Regular acyclic and macrocyclic [AB] oligomers by formation of push-pull chromophores in the chain-growth step

Article abstract of DOI:10.1002/chem.201003672

The substrate scope of the [2+2] cycloaddition-cycloreversion (CA-CR) reaction between electron-deficient (2,2-dicyanovinyl)benzene (DCVB) or (1,2,2-tricyanovinyl)benzene (TCVB) derivatives and N,N-dimethylanilino (DMA)-substituted acetylenes was investigated. The structural features of the cyanobutadiene products of these transformations were examined and the rates of selected CA-CR reactions were measured. Rate constants for reactions utilizing pentafluorinated TCVB and DCVB were found to be one to two orders of magnitude larger than those for the unsubstituted analogues. Multiple, consecutive CA-CR reactions were performed with substrates incorporating two reactive 2,2-cyanovinyl or 4-ethynylanilino sites. 1,4-Bis(2,2-dicyanovinyl)-2,3,5,6- tetrafluorobenzene and 1,4-bis[(4′-dihexylamino)phenylethynyl]benzene were selected as suitably reactive monomers for the synthesis of regular [AB] oligomers wherein the push-pull chromophores were formed in the chain-growth step. Oligomers of two types were isolated: macrocyclic [AB]_n and open-chain B[AB]_n oligomers, with n≤4.

Full text of DOI:10.1002/chem.201003672

DOI: 10.1002/chem.201003672
Regular Acyclic and Macrocyclic [AB] Oligomers by Formation of Push–Pull
Chromophores in the Chain-Growth Step
Fabio Silvestri,[a] Markus Jordan,[a] Kara Howes,[a] Milan Kivala,[a]
Pablo Rivera-Fuentes,[a] Corinne Boudon,[b] Jean-Paul Gisselbrecht,[b]
W. Bernd Schweizer,[a] Paul Seiler,[a] Melanie Chiu,[a] and FranÅois Diederich*[a]
Dedicated to Professor Didier Astruc on the occasion of his 65th birthday
Abstract: The substrate scope of the
[2+2] cycloaddition–cycloreversion
(CA–CR) reaction between electron-
deficient (2,2-dicyanovinyl)benzene
(DCVB) or (1,2,2-tricyanovinyl)ben-
zene (TCVB) derivatives and N,N-di-
methylanilino (DMA)-substituted ace-
tylenes was investigated. The structural
features of the cyanobutadiene prod-
ucts of these transformations were ex-
amined and the rates of selected CA–
CR reactions were measured. Rate
constants for reactions utilizing penta-
fluorinated TCVB and DCVB were
found to be one to two orders of mag-
nitude larger than those for the unsub-
stituted analogues. Multiple, consecu-
tive CA–CR reactions were performed
with substrates incorporating two reac-
tive 2,2-cyanovinyl or 4-ethynylanilino
sites. 1,4-Bis(2,2-dicyanovinyl)-2,3,5,6-
tetrafluorobenzene and 1,4-bis[(4’-di-
hexylamino)phenylethynyl]benzene
were selected as suitably reactive mon-
omers for the synthesis of regular [AB]
oligomers wherein the push–pull chro-
mophores were formed in the chain-
growth step. Oligomers of two types
were isolated: macrocyclic [AB]n and
open-chain B[AB]n oligomers, with nꢀ
4.
Keywords: cycloaddition–cyclore-
version
· chromophores · cyclo-
phanes · donor–acceptor systems ·
oligomerization
Introduction
the push–pull chromophore products,[4,5] the reaction typi-
cally proceeds rapidly and with very good yields. These
properties stimulated us to explore the use of the CA–CR
transformation for the preparation of regular push–pull olig-
omers, which may ultimately lead to the synthesis of poly-
mers and dendrimers.
Nonplanar, p-conjugated, donor–acceptor chromophores
that feature low-energy charge-transfer (CT) absorptions
are attractive materials for nonlinear optical and photonic
applications.[1] One particularly efficient method for access-
ing these chromophores is a formal [2+2] cycloaddition–cy-
cloreversion (CA–CR) reaction between electron-rich al-
kynes, such as N,N-dialkylanilino (DAA)-substituted acety-
lenes, and electron-deficient alkenes, such as tetracyanoe-
thene (TCNE), yielding nonplanar donor-substituted cyano-
buta-1,3-dienes that feature intense, bathochromically
shifted, intramolecular CT bands.[2,3] Apart from the excel-
lent optoelectronic performance and demonstrated utility of
One possibility for accessing push–pull-chromophoric
polymers by means of the CA–CR transformation has been
reported by Michinobu and co-workers: polymers are syn-
thesized with donor-activated acetylene moieties either in
the main chain or laterally appended; these acetylene moiet-
ies subsequently undergo reaction with tetracyanoethene
(TCNE) as a post-polymerization modification.[6] Another,
hitherto unexplored possibility for accessing regular [AB]
oligomers utilizing this reaction enables the formation of
push–pull chromophores in the chain-growth step. Such an
approach can be realized if both monomers, A and B, are
able to participate in multiple, consecutive CA–CR reac-
tions.[7] Recently, weaker acceptors, such as 2,2-dicyanovinyl-
benzene (DCVB) and 1,2,2-tricyanovinylbenzene (TCVB)
derivatives were found to be capable of undergoing the
CA–CR reaction in high yields and with complete diastereo-
selectivity.[8] This discovery prompted us to explore the use
[a] Dr. F. Silvestri, Dr. M. Jordan, Dr. K. Howes, Dr. M. Kivala,
P. Rivera-Fuentes, Dr. W. B. Schweizer, P. Seiler, Dr. M. Chiu,
Prof. Dr. F. Diederich
Laboratorium fꢀr Organische Chemie, ETH Zꢀrich
Hçnggerberg, HCI, 8093 Zꢀrich (Switzerland)
Fax : (+41)44-632-1109
E-mail: diederich@org.chem.ethz.ch
[b] Prof. Dr. C. Boudon, Dr. J.-P. Gisselbrecht
Laboratoire dꢁElectrochimie et de Chimie Physique
du Corps Solide, Institut de Chimie
of bis(dicyanovinyl)benzene (bis
ACHTUNGTNER(NUNG DCV)) and bis(tricyanovi-
UMR 7177, C.N.R.S., Universitꢂ de Strasbourg
4, rue Blaise Pascal, CS 90032
67081 Strasbourg Cedex (France)
nyl)benzene (bis(TCV)) derivatives as A monomers in the
AHCTUNGTRENNUNG
synthesis of [AB] oligomers (Scheme 1).
Because a high-yielding and facile chain-growth step is
imperative to access oligomers, and eventually longer poly-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201003672.
