A Study of Syn thesis, Imm ob il iza tion and Ca ta lytic Capab il ity of M eta lloporphyr in 3

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1 V o l. 14 N o Chem ical R esearch in Ch inese U niversities A Study of Syn thesis, Imm ob il iza tion and Ca ta lytic Capab il ity of M eta lloporphyr in 3 W AN G X ing2qiao 3 3, GAO Shuang, CA Chang2sheng YU L ian2x iang, GUO J ing2fu, SHUN Shu2ju and CAO X i2zhang (D ep artm ent of Chem istry, J ilin U niversity, Chang chun, ) (R eceived M ay 20, 1997) A stepw ise2synthesis m ethod w as used to immobilize tetrach lo ro2tetram ethyl po rphyrins in the supercages of N acox mo lecular sieve. T he immobilized po rphyrin w as characterized by m eans of UV 2V is, IR, D TA, SEM and EPR. A comparision w as m ade fo r the activities among tetra2 ch lo ro2tetram ethyl po rphyrins, its cobalt (g ) comp lex, N acox mo lecular sieve and the immobi2 lized po rphyrin as catalysts in the oxidation reaction of styrene and p 2creso l. T he stability and catalytic capability of the m etallopo rphyrin is increased after the com bination of po rphyrin w ith m o lecular sieve. In addition, th is new type of catalyst tetrach lo ro2tetram ethyl po rphyrin imm obi2 lized in the supercages of N acox mo lecular sieve no t only po ssesses the advantages of bo th po r2 phyrin and m o lecular sieve, but also m akes up fo r their respective deficiencieṡ T he experim ental results confirm ed that bo th the stability and catalytic capability of m etallopo rphyrin imm obilized in the supercages of m o lecular sieve are increased. Ke yw o rds M etallopo rphyrin, Synthesis, Immobilization, Catalytic capability In troduction T he m etallopo rphyrin is a con jugated m acrocyclic compound w h ich has special capab ili2 ties in som e respects, such as an activation of sm all ino rgan ic mo lecu les, pho tochem istry, electrochem istry, gas sen sitivity and chem ical catalysis. In particu lar, its catalytic capab ility in ox idation2reduction reaction s has attracted ex ten sive atten tion [1-8 ]. How ever, m etallopo r2 p hyrin s have no t been w idely app lied due to their poo r stab ility and low yield of p reparation. Fo r u tilizing the m etallopo r2 phyrin s, chem ists have m ade m any effo rts to imp rove the stab ility of po rphyrin s, Co llm an [9 et al. ] u sed the m ethod of periphery deco ra2 tion to syn thesize a po rphyrin of " tailed p icket fence" w ith a rm ing a t increa sing the stab ility of m etallopo rphyrin. In the early 1990 s, [10 N akam u ra et al. ] repo rted that they immob i2 lized successfu lly po rp hyrin in a m o lecu la r sieve (N ay). W e u sed a m ethod differen t from that u sed in literatu re [11 ], stepw ise2syn thesis F ig. 1 Schem atic draw ing of the structure of the m ononuclear po rphyrin. 3 Suppo rted by a grant from N ational N atural Science Foundation of Ch ina. 3 3 To w hom co rrespondence should be addressed.

