Electrochemical behavior of phthalocyanines containing high oxidation state central metals: Titanium(IV), vanadium(IV), and tantalum(V)

The syntheses of 2,(3)-(peripheral) and 1,(4)-(non-peripheral) (2-mercaptopyridine)phthalocyanine complexes of titanium(IV) oxide (5a and 6a, respectively), vanadium(IV) oxide (7a and 8a, respectively) and tantalum(V) hydroxide (9a, peripheral only) and their electrochemical characterization are presented in this report. Their electrochemistry is compared to that of thiophenyl and thiobenzyl substituted derivatives. The non-peripherally substituted complexes are more difficult to reduce than peripherally substituted derivatives. In addition, the mercaptopyridine substituted derivatives are more difficult to reduce compared to benzylmercapto and phenylmercapto derivatives, and aryl easier reduce than alkyl substitution. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes.

Graphical abstractThe syntheses of titanium(IV), vanadium(IV) and tantalum(V) phthalocyanine complexes peripherally or non-peripherally substituted with mercaptopyridine groups is described. The non-peripherally substituted complexes are more difficult to reduce than peripherally substituted derivatives.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► V, Ti and Ta phthalocyanines were synthesized. ► The complexes contain 2-mercaptopyridine at α or β positions. ► Ti and Ta phthalocyanines are reduced both at the ring and at the central metal. ► V complexes are reduced only at the ring.