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Time-Resolved Transient Optical Absorption Study of Bis(terpyridyl)oligothiophenes and Their Metallo-Supramolecular Polymers with Zn(II) Ion Couplers
journal contribution
posted on 2015-06-18, 00:00 authored by David Rais, Miroslav Menšík, Pavla Štenclová-Bláhová, Jan Svoboda, Jiří Vohlídal, Jiří Pflegerα,ω-Bis(terpyridyl)oligothiophenes
spontaneously assemble with Zn(II) ions giving conjugated constitutional
dynamic polymers (dynamers) of the metallo-supramolecular class, which
potentially might be utilized in optoelectronics. Their photophysical
properties, which are of great importance in this field of application,
are strongly influenced by the dynamic morphology. It was assessed
in this study by using ultrafast pump–probe optical absorption
spectroscopy. We identified and characterized relaxation processes
running in photoexcited molecules of these oligomers and dynamers
and show impacts of disturbed coplanarity of adjacent rings (twisting
the thiophene–thiophene and thiophene–terpyridyl bonds
by attached hexyl side groups) and Zn(II) ion couplers on these processes.
Major effects are seen in the time constants of rotational relaxation,
intersystem crossing, and de-excitation lifetimes. The photoexcited
states formed on different repeating units within the same dynamer
chain do not interact with each other even at very high excitation
density. The method is presented that allows determining the equilibrium
fraction of unbound oligothiophene species in a dynamer solution,
from which otherwise hardly accessible values of the average degree
of polymerization of constitutionally dynamic chains in solution can
be estimated.