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ABSTRACT:For the preparation of a heterogenized N,NЈ-bis(acetylacetone)ethylenediamine cobalt(II) Schiff base complex, first crosslinked polymer beads were prepared by the suspension copolymerization of styrene (48.97 mmol, 5.1 g), allyl chloride (48.97 mmol, 3.746 g), and divinyl benzene (DVB; 1.75 mmol, 0.228 g) in the presence of azobisisobutyronitrile (0.9 ϫ 10 Ϫ3 mmol, 0.15 g) as an initiator at 23 Ϯ 0.1°C under an inert atmosphere. The copolymerization of styrene, allyl chloride in the presence of gelatin (0.75 g), bentonite (2.0 g), and boric acid (2.5 g) produced beads of different crosslinked densities corresponding to the concentration of DVB in the reaction mixture. The amount of allyl chloride in the prepared beads varied from 5.40 to 7.40 mmol g Ϫ1 of beads with the amount of DVB varying from 2.0 to 0.8 mmol in the reaction mixture. A quadridentate Schiff base (acen) was prepared with ethylenediamine (5.0 mmol, 0.3 g) and acetylacetone (10.0 mmol, 1.0 g), and it was used to obtain a homogenized and heterogenized Co(II)(acen) 2 complex. The extent and arrangement of the Schiff base (acen) in the crosslinked beads depended on the availability of DVB in the reaction mixture. The amount of DVB in the reaction mixture influenced the extent of cobalt(II) ion loading, the degree of swelling, the porosity, and the pore size in the prepared beads. The beads (type IV) prepared with 1.75 mmol (0.228 g) of DVB in the reaction mixture showed a degree of swelling of 9.65% and efficiencies of loading and complexation for cobalt(II) ions of 49.4 and 85%, respectively, in comparison with beads obtained at other concentrations of DVB in the reaction mixture. The structure of free and polymer-supported Co(II)(acen) 2 complexes was verified with IR, UV, and magnetic measurements, which suggested a square planar geometry for the complexes under both conditions. The catalytic activities of the homogenized and heterogenized Co(II)(acen) 2 complexes were compared by the evaluation of the rate constant (k) for the decomposition of hydrogen peroxide. The heterogenized Co(II)(acen) 2 complex showed a high catalytic activity for the decomposition of hydrogen peroxide (k ϭ 2.02 ϫ 10 Ϫ4 s Ϫ1) in comparison with the homogenized Co(II)(acen) 2 complex (k ϭ 4.32 ϫ 10 Ϫ6 s Ϫ1). The energy of activation for the decomposition of hydrogen peroxide with the heterogenized Co(II)(acen) 2 complex was low (38.52 kJ mol Ϫ1 ) in comparison with that for the homogenized complex (73.44 kJ mol Ϫ1). In both cases, the rate of decomposition of hydrogen peroxide was directly proportional to the concentration of hydrogen peroxide and cobalt(II) ions. On the basis of experimental observations, a rate expression for the decomposition of hydrogen peroxide was derived.

N,N 0 -bis(acetylacetone)o-phenylenediamine cobalt (II) Schiff base complex and its polymer bound analogue have been prepared and characterized for their structure and catalytic activity. To prepare heterogenized analogue of the cobalt (II) complex, a new crosslinked functional polymeric beads were prepared by suspension copolymerization of styrene (48.97 mmol, 5.1 g), allylchloride (48.97 mmol, 3.746 g) and divinylbenzene (1.50 mmol, 0.195 g) in the presence of azobisisobutyronitrile (9.0 £ 10 24 mmol, 0.15 g) as initiator at 25^0.18C under inert atmosphere. The beads of variable crosslinked densities were prepared by varying the amount of divinylbenzene in a reaction mixture from 0.80 -2.00 mmol. The beads prepared with 1.5 mmol of divinylbenzene contained 4.90 mmol (0.367 g) of allylchloride as found with the chlorine content in the beads. These beads have shown optimum degree of swelling (4.83%) and maximum attachment of N,N 0 -bis(acetylacetone)o-phenylenediamine Schiff base (1.96 mmol g 21 of beads). These beads have also shown maximum loading of cobalt (II) ions on polymer anchored Schiff base (1.37 mmol g 21 of beads). The spectral and magnetic measurements have suggested a square planar structure for cobalt (II) complex both in homogeneous and heterogeneous state. The heterogenized cobalt (II) complex has shown an enhanced rate of decomposition of hydrogen peroxide with low activation energy (42.37 kJ mol 21 ) in comparison to a homogenized complex (63.59 kJ mol 21 ). The rate of decomposition has been found to be directly 475 proportional to the concentration of hydrogen peroxide and cobalt (II) complex. A suitable rate expression has been derived for the decomposition of hydrogen peroxide.

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