2 112 Chem ical R esearch in Ch inese U niversities V o l. 14 of so lid2liqu id phases [12 ] to syn thesize a series of new type of po rphyrin compounds including 3, 7, 13, 17 2tetrach lo ro 2 2, 8, 12, 18 2tetram ethyl po rphyrin (TCTM P ) [13 ] and m etal2po r2 phyrin [CoTCTM P, M ntctm P, FeTCTM P ] ( see F ig. 1). A t the sam e tim e po rphyrin (TCTM P) w as immob ilized in a supercage of Co 2+ 2exchanged N ax (TCTM P2N acox). Fu r2 thermo re, w e studied the catalytic p roperties of the catalysts. T he resu lt indicates that the stab ility of po rphyrin w as imp roved indeed w hen it w as im 2 mob ilized in the supercages of mo lecu lar sieve. Exper im en tal 1 Syn thesis of Com pounds TCTM P w as syn thesized by the m ethod described in p reviou s paper [13 ]. M etallopo r2 phyrin w as syn thesized by the m ethod of reference [14 ]. P reparation of N acox mo lecu lar sieve and syn thesis of TCTM P2N acox w ere described som ew here [12 ]. 2 Ca ta lytic Reaction s Tw o reaction s w ere cho sen to exam ine the catalytic capab ilities of the syn thesized cata2 lyst ṡ Fo r the ox ida t ion of styrene by hyd rogen p erox ide, 10 ml of acetone con ta in ing styrene (9. 6 mmo l), 30% aqueou s so lu tion of hydrogen perox ide (7. 8 mmo l) and a sm all amoun t of the syn thesized catalyst w ere put in a reaction bo ttle w ith a circu lating w ater jack2 eṫ T he reaction system w as linked w ith a gas m easu ring tube and kep t at 333 K by con stan t2 temperatu re w ater. T he reaction m ix tu re w as stirred un til the p roduct quan tity reached its m ax im um by mon ito ring w ith gas ch rom atography. Fo r the ox idation of p 2creso l by dioxygen, p 2creso l (415 mmo l), N aoh (50 mmo l), m ethano l (10 ml ), co2catalyst copper (5 m g) and a sm all amoun t of the syn thesized catalyst w ere put in the above doub le2layered bo ttle. T he reaction m ix tu re w as stirred fo r 7 h, then the reaction w as stopped. 3 Ana lytica l Techn iques N a + con ten t in the tw ice exchanged so lu tion w as determ ined by atom ic ab so rp tion spec2 tro scopy. Scann ing electron m icro scopy (H ITA CH I X2650 Japan) w as u sed to check w hether po rphyrin depo sited on the ex ternal su rface of the mo lecu lar sieve crystals w as removed com 2 p letely. Infrared spectra of N acox, TCTM P2N acox and TCTM P w ere reco rded on a FT IR 2 5PC Infrared Spectropho tom eter (U. S. A. N ico let Co. ) and their UV 2V is spectra w ere tak2 en on UV 2visib le R eco rding Spectropho tom eter UV 2240 (Sh im adzu). T he differen tial ther2 m al analysis fo r the above samp les w as carried ou t u sing differen tial therm al analytical appa2 ratu s (Japan Science) under the condition of D TA 250 mv, N 2 50 cm 3 gm in at a temperatu re2 raising rate of 10 gm in. EPR spectra of N acox, TCTM P, CoTCTM P and TCTM P2N a2 CoX w ere m easu red on ER 2000 EPR (Germ any) under the experim en tal condition of cen tral m agnetic field in ten sity m T. Gas ch rom atograph ic analysis w as perfo rm ed u sing the model SC21001 gas ch ro2 m atograph ic apparatu s w ith A 4500 computeṙ T he apparatu s w as equ ipped w ith 2 m long stain less steel co lum n packed w ith 80g100 m esh w h ite SiO 2 and m ethyl2silicone E 301. Results and D iscuss ion 1 Co 2+ -exchange D egree T he to tal exchange degree of Co 2+ w as found to be 31. 2% by atom ic ab so rp tion

3 N o. 2 WAN G X ing2qiao, GAO Shuang, CA Chang2sheng et al. 113 specero scopy. 2 Scann ing Electron M icroscopy T he experim en tal resu lts of the scann ing electron m icro scopy (F ig. 2) show clearly that the depo sition of m aterial on the ex ternal su rface of N acox mo lecu lar sieve cou ld be removed effectively by the ex traction p rocedu reṡ F ig. 2 Schem es of scanning electron m icro scopy. (A ) N acox after reaction w ith TCTM P; (B) after the extraction p rocedures. F ig. 3 EPR spectra of N acox, TCTM P, and TCTM P2N acox. 3 Electron Paramagnetic Resonance (EPR) EPR spectra of N acox, TCTM P, CoTCTM P and TCTM P2N acox w ere show n in F ig. 3, from w h ich Cobalt signal can be seen w ith an excep tion of TCTM P. EPR spectrum of free po rphyrin w as differen t from that of cobalt po rphyrin. How ever, the signal from TCTM P2 N acox w as sim ilar to that from cobalt po rphyrin. T h is resu lt confirm s fu rther that po r2 phyrin in