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FULL PAPER
To quantify whether the rates of CA–CR reactions with
electronically activated acceptors are accelerated, kinetic
studies were undertaken. We were particularly interested in
the reactivity of pentafluorinated compounds 1b and 2b be-
cause reactions utilizing these compounds provided the best
compromise between high yields and short reaction times.
DCVBs 1a and 1b or TCVBs 2a and 2b were treated with
DMA-acetylene 3 in (CDCl2)2 at 228C and the transforma-
tions were monitored by 1H NMR spectroscopy (Table 1).
Table 1. Kinetic data from 1H NMR spectroscopy of CA–CR reactions
with unsubstituted and fluorinated DCVBs and TCVBs.[a]
Scheme 1. Formation of [AB] oligomers by using the CA–CR reaction to
install push–pull chromophores in the chain-growth step. X and Y can be
a variety of spacers; Alk is an alkyl chain.
mers, we initiated our studies with a series of model reac-
tions and kinetic studies designed to determine the degree
to which the DCVB or TCVB acceptors should be activated
to attain optimal reactivity. X-ray crystallographic studies on
the cyanobutadiene products of these model reactions sug-
gest that the reactions proceed through a highly torquoselec-
tive, cyclobutene-opening step. Subsequently, donors and ac-
ceptors incorporating two reactive sites were shown to un-
dergo multiple, consecutive CA–CR reactions. Finally, we
translated the findings from these model studies to the syn-
thesis of a new class of regular acyclic and macrocyclic [AB]
oligomers.
Entry
1[b]
2
3
4
DCVB/TCVB
Product
kobs [mÀ1 sÀ1
5.67ꢄ10À5
]
t1/2 [min]
1a Ar=Ph
1b Ar=F5Ph
2a Ar=Ph
5a
5b
6a
6b
8790
(1.78Æ0.08)ꢄ10À2
(8.45Æ0.38)ꢄ10À4
(1.28Æ0.06)ꢄ10À2
26.8Æ1.6
589Æ24
42.7Æ2.4
2b Ar=F5Ph
[a] Unless otherwise noted, reported values are the averages of three in-
dependent measurements; reported errors represent standard deviations.
Initial concentration of all reagents was 0.032m in (CDCl2)2 with hexame-
thylbenzene (0.011m) as an internal standard; reactions were performed
at 228C. [b] Reaction was performed once; reported values are extrapo-
lated from initial rate measurement in which the reaction was followed
to 25% conversion.
Results and Discussion
All reactions exhibited overall second-order behavior (see
Figures S26–33 in the Supporting Information for detailed
Model studies for identifying an A monomer: To identify
the optimal acceptor motif for the A monomer to be used in
the targeted oligomerization reactions (Scheme 1), a series
of aryl-substituted DCVBs (1) and TCVBs (2) were pre-
pared (see the Supporting Information). Their conversions
in the CA–CR reaction with N,N-dimethylanilino- (DMA-)
substituted terminal (3) and internal (4) acetylenes to afford
donor-substituted cyanobutadienes 5–8 were investigated
(see Scheme 2 and Table S1 in the Supporting Information
for details). In contrast to reactions utilizing unsubstituted
analogues 1a and 2a (for depiction, see Table 1), reactions
using DCVBs and TCVBs that included electron-withdraw-
ing substituents on the aryl ring (e.g., 1b–d and 2b–d) were
uniformly high yielding.
kinetic data and linear fits).[8b] While the rate constant (kobs
)
for the reaction using fluorinated DCVB 1b was ((1.78Æ
0.08)ꢄ10À2)mÀ1 sÀ1, the rate constant for transformation of
unsubstituted DCVB 1a was more than two orders of mag-
nitude smaller (kobs =(5.67ꢄ10À5)mÀ1 sÀ1). Similar behavior
was observed in the TCVB systems: kobs =((1.28Æ0.06)ꢄ
10À2) and ((8.45Æ0.38)ꢄ10À4)mÀ1 sÀ1 for the reactions utiliz-
ing perfluorinated TCVB 2b and unsubstituted TCVB 2a,
respectively. It is noticeable that the third vinylic CN group
in the TCVBs either inhibits or does not markedly facilitate
conversion compared with reactions utilizing DCVBs
(Table 1, entry 1 vs. 3 and entry 2 vs. 4). The increased elec-
tronic activation in the TCVBs is presumably mitigated by
increased steric bulk; previous mechanistic studies indicate
that the free enthalpy of activation (DG°) of the first [2+2]
cycloaddition step is strongly increased by steric hindran-
ce.[8b]
Characterization of DMA-substituted di- and tricyanobuta-
1,3-dienes: X-ray crystallographic studies performed on
single crystals of several cyanobutadiene products (for
ORTEP plots, see Figures S34–45 in the Supporting Infor-
mation) revealed two significant results: 1) the configuration
of the TCVB-derived cyanobutadiene products was elucidat-
ed and 2) a correlation between steric bulk and effective
Scheme 2. CA–CR reactions of DCVBs and TCVBs with DMA-activated
terminal and internal alkynes. Solvent
= 1,1,2,2-tetrachloroethane or
N,N-dimethylformamide.
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F. Diederich et al.
conjugation within the cyanobutadiene products was estab-
lished. The CA–CR reactions of TCVBs with both terminal
and internal DMA-substituted alkynes, such as those utiliz-
ing DCVBs,[8] yielded one diastereoisomer exclusively. Crys-
tal structures of these products show that the aryl ring (from
the TCVB precursor) and the dicyanovinyl moiety are trans
oriented (6b and 8c in Figure 1; for 6a, see Figure S39 in
the Supporting Information); this configuration is consistent
with that observed for DCVB-derived cyanobutadienes
(e.g., 5b, 5d, 7b, and 7c in Figures S37, 38, 42 and 43, re-
spectively, in the Supporting Information).[8] These crystal
structures constitute the first examples of donor-substituted
tricyanobuta-1,3-dienes derived from TCVB precursors. The
diastereoselectivity of this reaction testifies to the high tor-
quoselectivity with which the cyclobutene intermediate
opens.[9]
The structural parameters summarized in Table 2 show a
correlation between steric bulk and conjugation within the
cyanobutadiene monoadducts. With increasing steric bulk
about the butadiene moiety, the dihedral angle q, defined by
the butadiene moiety (C4-C3-C5-C6, Table 2), increases.
Thus, values of q are smallest for cyanobutadienes 5b
(18.9(4)8) and 5d (13.4(3)8) (Table 2, entries 1 and 2), which
are formed from the terminal alkyne 3 and DCVBs 1b or
1d. More significant deviations from planarity, up to q=
77.0(7)8 (6b, entry 4), are found in the products obtained
from the reaction of TCVBs 2a–d and/or internal alkyne 4
(entries 4–9).
