142.9, 139.0, 138.1, 137.3, 136.1, 135.7,
132.8, 128.3, 128.2, 128.1, 127.6, 126.8, 126.6, 125.5, 124.7, 119.9,
118.1, 115.6 (arom.), 98.9, 94.2 (ethynyl), 20.1, 19.6, 17.9 (2 C),
5a: Yield: 987 mg (89%). 1H NMR (CD2Cl2, 200 MHz): δ = 8.52 (s, 2
H), 8.34 (d, J = 8.1 Hz, 2 H), 7.89 (s, 4 H), 7.56 (d, J = 8.1 Hz, 2 H),
7.13 (s, 4 H, phenyl spacer), 6.93 (s, 4 H), 6.67 (s, 4 H), 2.30 (s, 6 H),
2.01 (br. s, 24 H), 1.10 (m, 42 H, TIPS) ppm. 13C NMR (CD2Cl2,
50 MHz): δ = 161.5, 160.6, 155.5, 137.6, 137.5, 136.4, 136.2, 135.7,
131.4, 131.3, 131.1, 128.2, 128.0, 127.9, 127.7, 127.0, 126.9, 125.6,
125.0, 122.9, 119.9, 118.4 (arom.), 94.1, 88.7 (ethynyl), 20.2, 17.7 (3 C),
12.8, –1.0 (aliph.) ppm. IR (KBr): ν = 3442, 2943, 2865, 2152 (ν
˜
CϵC), 1602, 1459, 1393, 1321, 1249, 1162, 1048, 996, 858, 846,
810, 686, 641 cm–1. ESI-MS [C43H54N2OSi2 + H]+: calcd. m/z =
671.4; found m/z = 671.8. C43H54N2OSi2 (671.07): calcd. C 76.96,
H 8.11, N 4.17; found C 76.65, H 8.30, N 4.01.
12.7 ppm. IR (KBr): ν = 3407, 3044, 2944, 2865, 1720 (CϵC), 1602,
˜
1537, 1504, 1458, 1395, 1320, 1165, 1047, 992, 917, 885, 847, 809, 685,
637 cm–1. ESI-MS [C86H94N4O2Si2 +H]+: calcd. m/z = 1271.7; found
m/z (%) = 1272.0 (70). ESI-MS [C86H94N4O2Si2 +2H]+2: calcd. m/z =
637.3; found m/z (%) = 637.4 (100). C86H94N4O2Si2·¾CH2Cl2
(1335.56): calcd. C 78.01, H 7.21, N 4.20; found C 78.26, H 7.64, N
3.97.
2,9-Dianthracen-9-yl-3-trimethylsilanylethynyl[1,10]phenanthroline
1
(3b): Yield: 2.04 g (78%). H NMR (CD2Cl2, 400 MHz): δ = 8.62
(s, 1 H, phenanthroline), 8.44–8.49 (m, 2 H, anthracene), 8.35 (d,
J = 8.3 Hz, 1 H, phenanthroline), 8.04 (s, 2 H, phenanthroline),
7.95–7.97 (m, 4 H, anthracene), 7.66–7.78 (m, 4 H, anthracene),
7.65 (d, J = 8.3 Hz, 1 H, phenanthroline), 7.22–7.61 (m, 8 H, an-
thracene), –0.41 (s, 9 H, TMS) ppm. 13C NMR (CD2Cl2,
100 MHz): δ = 161.1, 159.4, 146.7 (2 C), 145.4, 139.5 (2 C), 136.4
(2 C), 135.7 (2 C), 134.5, 133.8, 131.7 (2 C), 130.9, 128.7, 128.6 (2
C), 128.1, 127.9 (2 C), 126.8 (2 C), 126.0, 125.6, 125.3, 122.1
(arom.), 102.7 80.9 (ethynyl), –0.67 ppm. ESI-MS [C45H32N2Si+H]+:
calcd. m/z = 629.2; found m/z (%) = 629.6 (100). C45H32N2Si (628.83):
calcd. C 85.95, H 5.13, N 4.45; found C 85.63, H 5.07, N 4.83.
