Synthesis and mechanistic studies of chromium(III) porphyrazines

Abstract

The octakis(propyl)porphyrazinemagnesium(II) complex has been prepared by the addition of bromine to 4-octyne in the presence of acetic acid to produce a trans-dibromoalkene. These vinylic dibromides have been converted to fumaronitriles via a Rosenmund - von Braun reaction. The fumaronitriles have been photoisomerised to the corresponding maleonitriles. Mixed Linstead macrocyclisation of the maleonitrile in the presence of magnesmm butoxide has yielded the octakis(propyl)porphyrazinemagnesium(II) complex. 2,3,9,10,16,17,23,240cta-substituted phthalocyanine has been prepared by reacting a solution of 4-nitrophthalonitrile with phenol in the presence of tetrahydrofuran, at lower temperatures to form the 1,2-diisocyano-4-phenoxybenzene. The phenoxybenzene has been further reacted with 1,8 diazabicyclo[5,4,0]-undec-7-ene, in the presence of methanol to give the 2,3 ,9, 10, 16, 1 7 ,23 ,24octa-substituted phthalocyanine. The octakis(propyl)porphyrazinemagnesium(II) complex has been demetallated with trifluoroacetic acid, to give a freebase compound which has been metallated centrally with cobalt(II) and chromium(III) ions. In addition the octakis(propyl)porphyrazinemagnesium(II) complex and the 2,3 ,9, 10, 16, 17,23 ,24octa-substituted phthalocyanine have been metallated centrally with chromium(III) ion. The reduction of octakis(propyl)porphyrazinechromium(III) complex using octakis(propyl)porphyrazine cobalt(II) complex has been investigated. The kinetics of both the chromium(III) insertion into the octakis(propyl)porphyrazinemagnesium(II) complex and the 2,3,9, 10, 16, 17,23,24octa-substituted phthalocyanine and reduction of octakis(propyl)porphyrazinechromium(III) complex with octakis(propyl) porphyrazinecobalt(II) complex have been followed spectrophotometrically at temperatures ranging from l 5°C to 35°C. The reactions have been found to follow pseudo-first order kinetics. Mechanisms of the insertion and reduction of chromium(III) ion have been proposed.