Lastly, the ground-and excited-state properties for all 25,000 geometries were obtained using the complete active space self-consistent field (CASSCF) approach in conjunction with the double-ζ cc-pVDZ basis set as implemented in OPENMOLCAS . For this purpose, an active space of two active electrons in two orbitals, including the πand π * -orbitals of the C=C double bond was chosen. The electronic properties of the individual three lowest lying singlet states (S 0 , S 1 , and S 2 ) and their couplings were obtained using state-averaging of these three singlet states -i.e. SA(3)-CASSCF(2,2).