1. No category

PDF hosted at the Radboud Repository of the Radboud University
Nijmegen
The following full text is a publisher's version.
For additional information about this publication click this link.
http://hdl.handle.net/2066/16536
Please be advised that this information was generated on 2015-01-12 and may be subject to
change.
COMMUNICATIONS
Construction of a Multiwired Molecular Cable
of Micrometer Length by a Self-Assembly
Process**
Cornelus F. van Nostrum, Stephen J. Picken, and
Roeland J. M. Nolte*
The engineering o f m olecules and m olecular system s that can
form nanom eter-sized structures is currently receiving a great
deal o f a tten tion .1' ~ 31 A n interesting challenge is the construc­
tion o f m olecular w ires and m olecular channels capable o f
transporting electrons and ions. F or exam ple, phthalocyanines
substituted w ith long hyd rocarbon side chains have been report­
ed to form con d u ctin g m esoph ases in w hich the m olecules are
stacked in colum ns. E lectron condu ction within the colum ns is
fast, w hereas it is slo w betw een the colu m ns.14,51 In previous
papers w e have sh ow n that crow n ether m olecules can be
stacked to create ion con d u ctin g chann els.16,71 H ere we describe
a novel liquid-crystalline m olecule (I) that sell-assem bles in
chann els built up from stacked cro w n eth er rings and a sur­
r ou n d in g hyd rocarbon m antle. Iso la te d cab les w ith m olecu lar
thickness and a length o f several m icrom eters can be recognized
in electron m icroscop y im ages.
P h th alocyan in e 1 w as prepared from cro w n ether 12 by a
cyclization reaction (see Schem e 1). T h e crow n ether w a s syn ­
thesized from I I , w h ich in turn w as a ssem b led from the bu ild in g
b locks 6 and 10. The starting com p ou n d for 6 w as 3,4-dihydro xybenzaldehyde (2). T his com poun d w as alkylated with decyl
no.
HO'
J
e
HO. ^
XX
\b
RO,
^Br
HO'
Br
/—wO —\Cl I, f
2THP0
RO'
I
: :xx
A ~ \/-\
HO
1°
fl° Y Y °
HO
Br
Br
10
n^
1^0^
n
C
1
^-0 0-^
-o
I'
o-
XX ° °XX'
HO.
12
RO'
Dr. S. J. Picken
AKZO Research Laboratories, Arnhem (The Netherlands).
[**] Tltis research was financially supported by the Dutch Innovatie-gericht Onder­
zoekprogramma (IOP) o f (he Ministry of Economic Affairs. We thank R. van
Puijenbroek (AKZO) for carrying out the SAXS measurements.
AngeII’ . Chem. Int. Eel. Engl. 1994, 33, Nu. 21
\_ /w
CN
I'
chloroform solu tion to form a m olecular cable. This cable c o n ­
tains a central wire o f stacked p h thalocyan ines, four m olecular
[’’■] Prof, Dr. R. .1. M. Nolte, C, F. van Nostrum
Department o f Organic Chemistry, NSR Center
University o f Nijmegen
NL-6525 ED Nijmegen (The Netherlands)
Telefax; Int. code + (80)553450
CN
Scheme 1. R =
a) DMF, iiC,„H31Br (2.1 equiv), K 2C 0 3 (2.2 equiv), N 3 ,
16 h (84%); b) Cl-ICi,/McOH (1/1, v/v), I-I,02 (0.75 equiv), H 2S 0 4 (0.2 equiv), 5 h
(65%); c) THF/HjO (2.7:1, v/v), K.(S03),N Q (2.5 equiv), K H ,P 0 4 (0.6 equiv),
Bu4N f Ci" (0.4 equiv), 2 h (80% ); d) A c0 H /A c20 (1/1, v/v), reflux, Zn (4cquiv),
reflux, 30 min. (88%); e) CCI4, Br, (2 equiv), 0 “C -»room temperature (R T), 16 h
(91 %); f) //BuOH, NaOH (2 equiv), C lCH,CH2OCH_,CH2OTHP (2 equiv), N a,
reflux, 1 6 h, HC1 (2.1 equiv), RT, I h (49%); g) pyridine, /jTosCI (2.4equiv),
- 1 0 ° C , 2 h, RT, 16 h (93% ); h) 6, «BuOH. NaOH (2.5 equiv), N ,, renux, 10
(1 equiv), reflux, 16 h (58%); i) DMF/pyridine (200:1, v/v), CuCN (3 equiv), N ,,
reflux, 40 h; subsequently, N H 40 H /H 20 , 0 2,2 h (75% ); j) (C H 3)jN C H 2CH2OH,
reflux, 40 h (30%).
