Woo-Dong Jang and Takuzo Aida- Supramolecular Nanofiber Formation of Macrocyclic Dendrimer

8/3/2019 Woo-Dong Jang and Takuzo Aida- Supramolecular Nanofiber Formation of Macrocyclic Dendrimer

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Supr am olecular Na nofiber F orm at ion of Macrocyclic Dendr imer

Wo o - D o n g J a n g * a n d T a k u z o A i d a

Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo,7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Received April 20, 2004; Revised Man uscript R eceived J un e 18, 2004

ABSTRACT: Novel ma crocyclic dendr imer s (Scheme 2), ha ving two cis -1,3,5-cyclohexanetricarboxamide(1) or 1,3,5-benzenetricarboxamide units (3) in their core, were synthesized, and their self-assemblybehaviors were evaluated in solution. Infrared spectroscopy ofcis -1,3,5-cyclohexan etr icarboxamide coreddendrimer (1) in CHCl3 indicated tha t format ion of strong hydrogen-bonding inter actions is t aking placeamong the core units. The 1H NMR spectrum of1 in CDCl3 showed broadenings of all th e peaks, wh ichwere sharpened by adding one drop of CF 3CO 2H. GPC ana lysis sh owed t he format ion of self-assembledpart icles having ultrah igh molecular weight, whose average diameter was evaluat ed as about 140 nm byDLS measu remen t. AFM observation of the cast on mica film showed tha t 1 forms a fibrous assembly ofuniform thickness with a diameter of 6 nm. In sharp contrast to 1, 1,3,5-benzenetricarboxam ide u nitscored dendrimer (3) did not form a fibrous assembly under identical conditions because of the twistedarra ngement of the core u nits.

I n t r o d u c t i o n

Secondary and tertiary structures of natu ral macro-molecules such as polypeptides, polynucleotides, andpolysaccharides are mostly controlled by noncovalentinteractions. These interactions are very important inmacromolecular chemistry where hydrogen bonding a ndother weak reversible interactions can make a majorcontr ibution to designing n ew polymeric ar chitectur es.I n r e ce n t ye a r s, a n u m be r of con ce pt s h a ve b ee nproposed t hat use noncovalent interactions for theconstruction of a supramolecular polymeric assembly.1

To obtain a linear type supramolecular polymeric as-sembly,2 it is desirable to have interactions sufficientlystrong, directional, and sufficiently reversible to alter-nate covalent bonds. cis -1,3,5-Cyclohexanetricarbox-amide3 an d 1,3,5-benzenetricarboxam ide4 u n it s a r e

potent ial scaffolds for th e const ru ction of supr am olecu-lar polymeric assembly systems. Both of them exhibita discotic supramolecular assembly via intermolecularhydrogen bonding (Scheme 1). cis -1,3,5-Cyclohexane-tricarboxamide has t hree u nidirectiona l amide units inwhich the cis -1,3,5-cyclohexan etr icar boxam ide deriva-tives form a p hysical gel or viscoelast ic fluid depen dingon the solvents.3 1,3,5-Benzenetricarboxamide deriva-tives also form unidirectional hydrogen bonds with atypical helical ar ran gement within t he supr amolecularassembly structure.4

On the other hand, dendrimers are nanometer-sizedhyperbran ched macromolecules with well-predictablethree-dimensional shapes and potential building blocks

for th e const ru ction of organized functiona l ma terials.5,6

Since dendrimers have unique three-dimensional shapes,solution properties are predominantly dependent on theperipheral functiona lities, and core st ructur es ar e pos-sibly insulated from the outer environmen t.7 From thispoint of view, three-dimensional warping of th e su-pramolecular assembly system using dendrimer fram e-works has potentials for providing a very interestingaspect. In this paper, we demonstrate a novel fibroussupramolecular assembly8 formation of a dendrit ic

macrocycle with a significantly high molecular weightattr ibutable to intermolecular hydrogen bonding insolution.

