redoxactive polymers synthesis

7/28/2019 Redoxactive Polymers Synthesis

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R e d o x - a c t i v e p o l y m e r s : s y n t h e s i s a n de x c h a n g e r e a c t i o n o f a m i n o c o m p o u n d sc o n t a i n i n g a c y c l i c d i s u l f i d eM a r i o C a s o l a r o * a n d E l e n a B u s iDipart imento di Chimica, Universi t~ di Siena, Piano dei Mantel l ini 44, 53100 Siena, I taly(Received 29 March 1993)

Tw o mo noa m idate d amino com pounds, bearing the cyclic disulfide mo iety of lipoic acid, were preparedby imidazole group transfer w ith aliphatic diamines (1,3-diaminopropane and piperazine). The products,characterized by spectroscopic m ethod s (1H nuclear magnetic resonance an d Fo urier-trans form infra-red),were studied in solution. Basicity constants for the protonation of the basic nitrogens were evaluated inaqueo us media, and redox properties in dimethylsulfoxide, by cyclic voltammetry. Insoluble polymers wereobtained by polymer-analogue exchange reaction of the mon oam idated com poun d with a benzotriazoleresidue present in preformed poly(N-acryloylbenzotriazole). A copolymer of the same monomer withN-vinylpyrrolidinone was soluble in solvents, giving a response in cyclic voltammetry. Its positive ano depeak w as slightly higher than that of the simple mon oam idated compounds.(Keywords: redox polymer; ipoamidH mine; exchange reaction)

I N T R O D U C T I O NA c l a ss o f r e a g e n t s c o n t a in in g r e d o x - a c t i v e mo ie t i e s i sb a s e d o n c o m p o u n d s t h a t h a v e t h e f i v e - m e m b e r e ddisu l f ide r ing of l ipo ic ac id an d i t s d e r iva t ives 1-3 .T h e s e c o m p o u n d s , w i t h a n - S - S - b o n d , a r e u s e d a sp r e c u rs o r s t o i n t r o d u c e - S H g r o u p s i n t o p o l y m e r s ,imp r o v in g t h e p o w e r f u l r e d u c in g c h a r a c t e r f o r d i su l f i d eb r id g e s i n p r o t e in s 4 . Mo r e o v e r , s e l ec t iv e r e d u c t io n o fo r g a n i c m o l e cu l e s c a n b e o b t a i n e d b y p o l y m e r - s u p p o r t e dc a t a ly s t s b a se d o n d i t h io l- i ro n ( i i ) c o mp le x e s 5.T h e sy n th e s i s o f r e a c ti v e p o ly me r s b y p o ly m e r i z a t i o no f th e c o r r e s p o n d i n g v i n y l m o n o m e r s c a r r y i n g f u n c t i o n a lg r o u p s m a y b e d i f f ic u l t o r e v e n imp o ss ib l e , e sp ec i a ll y i ft h e d e s i r e d f u n c t i o n r e t a r d s o r i n t e r f e re s w i th t h e r a d i c a lp o l y m e r i z a t i o n p r o c e ss 6. A w a y t o o b t a i n p o l y m e r s w i t hsp e c i a l i z e d f u n c t i o n s w a s r e p o r t e d b y F e r r u t i e t al . 7-9 .I t i s a n i n d i r e c t r o u t e b a se d o n t h e e x c h a n g e o fa min e s , b e a r in g t h e d e s i r e d g r o u p s a s su b s t i t u e n t s ,w i th t h e b e n z o t r i a z o l e r e s id u e o n p r e f o r me d p o ly ( 1 -ac ry loylbenzot r iazo le )7 ,10 .

T h e a i m o f th i s p a p e r w a s t o p r e p a r e t w o n e w a m i n oc o mp o u n d s b e a r in g t h e c y c l i c d i su l f i d e :H2N-(CH2 3-NH-C=O H-N IgC---O

(CH2)4

1 _zo b t a i n e d b y m o n o a m i d a t i o n o f l i po i c a c i d w i t hh i s - p r ima r y ( 1 , 3 - d i a min o p r o p a n e ) a n d b i s - s e c o n d a r y* To who m correspondence should be addressed0032-3861/94/020360-07 1994 Butterworth-HeinemannLtd.3 6 0 P O L Y M E R , 1 9 9 4 , V o lu m e 3 5 , N u m b e r 2

( p ip e r a z in e ) a min e s . T h e a min o l ip o y l d e r iv a t i v e w a si n s e rt e d i n a p o l y m e r m a t r i x b y e x c h a n g e r e a c t i o n w i t hth e b e n z o t r i a z o l e r e s id u e . T h e r e d o x p r o p e r t i e s o f as o l u b l e c o p o l y m e r ( N - v i n y l p y r r o l i d i n o n e - c o - l - a c r y l o y l -b e n z o t r i a z o l e ) i n c o r p o r a t i n g 1 , e v a lu a t e d b y c y c l i cv o l t a m m e t r y , w e r e c o m p a r e d w i t h t h o s e o f t h e c o r re -s p o n d i n g l o w - m o l e c u l a r -w e i g h t a n a l o g u e s .

