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.
Highlights
In the last decades, in order to gain more insight into electron transfer processes, extensive studies have been carried out on the optical behavior of chromophoric molecular systems consisting of electron donor and acceptor groups connected via different bridges [1,2]
In the poly- and oligo-phenylene vinylene (OPV) derivatives covalently linked to a bipyridine system reported by Wasielewski et al [13] an enhancement of the electronic delocalization on the polymer backbone and a red shift of the emission was observed upon addition of particular ions [e.g. Zn(II)]
Systems have been used in order to show the occurrence of emissive charge-transfer states in their zinc (II) complexes, such as bipyridine linked to a donor group [14] or to a pyrene unit via an oligo-phenylene bridge [15,16], conjugated pyrenethiophene-terpyridine [17], or OPV terminated by a terpyridine unit
Summary
In order to gain more insight into electron transfer processes, extensive studies have been carried out on the optical behavior of chromophoric molecular systems consisting of electron donor and acceptor groups connected via different bridges [1,2]. The emission spectrum of the free ligand in THF (Figure 5) shows a broad but somewhat structured emission band centered at 400 nm that is attributed to the local excited (LE) state of the pyrene.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