R e s u l t s a n d D i s c u s s i o n

S y n t h e s i s a n d C h a r a c t e r i s t i c . A series of poly-(benzyl ether) dendrimers (Scheme 2) ha ving macro-

cyclic cores, which contain two cis -1,3,5-cyclohexane-tricarboxamide or 1,3,5-benzenetricarboxamide units,were synthesized and characterized by 1H N M R a n dMALDI -TO F -MS spectroscopy. Details of the syn-thetic methodology for the macrocyclic dendrimers areshown in Scheme 3. First, phth alimide was introducedto 3 ,5-di-tert-butyldiphenylsilyloxybenzyl alcohol (4) ac-cordin g to th e Mitsun obus coupling r eaction.9 Then, 5t hus obt ained w as r eact ed w it h Fr echet s dendr onbromide (6)10 to get phtha limide cored dendron (7),which was changed to amine core dendrimer (8) usinghydrazine. Tris-p-nitrophenyl-cis -1,3,5-cyclohexane tri-* Corresponding a uth or. E -mail: [email protected].

S c h e m e 1. H y d r o g e n - B o n d i n g - Me d i a t e dS e l f -A s s e m b l y S t r u c t u r e s o f

cis-1,3,5-Cyclohexanetricarboxamide (Right) and1,3,5-Benzenetricarboxamide (Left)

7325Macrom olecul es 2004, 37 , 7325-7330

10.1021/ma0492364 CCC: $27.50 2004 American Chem ical SocietyPublished on Web 08/25/2004


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carboxylate (10 ) prepa red by dicyclohexyl carbodiimide

mediated condensation of p-nitrophenol and cis -1,3,5-cyclohexan etr icar boxylic a cid (9). Tris-p-nitrophenyl-benzene tricarboxylate (13 ) was prepar ed by condensa-tion reaction of trimesoyl chloride (10 ) and p-nitrophenol.And then, 8 was rea cted with 10 or 13 to get precursorsfor the macrocycle 11 or 14, r espectively. 11 or 14 t husobtained was rea cted with 4,4-biphenyldiaminomethylto get the corresponding macrocyclic dendrimers 1 a nd3, r espectively. 1 has two different isomeric structur esbecaus e of t he or i ent at i on of am i de bonds of cor ecyclohexyl units. However, all the evaluation of 1 wa sperformed a s a m ixture of the two isomers because th etwo isomers were not distinguishable or separable bythe conventional analytic methods. The N-methylatedderivative macrocyclic dendrimer (2) was pr epar ed from

1 by alkali mediat ed coupling rea ction with MeI. All themacrocyclic dendrimers were highly soluble to thehalogena ted solvents or polar aprotic solvents, su ch a sCHCl3, CH 2Cl 2, CH 2ClCH 2Cl, DMF, DMSO, etc.

S p e c t r o s c o p i c S t u d i e s o f Ma c r o c y c l i c D e n d r i m -e r s . The infrar ed spectrum (IR) of CHCl3 solution of1(5.0 mM) displayed relatively broad absorption bandsat 3290 cm -1, with sh arp ba nds at 1640 and 1550 cm -1,which are chara cteristics of stretching vibrations of N -H , am i de I , and am i de I I , r es pect i vely.11 Thesespectral characteristics indicate that the amide groupsof 1 are hydrogen bonded to each other despite dilutedconcentration in solution. Very interestingly, however,t h e I R s pe ct r u m of C H Cl3 solut ion of 3 (5.0 mM)

exhibited pa ttern s quite different from th at of1, wheret h e N -H stretching vibration band was exhibited at

3390 cm -1 and stretching vibrations of amide I and IIwere exhibited a t 1660 a nd 1518 cm -1, respectively(Figure 1), indicating n o hydrogen bonding.

O n t he ot her hand, t he 1H NMR spectrum of 1 inCDCl3 (1 mM) displayed significan tly broad ban ds of allthe characteristic peaks (Figure 2a), whereas the 1HNMR spectrum of 3 in CHCl3 displayed simple sharppeaks. Th ese observations again indicate possible for-mation of molecular assembly via hydrogen bonding,which leads to the broadening of 1H NMR signals of1because of the restriction of conformational change inCDCl3. It is interesting th at a ll the pea ks of1 in CDCl3were changed to simple sharp peaks t o be identified bythe addition of a drop of CF 3CO 2H, a strong hydrogen-bonding acceptor (Figure 2b). These changes indicatethat th e CF 3CO 2H molecules dissociated the assembleddendrimers.