E X P E R I M E N T A L S E C T I O NM a t e r i a l s

c t - L ip o i c a c id a n d 1 , 1 ' - c a r b o n y ld i imid a z o l e w e r ep u r c h a s e d f r o m F l u k a a n d u s e d w i t h o u t f u r t h e rp u r i f i c a t i o n . N - V in y lp y r r o l i d in o n e ( f r o m F lu k a ) a n da c r y lo y l c h lo r id e ( f r o m A ld r i c h ) w e r e d i s t i l l e d u n d e rr e d u c e d p r e s su r e b e f o r e u se . C h lo r o f o r m ( f r o m B a k e r )w a s r e p e a t e d ly w a sh e d w i th d o u b le - d i s t i l l e d w a te ra n d d r i ed o v e r C a F 2 . A n h y d r o u s p i p e ra z i n e ( f ro mE g a - C h e mie ) , 1 , 3 - d i a min o p r o p a n e ( f r o m A ld r i c h ) a n dt r i e th y l a m in e ( fr o m C . E r b a ) w e r e u se d a s r e c e iv ed .Spec t roscopic measurement s

1 H n . m . r , w a s p e r f o r m e d a t 2 0 0 M H z o n a B r u k e rA C 2 0 0 s p e c t r o m e t e r i n d e u t e r a t e d d i m e t h y l s u l f o x i d e( D M S O - d r ) u s i n g t e tr a m e t h y l s i l a n e ( T M S ) a s i n t e r n a lreference. F T i . r . s p e c t r a w e r e r u n o n a P e r k i n - E l m e rM 1 8 0 0 s p e c t r o p h o t o m e t e r f r o m K B r p e l l e t s ( p o w d e r yc o m p o u n d s ) a n d a. t . r . /FT i . r , sp e c t r a f r o m f i lms ( r u b b e r yc o m p o u n d s ) .Poten t iome t r i c and v i s comet r i c measurement s

P o te n t io me t r i c t i t r a t i o n s w e r e c a r r i e d o u t a t 2 5 C in0 .1 M N a C 1 b y a p r e v io u s ly d e sc r ib e d p r o c e d u r e 11 u s in gc o m p u t e r i z e d a n a l y t i c a l d e v i c e s ( R a d i o m e t e r P H M - 8 4a n d M u l t i d o s i m a t p i s t o n b u r e t t e ) c o n n e c t e d t o a n


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Ol ive tt i M20 com puter . T i tra t ions were made au tomat i ca l lyb y t h e a d d i t i o n o f s t a n d a r d 0 .1 M N a O H t o a s o l u ti o no f t h e a m i n o c o m p o u n d i n th e p r o t o n a t e d f o rm . T h et i t ra t i o n d a t a w e r e s t o r e d o n a f l o p p y d i s k a n d t h e b a s i c it yc o n s t a n t v a l u e s e v a l u a t e d b y t h e S u p e r q u a d p r o g r a m 12,o n a n O l i v e t t i M2 8 c o mp u t e r . Table 1 s u mma r i z e s t h ee x p e r i me n t a l d e t a i ls o f t h e p o t e n t i o me t r i c me a s u r e me n t s .In t r ins i c v i scos i t i es were measured a t 30C wi th anU b b e l o h d e v i s c o m e te r c o n n e c te d t o a n a u t o m a t i c S c h o t t -G e r a t e A V S 3 1 0 t i me r .Cyclic vol tammetry measurements

Cy c l i c v o l t a m me t r y ( c . v .) w a s p e r f o r me d a t a mb i e n tt e mp e r a t u r e i n a n i t r o g e n a t mo s p h e r e w i t h a BA S 1 0 0 Amu l t i p u r p o s e v o l t a mme t e r i n a c e t o n i t r i l e a n d d i me t h y l -s u lf o x id e ( D M SO ) c o n t a in i n g 0 .1 M t e t r a b u t y l a mm o n i u mp e r c h l o r a t e a s s u p p o r t i n g e l e c t r o l y t e 13. P l a t i n u me l e c t r o d e s w e r e u s e d f o r t h e w o r k i n g a n d c o u n t e r -e l e c t r o d e s , t o g e t h e r w i t h a s a t u r a t e d a q u e o u s c a l o me le lec t rode .Synthesis o f N -l ipo yl- l ,3-diaminop ropane [1 ]

c t -L ipo ic ac id (5 .00g , 24 .2mmol ) was d i s so lved inanh ydr ous and a l coho l - f ree ch lo ro fo rm (30 ml ). So l id1 ,1 ' -carbony ld i imidazo le (5 .00g , 30 .8 mm ol ) wa s add edin smal l po r t ion s w i th s ti r r ing un t i l bubb l ing cease d over5 min . Th i s so lu t ion was s lowly added to a so lu t ion o f1 ,3 -d iam inopropa ne (8 .79 g , 118 .6 mm ol ) in a l coho l - f reeCHC13 (20 ml ) under s t i r ring in an i ce ba th . S t i r ring wascon t inued fo r 0.5 h in the co ld a nd fo r 0 .5 h a t a mb ien tt e mp e r a t u r e . T h e l i mp i d y e l l o w s o l u t i o n w a s w a s h e d w i t ha q u e o u s s o d i u m c h l o r i d e (1 0 w t % , 3 x 5 0 ml ) a n d d o u b l e -d i s t il l ed w ater (3 50 ml ) . Then the so lu t ion was d r i edo v e r s o d i u m s u l f a t e a n d t h e s o l v e n t r e mo v e d u n d e rredu ced pressure . T he yield was 6 .5 g (96%). Analysis:C, 47 .4%; H, 7 .9%; N, 9 .6%. C llH22N2OS2 .H20requ i res : C, 47 .1%; H, 8 .6%; N, 10 .0%.Synthesis o f 4-1ipoylpiperazine [2-1

~-Lipo ic ac id (5 .00g , 24 .2mmol ) was d i s so lved inanhydrous and a l coho l - f ree CHC13 (40ml ) . So l id 1 ,1 ' -carbo ny ld i im idazo le (5 .00g , 30 .8 mm ol ) was ad ded insmal l po r t ions un t i l bubb l ing ceased under s t i r r ing . Th i ss o l u t io n w a s s l o w l y a d d e d t o a s o l u t io n o f a n h y d r o u sp iperaz ine (10 .4g , 120 .7mmol ) d i s so lved in the sameso lven t C HC I 3 (30 ml ) und er s t ir r ing and coo l ing . Thei ce b a t h w a s ma i n t a i n e d f o r 1 0 mi n a n d t h e n t h e s o l u t i o nw a s k e p t a t a mb i e n t t e m p e r a t u r e f o r 1 h . T h e y e l l o ws o l u t i o n w a s w a s h e d w i t h a q u e o u s s o d i u m c h l o r i d e(10 wt% , 4 x 40 m l ) and doub le-d i s t i l l ed wate r (3 x 50 ml ).T h e n i t w a s d r i e d ( N a 2 SO 4 ) a n d t h e s o l v e n t r e mo v e dunder reduced p ressu re . The y ie ld was 5 .3g (75%).Analys is : C, 49 .8%; H , 7 .7%; N, 9 .5%. C 12H 22N 2OS 2.H20requ i res : C, 49 .3%; H, 8 .3%; N, 9 .6%.

