C. R. Acad. Sci. Paris, t. 2, Skrie II c, p. 241-250,1999 Chimie des surfaces et catalyse/Surface chemistry and catalysis (Chimie inorganique mol&xdairelMo/ecu/ar inorganic chemistry)

Oxidation of 2,4,6=trichlorophenoI catalyzed by iron phthalocyanines covalently bound to silica Muriel SANCHEZ a, Anke HADASCH a, Alain RABION b, Bernard MEUNIER a*

a Laboratoire de chimie de coordination du CNRS, 205, route de Narbonne, 31077 Toulouse cedex 4, France ’ Centre de recherche Elf-Atochem, Lacq, BP 34,64170 Artix, France

E-mail: bmeunier@lcc-toulouse.fr

(Received 5 February 1999, accepted after revision 29 March 1999)

Abstract - The covalent attachment of an iron phthalocyanine with chlorosulfonyl substituents (FePcSOzCl) onto a functionalized 3-aminopropyl-silica has been achieved. This supported catalyst FePcSO&l-silica is able to degrade a recalcitrant pollutant like 2,4,6-trichlorophenol (TCP) with hydrogen peroxide as oxidant. In order to improve the catalytic efficiency of the grafted iron phthalocyanine complex, modifications of the macrocycle substituents, passivation of the silica surface, variation of the loading of the carrier and addition of an organic co- solvent to the reaction mixture were carried out. 0 Academic des sciences/Elsevier, Paris

supported iron phthalocyaoines / catalytic oxidation I 2,4,6-trichlorophenol I pollutant degradation

Version franqaise abregCe - Oxydation du 2,4,6-trichlorophCnoi catalyske par des phtalo- cyanines de fer greffhes sur silice par liaisons covalentes. La degradation des polluants, molecules peu biodegradables, tels que les composes aromatiques chlores [l] est une prioritt afin de preserver notre environ- nement. Dam cette categoric de composes, le 2,4,6-trichlorophenol (TCP), produit lors du blanchiment de la pate B papier [2], est souvent utilise comme modele de molecules peu dtgradees par les micro-organismes. Nous avons recemment decrit des systemes catalytiques capables de degrader le TCP en utilisant I'eau oxygenCe comme oxydant et des metallophtalocyanines comme catalyseurs biomimetiques [3-81. L’activation de la sulfo- natophtalocyanine de fer FePcS (&re I) avec l’eau oxygenee conduit B des especes actives de type Fe’“=0 et Fe”‘OOH impliquees dam la formation des produits d’ouverture du cycle aromatique ou de produits de couplage [6-81 ($gtire 2). L’activite catalytique des metallophtalocyanines est toutefois diminute par des phino- menes d’aggregation [9]. Deux strategies sont utilisees pour favoriser la forme monomerique : (a) addition d’un co-solvant organique [3, 71 ou d’un detergent [lo] et (b) fixation du catalyseur sur divers types de supports tels que des charbons [ll], polymeres [ 121, silices [13], zeolites [14] ou argiles [ 153. Ces dernieres methodes permet- tant d’obtenir des catalyseurs support&s presentent des avantages pour les procedes industriels : separation des produits aisle et possibilite de recyclage du catalyseur. Dans un precedent travail, nous avons decrit l’immo- bilisation par interactions Clectrostatiques de FePcS sur une r&sine cationique echangeuse d’ions (Amberlite IRA 9OO), mais la forte adsorption du substrat sous sa forme phenolate interferait avec sa degradation catalytique [16]. L’utilisation d’un support neutre non aromatique et la fixation de la metallophtalocyanine par liaisons covalentes devrait permettre d’hiter ce phenomene. Notre travail sur la preparation de metalloporphyrines ayant des fonctions sulfonamide a la periphtrie du macrocycle [ 17a,b] nous a amen& a envisager la fixation des metallophtalocyanines sulfonees par une telle fonction chimique (il faut noter que cette methode avait deja ete utilisee par Akopyants et al. pour la fixation d’une phtalocyanine de cobalt sur une silice mod&e [ 17~1). Nous avons done prepare une phtalocyanine de fer substituee par des groupements chlorosulfonyle (FePcSO&l), que nous avons ensuite immobilisee sur une silice commerciale fonctionnalisee par des groupements 3-aminopropyle (0,9 meq NH,/g) (figure 3) [IS]. A ucun phenomene d’adsorption du substrat sur le support mineral, ni de relar-

Communicated by Fran@s MATHEY.

