azobenzene-based photoswitchable catenanes

M. Bauer, W. M. Muller, U. Muller, K. Rissanen, F. Vogtle 649

Azobenzene-Based Photoswitchable Catenanes Martin Bauerb, Walter Manfred Miiller”, Ute Miiller”, Kari Rissanenb, and Fritz Vogtle*”

Institut fur Organische Chemie und Biochemie der Universitat Bonna, Gerhard-Domagk-Strale 1, D-53121 Bonn, Germany

Department of Chemistry, University of Joensuub, Yliopistokatu 7, FIN-80101 Joensuu, Finland

Received October 18, 1994

Key Words: Catenanes I Interlocked rings I Mechanical bond I Photoswitches ~

Four catenanes (1-4) and the corresponding tetracationic monocycles 5-8 are synthesized. X-ray structural analyses allow a prediction of the mobility (circumrotation) of the “interlocked” rings in the catenanes, which is proven by ‘H- N M R spectroscopy. An unexpected order in the crystal pack-

ing of 6 is demonstrated. ( E / Z ) isomerization in one ring in- fluences the second ring of 1-4 and inversely. An existing obstacle inside the cavity of the switchable macrocycle can block this isomerization completely.

Azobenzene-Based Photoswitchable Catenanes

In contrast to the first syntheses of catenanes, the yields of which were rather modest due to their ring formation controlled only by statistics[’], the strategies using supramolecular template developed during the last six years allow their synthesis on a preparative Start- ing from Stoddart’s methodology to achieve preorganis- ation of the reactants by donorlacceptor interaction~[~,~], we developed the catenanes 1-3 where, in contrast to 4[s,91, the nearly inert aromatic spacer units are systematically ex- changed for azobenzene units. In order to better understand the interaction between the noncovalent bonded but mechanically interlocked macromonocyclic rings, the corresponding “empty” macrocycles 5-8 were also synthesized for comparison.

The goal of this work was to produce for the first time photoswitchable catenanes by incorporation of one or two azobenzene units as photoresponsible elements into the tetracationic ring. Azobenzene has been an established photoswitchable component for many years in the con- struction set of supramolecular chemistry[l01. It isomerises on UV irradiation with a wavelength of approximately 300 nm from the more favoured E to Z configuration. Ir- radiation with 440 nm leads inversely to isomerisation from the (z) to the ( E ) isomer. In this way, it is possible to switch quickly between two photostationary equilibria, whereas thermal reisomerisation without light allows quantitative reformation of the ( E ) isomer within a half- life of about 25 days at room temperature[”]. In addition, the configurational change of the N = N bond is amplified by the phenylene rings. Thus, for instance, the distance between both carbon atoms in para-position !hortens due to (EIZ) isomerisation from about 9.0 to 6.2 A, and the phenyl groups are not located in the same plane any more[l21. Consequently, the distance between both bipyridine blocks in the paraquat macrocycle of the catenanes 1-3 should

be controllable from outside without any chemical inter- vention.

Syntheses

The catenanes 1-4 and also the macrocycles 5-8 are obtained in accordance with the following scheme starting with the non-macrocyclic dicationic compounds 10- 12 by reaction with the corresponding bis(bromomethy1)arenes. Because of the donor-acceptor template effect, cyclisation could be achieved without the usual conditions like high dilution and synchronous addition of the components over a long period. Typical concentrations are 1 mmol per 100 ml of solvent for the synthesis of macromonocycles and the double for catenane synthesis, as far as solubility allows so.

Crown ether 9L7,l31, obtained together with a small amount of tetrabenzeno crown 16 by a simplified procedure from dibromo compound 15, was used in 100% excess. However, 9 can be recycled almost completely. In principle, the empty paraquat rings can also be isolated in lower yields as side products of the catenane synthesisE81. The yields of the azobenzene unit-containing macromonocycles, obtained according to the procedure described here, are 40 to 50%, and for the catenanes 14% for the smallest one (4) and 49% for 3. Surprisingly, no catenane containing a para- substituted azobenzene unit could be recovered. Neither the reaction of 10 or 12 with 4,4’-bis(bromomethy1)azobenzene nor the reversed path via 13 has been successful under stan- dard conditions (without high Obviously, the fixed almost linear geometry of the inflexible para-substituted (E)-azobenzene unit in the starting material is respon- sible for this. Only oligomerisation occurs instead of ring closure.

X-Ray Structural Analyses

The X-ray structures of catenanes 1 and 4 as well as of the paraquat ring 6 (Figure 1) admittedly give only a rough

Liebigs Ann. 1995,649-656 0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim, 1995 0947-3440/95/0404-069 $10.00+.25/0

650 M. Bauer, W. M. Muller, U. Muller, K. Rissanen, F. Vogtle

0 \

8 ‘L

1

w 7

4”-”9

insight into the “frozen” geometries, but nevertheless together with the ‘H-NMR spectra they allow statements regarding the dynamics of the intertwined rings.

X-Ray Structure of 4

In 4, the smallest of our catenanes with two differently substituted xylene spac:rs, the average distance between the bipyridine units is 6.9 A. In comparison with the unsubsti- tuted bipyridine, the pyridine rings of the inner bipyridine

3 W

unit with a torsion angle of 1” are located almost in the same plane despite the mutual repulsion of the ortho hydrogen atoms. This points to a strongly reduced mobility of the crown ether ring pressed inside. The ‘H-NMR spectrum showing two very different signals for both hydroquinone moieties confirms this hypothesis. Thus, in [D,]acetone the protons of the outer hydroquinone unit appear as a sharp singlet at 6 = 6.27, the resonance of the inner ones is split into two broad signals at 6 = 4.42 and another in the area of the oxyethylene groups at about 6 = 3.66. Further details, particularly the temperature dependence of the ‘H- NMR spectrum, have already been discussed thoroughly by StoddartLg1.

