Supramolecular organization based on van der Waals forces: Syntheses and solid state structures of isomeric [6.6] cyclophanes with 2,5-diselenahex-3-yne bridges

Article abstract of DOI:10.1002/ejoc.200900106

The ortho, meta,and para isomers 4-6 of [6.6]cyclophanes with 2,5-diselenahex-3-yne bridges were synthesized by reacting the bis(selenocyanatomethyl)benzene derivatives 8a- 8c with the lithium salt of trimethylsilylethyne to yield 9a-9c, deprotection of w

Full text of DOI:10.1002/ejoc.200900106

FULL PAPER
DOI: 10.1002/ejoc.200900106
Supramolecular Organization Based on van der Waals Forces: Syntheses and
Solid State Structures of Isomeric [6.6]Cyclophanes with 2,5-Diselenahex-3-yne
Bridges
Alberth Lari,[a] Rolf Gleiter,*[a] and Frank Rominger[a]
Dedicated to the memory of Prof. Mircea D. Banciu
Keywords: Supramolecular chemistry / Cyclophanes / Alkynes / Selenium / Diselenaalkynes / van der Waals contacts
The ortho, meta, and para isomers 4–6 of [6.6]cyclophanes
tween one Se–CϵC–Se unit of each molecule leading to a
with 2,5-diselenahex-3-yne bridges were synthesized by re- linear chain of orthocyclophane rings. In the metacyclo-
acting the bis(selenocyanatomethyl)benzene derivatives 8a–
8c with the lithium salt of trimethylsilylethyne to yield 9a–9c,
deprotection of which afforded the bis(ethynylselenylmeth-
yl)benzenes 10a–10c. The condensation of the bis-lithium
salts of 10a–10c with 8a–8c yielded the target compounds 4–
6. X-ray investigations on single crystals of 4–6 revealed
intermolecular Se···Se interactions which contribute signifi-
cantly to the solid-state structures of these species. In the
phane, 5, the rings adopt a chair conformation and are piled
on top of each other. The resulting molecular channels are
connected with each other by intermolecular Se···Se interac-
tions. For 6 also a chair conformation of the [6.6]paracyclo-
phane unit was encountered. In the solid state the rings of 6
are connected by intermolecular Se···Se bridges.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
case of the orthocyclophane 4, we found short distances be- Germany, 2009)
Introduction
Molecular entities assembling to cavities are of consider-
able interest in the field of host-guest chemistry.[1,2] Exam-
ples for such assemblies are cyclic peptides,[3] cyclodex-
trins[4] or shape persistent cyclic hydrocarbons with phen-
olic groups,[5] to name only a few. Recently, we found that
cyclic tetrachalcogenaalkynes of the type 1 or 2 (Figure 1)
adopt columnar structures in the solid state[6,7] with cavities
which allow the inclusion of organic solvents. The columnar
structures are maintained by intermolecular forces between
the chalcogen centers of neighboring columns. Varying the
hydrocarbon chains between the rigid 1,2-dichalcogenaace-
tylene (m = 1) or 1,4-dichalcogenabutadiyne (m = 2) units
shows that short chains up to five CH2 groups are required
to maintain a sizeable cavity within the ring. With longer
(CH2)n chains the collapse of the cavity is observed.[7c]
In this paper we report on systems in which part of each
(CH2)n bridge in 2 is replaced by a benzene ring. This adds
in terms of intermolecular interaction a new component:
The chalcogen–chalcogen interactions now compete with
π–π interactions.
[a] Organisch-Chemisches Institut der Universität Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Fax: +49-6221-544205
E-mail: rolf.gleiter@oci.uni-heidelberg.de
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Figure 1. Tetrachalcogenaalkynes 1–3 and the [6.6]cyclophanes 4–
6 with 2,5-diselenahex-3-yne bridges.
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A. Lari, R. Gleiter, F. Rominger
FULL PAPER
As chalcogen centers we chose selenium (e.g. 3) because
its intermolecular interaction is expected to be considerably
stronger than that of sulfur.[8] Our endeavour was facilitated
by recent progress in organoselenium chemistry[9] and in the
synthesis of chalcogena–alkynes.[6,7,10] As first representa-
tives of 3 we report in this paper the synthesis and struc-
tural properties of the three isomeric [6.6]cyclophanes 4–6.
Figure 2. ORTEP representation (50% ellipsoid probability) of the
molecular structures of 1,4-bis(seleno-cyanatomethyl)benzene (8c –
left) and 1,4-bis(ethynylselenylmethyl)benzene (10c – right) in the
solid state. Hydrogen atoms are not displayed for the sake of clarity.
Results and Discussion
Synthesis of [6.6]Cyclophanes 4–6
Starting points of our synthesis were the three isomeric
1,n-bis(selenocyanatomethyl)-benzenes 8a–8c (Scheme 1)
which were generated from the corresponding 1,n-bis-
(bromomethyl)benzenes 7a–7c.
Furthermore the overall low yields observed for 4–6 are
also due to several side reactions which are specific for or-
ganoselenic compounds. When 10a–10c are treated with
nBuLi to generate the corresponding bis(lithium) salt the
agent may abstract the proton at the alkyne unit or react
with the Se center under substitution and elimination of
LiC2H.[7a,10b]
Although all three cyclophanes are highly sensitive to air,
light and humidity we were able to characterize them com-
pletely. The usual ionization methods for obtaining high-
resolution mass spectra (EI, FAB or MALDI) proved not
to be suitable for these species. Only by utilizing the FDI
method we obtained the molecular peaks of the three iso-
mers 4–6. In the Supporting Information all three Liquid
Injection Field Desorption Ionization (LIFDI) spectra are
compared with the theoretical isotopic pattern.