- Correspondence and reprinrs.

1387-1609/99/000200241 0 Acadkmie des sdences/lYsevier, Paris 241

M. Sanchez et al.

gage de metallophtalocyanine n’ont ete observh avec ce catalyseur support& apres 1 h dans les conditions expe- rimentales utilisees ulterieurement pour la catalyse. De plus, il a ete v&i& que la silice seule ne catalysait pas l’oxydation du TCP par H,O,. La capacite oxydante du catalyseur supporte FePcSO$-silice a ensuite Ctt testee sur la degradation du TCP. D’apres les resultats present& dam le tableau Z, dans les memes conditions experimentales (catalyseur/TCl? = 2 % en mole, TCP 1 mM, H,O, 6 mM, tampon phosphate 50 mM et sans co-solvant organique), l’activite catalytique de FePcSOaC1-silk a 17,5 prno1.g’ (29 % de conversion en 1 h, exp. 3) est comparable a celle de FePcS en solution (32 %, exp. I) ou FePcS immobilise sur Amberlite (28 %, exp. 2). Toutefois, le catalyseur se d&active lentement. Les fonctions SO&l de la phtalocyanine ont alors kc? mod&es, aprb immobilisation sur silice, en SO,H, SO*NR, et SO,SiPh, ($gure 4’) afin de determiner l’influence des substituants de la phtalocyanine sur la duree de vie du catalyseur supporte et sur son activite cata- lytique. Les resultats obtenus (dans les memes conditions d’oxydation que precedemment) avec ces nouveaux catalyseurs support& montrent que FePcS03H-silice est le moins actif de la serie, alors que I’activid catalytique des phtalocyanines de fer substituees par des groupements sulfonamide, FePcS02NRz-silice, augmente avec l’encombrement sttrique de R par creation d’un effet cage autour du site actif [19] (tableau I, exp. 4-7 et figure r). Les meilleurs resultats ont CtC obtenus avec FePcSOgSiPhj--silice (55 % de conversion en 1 h, exp. 8) mais, comme pour les autres catalyseurs support&, une d&activation est observee aprts 1 h (figure 5) [ 191. Une passivation de la silice du catalyseur supporte le plus actif FePcSOjSiPhj--silice a alors ete entreprise en desac- tivant les fonctions NH, libres et OH de surface par acetylation et silylation respectivement (figure 6). Le rtsultat de ces modifications sur la degradation catalytique du TCP en phase aqueuse est une perte d’activite qui augmente avec le caractere hydrophobe de la silice (tableau 1, exp. 8-10). I1 a egalement et& montre dam la litte- rature que l’activite spkifique des metallophtalocyanines greffees dtpendait de la charge du support [20]. Afin d’ttudier ce paramttre, nous avons prepare plusieurs echantillons de FePcSO&l-silice possedant des charges comprises entre 7,5 et 300 umolg’. Le graphe de la$g we 7 (voir aussi tableau I, exp. 3, I I-15) indique que la meilleure activite est obtenue pour une silice chargee a 17,5 umolsg-‘. Pour des charges plus importantes, la baisse de l’activite catalytique pourrait Ctre expliquee par des phenomenes d’aggregation de la phtalocyanine et pour des charges plus faibles, les molecules de phtalocyanine sont probablement trop dispersees sur la silice pour Ctre facilement accessibles pour le substrat. Ces phenomtnes ont deja ett decrits dans la litterature [20]. Afin d’augmenter la degradation du TCP, nous avons ajoute un co-solvant organique dam le milieu reactionnel pour amtliorer sa solubilite. Dans ces conditions, I’activitt catalytique d’une des phtalocyanines de fer support&e, FePcSOzCl-silice charge a 42 umolg’ (12 % de conversion en 2 h, exp. I2), a pu &tre multipliee par un facteur 2 avec 20 % d’ethanol (28 %, exp. 16) et par un facteur 6 avec 20 % d’acetone (69 %, exp. 17etjpre 8). Ces derniers resultats sont particulitrement interessants car, mCme si la conversion totale du TCP n’a pas encore Pte atteinte, ils mettent en evidence la vahdite du concept d’immobilisation par liaisons covalentes d’une mttal- lophtalocyanine qui pourrait &tre utilise dans un processus industriel de decontamination d’effluents aqueux. Des etudes sont actuellement en tours pour optimiser la reaction avec d’autres types de supports ainsi que pour la degradation d’autres polluants. 0 Academic des sciences/Elsevier, Paris

