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Novel Crown Ethers with a TrithiadiazapentaleneЦTrithiotriuret Redox System.

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Novel Crown Ethers with a Trithiadiazapentalene-Trithiotriuret Redox System**
Heinz Graubaum,* Franz Tittelbach, Gerhard Lutze,
Karsten Gloe,* Melinda Mackrodt, Torsten Kriiger,
Norbert Krauss, Alfred Deege, and
Heike Hinrichs
Red.
Dedicated to Professor Leonard I;: Lindoy
on the occasion of his 60th birthday
ox.
The host-guest chemistry of functionalized macrocycles offers much potential for special applications. For some time now
special attention has been paid to macrocyclic compounds
whose properties can be changed reversibly by both chemical
and physical means.['] This was achieved by introducing functional units like the reversibly isomerizable azo group''] or the
reversible dithiol-disulphide redox systemt3] into the macrocycles. In this way a systematic modification of properties of the
guest such as binding strength and binding selectivity offers new
possibilities for complexation, separation, or detection of both
valuable and toxic species.r41
The assembly of heterocyclic trithiadiazapentalene units and
diamino polyethers to form pentaleno crown compounds provides a new approach to the above-mentioned modification of
macrocyclic host compounds for cations. The exceptional electronic structure of the trithiapentalenes also makes them very
interesting building blocks for further synthesis, both in theory
and in practice.r51
In an earlier publication we showed that 2,5-bis(aryloxy)3,3aA4,4-trithia-1,6-diazapentalene~[~"I
are suitable for reaction
with nucleophiles. The diphenyl derivative 1 reacts with a,w-diaminopolyethers 2 in a 1 :3 molar ratio to form bridged bispentalenes in high yields. These compounds can be used as starting
materials for designing much larger cyclic molecules.'6b1
We now describe the synthesis of pentaleno crown ethers
3a-c and their subsequent reduction to the corresponding
thiourea derivatives 4a-c. Furthermore, their complex-forming
properties deduced from extraction and transport studies will
also be discussed. The synthetic path way leads to a novel class
of crown ethers that contains the trithiadiazapentalenetrithiotriuret redox system that can be used to control the recognition properties.
The compounds 3 were formed in reactions between 1 and 2
in a 1:2 molar ratio. Ring closure only occurred when the chain
of the polyethers was long enough (n 2 1). The structures of the
pentaleno crown ether compounds 3 a -c have been elucidated
[*] Dr. H. Graubaum, Dr. F. Tittelbach, Dr. G. Lutze
[**I
Institut fur Angewandte Chemie Adlershof
Rudower Chaussee 5, D-I2484 Berlin (Germany)
Fax: Int. code +(30)6392-4103
Prof. Dr. K. Gloe, M. Mackrodt, T. Kruger
Institut fur Anorganische Chemie der Technischen Universitat
Mommsenstrasse 13, D-01062 Dresden (Germany)
Fax: Int. code +(351)463-7287
e-mail : karsten.gloe@chemie.tu-dresden.de
Dr. N Krauss
Institut fur Kristallographie der Freie Universitat Berlin (Germany)
A. Deege, H. Hinrichs
Max-Planck-Institut Kohlenforscbung, Mulheim an der Ruhr (Germany)
Financial support by the Akademie der Naturforscher Leopoldina (H. G.)
and by the Fonds der Chemischen Industrie (H. G. and K. G.) is acknowledged. The authors wish to thank Prof. Dr. M. T. Reetz (MPI fur Kohlenforschung Miihlheim) for help rendered during the transport experiments
and Prof. Dr. H. Schneider (MPI fur biophysikalische Chemie Gottingen)
for support with the stability constant measurements. The graduate scholarship from Studienstiftung des deutschen Volkes (to M. M.) is gratefully appreciated.
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3a-c
L
1"
4a-c
by I3C NMR spectroscopy and fast-atom-bombardment mass
spectrometry (FAB-MS), and the results were confirmed by
X-ray analysis171of compound 3b (Figure 1).