The crystal shows a fairly dense packing of the catenane molecules, which probably can be attributed to the intermolecular donor/acceptor interaction between the outer hydroquinone moiety and the outer bipyridine unit of the next molecule. In the side view (Figure 2), however, channels built by four molecules are visible, running through the crystal lattice. In this two-dimensional network the hexafluorophosphate anions are located as well as a part of the strongly disordered solvent molecules (acetonitrile).

Liebigs Ann. 1995, 649-656

Azobenzene-Based Photoswitchable Catenanes 65 1

-

anion

exchange

7

10 - 12

+ 9

2) anion exchange

5 - 8 1 - 4

X-Ray Structure of 1 Due to the larger azobenzene spacer in 1 t$e average dis-

tance between both bipyridine units is 7.9 A, measured at the central bipyridine single bond. The non-bonded contact distances between the bipyridine and hydroquinone moieties are short compare! to their van der Waals radii, they vary from 3.4 to 3.6 A, the shortest distance between the outer hydroquinone and the inner bipyridine unit being 3.39(3) A. From the inner hydroquinone moiety to the inner bipyridine unit it is 3.41(3) A and finally 3.56(3) A to the outer bipyridine unit. In the crystalline state, the more spacious interior enables the inner bipyridine unit to adopt a more twisted conformation with a torsion angle of 12.1(2)". In comparison with this, the outer bipyridine units, which are not pressed in, still retain a torsion angle of 30.8(2)". The inner hydroquinone ring is not centred in the paraquat ring. This suggests that only one bipyridine2+ is involved in the charge-transfer complex.

In solution the spacious interior allows a fast circumrotation of the crown. As expected the 'H-NMR spectra show only an average signal at 6 = 5.72 corresponding to all 8 hydroquinone protons. In [D,]acetonitrile and also in the I3C-NMR spectrum only one sharp signal appears: the exchange between internal and external position is already too fast relative to the NMR time scale. Similar obser- vations have been made with catenane 3. The corresponding slightly broadened signal is found at 6 = 5.85 (in acetone).

In contrast to 4, catenane 1 in the crystal (Figure 3) is oriented in such a way that the outer bipyridine unit faces the same unit of a second molecule. Its outer hydroquinone moiety faces that of the third molecule. No intermolecular interactions therefore take place. The more different spacers cause a suggested link of opposed columns of molecules with the same orientation lying on top of the other forming

10 11

12 13

0 4 o b o

14 0

BYY 15

16

layers and thus preventing channel formation. The anions and solvent molecules fill the gap between two of these layers.

X-Ray Structure of 6 Regarding their dimensions 6 and the tetracationic cycle

of catenane 2 should not be considerably different. The distance between both bipyridine units is already 9 A. This should be suEcient for an unimpeded circumrotation of the polyether ring in 2. Indeed, the signal for all hydroquinone protons appears as a sharp singlet at 6 = 5.95. In the X-ray structural analysis, the syn-position of the azobenzene units is conspicuous as well as the apparent planarity of the bipyridine units. The latter is caused by disorder of the stag- gered pyridine rings. The molecule looks like a rectangular box without bottom, with walls formed by two nearly parallel bipyridine units, and two divergent azobenzen? units. The diomensions of the openings are about 9 X 10 A and 9 X 15 A respectively.

Liebigs Ann. 1995, 649-656

652 M. Bauer, W. M. Muller, U. Muller, K. Rissanen, F. Vogtle

Figure 1. Crystal structure of 1, 4, and 6

1

4

6

Figure 3. Catenane 1 in the crystal lattice: top view with “link” (left) and side view with layers containing the not shown anions

and solvent molecules

are stuck into each other like a stack of glasses and form, because of the missing bottoms, infinite angular tubes. These reversely ordered parallel tubes incorporate part of the disordered voluminous hexafluorophosphate anions, the remaining portion connects the charged tubes between two neighbouring bipyridine rows,

Figure 4. Monocycle 6 in the crystal lattice: side view showing the “pile” (left) and top view into the tube interior

Figure 2. Catenane 4 in the crystal lattice: front view (left) and side view with channels (right). The anions and solvent molecules are

not shown

The extensive structure possesses an unusual geometry: In the crystal lattice (Figure 4), the conically tapering boxes

Photoisomerisations

On irradiation of catenane 1 with UV light at 300 nm, a photostationary equilibrium is achieved containing about 40% of the 2 isomer. The appearance of NMR signals (Fig- ure 5), which are typical of (2)-azobenzene and in comparison with 5 under the same conditions, prove that the irradiation causes only the expected (EIZ) isomerisation and not a light-induced electron transfer in the CT complex. This configurational change has a severe effect on the entire molecule: All signals appear twice, even those of the para phenylene ring that is separated by the bipyridyl groups. Whereas the proton signals of the hydroquinone part of the crown are almost unchanged, the (not further correlated) signals of the oxyethylene groups multiply with chemical

Liebigs Ann. 1995, 649-656

Azobenzene-Based Photoswitchable Catenanes 653

shifts up to 0.07 ppm. Because the isomerisation reduces the distance between the bipyridine units, the space available for the rotation of the polyether cycle decreases. Ap- parently, this mechanical constriction affects more the “thicker” aliphatic parts of the crown than the flat arene units in the ring. This should lead to a increased “friction” and thus acting as a brake on rotation. A corresponding further broadening of other signals, however, could not be detected.