phtalocyanines de fer supportkes 1 oxydation catalytique / 2,4,6-trichloroph&ol I degradation de polluants

1. Results and discussion

I. I. Introduction

The degradation of recalcitrant pollutants remains a high priority in order to preserve our environment. For example, chlorinated aro- matic compounds are extremely persistent in the environment because of their slow biodeg- radation by microorganisms [l]. One of the most notable toxic offenders is 2,4,6-trichlo- rophenol (TCP) which is produced by paper mills [2] and also used as a biocide. Thus, TCP

is an obvious benchmark for research on the decontamination of waste-waters.

We have recently reported efficient systems for the catalytic degradation of TCP using hydrogen peroxide as oxidant and metalloph- thalocyanines as bioinspired catalysts [3-81. The iron tetrasulfophthalocyanine complex FePcS (fiszlre I) is water-soluble and exhibits a high catalytic activity. The activation of FePcS with H,O, generates a high valent iron-oxo FeIV=O and an iron-hydroperoxo Fe”‘OOH as active species which are able to oxidize TCP to chloromaleic acid and to CO, as ultimate oxi-

242

Figure 1. Structure of the iron(III)-tetrasulfophtha~ocya- nine (FePcS); only one of the four possible regioisomers is

depicted here.

dation product [6-81. Oxidative coupling products are also observed (jg~e2).

The efficiency of this category of soluble cat- alysts is considerably decreased by the well- known aggregation of phthalocyanine com- plexes [9]. To ensure that only monomeric met- allophthalocyanines are present in the reaction mixture, two strategies have been developed: (i) the addition of an organic co-solvent [3, 71 or detergent [lo] and (ii) the immobilization of

Iron phthalocyanines covalently bound to silica

the catalyst on a variety of supports like char- coal [ll], polymers [12], silica [13], zeolites [ 141 or clays [ 151. This latter strategy for the preparation of supported oxidation catalysts is advantageous in industrial processes by facili- tating both catalyst separation and recycling, and also by reducing effluent contamination.

In a previous work, we described the adsorp- tion of FePcS onto a cationic ion-exchange resin (Amberlite IRA 900) via strong electro- static interactions [ 161. Unfortunately, the adsorption of the phenolate form of the sub- strate on the cationic polymer competes with its oxidative degradation. This phenomenon can be avoided by using a neutral and a non- aromatic carrier, on which the metallophthalo- cyanine catalyst can be fixed by covalent bonds. Our work on the preparation of metallopor- phyrin derivatives with sulfonamide functions at the periphery of the macrocycle [ 17a,b] sug- gested us to link sulfonated iron-phthalocy- anines via a sulfonamide bond to a silica support modified with amino functions (it should be noted that this method has been used by Akopyants et al. to attach a cobalt phthalo- cyanine onto silica [ 17~1).

So, we prepared an iron(II1) phthalocyanine substitued by chlorosulfonyl groups

OH

t;l TCP

T Aromatic ring cleavage

! H

‘c=c’c’ HO& \COOH +

(24%)

H ,C=C,H

HO06 ‘COOH +

(1%)

\ OH

H COOH ‘c=c’

HO06 ‘Cl (346)

H. ,COOH ,c=c,

HOOC H (1%)

Figure 2. Product disrriburion of the H,O, oxidation of TCP catalyzed by FePcS.

