Mono-crowned substituded iron porphyrin: synthesis, analytical properties and catalytic activity

Abstract

A substituted porphyrin bearing a crown ether unit, H 2( M 18 C 6 P ), was synthesized from the reaction between (5-mono(o-aminophenyl)10,15,20-triphenylporphyrin) and the acyl derivative of the ether (4-carboxy-18-crown-6). The corresponding iron porphyrin, Fe ( M 18 C 6 P ) Cl , was obtained through iron insertion into H 2( M 18 C 6 P ). The new free-base porphyrin was analyzed by C , N , and H elemental analysis, UV-vis and IR spectroscopies, electrospray mass spectrometry (MS) and 1 H NMR. It selectively extracts 18% of the K + ions present in aqueous medium to the organic phase (chloroform). UV-vis spectroscopy studies showed that H 2( M 18 C 6 P ) is also capable of forming aggregates with K +, probably the 1:1 complex, in methanol. This happens because the ionic radius of the potassium ion is appropriate for its accommodation inside the cavity of the crown ether, and also because of the associative effect between the porphyrin and the crown ether unit. The iron porphyrin Fe ( M 18 C 6 P ) Cl was used as catalyst for the epoxidation of cyclooctene by iodosylbenzene or sodium hypochlorite, in methanol or biphasic water/dichloroethane system, respectively. The results obtained with sodium hypochlorite show that Fe ( M 18 C 6 P ) Cl is a potential catalyst for selective oxidations, because the crown ether unit can select or orient substrates. This iron porphyrin can also be employed as a catalyst in a biphasic water/organic solvent system, with no need of a phase transfer agent.