5aЈ: 1H NMR ([D7]DMF, 200 MHz): δ = 9.52 (s, 2 H, –OH), 8.86 (s, 2
H), 8.64 (d, J = 8.1 Hz, 2 H), 8.16 (s, 4 H), 7.76 (d, J = 8.1 Hz, 2 H),
7.28 (s, 4 H, phenyl spacer), 6.97 (s, 4 H), 6.68 (s, 4 H), 2.31 (s, 6 H),
2.03 (s, 12 H), 2.01 (s, 12 H) ppm. 13C NMR ([D7]DMF, 50 MHz): δ =
163.1, 162.5 (2 C), 161.9, 161.8, 160.7, 157.9, 145.4, 138.8 (2 C), 137.7,
137.6, 137.1, 135.9, 132.6, 131.9, 128.4, 127.5 (2 C), 123.3, 119.9, 114.5
(arom.), 89.9 (2 C, ethynyl), 20.1, 18.1, 13.5 ppm. IR (KBr): ν = 3284,
˜
2919, 2854, 2210 (CϵC), 1612, 1503, 1456, 1397, 1315, 1157, 1030,
909, 848, 775, 638 cm–1. ESI-MS [C68H54N4O2 +H]+: calcd. m/z =
960.2: found m/z (%) = 959.9 (100). ESI-MS [C68H54N4O2 +2H]+2
:
Procedures for TMS or TIPS Deprotection
calcd. m/z = 480.2; found m/z (%) = 480.9 (70). C68H54N4O2·¼CH2Cl2
(980.42): calcd. C 83.61, H 5.60, N 5.71; found C 83.96, H 5.71, N 5.81
(see also single crystal structure).
TMS Deprotection: Typically, the 3-trimethylsilanylethynylphen-
anthroline building block (4a,b, 0.195 mmol) was first dissolved in
THF/MeOH, then aqueous KOH (1 , 10 mL) was added. After stir-
ring for 12 h, the solution was diluted with aqueous NH4Cl and ex-
tracted with CH2Cl2. The combined organic layers were dried with
MgSO4, and the solvents were removed to yield a colorless solid. It was
further purified by column chromatography (SiO2, dichloromethane)
to yield the product as a white crystalline material. Compound 4b was
used without further characterization in the synthesis of 5b.
4a: Yield: 104 mg (89%). 1H NMR (CDCl3, 200 MHz): δ = 8.45 (s, 1
H), 8.26 (d, J = 8.1 Hz, 1 H), 7.83 (br. s, 2 H), 7.57 (d, J = 8.1 Hz, 1 H),
6.92 (s, 2 H), 6.61 (s, 2 H), 3.06 (s, 1 H), 2.31 (s, 3 H), 2.13 (s, 6 H), 2.05
(s, 6 H), 1.24 (m, 21 H, TIPS) ppm. 13C NMR (CDCl3, 50 MHz): δ =
162.8, 161.4, 156.4, 146.9, 146.2, 141.3, 141.2, 138.8, 138.5, 137.2,
133.7, 129.5, 129.4, 128.5, 127.9, 127.5, 126.4, 126.3, 120.1, 119.6
(arom.), 83.1, 81.7 (ethynyl), 24.8, 21.5, 19.0 (2 C), 13.7 (aliph.) ppm.
5b: Yield: 306 mg (31%). 1H NMR [CD2Cl2/trifluoroacetic acid
(0.3:0.01 mL), 200 MHz]: δ = 8.89 (d, J = 8.3 Hz, 2 H), 8.35 (s, 2 H),
8.21 (d, J = 8.3 Hz, 2 H, phenanthroline), 8.05 (s, 4 H), 7.90–7.94 (m,
6 H, anthracene), 7.51–7.60 (m, 8 H, anthracene), 6.88–6.99 (m, 12 H,
anthracene), 6.72–6.81 (m, 8 H, anthracene), 6.60–6.64 (m, 2 H, an-
thracene) ppm. C90H50N4 (1187.39): calcd. C 91.04, H 4.24, N 4.72;
found C 91.10, H 4.01, N 4.90.
1
6a:[15] Yield: 629 mg (89%). H NMR (CD2Cl2, 200 MHz): δ = 9.26
(br. s, 2 H), 9.16 (d, J = 4.2 Hz, 2 H), 8.35 (s, 2 H), 8.23 (d, J = 8.5 Hz,
2 H), 7.78 (d, J = 8.6 Hz, 2 H), 7.76 (d, J = 8.6 Hz, 2 H), 7.67–7.58 (m,
2 H ) , 7 . 1 0 ( s, 2 H , p h e n y l ) , 4 . 0 7 ( t , J = 7 . 1 H z , 4 H ,
–OCH2–), 1.85 (q, J = 7.1 Hz, 4 H, aliph.), 1.15–1.09 (m, 36 H, aliph.),
0.79 (t, J = 6.4 Hz, 6 H, –CH3) ppm. ESI-MS [C58H66N4O2 + H]+:
calcd. m/z = 851.5; found m/z (%) = 851.7 (100). ESI-MS
[C58H66N4O2 +2H]2+: calcd. m/z = 426.6; found m/z (%) = 426.6 (25).