243

M. Sanchez et al.

(FePcSO,Cl) by refluxing FePcS in thionyl chloride (84 % yield, j$re 3). The commer- cially available 3aminopropyl silica gel (0.9 meq NH,/g) was used as support [ 181. The subsequent immobilization of the complex through a sulfonamide linkage was achieved by refluxing the chlorosulfonated metallophthalo- cyanine and the amino-linked silica support in pyridine (jgure 3). The green color of the material obtained after various washing strongly suggested the fixation of the iron phthalocyanine complex as monomer. The loading of the support (17.5 umol of FePcSO,Cl/g) was determined directly by an iron elemental analysis and indirectly by the determination of the amount of FePcSO,Cl remaining in solution by W-vis spectroscopy. No leaching of the complex was observed dur- ing intensive washings with water, DMF or diethylether or after I h under the experimental conditions used for the catalytic oxidations. We also checked that TCP did not merely phy- sisorbed on the surface of the modified silica and the mineral carrier without FePcSO,Cl did not catalyze the oxidation of TCP with H,O,. The catalytic behavior of the supported metal- lophthalocyanine FePcSOJl-silica for the

degradation of TCP with hydrogen peroxide as “green” oxidant (water is the only residue after the oxidation) was then studied. These results reported in table I were obtained under the same experimental conditions (catalyst/TCP = 2 mol %, TCP 1 mM, H,O, 6 mM, phosphate buffer 50 mM and without any organic co-sol- vent). The activity of FePcSO,Cl grafted onto silica (29 % conversion after 1 h, run 3) is com- parable to that of free FePcS in solution (32 %, run I) or FePcS immobilized onto Amberlite IRA 900 (28 %, ran 2). Nevertheless, a slow deactivation of the supported catalyst was observed, but this is not due to an over-con- sumption of H,O, by a catalase effect mediated by the metallophthalocyanine since a subse- quent addition of oxidant did not restore the ability of the catalytic system to oxidize TCI?

In order to study the influence of the substit- uents of the iron phthalocyanine on the lifetime of the supported catalyst and on its catalytic activity, the SO-J1 groups were transformed into SO,H, SO,NR, and SO,SiPh, after the immobilization of the metallophthalocyanine onto the silica. The supported catalyst FePcSO&l-silica was treated with sulfuric acid, dimethyl-di(iso-propyl)- or (iso-propyl)

so; soc12 ) ClO,S SO~CI 80°C; 12h

FePcS FePcS02C.I (84%)

OH 0 &i-NH2 + d

ClO*S SO,Cl

OH I SO&l

OH 0

SO&I

C&i-NHS02 d 4 Fe”’ SO&I

OH SO&I

FePcSO$3-silica 17.5 pmol /g (82%) Figure 3. Preparation of FePcSO,CI and immobilization on a functionalized silica.

244

Iron phthalocyanines covalently bound to silica

Table I. Oxidation of TCP at room temperature catalyzed by supported iron phthalocyanines.”

Runs Catalysts Loading Conversion of TCP (o/o)

(pmol.g-‘) 30 min 60 min 90 min 120 min

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16”

17’

FePcS

FePcS-Amb

Fel?cSO@silica

FePcS03H-silica

FePcSOzNMe2-silica

FePcSOzN(i-Pr&silica

FePcSOzN(i-Pr)(r-Bu)-silica

FePcSO,SiPh,-silica

FePcSO$iPh,-silica-NHCOCH3

FePcSO$iI%-silica-NHCOCH,/OSiMe,

FePcSOLC1-silica “

“

-

9.0

17.5

11.5

7.5

9.5

21.4

42.0

300

42.0

- 22

8

21

25

30

39

31

16

2

6

3

0

11

39

32

28

29

11

28

42

52

55

38

25

10

12

12

10

0

25

52

16

33

42

57

61

50

26

13

20

13

12

0

28

69

3 For the experimental conditions, see the general catalytic procedure for TCP degradation in the experimental section. Concentrations of the reactants: TCP 1 mM, catalyst/TCP = 2 o/o (in mol), phosphate buffer 50 mM, H,O, 6 mM.