D y n a m i c L i g h t S c a t t e r i n g ( D L S ) a n d G e l P e r -m e a t i o n C h r o m a t o g r a p h y ( G P C ) . Figure 3 showsthe histogram profile of DLS result of 1 (0.06 mM) inCHCl3, which indicates the formation of quite a largeparticles. The average diameter of the particles wasevaluated as 142 ( 48 nm . However, 3 has insufficientlight scattering intensity in the DLS measurement tobe detected a s pa rticles. Therefore, th e a verage m olec-ular weight of particles was examined by GPC. Theresult showed tha t 1 exhibited a peak at extremely highmolecular weight region (Figure 4a), eluting at the timeof the exclusion limit of a column (TSKgel GMHXL

S c h e m e 2 . Ma c r o c y cl i c D e n d r i m e rs

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exclusion limit: 4 10 8, eluent: CHCl3). Interestingly,when t he solution containing a small amount of CF3-CO 2H was eluted, the retention time was significantlyincreased (Figure 4b). This observation agrees with the1H NMR result . As a non-hydrogen-bonding modelcompound, the N-methylated derivative (2) was n ewlysynthesized and unambiguously characterized by 1HNMR and MALDI-TO F -MS spectroscopy. The GPCprofile of2 exhibited a single shar p peak with th e sameretention time as the solution of1 cont aining CF 3CO 2H,indicating that the addition of CF 3CO 2H dissociated theassem bled ma crocyclic dendrim ers (Figure 4c). Consid-ering th e n umber of hydrogen-bonding sites, 3 also hasa possibility to form a supramolecular assembly. How-

ever, IR and 1H NMR spectra revealed that it was hardfor 3 to form hydrogen bonds. GPC analysis of 3 alsoexhibited a single sharp peak with the same retentiont i m e as 2, indicating t hat 3 does not associate underthe GPC condition (Figure 4d).

A tomic Force Microscopic (A FM) O bservation ofM a c r o c y c l i c D e n d r i m e r . To find the morphology ofthe dendrimer assembly, the CHCl3 solut ion of macro-cyclic dendrimers was spin-coated on a mica film andthen subjected to AFM. Clearly 1 formed as entangledfibrous structures (Figure 5a). With sufficient dilution

S c h e m e 3 . S y n t h e s i s o f Ma c r o c yc l i c D e n d r i m e rsa

a Reagents an d reaction conditions: (i) DEAD, PPh 3, phth alimide, in THF at 0 C for 1 h a nd 25 C for 11 h ; (ii ) KF, 18-crown-6ether, 6, in acetone reflux 3 h; (ii i) DCC, p-nitrophenol, in DMF a t 0 C for 1 h and 25 C for 12 h; (iv ) in DMF a t 60 C for 36 h;(v) in DMF at 60 C for 72 h; (vi ) H 2NN H 2H 2O in THF/EtOH (1/1) reflux 12 h; (vi i) p-nitrophenol, 1,3,5-collidine, in DMF at 0 C1 h and 25 C 12 h.

F i g u r e 1 . FT-IR spectra of1 (solid) an d 3 (dotted) in CHCl3.

F i g u r e 2 . 1H NMR spectra of 1 in CHCl3 (a) an d i n T FAincluded CHCl3 (b).

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of the solution, we could get a single filament of theassembly (Figure 5b,c). This f ibrous structure has ahomogeneous thickness of 6 nm, which agrees with thecomputer-aided calculated diameter of the dendrimer,indicating a linear supramolecular assembly formation.In contrast to the result of1, the AFM r esults of2 or 3showed a clearly different feature. Under identicalconditions, 2 or 3 exhibited only an agglomerated mass.

Even though both core units of 1 or 3 have six amidebonds, with a potential to form a self-assembled su-pramolecular structure, only 1 formed the supramo-lecular polymeric assembly. It is assumed that 1,3,5-benzenetricarboxamide derivatives are twisted into aheli cal ar r angem ent i n t he m os t s t able hydr ogen-bonding mode; thus, the two 1,3,5-benzenetricarbox-amide u nits in t he core of3 cannot form hydr ogen bondssimultaneously among the core units to form a lineartype supramolecular polymeric assembly. In sharpcontrast , the two cis -1,3,5-cyclohexanetricarboxamideuni t s i n t he cor e of 1 can form the hydrogen bondssimultan eously to reinforce each other, so th at 1 exhibitsan ultrahigh molecular weight and a fibrous assemblyformation even in solution.