W
H
182
Figure 1. X-ray crystal structure of the pentaleno crown compound 3b 171
The macrocycles 3 can be reduced by treatment with zinc in
acetic acid to form the corresponding thioureas 4. The reoxidation is quantitative in the presence of atmospheric oxygen. As
solids compounds 4 are stable in air at room temperature for
several months.
Complex formation of the starting pentalene and of the new
pentaleno crown compounds was investigated by liquid - liquid
extraction studies with solutions of metal salt/picric acid in water and the ligand in chloroform as the liquid-liquid system.[81
The extractability of metal ions (see Figure 2 for Ag' and Hg")
by simple open-chain thiaazapentalene 1 was very low in this
system. However, on introduction of 1 into a macrocyclic ring
system (3a-c) the extractability of Ag' and Hg" increased significantly. The results for Na', K', Cs', Sf', Ca", Zn", Co", and Cu"
were comparable with that obtained in extraction studies with 1
in the same solvent extraction system. A remarkable variation in
the extraction properties of the macrocyclic ring compounds 3a,
3b, and 3c is observed for Ag' and Hg". As shown in Figure 2 3a
extracts Ag' quantitatively into the organic phase (as picrate). In
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Figure 2. Liquid-liquid extraction of Ag' and Hg" with the open-chain trithiadiazapentalene 1 and the pentaleno crown compounds 3a-c, c, = 1 x 1 0 - 4 ~
(AgNO, or HgCI,); cHP,.= 5 x 1 0 - 3 ~ cL
; =1 x ~ O - , M in CHCI,.
contrast, only 20% extraction of Ag' by the ligands 3b and 3c
was ~bserved.~']
The results correlate well with the order of the
potentiometrically determined stability constants of the 1:1 Ag'
complexes with these macrocyclic ring compounds in homoge3a (IgK,,, = 6.84+0.08)>3b (4.51 i
neous
O.O7)=3c (4.50f0.11).
In contrast to the behavior of Ag', the Hg" complex formation was optimal with the medium-sized macrocycle 3b. In this
case more than 80% of HgCl,["] was extracted. With smaller or
larger macrocyclic compounds the extraction decreased significantly (25%, Figure 2).
These differences in behavior can be attributed to the different structures of the Ag' and Hg" complexes formed during
extraction. This has been confirmed by semiempirical molecular
modeling calculations of the 1 :1 complexes.['21 Figure 3 shows
the results of Ag' and Hg" complexes with compounds 3a and
3b. Ag' formed five bonds with two nitrogen atoms of the pentalene unit and three bonds with the ether oxygen atoms of 3a,
which results in an approximately symmetrical arrangement.
Since Ag' forms only four longer bonds with 3b, this complex is
distinctly less favored. In the complex between 3b and HgCl,
interactions between Hg" and the two nitrogen atoms of the
pentalene unit and all three oxygen atoms in the macrocycle
were found. In contrast, Hg" coordinated with only two oxygen
atoms and two nitrogen atoms of 3a.
To determine whether bond formation with Ag' and Hg" depended on the oxidation state of the ligand (3/4), the macrocyclic thiourea derivatives 4 were also tested as extractants. The
extraction properties of all these compounds were comparable.
They extracted Ag' and Hg" quantitatively. This has been attributed to the change of the binding sites during complexation.
Molecular modeling calculations gave some evidence that the
sulfur atoms of the thiourea derivatives acted as coordination
centers and that no coordination within the macrocyclic ring
occurred.
In summary the new ligands uncover an interesting differentiation in the complex formation properties of Ag' and Hg",
which are otherwise very similar. This differentation depends on
Figure 3. Structures of the complexes of Ag' (top) and Hg" (bottom) with 3a (left) and 3b (right), determined by semiempirical calculations (PM3 and ZINDO/l); selected
lengths [A]: for3a Ag'- . N(1) 2.25, Ag'. . N(2) 2.25, Ag'. . . O(1) 2.65, Ag'. . . O(2) 2.62, Ag" - O(3) 2.80; Hg". . .N(1) 2.85, Hg" . . . N(2) 2.65, Hg".. O(1) 4.33, Hg". . . O(2)
2.31, Hg" . . O(3) 2.32; for 3b Ag'. . . N(1) 2.35, Ag" . . N(2) 2.35, Agl- . . O(1) 3.23, Ag'. ..O(2) 3.01, Ag'-. . O(3) 2.82, Ag" . . O(4) 4.62; Hg". . .N(1) 2.72. Hg". . N(2) 2.76,
Hg" . . . O(1) 2.96, Hg"...O(2) 2.62, Hg1"..0(3) 2.74, Hg"...0(4) 2.97.