Figure 1. ORTEP representations of the molecular structures of 6b (top,
220 K) and 8c (bottom, 123 K). Thermal ellipsoids are shown at the 50%
probability level. Hydrogen atoms are omitted for clarity and atoms are
numbered arbitrarily. For selected bond lengths and angles, see the Sup-
porting Information.
Increasing values of q generally correlate to decreasing
values of f, the dihedral angle (C1-C2-C3-C4, Table 2) de-
fined by the two vinylic C atoms of the dicyanovinyl (DCV)
moiety and the two adjacent CACHTNUGRTNEUNG
(sp2) atoms of the DMA
moiety. Thus, increasing steric bulk about the butadiene
moiety appears to induce the DMA and DCV moieties to
approach coplanarity. These
increasing conjugation and CT within cyanobutadiene chro-
mophores.
moieties are, in turn, responsi-
Table 2. Dihedral angles and bond-length alternation parameters from X-ray crystal structures for DMA-sub-
stituted cyanobutadiene chromophores.
ble for the intramolecular CT in
the chromophores,[2f] which is
manifested in the solid state as
bond-length alternation within
the aniline rings (dr, see Table 2
for definition).[10] In sterically
encumbered 7b, dr is relatively
strong
(0.041 ꢅ,
Table 2,
entry 6) in comparison with
5b (dr=0.023 ꢅ) and 5d
(dr=0.016 ꢅ) (Table 3, en-
tries 1 and 2). This large dr
value in 7b is consistent with
more efficient conjugation be-
tween the DMA and DCV moi-
eties, which is enabled by a rel-
Entry
Compound
Ar
R
R’
q [8][a]
f [8][b]
dr [ꢅ][c]
1
2
3
4
5
6
7
8
9
5b
5d
6a
6b
7a
7b
7c
7d
8c
F5Ph
4-CF3-Ph
Ph
F5Ph
Ph
H
H
CN
CN
H
H
H
H
CN
H
H
H
H
Ph
Ph
Ph
Ph
Ph
18.9(4)
13.4(3)
50.1(2)
77.0(7)
56.8(2)
74.6(6)
70.0(2)
67.0(3)
70.9(4)
48.7(4)
47.0(3)
37.5(2)
4.0(10)
26.9(3)
26.4(5)
28.5(3)
26.6(3)
28.7(5)
0.023
0.016
0.039
0.03
0.042
0.041
0.035
0.037
0.039
F5Ph
4-CN-Ph
4-CF3-Ph
4-CN-Ph
atively small value of
f
(26.4(5)8). Putting these trends
together, increasing steric bulk
[a] q is the dihedral angle defined by C4-C3-C5-C6. [b] f is the dihedral angle defined by C1-C2-C3-C4.
[c] dr={[(a+a’)/2-(b+b’)/2]+[(c+c’)/2-(b+b’)/2]}/2; for benzene, dr=0.00 ꢅ; for fully quinoid rings, dr=
about
the
cyanobutadiene
moiety ultimately translates to 0.08–0.12 ꢅ.
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Acyclic and Macrocyclic Oligomers
FULL PAPER
Table 3. Consecutive CA–CR reactions starting from 9 with two DAA-activated internal acetylenes.
providing, in most cases, very
good yields of corresponding
bisadducts 14a, 14b, 15a, and
15b in short reaction times (see
Table 4, entries 1 and 4). Be-
cause the push–pull chromo-
phore formed in the first addi-
tion remains a potent electron
acceptor,[2] the monoadduct is
sufficiently activated for the
second addition step. The reac-
tion of 3 and 13a to form bisad-
duct 15a was monitored by
1H NMR spectroscopy (see Fig-
ure S25 in the Supporting Infor-
mation): after 20 h at 1008C,
50% conversion to the inter-
mediate monoadduct and 45%
conversion to the bisadduct
Entry
DCVB/TCVB
Solvent
Product
t [h]
Yield [%]
1
2
3
1b (3 equiv)
1c (4 equiv)
2b (3 equiv)
DMF[a]
DMF[a]
TCE[b]
10
11
–
18
22
24
37
98
–
[a] [9]=0.01m. [b] [9]=0.04m.
The UV/Vis and electrochemical properties of the new cy-
anobutadiene monoadducts obtained from these model stud-
ies are reported in the Supporting Information.
Consecutive CA–CR model studies: The reactivities of com-
pounds with either two DAA-acetylene- or two DCV-/TCV-
(tricyanovinyl-) reactive sites were evaluated. When
bis(DAA-acetylene) derivative 9 was treated with excess
pentafluorinated DCVB 1b (3 equiv), the expected bisad-
duct was formed, but the reaction did not proceed to com-
pletion (Table 3). Formation of the monoadduct was ob-
1
served by H NMR spectroscopy, but the resulting deactiva-
tion of the second alkyne rendered the second addition very
slow. Bisadduct 10 was only isolated in 37% yield after 18 h
(DMF, 1008C). In contrast, a p-CN substituent on the
phenyl ring of DCVB 1c did not seem to influence the
second addition to the same extent: bisadduct 11 was isolat-
ed in 98% yield. Its structure was confirmed by X-ray analy-
sis (Figure 2) and indicated that the absolute torquoselectivi-
ty of the cyclobutene-ring-opening step is maintained in
multiple-adduct formations: the 4-cyanophenyl and the di-
cyanovinyl moieties are trans oriented with respect to the
C4=C5 double bond. Each of these reactions yields the
product as only a single diastereomer. UV/Vis spectroscopy
and electrochemical data for bisadducts 10 and 11 are in-
cluded in the Supporting Information (Figure S50 and
Table S2, respectively). In the reaction utilizing TCVB 2b,
only monoadduct and no desired bisadduct were obtained.
The additional CN group deactivates the remaining, directly
p-conjugated acetylene bond in the monoadduct, rendering
it inert to further reaction.
Figure 2. ORTEP representation of the molecular structure of 11 in the
crystal (123 K). Thermal ellipsoids are shown at the 50% probability
level. Hydrogen atoms and minor occupations of disordered atoms (C31
and C32) are omitted for clarity and atoms are numbered arbitrarily. Se-
À
À
lected bond lengths [ꢅ] and dihedral angles [8]: C23 C24 1.411(5), C24
À
À
À
C25 1.377(5), C25 C20 1.408(6), C20 C21 1.399(5), C21 C22 1.383(5),
À
À
À
À
C22 C23 1.419(6), C20 C14 1.455(5), C14 C15 1.378(6), C14 C4
1.482(5), C4 C5 (1.346(5), C4 C3 1.490(4), C5 C6 1.465(5); C3-C4-C5-
C6 À11.4(6), C5-C4-C14-C15 À46.8(5), C15-C14-C20-C21 À37.2(5).