T h e r m a l S t a b i l i t y o f A s s e m b l y . Variable-temper-at ur e 1H NMR measurement was performed to checkthe th erma l sta bility of hydrogen bond of self-assembleddendrimers (Figure 6). At room temperature, the 1HNMR spectrum of1 in o-dichlorobenzene-d4 displayedbroad bands of all the peaks, similar to that in CDCl3.O n r ai si ng t he t em per at ur e, t hes e br oad bands r e-ma ined up t o 150 C. At 150 C, all the peaks sh ar penedenough t o be i dent ifi ed. For com par is on w it h t hebehavior in solution, th e th erma l behavior of the dr iedsamples (1 a n d 2) was stu died by differential scanningcalorimetry (DSC). Ea ch sam ple was prepared by evapo-rat ion from its CHCl3 solution. Upon heating at a rateof 10 C min -1 from 0 C, both samples exhibited asingle endothermic thermal tr ansition, but t he temper-atu re was significant ly different. 1 exhibited an endo-thermic transition at 144 C (H ) -39.7 kJ mol-1), am uch hi gher t em per at ur e t han t hat of 2, which ap-p e a r e d a t 6 0 C (H ) -26. 6 kJ m ol-1) . The hightransit ion temperature of 1 m i ght be a r es ul t of t hehydrogen-bonding intera ction of amide units. Notably,the transit ion temperature of 1 was very close to thes har peni ng t em per at ur e of t he 1H N M R s pect r um ,revealing a very interesting a spect that the self-as-

sembly of1 remarkably stables even in solution.Synth esis of L ow Molecular Weigh t Model Com-p o u n d . In our attempt to prepare macrocyclic com-pound without dendrit ic substitution, benzylamine,instead of8, was reacted with 10 to prepare a precursorfor the macrocycle (Scheme 4). Benzylamine-substitutedcyclohexane derivative (15 ) thus obtained was r eactedwith 4,4-diphenyldiaminometh yl in th e identical condi-tion to that for 1. Unlike the case of 1, the reactionmixture formed an insoluble mass. By the MALDI-TO F -M S anal ys is of t hi s m as s , t he exi st ence of adimeric m acrocycle wa s definitely confirmed. However,purification of macrocyclic compound was impossiblebecause of the disordered network formed by hydrogenbonding. This means that the dendritic substitution is

importa nt for th e forma tion of a soluble assembly andmight control the ordered interaction among the coreamide groups. Therefore, th e supr amolecular assemblyformation of large den drimer possibly occurred by th ethree-dimensional warping of core groups by the den-dritic wedges, which may prevent a disordered networkformation and possibly stabilize hydrogen-bonding in-teractions because of the hydrophobic characteristics ofthe dendrit ic wedge in addition to possible van derWaals interaction.

E x p e r im e n t a l S e c t i o n

P r e p a r a ti o n o f D e n d r i m e r s: C h e m i c a ls . Chemicalswere u sed as received from commer cial sources (Aldrich, TCI).Solvents were freshly distilled according to literature methods.

F i g u r e 3 . Histogram analysis of DLS measur ement of1 inCHCl3 (0.06 mM).

F i g u r e 4 . GPC profiles of1 (a, b: including TFA), 2 (c), and3 (d).

F i g u r e 5 . AFM image of fibrous assembly of1.



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5. To a tetrahydrofuran (THF) solution (60 mL) of a mixtureof4 (9.0 mm ol), phth alimide (10.8 m mol), a nd tr iphenylphos-phine (10.8 mmol) was added 40% toluene solution of diethyl-azodicarboxylic acid (DEAD; 10.8 mmol), and the resultingmixture was stirred under Ar at 0 C for 1 h and 25 C for 11h. The reaction mixture was then evaporated to dryness, and

the residue was chromatographed on silica gel with CH 2Cl 2as eluent, wher e th e second fra ction was collected a nd evapo-rat ed to give 5 as transparent oil in 87% yield. MALDI-TOF -MS for C48H 48O4Si 2 m/z: calcd: 745 [M +]; foun d: 745. 1H NMR(CDCl3): 0.94 (s, 18H; tert-Bu), 4.47 (s, 2H; -CH 2-), 6.04(t, 1H; p-H in C6H 3), 6.30 (d, 2H; o-H in C6H 3), 6.03-7.48 (m,20H; -C6H 5), 7.69 and 7.76 (m, 4H, C6H 4 in phthalimide).