C58H66N4O2 (851.17): calcd. C 81.84, H 7.82, N 6.58; found C 81.40,
H 7.91, N 6.70 (see also single crystal structure).
IR (KBr): ν = 3412, 2924, 2866, 2110 (CϵC), 1603, 1460, 1395, 1319,
˜
1159, 1046, 884, 849, 810, 686, 639 cm–1. ESI-MS [C40H46N2OSi+
H]+: calcd. m/z = 599.3; found m/z = 599.7. C40H46N2OSi (598.89):
calcd. C 80.22, H 7.74, N 4.68; found C 79.89, H 7.69, N 4.55.
TIPS Deprotection:[32] A solution of 5a (200 mg, 157 µmol) and 6b: Yield: 374 mg (61%). 1H NMR (CD2Cl2, 200 MHz): δ = 9.23 (br.
(nBu)4NF·3H2O (248 mg, 786 µmol) in a mixture of THF (12 mL) s, 2 H), 9.13 (d, J = 4.5 Hz, 2 H), 8.36 (s, 2 H), 8.26 (d, J = 8.1 Hz, 2
3084
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Eur. J. Org. Chem. 2006, 3079–3086

Rigid Bisphenanthrolines
FULL PAPER
[6]
a) M. Schmittel, A. Ganz, Chem. Commun. 1997, 999–1000; b) M.
Schmittel, U. Lüning, M. Meder, A. Ganz, C. Michel, M. Herder-
ich, Heterocycl. Commun. 1997, 3, 493–498.
M. Schmittel, V. Kalsani, R. S. K. Kishore, H. Cölfen, J. W. Bats,
J. Am. Chem. Soc. 2005, 127, 11545–11546.
Related but unsubstituted bisphenanthrolines were originally re-
ported as ruthenium complexes, D. Tzalis, Y. Tor, Chem. Commun.
1996, 1043–1044.
M. Schmittel, C. Michel, S.-X. Liu, D. Schildbach, D. Fenske, Eur.
J. Inorg. Chem. 2001, 1155–1166.
H), 7.82 (d, J = 8.3 Hz, 2 H), 7.80 (d, J = 8.3 Hz, 4 H), 7.64 (dd,
J = 8.1, 4.5 Hz, 2 H), 7.15 (s, 2 H, phenyl), 4.10 (t, J = 6.4 Hz, 4 H,
–OCH2–), 1.98–1.84 (m, 4 H, aliph.), 1.66–1.56 (m, 4 H, aliph.), 1.52–
1.26 (m, 16 H, aliph.), 0.82 (t, J = 6.9 Hz, 6 H, –CH3) ppm. 13C NMR
(CD2Cl2, 50 MHz): δ = 153.9, 151.7, 150.5, 146.0, 144.9, 137.8 (2C),
135.9, 129.1, 127.9, 126.1, 123.2, 119.5, 116.9, 113.7 (arom.), 92.0, 90.1
(ethynyl), 69.7 (H2CO), 31.9, 29.4 (2 C), 26.1, 22.7 (2 C), 13.9 (aliph.)
[7]
[8]
ppm. IR (KBr): ν = 3027, 2921, 2851, 2204 (CϵC), 1589, 1552, 1505,
˜
[9]
1467, 1411, 1383, 1277, 1218, 1123, 1097, 1062, 970, 908, 833, 734,
694 cm–1. ESI-MS [C50H50N4O2 +H]+: calcd. m/z = 739.4; found
m/z (%) = 739.6 (100). C50H50N4O2 (738.96): calcd. C 81.27, H 6.82, N
7.58; found C 81.29, H 6.90, N 7.32 (see also single crystal structure).
[10]
M. Schmittel, C. Michel, A. Wiegrefe, V. Kalsani, Synthesis 2001,
1561–1567.
[11]
[12]
M. Schmittel, A. Ganz, D. Fenske, Org. Lett. 2002, 4, 2289–2292.
C. O. Dietrich-Buchecker, P. A. Marnot, J. P. Sauvage, Tetrahe-
dron Lett. 1982, 23, 5291–5294.
