Chemistry in Pictures: Looking for electrons

Preston J. MacDougall, a professor at Middle Tennessee State University, wanted to understand where electrons tended to reside and where they stayed away from in a crystal of a diiron cluster compound. Such information could help him understand how and why this cluster’s two iron atoms (one atom is shown at center in blue) bind to diazene (pink molecule at top right), which is an intermediate in converting nitrogen into ammonia, a fertilizer and useful raw material. To find where the electrons were hanging out, he created this image using an X-ray crystal structure and several computer modeling programs. It shows the calculated curvature of the electron density in the crystal. Orange, red, pink, and white signify areas with progressively higher concentration of electron density, while yellow, green, and blue signify the extent of charge depletion.

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