Effect of external electric field on ground and singlet excited states of phenylalanine: A theoretical study

The effect of external electric field on the ground and few singlet excited states of phenyalanine are studied in the light of TDDFT (time dependent density functional theory) and DFRT (density functional reactivity theory). The excited state geometries are compared with the ground state ones. Sensitivity of the reactivity parameters such as total electronic energy, energy of the HOMO (highest occupied molecular orbital), global hardness (η), electrophilicity (ω) etc. towards the external electric fields are measured by varying the applied field strength. Variation of aromaticity of the ground and excited states are gauged in terms of nucleus independent chemical shift (NICS). Geometry, reactivity and aromaticity of the ground as well as excited states are responsive to the presence of external electric field.