'
Angen. Chem. Inf Ed. Engl. 1997, 36, No. 15
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'
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the size of the macrocyclic cavity and the component of the
redox system. A significant change of the host selectivity is observed for the redox pairs 4b/3b towards Ag' and for 4a/3a
towards Hg". In both cases the trithiotriuret derivative binds the
metal ion, but the trithiadiazapentalene does not.
Attempts to obtain crystalline complexes of the pentaleno
crown ethers yielded a 1:1 complex with sodium picrate in the
case of 3a and two 1 :1 complexes with ammonium rhodanide
and benzylammonium perchlorate in the case of 3b.['31Preliminary X-ray diffraction studies on the structure of NH4SCN.3b
showed that the ammonium cation is arranged symmetrically in
the ring, fixed by two nitrogen atoms of the pentalene unit and
four ether oxygen atoms.
Success in the synthesis and isolation of NH4SCN.3b have
induced immense interest in the study of the transport properties of the compounds 3a-c towards L-phenylalanine with the
liquid membrane technique. The experimental conditions chosen were similar to those reported by Reetz et al."41 on a system
in which 3,5-bis(trifluoromethyl)benzoylboronic acid provided
the synergistic effect. The results showed that the increase in the
transport rates for L-phenylalanine is dependent on the cavity
size of the macrocycle: 3b (T, =1037)>3a (T, = 417.2)>3c
(T, =74.1).[15] The transport rate of compound 3b, the highest
among 3a-c, is comparable with that of [18]crown-6 (T, =
1270). Liquid-liquid extraction studies with 14C-labeled Lphenylalanine have confirmed the observed trend of the transport rates of compounds 3a-c listed above.
Experimental Section
3a-c: Pentalene l a (2mmol) was stirred for 2-3 days with each of the diaminopolyethers 2a-c (4 mmol) in chloroform (200 mL) at 25 "C. The mixture was
purified by column chromatography (silica gel 60, particle size 63- 100 mm, Merck)
with chloroform/acetone (ZOjl) as eluent for phenol and chloroform/acetone (2/1)
as eluent for 3a-c. 3a: Yield 27%, m.p. 152-154°C; 13CNMR (CDCl,): 6 = 49.1
(NCH,), 56.3 127.4, 128.0, 128.8, 135.5 (benzyl-C), 66.4, 69.2, 70.2 (OCH,), 184.0
(C-2,5), 186.8 (C-3a); FAB-MS: m/z(%o) = 531 (48)[M+H]+, 553 (48) [M+Na]+.
3b: Yield 17.5%, m.p. 1355137°C; 13C NMR (CDCI,): 6 = 39.2-40.2 (NCH,),
51.1 -53.8 (NCH,), 67.0-71.9 (OCH,), 183.4 (C-2,5), 186.0 (C-3a), FAB-MS: m/r
(%) = 423 (48) [M+H]+, 389 (14) [M - SH]+. 3c: Yield 18.8%. m.p. 66-71°C
(acetonitrile); 13CNMR (CDCI,): 6 = 39.7-40.5 (NCH,), 51.7-54.0 (NCH,),
68.0-71.0 (OCH,), 182.2, 182.8 (C-2,5), 185.7, 185.9 (C-3a); FAB-MS: m/z
(%) = 467 (100) [M+H]', 433 (28) [M - SH]'.
4a-c: Macrocycles 3a-c (0.50 mmol) and zinc powder (150 mg) in acetic acid
( 5 mL) were stirred for 30 min at 25 "C under a nitrogen atmosphere. Then additional zinc powder (50 mg) was added, and the mixture stirred for 15 min. The resultant
solution was neutralized with drops of a dilute solution of sodium hydrogencarbonate, extracted with chloroform, washed with water, and evaporated under vacuum.