À
À
À
Both non-[11] and tetrafluorinated bis(2,2-dicyanovinyl)-
benzene (12a and 12b, respectively) and bis(1,2,2-tricyano-
vinyl)benzene derivatives (13a and 13b) (see the Supporting
Information for the synthesis of 12b and 13b) underwent
two, consecutive CA–CR reactions with DMA-acetylene 3,
were observed, in addition to trace amounts of the starting
material.
These data show that bis-additions to both bis(DAA-
alkyne) and bisACTHNUGRTENNUG(DCV) or bisAHCTUNGTRENN(UGN TCV) substrates are possible,
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F. Diederich et al.
Table 4. Consecutive CA–CR reactions starting from 1,4-bis(2,2-dicyanovinyl)- and bis(1,2,2-tricyanovinyl)-
benzene derivatives.
Signals in the NMR spectra
of the major product, [AB]2 oli-
gomer 16b, were sharp at room
temperature and were indica-
tive of a molecule with appar-
ent D2h symmetry. These obser-
vations led us to postulate that
16b was macrocyclic in struc-
ture. To test this hypothesis, we
treated 16b with a further two
equivalents of DCVB 1b under
the oligomerization reaction
conditions; no reaction was ob-
served by MALDI-TOF mass
spectrometry, which was consis-
tent with a cyclic structure that
did not contain free, reactive
acetylene groups. When B[AB]1
oligomer 17a was treated with
Entry
Cyanoolefin
Solvent
Product
t [h]
Yield [%]
1
2
3
4
12a R’=H
12b R’=F
13a R’=H
13b R’=F
DMF
DMF
TCE
TCE
14a[a]
14b[a]
15a[b]
15b[a]
5
15
72
1
86
70
94
95
[a] [Cyanoolefin]=0.02m. [b] [Cyanoolefin]=0.006m.
with the DCV derivatives performing better than the TCV
derivatives in many cases, presumably due to a combination
of steric and electronic effects.
Synthesis, isolation, and characterization of [AB] oligomers:
BisACHTUNGTRENNUNG(DCV) derivative 12b (A, see Scheme 3) was reacted
with bis(DAA-alkyne) derivative 9 (B) in TCE at 808C. The
transformation was monitored by using MALDI-TOF mass
spectrometry. Consumption of the 1,4-bis(phenylethynyl)-
benzene starting material, 9, and concomitant formation of
a mixture of oligomeric products (Scheme 3) were observed.
The signals in the mass spectrum of the crude product mix-
ture correspond to m/z values that are consistent with prod-
ucts of three general formulae: [AB]n (16a–d) and B[AB]n
(17a–d), in which n=1–4, as well as A[AB]n (18), in which
n=1–3 (see Figure S52 in the Supporting Information for
the mass spectrum of the crude reaction mixture). Recycling
gel permeation chromatography (GPC) was performed to
separate the components of the product mixture (for their
mass spectra, see the Supporting Information). Samples of
[AB]n (n=2–4) and B[AB]n (n=1–4) oligomers were isolat-
ed with [AB]2 oligomer 16b
Scheme 3. CA–CR oligomerization reaction between 12b (monomer A,
see Scheme 1) and 9 (monomer B) in TCE. Reaction conditions: [9]=
0.02m in TCE, 12b (1 equiv). Unoptimized yields are reported.
DCVB 1b, however, consumption of starting material was
1
observed by H NMR spectroscopy, suggesting that 17a pos-
sessed an open-chain connectivity.
procured, by far, as the major
product (21%). The second-
most-abundant compound iso-
lated was B[AB]1 oligomer 17a
(2%). These two major isolated
products were fully character-
ized by NMR spectroscopy (1H,
13C, and 19F; see the Supporting
Information). Interestingly, the
reaction of 9 with bisACTHUNTGRENNG(U TCV) de-
rivative 13b did not afford any
higher oligomeric products and
only formation of a monoad-
duct was observed.
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Chem. Eur. J. 2011, 17, 6088 – 6097

Acyclic and Macrocyclic Oligomers
FULL PAPER
versible protonation–deprotonation experiments (see Fig-
ure S51 in the Supporting Information). When B[AB]1 oligo-
mer 17a was treated with excess trifluoroacetic acid (TFA),
the two lower-energy absorption bands at about 380 and
470 nm disappeared. Subsequent addition of triethylamine
to the sample resulted in the reappearance of both absorp-
tion bands. Thus, both absorption bands can be ascribed to
intramolecular CT in the B[AB]n oligomers. To distinguish
the two CT interactions from one another, TFA (0.4 equiv)
was added to B[AB] oligomer 17a, causing only the absorp-
tion band at around 380 nm to disappear. Because the anili-
no moieties that are conjugated to the alkyne unit are more
basic than those adjacent to the DCV groups, the absorption
band at about 380 nm can be attributed to an intramolecular
CT from the DAA-acetylene to the adjacent DCV moiety.
In [AB]2 oligomer 16b, only one type of DAA moiety is
present, and the protonation–deprotonation experiments
identified only the strong absorption maximum at around
470 nm as a CT band.
Computational studies corroborated the proposed connec-
tivity of [AB]2 oligomer 16b and yielded insight into its elec-
tronic structure (see the Experimental Section for details).
A simplified analogue of the proposed cyclic oligomer 16b,
wherein the hexyl chains on the aniline nitrogen atoms were
replaced with methyl groups, was subjected to conforma-
tional analysis. A global minimum was identified and further
optimized at the B3LYP/6-31G(d) level of theory (see Fig-
ure S60 in the Supporting Information). This conformation
is C2 symmetric. However, all aromatic rings rotate freely
according to molecular dynamics simulations, leading to a
higher pseudo-symmetry that is consistent with the experi-
mental NMR spectrum of 16b. Furthermore, the UV/Vis
spectrum of 16b was simulated by using the structure of the
calculated global minimum, wherein vertical excitations
were simulated at the time-dependent (TD) CAM-B3LYP/
6-31G(d) level of theory. Good agreement between the si-
mulated and experimental spectra of 16b (see Figure S61 in
the Supporting Information) further supports the proposed
macrocyclic structure of that compound. The calculated UV/
Vis spectrum of acyclic B[AB]1 oligomer 17a (see Fig-
ure S62 in the Supporting Information) also agrees with its
experimental spectrum, which validates the use of these cal-
culations for predicting the connectivity of the oligomers.
