When two chromophores interact with each other forming dimers, the electronically excited states of the combined system are more complex than those of the individual chromophores. In addition to monomer-like states,  delocalized excitonic  or charge transfer states may exist. We have investigated the electronically singlet excited states of dimers of DNA bases and their fluorescent analogs. The photophysical and photochemical behavior of nucleobases is very important because of their biological role as the building blocks in DNA and RNA. Fluorescent analogs of the natural bases are also important and are used as fluorescent probes to monitor various processes in DNA.  Although great progress has been made in understanding the excited-state properties of monomers, the excited states and dynamics of dimers and beyond are not well  understood.  The excited states of p-stacked nucleobases and their fluorescent analogs have been investigated using various ab initio methods and the performance of these methods on excitation energies and excitonic couplings will be discussed. Furthermore, we have investigated  spectroscopic and dynamical properties of the excited  states, focusing on mechanisms for fluorescence quenching.

Excited electronic states of nucleobase dimers

239th National Meeting (2010)

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