R e d o x - a c t i v e p o ly m e r s : M . C a s o l ar o a n d E . B u s iSynthesis o f poly(1-acrylo yl-4-1ipo lpiperazine)

T h e l i mp i d y e l l o w s o l u t io n ( 1 0 w t % ) o f 1 - a c ry l o yl -4 -1 ipoy lp iperaz ine and azob i s i sobu ty ron i t r i l e (AIBN)(0 .1 m ol% ) in 1 ,4 -d ioxane was purg ed w i th n i t rogen ; thereac t ion m ix tu re w as a l lowed to reac t a t 60C fo r 24 hwhi le the po lymer p rec ip i t a t ed ou t .The monomer 1 -acry loy l -4 -1 ipoy lp iperaz ine was ob-t a ined b y d ropw ise add i t ion o f acry loy l ch lo r ide (0.01 mol )t o c o m p o u n d 2 (0 .0 1 mo l ) in a n h y d r o u s c h l o r o f o r m a n di n t h e p r e se n c e o f tr i e th y l a mi n e . T h e t e mp e r a t u r e w a sma i n t a i n e d a t 0 C f o r 1 5 mi n a n d t h e n r a i s ed t o a m b i e n tt e mp e r a t u r e o v e r 1 h . T h e s o l u t io n w a s w a s h e d w i thw a t e r , H C1 (1 M) , w a t e r , a q u e o u s N a H C O 3 ( 1 0 w t % ) ,water and f inal ly dried (Na2SO4). Analysis : C, 53.9%; H,7 . 3 % ; N , 8 . 1 % . C1 5 H 2 4 N 2 0 2 S2 '0 . 2 5 H 2 0 r e q u i r e s : C ,54 .1%; H, 7 .4%; N, 8 .4%.Synthesis o f copolymer (poly(ABT-co-VPy))

T h e m o n o m e r s o l u t i o n , w h i c h c o n s i s te d o f N -acry loy lbenzo t r i azo le (ABT) (0 .858g , 0 .0050mol ) , N-v iny lpyrro l id inone (VPy) (1 .15g , 0 .010mol ) and 1 ,4 -d i o x a n e ( 7 ml ) , w a s d e o x y g e n a t e d a n d t h e r e a c t i o ninit iated with AIB N (15 mg). The m ixture was therm ostat teda t 7 0 C i n a n o i l b a t h a n d p o l y me r i z a t i o n w a s a l l o w e dto p roce ed to com ple t ion in 24 h , under n i t rogen . Th ecop o lym er was p rec ip i t a t ed in d ie thy l e ther (100 ml ) andt h e w h i t e p o w d e r r e c o v e r e d w a s w a s h e d w i t h t h e s a mesolvent . Yield (dry we ight) was 1 .88 g . Int r insic viscosi ty[ r/ ] =0 .1 6 d l g - 1 ( in c h lo ro fo rm a t 30C) .Exchange react ions

A mi x t u r e o f c o p o l y me r (0 .5 0 g , 4 3 w t % A BT r e s id u e s )a n d t r i e th y l a mi n e ( 2 mo l ) , d i s s o lv e d in a n h y d r o u sc h l o r o f o r m ( 1 0 ml ), w a s a d d e d t o a CH CI 3 s o l u t io ncon ta in ing a tw o-fo ld excess o f 1 (0 .88 g , am ino g ro upcon te n t 75 wt% ) . The mix tu re was l e f t t o reac t in theco ld ( ice ba th ) w i th s t i rr ing fo r 1 h . Then i t was m ain ta ineda t a mb i e n t t e mp e r a t u r e o v e r n i g h t . T h e c o p o l y me r w a sprec ip i t a t ed in n -hexane (100 ml ) and w ashed wi th ho tCHC13 (40 ml) unde r reflux. The res idu e was a pale yel lowp o w d e r , s o l u b le o n l y i n h o t D M SO . Y i e ld w a s 0 . 8 0 g .In t r ins i c v i scos i ty [ r/ ] =0 .14 d l g - 1 ( in D M S O a t 30C) .Exch ange reac t ions o f po ly (1 -acry loy lbenz o t r i azo le)(po ly (ABT) , I -r /] = 1 .02 d l g -Z) wi th com pou nds 1 an d 2w e r e p e r f o r me d i n D MSO ( 2 5 ml ) a t mo l a r r a t i o s 1 : 1(0 .68 g o f 2 , amino g rou p con te n t 93 wt% , 2 .30 mm ol ;0.40 g poly(ABT), 2 .30 mm ol) an d 1:1 .5 (1 .52 g of 1 , am inog r o u p c o n t e n t 7 5 w t % , 4 . 3 4 mmo l ; 0 . 5 2 g p o l y ( A BT ) ,3 .00 mm ol ) , respec tive ly . The so lu t ion was a l lowed toreac t in the p resence o f t r i e thy lamine a t am bien tt em pera tu re fo r 24 h . In a l l cases, the so l id p ro duc t w asi s o l a t e d b y p o u r i n g t h e r e a c t i o n mi x t u r e i n t o a n e x c e s sof ace tone . The d r i ed f ine pow der y ie lded 0 .54g