Finally, the origin of the single CT absorption band ob-
served in the UV/Vis spectrum of cyclic [AB]2 oligomer 16b
was elucidated by molecular orbital calculations. The highest
occupied molecular orbitals (HOMO-3 to HOMO) for
cyclic oligomer 16b include two pairs of degenerate orbitals
centered on the four aniline rings (Figure 4a and b). This
degeneracy lends further credence to the proposed cyclic
structure of 16b because an open-chain structure is of lower
symmetry and such degeneracy would not be possible. Fur-
thermore, the fact that these four HOMO orbitals are close
in energy is consistent with the unique four-electron oxida-
tion at +0.74 V observed in the cyclic voltammogram of 16b
(see Figure S46 in the Supporting Information). The elec-
tron density of the calculated first four virtual orbitals
Figure 3. UV/Vis spectra of a) cyclic [AB]n and b) acyclic B[AB]n oligo-
mers isolated from the CA–CR oligomerization of 9 and 12b (CH2Cl2,
298 K).
The UV/Vis spectra of 16b and 17a, as well as the isolat-
ed higher-order [AB]n and B[AB]n oligomers provided fur-
ther insight into the structures of these compounds
(Figure 3). The longest-wavelength maxima in both series
appear at about 470 nm and do not change with oligomer
length. The homology between the UV/Vis spectra of 16b
and the higher-order [AB]n oligomers, 16c and 16d, suggests
that these compounds are possibly all cyclic in structure.
Additionally, the molar extinction coefficients in the [AB]n
oligomers do not increase with increasing oligomer size. The
larger compounds become more fluxional, as evident from
the broadness of the signals in the NMR spectra. Analo-
gously, the similarities between the UV/Vis spectra of 17a
and the higher-order B[AB]n oligomers suggest that these
compounds are of an open-chain connectivity. Whereas the
absorption strengths of all compounds in the [AB]n series
are similar (Figure 3a), the molar extinction coefficients of
the three absorption bands in the B[AB]n oligomers de-
crease with increasing oligomer length (Figure 3b). We spec-
ulate that this strong hypochromicity might arise from
arene–arene interactions in a helical or folded conformation
in these oligomers.[12] Two additional observations are con-
sistent with this tentative hypothesis: 1) the sharpness of all
three absorption bands remains constant, and 2) bisadduct
11 possesses a bent “H” structure in the solid state
(Figure 2).
The CT character of the longest-wavelength absorptions
of the [AB]n and B[AB]n oligomers was demonstrated in re-
Chem. Eur. J. 2011, 17, 6088 – 6097
ꢃ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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6093

F. Diederich et al.
active sites, respectively, led to the formation of two types of
oligomers with [AB]n or B[AB]n constitutions. Experimental
results suggested that the B[AB]n oligomers were open-
chain structures, whereas the [AB]n oligomers were macro-
cyclic structures. Further support for the macrocyclic struc-
ture of the [AB]2 oligomer was obtained by computational
investigations, which also showed that the observed intramo-
lecular CT in this systems arose from electron donation
from the peripheral dialkylanilino rings to the electron-defi-
cient macrocycle. Future studies will be directed toward
controlling the product distribution of the oligomerization
reaction and exploring the supramolecular chemistry of the
macrocyclic oligomers, which have been obtained by seren-
dipity rather than by design. After further improving the re-
activity of the monomeric starting materials by optimization
of electronic and structural properties, new polymers and
dendrimers should also become accessible.
Experimental Section
Figure 4. Representations of selected calculated molecular orbitals of
cyclic [AB]2 oligomer 16b. a) HOMO; b) HOMO-3; c) LUMO.
Materials and general methods: Reagents and solvents were purchased at
reagent grade from Acros, Aldrich, and Fluka, and used as received.
Compound 3 was commercially available. Compounds 1a,[8a] 1b,[13] 1c,[14]
1d,[15] 2a,[13] 2b,[13] 4,[16] 5a,[8a] 5c,[8b] 9,[2b] 12a,[11] and 13a[11] were synthe-
sized according to literature procedures. The syntheses of compounds 2c,
2d, 12b, and 13b are described in the Supporting Information. General
procedures for the [2+2] CA–CR and oligomerization reactions, as well
as representative examples of these reactions, are given below; the syn-
theses and characterization data for compounds 5b, 5d, 6a, 6b, 7a–d,
8a–d, 11, 14a, 14b, 15a, 15b, and oligomers 16c, 16d and 17a–d are de-
scribed in the Supporting Information. All reactions were performed in
standard glassware under a positive pressure of Ar. TLC analysis was
conducted on aluminum sheets coated with SiO2 60 F254 obtained from
Macherey–Nagel and visualized by UV irradiation (254 or 366 nm). Flash
column chromatography (FC) was performed with SiO2 60 (particle size
0.040–0.063 mm, 230–400 mesh ASTM; Fluka) or SiO2 60 (particle size
0.063–0.200 mm, 70–230 mesh ASTM; Merck) and distilled technical sol-
vents. Preparative TLC was performed by using SiliaPlate preparative
plates (SiliCycle, 20ꢄ20 cm, thickness=1000 mm). Melting points were
measured on a Bꢀchi B-540 melting-point apparatus in open capillaries
and are uncorrected. 1H, 13C, and 19F NMR spectra were recorded on
Varian Gemini 300, Bruker DRX 400, Bruker DRX 500, or Bruker DRX
600 spectrometers at 298 K. Chemical shifts (d) are reported in ppm rela-
tive to tetramethylsilane (TMS); the residual solvent peak was used as an
internal reference. Coupling constants (J) are given in Hz. Apparent res-
onance multiplicities are described as s (singlet), brs (broad singlet), d
(doublet), t (triplet), q (quartet), and m (multiplet). IR spectra were re-
corded on a Perkin–Elmer BX FT-IR spectrometer; signal designations:
s (strong), m (medium), w (weak). All spectra were measured by using
neat samples. UV/Vis spectra were recorded on a Varian Cary 500 spec-
trophotometer. The spectra were measured in CH2Cl2 in a quartz cuvette
(LUMO to LUMO+3) is delocalized over the entire cyclo-
phane macrocycle with coefficients extending to the dicya-
novinyl substituents (Figure 4c). Thus, the CT absorption
band in the UV/Vis spectrum of cyclic oligomer 16b arises
from electron donation from the four anilino rings to the
electron-accepting cyclophane macrocycle.