Figure 5. ‘H-NMR spectrum of 1 (250 MHz, [D6]acetone) before (below) and after irradiation with 300 nm (above)

Figure 6. Part of the ‘H-NMR spectrum of 2 (250 MHz, [D3]acetonitrile) before (below) and after irradiation with 300 nm (above)

r- I I I I ---r 6.0 5.5 5.0 4.5 4.0 3.5

[ P P m l

I I I I I I 9 8 7 6 5 [PPml 4

Something similar can be observed after photoisorneri- sation of catenane 2. Due to two switchable azo groups, both (E,Z)-2 and (Z,Z)-2 are formed. However, the situ- ation simplifies as a result of the faster reisomerisation of (Z,Z)-2 compared to the (E,Z) isomer. So after some time the (Z,Z) isomer, which is already formed in a maximum concentration of lo%, is negligible in the ‘H-NMR spectrum (Figure 6). Because also shifts of the (E,Z) isomer for the oxyethylene protons of about 0.05 ppm occur, on the other hand the crown ether should be able to rotate freely according to modelling studies, and also the hydroquinone units still appear as a sharp singlet, shifted about 0.04 ppm to high field, a slowdown of the translation process can be excluded. Rather the dissymmetry of the paraquat ring and thus the different inclination of the axis of rotation of the polyether are offered as the rationale.

In the presence of ( 2 , 2 7 2 the spectrum looks somewhat different like immediately after irradiation. Although in every tested solvent some signal overlapping exists, particularly in acetone, a broadening in the area of the aromatic crown ether protons can be observed the reason of which should be limited circumrotation.

Proof that the crown is really considerably pressed is the behavior of catenane 3. Because of the diminished distance between its bipyridine units it was expected to show the strongest retardation of the translation process of the crown ether. Surprisingly, 3 is not isomerisable any more. Even immediately after irradiation for several hours only the unchanged spectrum of the pure (E) isomer was observed. In contrast to monocycle 7, which is isomerisable as expected,

the permanent filling of the interior blocks any further ap- proach of the rigid paraquat bridges and thus prevents the configurational change from (E) to (Z) inducing a higher “pressure”. This observation demonstrates that the (E,Z) isomerisation not only affects the movement of the crown but also that the presence of a permanent “guest” exerts a drastic influence on the (E,Z) isomerisation process.

Acceleration of the thermal (2,E) reisomerisation due to the paraquat interior filled by the crown is discussed in reE[*].

Conclusion

Catenanes are by no means exotic, hardly available compounds of doubtful use. They are one of many compound classes used in supramolecular chemistry and are easy to fit with functionalities as illustrated by photoswitchable build- ing We have shown in this paper that only one reversible configurational change via the mechanical bond affects measurably every part of the molecule. On the other hand just this configurational change can be prevented mechanically. Knowledge obtained by investigation of catenanes should be in part transferable to potential host- guest complexes, even though their complex constants are not infinitely large.

This work was supported by the Ministerium fur Forschung und Technologie (project no. 0329120 A). M. B. thanks the Centre for Znternntiond Mobility, Helsinki, for a post doctoral grant.

Experimental ‘H and I3C NMR: Bruker WM 250 (250 and 62.9 MHz, respec-

tively). - MS: MS-30 and MS-50 A.E.I.; FAB-MS: Concept 1 H, Cratos, Manchester, GB, with 3-nitrobenzyl alcohol (mNBA) as

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654 M. Bauer, W. M. Muller, U. Miiller, K. Rissanen, F. Vogtle

matrix. - Melting points: Tottoli melting-point apparatus SMP-20 (Buchi), uncorr. - Thin layer chromatography: TLC aluminium sheets, silica gel 60 F254 (Merck 5554), eluent: dichloromethane/ tert-butyl methyl ether (1:l); HPTLC sheets, silica gel 60 F254 for nano TLC (Merck 5628), eluent methanol/l M aqueous ammonium chloride solutiodnitromethane (7:2: 1). - Column chromatography: Preparative medium-pressure system (MPLC), Biichi, silica gel LiChroprep Si 60, 15-25 pm (Merck 9336), eluent A: methanolll M aqueous ammonium chloride solution (7:2), eluent B: methanol/ 1 M aqueous ammonium chloride solutiodnitromethane (14:4: I), eluent C: methanolll M aqueous ammonium chloride solution/ nitromethane (7:2: 1). - Elementary analyses: Mikroanalytische Abteilung des Instituts fur Organische Chemie und Biochemie der Universitat Bonn and Mikroanalytisches Labor Pascher, Remagen. Some compounds were analysed as their chlorides. - Preparation of the hexafluorophosphates by anion exchange: A clear solution of the corresponding chloride in water was treated with a large excess of a 50% ammonium hexafluorophosphate solution. The precipitate was filtered and washed with water. - Preparation of the chlorides by anion exchange: To a clear solution of the corresponding mixed salt (bromide and hexafluorophosphate) in nitromethane a 20% solution of tetraethylammonium chloride in nitromethane was added. The precipitate was filtered and washed.

I, I l-Bis[4- (benzyloxy)phenyl]-3.6,9-trio~aundecane[~~: Under argon 16.0 g (80 mmol) of 4-(benzy1oxy)phenol was added to a boiling solution of 4.94 g (88 mmol) of powdered potassium hydroxide in 200 ml of ethanol. To the colorless solution a solution of 12.8 g (40 mmol) of l,ll-dibromo-3,6,9-trioxadecane (15) in 75 ml of ethanol was dropped, and heating was continued for 5 h. The mixture was concentrated, the residue taken up in 150 ml of dichloromethane, and the solution was washed several times with water, a 5% sodium hydroxide solution and water. After drying with sodium sulfate and evaporation of the solvent the product was recrystallized from ethanol. Yield: 17.9 g (SO%), m.p. 81-83°C ref.L7] 78-80°C), TLC: Rf = 0.62.