7. A acetone solution (20 mL) of a m ixture of5 (0.8 mmol),6 (1.6 mmol), and 18-crown-6 (0.2 mmol), containing KF (1.9mmol), was refluxed under Ar for 3 h. The reaction mixturewas poured into water (50 mL) and extracted th ree times withethyl acetat e (50 mL). The combined extracts were dried overanhydrous MgSO4 and chromatographed on silica gel withCH 2Cl 2 as eluent, where the third fraction was collected andfreeze-dried from benzene to give 7 as a white solid in 90%yield. MALDI-TO F -MS for C129 H 127NO 32 m/z: calcd: 2241

[M + K+]; found: 2243. 1H NMR (CDCl3): 3.74 (s, 48H;-OMe), 4.73 (s, 2H; -CH 2- N), 4.93 (s, 28H; -CH 2-), 6.35-6.65 (m, 45H; o, p-H in C6H 3), 7.62 an d 7.77 (m, 4H; C 6H 4 inphthalimide).

8. To a THF/EtOH (1:1) solution (20 mL) of 7 (0.72 mmol)w as ad d ed h y d ro u s h y d razi n e (1 0 mL ), an d t h e res u l t i n gmixture was r efluxed for 12 h. Then , insoluble fractions werefiltered off from the reaction mixture, and the filtrate waspoured into water (100 mL) and extracted three times withethyl acetat e (50 mL). The combined extracts were dried overanh ydrous MgSO4 and evaporated to dryness and th en freeze-dried from benzene to give 8 as a white solid in quantitativeyield. MALDI-TO F -MS for C121 H 125NO 30 m/z: calcd: 2073[M+]; foun d: 2075. 1H NMR (CDCl3): 3.71 (s, 48H; -OMe),4.78 (m, 28H, -CH 2-), 4.95 (s, 2H; -CH 2-N), 6.31-6.63 (m,48H; o, p-H in C6H 3).

10 . T o a D MF s ol u t ion (1 0 m L ) o f 9 (4.6 m mol) andp-nitrophenol (16.1 mmol) was added dicyclohexylcarbodiimide(DCC; 16.1 mmol), and the reaction mixture was vigorouslystirred at 0 C for 1 h and 25 C for 12 h. Insoluble fractionswere filtered off from the reaction mixture, and the filtratewas evaporated to dryness. Then, the resulting mixture was

washed with cold etha nol and recrystallized twice in hotethanol to get 10 as a white crystalline solid in 32% yield.MALDI-TO F -MS for C27H 21N 3O12 m/z: cal cd : 5 79 [M+];found: 579. 1H NMR (CDCl3): 1.90 (q, 3H; equat orial H ofcyclohexyl), 2.69 (m, 3H; axial H of CH 2 in cyclohexyl), 2.91(m, 3H; CH in cyclohexyl), 4.27 a nd 8.28 (m, 12H; H innitrophenyl).

11 . A DMF solution (10 mL) of a mixture of10 (0.43 mmol)a n d 8 (0.14 mmol) was vigorously stirred under Ar at 60 Cfor 36 h. The reaction mixture was poured into water andextracted with ethyl acetate. The combined extracts werewashed thr ee times with a n aqueous solution of 1 M NaOHand evaporated to dryness. The resulting mixture was thensubjected to r ecyclable preparative GPC, where the firstfraction was collected and freeze-dried from benzene to give11 as a w h it e s ol id i n 7 2% y ield . MAL DI-TOF-MS forC142H 141 N 3O39 m/z: calcd: 2514 [M + H +]; found: 2514. 1HNMR (CDCl3): 1.56-2.51 (m, 9H; cyclohexyl), 3.67 (s, 48H ;-OMe), 4.23 (d, 2H; CH 2-N), 4.84 (s, 28H; -CH 2-), 5.86 (t,1H; N -H), 6.28-6.56 (m, 45H; o, p-H in C6H 3), 7.08 and 8.06(m, 8H; C6H 4 in p-nitrophenyl).