Structural Investigations
We were able to grow single crystals of 4–6 which were
suitable for X-ray diffraction studies. The molecular struc-
ture of 4 was already discussed in a preliminary report.[12]
The planes of the aromatic rings in 4 are twisted by 87°
among each other. The torsion angles between the Se–CH2
Scheme 1. General synthetic procedure for preparation of the [6.6]-
cyclophanes 4–6.
The reaction of 7a–7c with KSeCN in acetone at room bonds along the Se(1)···Se(2) axis amount to 74.7° and
temperature[11] afforded the bis(selenacyanatomethyl)ben- along the Se(3)···Se(4) axis to 92.2°. This result is in line
zenes 8a–8c in good yields as colorless crystals. The reac- with other studies which show that for the CH2–Se–CϵC–
tion of 8a–8c with lithiated trimethylsilylethyne[10] (TMSA) Se–CH2 units in cyclic systems torsional angles between 60°
yielded the bisdiselenaalkadiynes 9a–9c as yellow colored and 90° are preferred due to the repulsion of the 4p lone
oils (9a, 9b) or crystals (9c). The removal of the protecting pairs at the Se centers.[7a]
group was achieved by treatment with 0.1  NaOH solution
In Figure 3 we show a section of the solid state of 4. It
affording the alkynes 10a–10c. The alkynes were trans- is found that the rings are stacked on top of each other in
formed into the bis-lithium salts and subsequently reacted the crystallographic b-direction. A remarkable feature of
with an equivalent of the selenocyanates 8. The yields of the structure of 4 is that only one Se–CϵC–Se unit of each
the purified cyclophanes were low and varied between 7.4% molecule is involved in strong intermolecular interactions.
(5) and 2% (6). The anti-conformation of the functional This leads to a one dimensional thread of ···Se–CϵC–Se···
groups of 1,4-bis(ethynylselenylmethyl)benzene (10c) and units in the crystallographic c-direction with the cy-
1,4-bis(selenocyanatomethyl)benzene (8c) found in the solid clophanes alternating on both sides. The Se···Se contacts
state might also contribute to the exceptional low yield of along this thread (bold dashed lines) amount to only 3.48 Å
6. Due to this conformation the simultaneous coupling be- and 3.52 Å, respectively. Parallel strings are connected by
tween both species should be rather low. Interestingly in the weaker Se···Se interactions (3.93 Å, light dashed lines) in
case of 8a both functional groups show a syn-cis conforma- the crystallographic a-direction. In both cases these dis-
tion. The molecular structures of 8c and 10c are depicted tances are shorter than or close to the sum of the van der
in Figure 2.
Waals radii for Se: 3.80 Å.[13] It is remarkably that the
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Supramolecular Organization Based on van der Waals Forces
C(sp3)–Se–C(sp) angles amount to 102.1° and 102.6° for Se···Se interactions (3.975 Å) are close to those reported for
the selenium atoms involved into the short Se···Se contacts, related systems[7] and agree with the values computed for a
whereas this angle at the selenium atoms with the weaker van der Waals dimer consisting of two dimethylselenide
interaction is much smaller (99.1° and 98.1°). The first type units (d = 3.91 Å).[8a]
of Se–CϵC–Se units leading to the threaded arrangement
(see Figure 3), is more bent than the second one and shows
a smaller torsion angle between the CH2–Se bonds (74.7°
as compared to 92.2° of the second one).
Figure 3. Threaded arrangement in the solid-state structure of 4
(50% ellipsoid probability). Thick dotted lines represent strong
Se···Se interactions (Se1–Se1 3.476 Å, Se2–Se2 3.523 Å), thin dot-
ted lines represent weak Se···Se interactions (Se4–Se4 3.934 Å). Hy-
drogen atoms are not displayed for the sake of clarity.
In the metacyclophane 5 the molecular structure shows
a chair conformation with Ci symmetry. Both planes of the
aromatic rings are parallel to each other and the torsion
angle between the Se–CH2 bonds along the Se(2)···Se(5)
axis amounts to 58.2° (Figure 4).
Figure 5. Plots of weak Se–H hydrogen bonds (light dashed lines),
CH···π contacts (dotted lines) and Se···Se interactions (bold dashed
lines) observed in the crystal lattice of 5. Top: intermolecular weak
interactions between different levels of the stacks. Bottom: intermo-
lecular weak interactions connecting different stacks in the crystal-
lographic a–c plane.
The Se···H bonds vary between 2.95 Å (intramolecular)
and ca. 3.30 Å (intermolecular) and represent so called
weak hydrogen bonds.[14] CH···π interactions[15] between
the benzylic proton and the C(sp)–C(sp) unit from a mole-
cule situated in the same stack with distances of 2.72 Å
[H···C(sp)] are also involved in generating the stacks. Sim-
ilar interactions have been observed in the case of orthocy-
clophane 4, with distances even smaller, of ca. 2.69 Å
Figure 4. ORTEP representation of the molecular structure of 5
(50% ellipsoid probability) in the solid state. Hydrogen atoms are
not displayed for the sake of clarity.
The bond angles C(sp3)–Se–C(sp) both amount to 98.0°. [H···C(sp)].
We notice in the crystal a stacking of the rings on top of
The paracyclophane 6 also adopts a chair conformation
each other in the crystallographic b-direction. The Se···Se (non-crystallographic C2h) in the solid state. The planes of
distances are rather long in these stacks (Ͼ4.36 Å). So pre- the two aromatic rings are symmetry imposed parallel. The
sumably weak Se···H and CH···π interactions are responsi- torsion angle between the CH2–Se bonds along the Se(1)···
ble for the stacking rather than Se···Se interactions. The Se(2) axis amounts to 116.7°. This value is considerably
various stacks of the metacyclophane rings are hold to- larger than those values found for 4 and 5 indicating some
gether with intermolecular Se···Se interactions, weak Se···H strain energy due to the para-connection. The C(sp3)–Se–
bonds[14] and CH···π interactions.[15] All types of interac- C(sp) angles in 6 were recorded to be 97.1° and 99.7°,
tions are indicated in Figure 5. The values found for the respectively.