supercage of N acox com b ined w ith Co 2+ ion to fo rm Co (g ) po rphyrin comp lex. 4 UV-v is Spectra T he data of UV 2V is spectra of TCTM P and so lids reflection of TCTM P2N acox w ere show n in T ab le 1. It can be seen from T ab le 1 that the So ret band of TCTM P2N acox had a b lue2sh ift, w h ile it s Q band had a red2sh ift and a decrea se in Q band num ber rela t ive to TCTM P, indicating that po rphyrin mo lecu les imm ob ilized in the sup ercages of N acox T able 1 UV 2V is spectra param eters of po rphyrins Samp le So ret Κgnm Q Κgnm TCTM P So lid reflection (TCTM P2N acox) mo lecu lar sieve com b ined w ith Co 2+ ion fo rm ing Co (g ) po rphyrin comp lex. T he amoun t of po rphyrin immob ilized in N acox mo lecu lar sieve w as figu red ou t to be mo l TCTM P g N acox u sing Beer s law. A cco rding to the degree of Co 2+ exchange (31. 2% ), the ratio of Co 2+ (comp lex) to Co 2+ (excess) w as figu red ou t to be 10. 2%. 5 Infrared Spectra T he infrared spectra param eters of N acox, TCTM P2N acox and TCTM P w re listed in T ab le 2. F rom T ab le 2, it can be seen that the vib ration s cam e from bo th TCTM P2N acox and po rpbyrin N - H vib ration of po rphyrin mo lecu les immob ilized in the supercage of N a2 CoX mo lecu lar sieve disappeared. A t the sam e tim e, the sh ifts of the peak s of pyrro le ring and po rphyrin ring appeared. T hese phenom ena m ay be attribu tab le to the fo rm ation of com 2 p lex of Co 2+ ion in the supercage of the mo lecu lar sieve w ith N atom s in po rphyrin mo lecu les.

4 114 Chem ical R esearch in Ch inese U niversities V o l. 14 T able 2 IR spectra param eters of po rphyrin, N acox and TCTM P2N acox (KB r) Po rphyrin Compd. N H CH TCTM P Pyrro le ring R ing W ave num bergcm - 1 M o lecular sieve T O W inding B icyclic Inter tetrahedral symm etry expand2 contract TCTM P2N acox Inter tetrahedral resymm etry expand2 contract N acox D ifferen tia l Therma l Ana lysis (D TA) T he experim en tal resu lt of differen tial therm al analysis indicates that the decompo sition temperatu re of po rphyrin immob ilized in the supercages of the mo lecu lar sieve raised abou t 70 K compared w ith that of free po rphyrin. 7 Ca ta lytic Activ ity and Selectiv ity of the Ca ta lysts T he h ighest conversion ratio of styrene and the catalytic efficiency of the differen t cata2 lysts are listed in T ab le 3. T he data in T ab le 3 show that the catalytic activities of the differ2 en t m etal2tctm P are in the fo llow ing o rder: Co (g ) TCTM P > Fe (g ) TCTM P > M n (g ) TCTM P. T herefo re, on ly Co (g ) TCTM P w ith the h ighest activity w as immob ilized in the supercages of the mo lecu lar sieve. It can be seen also from T ab le 3 that free po rphyrin and the mo lecu lar sieve have a sim ilar and w eak catalytic capab ility. T he in teraction betw een Co (g ) ion s in the supercages of N acox mo lecu lar sieve and the reactan t en tering in to the su2 percages of N acox mo lecu lar sieve is on ly a electro static in teraction in a region of availab le electric field. Ow ing to the w eak ab ility to activate C C bond in styrene, Co (g ) ion s in mo lecu lar sieve show ed a low catalytic activity. How ever, after po rphyrin fo rm s a m etal comp lex w ith Co ( g ) ion s, the T able 3 Catalytic activity and selectivity to phenylaldehyde p roperty of po rphyrin w as changed fo r the catalysts in the oxidation reaction of obviou sly. CoTCTM P can fo rm an in2 styrene term ediate comp lex w ith styrene at ax i2 al po sition. T he action of Co (g ) ion s resu lts in a decrease in bond energy of C C in styrene and facilita tes C C bond to b reak. T herefo re, the catalytic capab ility of CoTCTM P is m uch h igher than tha t of free po r2 phyrin. T he catalytic activity of Co ( g ) TCTM P imm ob ilized in the sup ercages of mo lecu lar sieve increased greatly. T he po ssib le rea son is tha t the reac2 Amount of Conversion Catalytic catalyst ratio (% ) of efficiency a gm g styrene Fe (g ) TCTM P (87) c M n (g ) TCTM P (100) Co (g ) TCTM P (53) TCTM P (98) N acox (98) TCTM P2N acox (98) b a. M o les of styrene consum edgm o les of catalyst w ith an excep tion TCTM P2N acox; b. M o les of styrene consum edgm o les of po rphyrin in N acox; c. The num bers in brackets are the percentage of phenylaldehyde content in the p roducts.