” The reaction mixture contained 20 %I of ethanol (TCP was dissolved in a solution of phosphate buffer 50 mM/EtOH

80:20). ’ The reaction mixture contained 20 o/o of acetone (TCP was dissolved in a solution ofphosphate buffer 50 mM/ace-

tone 80:20).

(tert-butyl)-amines and triphenylsilanol On the other hand, the activity of the iron- (jgure 4). According to UV-vis data, no leach- phthalocyanines substituted by sulfonamide ing of the metallophthalocyanine was detected groups, FePcSOzNR2-silica, increased with the during these post-synthesis modifications. The bulkness of the substituents (jgtire5). When results obtained with these modified supported the nitrogen atom was substitued by two catalysts in the degradation of TCP (under the methyl groups, the conversion of TCP was same experimental conditions described above) 28 % after 1 h (rzln 5) and increased to 42 % indicated that FePcS03H-silica is the less and 52 % with the bulkier iso-propyl and tert- active catalyst with only 11 % conversion of butyl subtituents (runs G7), respectively. TCP after 1 h (t&&I, run 4). These data are a clear-cut illustration of the role

silica-HNO$ SO,Cl

so,cr

FeP&OzCI-silica

v 9 w siiii-HNO,S

I Y = SOsH; SO$WIQ; SOzN(i-FQ SOzN(i-Pr)(f-Bu); SO&Phs

i) ~$0~; Me$IH; (i-P&NH; (i-Pr)(t-EWJR &SiOH

Figure 4. Modification of the chlorosulfonyl substituents of FePcSOzCI-silica and preparation of FePcSOsH-silica, FePcS02NMe2-silica, FzPcSOzN(i-Prz)-silica, FePcS02N( -I’ )( -B )- I’ I r t u so tea and FePcS07SiPh,-silica.

245

M. Sanchez et al.

o(..-.-.-.-.-,......-....I 0 2 I 6 I 10 12 I4 16 16 20 22 24

Time (hours)

Figure 5. Influence of the substituents of the iron-

phthalocyanine on its catalytic activity. For the experi-

mental conditions, see the general catalytic procedure for

TCP degradation in the experimental section. Concen- trations of the reactants: TCP 1 mM, catalyst/T0 = 2 %

(in mol), phosphate buffer 50 mM, H,O, 6 mM.

of a cage-effect created by steric hindrance at the periphery of the l&and to protect the active catalytic center (this cage-effect has already been observed in metalloporphyrin-catalyzed oxidations [ 191). The highest catalytic activity was obtained with FePcS03SiPh3-silica (55 % conversion of TCP in 1 h, run 8) but as observed for the other catalysts, the catalytic activity occurred during the first hour, followed by an irreversible deactivation of the supported catalyst (fi9un 5). Since the green color of the supported catalyst remained during the cata- lyzed oxidation, and even when the conversion

0 “c in pyridine

FeP&&SiPb#ica

is stopped, the absence of complete TCP con- version should be attributed to a deactivation process rather than a degradation of the met- allophthalocyanine itself.

A different approach to increase the activity of these types of iron-phthalocyanine-based catalysts concerned the passivation of the hydroxyl and amino groups of the silica sup- port. The presence of these surface functional- ities could produce a decrease in the catalyst activity and the catalyst lifetime due to their own oxidation during the catalytic process lead- ing to radical species able to degrade the phthalocyanine complex. These passivation modifications were carried out on the surface of the most active supported catalyst, namely FePcSOjSiPhj-silica. The free NH, groups of the linker which were not covalently bound to the phthalocyanine were acetylated with acetyl chloride at 0 “C in pyridine ($gtire 6). Accord- ing to UV-vis data, a small part of the catalyst was desorbed during this reaction (loading of FePcSO,SiPh -silica-NHCOCH3:

? I 1.5 pmolg ). Subsequently, this new mate- riaJ was treated with trimethylsilyl chloride in order to deactivate the OH groups of the SiO, surface, which was achieved without further leaching of FePcSO,SiPh, (@gun 6). The low conversion of TCP with these passivated cata- lysts indicated that these modifications of the support material led to a loss of the catalytic

-. 0 O;Si-NHCOCH3

:H FePcSO$SiPb3-aha-NHCOCH3

1 Me3SiCl pyridine

Figure 6. Passivation of the silica surface; deactivation of the amino and hydroxyl functions.