The mixture was passed through a chromatographic column (silica gel 60, particle
size 63-100 mm, Merck). 4a: Eluent heptane/acetone ljl, yield 85%, amorphous;
13C NMR (CDCI,): 6 = 50.3-51.7 (NCH,), 56.7-58.5, 127.4, 128.0 128.8, 135.5
(benzyl-C), 68.2-70.8 (OCH,), 162.4, 178.2, 180.6 (CS), FAB-MS: m/r (%) = 533
(62) [M + HI+; 4b: eluent heptane/acetone 4/5 to 2/5, yield 44%, m.p. 140-141 "C.
"C NMR (CDCl,): S = 40.1-40.8 (NCH,), 53.2-54.2 (NCH,), 67.4-71.8
(OCH,), 162.2, 179.5, 180.6 (CS), FAB-MS: m / z (%) = 425 (100) [ M t H ] ' ; 4c:
eluent heptane/acetone 4/5 to 3j5, yield 57%, amorphous. I3C NMR (CDCI,):
S = 40.1-40.8(NCH3), 52.2-52.8(NCH2),67.4-69.8(OCH2),
162.4, 178.2,180.6
(CS), FAB-MS: m/z (%) = 469 (54) [ M t HI+.
Compounds: Toward Future Applications(Ed.:S . R. Cooper), VCH, Weinheim,
1992, pp. 27-39.
[ZJ S . Shinkai, T. Ogawa, T. Nakaji, Y. Kusano, 0. Manabe, Tetrahedron Lett.
1979,4569-4572; S. Shinkai, T. Nakaji, Y. Nishida, T. Ogawa, 0. Manabe, J
Am. Chem. Sac. 1980, 102, 5860-5865.
[3] S. Shinkai, K. Inuzuka, 0.Miyazaki, 0. Manabe, J Am. Chem. Soc. 1985,107,
3950-3955; T. Nabeshima, H. Furusawa, Y Yano, Angew. Chein. 1994, 106,
1849-1851; Chem. lnt. Ed. Engl. 1994, 33, 1750-1752; H. Graubaum, F.
Tittelbach, G. Lutze, K. Gloe, M. Mackrodt, J-prakt.Chem. 1997,339,55-58.
[4] J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995, pp. 55-87.
[5] N. Lozac'h, Adv. ffeterocycl.Chem. 1971,13,161-234; C. T. Pederson, Sulfur
Report 1980, 54-77; M. Yokoyama, T. Shiraishi, H. Hatanaka, K. Ogata,
J Chem. Sac. Chem. Commun. 1985, 1704-1705.
[6] a) H. Graubaum, H. Seeboth, P. Zalupsky, Monatsh. Chem. 1989, f20,9971002; b) H. Graubaum, G . Lutze, F. Tittelbach, Chem. Ber. 1994,127,22092213.
[7] Crystallographic data (excluding structure factors) for the structure 3b reported in this paper have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication no. CCDC-100323. Copies of the
data can be obtained free of charge on application to The Director, CCDC,
12 Union Road, Cambridge CB2 lEZ, UK (fax: int. code +(1223)336-033;
e-mail : deposit@chemcrys.cam.ac.uk)
[8] The liquid-liquid extraction studies were carried out at 2 5 k 1 "C with the
radiotracer technique. The phase ratio was 1 : 1 and the shaking time 30 min.
/ c[ %~]=
( ~
DlOO/
) ~
The concentrations are given in Figure 2. D = c ~ ( ~ ~ ~ E) M
( D + 1) where cM= concentration of the metal salt in the organic (org) or
aqueous (w) phase; see K. Gloe, P. Miihl, lsotopenpraxis 1979, 15, 236-239.
[9] From extraction experiments the composition of the extracted complexes can
be determined with the functionality D, =XcL). Ag' also forms [AgL,]+ complexes at higher ligand concentrations.