Tab le 1 Experimental details of potentiometri c measure ments~ in 0.1 M NaCI at 25CTL x 103 Ta+ 103 C x

Comp ound (mol) (mol) (mol dm - a) pH range Points1 0.1677 0.4540 - 0.1193 8.39-10.21 39

0.2731 0.0000 0.1138 10.28-6.28 252 0.2966 0.5016 -0 .1 48 4 5.71-8.29 18

0.2593 0.4552 -0 .1 48 4 7.66-10.02 31~TL= initial a mount of ligand; TH+ = initial a mount of hydrogen ions; Cr = titrant concentration (negative values refers to Na OH solution)

POLYMER, 1994, Vo lume 35, Number 2 361


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Red ox -ac t i ve po l ym ers : I V /. Caso la ro and E. B u s ifo r the subs t i tu t ion o f 2 , and 0 .93 g fo r th a t o f 1 .Analys i s (der ived f rom 2): C, 53 .9%; H , 6 .0%; N , 10 .9%.Analys i s (der ived f rom 1) : C, 48 .7%; H, 7 .1%; N, 7 .9%.(C14H24N202S2 .1 .5H20)x requ i res : C, 48 .9%; H, 7 .9%;N , 8 . 1 % .R E S U L T S A N D D I S C U S S I O NLow-molecular-weight compounds

Synthesis and structures. T h e t w o c o m p o u n d s 1and 2 , con ta in ing the cyc l i c d i su lf ide and the f ree am inogroup , were p repared wi th a fa i r y i e ld in two reac t ionsteps (Scheme 1). Fi rs t , t he imidazo l ide was p repared

CHCI3

! ~ ( C H 2 ) 4 ~ - N ~ N

+ d i a m i n e (1 ,3-d iarn inopropane orp iperazine)

C H 2 ) 4 - R ~ -S c h e m e 1

by add i t ion o f 1 ,1 ' -carbony ld i imidazo le to ~- l ipo icac id , in anhydrous and a l coho l - f ree ch lo ro fo rm. Theso lu t ion o f imidazo l ide w as pour ed in to a l a rge excesso f b i s- p r i ma r y ( 1 , 3 - d i a mi n o p ro p a n e ) o r b i s - s e c o n d a r y(p iperaz ine) amine . The amino l ipoy l der iva t ive ob ta inedwas a b r igh t o range , rubbery so l id . The so l id p roductw a s n o t s o l u b l e i n c h l o r o f o r m a t a mb i e n t t e mp e r a t u r e ,b u t w a s s o l u b l e in h o t C H C I 3 a n d s o me o t h e r o r g a n i cso lven t s (ace ton i t r i l e , d imethy l su l fox ide) . The s t ruc tu reof the p rod uct w as charac te r i zed b y e l ementa l ana lys is ,in f ra -red and 1H n .m. r, spe c t roscopy . E lem enta l ana lys i srevea led a res idua l water molecu le . Th i s may be re l a t edt o t h e p r e s e n c e o f h y d r o p h i l ic c o m p o n e n t s , s u c h a s a mi d oa n d p r i ma r y o r s e c o n d a r y a mi n o g r o u p s . T h e f o r ma t i o nof the am id ic l inkage w as revea led by in f ra - red ana lys i s .F igure I s h o w s t h e F T i . r . s p e c t r a o f t h e t w o c o m p o u n d s .Co mp o u n d 1 s h o w e d t w o c h a r a c t e r i s t i c f r e q u e n c i e s f o rt h e a mi d o g r o u p : a mi d e I a t 1 6 40 c m - 1 a n d a m i d e I I a t1 5 50 c m - 1 . O n l y t h e a m i d e I a t 1 6 30 c m - 1 w a s f o u n d i nc o m p o u n d 2 d u e t o t h e p r e s e n c e o f t h e p i p e r az i n e r i ng .Pr o to n n .m. r, spec t ra ag reed wi th the p rop ose d s t ruc tu re .F i#ure 2 s h o w s t h e 1 H n .m . r, o f c o m p o u n d 1 inD M SO - d 6 . T h e c h e m i c a l sh if ts f o r b o t h c o m p o u n d s a r er e p o r t e d i n T ab le 2 t oge ther wi th tha t o f s imple l ipo ica c id , b y w a y o f c o mp a r i s o n .Physicochemical properties. T h e e l e c tr o c h e mi c a l a n dt h e r mo d y n a m i c ( b a s ic i ty c o n s ta n t s ) p r o p e r t i e s o f t h e t w os y n t h e t i c c o mp o u n d s w e r e e v a l u a t e d i n s o l u t i o n . T h eb a s i c it y c o n s t a n t f o r t h e p r o t o n a t i o n o f t h e f r ee a mi n og r o u p w a s e v a l u a t e d i n 0 .1 M N a Cl a t 2 5 C f r o mp o t e n t i o me t r i c d a t a . T i t r a t io n s w e r e p e r f o r me d w i t h t h ea d d i t i o n o f s t a n d a r d 0 .1 M s o d i u m h y d r o x i d e t o as o l u t io n o f i o n iz e d a mi n o c o m p o u n d i n t h e p r e s e n c e o fa l a rge excess o f hydro ch lo r i c ac id . Sharp end-p o in t s o fthe po ten t iomet r i c t i t ra t ion cu rves a l lowed re l i ab led e t e r mi n a t i o n o f t h e f r e e b a si c n it r o g e n s p r e s e n t i n b o t hc o m p o u n d s . T h e s o l u t i o n b e c a me c l o u d y w h e n t h e a m i n og r o u p r e a c h e d a c o m p l e t e ly u n c h a r g e d s t at e , b e c a u s e t h ef r e e c o mp o u n d i s i n s o l u b l e i n w a t e r . A mi n o g r o u p