13 . To a DMF solution (30 mL) of12 (13.8 mmol) was addedp-nitrophenol (48.3 mmol), and the reaction m ixture wasvigorously stirred at 0 C for 1 h and 25 C for 12 h. Thereaction mixture evaporat ed to dryness an d washed with coldethanol and then recrystallized twice in hot ethanol to get 13

as a white crystalline solid in 12% yield. MALDI-

TOF-MSfor C27H 15N 3O12 m/z: calcd: 573 [M+]; found: 573. 1H N MR(DMSO-d6): 7.71 and 8.38 (d, 12H; H in p-nitrophen yl), 8.91(s, 3H; C6H 3).

14 . A DMF solution of a mixture of 13 (0.09 m mol) and 8(0.75 mmol) was vigorously stirred under Ar at 60 C for 36h. The reaction mixture was treated in a manner similar tothat for the preparation of 11 to give 14 as a white solid in52% yield. MALDI-TOF-MS for C142H 135 N3O39 m/z: calcd:2529 [M + Na +]; found: 2531. 1H NMR (CDCl3): 3.73 (s,48H; -OMe), 4.50 (d, 2H; CH 2-N), 4.89 (m, 30H; -CH 2-),6.34-6.58 (m, 45H; o, p-H in C6H 3 of dendritic wedge), 7.36and 8.21 (d, 8H; C6H 4 in p-nitrophenyl), 8.76 and 8.95 (m, 3H;C6H 3 in core).

15 . A DMF solution of a mixture of 10 (0.69 mmol) andbenzylamine (0.35 mmol) was vigorously stirred under Ar at

60 C for 3 h. The r eaction m ixture was treat ed in a mann ersimilar t o that for the pr eparation of 11 to give 15 as whitesolid in 75% yield. MALDI-TOF-MS for C28H 25N 3O9 m/z:calcd: 547 [M+]; found: 547. 1H NMR (CDCl3): 1.84-2.76(m, 9H ; cyclohexyl), 4.45 (d, 2H ; CH 2-N), 5.82 (t, 1H; N -H ),7.24-7 . 3 4 (m, 5 H ; C6H 5), 7 .2 6 a n d 8 .0 6 (d , 8 H ; C 6H 4 inp-nitrophenyl).

1. A DMF solution of a mixture of11 (0.2 m mol) and 4,4-biphenyldiaminometh yl (0.2 mm ol) was vigorously st irredunder Ar at 60 C for 72 h. The reaction mixture was pouredinto water and extracted with ethyl acetate. The combinedextracts were washed three times with aqueous solution of 1M NaOH and evaporated to dryness. The resulting mixturewas then subjected to recyclable preparative GPC, where thefirst fraction, wh ich is exceeded in the exclusion limit of thecolumn, was collected and freeze-dried from benzene to give

11 as a w h it e s ol id i n 4 2% y ield . MAL DI-TOF -MS forC288H 294 N 6O66 m/z: calcd: 4918 [M + Na +]; found: 4919. 1HNMR (TFA included CDCl3): 1.65-2 . 3 7 (m, 1 8 H , H i ncyclohexyl) 3.75 (s, 90H, -OMe), 4.26 (m, 12H, CH 2-N), 4.94(d, 60H; -CH 2-), 6.40-6.65 (m, 90H; o, p-H in C6H 3), 7.16-7.40 (m, 8H ; C6H 4).

F i g u re 6 . 1H N MR s p ect ra of 1 in o-dichlorobenzene atdifferent temperatur es.

