Transient behavior of 2-(2',4'-dinitrobenzyl)pyridine photochromism studied by ultrafast laser spectroscopy

Ultrafast transient behavior of photochromic 2-(2',4'-dinitrobenzyl)pyridine has been studied using ferntosecond transient absorption spectroscopy. Three different transient signals could be found in the experiment at different time delays. The dynamics of transient behavior in the short time scale reveal that very fast relaxation (similar to400 +/- 100 fs) from the initial excited state leads to the formation of a relatively stable intermediate which is the precursor of proton transfer. The intermediate relaxes to the ground state of proton transferred aci-nitro structure in nanosecond time scale. The relatively slow proton transfer in DNBP is due to the necessity of extensive structural rearrangement before proton transfer. Solvent hydrogen bonding in ethanol seems to play an important role in the deactivation of the excited state giving entirely different photophysical behavior. (C) 2004 Elsevier B.V. All rights reserved.