Early bird or night owl? Controlling the ultrafast photodynamics of triphenylamine substituted 2,2′:6′,2′′-terpyridine

Controlling the ultrafast photodynamics of metal-free organic molecules has great potential for technological applications. In this work, we use solvent polarity and viscosity as "external knobs" to govern the photodynamics of an electron-donating derivative of 2,2 ':6 ',2 ''-terpyridine (terpy), namely 4 '-(4-(di(4-tert-butylphenyl)amine)phenyl)-2,2 ':6 ',2 ''-terpyridine (tBuTPAterpy). We combine femtosecond fluorescence upconversion (FlUC), transient absorption (TA) and quantum mechanical calculations to provide a comprehensive description of the tBuTPAterpy's photodynamics. Our results demonstrate that, by changing the solvent, the time scale of light-induced conformational changes of the system can be tuned over two orders of magnitude, controlling the tBuTPAterpy fluorescence spectral region and yield. As a result, depending on the local environment, tBuTPAterpy can act either as an "early bird" or a "night owl", with a tunability that makes it a promising candidate for metal-free sensors. 4 '-(4-(di(4-tert-butylphenyl)amine)phenyl)-2,2 ',6 ',2 ''-terpyridine presents a complex photodynamics tuned by the local environment, making it either an 'early bird' or a 'night owl'.