© VCH Verlagsgesellschaft m b ll , D-69451 Wemheim, 1994
0570-083319412121-2173 $ 10.00 + .25/0
2173
COMMUNICATIONS
b rom id e (-» 3) and su b seq u e n tly con verted into 3,4-b is(d ec o x y )p h e n o l (4) b y a B a e y e r - V illiger typ e o f o x id a tio n .[8] Treat­
m en t o f th e p h en ol w ith F re m y ’s r a d ic a l^ 1un d er ph ase transfer
c o n d itio n s yielded 4 ,5 -b is(d e c o x y )-1 ,2 -b e n z o q u in o n e (5), w h ich
was co n v erted in to l,2 -b is (a c e to x y )-4 ,5 -b is(d e c o x y )b e n z c n e (6;
for ch aracterization see T ab le 1) b y red u ction w ith zin c/
acetic acid /a cetic anh ydride. T h e o v era ll yield o f 6 from 2 w as
m etal-free p h thalocyan ines. H ow ever, w h en this so lu tio n was
cooled to room tem perature a blue shift o f the bands and a
broadening o f the signals w as observed, w hich is characteristic
o f aggregated phthalocyan ine species (F ig. 1).
Table 1. Characteristic physical data o f I, 6, and 10.
1: IR (CI-IClj): v = 3294 (N H ), 2925, 2853 (C H ,), 1603, 1529, 1413 (Ar), 1490,
1391,1369.1101 (phtlnilocyanine), 1 2 8 0 (A rO ), 1134(COC), 1022(N H ),863 cm - '
(ArH); 'H N M R (400 MHz, CDC1,, 5 3 °C): <5 = 6.64 (s, 8H, ArH), 3 . 6 - 4 . 9 (m,
80H, C H jO ), 1 .2 -1 .8 (m, 128H, C H ,), 0.89 (s. 24H, C H ,); elemental analysis;
C„l8H 25„N B0 3,.CHCl.,; calcd C 67.36", H 8.40, N 3.72, found C 67.18, H 8.28, N
3.74%
6: [R ( K B r ) : F = 2800-3100 (C H ,, C H ,, A rH ), 1760 (C = O), 1605, 1510 (Ar),
1230, 1180 c m ' 1 (CArO); '11 N M R (100 M Hz, C D C !,):fi = 6.68 (s, 2H, A rH ), 3.94
(t, 4H, C H jO ), 2.26 (s, 611, C H aC = O ), 1.2 -1 .9 (m, 32H, C H ,), 0.88 (t, 6H, CH.,);
MS (Cl): hi/-: 506
elemental analysis: C ,nH 50OfJ: calcd C 71.11, H 9.95,
found C 71.42, H 9.82%
10: IR (CHC13): f = 2800 3100 (C H „ A rH ), 1350,1170 (SO.,), 1245, 1190 (C AtO),
655 cm “ 1 (ArBr); ‘H NMR (100 MHz, CDCI.,): <5 = 7 .1 3 -7 .8 5 (m, 8H, A rH ), 7.03
(s, 2H, ArH ), 3 .6 -4 .2 5 (m, IfiH, C H2), 2.38 (s, 6H, CH.,); MS (FAB): m /z: 752
[M + +1]
38 % . T h e syn thesis o f the se c o n d b u ild in g b lock 10 w a s per­
form ed u sin g m ore stan d ard rea c tio n s. C a te ch o l (7) w as b rom inated an d su b seq u en tly a lk y la te d w ith tetrah yd rop yran yl(T H P )-p rotected d ie th y len eg ly c o l m o n o c h lo r id e to give, after in
situ d e p r o te ctio n , c o m p o u n d 9. R e a c tio n o f 9 w ith p -to lu en esu lfonyl ch lorid e gave c o m p o u n d 10 a s a h ig h ly v isc o u s oil in 42 %
overall yield (Table 1). T h e c o u p lin g o f the tw o fragm ents was
carried o u t b y first h y d ro ly zin g 6 an d su b seq u en tly trea tin g the
resultin g ca tech o la te in situ w ith 10. T h e tw o b ro m in e a to m s o f
11 w ere su bstitu ted b y nitrile g r o u p s w ith co p p e r cy a n id e in
7V,7V-dim ethylfonnam ide ( D M F ) . F in a lly , th e resultin g crow n
ether 12 w a s con verted in to p h th a lo c y a n in e 1 by reflu xin g in
A^.TV-dimethylaminoethanol (o v e ra ll y ield fr o m 6 an d 10 13% ).
