Spectroscopic investigation of the ultrafast photoinduced dynamics in pi-conjugated terpyridines.

Ultrafast light-induced processes in a series of pi-conjugated mono-, bis-, tris- and tetrakis(terpyridine) derivatives are investigated by femtosecond time-resolved spectroscopy. Non-exponential excited-state dynamics involving singlet-triplet intersystem crossing are observed which span from picoseconds to nanoseconds (see figure). Time-resolved spectroscopy is applied to investigate the ultrafast relaxation dynamics of several pi-conjugated mono-, bis-, tris- and tetrakis(terpyridine) derivatives. This particular series of structurally closely related systems was prepared applying efficient synthetic strategies and resembles key building blocks for a wide range of photoactive complexes, dendrimers and metallo-polymers with resulting potential applications, for example, in photovoltaics or as organic light-emitting diodes. Aiming for applications of supramolecular assemblies based on these recently presented terpyridine ligands a detailed knowledge of the light-induced processes of the ligands themselves represents a prerequisite. By applying femtosecond time-resolved absorption spectroscopy in concert with time-resolved fluorescence and Raman measurements, we detail the photophysical properties.