1,4,7,I0,17,20,23,26,28,32-Decuoxu[13.13]paracyclophane (9)L7.I3]: A solution of 14 g (25 mmol) of the above compound in 150 ml of ethyl acetate and 50 nil ethanol was shaken together with 1.4 g of palladium on charcoal (10%) for 8 h at 40°C in a Parr hydrogen- ation apparatus (3 bar). After filtration with kieselgur (Merck 8117) and evaporation of the solvents the crude product was used for cyclisation: Within 1.5 h a solution of 7.44 g (23.2 mmol) of 1,l l-dibromo-3,6,9-trioxadecane (15) in 100 ml of dimethylforma- mide was dropped to a stirred mixture of 15.2 g (46.5 mmol) of caesium carbonate and 8.80 g (23.3 mmol) of the crude phenol at 80°C. Stirring was continued for 2 d. After cooling to room temp. the precipitate was filtered and the solution evaporated to dryness. On addition of a small amount of water the remaining product solidified. After separation by MPLC on silica gel 15-40 pm (Merck 151 11) with dichloromethaneltert-butyl methyl ether (1 : 1) and recrystallisation from methanoYethano1 2.25 g (18%) of 9 was obtained as colorless needles. M.p. 93-95°C (ref. 93-94°C['3a1, 87-88"C['], TLC: Rf = 0.26. - FAB-MS, mlz (%): 536 (100) [M+].

Dimevic Crown Ether 16: The second fraction of the workup of the previously described reaction contained 180 mg (0.23%) of the dimeric crown ether. M.p. 96-99°C (ref.['3b] 96-98"C), TLC: Rf =

0.12. - FAB-MS, (mlz) ("XI): 1072.5 (100) [M+] and 1095 [M + Na+].

Bis- (kexafluorophosphate) (13): To a boiling solution of 3.12 g (20 mmol) of 4,4'-bipyridine in 70 ml of dry acetonitrile 1.84 g (5.0 mmol) of 4,4'-bis(bromomethyl)azobenzene[~5] was added, and the

I, 1 '-[4,4' -Azobenzenebis(methylene) ]bis(4,4' -bipyridinium)

mixture was stirred under reflux for 12 h. After filtration the precipitate was collected, washed with acetonitrile and converted to the chloride. This was dissolved in 40 ml of acetonitrile and purified by MPLC with eluent A. Conversion to the hexafluorophosphate yielded 2.95 g (73y0) of 13. HPTLC: Rf = 0.40. - 'H NMR (250 MHz, [D6]acetone): 6 = 6.26 (s, 4H, CHJ, 7.90 and 8.04 (both d, J = 8.5 Hz, 4H), 8.73 and 9.44 (both d, J = 6.9 Hz, 4H). - I3C NMR (62.9 MHz, [D3]acetonitrile): 6 = 64.51, 122.82, 124.57, 127.31, 131.30, 137.05, 142.05, 146.07, 152.15, 153.97, 155.72. -

calcd. C 59.91, H 5.62, N 12.33; found C 60.55, H 5.51, N 12.59.

Bis- (hexafluorophosphate) (ll)C8]: A solution of 14.06 g (90 mmol) of 4,4'-bipyridine in 50 ml of dry acetonitrile was heated with a solution of 5.52 g (15 mmol) of 3,3'-bis(bromomethyl)azobenzene[16~ in 175 ml of dry acetonitrile under reflux for 14 h. The precipitate was collected by filtration, washed with acetonitrile, converted to the chloride and purified by MPLC with eluent A. The pure fraction was converted to the hexafluorophosphate to give 7.58 g (62%) of 11. - HPTLC: Rf = 0.39. - 'H NMR (250 MHz, [D6]acetone): 6 = 6.30 (s, 4H, CH2), 7.76 (t, J = 7.7 Hz, 2H), 7.90 (dm, J = 8 Hz, 2H), 7.93 (dm, J = 7.5 Hz, 2H), 8.26 (m, 2H), 8.76 and 9.48 (both d, J = 6.9 Hz, 4H). - I3C NMR (62.9 MHz, [D3]acetonitrile): 6 = 64.67, 123.64, 124.71, 124.78, 127.50, 131.73, 133.15,

FAB-MS, m/z: 665.2 [M+ - PFs]. - C34H28c12N6 ' 5 H2O (681.6):

I , I -[3> 3'-Azobenzenebis (methy lene) Ibis (4, 4'-bipyridinium)

135.22, 146.14, 150.70, 153.86. - FAB-MS, m/z: 665.3 [M+ - PFs]. - C34H28C12N6 1 HzO (609.6): calcd. C 67.00, H 4.96, N 13.79; found C 66.74, H 4.80, N 13.93.

General Procedure for the Preparation of Macromonocycles 5-8: A solution of an equivalent amount of the bis(bromomethy1) compound in acetonitrile was added to a solution of the corresponding dicationic bipyridinium compound, and the mixture was heated under reflux for 2 d. Then the solvent was evaporated, the residue dissolved and purified by MPLC with eluent C. After evaporation of the solvent the product was converted to the tetrakis- (hexafluorophosphate).

