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Wiley, ChemPhysChem, 1(10), p. 276-281, 2009

DOI: 10.1002/cphc.200800612

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Femtosecond to Subnanosecond Multistep Calcium Photoejection from a Crown Ether-Linked Merocyanine

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

Photoinduced calcium release from the crown ether-linked merocyanine DCM-crown was reexamined by femtosecond transient absorption spectroscopy with sub-100-fs time resolution. Photodisruption of the bond linking the cation to the nitrogen atom shared by the crown and the chromophore is found to take place in 130 fs. Confirming our previous reports, the photoinduced intraligand charge transfer is observed in the picosecond regime but a three-component kinetics (1 ps, 8 ps and 77 ps), together with a 56-ps stimulated-emission time-resolved red shift, are found in the present study. Both delayed intraligand charge transfer and cation release are assumed to occur in this time range due to repulsion effects between the positively charged nitrogen of the crown ether moiety and the cation. In the sub-nanosecond regime, a 670-ps time-resolved red shift of the stimulated-emission spectrum of the charge-transfer state, similar to the shift previously observed with Sr2+, demonstrates the motion of the cation away from the crown to the bulk. A thorough examination of the present data allows us to conclude that calcium ion is photoejected to the bulk in a multistep process.