C o m p o u n d 1 w as pu rified by rep eated recrystallization from
ch lo ro fo rm . S p ectro sco p ic a n d e le m en ta l an a ly sis w ere c o n sis­
tent w ith the p r o p o sed stru ctu re (T ab le 1).
C row n ether p h th a lo cy a n in e 1 sh o w e d th erm o tro p ic liquid
crystallin e beh avior as w as ev id en t from d ifferen tial scann in g
calorim etry (D S C ), p o la r iz in g m ic r o sc o p y , a n d sm all an g le X ray sca tterin g (S A X S ) m ea su rem en ts. A tran sition to a highly
v isc o u s, birefringent m e so p h a se w a s ob served at 148 °C o n h eat­
ing ( A N = : 1 3 0 k J m o ] ~ l ). L arge h ysteresis w a s o b serv ed on
c o o lin g : the transition to th e c ry sta llin e p h a se occu rred at
105 °C . N o tran sition to the iso tr o p ic p h a se w a s observed below
the d e c o m p o sitio n tem p eratu re o f th e c o m p o u n d (320 °C ). The
large n u m b er o f p ea k s in th e S A X S m easu rem en ts at room
tem p erature in d icated a c ry sta llin e ph ase. In the m esop h ase
at 170 °C an in ten se p eak , c o rr e sp o n d in g to a sp a cin g o f
35.10 A, an d a very b road p e a k , c o r r e sp o n d in g to 4.5 A, were
visible. T h e form er p ea k p r o b a b ly is the (1 0 0 ) reflection o f a
h e x a g o n a l colu m n ar p h ase w ith a n in terco lu m n a r d istan ce o f
40.5 A.
G en erally, alk o x y - an d c ro w n -eth er -su b stitu te d p h th alocyanin es are high ly so lu b le in o r g a n ic so lv e n ts. S u rp risin gly, 1 was
on ly so lu b le in b o ilin g c h lo r o fo r m an d in b o ilin g to lu en e. A
so lu tio n o f 1 (at a c o n c e n tr a tio n o f 7 m g r a L " 1 or m ore) in
ch lo ro fo r m form ed a gel o n c o o lin g . A U V /V is sp ectru m o f a
dilute so lu tio n (11 (im ) o f 1 in c h lo r o fo r m at 50 °C s h o w e d a split
Q -b a n d at 660 and 7 0 0 n m th a t is typ ical fo r non aggregated
2174
© VCH Verlagsgesellschafl mbH, 0-69451 Weinheim, 1994
X [n m ] ------Fig. 1. UV/Vis spectra of 1 in chloroform { 11 jam)
at
25 (:C (----- ) and 50 "C (—
).
The structure o f the aggregates w as elucidated w ith the help
o f transm ission electron m icroscop y (T E M ). C om p ou n d 1
(7 m g) w as boiled in ch loroform (1 m L ), and after the solution
had c o o led , a drop o f the resulting gel w as placed on a carboncoated copper grid. A fter one m inute the grid w as blotted dry
and shadow ed w ith platinum at an angle o f a p p roxim ately 45°.
Two representative T E M pictures are sh ow n in Figure 2. A t low
Fig. 2. Transmission electron micrographs o f a gel of 1 in chloroform. A): Isolated
single strands and bundles o f parallel strands of 1. B): Magnification showing
individual strands of molecules 1, which have diameters of 60 A.
m agnifications fibers with a length in the order o f m icrom eters,
w hich form a netw ork structure, are observed. A t higher m agni­
fications these fibers are seen to con sist o f b u nd les o f single
parallel strands. The thickness o f these strands equals the di­
am eter o f a m olecule o f 1 as estim ated from C P K space-filling
m olecular m odels, that is, 5 0 - 6 0 A. Several isolated strands
can be observed w ith the sam e diam eter. A t low er concentra­
tions o f 1 in chloroform , th at is, below the gel-form in g point,
fibers are still present, but they are sm aller, and n o netw ork is
form ed.
