High-level ab initio calculations on the energetics of low-lying spin states of biologically relevant transition metal complexes: a first progress report.

Although DFT is the unrivaled method of choice for quantum chemical studies of bioinorganic problems, little is known about its ability to predict the energetics of the low-lying electronic states of transition metal complexes. The first high-level ab initio calculations aimed at calibrating DFT vis-a-vis this issue indicate that, despite its many successes, DFT is far from infallible. In the short term, additional calibration of DFT against more elaborate ab initio methods remains an important goal for computational bioinorganic researchers. In the longer term, we are optimistic that high-level ab initio methods such as CASPT2 and CCSD(T) will be regularly used to study realistic molecules of genuine biochemical interest.