Table 3.

Bond lengths in Angstroms of tetramic acid (TA) and Cu, Zn-complexes (Cu(TA-H⁺)₂(EtOH)₂), (Zn(TA-H⁺)₂(EtOH)₂) calculated by B3LYP method using the TZVP basis set. Atoms numbering refers to Figure 4.

	Complexes-bond length [Å]					Bonds	Ligand-bond length [Å]
	Bonds	Cu-complex/B3LYP	Cu-complex/X-rays	Zn-complex/B3LYP	Zn-complex/X-rays [37]		B3LYP	X-rays [37]
						O12–H13	1.0043	1.0809
–N–C– bonds	N2–C6	1.4223	1.428	1.4208	1.4261	N1–C5	1.4269	1.4326
	N2–C27	1.4191	1.420	1.4183	1.3951	N1–C27	1.4224	1.4190
	N2–C3	1.4518	1.449	1.4526	1.4517	N1–C2	1.4549	1.4353
–C=O bonds	C7–O8	1.2588	1.281	1.2566	1.2534	C6–O11	1.2423	1.2592
	C27–O28	1.2102	1.214	1.2105	1.2219	C27–O28	1.2088	1.2124
	C3–O33	1.2134	1.205	1.2139	1.2110	C2–O33	1.2105	1.2178
–C=O bond	C5–O13	1.2594	1.268	1.2596	1.2528	C4–O12	1.3116	1.3138
–C–C– bonds pyrrole ring	C3–C4	1.4536	1.451	1.4536	1.4529	C2–C3	1.4554	1.4530
	C4–C5	1.4113	1.394	1.4145	1.4116	C3–C4	1.3788	1.3836
	C5–C6	1.4807	1.483	1.4834	1.4898	C4–C5	1.4525	1.4552
–C–C– bonds carbon chain	C4–C7	1.4201	1.410	1.4260	1.4306	C3–C6	1.4489	1.4416
	C7–C9	1.5046	1.475	1.5057	1.5001	C6–C7	1.5001	1.4910
	C6–C14	1.3473	1.332	1.3470	1.3371	C5–C14	1.3516	1.3535
	C14–C16	1.4554	1.453	1.4557	1.4661	C14–C16	1.4521	1.4559
	C27–C29	1.5076	1.484	1.5078	1.4969	C27–C29	1.5064	1.4964
–C–C– bonds phenyl ring	C16–C25	1.4029	1.416	1.4029	1.3981	C16–C25	1.4036	1.4033
	C16–C17	1.4042	1.397	1.4042	1.3983	C16–C17	1.4049	1.4041
	C17–C19	1.3873	1.384	1.3874	1.3900	C17–C19	1.3868	1.3837
	C19–C21	1.3918	1.378	1.3918	1.3859	C19–C21	1.3919	1.3816
	C21–C23	1.3925	1.357	1.3925	1.3808	C21–C23	1.3928	1.3887
	C23–C25	1.3868	1.391	1.3868	1.3883	C23–C25	1.3860	1.3840
Ethanol	O34–C36	1.4362		1.4450	1.4543
	C36–C39	1.5191		1.5167	1.4814
	O34–H35	0.9647		0.96546	0.8403
–M–O– bonds MO6 unit	M1–O13	1.9791	1.930	2.0574	2.0544
	M1–O54	1.9791	1.930	2.0574	2.0544
	M1–O8	1.9938	1.936	2.0782	2.0744
	M1–O49	1.9938	1.936	2.0782	2.0744
	M1–O34	2.4688	2.522	2.2323	2.1352
	M1–O75	2.4688	2.522	2.2323	2.1352