T he con clu sion from these experim ents is th at crow n ether
p h thalocyan ine 1 self-assem bles in to extrem ely lo n g stacks o f
m olecular thickness, w h ich con sist o f m ore than 104 m olecules,
To the b est o f our k n ow led ge, evidence for the form ation o f such
large p h thalocyan ine aggregates has n ot been reported before.
A p parently, the attractive forces betw een the m olecu les are so
strong that com plete solvation is prevented at ro o m tem pera-
0570-0833/94/2121-2174 $ 10.00+.25/0
Angnv. Chem, Int. Ed. Engl. 1994, 33, No. 21
COMMUNICATIONS
50-60 A _
ture. A s shown schem ati­
cally in Figure 3 a stack
o f m olecules 1 can be
considered to be a m ulti­
wired m olecular cable.
In view o f its structural
resem blance
to
the
crow n-ether-substituted
phthalocyanine
poly­
m ers previously studied
by us,[7J it is reasonable
to postulate that the
- - 'i s o l a t in g m a n tle
m olecular cable is capa­
ble o f condu cting ions
— io n c h a n n e ls
and electrons.
Apart
e le c tr o n w ire
from that, the transition
o f I from the solid state
Fig. 3. Schematic representation o f the
to the m esophase is
multiwired molecular cable formed by
self-assembly o f crown ether phthalocyaprobably accom panied
nine 1. In the mesophase the individual
by a change in electronic
molecules probably rotate around their
and ionic conductive
stacking axis (see ref. [10]).
properties. We are cur­
rently investigating this
in detail, as w ell as the p olym erization o f the dihydroxysilicon
derivative o f 1 to give a polym erized m olecular cable.
c a n n o t form stab le m etal c o m p lex e s. T h e g o a l o f our research
w ork is the synthesis o f m a cro cy cles th a t h ave on ly a few flu o ­
rine a to m s in corp orated in to the cyclic stru ctu re. U p o n co m plexation o f m etal ions, the flu orin e sh o u ld act as a “ d e te cto r ” ,
since the 19F N M R sig n a ls sh ift u p o n c o m p le x a tio n .131 T h e high
sensitivity, com b in ed w ith a large sign al d isp er sio n and the a b ­
sence o f a natural background m a k e U)F N M R sp ectro sco p y an
ideal to o l for in v e stig a tio n /41
R ecen tly we reported the sy n th esis o f a p artially flu orin ated
[2.2.2]cryptand.t51 T his c o m p o u n d form s c o m p lex e s w ith m etal
ions; how ever, the 19F N M R sig n a ls sh ift o n ly slightly u p on
com p lexation , since n o direct m e ta l- flu o r in e con tacts are
form ed. Such an in teraction b eco m es m ore lik ely if a carb on fluorine b o n d is directed to w a r d s the cen ter o f the crow n ether.
The relatively sm all steric d em a n d o f th e flu orin e a to m is n o t
expected to interfere w ith th e b in d in g o f m e ta l ions; o n the
contrary it is h op ed th at fo r m a tio n o f a cr-donor bond betw een
fluorine and the m etal io n w ill in crease th e sta b ility o f the m etal
com plexes.
T h e building b lock u sed fo r th e sy n th e sis o f th e flu o rin e-co n ­
taining m acrocycles w as 1,3 -b is(b r o m o m eth y l)-2 -flu o r o b e n z en e
(1), w h ich w as treated w ith te tr a e th y len eg ly c o l, eth ylen eglycol,
or azacrow n ethers to y ield flu o r o cr o w n ethers (Schem e 1 ).[6]
Received: March 26, 1994
Revised version: June 21, 1994 [Z6799IE]
German version: A/igetr. Chan. 1994, 106, 2298
[1] G. M. Whitesides, X P. Mathias, C. T. Seto, Science 1991. 254, 1312.
[2] J.-M. Lchn, Angcw. Chem. 1990, 102,1347; Angew. Client. Int. Ed. Engl. 1990,
29, 1304.
[3] A. Murada, J. Li, M. Kamachi, Nature 1993, 364, 516.