3OOO 2O00

Figure 1

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1800 1200 800cm-1

A . t . r . / F T i . r . o f ( a) c o m p o u n d 1 a n d ( b ) c o m p o u n d 2

3 6 2 P O L Y M E R , 1 9 9 4 , V o l u m e 3 5 , N u m b e r 2


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R e d o x - a c t i v e p o l y m e r s ." M . C a s o l a r o a n d E . B u s i

,/

, . . . . . . . . . . . . ! . . . . . . . . . . . . . . . . . i . . . . . . . . . . . . . i . . . . . . . . . . . . . . . ! . . . . . . . . . . . . . . . . . . i . . . . . . . . . . . . . . . . . . i . . . . . . . . . . . . . . . . . . ! . . . . . . . . . . . . . . . . . . i . . . . . . . . . . . . . . . . . . ! . . . . . . . . . . . . . . . . . . i9 . 0 0 0 . 0 0 7 . 0 0 6 . 0 0 S . O 0 4 . 0 0 3 . 0 0 2 . 0 0 I . O 0PPHFigure 2 P ro to n n .m. r, spec t rum of com pou nd 1 in DM SO-d 6 . The inse t shows the 1H n .m. r , o f the a - l ipo ic ac id in the same so lven t

Tab le 2 P ro to n n .m. r, chemica l sh if ts (DM SO -d6 /TM S) o f low-m o l e c u l a r -w e i g h t c o m p o u n d s_ ~ / s - - s

R = -CH 2-C _2-CH.2-C_H.2 CH /G F E D C

B A

6, JS t ruc tu re (Hz)

R-OH H

NH2 NILII

~ u .R

E1 NIt N \

n c~ CH~ M\N /I

R

P H \ C / H X(2 __H/ = ~= 0. I N . \

tR

Lipoic acid12 (s, 1H; H); 3.72-3.56 (m, 1H; C); 3.37-3.06(m, 2H ; bO; 2.44 (q, 2H , J = 7; E); 2.24 (t, 2H , J = 10;G); 2 .00-1.79 (m, 2H; D); 1 .79-1.30 (m, 4H ; A, B)Compound 17.93-7.75br (m, 2H; N, H); 3.74-3.55 (m, 1H; C) ;3.30-2.90 (m , 8H; I , L, M , tO; 2.50-2.34 (m , 2H; E);2.19 (t , 2H, J = 10; G); 2 .00-1.82 (m, 2H; D);

1.80-1.30 (m, 4H ; A, B)

Compound 23.72-3.55 (m, 9H; I , H , L, M, C); 3 .30-3.10(m, 2H; F); 2.86br (s, 1H; N); 2.75-2.59 (m, 2H;E); 2.60 (t, 2H, J = 10; G); 2.10-1.80 (m, 2H; D);1.79-1.31 (m, 4H; A, B)

1-Acrylofl-4-1ipoylpiperazme6.83 (q, 1H, JQx = 18, JPx = 12; X); 6.20-5.65(2q, 2H, JPo = 4; P, Q); 3 .74-3.40 (m, 9H; H , I , L,M , C); 3 .25-3.09 (m, 2H; F); 2 .55-2.40 (m, 2H; E);2.36 (t , 2H, J = 9 ; G); 2 .00-1.80 (m, 2H ; D);1.80-1.35 (m, 4H ; A, B)

Tab le 3 Bas ic i ty o f mo noam ida ted d iamines a t 25C in 0 .1 M NaC1C o m p o u n d L o g K R e f.

. t ~ ' ~ O HS , . _ / II I 9 .571(10) b This pape r~( CH2 4-C-N-(CH2 3-NH2H2N-(CHz)3-NH2 10.52 148.74

2-O-~-I~H(CH2 3-NH2

CH2ICH-(~-N-(CH2)3-NH2

, I

s 0

2 I ~ ( C H 2 ) 4 2 _ ~ N _ .x . _ . /

H _N / - - XN _Hk . . . . ]

9.65 16

9.31 a 10

7.77(6)b

9.71 145.59

T h i s p a p e r

CH2I , - - ,CH -~-N N-H'1 , x..../

7.13" 17

"Calcu la ted a t a degree o f p ro tona t ion c t = 0 .5b Va lues in pa ren theses a re s tandard dev ia t ions