Eur. J. Org. Chem. 2009, 2267–2274
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A. Lari, R. Gleiter, F. Rominger
FULL PAPER
In the solid state each selenium atom of 6 (Figure 6) is
involved into three short contacts (3.79 Å, 3.80 Å and
3.81 Å) to selenium atoms of three different neighboring
molecules, giving rise to a structure with two-dimensional
Se-regions showing multiply linked selenium networks.
The expected competition between selenium–selenium
interactions and π–π interactions could be observed espe-
cially in the case of the cyclophanes 5 and 6, which show a
chair conformation in the solid-state structures, whereas for
compound 4, due to the twisting of the benzene rings, the
π–π interactions were not favoured, leading to stronger
Se···Se interactions. Compound 5, having the weakest
Se···Se interactions from all three isomers, shows in the so-
lid-state structure a distance between two benzene planes
that amounts to 3.51 Å. In the columnar structure, the ben-
zene rings are in an offset arrangement, in which the ben-
zylic CH2 group is situated right under one benzene ring
from the upper molecule in the stack. In the case of com-
pound 6, that has stronger Se···Se interactions than com-
pound 5, but weaker than the ones observed in compound
4, the distance between two benzene ring planes amounts to
3.58 Å. These observations illustrate both the competitive
relation between non-bonding interactions and also their
complementary action that helps keep up a supramolecular
structure.
Figure 7. Isomeric [6.6]cyclophanes 11–13 with 1,6-dioxahex-3-yne
bridges.
Conclusions
Utilizing a two-component condensation reaction be-
tween a 1,2-, 1,3- and 1,4-bis(selenocyanatomethyl)benzene
(8a–8c) and the bis(lithium) salts of 1,2-, 1,3- and 1,4-bis-
(ethynylselanylmethyl)benzene (10a–10c) yielded the corre-
sponding [6.6]cyclophanes bridged with 2,5-diselenahex-3-
yne units in the ortho-, meta- and para-positions. The yields
of this condensation reaction varied between 2% and 7%.
This low yield was also due to side reactions of selena-sub-
stituted ethyne units with n-butyllithium. The solid-state
structures of 4–6 revealed in all three cases columnar struc-
tures with short Se···Se contacts between the columns. In-
tramolecular and intermolecular short Se···H distances
were also encountered.
Experimental Section
General Remarks: All melting points are uncorrected. The NMR
spectra were measured, with a Bruker ARX500 spectrometer (1H
NMR at 500 MHz, 13C NMR at 125 MHz and 77Se NMR at
95 MHz) and a Bruker ARX300 spectrometer (1H NMR at
300 MHz and 13C NMR at 75 MHz) using the solvent for calibrat-
Figure 6. Plot of intermolecular Se···Se interactions in the solid-
state structure of 6. Dotted lines represent contacts smaller than
sum of van der Waals radii (3.8 Å). Hydrogen atoms are not dis-
played for the sake of clarity.
1
ing the H NMR and the XSI scale for the heterogeneous nuclei.
High-resolution mass spectra (HR-MS) were obtained with ZAB-
3F (Vacuum Generators) and JEOL JMS 700 high resolution mass
spectrometers. UV/Vis absorption spectra were recorded with a
Hewlett–Packard HP 8452A Diode Array spectrometer. IR spectra
were recorded with a Bruker Vector 22 FTIR spectrometer. All
reactions were carried out in dry degassed solvents under argon
atmosphere, unless otherwise stated.
It is interesting to compare the molecular structures of
4–6 with those of the related [6.6]cyclophanes 11–13 (Fig-
ure 7) with 1,4 dioxabut-2-yne bridges.[16] In the latter cy- X-ray Crystallographic Study: The data were collected on a Bruker
APEX diffractometer at 100 K (for 4, 5) and a Bruker Smart dif-
fractometer (for 6, 8c and 10c) at 200 K using Mo-Kα radiation
(0.71073 Å). Relevant crystal and data collection parameters are
given in Table 1 for 8c and 10c, respectively, for 4–6 in Table 2. In
all cases, the collection strategies used 0.3 deg omega-scans cover-
ing a whole sphere in reciprocal space, intensities were corrected
for Lorentz and polarization effects and empirical absorption cor-
rections were applied using SADABS[17] based on the Laue sym-
metry of the reciprocal space, the structures were solved by direct
methods and refined against F2 using the SHELXTL-PLUS (5.10)
software package.[18]
clophanes the molecular structure is determined by the con-
jugation of the oxygen lone pairs with the benzene units
giving rise for the most part to planar dimethoxybenzene
units which lead to a rather planar ring (11) or rings with
chair conformations (12, 13). In contrast to 11–13, the mo-
lecular structures of 4–6 are determined by the rigid CH2–
Se–CϵC–Se–CH2 units which tend to adopt a torsional an-
gle close to 90°. This leads in the case of 4 to a twisting of
the benzene rings by 87° but to chair conformations for 5
and 6.
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Supramolecular Organization Based on van der Waals Forces
CCDC-662133 (for 4), -718215 (for 5), -718216 (for 6), -718217 (for
8c) and -718218 (for 10c) contain the supplementary crystallo-
graphic data for the structures. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Table 1. Crystal data and structural refinement for 8c and 10c.
8c
10c
Empirical formula
Formula weight
Crystal system
Space group
Z
C10H8N2Se2
314.10
monoclinic
P21/c
C12H10Se2
312.12
orthorhombic
Pbca
General Procedure for the Preparation of the Bis(selenocyanato-
methyl)benzenes 8a–c: To a stirred solution of dibromoxylene in
200 mL of degassed dry acetone a solution of KSeCN in 200 mL
of degassed acetone was added dropwise under argon atmosphere
at room temperature over a period of 3 h. The reaction mixture was
stirred for an additional hour and the resulting KBr was filtered off.