246

Iron phthalocyanines covalently bound to silica

These two phenomena have already been described in the literature [20].

Finally, we tried to improve the catalytic activity of these supported iron phthalocy- anines by adding an organic co-solvent. TCP is not very soluble in water and by increasing its solubility, we hoped to enhance its oxidation rate. Using FePcSOQ-silica at 42 pmol.g-‘, the presence of 20 % of either ethanol or ace- tone in the reaction mixture led to an increased activity of twofold (28 % conversion) or sixfold (69 % conversion), respectively, after 2 h (jgure 8 and table I, runs 14, 1GlI). These last

activity (table 1, runs 8-l 0). The passivation of the silica surface probably strongly increased its hydrophobic character, and consequently mass transport limitations became more significant than with the non-passivated supported cata- lysts, specially in this aqueous reaction mixture.

As already mentioned, the loading of FePcS03SiPh3-silica-NHCOCH3 was lower than that of the precursor, leading to a decreased catalytic activity. It has been shown in the literature that the specific activity of attached metallophthalocyanines (for one mole of phthalocyanine complex) is directly related to the concentration of phthalocyanine fixed onto the support [2O]. In order to optimize this parameter, we prepared several samples of supported metallophthalocyanines, FePcSO, Cl-silica, with different loadings ranging from 7.5 to 300 umol.g-‘. According to the graph depicted in figure 7 (see also table I, runs 3,

0 7.5 93 17.5 21.4 420 300

Lotxling of FePcS@Cl-silica (pmol/g)

Figure 7. Influence of the loading of the support on the

catalytic activity of FePcSOaCI-silica. For the experimen- tal conditions, see the general catalytic procedure for TCP

degradation in the experimental section. Concentrations

of the reactants: TCP lmM, FePcSOaCl-silica/TCP =

2 % (in mol), phosphate buffer 50 mM, H,O, 6 mM.

ll-15), the maximal catalytic activity was obtained with a loading of 17.5 l.trnolg’. Higher as well as lower loadings led to lower catalytic activities. The decrease of activity at high loadings could be explained by the aggre- gation tendency of the metallophthalocyanine molecules which is enhanced as the concentra- tion increases. When the loading of the catalyst on the silica support is too low, the metalloph- thalocyanine molecules are probably too dis- persed to be easily accessible to the reagents due to an increase of diffusion-limitation effects.

20% ethanol .

0 1 Time (hours)

2

Figure 8. Influence of the addition of an organic co-sol-

vent on the catalytic activity of the iron phthalocyanine FePcSO&l-silica. For the experimental conditions, see

the general catalytic procedure for TCP degradation in the

experimental section. Concentrations of the reactants:

TCP 1 mM, FePcSOaCl-silica/TCP = 2 % (in mol), phosphate buffer 50 mM, H,O, 6 mM, ethanol or ace-

tone 20 %.

results are encouraging, despite the absence of full TCP conversion, since they illustrate the concept of immobilizing a metallophthalocya- nine catalyst onto a solid support (presently a modified silica) through covalent linkages is valid for the catalytic oxidative decontamina- tion of industrial aqueous effluents. Alternative types of carrier material such as neutral resins or organic polymers could be more efficient and we currently working in this direction.

1.2. Conclusion

The covalent attachment of iron phthalocy- anines onto a functionalized silica gel has been achieved. This mode of fixation provided a homogeneous surface dispersion of the metal-

247

M. Sanchez et al.

lophthalocyanine monomers without leaching in the reaction mixture. These supported cata- lysts were able to degrade a recalcitrant pollut- ant such as 2,4,6-trichlorophenol (TCP) with hydrogen peroxide as “green” oxidant. The activity of these systems is however lower than that of the corresponding homogeneous cata- lytic systems and a slow deactivation of the sup- ported catalyst is observed over time. The addition of 20 % of ethanol or acetone to the reaction mixture clearly improved the conver- sion of the TCP substrate. Optimization of this oxidation reaction with supported iron- phthalocyanine catalysts in order to achieve a complete degradation of TCP is under investi- gation as well as the use of other materials and the application of these systems to the oxida- tion of other pollutants. These supported-met- allophthalocyanines might be useful for the purification of contaminated ground-water and/or industrial aqueous effluents under ambient conditions.

