Influence of substituents, reaction conditions and central metals on the isomer distributions of 1(4)-tetrasubstituted phthalocyanines

The 1(4)- and 2(3)-tetraalkoxy-substituted nickel (5), copper (6), and meta l-free phthalocyanines 7 and 8 were synthesized from the corresponding subs tituted phthalonitriles 2 and 4, respectively, and the four structural isom ers formed for each phthalocyanine were separated by HPLC. In the case of 1 (4)-tetraalkoxy-substituted phthalocyanines the ratio of the four isomers w as found to be different from the expected statistical distribution of D-2h :C-5:C-2v:C-4h = 12.5:50:25:12.5. For the 1(4)-substituted metal-fret: phth alocyanine 7 a very high proportion of the C-4h isomer (87%) is formed. In the case of the 1(4)-substituted metal phthalocyanines 5 and 6 the striking ly low proportion of the D-2h isomer (found: 2-4% compared to statistical d istribution: 12.5%) is interpreted by a template mechanism (given in Scheme 2) in which strong steric hindrance of the respective neighboring groups p revent the formation of the D-2h isomer. To investigate further the mechani sm of formation of phthalocyanines the synthesis of 1(4)- and 2(3)-tetraalk oxy-substituted metal phthalocyanines containing chiral alkoxy groups (13-1 7) was studied under different reaction conditions starting from the corres ponding alkoxy-substituted phthalonitriles 10 and 11. In all investigated c ases the chiral alkoxy groups in the starting phthalonitrile again affect t he distribution of the structural isomers of the formed phthalocyanines, le nding to a higher proportion of the C-4h isomer in comparison with the 1(4) -tetraalkoxy-substituted phthalocyanines with racemic alkoxy groups.