Theoretical study of 2,5-diphenyl-1,4-distyrylbenzene (A model compound of PPV): A comparison of the electronic structure and photophysical properties of cis- and trans-isomers

2,5-Diphenyl-1,4-distyrylbenzene (DPDSB), a model compound of PPV, have been synthesized with two isomers: cis- and trans-DPDSB in our lab. We have found three distinguishing features of photophysical properties between these two isomers. To explain these three special spectral behaviors, the quantum-chemical computations were performed to investigate the ground-state and excited-state molecular geometries, electronic structure, absorption and emission properties, potential-energy curve of the ground-state and excited-state, and so on. According to our calculated results, the nature causing above distinguishing photophysical properties is larger configuration displacement of cis-DPDSB than trans-DPDSB from the ground-state to the excited-state, especially for the changes in torsion angle along vinyl double bonds in cis-DPDSB.