6c: Yield: 476 mg (84%). 1H NMR (CD2Cl2, 200 MHz): δ = 9.20 (s, 2
H), 9.11 (d, J = 4.5 Hz, 2 H), 8.35 (s, 2 H), 8.23 (d, J = 8.4 Hz, 2 H),
7.77 (d, J = 8.4 Hz, 2 H), 7.75 (d, J = 8.4 Hz, 2 H), 7.61 (dd, J = 8.4,
4.5 Hz, 2 H), 7.13 (s, 2 H, phenyl), 4.09 (t, J = 6.4 Hz, 4 H, –OCH2–),
1.97–1.64 (m, 4 H, aliph), 1.60–1.32 (m, 12 H, aliph.), 0.82 (t, J =
6.9 Hz, 6 H, –CH3) ppm. 13C NMR (CD2Cl2, 100 MHz): δ = 151.9,
148.7, 144.1, 142.8, 136.1, 134.1, 130.2, 127.0, 125.8, 124.1, 121.3 (2
C), 117.8, 114.9, 111.9 (arom.), 90.2, 88.4 (ethynyl), 54.1 (H2CO), 29.9,
27.8, 27.5, 24.2, 20.7 ppm. ESI-MS [C46H42N4O2 +H]+: calcd. m/z =
683.3: found m/z (%) = 683.1 (100). C46H42N4O2 (682.85): calcd. C
80.91, H 6.20, N 8.20; found C 80.54, H 6.32, N 8.12.
[10]
[13]
[14]
The synthesis of 3c and 3d has been reported earlier.
A. de Meijere, F. E. Meyer, Angew. Chem. 1994, 106, 2473–2506;
Angew. Chem. Int. Ed. Engl. 1994, 33, 2379–2411.
[15]
a) U.-W. Grummt, E. Birckner, M. Al-Higari, D. A. M. Egbe, E.
Klemm, J. Fluoresc. 2001, 11, 41–51; b) M. Al-Higari, E. Birckner,
B. Heise, E. Klemm, J. Poly. Sci., Part A: Polymer Chem. 1999, 37,
4442–4448.
Crystal data for 5aЈ: C68H54N4O2·4DMF (DMF = dimethylform-
amide), M = 1251.54, monoclinic, space group C2/c, a =
32.113(6) Å, b = 15.049(3) Å and c = 14.506(3) Å, α = 90º, β =
93.72(3)º, γ = 90º, V = 6996(2) Å3, T = 193(2) K, Z = 4, Dc =
1.188 g/cm3, λ(Mo-Kα) = 0.71073 Å, 8207 reflections measured,
[16]
5570 unique (Rint
all calculations. R1 = 0.0781 [IϾ2σ(I)] and wR2 = 0.1679,
GOF 1.075. CCDC reference number CCDC-299815.
=
0.0509) which were used in
Acknowledgments
=
The CCDC data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
The authors gratefully acknowledge the financial support by the DFG
(Deutsche Forschungsgemeinschaft) and the Fonds der Chemischen
Industrie. We are indebted to Dr. Clemens Stupperich for technical
help with the figures and drawings.
[17]
Crystal data for 6a: Suitable single crystals were obtained
by the slow evaporation of
a dichloromethane solution
containing 6a. Solvent could be located partially.
¯
C58H66N4O2·nCH2Cl2, M = 1016.97, triclinic, space group P1, a
= 11.973(2) Å, b = 13.924(3) Å and c = 18.606(4) Å, α =
75.53(11)º, β = 82.81(3)º, γ = 73.32(3)º, V = 2872.3(10) Å3, T =
193(2) K, Z = 2, Dc = 1.176 g/cm3, λ(Mo-Kα) = 0.71073 Å, 12600
reflections measured, 8519 unique (Rint = 0.0310) which were used
in all calculations. R1 = 0.1138 [IϾ2σ(I)] and wR2 = 0.3082, GOF
= 1.041. CCDC reference number CCDC-299301.
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Crystal data for 6b: Suitable single crystals were obtained by the
slow of evaporation of dichloromethane solution containing 6b.
¯
C50H50N4O2·2CH2Cl2, M = 908.79, triclinic, space group P1, a =
10.8660(16) Å, b = 10.987(2) Å and c = 12.019(2) Å, α =
102.442(11)º, β = 105.003(12)º, γ = 114.479(9)º, V = 1173.4(4) Å3,
T = 155(2) K, Z = 1, Dc = 1.286 g/cm3, λ(Mo-Kα) = 0.71073 Å,
20884 reflections measured, 7645 unique (Rint = 0.0428) which
were used in all calculations. R1 = 0.0458 [IϾ2σ(I)] and wR2 =
0.1167, GOF
= 1.028; max/min residual density 0.587/–
0.337 eÅ–3. CCDC reference number CCDC-299302.
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Published Online: May 22, 2006
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Eur. J. Org. Chem. 2006, 3079–3086