The solvent was removed by rotary evaporation and the product
was purified by column chromatography on deactivated silica, or
used as raw product when the purity was higher than 98% as calcu-
4
4
Unit cell dimensions
a [Å]
b [Å]
22.2635(9)
5.9933(3)
8.3679(4)
98.896(1)
1103.11(9)
1.89
5.9208(3)
8.5285(4)
22.4766(9)
90
1134.97(9)
1.83
c [Å]
β [°]
V [Å3]
Dcalcd. [g/cm3]
Absorption coeff. µ [mm–1]
Crystal shape
Crystal size [mm3]
Crystal colour
θ range for data collection
Index ranges
6.66
needle
6.47
polyhedron
1
lated from H NMR spectroscopic data.
2.00ϫ0.04ϫ0.02 0.20ϫ0.18ϫ0.06
colorless
1,2-Bis(selenocyanatomethyl)benzene (8a): Starting materials: 10.6 g
(40.0 mmol) of 1,2-bis-bromomethylbenzene (7a) and 14.4 g
(100 mmol) potassium selenocyanate. The resulting residue from
the solvent removal was purified by silica-gel chromatography using
a mixture of n-hexane/diethyl ether (1:2), resulting in 11.2 g of 8a
as white solid (35.8 mmol, 89%), slightly light sensitive. m.p.
106 °C. MS (EI+; m/z; %): 314 [M]+ (0.9), 263.9 [C8H8Se2]+ (7.8),
209.9 [M – SeCN]+ (52.8), 182.9 [C8H8Se]+ (28.4), 104 [C8H8]+ (BP,
colorless
0.9 to 27.5°
–28 Յ h Յ 28
–7 Յ k Յ 7
–10 Յ l Յ 10
9528
2488 (0.0694)
1835 [IϾ2σ(I)]
0.88/0.03
2488/0/108
1.30
0.108
0.257
3.37 and –1.36
1.8 to 27.5°
–7 Յ h Յ 7
–11 Յ k Յ 11
–29 Յ l Յ 29
10337
1300 (0.3352)
951 [I Ͼ2σ(I)]
0.70/0.36
1300/0/64
1.14
0.088
0.190
2.10 and –1.20
Reflections collected
Indep. reflections [R(int)]
Observed reflections
Max./min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
R(F)
1
100), 78 [C6H6]+ (18.2). H NMR (500 MHz, CD2Cl2): δH = 4.42
(s, 4 H, CH2), 7.38 (m, 2 H, Harom), 7.41 (m, 2 H, Harom) ppm. 13
C
NMR (125 MHz, CD2Cl2): δC = 30.9 (2 C, s-CH2), 101.5 (2 C, q-
SeCN), 130.0 (2 C, t-Carom), 131.9 (2 C, t-Carom), 134.5 (2 C, q-
RW(F2)
C
arom) ppm. 77Se NMR (95 MHz, CD2Cl2): δSe = 302.3 ppm. IR
(∆p)max., (∆p)min. [eÅ–3]
(KBr): ν = 3442 (vb), 3007 (w), 2148 (s), 2073 (m), 1630 (w), 1491
˜
(m), 1451 (m) cm–1.
Table 2. Crystal data and structural refinement for 4, 5 and 6.
4
5
6
Empirical formula
Formula weight
Crystal system
Space group
Z
C20H16Se4
572.17
monoclinic
C2/c
C20H16Se4
572.17
monoclinic
P21/n
C20H16Se4
572.17
monoclinic
P21/c
8
2
2
Unit cell dimensions
a [Å]
b [Å]
24.293(2)
5.2235(5)
30.239(3)
92.753(2)
3832.6(7)
1.98
8.057(1)
10.7377(5)
9.2932(4)
10.0453(5)
107.836(1)
954.22(8)
1.99
4.7364(6)
24.438(3)
98.151(2)
923.2(2)
2.06
7.95
needles
0.32ϫ0.06ϫ0.03
colorless
1.7 to 28.3
–10 Յ h Յ 10
–6 Յ k Յ 6
–32 Յ l Յ 32
8715
2306 (0.0407)
1963 [I Ͼ2σ(I)]
0.80/0.19
2306/0/141
1.05
c [Å]
β [°]
V [Å3]
Dcalcd. [g/cm3]
Absorption coefficient µ [mm–1]
Crystal shape
Crystal size [mm3]
Crystal colour
θ range for data collection [°]
Index ranges
7.66
7.69
polyhedron
0.20ϫ0.08ϫ0.05
colorless
1.7 to 28.3
–32 Յ h Յ 32
–6 Յ k Յ 6
–40 Յ l Յ 40
19112
4744 (0.0384)
3821 [I Ͼ2σ(I)]
0.70/0.31
4744/0/217
1.01
polyhedron
0.20ϫ0.11ϫ0.01
colorless
3.0 to 24.1
–12 Յ h Յ 12
–10 Յ k Յ 10
–11 Յ l Յ 11
6786
1512 (0.0785)
1105 [I Ͼ2σ(I)]
0.96/0.31
1512/0/109
1.10
Reflections collected
Independent reflections [R(int)]
Observed reflections
Max./min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
R(F)
0.029
0.058
0.55 and –0.41
0.026
0.056
0.83 and –0.43
0.052
0.093
0.89 and –0.54
RW(F2)
(∆p)max., (∆p)min. [eÅ–3]
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A. Lari, R. Gleiter, F. Rominger
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1,3-Bis(selenocyanatomethyl)benzene (8b): Starting materials: 5.3 g
(20.0 mmol) of 1,3-bis-bromomethylbenzene (7b) and 8.8 g
(60.8 mmol) potassium selenocyanate. The resulting residue from
the solvent removal was purified by silica-gel chromatography using
a mixture of n-hexane/diethyl ether (1:2), resulting in 4.2 g of 8b as
white solid (13.4 mmol, 67%). m.p. 108 °C. MS (EI+; m/z; %): 316
(0.9) [M]+; 210 (37.8) [M – SeCN]+; 116 (62.2) [M – 2SeCN]+; 104
(BP, 100) [M – C8H8]+; 78 (26.2) [C6H6]+; 51 (19.2) [M – C4H3]+.
