1,10-Phenanthroline, ionization energy

Several groups have applied theoretical and quantum chemical calculations to many aspects of the phenanthrolines over the past two decades. The -electron distributions in all the phenanthrolines have been determined, and they are generally in accord with the known chemical reactions of the molecules.37 Resonance energies of 1,7- and 1,10-phenanthrolines have been calculated and compared with those of 7-aminoquinoline and 8-aminoquinoline, respectively.38 Calculations applied to 1,10-phenanthroline and methyl-substituted derivatives have been correlated with their reduction potentials39 and ionization constants.40 Bond lengths for most of the phenanthrolines have been computed.41... 

On the contrary the MLCT bands are present when the central metal has a low ionization potential and at least one ligand possesses an empty accessible n orbital (CN-, CO, pyridine, phenanthroline, etc.). They are generally allowed transitions and therefore they originate intense bands with a quite high energy, lying in the UV or blue region of the visible. 

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