Macromonocycle 6L8l: From 368 mg (1.0 mmol) of 3,3'-bis(bromomethyl)azobenzene[l6I, dissolved in 75 ml of acetonitrile, and 811 mg (1.0 mmol) of 11 in 75 ml of acetonitrile. Yield: 620 mg (47%). - HPTLC: Rf = 0.16. - IH NMR (250 MHz, [D3]acetonitrile): 6 = 5.88 (s, SH), 7.73 (t, J = 7.7 Hz, 4H), 7.85 (dm, J = 7.7 Hz, 4H), 7.93 (m, 4H), 7.99 (dm, J = 8.0 Hz, 4H), 8.24 and 8.93 (both d, J = 6.9 Hz, 8H). - I3C NMR (62.9 MHz, [D3]acetonitrile): 6 = 65.27, 124.33, 125.66, 128.43, 131.78, 134.38, 134.63, 146.30, 151.36, 154.13. - FAB-MS, m/z: 1163.2 [M+ - PF,]. - C48H40F24N8P4 (1308.75): calcd. N 8.56; found N 8.63.

Macromonocycle 7: From 2.12 g (3.0 mmol) of 1,1'-[1,3-phenyl- enebis(methylene)]bi~-4,4'-bipyridinium bis(hexafluorophosphate) (l2)[I7] and 1.10 g (3.0 mmol) of 3,3'-bis(bromomethyl)azobenzene in 300 ml of acetonitrile. Yield: 1.57 g (43%). - HPTLC: Rf = 0.12. - 'H NMR (250 MHz, [D,]acetonitrile): 6 = 5.79 and 5.90 (both s, 4H, CHz), 7.55 (m, 1 H), 7.62 (m, 2H), 7.65-7.78 (m, 3H), 7.79-7.86 (m, 4H), 7.98 (dm, J = 8.1 Hz, 2H), 8.21 (d, J = 6.9 Hz, 4H), 8.26 (d, J = 7.0 Hz, 4H), 8.81 (d, J = 7.0 Hz, 4H), 8.90 (d, J = 6.9 Hz, 4H). - 13C NMR (62.9 MHz, [D3]acetonitrile): F = 65.21, 122.98, 125.05, 128.28, 128.36, 128.50, 131.47, 131.54, 132.02, 133.38, 134.09, 134.79, 135.04, 146.16, 146.70, 151.02, 151.29, 154.18. - FAB-MS, m/z: 1059.2 [M+ - PF6], 914.2 [M+ - 2 PF6], 769.2 [M+ - 3 PFs]. - C42H36C14N6 ' 6 H2O (874.7): calcd. C 57.67, H 5.53, N 9.61; found C 57.23, H 5.51, N 9.76.

Macromonocycle 5: From 81 1 mg (1 .O mmol) of 11 and 264 mg (1.0 mmol) of 1,4-bis(bromomethyl)benzene in 145 ml of acetonitrile. Yield: 449 mg (37%). - HPTLC: Rf = 0.11, - 'H NMR (250

Liebigs Ann. 1995, 649-656

Azobenzene-Based Photoswitchable Catenanes 655

MHz, [D6]acetone): 6 = 6.16 (s, 4K, CH,), 6.28 (s, 4H, CH2), 7.77 (t, J = 7.8 Hz, 2H), 7.82 (s, 4H), 7.88 ("t", J = 1.6 Hz, 2H), 7.96 (dm, J = 7.8 Hz, 2H), 8.04 (dm, J = 7.5 Hz, 2H), 8.61, 8.69, 9.40 and 9.44 (all d, J = 6.9 Hz, 4H). - 13C NMR (62.9 MHz, [D3]acetonitrile): 6 = 65.29, 65.48, 123.98, 124.99, 128.33, 128.42, 131.58, 131.64, 134.24, 134.97, 136.37, 146.19, 146.44, 150.83, 150.96, 154.37. - FAB-MS, m/z: 1059.1 [M+ - PF,], 914.2 [M+ - 2 PF,], 769.2 [M+ - 3 PF,]. - C ~ & I & Z ~ N ~ P ~ (1204.6): calcd. N 6.98; found N 6.96.

Macromonocycle 8['s91: From 2.12 g (3.0 mmol) of l,lf-[1,3-phen- ylenebis(methylene)]bi~-4,4'-bipyridinium bis(hexafluorophosphate) (12)[171 and 0.79 g (3.0 mmol) of 1,4-bis(bromomethyl)benzene in 500 ml of acetonitrile. Yield: 823 mg (250/4). - HPTLC: Rf = 0.09. - 'H NMR (250 MHz, [D,]DMSO): 6 = 5.85 and 5.88 (both s, 4H), 7.56 (t, J = 7.7 Hz, lH), 7.73 (s, 4H), 7.84 (d, J = 7.7 Hz, 2H), 8.07 (m, IH), 8.41, 8.48, 9.43 and 9.47 (each d, J = 6.7 Hz, 4H). - FAB-MS, mlz: 955.1 [M+ - PF,], 810.2 [M+ - 2 PFs], 665.2 [M+ - 3 PF,]. - C36H32F24N6P4 (1100.5): calcd. N 5.09; found N 4.98.

General Procedure for the Preparation of the Catenanes 1-4: To a solution of the dicationic bipyridine and the double molar amount of crown ether 9 in 20 ml of acetonitrile was added a solution of an equimolar amount of the corresponding bis(bromomethyl) compound in acetonitrile, and the mixture was stirred at room temp. for 8 d. After filtration the filtrate was stored at - 18°C over- night and after a second filtration almost the entire excess of the crown ether could be recovered. Then the solvent was evaporated, the residue dissolved and purified by MPLC with eluent C. After evaporation of the eluent the product was converted to the tetrakis- (hexafluorophosphate).

