Principal Interacting Spin Orbital: Understanding the Fragment Interactions in Open-Shell Systems

Due to the recent rise in the interests and research effort on first-row transition metal catalysis and other radical-related reactions, open-shell system is playing a much more important role in modern chemistry. However, the development of bonding analysis tools for open-shell system is still lagging behinid. In this work, we will present the principal interacting spin orbital (PISO) analysis, which is an analysis framework developed based on our previous principal interacting orbital (PIO) analysis. We will demonstrate the power of our framework to analyze different kinds of open-shell systems, ranging from simple organic radicals to much more complicated coordination complexes, from which we can see how different kinds of odd electron bonds could be identified. We will also illustrate its ability to be used in the analysis of chemical reaction, through which we can observe subtle patterns that could be helpful for tuning or rational design of related reactions.