Conclusion
A series of model investigations enabled the identification
of suitably reactive monomers, 12b (A) and 9 (B), for the
formation of regular [AB] oligomers by using the CA–CR
reaction. In this novel oligomerization, nonplanar, push–pull
buta-1,3-dienes with intense intramolecular CT interactions
are formed in the chain-growth step. The use of pentafluori-
nated TCVB or DCVB substrates enables rate enhance-
ments of 16- to 280-fold in the CA–CR reaction compared
with reactions utilizing the non-fluorinated analogues; this
facile reactivity was essential for obtaining oligomers. As
shown in model reactions utilizing substrates containing
either two cyanoolefin or two alkyne moieties, tricyanoole-
fins are less reactive than their dicyanovinyl counterparts;
presumably, disfavorable steric effects negate the beneficial
electron-withdrawing effects of the third CN group. Addi-
tionally, X-ray crystallographic studies enabled a detailed
analysis of the influences of steric bulk on both molecular
conformation and the efficiency of the intramolecular
donor–acceptor conjugation in nonplanar donor-substituted
cyanobuta-1,3-dienes.
(1 cm) at 298 K. The absorption maxima ACHTNUTRGNE(UNG lmax) are reported in nm with
the extinction coefficient (e [mÀ1 cmÀ1]) in parentheses; shoulders are in-
dicated as sh. Preparative recycling GPC was performed on a Japan Ana-
lytical Industries LC-9101 preparative recycling HPLC apparatus
equipped with a Jaigel-2H column, using CHCl3 (ReagentPlus grade,
ꢁ99.8%) as the mobile phase, with a flow rate of 4 mLminÀ1. Mass spec-
trometry was performed by the MS Service at ETH Zꢀrich. High-resolu-
tion (HR) electron ionization (EI) mass spectra were measured on a
Waters Micromass Auto-Spec Ultima spectrometer. HR matrix-assisted
laser-desorption (MALDI) mass spectra were measured on a Varian Ion-
Spec Ultima MALDI-FTICR mass spectrometer with 3-hydroxypyridine-
2-carboxylic acid (3-HPA) as the matrix or on a Bruker Daltonicx Ultra-
CA–CR oligomerization between optimized monomers, A
and B, which contain two DAA-acetylene and two DCV re-
6094
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Chem. Eur. J. 2011, 17, 6088 – 6097

Acyclic and Macrocyclic Oligomers
FULL PAPER
flex II MALDI-TOF mass spectrometer using 2-[(2E)-3-(4-tert-butyl-
phenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) as matrix. Iso-
tope signals with the highest relative abundance are reported. Elemental
analyses were performed by the Mikrolabor at the Laboratorium fꢀr Or-
ganische Chemie, ETH Zꢀrich, with a LECO CHN/900 instrument. The
fluorine content was estimated by ion chromatography on a Metrohm
761 Compact IC instrument. In samples in which the presence of residual
solvent was indicated by elemental analysis, its presence and identity was
confirmed by 1H NMR spectroscopy. Compound names were generated
by using ACD/Lab 6.0 software (Advanced Chemistry Development).
X-ray crystal structure of 6a: C21H16N4; Mr =324.38; monoclinic; space
group P21/n; 1calcd =1.223 gcmÀ3; Z=4, a=7.5396(11), b=10.5438(12),
c=22.3962(15) ꢅ; a=90.00, b=98.277(11), g=90.008; V=1761.86 ꢅ3 at
220(2) K. Orange cut fragment (linear dimensions ca. 0.21ꢄ0.18ꢄ
0.17 mm). Number of measured and unique reflections: 6537 and 3596,
respectively (Rint =0.0287). Final R(F)=0.0489, wR(F2)=0.1095 for 229
parameters and 3596 reflections with I>2s(I) and 1.84<q<28.388.
X-ray crystal structure of 6b: C21H11F5N4; Mr =414.337; orthorhombic;
space group P212121; 1calcd =1.524 gcmÀ3
; Z=4; a=6.4708(2), b=
14.0247(5), c=19.9010(10) ꢅ; a=90.00, b=90.00, g=90.008; V=
1806.04(12) ꢅ3 at 173 K. Amber plate (linear dimensions ca. 0.36ꢄ0.27ꢄ
0.027 mm). Number of measured and unique reflections: 3079 and 3063,
respectively (Rint =0.062). Final R(F)=0.1095, wR(F2)=0.3100 for 274
parameters and 3063 reflections with I>2s(I) and 2.753<q<25.0288.
General procedure for rate measurements: A 1-dram scintillation vial
was charged with a solution of 3 (3.5 mg, 0.024 mmol) and hexamethyl-
benzene (1.3 mg, 0.0080 mmol) in (CDCl2)2 (0.75 mL). A given acceptor
source (1a (3.7 mg), 1b (5.9 mg), 2a (4.3 mg), or 2b (6.5 mg),
0.024 mmol) was added to this solution as a solid and dissolved. The re-
sulting solution was then immediately transferred to an NMR tube.
Single-scan 1H NMR spectra were recorded at varying intervals (5–
120 min) for the first 12 h on a Varian Gemini 300 spectrometer at 298 K.
X-ray crystal structure of 7a: C26H21N3; Mr =375.475; monoclinic; space
group P21/n; 1calcd =1.209 gcmÀ3; Z=4; a=13.2760(4), b=9.4253(3), c=
16.7739(4) ꢅ; a=90.00, b=100.509(2), g=90.008; V=2063.71(10) ꢅ3 at
123 K. Dark yellow cube (linear dimensions ca. 0.18ꢄ0.18ꢄ0.15 mm).
Number of measured and unique reflections: 8832 and 4704, respectively
(Rint =0.065). Final R(F)=0.0524, wR(F2)=0.1402 for 264 parameters
and 4704 reflections with I>2s(I) and 2.753<q<27.4858.
1
For the reactions using 1b, 2a, and 2b, the collection of H NMR spectra
continued for seven half-lives; the reaction using 1a was monitored to
25% conversion over 96 h.
Computational methods: All optimizations, frequency calculations, and
vertical electronic transitions were calculated by using the Gaussian 09
program package.[17] Conformational analysis was performed by using a
mixed Monte Carlo Multiple Minimum/Low-Mode Conformational
Search method and the OPLS95 force field as implemented in MacroMo-
del 9.7. All conformers with energies less than 3 kcalmolÀ1 relative to the
global minimum were manually examined. Seven structures were selected
for further optimization by using DFT at the B3LYP/6-31G(d) level of
theory. This refinement yielded five conformers; harmonic vibrational
analysis of these conformers performed at the same level of theory con-
firmed that all structures are minima of the potential energy surface.
However, the global minimum was found to represent about 95% of the
conformations in a Boltzmann distribution at 298.15 K. The UV/Vis spec-
trum of 16b was simulated by using the structure of the global minimum.
100 vertical electronic transitions were computed at the TD CAM-
B3LYP/6-31G(d) level of theory.
