Molecular dynamics study of the solid state photoreactivity of 3- and 4-cyano-trans-cinnamic acids

Molecul ar dynami cs (MD ) simul ation studies show the importance of molecul ar moti on and optimal n-n overl ap of incipient reacti ve double bunds in the topochemical photodi meri sati on reactions of 3and 4-cyanoci nnami c acids. These simulati ons have heen carried out in mi nicrystals consi sting of 180 molecul es and confirm earl ier conclusions arising from packi ng calculations of static structu res. A two-step diradica l pathway for the cl imerisation is possi ble. A stepwise MD study has also been performed in which two mo lecules at the centres of the min icrystals have been dimerised and these calcul ati ons reveal the importance of thermal motion in these solid strue photochemical reactions.