P O L Y M E R , 1 9 9 4 , V o l u m e 3 5 , N u m b e r 2 3 6 3


5/7

Redox-active polymers: M. Casolaro an d E. Bu sic o n t e n t w a s 7 5 % a n d 9 3 % r e s p ec t iv e l y f o r c o m p o u n d s1 and 2 . The bas ic i ty cons tan t s ( log K) a re repo r t ed inTable 3, t o g e t h e r w i t h t h o s e o f l o w - mo l e c u l a r -w e i g h t a n dp o l y me r i c a n a l o g u e s , f o r c o mp a r i s o n . I n b o t h c a s e s ,c o m p o u n d s 1 a n d 2 s h o w e d o n l y a s in g le l o g K v a lu e .I t s ma g n i t u d e w a s l o w e r t h a n l o g K 1 a n d h i g h e rt h a n l o g K 2 o f t h e c o r r e s p o n d i n g s i mp le d i a mi n e s(1 ,3 -d iamino propane and p iperaz ine) a4. Th i s depen dson the induct ive e f fec ts o f the ne ighbo ur ing am idog r o u p i n m o n o a m i d a t e d c o m p o u n d s 1 a n d 2 . I n t h ec a s e o f c o mp o u n d 1 , t h i s e f f e c t c a n b e c o mp a r e dw i t h t h e p u r p o s e l y s y n t h e s i z e d b e n z y l o x y c a r b o n y l - l , 3 -p rop ane d iam inC s , wh ich show s s imi la r log K va lues 16 .Fu r t h e r c o mp a r i s o n c a n b e ma d e w i t h p r e v i o u s l ys tud ied v iny l po lymers car ry ing the s imple d iaminec o n d e n s e d a t o n e e n d ~a T . T h e u n c h a r g e d p o l y me r , a tz e r o p r o t o n a t i o n , s h o w s a l o g K v a l u e c l o s e to t h a to f t h e c o r r e s p o n d i n g l o w - m o l e c u l a r- w e i g h t c o mp o u n d .Th i s fac t s t rong ly supp or t s the va l id i ty o f com par ingp o l y e l e c tr o l y te s a n d l o w - mo l e c u l a r - w e i g h t c o mp o u n d sw i t h a mi n o f u n c t io n a l g r o u p s , a s f o u n d f o r v in y l p o l y me r sc a r r y i n g c a r b o x y l g r o u p s I s .T h e e l e c tr o c h e mi c a l b e h a v i o u r i n d i me t h y l su l f o x id e o fc o m p o u n d s 1 a n d 2 s h o w e d a c y c l ic v o lt a mm e t r i c ( c. v.)response a t a p la t inum e lec t rode (Figure 3). D i a g n o s t i ccr i t e r ia ba sed on the c .v . responses revea led tha t the redoxp r o c e s s is n o t r e v e rs ib l e. Co m p o u n d 2 e x h i b it e d o n l y a nanod ic ox ida t ion p rocess (Ea = 1 .00 V) unassoc ia ted wi ththe ox ida t ion p rocess in the reverse scan . S imi la ri r r e v e r s i b l e b e h a v i o u r w a s o b s e r v e d f o r c o mp o u n d 1 ,

~ p R R N O D I CI ~ T E N T I L ( n I = I I F / [ I( l J I I I I t h ' T t R ) = l . d l ~ E - - 6

+ 1 .5 0 0 ~ - t 7 1 T ' ~. . . d . G rS ' - " ' ~ * O . 0 0 0

E(VOLT}F i g u r e 3 C y c li c v o l t a m m o g r a m o f c o m p o u n d 1 r e c or d e d a t a p la t i n u me l e c tr o d e f o r a D M S O s o l u t i o n . S c a n r a t e 2 0 0 m V s - 1

Table 4 R e d o x p o t e n t i a l s o f l o w - m o l e c u l a r - w e i g h t a n d p o l y m e r i cc o m p o u n d s ( P t e l e c t ro d e v s . S C E )

V o l t a g e ( m V )S w e e p r a t eC o m p o u n d S o l v en t E . E c ( m V s - 1)

1 D M S O 1 0 70 - 2 0 0C H a C N - - 1 4 0 0 2 0 0C o p o l y m e r w i t h 1 D M S O 1 2 14 - 2 0 01238 - 1002 D M S O 1 0 0 4 - 2 0 02 / C u 2 + D M S O 5 5 0 - 2 0 0= C o m p l e x s p e c ie s a r e p re s e n t i n D M S O w i th 2 = = x = 6 8 0 n m( 14 . 7 x 103 c m - 1 )

w h i c h s h o w e d a s in g le o x i d a t i o n ( E a = 1 . 07 V ) p e a k(Table 4). C o m p o u n d 1 a l s o s h o w e d a w e a k c a t h o d i cresponse in ace ton i t r il e .Polymers

Exch ange reactions o f N-alkylbenzotr iazole in homo-and copolymers with compounds ! and 2. The ab i l i tyo f po ly (N -a lky lbenzo t r i azo le) to en te r in to exchanger e a c t i o n w i t h t h e m o n o a m i d a t e d c o m p o u n d w a si n v e s ti g a te d b y t r e a t i n g D M S O s o l u t io n s o f a s y n t h e si z e dp o l y me r s a mp l e w i t h a mi n o c o mp o u n d s 1 a n d 2 a tA BT / a mi n e mo l a r r a t i o saccord ing to :[-CH2-~H-Ix + I or 2 [-CU2-~n-]x

C=O C=OI Is( ,C= OL . . J 'CH2)4

ranging from 1:1 to 2:1 ,

R = p i p e r a z t n eo r 1 , 3 - d ia m l n o -p r o p a n e

T h e e x t e n t o f t h e e x c h a n g e r e a c t i o n w a s c h e c k e d b yn i t rogen ana lys i s and FTi .r . spec t roscopy . In the l a t t e rc a se , t h e d i s a p p e a r a n c e o f th e b a n d s a t 1 7 3 0 c m - 1( a t t r ib u t e d t o th e b e n z o t r ia z o l i d e C= O ) a n d 7 7 0 c m -(a t t r ibu ted to subs t i tu t ed benzo t r i azo le) was main lycons idered 8 . W i th a mo lar ra t io c lose to 1 , the rea c t iono f p o l y ( N - a l k y lb e n z o t r i a z o le ) a n d c o m p o u n d 2 d i d n o ts e e m t o b e q u a n t i ta t i ve . T h e n i t ro g e n c o n t e n t w a s f o u n dto be h igher than the ca lcu la ted va lue (Table 5).E x a m i n a t i o n o f t h e FTi .r . spec t ra a l so revea led a l imi tede x c h a n g e r e a c t io n . C o m p a r i s o n w i t h t h e i n fr a - re d s p e c t r ao f a n a u t h e n t i c s a mp l e o f t h e s a me p o l y m e r o b t a i n e d b ya d i rec t rou te , i . e . by po ly me r iza t ion o f 1 -acry loy l -4 -l ipoy lp iperaz ine (Table 2), showed smal l d i f fe rences duet o b a n d s i n t h e re g i o n me n t i o n e d a b o v e . H o w e v e r , a v e r ys t r o n g a n d b r o a d b a n d a p p e a r e d a t 1 64 0 e rn - x i n t h es p e c t r u m o f b o t h s a mp le s . T h i s ma y c l e a rl y b e a t t r i b u t e dt o t h e a mi d e I b a n d a n d s u g g e st s t h a t t h e b e n z o t r i a z o leres idue i s subs t i tu t ed wi th the s imple co - reac tan t 2 . Thes t r o n g b a n d a t 1 01 5 c m - 1 d u e t o t h e p i p e r a z in e r i ng w a sfu r ther ev idence o f subs t i tu t ion . The n i t roge n co n ten ta g r e e d w e ll w h e n t h e m o l a r r a t i o o f si mp l e c o m p o u n d 1wi th respec t to ABT res idues was increased to 1 .5 :1(Table 5). In a l l cases , however , t he po lymers ob ta inedwere inso lub le in o rgan ic so lven t s . To ob ta in a mores o l u b le p o l y me r , w e i n t r o d u c e d t h e N - v i n y l p y r r o l id i n o n eun i t in to a copo lymer wi th acry loy lbenzo t r i azo le :

