Infrared spectroscopy metal-dioxygen complexes

Infrared spectroscopy can be used to classify metal-dioxygen complexes as either superoxo species (p(O-O) from 1200 to 1070 cm-1) or as peroxo species (p(O-O) from 930 to 740 cm-1) (49). However, this system fails to accurately define the type of dioxygen species present in 8 and 15, as these complexes exhibit v(O-O) absorptions at 961 and 941 cm-1, respectively. Preparation of the complexes with 180-enriched dioxygen confirmed that the dioxygen was bound side-on (if) in these complexes Complex 8 exhibited isotopically shifted vibrations indicative of a side-on bound dioxygen 0(160-160) absorption at 961 cm-1, p(160-180) at 937 cm-1, and /(180-180) at 908 cm-1), as did complex... 

The stretching frequencies attributed to the 0-0 vibration are closely related to the structural type. Type I complexes show 0-0 stretching vibrations around 1125 cm-1 and type II around 860 cm-1. This sharp difference enables the O-O stretching frequency as measured by infrared or Raman spectroscopy to be used for structure type classification. Table 16.2.2 lists the structural data of dioxygen metal complexes. 

---