https://courses.lumenlearning.com/introchem/chapter/transition-metals/

https://www.semanticscholar.org/paper/A-Luminescent-Zinc(II)-Metal-Organic-Framework-with-Yao-Cui/290c6771ec14f9ae7c71d14a11012beb15dd8ca5/figure/0

Metal to Ligand and Ligand to Metal Charge Transfer Bands

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Spectroscopy/Electronic_Spectroscopy/Metal_to_Ligand_and_Ligand_to_Metal_Charge_Transfer_Bands