Octakis(dodecyl)phthalocyanines: Influence of Peripheral versus Non-Peripheral Substitution on Synthetic Routes, Spectroscopy and Electrochemical Behaviour.

Non-peripherally octakis-substituted phthalocyanines ( np Pc's), MPc(C 12 H 25 ) 8 with M = 2H ( 3 ) or Zn ( 4 ), as well as peripherally octakis-substituted phthalocyanines ( p Pc's) with M = Zn ( 6 ), Mg ( 7 ) and 2H ( 8 ), were synthesized by cyclotetramerization of 3,6- ( 2 ) or 4,5-bis(dodecyl)phthalonitrile ( 5 ), template cyclotetramerization of precursor phthalonitriles in the presence of Zn or Mg, metal insertion into metal-free phthalocyanines, and removal of Mg or Zn from the phthalocyaninato coordination cavity. The more effective synthetic route towards p Pc 8 was demetalation of 7 . np Pc's were more soluble than p Pc's. The Q-band λ max of np Pc's was red-shifted with ca. 18 nm, compared to that of p Pc's. X-ray photoelectron spectroscopy (XPS) differentiated between N-H, N meso and N core nitrogen atoms for metal-free phthalocyanines. Binding energies were ca. 399.6, 398.2 and 397.7 eV respectively. X-ray photoelectron spectroscopy (XPS) also showed zinc phthalocyanines 4 and 6 have four equivalent N meso and four equivalent N-Zn core nitrogens. In contrast, the Mg phthalocyanine 7 has two sets of core N atoms. One set involves two N core atoms strongly coordinated to Mg, while the other encompasses the two remaining N core atoms that are weakly associated with Mg. p Pc's 6 , 7 , and 8 have cyclic voltammetry features consistent with dimerization to form [Pc][Pc + ] intermediates upon oxidation but np Pc's 3 and 4 do not. Metalation of metal-free p Pc's and np Pc's shifted all redox potentials to lower values.