5 N o. 2 WAN G X ing2qiao, GAO Shuang, CA Chang2sheng et al. 115 tan ts en tered in the supercages w ere influenced by bo th facto rs of the electro static fields of mo lecu lar sieve and ax ial effect of po rphyrin, w h ich resu lted in a strik ing activation of styrene. In summ a ry, the ca ta lyt ic cap ab ility of the severa l ca ta lyst s a re in the o rder: TCTM P2N acox> Co (g ) TCTM P> Fe (g ) TCTM P> M n (g ) TCTM P N acox> TCTM P 8 The L ife of the Syn thesized Ca ta lysts Fo r investigating the stab ility of CoTCTM P, w e did som e experim en ts to check the life of TCTM P2N acox and Co (g ) TCTM P. T he data in T ab le 4 show the h ighest conversion ratio of the above tw o catalysts in the several repeated experim en tṡ A fter having been u sed fo r fou r tim es, Co (g ) TCTM P activity decreased obviou sly. How ever, the h igh activity of TCTM P2N acox still rem ained. T he resu lts indicate that the stab ility of m etallopo rphyrin w as increased after it w as immob ilized in the supercages of the mo lecu lar sieve. T able 4 T he life of TCTM P2N acox and CoTCTM P Amount of catalyst gm g Conversion ratio (% ) of styrene N o. of the experim ents TCTM P2N acox CoTCTM P T he reaction fo r each experim ent w as run fo r 24 h. 9 Ca ta lytic Activ ity of CoTCTM P and TCTM P-NaCoX in the Ox ida tion of p - Cresol Fo r ano ther reaction model, p 2creso l ox idation to p 2H PA (p 2hydroxyl phenylaldeyde) by dioxygen, TCTM P2N acox show ed a h igher activity compared to CoTCTM P ( see T ab le 5). T able 5 Catalytic activity of the catalysts in the oxidation reaction of P2creso l Amount of catalyst Conversion ratio (% ) a Catalytic efficiency b CoTCTM P TCTM P2N acox a. T he conversion ratio of p 2creso l; b. see T able 3. Re fe re nce s [ 1 ] Jam es, E. L., Paul, E. E. J ṙ, H arry, K. M. J ṙ et al., Journal of Catalysis, 141, 311 (1993) [ 2 ] Jam es, E. L. and Paul, E. E. J ṙ, Catalysis L etters, 8, 45 (1991) [ 3 ] T eddy, G. T. and A ndrew, R. M., J. Am. Chem. Soc., 111, (1989) [ 4 ] W ang, X. Y., W ang, R., L i, G. Q. et al., A cta Ch im ica Sinica, 45, 780 (1987) [ 5 ] X i, Z. W., L iu, W. Z., Cao, G. Y. et al., A cta Catalysis (Ch ina), 7 (4), 357 (1986) [ 6 ] T such iya, S. and Seno, M., Chem. L etṫ p. 263 (1989) [ 7 ] Co llm an, J. P., B raum an, J. İ, Doxsee, K. M. et al., J. Am er. Chem. Soc., 102, (1980) [ 8 ] R ao, L. F., Guo, X. X., A tsush i, F. et al., A cta catalysis (ch ina), 10 (2), 143 (1989) [ 9 ] D e M allm ann, A. and Barthom euf, D., Catal. L etṫ, 5 (3), 293 (1990) [10 ] N akam ura, M., T atsum i, T., Tom inaga, H., Bull Chem. Soc. Jpn., 61 (11), (1990) [11 ] M eyer, G., W oh rle, D., M oh l, M. et al., Zeo lites, 4, 30 (1984) [12 ] W ang, X. Q., Gao, S., L iu, Y. W. et al., Chem. J. Ch inese U niv. 15 (6), 789 (1994) [13 ] W ang, Y. Q., W ang, X. Q., L iang, Y. X. et al., A cta Scientarum N aturalium U niversitis J ilinensis, Supp l., 106 (1992) [14 ] A dler, A. D., L ongo, R. R., F inarelli, J. D., J. O rganom etal. Chem. 32, 476 (1967)