X-ray crystal structure of 7b: C26H16F5N3; Mr =465.425; triclinic; space
group P1; 1calcd =1.436 gcmÀ3; Z=2; a=9.4718(7), b=10.0314(7), c=
¯
12.5863(10) ꢅ;
a=69.866(3),
b=83.756(3),
g=73.520(4)8;
V=
1076.60(14) ꢅ3 at 123 K. Amber cube (linear dimensions ca. 0.21ꢄ0.12ꢄ
0.075 mm). Number of measured and unique reflections: 4953 and 2822,
respectively (Rint =0.108). Final R(F)=0.0697, wR(F2)=0.1668 for 309
parameters and 2822 reflections with I>2s(I) and 2.753<q<22.9868.
X-ray crystal structure of 7c: C27H20N4; Mr =400.485; triclinic; space
group P1; 1calcd =1.237 gcmÀ3; Z=2; a=8.6684(4), b=10.3124(5), c=
¯
13.4632(7) ꢅ;
a=76.954(2),
b=88.910(2),
g=66.933(2)8;
V=
1075.46(9) ꢅ3 at 123 K. Amber plate (linear dimensions ca. 0.165ꢄ
0.066ꢄ0.048 mm). Number of measured and unique reflections: 8540 and
3329, respectively (Rint =0.066). Final R(F)=0.0555, wR(F2)=0.1676 for
360 parameters and 4912 reflections with I>2s(I) and 2.753<q<
27.4858.
X-ray crystal structure of 7d: C27H20F3N3, Mr =443.472; triclinic; space
group P1; 1calcd =1.331 gcmÀ3; Z=2; a=8.4794(3), b=10.6526(4), c=
¯
X-ray analysis: Unless otherwise noted, single crystals of indicated com-
pounds were obtained by layering Me2SO on top of a solution of the in-
dicated compound in CH2Cl2 and allowing slow diffusion between the
two layers at 228C. ORTEP diagrams of all compounds for which X-ray
data was collected can be found in the Supporting Information. X-ray
data collection was carried out on a Bruker KappaCCD diffractometer
13.5062(5) ꢅ; a=87.982(2), b=79.5732(14), g=67.358(2)8; V=
1106.57(7) ꢅ3 at 173 K. Pale yellow plate (linear dimensions ca. 0.36ꢄ
0.24ꢄ0.039 mm). Number of measured and unique reflections: 8868 and
5047, respectively (Rint =0.052). Final R(F)=0.0634, wR(F2)=0.1962 for
378 parameters and 5047 reflections with I>2s(I) and 2.753<q<
27.4858.
equipped with
a graphite monochromator (MoKa radiation, l=
0.71073 ꢅ) and an Oxford Cryostream low-temperature device. Cell di-
mensions were obtained by least-squares refinement of all measured re-
flections (HKL, Scalepack[18a]), qmax =27.58. All structures were solved by
direct methods (SIR97[18b]). All non-hydrogen atoms were refined aniso-
tropically, hydrogen atoms were refined for compounds 1d, 2c, 4b, 4d,
7c, and 7d isotropically by full-matrix least-squares with SHELXL-97[18c]
using experimental weights (1/[s2(Io)+(Io +2Ic)2/900]). For compounds
2b, 5a, 5b, 7a, 7b, 8c, and 11, hydrogen positions were calculated and in-
cluded in the structure factor calculation.
X-ray crystal structure of 8c: Single crystals were obtained by layering
hexanes on top of a solution of 8c in tetrahydrofuran and allowing slow
diffusion between the two layers at 228C. C28H19N5·C4H8O; Mr =497.602;
monoclinic; space group P21/n; 1calcd =1.253 gcmÀ3; Z=4; a=12.2364(5),
b=11.4908(5), c=18.8308(9) ꢅ; a=90.00, b=94.870(2), g=90.008; V=
2638.2(2) ꢅ3 at 123 K. Red plate (linear dimensions ca. 0.22ꢄ0.18ꢄ
0.03 mm). Number of measured and unique reflections 8518 and 4779, re-
spectively (Rint =0.060). Structure contains a disordered THF molecule in
the asymmetric unit. Two atoms were refined over two positions. Final
R(F)=0.0906, wR(F2)=0.2419 for 342 parameters and 4779 reflections
with I>2s(I) and 2.425<q<25.3508.
X-ray crystal structure of 5b: C20H12F5N3; Mr =389.327; monoclinic; space
group P21/n; 1calcd =1.516 gcmÀ3; Z=4; a=12.2399(8), b=6.5379(5), c=
21.348(2) ꢅ; a=90.00, b=93.111(4), g=90.008; V=1705.8(2) ꢅ3 at
123 K. Red brown needle (linear dimensions ca. 0.27ꢄ0.06ꢄ0.03 mm).
Number of measured and unique reflections: 5711 and 2992, respectively
(Rint =0.093). Final R(F)=0.0638, wR(F2)=0.1559 for 301 parameters
and 2992 reflections with I>2s(I) and 2.753<q<25.0288.
X-ray crystal structure of 11: C68H74N8; Mr =1003.396; triclinic; space
group P1; 1calcd =1.160 gcmÀ3; Z=1; a=10.8650(4), b=11.4737(4), c=
¯
13.1850(2) ꢅ; a=111.005(2), b=92.055(2), g=108.345(2)8; V=
1435.8(9) ꢅ3 at 123 K. Colorless cube (linear dimensions ca. 0.21ꢄ0.15ꢄ
0.09 mm). Number of measured and unique reflections 8868 and 4701, re-
spectively (Rint =0.066). Two atoms of a hexyl chain are disordered and
were refined over two positions. Final R(F)=0.0842, wR(F2)=0.2251 for
365 parameters and 3634 reflections with I>2s(I) and 2.753<q<
24.4078.
X-ray crystal structure of 5d: C21H16F3N3; Mr =367.374; monoclinic; space
group P21/c; 1calcd =1.321 gcmÀ3; Z=4; a=9.3457(4), b=8.1316(4), c=
24.5171(12) ꢅ; a=90.00, b=97.609(2), g=90.008; V=1846.8(2) ꢅ3 at
123 K. Colorless plate (linear dimensions ca. 0.18ꢄ0.06ꢄ0.03 mm).
Number of measured and unique reflections: 4352 and 2501, respectively
(Rint =0.08). Final R(F)=0.0526, wR(F2)=0.1379 for 308 parameters and
2501 reflections with I>2s(I) and 2.425<q<22.9868.
