Control of photoinduced electron transfer in zinc phthalocyanine- perylenediimide dyad and triad by the magnesium ion

Shunichi Fukuzumi, Kei Ohkubo, Javier Ortiz, Ana M. Gutiérrez, Fernando Fernández-Lázaro, Ángela Sastre-Santos

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Abstract

Photoexcitation of a zinc phthalocyanine-perylenediimide (ZnPc-PDI) dyad and a bis(zinc phthalocyanine)-perylenediimide [(ZnPc)2-PDI] triad results in formation of the triplet excited state of the PDI moiety without the fluorescence emission, whereas addition of Mg2+ ions to the dyad and triad results in formation of long-lived charge-separated (CS) states (ZnPc +-PDI-/Mg2+ and (ZnPc)2 +-PDI-/Mg2+) in which PDI- forms a complex with Mg2+. Formation of the CS states in the presence of Mg2+ was confirmed by appearance of the absorption bands due to ZnPc+ and PDI-/Mg2+ complex in the time-resolved transient absorption spectra of the dyad and triad. The one-electron reduction potential (Ered) of the PDI moiety in the presence of a metal ion is shifted to a positive direction due to the binding of Mg2+ to PDI-, whereas the one-electron oxidation potential of the ZnPc moiety remains the same. The binding of Mg2+ to PDI- was confirmed by the ESR spectrum, which is different from that of PDI- without Mg2+. The energy of the CS state (ZnPc+-PDI-/Mg2+) is determined to be 0.79 eV, which becomes lower that of the triplet excited state (ZnPc-3PDI *: 1.07 eV). This is the reason why the long-lived CS states were attained in the presence of Mg2+ instead of the triplet excited state of the PDI moiety.

Original languageEnglish
Pages (from-to)10744-10752
Number of pages9
JournalJournal of Physical Chemistry A
Volume112
Issue number43
DOIs
StatePublished - 30 Oct 2008

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