[-CHz-CH-hx +CHz-~H-lxC=O C=OI J

Ta b l e 5 E x c h a n g e re a c t i o n s o f N - a c r y l o y l b e n z o t r i a z o l e i n p o l y ( A B T )w i th m o n o a m i d a t e d c o m p o u n d s 1 a n d 2N c o n t e n t (% )

S t a rt i n g A m i n o A m i n o / A B T C a l c d f o r 1 0 0 %p o l y m e r c o m p o u n d m o l a r r a ti o e x c h a n g e F o u n dpo l y ( A B T ) 2 1 :1 8 . 53 10 . 971 1.5:1 8.15 a 7.90

C a l cu l at e d f or C a 4 H 2 4 N 2 0 2 S f l . 5 H 2 0

3 6 4 P O L Y M E R , 1 9 9 4 , V o l u m e 3 5 , N u m b e r 2


6/7

R e d o x - a c t i v e p o l ym e r s : M . C a s o la r o a n d E . B u s iI !

n _

Figure 4reaction with the compound 1

I I I I I I I I~ ~ Z 0 0 0 1 7 1 1 0 1 5 0 0 ~ t 0 0 0

cm-1FTi.r . spectra of the copolymer(ABT-co-VPy)before (a) and after (b) the exchange

T h e A B T r e s i d u e w a s e x c h a n g e d w i th c o m p o u n d 1 i n a2 :1 m o l a r r a t io . U n d e r t h e s e c o n d i t i o n s , t h e r e a c t i o n w a ss u b s t a n t i a l l y q u a n t i t a t i v e . T h i s w a s c o n f i r m e d b y i . r .s p e c t r a ( F i g u r e 4 ) , w h i c h s h o w e d t h e c o m p l e t e a b s e n c eo f s u b s t i t u t e d b e n z o t r i a z o l e . F u r t h e r m o r e , t h e a m i d e Ib a n d w a s v e r y s tr o n g a t 1 6 45 c m - 1 a n d t h e r e w e r e t w oc l o se s tr o n g b a n d s a t 1 5 5 5 a n d 1 5 4 0 c m - 1 . T h e l a s t t w oa r e a m i d e I I b a n d s a n d c a n p r o b a b l y b e a t t r i b u t e d t ot h e t w o a m i d o g r o u p s i n t h e l a te r a l c h a i n o f t h e v i n y lc o p o l y m e r . T h e c o p o l y m e r , e v e n c a r r y i n g s u b s t i t u t e dd i s u l f i d e r i n g , w a s s o l u b l e i n D M S O o w i n g t o t h ev i n y l p y r r o l i d i n o n e u n i ts , a n d t h e c y c li c v o l t a m m e t r i cr e s p o n s e s a t a p l a t i n u m e l e c t r o d e w e r e r e c o r d e d i n t h i ss o l v e n t . O n c e m o r e t h e c h a r a c t e r i s t i c s i n g l e o x i d a t i o np r o c e s s , w i t h o u t a d i r e c t l y a s s o c i a t e d r e s p o n s e i n t h er e v e r s e s c a n , w a s o b s e r v e d i n t h e c o p o l y m e r c a r r y i n g t h ed i s u lf i d e r in g . T h e c y c li c v o l t a m m o g r a m s t h u s c o n s i s t o fa s i n g l e r e d o x p e a k h a v i n g a n a n o d e p o t e n t i a l t h a ts l o w l y c h a n g e s w i t h s c a n r a t e s ( T a b le 4 ) . T h e c y c l i cv o l t a m m o g r a m i s e s s e n ti a ll y i d e n ti c a l t o t h a t o f t h ec o r r es p o n d i n g s im p le m o n o a m i d a t e d c o m p o u n d s e x c ep tt h a t t h e o x i d a t i o n p o t e n t i a l i s s h i f t e d t o h i g h e r v a l u e s ,i n c r e a s in g w i t h d e c r e a s i n g s c a n r a t e . T h e h i g h e r o x i d a t i o np o t e n t ia l o f th e a n o d e p e a k o f t h e c o p o l y m e r is p r o b a b l yd u e t o e l e c t r o n i c a n d s t e ri c ef f ec ts o f t h e m a c r o m o l e c u l a rc h a in , a b s e n t in s i m p le c o m p o u n d 1. T h e a m i n o g r o u pi n 1 h a s m o r e e l e c t r o n - w i t h d r a w i n g p r o p e r t i e s t h a n t h ea m i d o g r o u p i n th e c o p o l y m e r . T h is p o i n t n e e d s m o r ed e t a i le d s t u d y t o c l a r if y t h e m e c h a n i s m o f th e r e d o xp r o c e s se s .C O N C L U S I O N ST h e s y n t he s is o f m o n o a m i d a t e d c o m p o u n d s u s i n gc a r b o n y l d i i m i d a z o l e i s a c o n v e n i e n t w a y t o f o r ml i p o a m i d e - a m i n e s t h a t a r e u s e f u l f o r b i n d i n g t o v a r i o u sp o l y m e r i c m a t r i c e s 4 .