843 (vs) 760 (s) 700 (m). HRMS (positive EI): calcd. for
12
C
18
1H2626Si280Se2 [M+], 457.9903; found, 457.9886 (–1.8 mmu).
1,3-Bis{[(trimethylsilyl)ethynylselenyl]methyl}benzene (9b): Starting
materials: 1.1 g (3.4 mmol) of 8b dissolved in 100 mL of THF;
5.23 mL (8.4 mmol) of n-butyllithium (1.6  inn-hexane) and 0.82 g
(8.35 mmol) of TMSA dissolved in 100 mL of THF. Chromatog-
raphy using a mixture of n-hexane and diethyl ether (12:1) afforded
1.0 g (66.2%) of 9b as yellow oil. MS (EI+; m/z; %): 458 [M]+ (1.1),
143 [C11H11]+ (40.9), 128 [C10H8]+ (29.0), 104 [C8H8]+ (31.2), 73
[Si(CH3)3]+ (BP,100.0). 1H NMR (500 MHz, CD2Cl2) δH = 0.15 [s,
18 H, Si(CH3)3], 4.00 (s, 4 H, CH2), 7.22–7.27 (m, 4 H, Harom
)
1H NMR (500 MHz, CD2Cl2): δH = 4.28 (s, 4 H, CH2), 7.34–7.41
(m, 4 H, Harom) ppm. 13C NMR (125 MHz, CD2Cl2): δC = 32.6 (2
C, s-CH2), 101.8 (2 C, t-CN), 129.5 (2 C, t-Carom), 129.8 (1 C, t-
Carom), 130.1 (1 C, t-Carom), 137.4 (2 C, q-Carom) ppm. 77Se NMR
ppm. 13C NMR (125 MHz, CD2Cl2) δC = 0.0 (6 C, p-CH3), 33.0
(2 C, s-CH2), 86.6 (2 C, q-SeC), 109.8 (2 C, q-SiC), 128.5 (2 C, t-
Carom), 129.0 (1 C, t-Carom), 129.5 (1 C, t-Carom), 138.7 (2 C, q-
Carom) ppm. 77Se NMR (95 MHz, CD2Cl2) δSe = 267.64 ppm. IR
(95 MHz, CD2Cl2): δSe = 294.55 ppm. IR (KBr): ν = 3444 (s), 2151
˜
(KBr): ν = 2958 (s), 2897 (w), 2087 (s), 1605 (w), 1487 (w), 1443
˜
(s), 1630 (m), 1486 (w), 1444 (m) cm–1.
12
(w). HRMS (positive EI): calcd. for
457.9903; found 457.9913 (+1.0 mmu).
C
18
1H2626Si280Se2 [M+],
1,4-Bis(selenocyanatomethyl)benzene (8c): Starting materials: 6.6 g
(25.0 mmol) of 1,4-bis-bromomethylbenzene (7c) and 10.8 g
(75 mmol) of potassium selenocyanate. The resulting residue from
the solvent removal was purified by silica-gel column chromatog-
raphy using a mixture of n-hexane/diethyl ether (1:2), resulting in
7.47 g of 8c as a yellowish solid (23.78 mmol, 95.1%) slightly light
sensitive. m.p: 138 °C. MS (EI+; m/z; %): 316 [M]+ (8.3), 210 [M –
SeCN]+ (74.8), 182 [C8H8Se]+ (4.2), 104 [C8H8]+ (BP, 100), 78
[C6H6]+ (7.2). 1H NMR (500 MHz, CD2Cl2): δH = 4.28 (s, 4 H,
CH2), 7.39 (s, 4 H, Harom) ppm. 13C NMR (125 MHz, CD2Cl2): δC
= 32.5 (2 C, s-CH2), 101.8 (2 C, q-SeC), 130.0 (4 C, t-Carom), 136.9
1,4-Bis{[(trimethylsilyl)ethynylselenyl]methyl}benzene (9c): Starting
materials: 5.0 g (16.0 mmol) of 8c dissolved in 300 mL of THF;
20.0 mL (32.0 mmol) of n-butyllithium (1.6  in n-hexane) and
3.1 g (32 mmol) TMSA dissolved in 350 mL of THF. Chromatog-
raphy using a mixture of n-hexane and diethyl ether (20:1) afforded
3.3 g (45.4%) of 9c as pale yellow crystals. m.p. 52–54 °C. MS (EI+;
m/z; %): 458 [M]+ (1.1), 442 [M – CH3]+ (0.7), 354 [C13H11Se2Si]+
(6.7), 281 [C13H17SeSi]+ (12.3), 162 [C4H6SeSi]+ (4.3), 143
[C11H11]+ (10.9), 128 [C10H8]+ (12.0), 104 [C8H8]+ (BP, 100), 73
1
[Si(CH3)3]+ (65.0). H NMR (500 MHz, CD2Cl2): δH = 0.15 [s, 18
(2 C, q-Carom
) =
ppm. 77Se NMR (95 MHz, CD2Cl2): δSe
H, Si(CH3)3], 4.01 (s, 4 H, CH2), 7.28 (s, 4 H, Harom) ppm. 13C
NMR (125 MHz, CD2Cl2): δC = 0.0 (6 C, p-CH3), 32.8 (2 C, s-
CH2), 86.7 (2 C, q-SeC), 109.8 (2 C, q-SiC), 129.4 (4 C, t-Carom),
307.10 ppm. IR (KBr): ν = 3428 (vb), 3048 (w), 3013 (w), 2955 (w),
˜
2147 (s), 2073 (s), 1630 (m), 1509 (m), 1425 (m) cm–1.
