. 2026 Jan 20;16(5):4473–4485. doi: 10.1039/d5ra06131h

Table 2. Calculated transition energies (eV), maximum absorption wavelengths (λ_max), oscillator strengths (f_os), and major molecular orbital (MO) contributions for the HP and HP–Cu²⁺ complex.

Compound	λ (nm)	E (eV)	f _os	MO contributions (major contribution, <30%)
HP	292.21	4.24	0.33	HOMO > LUMO (78%)
	281.90	4.40	0.162	H − 1 > LUMO (44%)
	275.40	4.50	0.0248	HOMO > L + 1(38%), HOMO > L + 2 (42%)
HP–Cu²⁺	2389.34	0.518	0.0048	HOMO(B) > LUMO(B) (98%)
	1262.17	0.982	0.0196	H − 2(B) > LUMO(B) (36%), H − 1(B) > LUMO(B) (60%)
	943.62	1.31	0.1052	H − 2(B) > LUMO(B) (58%), H − 1(B) > LUMO(B) (36%)

Table 2. Calculated transition energies (eV), maximum absorption wavelengths (λmax), oscillator strengths (fos), and major molecular orbital (MO) contributions for the HP and HP–Cu2+ complex.