Table 1.

Frontier molecular orbital properties for melatonin.

Chemical descriptors	Energy in kcal/mol
HOMO	−127.9554
LUMO	−15.7755
Ionization energy (I = ɛHOMO = −HOMO)	127.9554
Electron affinity (A = ɛLUMO = −LUMO)	15.7755
Energy gap = HOMO − LUMO	112.1798
Global hardness (η = (I − A) / 2)	55.9989
Global softness (S = 1 / η)	7031.7032
Chemical potential (μ = (I + A) / 2)	71.8624
Electronegativity (χ = −μ)	−71.8624
Electrophilicity index (ω = μ2 / 2η)	46.1094
Nucleophilicity index (N = 1 / ω)	8539.8611