137.6 (2 C, q-Carom) ppm. 77Se NMR (95 MHz, CD2Cl2): δSe
=
General Procedure for the Preparation of the Bis(trimethylsilyl)di-
selenaalkadiynes 9a–c: In a four-necked flask, trimethylsilylacetyl-
ene (TMSA) was dissolved in anhydrous THF at –35 °C. At this
temperature n-butyllithium was added dropwise over a period of
20 min by using a syringe. Then the solution was stirred under the
same conditions for two hours. The diselenocyanatoxylene dis-
solved in anhydrous THF was added dropwise over a period of
45 min at –35 °C. After stirring for one hour at this temperature
the mixture was warmed up to room temperature. 50 mL of satu-
rated NH4Cl solution and 100 mL n-hexane were added. The aque-
ous layer was separated and extracted four times with n-hexane.
After combining the organic layers the mixture was dried with
MgSO4 overnight. The mixture was filtered, the solvent evaporated
and the resulting product was purified by silica-gel column
chromatography.
269.1 ppm. IR (KBr): ν = (≈ 3100–3600, s) , 3022 (w), 2957 (m),
˜
2899 (w), 2082 (s), 1636 (w), 1511 (m), 1419 (m), 1253 (s), 1247 (s),
1169 (s) cm–1. HRMS (positive EI): calcd. for
[M+], 457.9903; found 457.9929 (+2.5 mmu).
C
18
1H2626Si280Se2
12
General Procedure for the Preparation of the Diselenaalkadiynes
10a–c: To a solution of bis(trimethylsilyl)diselenaalkadiynes in
100 mL of anhydrous MeOH and 5 mL of anhydrous THF, in a
500 mL three-necked flask, the 0.1  NaOH solution was added
dropwise during a period of 15 min at room temperature. Then the
mixture was stirred for two hours. The reaction was stopped by
adding 150 mL of ice-water mixture and 150 mL of diethyl ether.
After separation of the organic layer the aqueous layer was ex-
tracted four times with 80 mL of diethyl ether. The combined or-
ganic layers were washed three times with saturated NH4Cl solu-
tion and three times with brine. After drying over MgSO4, the sol-
vent was evaporated and the product purified by silica-gel
chromatography.
1,2-Bis{[(trimethylsilyl)ethynylselenyl]methyl}benzene (9a): Starting
materials: 6.3 g (20 mmol) of 8a dissolved in 350 mL of THF,
25 mL (40 mmol) of nBuLi (1.6  in n-hexane) and 4 g (40 mmol)
of TMSA dissolved in 350 mL of THF. Chromatography using a
mixture of light petroleum and diethyl ether (20:1) afforded 5.8 g
of 9a (63.1%) as yellow-brown oil. MS (EI+; m/z; %): 458 [M]+
1,2-Bis(ethynylselenylmethyl)benzene (10a): Starting materials: 4.9 g
(10.8 mmol) of 1,2-bis{[(trimethylsilyl)ethynylselenyl]methyl}ben-
zene (9a) and 11 mL (1.1 mmol) 0.1  NaOH solution. Chromatog-
(Ͻ1), 427 [M – 2·CH3]+ (1.2), 264 [C8H8Se2]+ (2.3), 183 [C8H8Se]+ raphy on silica gel using a mixture of n-hexane/diethyl ether (6:1)
(13.6), 143 [C11H11]+ (40.9), 128 [C10H8]+ (29.0), 104 [C8H8]+
(31.2), 97 (28.5) [C5H9Si]+; 73 [Si(CH3)3]+ (BP, 100). 1H NMR
afforded 3.03 g (9.7 mmol, 90%) of 10a as yellow-brownish oil. MS
(EI+; m/z; %): 313 [M – H]+ (Ͻ1), 233 [C12H9Se]+ (11.3), 152
(500 MHz, CDCl3) δH = 0.15 [s, 18 H, Si(CH3)3], 4.21 (s, 4 H, [C12H8]+ (17.9), 128 [C10H8]+ (100.0), 104 [C8H8]+ (63.3), 78
CH2), 7.22 (m, 2 H, Harom), 7.27 (m, 2 H, Harom) ppm. 13C NMR [C6H6]+ (32.5). 1H NMR (500 MHz, CDCl3): δH = 2.90 (s, 2 H,
(125 MHz, CDCl3) δC = –0.1 [6 C, Si(p-CH3)3], 30.0 (2 C, s-CH2), CϵCH), 4.23 (s, 2JSe,H = 13.1 Hz, 4 H, CH2), 7.25 (m, 2 H, Harom),
86.1 (2 C, q-SeCϵCSi), 109.7 (2 C, q-SeCϵCSi), 128.0 (2 C, t- 7.31 (m, 2 H, Harom) ppm. 13C NMR (125 MHz, CDCl3): δC = 29.6
Carom), 131.1 (2 C, t-Carom), 135.5 (2 C, q-Carom) ppm. 77Se NMR
(2 C, s-CH2), 65.7 (2 C, t-CH), 90.1 (2 C, q-SeC), 128.2 (2 C, t-
(95 MHz, CDCl3) δSe = 250.17 ppm. IR (film): ν = 2958 (s) 2897
Carom), 131.1 (2 C, t-Carom), 135.3 (2 C, q-Carom) ppm. 77Se NMR
˜
(m) 2350 (w) 2087 (s) 1491 (w) 1262 (m) 1172 (m) 945 (w) 859 (vs)
(95 MHz, CDCl3): δSe = 229.14 ppm. IR (KBr): ν = 3277 (s), 3061
˜
2272
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2267–2274

Supramolecular Organization Based on van der Waals Forces
(w), 3020 (w), 2954 (w), 2028 (w), 1491 (m), 1452 (m), 1420 (w),
THF; 11 mL of nBuLi (1.6  in n-hexane, 18 mmols); 2.8 g
1376 (w), 1300 (w) cm–1. HRMS (positive EI): calcd. for (9 mmol) of 8a dissolved in 250 mL of anhydrous THF. The raw
12
C
12
1H980Se2 [M – H]+ 312.9035; found 312.9065 (+3.0 mmu).
