Stabilization of activated fragments by shell‐wise construction of an embedding environment

An activated fragment which is structurally unstable when considered isolated can be stabilized through binding to a suitable molecular environment; for instance, to a transition‐metal fragment. The metal fragment may be designed in a shell‐wise build‐up of a surrounding molecular environment. However, adding more and more atoms in a consecutive fashion soon leads to a combinatorial explosion of structures, which is unfeasible to handle without automation. Here, we present a fully automated and parallelized framework that constructs such an embedding environment atom‐wise. Molecular realizations of such an environment are constructed based on simple heuristic rules intended to screen a sufficiently large portion of the possible compound space and are then subsequently optimized by electronic structure methods. (Constrained‐optimized) structures are then evaluated with respect to a scoring function, for which we choose here the concept of gradient‐driven molecule construction. This concept searches for structure modifications that reduce the forces on all atoms. We develop and analyze our approach at the example of CO 2 activation by reproducing a known compound and mapping out possible alternative structures and their effect on the stabilization of a (bent) CO 2 ligand. For all generated structures, the nuclear gradient on the activated fragment and its coordination energy are evaluated to steer the design process.