Catenane 2: From 0.37 g (1.0 mmol) of 3,3'-bis(bromomethy1)- azobenzene, 1.07 g (2 mmol) of 9 in 80 ml of acetonitrile and 0.81 g (1.0 mmol) of 11. Yield: 287 mg (16%). - HPTLC: Rf = 0.27. - 'H NMR (250 MHz, [D6]acetone): 6 = 3.50-3.56 (m, 8H, CH2CH20), 3.67-3.73 (m, 8H, CHzCH20), 3.84 ("s", 16H, CH2CH20), 5.95 and 6.25 (both s, 8H), 7.79 (t, J = 7.8 Hz, 4H), 8.04 (m, 8H), 8.24 (m, m 4H), 8.40 and 9.38 (both d, J = 6.6 Hz, 8H). - FAB-MS, m/z: 1699.5 [M+ - PF6], 1554.5 [M+ - 2 PF6], 1409.6 [M+ - 3 PF,]. - Cj&&24N@10P4 (1845.4): calcd. N 6.07; found N 6.13.

Catenane 3: From 184 mg (0.5 mmol) of 3,3'-bis(bromomethy1)- azobenzene, 537 mg (1 mmol) of 9 in 50 rnl of acetonitrile and 353 mg (0.5 mmol) of 12. Yield: 454 mg (49%). - HPTLC: Rf = 0.18. - 'H NMR (250 MHz, [D6]acetone): 6 = 3.67-3.85 (m, 32H, CH2CH20), 5.85 (br. 8H, hydroquinone), 6.19 and 6.21 (s, 4H, CH,N), 7.80 (t, J = 7.7 Hz, 2H), 7.89-7.98 (m, 6H), 8.08-8.16 (m, 4H), 8.24 (d, J = 6.7 Hz, 4H), 8.28 (d, J = 6.5 Hz, 4H), 9.11 (d, J = 6.4 Hz, 4H), 9.23 (d, J = 6.7 Hz, 4H). - FAB-MS, m/z:

- C~OH~~F&&P~ (1741.3): calcd. N 4.83; found N 5.35. Catenane 1: From 257 mg (0.70 mmol) of 3,3'-bis(bromomethyl)-

azobenzene, 975 mg (1.84 mmol) of 9 and 493 mg (0.70 mmol) of 10 in 50 ml of acetonitrile. For MPLC eluent B was used. Yield: 414 mg (34%). - HPTLC: Rf = 0.19. - 'H NMR (250 MHz, [D,]acetone): 6 = 3.60-3.68 (m, 8H, CH2CH20), 3.74-3.88 m, 24H, CH2CH20), 5.72 (br., 8H, hydroquinone), 6.15 and 6.21 (both s, 4H, CH,N), 7.82 (t. J = 7.2 Hz, 2H), 7.95-8.02 (m, 4H), 8.04 (s, 4H), 8.11 (dm, J = 8.0 Hz, 2H), 8.22 (m, 8H), 9.21 and 9.37 (both d, J = 6.7 Hz). - I3C NMR (62.9 MHz, [D6Jacetone): 6 = 65.41, 66.19, 68.97, 71.35, 71.65, 71.90, 116.02, 123.34, 126.52, 127.36, 127.80, 132.13, 132.34, 135.03, 136.18, 137.85, 146.83, 147.35, 149.05, 149.30, 153.36, 154.82. - FAB-MS, mlz: 1595.4

1595.3 [M+ - PF,], 1450.3 [M' - 2 PF,], 1305.4 [M+ - 3 PF,].

Table 1. Crystal and data collection parameters of 1, 4, and 6

1 [a1 4 fbl 6 [GI

Formula

Molecular mass Crystal size Imml Crystal system SP- group a [Pml b bml

No. of reflections: measured independent observed [I >2a(I)] Weighting scheme Parameters Max. W e m

~~

q&76N6010h

1864.42 0.30 ' 0.40.0.45 triclinic P-1 (No. 2) 1183.7( 1) 1472.6(4) 2564.1(4) 105.20(2) 100.2q1) 93.00(1) 4221(1) 1.473 2 0.20 1920

O 5 h 5 l Z -15 5 k5 15 -27 5 1 5 27

4 PFd. 3 C H 3 c N

40 C Z ~ c 440

c64H72N40106 4 PF6-. 5 C H 3 c N 1890.46 0.30.0.40.0.45 monocliic c u c (No. 15) 4980.8(8) 1401.5(2) 2904.4(3) 90 119.730) 90 17604(1) 1.426 8 0.19 7792

-545h547 05k5 15 051531

30 c 28 < 460

10949 12984 10332 12216 5055 5472

lOn 1015 c 0.10 c 0.10

w=w'[ 1 .O-(AF/&FFl2

Rnu R Rw Max. Ap [lo6 e pm3]

0.032 0.008 0.108 0.1 14 0.135 0.132 5 0.9 5 0.8

c48H40N8*

1308.75 0.20.0.35 .0.45 triclinic P-1 (No. 2) 1363.5(2) 3240.3( 10) 659.1(2) 90.25(2) 100.91(2) 79.00(2) 2805(1) 1.5M 2 0.25 1320

-145h514 -335k533 0 5 1 5 6

7180 6830 2476

505 c 0.15 0.013 0.127 0.123 5 0.85

4 PF.5-

40< 28 < 440

La] One acetonitrile molecule is disordered over two orientations. - lb] With one unresolved electron density, treated as 8 C atoms with occupancy 0.5. - 1'1 The anions are disordered over two sites and two orientations.

[M+ - PF6], 1450.3 [M+ - 2 PF6], 1305.5 [M+ - 3 PF,]. -

C70H76F~N6010P4 (1741.3): calcd. N 4.83; found N 5.29.