product was purified using silica-gel chromatography. First, a mix-
ture of n-hexane and toluene (3:1) was used as eluent and an en-
riched fraction was further purified by chromatography using a
mixture of n-hexane and diethyl ether (10:1). Thin yellow needles
were recrystallized from CH2Cl2/n-hexane to give the final product
1,3-Bis(ethynylselenylmethyl)benzene (10b): Starting materials: 1.0 g
(2.1 mmol) of 1,3-bis{[(trimethylsilyl)ethynylselenyl]methyl}benzene
(9b) and 1.8 mL (0.2 mmol) 0.1  NaOH solution. Chromatog-
raphy on silica gel using a mixture of n-hexane and diethyl ether
(6:1) afforded 0.63 g (2.0 mmol, 95%) of 10b as yellowish oil. MS
(EI+; m/z; %): 313 [M – H]+ (0.4), 233 [C12H9Se]+ (15.1), 153
[C12H9]+ (11.8), 129 [C10H9]+ (49.5), 128 [C10H8]+ (BP, 100.0), 104
[C8H8]+ (43.0), 78 [C6H6]+ (28.0). 1H NMR (500 MHz, CD2Cl2):
4 (0.182 g, 0.32 mmol, 3.6% yield). 1H NMR (500MHz, CDCl3):
2
δH = 4.47 (s, JSe,H = 7.9 Hz, 8 H, CH2), 7.22 (br. s, 8 H, Harom
)
ppm. 13C NMR (125 MHz, CDCl3): δC = 33.0 (4 C, s-CH2), 85.9
(4 C, q-SeCϵCSe), 128.4 (4 C, t-Carom), 130.9 (4 C, t-Carom), 135.5
(4 C, q-Carom
) =
ppm. 77Se NMR (95 MHz, CDCl3): δSe
2
δH = 2.94 (s, 2 H, CϵCH), 4.04 (s, JSe,H = 14.9 Hz, 4 H, CH2),
235.04 ppm. IR (KBr): ν = 3100–3600 (s), 1772 (w), 1636 (m), 1559
˜
7.24–7.30 (m, 4 H, Harom) ppm. 13C NMR (125 MHz, CD2Cl2) δC
= 32.4 (2 C, s-CH2), 65.9 (2 C, t-CH), 90.3 (2 C, q-SeC), 128.5 (2
C, t-Carom), 129.2 (1 C, t-Carom), 129.7 (1 C, t-Carom), 138.5 (2 C,
q-Carom) ppm. 77Se NMR (95 MHz, CD2Cl2): δSe = 246.5 ppm. IR
(w), 1507 (w), 1490 (w), 1452 (w), 1419 (w), 1384 (w), 1249 (w)
12
cm–1. MS (LIFDI, ion mode FD+) calcd. for
573.79; found 573.60.
C
20
1H1680Se4 [M]+
(KBr): ν = 3277 (s), 3025 (w), 2939 (w), 2028 (m), 1604 (m), 1486
˜
2,5,14,17-Tetraselena[6,6]metacylophane-3,15-diyne (5): Starting
materials: 0.57 g (1.8 mmol) of 10b, dissolved in 300 mL of anhy-
drous THF, 2.25 mL (3.6 mmol) n-butyllithium (1.6  in n-hexane),
1
(m), 1443 (m) cm–1. HRMS (positive EI): calcd. for 12C12 H1080Se2
[M]+ 313.9113; found 313.9139 (+2.6 mmu).
1,4-Bis(ethynylselenylmethyl)benzene (10c): Starting materials: 3.0 g 0.57 g (1.8 mmol) of 8b dissolved in 300 mL of anhydrous THF.
(6.5 mmol) of compound 9c, 6.5 mL (0.7 mmol) of 0.1  NaOH Addition time was 7 hours. After warming up to room temp., the
solution, 300 mL of MeOH (solvent) and 15 mL of THF (cosol-
vent). The product was purified by silica-gel chromatography using
a mixture of n-hexane and diethyl ether (6:1), to give 1.95 g of pure
solvents were evaporated and the residue was filtered through sil-
ica-gel with toluene to remove salts and polymers. The raw product
was further purified using silica-gel chromatography with a mixture
10c (6.2 mmol, 95.8%) as pale yellow crystals. m.p. 77–79 °C. of n-hexane/toluene (4:1), and then an enriched fraction was fur-
MS (EI+; m/z; %): 314 [M]+ (0.1), 289 [C10H9Se2]+ (1.3), 209
ther purified by chromatography with a mixture of n-hexane/tolu-
ene (1:2). Finally, product 5 was separated by chromatography on
[C10H9Se]+ (12.1), 184 [C8H8Se]+ (1.4), 153 [C12H9]+ (6.8), 128
[C10H8]+ (16.4), 104 [C8H8]+ (BP, 100), 78 [C6H6]+ (21.0). 1H NMR silica-gel with a mixture of n-hexane/diethyl ether (5:1), obtaining
2
(300 MHz, CDCl3): δH = 2.89 (s, 2 H, CϵCH), 4.05 (s, JSe,H
=
0.076g of 5 (0.133 mmol, 7.4%) as thin colourless needles. 1H
14.2 Hz, 4 H, CH2), 7.30 (s, 4 H, Harom) ppm. 13C NMR (125 MHz, NMR (500 MHz, CD2Cl2): δH = 3.93 (s, JSe,H = 17.4 Hz, 8 H,
2
CDCl3): δC = 32.0 (2 C, s-CH2), 65.7 (2 C, t-CH), 89.9 (2 C, q-
CH2), 7.10–7.33 (m, 8 H, CHarom) ppm. 13C NMR (125 MHz,
SeC), 129.2 (4 C, t-Carom), 136.8 (2 C, q-Carom) ppm. 77Se NMR CD2Cl2) δC = 33.9 (4 C, s-CH2), 85.7 (4 C, q-SeC), 128.3 (2 C, t-
(95 MHz, CDCl3) δSe = 247.8 ppm. IR (KBr): ν = ca. 3100–3600
(s), 3262 (s), 3247 (m), 3052 (w), 2084 (w), 1636 (w), 1510 (w), 1419
Carom), 128.9 (1 C, t-Carom), 130.7 (1 C, t-Carom), 138.4 (2 C, q-
C
arom) ppm. 77Se NMR (95 MHz, CD2Cl2) δSe = 288.52 ppm. IR
˜
12
(w) cm–1. HRMS (positive EI): calcd. for
[M]+ 313.9113; found 313.9141 (+2.8 mmu).
