Electro- and magneto-electrochemistry of zeolite Y- and MCM-41-associated bipyrylium ion

The electrochemical response of bipyrylium bication [1,4-bis(3,5-diphenyl-4-pyrylium)phenylene] associated with Y and MCM-41 aluminosilicates (BTP@Y and BTP@MCM, respectively) is described using polymer-film electrodes immersed into Et4N+ + MeCN and Bu4N+ + MeCN electrolytes. BTP@MCM provides a solution-like response in all electrolytes consisting in two successive strongly comproportionation mediated one-electron reduction processes near to +0.05 and -0.12 V vs. Ag vertical bar AgCl. The response of BTP@Y in BU4N+ + MeCN is restricted to a unique reduction process near to -0.40 V, while in Et4N+ + MeCN, it differs significantly: here, two reduction processes at -0.22 and -0.36 V appear. This response suggests the presence of different boundary-associated topological redox isomers for which no significant comproportionation reaction occurs. Under the application of a static magnetic field, the electrochemical response of BTP@MCM remains almost unchanged while that of BTP@Y in contact with Et4N+ + MeCN is sensitive to changes in the orientation and strength of the external magnetic field. Such magneto-electrochemical effects are consistent with the idea that different boundary-associated orientation isomers of BTP@Y exist. (c) 2004 Elsevier B.V. All rights reserved.