[4] J. Simon, P. Bassoul in Phthuhcycinines, Properties and Applications, Vol. 2
(Eds.: C. C. Leznoff, A. 13. P. Lever), VCH, New York, 1993, pp. 223-299.
[5] P. G. Schouten, J. M. Warman, M. P. de Haas, J. F. van der Poi, J, W. Zwikker.
J. Am. Chem. Sac. 1992, 114, 9028.
[6] M. F. M. Roks, R. J. M. Nolle, Macromoleatlcs 1992, 25, 5398.
[7] Ö. E, Sielcken, L. A. van de Kuil, W. Drcnlh, J. Schoonman, R. J. M. Nolle, J.
Am. Chem. Soc, 1990, 112, 3086.
[8] M. Matsumolo, H. Kobayashi, Y. Hotta, J. Org. Chem, 1984, 49, 4740.
[9] H. Zimmer, D. C. Lankin, S. W. Horgan, Chem, Rev, 1971, 71, 229.
[10] A. P. M. Kentgens, B. A. Markies, J. F. van der Pol, R. I M. Nolle, J. Am.
Chem. Soc. 1990, 112, 8800.
( .J
4 (n=1), 5 (n=2), 6 (n=3)
Schem el, a) KO/Bu, tetraethyleneglycol, b) KOfBu, ethyleneglycol, c) N a2C 0 3,
aza[9 + 3«]erown-(H + 3).
Complexes of Partially Fluorinated Macrocycles
with a Metal-Fluorine cr-Donor Bond and
Their Suitability as Metal Ion Indicators**
Herbert Plenio* and Ralph Diodone
Even thou gh a rather large num ber o f m acrocyclic polyethers
is kn ow n ,11] only few fluorine-containing crow n ethers121 have
been reported, and in m ost o f these all o f the hydrogen atom s
are substituted by fluorine, A s a result o f the electron-w ithdraw ­
ing nature o f the C F2 units, the oxygen or nitrogen atom s in
these polyethers no longer exhibit Lewis basicity and therefore
[*] Dr. H. Plenio, Dipl,-Chem. R. Diodone
Institut für Anorganische und Analytische Chemie der Universität
Albcrtstrasse 21, D-79104 Freiburg (FRG)
Telefax: Ini. code + (761)203-5987
[**] This work was supported by the Fonds der Chemischen Industrie. The authors
thank Prof. Dr. H. Vahrenkamp for his support and Dr. E. Keller for hints in
determining the crystal structure.
Pigili'. Chem. Ini. Ell. Engl. 1994, 33, No. 21
The m acrocyclic ligands 2 - 6 w ere o b ta in e d in yields o f 30 to
8 0 % . In these c o m p o u n d s the c a r b o n -f lu o r in e bon d is directed
tow ards the region th at is exp ected to be th e bin ding site for
m etal ions.
T h e reaction o f c o m p o u n d s 2, 4, 5, an d 6 w ith m etal salts
leads to the co m p lex a tio n o f a m etal io n , w h ile at the sam e tim e
the 1H , 13C, and l9F N M R reson an ces o f th e ligan d s are sh ift­
ed; in contrast, no su ch e ffects w ere o b serv ed for 3 . T h e 19F
N M R reson an ces (300 K ) rep orted for the variou s m eta l c o m ­
p lexes represent the averaged 19F N M R sig n a ls for the m etalfree and m eta l-co n ta in in g ligan d s (fa st e x c h a n g e ). T h e a b so lu te
valu es o f these signal sh ifts are, h o w e v e r , o n ly large in the 19F
N M R spectra, in w h ich v a lu es up to A d = 8.8 have been o b ­
served.
F igu re 1 sh o w s the d ifferen ces in c h e m ic a l sh ift (A5) ob tain ed
by a d d in g an ap p roxim ately te n fo ld m o la r excess o f m eta l salt
to th e flu oroxylen e b is(c r o w n eth ers) 4 - 6 ; how ever, in m o st
cases ad d ition o f m eta l sa lt b e y o n d a tw o fo ld e x cess d oes
n ot m arkedly change the p o s itio n o f the signals. It w as
© VCH Verlagsgesellschafl mbH. D-69451 Wcmheim. 1994
0570-083319412121-2175 S 10.00+ .25/0
2175