T h e e x c h a n g e r e a c t i o n w i t h t h e b e n z o t r i a z o l e r e s i d u ei n v i n y l p o l y m e r s a l l o w s e a s y i n t r o d u c t i o n o f t h e c y c li cd i s u l f i d e . T h e l a t t e r c a n b e r e d u c e d t o a d i h y d r o - t y p ep o l y m e r h a v i n g a p o w e r f u l r e d u c i n g c h a r a c te r . T h er e a c t i o n c a n b e p e r f o r m e d b e t t e r i f t h e o r i g i n a l p o l y m e ri s i n a so l u b l e f o r m , a s in t h e c a se o f c o p o l y m e r s w i t hN - v i n y l p y r r o l i d i n o n e u n i t s .E l e c tr o c h e m i c a l d a t a o n s y n t h e t i c c o m p o u n d s c a r r y in gt h e c y c li c d i s u lf i d e o n l y s h o w e d a n a n o d e r e s p o n s e i nc y c li c v o l t a m m e t r y , a n d w e r e a l so i r r e v e rs i b le . T h e a n o d ep e a k p o t e n t i a l i n c r e a s e d o n g o i n g f r o m t h e s i m p l el o w - m o l e c u l a r - w e i g h t c o m p o u n d s t o t h e c o p o l y m e r ,w h i l e th e p r e s e n c e o f co p p e r ( I 0 io n s l e d t o a s h a r p d r o pi n t h e v o l t a g e a s t h e s i m p l e c o m p o u n d s f o r m e d c o m p l e xsp e c i e s i n d i m e t h y l su l f o x i d e ( T a b l e 4 ) . T h e c l a r i f i c a t i o no f th i s p e c u l i a r b e h a v i o u r c a l ls f o r f u r t h e r s t u d y .

A C K N O W L E D G E M E N T ST h i s w o r k w a s s u p p o r t e d b y a g r a n t t o t h e I n t e r n a t io n a lJ o i n t R e s e a r ch P r o j e c t fr o m N E D O , J a p a n . O n e o f u s( M . C . ) w i sh e s t o t h a n k P r o f e s so r P . F e r r u t i ( B r e sc i aU n i v e r s i t y ) f o r h i s v a l u a b l e su g g e s t i o n s f o r t h e sy n t h e s i s .T h a n k s a r e d u e t o P r o f e s s o r A . C i n q u a n t i n i ( S i e n aU n i v e r s i t y ) f o r r e c o r d i n g t h e v o l t a m m o g r a m s .R E F E R E N C E S

1 Ise, N. and Tabushi, I. 'An Introduction to SpecialityPolymers',Cambridge University Press, Cambridge, 19832 Caso la ro ,M. an d Ito, Y. 'The Develop men t of Science forthe Improvement of Hu ma n Life' , 1st Kyoto-Siena Symp.(Eds. F. Cas prini and R. Barbucci), 19923 N a m b u ,Y., Acar, M. H., Su zuki, T. and Endo , T. Makromol.Chem. 1988, 189, 4954 G o r e c k i ,M. and Patchornik, A. Biochim. Biophys. Acta 1973,303, 365 N a m b u ,Y., Kijima, M. an d Endo , T. Macromolecules 1987, 20,962

P O L Y M E R , 1 9 94 , V o l u m e 3 5 , N u m b e r 2 3 6 5


7/7

Redox-act ive po lymers: M. Caso laro and E. Bus i6 Suzuki , T., Nam bu, Y. and Endo , T. Mac romole c ule s 1990, 23,15797 Ferrut i , P., Fer6, A. an d Cott ica, G. J . Po lym. Sc i. , Polym. Chem.Edn. 1974, 12, 5538 Ferrut i , P., Vaccaroni , F. and Tanzi , M. C. J . Polym. Sc i . , Polym.Chem. Edn. 1978, 16, 14359 Ferrut i , P., Tanz i , M. C., Ruscon i , L. and Cecchi, R. M a k r o m o l .Chem. 1981, 182, 2183l0 Barbucci, R., Casolaro, M., Noc entini , M., Reginato, G. and

Fer ru t i , P . Mak romol . Che m. 1986, 187, 195311 Barbucci, R., Casolaro , M., Dan zo, N., Barone, V., Ferrut i , P.and Ange lon i , A . Mac romole c ule s 1983, 16, 45612 Ga ns, P., Sabatini , A. and Vacca, A. J . Chem. Soc . , Dalton Trans.

1985, 119513 Zanello, P., Cin quan tini , A., Ghilard i , C. A., Mido ll ini , S.,Mo neti , S., Orland ini , A. and Bencini, A. J . Chem. Soc . , DaltonTrans. 1990, 376114 Smith, R. M. an d Martel l , A. E. 'Cri t ical Stabil i ty Con stants ' ,Ple num Press, New York, 197515 Lawson, W. B., Leafer, Jr, M. D., Tewes, A. an d Rao, G. J. S.Hoppe-Seyler 's Z. Physiol . Chem. 1968, 349, 25116 Caso la ro , M. Unpu bl i shed da ta17 Barbucci , R., Casolaro, M., Ferrut i , P., Tanz i , M. C., Grassi , L.and Barozzi , C, Mak romol . Che m. 1984, 185, 152518 Barbucci , R., Casolaro, M. and Ma gnan i , A. Coord. Chem. Rev.1992, 120, 29

3 6 6 POLYMER, 1994, Vo lume 35, Number 2

redoxactive polymers synthesis

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