In contrast, in the ethylene-and propene-derived diradicals, the MECPs are very close to the triplet state minima, both structurally and energetically. For these systems, optimization of MECP was non-trivial because of a very shallow PES and the lack of analytic gradients for EOM-DIP-CCSD (which for this system is the only EOM model capable of describing the relevant states around the MECP in a balanced way). We used the conjugate gradient method and steepest decent starting from the optimized triplet geometries. Often the optimization procedure converged to a stationary point, which has one or two imaginary frequency along the seam. In these cases, we located the true MECPs by applying displacements from these stationary points and rerunning the optimization. In these systems, the crossing coordinate at MECP is the bending of the OCC angle.