Modulating the Roaming Dynamics for the NO Release in ortho- Nitrobenzenes

The dynamics of NO release upon photodissociation of nitroaromatic compounds is dependent on the nature of the interaction between the NO2 group and substituent in the ortho position. A bimodal (slow and fast) translational energy distribution of the NO photofragment indicates the presence of two distinct NO elimination channels. The slow-to-fast branching ratio for the NO release is regulated by the hydrogen bonding ability of the ortho substituent and follows the order [OH > NH2 > CH3 > OCH3], indicating that the intramolecular hydrogen bonding plays a pivotal role in NO release dynamics. Further, the topology of the triplet state potential energy surface acts as a doorway to the dissociation pathway switching between the roaming and nonroaming mechanisms, with hydrogen bonding substituents (OH and NH2) favoring the roaming mechanism.

Automated summary

The release of NO upon photodissociation of nitroaromatic compounds is influenced by the interaction between the NO2 group and substituent in the ortho position. Two distinct NO elimination channels are observed with a bimodal translational energy distribution of the NO photofragment. The hydrogen bonding ability of the ortho substituent regulates the ratio of slow-to-fast branching for NO release, with OH and NH2 favoring the roaming mechanism.