Catenane 418,']: From 0.49 g (1.85 mmol) of 1,3-bis(bromomethyl)benzene, 2.22 g (4.13 mmol) of 9 and 1.31 g (1.85 mmol) of 10 in 100 ml acetonitrile. For MPLC eluent A was used. Yield: 426 mg (14%). - HPTLC: Rf= 0.16. - 'H NMR (62.9 MHz, [Ddacetone): 6 = 3.37-3.44 and 3.60-4.08 (m, altogether 34H), 4.43 (br., 2H), 6.05, 6.13, 6.27 (each s, 4H), 7.89 (t, J = 7.6 Hz, lH),8.00(m, lH),8.05(~,4H),8.19(rn,2H),8.20,8.27and9.17 (each d, J = 6.5 Hz, 4H), 9.29 (d, J = 6.7 Hz, 4H). For a detailed correlation cf. - I3C NMR (62.9 MHz, [D6]acetone): S = 65.81, 66.32, 67.84, 69.09, 71.13, 71.26, 71.34, 71.78, 72.01, 115.0, 116.60, 126.79, 127.13, 132.70, 135.51, 135.75, 138.46, 146.23, 147.04, 147.54, 151.97, 153.70. - FAB-MS, mlz: 1491.5 [M+ -

C64H72CbN4010 . 4 HzO (1271.2): calcd. C 60.47, H 6.34, N 4.41; found C 60.01, H 6.71, N 4.32.

Crystal Structure Determination: Diffractometer CAD4 (Enraf- Nonius), Mo-K, radiation (h = 71.07 pm), 296 f 1 K. All data were corrected for Lorentz and polarisation effects as well as for absorption (DIFABS"1). The structures were solved by using SHELXS[I9], the refinements were calculated with CRYSTALS120J.

Refinement of 1: Minimum and maximum correction coefficients for absorption 0.744 and 1.035; weighting scheme w' = Chebychev polynomial for F, with three coefficients (8.72, 5.35, and 6.04). In the block matrix least-squares refinement [five blocks: the x, y , Z,

and U values of the anions as first, x, y and z of the catenane as second, the U values of the catenane as third, x, y, z , and U (Uiso for the disordered atoms, respectively) for the acetonitrile molecules as fourth and scale and A s , as fifth block] non-hydrogen atoms

PF6], 1346.6 [M+ - 2 PFs], 1201.6 [M+ - 3 PF,]. -

Liebigs Ann. 1995, 649-656

656 M. Bauer, W. M. Muller, U. Miiller, K. Rissanen, F. Vogtle

were refined anisotropically except those of the disordered solvent molecule.

Refinement of 4: Minimum and maximum correction coefficients for absorption 0.715 and 1.375; w' = Chebychev polynomial for F, with five coeficients (2.96, -4.89, -4.22, -6.32, and -3.14). In the block matrix least-squares refinement [five blocks: the x, y, z , and U values of the anions as first, x, y, z , and U values of the catenane as second, x, y, z , and 9, of the ordered acetonitrile molecules as third, the x, y, z , and U,,, for the unresolved electron density (treated as C atoms only) as fourth and scale and A Uis, as fifth block] non-hydrogen atoms were refined anisotropically except those of the solvent molecules. A quite large electron density could not be resolved and was therefore treated as eight carbon atoms with occupancy 0.5.

Refinement of 6: Minimum and maximum correction coefficients for absorption 0.751 and 1.146; w' = Chebychev polynomial for F, with five coefficients (-2.17, -19.8, -11.2, -9.28, and -6.12). Due to the very poor data, full matrix least-squares cascade refinement (the x, y, z , and U values of the anions and those of the macrocycle alternating) was applied. The non-hydrogen atoms were refined anisotropically except those with occupancy factor 0.5 (two of the anions) which were refined isotropically.

In all structures hydrogen atoms are calculated to their idealised positions (C-H distance 100 pm) and are included in the final structure factor -calculations with fixed isotropic temperature fac- tors ( U = 0.08 A*) but not refined[*'].

[l] A. Luttringhaus, F. Cramer, H. Prinzbach, F. M. Henglein, Lie- bigs Ann. Chem. 1958, 613, 185-198; reviews: G. Schill, Ca- tenanes, Rotaxanes, and Knots, Academic Press, New York, 1971; J.-C. Chambron, C. Dietrich-Buchecker, J. P. Sauvage, Top. Curr. Chem. 1993, 165, 131-162; C. 0. Dietrich-Buch- ecker, J.-P. Sauvage, Chem. Rev. 1987, 87, 795-810.

['I [2al R. Hoss, F. Vogtle, Angew. Chem. 1994, 106, 389-398; An- gew. Chem. Int. Ed. Engl. 1994,33, 375-384. - [2b] C. Dietrich- Buchecker, B. Frommberger, I. Liier, J.-P. Sauvage, F. Vogtle, Angew. Chem. 1993, 105, 1526-1529; Angew. Chem. Int. Ed. Engl. 1993, 32, 1434- 1437, and references cited there.

L3] D. B. Amabilino, P. R. Ashton, A. S. Reder, N. Spencer, J. F. Stoddart, Angew. Chem. 1994, 106, 1316-1319; Angew. Chem. Znt. Ed. Engl. 1994, 33, 1286-1290; Angew. Chem. 1994, 106, 450-456; Angew. Chem. Znt. Ed.Eng1. 1994, 33, 433-437, and references cited there.

c41 F. Vogtle, S. Meier, R. Hoss, Angew. Chem. 1992, 104, 1628-1631; Angew. Chem. Znt. Ed. Engl. 1992,31, 1619-1622; S . Ottens-Hildebrandt, S. Meier, W. Schmidt, F. Vogtle, ibid. 1994,106, 1817-1821; ibid. Int. Ed. Engl. 1994,33, 1767-1770; C. A. Hunter, J: Am. Chem. SOC. 1992,114, 5303-5311.