CCDC-802597 (5b), 802598 (5d), 802596 (6a), 802599 (6b), 802600 (7a),
802601 (7b), 802602 (7c), 802603 (7d), 802604 (8c), and 802605 (11) con-
tain the supplementary crystallographic data for this publication. These
Chem. Eur. J. 2011, 17, 6088 – 6097
ꢃ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6095

F. Diederich et al.
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General procedure for [2+2] CA–CR reactions: A solution of DAA-ac-
tivated alkyne and electron-deficient olefin (DCVB, TCVB, or 1,4-di-
vinylbenzene derivative) in DMF was stirred at 1008C until complete
conversion was observed by LC-MS. The solvent was evaporated, and the
crude residue was washed with Et2O. Purification by FC afforded the de-
sired product.
2,2’-{1,4-Phenylenebis[(1E)-3-[4-(dimethylamino)phenyl]-1-(pentafluoro-
phenyl)-1-propen-2-yl-3-ylidene]} dimalononitrile (10): By using the gen-
eral procedure, 1b (25 mg, 0.10 mmol) and 9 (22 mg, 0.034 mmol) were
stirred in DMF (2.5 mL) for 18 h. FC (SiO2; toluene/hex 95:5) afforded
10 as a black solid (14 mg, 37%). Rf =0.86 (SiO2; CH2Cl2); m.p. 241–
2438C; 1H NMR (300 MHz, CD2Cl2): d=0.88 (t, J=6.7 Hz, 12H), 1.29
(brs, 24H), 1.47–1.66 (m, 8H), 3.32 (t, J=15.6 Hz, 8H), 6.60 (d, J=
9.4 Hz, 4H), 6.58 (s, 2H), 6.93 (s, 4H), 7.69 ppm (d, J=9.3 Hz, 4H);
13C NMR (75 MHz, CD2Cl2): d=14.2, 23.0, 27.0, 27.4, 31.9, 51.5, 78.9,
110.3–111.2 (m), 111.4, 115.0, 115.8, 119.0, 120.7, 128.4–129.2 (m), 128.8,
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137.5, 137.8 (dm, 1J(C,F)=255.3 Hz), 144.2 (dm, 1J
ACHTUNGTRENNUNG ACHTUNTGREN(NUGN C,F)=248.1 Hz),
145.8, 146.0, 152.4, 170.3 ppm; 19F NMR (282 MHz, CD2Cl2): d=À137.1
to À137.4 (m), À153.0 (t, J=20.1 Hz), À161.1 to À161.4 ppm (m); IR
(ATR): n˜ =2925 (m), 2213 (m), 1599 (s), 1518 (m), 1491 (s), 1436 (m),
1412 (m), 1381 (m), 1335 (m), 1293 (m), 1178 (s), 975 (s), 909 (m), 821
(m), 704 (w), 636 cmÀ1 (w); UV/Vis (CH2Cl2): lmax (e)=284 (31300), 348
(28500), 462 nm (53900mÀ1 cmÀ1); HR-MALDI-MS (3-HPA): m/z calcd
for C66H67F10N6+: 1133.5262; found: 1133.5278 [M+H]+; elemental analy-
sis calcd (%) for C66H66F10N6 (1133.27): C 69.95, H 5.87, N 7.42; found: C
70.12, H 6.06, N 7.23.
General procedure for synthesis of oligomers: Compounds 12b (A)
(100 mg, 0.155 mmol) and 9 (B) (46.9 mg, 0.155 mmol) were dissolved in
TCE (10 mL) and the resulting mixture heated to 808C for 48 h. After
cooling the mixture to room temperature, the solvent was removed and
the residue was subjected to FC (SiO2; CH2Cl2/EtOAc 99:1). The frac-
tions containing oligomers were then subjected to recycling GPC (Jaigel-
2H; CHCl3) to afford the [AB]2 oligomer 16b as the major product
(32 mg, 21%), as well as small amounts of other oligomers, ranging from
B[AB]1 to B[AB]4. [AB]2 ACHTNUTRGENUNG
(16b): m.p. 124–1268C; 1H NMR (600 MHz,
CDCl3): d=0.88–0.92 (m, 24H), 1.28–1.36 (m, 48H), 1.56–1.63 (m, 16H),
3.30–3.36 (m, 16H), 6.51 (s, 4H), 6.59 (d, J=9.5 Hz, 8H), 7.21 (s, 8H),
7.73 ppm (d, J=9.3 Hz, 8H); 13C NMR (151 MHz, CDCl3): d=14.1, 22.8,
26.8, 27.4, 31.7, 51.4, 74.1, 111.6, 114.9, 116.0, 119.8, 120.3, 129.2, 133.5,
137.7, 143.8, 144.9, 145.4, 152.4, 171.5 ppm; 19F NMR (377 MHz, CDCl3):
d=À136.2 ppm (s); IR (ATR): n˜ =2926 (m), 2855 (m), 2214 (m), 1598
(w), 1536 (w), 1479 (s), 1410 (s), 1365 (m), 1332 (s), 1289 (s), 1199 (m),
1177 (s), 975 (s), 855 (m), 817(s), 735 (m), 676 cmÀ1 (m); UV/Vis
(CH2Cl2): lmax (e)=288 (72000), 461 nm (129900mÀ1 cmÀ1); MALDI-
TOF-MS (DCTB): m/z (%): 1822 (65), 1823 (93), 1824 (61), 1825 (26),
[7] For the electronically controlled formation of regular oligomers by
sequential CA–CR of electron-poor TCNE and electron-rich tetra-
thiafulvalene (TTF) to polyynes, see: a) M. Kivala, C. Boudon, J.-P.
Gisselbrecht, P. Seiler, M. Gross, F. Diederich, Angew. Chem. 2007,
119, 6473–6477; Angew. Chem. Int. Ed. 2007, 46, 6357–6360;
b) B. B. Frank, M. Kivala, B. Camafort Blanco, B. Breiten, W. B.
Schweizer, P. R. Laporta, I. Biaggio, E. Jahnke, R. R. Tykwinski, C.
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1831 (78), 1832 (100) [MÀ
(C6H12)+Na]+, 1833 (63), 1834 (23), 1893 (49),
ACHTUNGTRENNUNG
1894 (61) [M+H]+, 1895 (45), 1896 (22); HR-MALDI-MS (3-HPA) m/z
calcd for C120H133F8N12+: 1894.0643; found: 1894.0663 [M+H]+.
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Acknowledgements
Funding from an ERC Advanced Grant (“OPTELOMAC”) is gratefully
acknowledged. M.C. thanks the ETH Research Council for an ETH fel-
lowship.
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Received: December 20, 2010
Revised: February 2, 2011
Published online: April 18, 2011
Chem. Eur. J. 2011, 17, 6088 – 6097
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www.chemeurj.org
6097