Spectroscopic details on the molecular structure of pyrimidine‑2‑thiones heterocyclic compounds: computational and antiviral activity against the main protease enzyme of SARS-CoV-2

Table 2 Excitation energies, maximum wavelengths, oscillator strengths and % orbital contribution for the computationally studied compounds

Compound	Spectral line number	Excitation energy (eV)	λ_max (nm)	F	Type of transition	% Orbital contribution
L1	1	3.883	319.26	0.138	HOMO → LUMO	66.70
	2	3.989	310.81	0.010	HOMO−1 → LUMO	58.28
	3	4.436	279.47	0.238	HOMO−2 → LUMO	61.7
L2	1	3.318	518.16	0	HOMO → LUMO	61.04
	1	3.318	518.16	0	HOMO−1 → LUMO	16.70
	2	3.002	412.98	0	HOMO → LUMO	18.00
	2	3.002	412.98	0	HOMO−1 → LUMO	58.36
	3	3.383	366.50	0.056	HOMO → LUMO	67.00
	3	3.383	366.50	0.056	HOMO → LUMO + 2	13.71
L3	1	3.497	354.53	0.067	HOMO → LUMO	69.43
	2	3.627	341.8	0.025	HOMO−1 → LUMO + 1	15.11
	2	3.627	341.8	0.025	HOMO → LUMO + 1	67.14
	3	4.053	305.91	0.278	HOMO−1 → LUMO	60.82
	3	4.053	305.91	0.278	HOMO−1 → LUMO + 1	31.70
L4	1	2.822	439.27	0.0006	HOMO → LUMO	70.24
	2	3.552	349.07	0.013	HOMO−1 → LUMO	18.00
	2	3.552	349.07	0.013	HOMO−2 → LUMO	49.02
	3	3.711	334.06	0.016	HOMO−1 → LUMO	67.03
	3	3.711	334.06	0.016	HOMO−2 → LUMO	14.47
L5	1	3.688	336.14	0.019	HOMO → LUMO	67.23
	1	3.688	336.14	0.019	HOMO → LUMO + 1	19.04
	2	4.137	299.64	0.112	HOMO → LUMO	16.02
	2	4.137	299.64	0.112	HOMO → LUMO + 1	65.00
	3	4.378	283.21	0.269	HOMO−1 → LUMO	67.37
	3	4.378	283.21	0.269	HOMO → LUMO + 1	13.26

ISSN: 2661-801X