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Metal Ion Enhanced Charge Transfer in a Terpyridine-bis-Pyrene System
Molecular Photonics Group, Van’t Hoff Institute for Molecular Sciences, Universiteit Van Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam, The Netherlands
Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Mendelstrasse 7, D-48149 Münster, Germany
* Author to whom correspondence should be addressed.
Received: 7 April 2009; in revised form: 8 May 2009 / Accepted: 12 May 2009 / Published: 13 May 2009
Abstract: The synthesis, electrochemical and photophysical properties of a branched molecule 3,5-bis(pyrene-1-yl)-4'-phenyl-2,2':6',2''-terpyridine are reported. Spectroscopy in different solvents reveals that an optical electron transfer from the pyrene donor to the terpyridyl electron acceptor can occur in polar media, as the system displays both charge transfer (CT) absorption and CT emission. Furthermore, the study of the zinc complex as well as the bis-protonated form shows an enhancement of the electron transfer character of the system, by an increase of the acceptor strength. This is accompanied by a large increase of the non-radiative processes. With sub-nanosecond transient absorption spectroscopy, the CT state, consisting of the pyrene radical cation and the terpyridine radical anion, has been detected. At room temperature, the study of the nanosecond transient absorption spectra reveals the formation of a low-lying triplet excited state that we attribute to the pyrene moiety through which the CT state decays. At 77K, the absence of the terpyridine triplet emission also suggests the population of a low-lying triplet state of the pyrene unit.
Keywords: branched molecules; spectroscopy; ion complexation; excited state absorption; emission; molecular polarity sensor
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D’Aléo, A.; Cecchetto, E.; De Cola, L.; Williams, R.M. Metal Ion Enhanced Charge Transfer in a Terpyridine-bis-Pyrene System. Sensors 2009, 9, 3604-3626.
D’Aléo A, Cecchetto E, De Cola L, Williams RM. Metal Ion Enhanced Charge Transfer in a Terpyridine-bis-Pyrene System. Sensors. 2009; 9(5):3604-3626.
D’Aléo, Anthony; Cecchetto, Elio; De Cola, Luisa; Williams, René M. 2009. "Metal Ion Enhanced Charge Transfer in a Terpyridine-bis-Pyrene System." Sensors 9, no. 5: 3604-3626.