2. Experimental section

The conversion of TCP was monitored by HPLC (Waters) equiped with a CL-Bondapak Cl8 column using a methanol/ammonium acetate buffer mixture (7:3, v/v; acetate buffer 50 mM pH 5 acidified to pH 4 with acetic acid) and a detection at 220 nm. The UV-vis- ible absorption spectra were recorded on a Hel- wett Packard 8452A spectrophotometer. The 3-aminopropyl-functionalized silica gel (0,9 meq NH,/g) was purchased from Aldrich [ 181. The reactants: SOC12, R,NH, Ph,SiOH, CH,COCl and Me$iCl are commercially available and were used without further purifi- cation. 2,4,6-Trichlorophenol was obtained from Janssen and hydrogen peroxide was sup- plied from Acres as a 35 wt % aqueous solu- tion. All solvents used were of analytical grade and milliQ-water was always used to prepare aqueous solution. Iron(II1) tetrasulfophthalo- cyanine (FePcS) was prepared according to pre- viously published modifications of the method of Weber and Bush [21, see ref. [7] for modi- fications].

2.1. General catalytic procedure for TCP di?pdQtiO?l

In a typical experiment, the supported cata- lysr (0.16 pmol Fe”‘, catalyst/TCP = 2 mol %)

and 40 PL of a 1.2 M aqueous solution of hydrogen peroxide (48 pmol) were added to a 1 mM TCP solution (8 mL, 8.0 pmol) in phophate buffer 50 mM (pH = 7). The reaction mixture was stirred at room temperature and analyzed by HPLC.

2.2. hvparation of FePcSO&l

A suspension of FePcS (1 .OO g, 0.88 mmol) in thionyl chloride (30 mL) was refluxed over- night under an atmosphere of dry nitrogen. Excess SOCl, was removed by distillation. Dry toluene (30 mL) was added and subsequently removed through distillation, this operation being repeated three times in order to eliminate the last traces of SOCI,. Then ether (30 mL) was added and the solid was isolated by filtra- tion, washed three times with ether (3 x 10 mL) and dried at 53 “C for 12 h. FePcS02Cl was obtained as a violet powder (0.83 g, 84 %). UV-vis (dimethylformamide/HzO = 80:20, v/v): h = 654 nm (broad), E = 82850 M-‘*cm-‘; C3,H,,C14FeN,0,S4(0H).8H~O: calcd C 34.20, H 2.60, N 9.97; found: C 34.15, H 1.48, N 9.14.

2.3. Immobilization of FePcSO&‘l

A suspension of FePcSO,Cl (95 mg, 84.6 pmol) and silica gel (4.00 g, 3.60 mmol NH,) in pyridine (10 mL) was heated to reflux for 24 h. The mixture was filtered and the solid obtained washed three times with water (3 x 20 mL), dimethylformamide (3 x 20 mL) and ether (3 x 20 mL) prior to drying at 53 “C for I2 h. FePcSO&l-silica was obtained as a green powder (3.90 g, 17.5 pmol FePcSO,Cl/g, 82 % yield). Th e content of FePcS02CI fixed onto the silica gel was found indirectly by calculating the amount of unreacted FePcSO&l using UV-vis spectroscopy. For the silicas containing 7.5 ,Umol.g-‘, 9.5 pmol.g-‘, 21.4 ymolg’, 42.0 pmol.g-’ and 300 pmol FePcSO,Cl/g, the same procedure was used starting from: 5.2 mg of FePcS02Cl + 250 mg SiO, (40 % yield), 20.6 mg of FePcSOzCl + 500 mg SiO, (26 % yield), 25.8 mg of FePcS02Cl + 500 mg SiO, (46 % yield), 32.6 mg of FePcSO&l + 500 mg SiO, (72 % yield) and 244 mg of FePcSOzCl + 250 mg SiO, refluxed three days in pyridine (34 % yield), respectively.

