Three copper coordination compounds are synthesized using a nitrogen-based ligand, an oxygen-based ligand, or a ligand that has both oxygen and nitrogen binding sites. One compound appears purple, another appears blue, and the last appears green. Which compound was formed with the oxygen-based ligand? Why?

A The purple compound because oxygen is a weaker field ligand than nitrogen, which results in absorbance of a longer wavelength of light
B. The purple compound because oxygen is a stronger field ligand than nitrogen, which results in absorbance of a shorter wavelength of light.
C. The green compound because oxygen is a weaker field ligand than nitrogen, which results in absorbance of a longer wavelength of light.
D. The green compound because oxygen is a stronger field ligand than nitrogen, which results in absorbance of a shorter wavelength of light.