S c h e m e 4 . S y n t h e s i s o f L o w Mo l e c u l a r N o n d e n d r i t i c Mo d e l

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2. To a THF solution of a mixture of 1 (4 mol) and NaH(12 mol) was added MeI (12 mol) and vigorously stirredunder Ar at 25 C for 12 h. Insoluble fractions were filteredoff from the reaction mixture, and filtrate was evaporated todryness. Then, the resulting mixture was subjected to re-cyclable prepa rat ive GPC, where t he first fraction wa s collectedand freeze-dried from benzene to give 2 as a white solid inquant itative yield. MALDI-TOF -MS for C294H 306 N 6O66 m/z:calcd: 5002 [M + Na +]; found: 5002. 1H NMR (CDCl3): 1.62-2.32 (m, 18H , H in cyclohexyl) 2.89 (s, 18H; N-Me), 3.74(s, 90H, -OMe), 4.46-4.50 (m, 12H, CH 2-N), 4.93 (d, 60H;-CH 2-), 6.36-6.64 (m, 90H; o, p-H in C6H 3), 7.36-7.46 (m,8H; C6H 4).

3. A DMF solution of a mixture of 14 (0.03 mmol) and 4,4-biphenyldiaminomethyl (0.03 mmol) was vigorously stirredunder Ar at 60 C for 72 h. The reaction mixture was treatedin a manner similar to that for the preparation of11 to give 1as a white solid in 55% yield. MALDI -TOF-MS for C288H 282 -N 6O66 m/z: calcd: 4906 [M + Na +]; found: 4908. 1H N MR(CDCl3): 3.70 (s, 90H, -OMe), 4.42 (m, 12H, CH 2-N), 4.87(d, 60H; -CH 2-), 6.32-6.59 (m, 90H; o, p- H i n C6H 3 ofdendritic wedge), 7.17-7.30 (m, 8H; C6H 4), 8.00 and 8.31 (m,6H, C6H 3 in core).

M e a s u r e m e n t : I n s t r u m e n t s . 1H NMR spectra were mea-sured in CDCl3 or DMSO-d6 at 21 C on a JEOL GSX-270spectrometer operat ing at 270 MHz, where the chemical shiftswere determined with r espect t o CHCl3 ( 7.28 ppm) and CH 3-

SOCD2H ( 7.28 ppm). Matrix-assisted laser desorption ioniza-tion time-of-flight mass spectrometry (MALDI-TOF -MS) wasperformed on a Bruker model Protein TOF m ass spectrometerusing 9-nitroant hra cene (9NA) or indole acetic acid (IAA) asa m atr ix. FT-IR spectra were recorded on a J ASCO model FT/IR 610. Dynamic light scattering (DLS) measurements werecarried out using by an Otsuka model DLS-700 instr umen t at25 C.

G P C M e a s u r e m e n t s . Analytical GPC was carried out ona TOSOH model HLC-8020 equipped with TSKgel GMH XLcolumn as eluent of CHCl3 at 25 C. Recyclable preparativeGPC was carried out on a JAI model LC-908 equipped withJAIGEL 2H an d JAIGEL 3H column a s eluent of CHCl3 at 25C.

Atomic Force Microscopy (AFM). AFM was carried outon a J EOL model JSP M 4200. One drop of dilute solution of1

(0.2 mM) in CHCl3 was placed on a freshly cleaved micasurface and spin-cast for AFM observation.

C o n c l u s i o n

In our dem onstra tion of th e self-assembly of dendriticmacrocycle, spectroscopic studies revealed that thehydr ogen bonding am ong cor e am i de gr oups i s t hedriving force for the supramolecular assembly. Ultra-high m olecular weight assembly formation of the m ac-rocyclic dendrimer 1 was observed by GPC and DLSanalysis, whereas 3 cann ot form a high molecularweight supra molecular assembly, presumably becauseof the twist arran gement of hydrogen bonds betweencore 1,3,5-benzenetr icarboxamide u nits. The linear stack-

ing of macrocycle may provide a tubu lar stru cture.

12 1exhibited a fibrous su pram olecular assembly structur eby AFM. It is possible th at the fibrous supra molecular

assembly structure of dendritic macrocycle also havetubular internal space. A novel ultrah igh molecularweight supra molecular polymeric assembly which iscomposed of macrocyclic units was designed, and itssolubility was contr olled by introducing of a dendriticarchitecture.

R e f e re n c e s a n d N o t e s

(1) Sherrington, D. C.; Taskinen, K. A. Chem. Soc. Rev. 2001,

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Woo-Dong Jang and Takuzo Aida- Supramolecular Nanofiber Formation of Macrocyclic Dendrimer

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