248

Iron phthalocyanines covalently bound to silica

2.4. Preparation of the sdfonic acid, su&zami& and sulfbnic ester phtb&cyanines supported onto silica gel

2.4.1. FePcSOTH-silica

Sulfuric acid 6 M (20 mL, 0.12 mol) was added at 0 “C to FePcSO&l-silica gel 17.5 umolg’ (0.10 g, 5.2 umol SO,Cl) and stirred at room temperature for 15 min. The solid was filtered, washed three times with water (3 x 10 mL), ethanol (3 x 10 mL) and acetone (3 x 10 mL) prior to drying at 53 “C for 12 h. The new supported catalyst FePcSOsH-silica gel was obtained as a blue powder.

2.4.2. FePcSOJVRR’-silicu

A solution of the amines Me2NH (1 mL, 2.00 mmol), i-Pr,NH (0.5 mL, 3.50 mmol) or (i-Pr)(t-Bu)NH (0.50 g, 4.30 mmol) in THF (2 mL) were added dropwise to a suspension of the supported catalyst FePcSOzC1-silica 17.5 p.mol.g-’ (0.25 g, 13.2 pmol SO,Cl) in THF (5 mL). The mixture was heated to reflux overnight, then the solid was isolated by filtra- tion, washed three times with water (3 x 10 mL), ethanol (3 x 10 mL) and acetone (3 x 10 mL) prior to drying at 53 “C for 12 h. The supported catalysts FePcSO,NMe,, FePcSO,N(i-Pr,) and FePcSOzN(i-Pr)(t-Bu) on silica were obtained as green powders.

2.4.3. FePcSO~$%pdica

A solution of triphenylsilanol (0.84 g, 3.00 mmol) in pyridine (5 mL) was added drop- wise to a suspension of the supported catalyst FePcSOzC1-silica 17.5 ymol.g-’ (1 .OO g, 52.5 j.tmol SO&l) in pyridine (5 mL). The mixture was heated to reflux overnight then the solid was isolated by filtration, washed three times with water (3 x 10 mL), ethanol (3 x 10 mL) and acetone (3 x 10 mL) prior to dry- ing at 53 “C for 12 h. The supported catalyst FePcS03SiPh3-silica was obtained as a green powder.

2.5. Passivation of the silica surface

2.5.1. Deactivation of the amino$nctions

A solution of acetyl chloride (0.5 mL, 7.03 mmol) in pyridine (2 mL) was added

dropwise to a suspension of the supported catalyst FePcSOjSiPhj-silica 17.5 Itmo1.g’ [l.OO g, 0.88 mmol Si(CH,),NH,] in pyridine (5 mL) at 0 “C. The mixture was stirred over- night at room temperature, then the solid was isolated by filtration, washed three times with water (3 x 10 mL), ethanol (3 x 10 mL) and acetone (3 x 10 mL) before drying at 53 “C for 12 h. According to UV-vis spectroscopy, a small amount of the catalyst (6 pmoi) was desorbed during the reaction (FePcSO$iPh~-sili- ca-NHCOCH3 11.5 nmol.g-‘).

2.5.2. Deactivation of the OHjimctions

Chlorotrimethylsilane (10 mL) was added dropwise to a suspension of the supported catalyst FePcS03SiPh3-silica-NHCOCH3 11.5 l.trnol.g-’ prepared by the above procedure (0.50 g) in pyridine (5 mL). The mixture was heated to reflux overnight. The solid was iso- lated by filtration, washed three times with water (3 x 10 mL), ethanol (3 x 10 mL) and acetone (3 x 10 mL) before drying at 53 “C for 12 h.

Acknowledgements

MS and AH are indebted for a post-doctoral fellowship to Elf-Atochem and for a doctoral fellowship to the European Community (TMR grant no. ERBFMBICT950030), respectively. Financial support was provided by CNRS, Elf- Atochem and EC (TMR). The authors are indebted to Laurent Fraisse (Elf-Atochem) for fruitful discussions.

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