C
1H1080Se2 (CD Cl ): ν = 3679 (bs), 3600 (m), 2930 (s), 2853 (m), 2371 (w),
˜
12
2 2
2335 (m), 1605 (s), 1487 (w), 1464 (w), 1442 (w), 1187 (m) cm–1.
1
MS (LIFDI, ion mode FD+) calcd. for 12C20 H1680Se4 [M]+ 573.79;
General Procedure for the Preparation of the Tetraselenacyclodiynes
4–6: To a solution of diselenaalkadiyne in anhydrous THF in a
three-necked flask, n-butyllithium (1.6  solution in n-hexane) was
added dropwise during 15 min, while maintaining the temperature
below –25 °C. The mixture was stirred for one hour at this tempera-
ture. To ca. 500 mL of anhydrous THF in a 2l three-necked flask,
cooled to –50 °C, the solutions of diselenocyanatoxylene and dili-
thiated diselenaalkadiynes in anhydrous THF were added simulta-
neously via separate dropping funnels over a time period of 6–7 h.
After complete addition the reaction mixture was warmed up to
room temperature overnight. The solvent was evaporated to give
the raw product which was cleaned by fast silica-gel chromatog-
raphy with toluene to remove salts and polymers. Further purifica-
tion was done using silica-gel chromatography with appropriate
solvent mixtures.
found 573.62.
2,5,14,17-Tetraselena[6,6]paracyclophane-3,15-diyne (6): Starting
materials: 0.78 g (2.5 mmol) of compound 10c in 250 mL of anhy-
drous THF, 3.1 mL (5.0 mmol) of n-butyllithium (1.6  in n-hex-
ane) and 0.78g (2.5 mmol) of compound 8c in 250mL of anhydrous
THF. Addition time was 5 hours. After warming up to room temp.
the solvents were evaporated and the residue was filtered through
silica-gel with toluene to remove salts and polymers. An enriched
fraction of the first column was used to purify the product, through
chromatography on deactivated silica-gel with n-hexane/diethyl
ether (5:1). After rotary evaporation of the solvents the product
was recrystallized from a mixture of dichloromethane and n-hex-
ane, resulting in 0.04 g of 6 (0.08 mmol, 1.8%) as thin colourless
crystals. 1H NMR (500 MHz, CD2Cl2): δH = 3.89 (s, JSe,H
=
2
Note: Melting points could not be determined for compounds 4–
6 because all samples decomposed upon heating in the 60–80 °C
range.
20.3 Hz, 8 H, CH2), 7.15 (s, 8 H, Harom) ppm. 13C NMR (75 MHz,
CD2Cl2): δC = 33.4 (4 C, s-CH2), 84.4 (4 C, q-SeC), 129.3 (8 C, t-
Carom), 138.4 (4 C, q-Carom) ppm. 77Se NMR (95 MHz, CD2Cl2):
δSe = 299.81 ppm. IR (CDCl ): ν = 3581 (w), 2957 (s), 2927 (s),
˜
3
Gas-chromatography of the compounds was unsuccessful, as they
decomposed.on the chromatographic column as well as in the
transfer line. Mass spectra could only be recorded using the LIFDI
(FD+) method and all compounds confirmed the calculated iso-
topic pattern.
2856 (m), 2241 (w), 1712 (w), 1650 (w), 1604 (w), 1557 (w), 1457
(m), 1366 (w), 1182 (m), 1017 (m) cm–1. MS (LIFDI, ion mode
12
FD+): calcd. for
C
20
1H1680Se4 [M]+ 573.79; found 573.67.
Supporting Information (see also the footnote on the first page of
this article): NMR spectra of synthesized compounds (S1–S12) and
2,5,14,17-Tetraselena[6.6]orthocyclophane-3,15-diyne (4): Starting
materials: 2.8 g (9 mmol) of 10a dissolved in 250 mL of anhydrous MS spectra of compounds 4–6 (S13–S14).
Eur. J. Org. Chem. 2009, 2267–2274
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2273

A. Lari, R. Gleiter, F. Rominger
FULL PAPER
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Acknowledgments
We are grateful to the Deutsche Forschungsgemeinschaft (DFG)
for financial support. A. L. thanks Mathias Reinmuth and Wolf-
gang Woiwode for preparative assistance and the Deutsche For-
schungsgemeinschaft for a graduate fellowship (GK850) and finan-
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Division, Madison, Wisconsin, 1997.
Received: January 30, 2009
Published Online: March 31, 2009
2274
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2267–2274