Ultrafast IR spectroscopy of polymeric cytosine nucleic acids reveal the long-lived species is due to a localised state

Abstract

The decay pathways of UV-excited cytosine polymers are investigated using picosecond time-resolved infrared spectroscopy. Similar yields of a non-emissive ¹nπ* state are found in the single-stranded dC₃₀ polymer as in the dCMP monomer, but with a longer lifetime in the polymer (80 ps vs. 39 ps). A longer lifetime is also found in the d(CpC) dinucleotide. No evidence of excimer states is observed, suggesting that localised ¹nπ* excited states are the most significant intermediates present on the picosecond timescale.