[lo] The potentiometric titrations were performed with AgCIO, and (Et4N)CI0,
( 5 x 1 0 - ' ~ )in acetone on a 716 DMS Titrino apparatus (Metrohm) with
Ag/Ag+-electrodes. H. J. Buschmann, Inorg. Chim. Acta 1992, 195, 51-60;
B. G. Cox, H. Schneider, Coordination and Transport Properties ofMacrocyclic
Compounds zn Solution, Elsevier, Amsterdam, 1992, pp. 44-47.
[ l l ] Hg" is extracted in the form of the stable species HgCl, under the selected
conditions. The results are therefore independent of the addition of picric acid.
[121 Calculations were performed with the PM3 method (program MOPAC 6.0,
ligands, Hg") and the ZINDO/l method (HyperchemTM4.5, Ag'). T. Kriiger,
K.Gloe, H. Stephan, B. Habermann, K. Hollmann, E. Weber, J. Mot. Model.
1996, 2, 386-389; T. Kriiger, K. Gloe, B. Habermann, M. Miihlstadt, K.
Hollmann, Z. Anorg. Allg. Chem. 1997, 623, 340-346. The calculated and
determined structures of 3b are identical.
[13] Sodium picrate.3a: macrocycle 3a (0.01 mmol) and sodium picrate.H,O
(0.1 1 mmol) were stirred for 1 h in 1 mL CHCI, at 25 "C, before filtration and
addition of 1 mL of toluene; precipitation after 48 h, yield 49%, m.p. 254256°C; C,H,N analysis calcd. for C3,H3ZN,0,0S3Na(7813):C 47.62, H 4.13,
N 12.54; found C 47.74, H 4.03, N 12.56. Benzylammonium perchlorate'3b:
macrocycle 3b (0.02 mmol) and benzylammonium perchlorate (0.04 mmol) in
CHCI, ( 2 mL); precipitation after 24 h, yield 32%, m.p. 160°C (decomp.);
C,H,N analysis calcd. for C,,H36ClN,0BS3 (630.2): C 41.93, H 5.76, N 11.1 1 ;
found C 41.71, H 5.69, N 11.26. Ammonium rhodanide.3b: macrocycle 3b
(0.02 mmol) and NH,SCN (0.04 mmol) were stirred for 1 h in CHCI, (2 mL)
at 25°C before filtration and addition of 2 mL of toluene; crystals after 24 h,
yield 60%, m.p. 160°C (decomp.); C,H,N analysis calcd. for C,,H30N,0,S,
(498.8): C 38.53, H 6.07, N 16.84, found C 38.35, H 6.13, N 16.93.
[14] M. T. Reetz, J. Huff, J. Rudolph, K. Tollner, A. Deege, R. Goddard, J: Am.
Chem. Sac. 1994, 116, 11588-11589.
[15] The transport studies with L-phenylalanine were carried out in an apparatus as
described by Izatt: J. D. Lamb, J. J. Christensen, S. R. Izatt, K. Bedke, M. S.
Astin, R. M. Izatt, J. Am. Chem. Sac. 1980, 102, 3399-3403; results (data in
mmolL-'h-'):3a 1210,3b3007,3c215, [18]crown-63680,"41 blankvalue2.9;
the relative transport rate as mentioned in the text takes into account the
transport without ligand.
Received: January 23, 1997 [Z 10025IE1
German version: Angew. Chem. 1997, 109, 1719-1722
Keywords: crown compounds host-guest chemistry mercury
* silver
[l] J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995, pp. 124- 138;
K. Schaumburg, J.-M. Lehn, V. Goulle, S. Roth, H. Byrne, S. Hagen, J.
Poplawski, K. Brunfeldt, K. Bechgaard, T. Bjornholm, P. Frederiksen, M.
Jorgensen, K. Lerstrup, P. Sommer-Larsen, 0. Goscinski, J.-L. Calais, L.
Eriksson in Nanostructures Based on Molecular Materials (Eds. : W. Gopel, C.
Ziegler), VCH, Weinheim, 1992, pp. 153-173; S. L. Gilat, S . H. Kawai, L M .
Lehn, Chem. Eur. J. 1995, 1, 275-284; S. H. Kawai, S. L. Gilat, R. Ponsinet,
J.-M. Lehn, Chem. Eur. J. 1995,1,285-293; Z. Chen, L. Echegoyen in Crown
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