('1 T. Lu, L. Zhang, G. W. Gokel, A. E. Kaifer, .I Am. Chem. Soc. 1993, 115, 2542-2543; G. M. Gruter, F. J. J. de Kanter, P. R. Markies. T. Nomoto. 0. S. Akkerman. F. Bickelhaupt. ibid. 1993, 115, 12179-12180; M. Fujita, F. Ibukuro, H. Hggihara, K. Ogura, Nature 1994,367, 720-723.

L6] P. R. Ashton, T. T. Goodnow, A. E. Kaifer, M. V. Reddington, A. M. Z. Slawin, N. Spencer, J. F. Stoddart, C. Vicent, D. J. Williams, Angew. Chem. 1989, 101, 1404- 1408; Angew. Chem. Int. Ed. Engl. 1989,28, 1396-1400; P. R. Ashton, C. L. Brown, E. J. T. Chrystal, T. T. Goodnow, A. E. Kaifer, K. P. Parry, A. M. Z. Slawin, N. Spencer, J. F. Stoddart, D. J. Williams, Angew. Chem. 1991. 103. 1055-1058: Anpew. Chem. Int. Ed. End , u

1991,30, 1039-1642. u

r71 P. L. Anelli. P. R. Ashton. R. Ballardini. V. Balzani. M. Delgado, M.' T. Gandolfi, T. T. Goodnow,'A. E. Kaifer, D. Philp, M. Pietraskiewicz, L. Prodi, M. V. Reddington, A. M. Z. Slawin, N. Spencer, J. F. Stoddart, C. Vicent, D. J. Williams, .I Am. Chem. SOC. 1992, 114, 193-218.

[*I This substance was synthesized by us and Stoddartrg1 almost at the same time; it is the simplest basic compound with an unsymmetrical paraquat ring: F. Vogtle, W. M. Muller, U. Muller, M. Bauer, K. Rissanen, Angew. Chem. 1993, 1356-1358; Angew. Chem. Int. Ed. Engl. 1993,32, 1295-1297.

L91 D. B. Amambilino, P. R. Ashton, M. S. Tolley, J. F. Stoddart, D. J. Williams, Angew. Chem. 1993, 1358-1362; Angew. Chem. Int. Ed. Engl. 1993, 32, 1297-1308.

[lo] Reviews: e.g. S. Shinkai, 0. Manabe, Top. Curr Chem. 1984, 121,67; S . Shinkai, K. Shigematsu, Y. Honda, 0. Manabe, Bull. Chem. SOC. Jpn. 1984, 57, 2879-2884, and 12 previous com- munications "Photoresponsive Crown Ethers"; S . Shinkai in Bioorganic Chemistry Frontiers (Ed.: H. Dugas), vol. 1, Springer Verlag, Berlin, 1990, p. 161; F. Vogtle, Supramolekulare Chemie, 2. Aufl., Kap. 7, Teubner, Stuttgart, 1992; F. Vogtle, Supramol- ecular Chemistry, Wiley, Chichester, 1991, p. 207-229, paper- back 1993; V. Balzani, F. Scandola, Supramolecular Photochem- istry, Horwood, Chichester, 1991.

["I G. S. Hartley, J: Chem. SOC. 1938, 633-642. ['*I C. J. Brown, Acta Crystallogr. 1966, 21, 146-153; A. Mostad,

C. Romrning, Acta Chem. Scand. 1971,25, 3561 -3568. [131 R. C. Helgeson, T. L. Tarnowski, J. M. Timko, D. J. Cram, .I Am. Chem. SOC. 1977, 99, 6411-6418. - P. R. Ashton, C. L. Brown, E. J. T. Chrystal, K. P. Parry, M. Pietraszkiewicz, N. Spencer, J. F. Stoddart, Angew. Chem. 1991,103, 1058-1061; Angew. Chem. Int. Ed. Engl. 1991, 30, 1042- 1045; cf.

[l41 Cf.: P. R. Ashton, R. Ballardini, V. Balzani, M. T. Gandolfi, D. J.-F. Marquis, L. Perez-Garcia, L. Prodi, J. F. Stoddart, M. Ven- turi, J Chem. Soc., Chem. Comrnun. 1994, 177-180.

[lS] N. H. Wassermann, B. F. Erlanger, Chem.-Biol. Interactions 1981, 36, 251.

[I6] A. E. Kaifer, D. A. Gutowski, L. Echegoyen, V. J. Gatto, R. A. Schulz, T. P. Cleary, C. R. Morgan, D. M. Goli, A. M. Rios, G. W. Gokel, J Am. Chem. SOC. 1985,107, 1958.

[I7] W. Geuder, S. Hunig, A. Suchy, Tetrahedron 1986, 42, 1665. [I8] N. Walker, D. Stuart, Acta Crystallogr., Sect. A , 1983, 39, 158. L L 9 ] G. M. Sheldrick in Crystallographic Computing 3 (Eds.: G. M.

Sheldrick, C . Kruger, R. Goddard), Oxford University Press, Oxford, UK, 1985, p. 175-189.

KZo] D. Watkin, J. R. Carruthers, P. W. Betteridge, CRYSTALS, Chemical Chrystallographic Laboratory, Oxford, UK, 1990.

lz11 Further details of the crystal structure analyses are available on request from the Fachinformationszentrum Karlsruhe, Ge- sellschaft fur wissenschaftlich-technische Information mbH, D- 76344 Eggenstein-Leopoldshafen, on quoting the depository number CSD-58786, the names of the authors, and the jour- nal citation.

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azobenzene-based photoswitchable catenanes

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