High liquid–liquid extraction selectivity of Fe(II) and Pb(II) with TD-DFT theoretical calculations of long chain acid pyrazole- and triazole-based ligands

Figures & data

Figure 1. General structure of the ligands (L1–L4).

Table 1. Comparison of ¹H NMR and ¹³C NMR chemical shifts for the different ligands

Ligand	RMN1H ppm	RMN13C ppm
	δ(N–CH2–N)	δ(N–CH2–N)
L1	4.87	65.36
L2	4.89	65.35
L3	5.15	64.05
L4	5.01	65.82

Table 2. Efficiency of individual extraction of metal ions E (%) using L1–L4

	Fe^2+ (%)	Cu^2+ (%)	Pb^2+ (%)	Cd^2+ (%)	Ni^2+ (%)	Zn^2+ (%)	Co^2+ (%)
L1	47.70	20.27	22.95	21.37	0.06	1.49	1.95
L2	97.29	50.75	86.18	40.60	0.12	5.38	4.90
L3	89.93	65.37	91.63	26.76	14.71	8.70	12.03
L4	90.37	41.06	80.73	43.45	4.22	5.99	5.05

Table 3. Efficiencies of the competitive extraction E (%) of metal ions using L1–L4

	Fe^2+ (%)	Cu^2+ (%)	Pb^2+ (%)	Cd^2+ (%)
L1	39.35	14.44	48.67	13.38
L2	79.08	14.93	25.99	17.20
L3	16.38	27.61	38.33	13.80
L4	75.41	8.66	17.59	11.89

Table 4. Back-extraction of metal ions extracted with using L1–L4

	Fe^2+ (%)			Pb^2+ (%)
	L2	L3	L4	L3
HCl 1 M	91.90	87.82	90.81	63.50
HNO3 1 M	77.79	72.95	79.26	85.66
H2SO4 1 M	82.27	92.12	85.13	57.08

Table 5. Quantum chemical parameters for L1–L4 obtained by using B3LYP/6-31G(d, p)

Property (eV)	L1	L2	L3	L4
EHOMO	−6.066508624	−6.073583587	−6.715772533	−6.309778504
ELUMO	0.316740649	0.340414564	−0.150206906	0.312114712
ΔE = ELUMO − EHOMO	6.383249274	6.413998151	6.565565627	6.621893217
Electronegativity (χ)	2.874883987	2.866584512	3.432989719	2.998831896
Chemical hardness (η)	−3.191624637	−3.206999076	−3.282782813	−3.310946608
Softness (σ)	−0.313320053	−0.311817988	−0.304619604	−0.302028428
Chemical potential (μ)	−2.874883987	−2.866584512	−3.432989719	−2.998831896
Electrophilicity index (ω)	−1.29478853	−1.281152032	−1.795034744	−1.358069731

Table 6. Some experimental and theoretical wavenumbers for L1–L4 obtained by using B3LYP/6-31G (ν: Stretching)

L1		L2		L3		L4		Streching bond
Theoretical wavenumbers (cm^−1)	Experimental wavenumbers (cm^−1)	Theoretical wavenumbers (cm^−1)	Experimental wavenumbers (cm^−1)	Theoretical wavenumbers (cm^−1)	Experimental wavenumbers (cm^−1)	Theoretical wavenumbers (cm^−1)	Experimental wavenumbers (cm^−1)
1501	1508	1502	1538	1500	1508	1478	1470	ν C=N
–	–	–	–	1507	–	1489	–
1610	1558	1609	1636	–	–	1550	1541	ν C=C
–	–	1610	–	–	–	1553	–
1792	1732	1751	1717	1751	1715	1751	1707	ν C=0
3034	3047	3017	3038	3069	2918	3063	2922	νSym CH2 (NCN)
–	–	3029	–	–		3074	–
3100	3134	3134	3132	3137	3117	3132	3119	νAsym CH2 (NCN)
–	–	3139	–	3143	–	3138	–
–	–	3285	3204	3319	3254	3295	3213	ν CH Ring
3284	3202	3287	–	3321	3283	3298	3244
–	–	–	–	3333	–	3312	–
–	–	–	–	3337	–	3317	–
3632	3649	3608	3647	3607	3412	3607	3447	ν OH
3589	3536	–	–	–	–	–	–	ν NH

Figure 2. The effect of pH on the liquid–liquid extraction of Fe²⁺.

Figure 3. The effect of ligands concentration on the liquid–liquid extraction of Fe²⁺.

Figure 4. The effect of ligands concentration on the liquid–liquid extraction of Pb²⁺.

Figure 5. log D vs. log [L] for the extraction of Fe²⁺ using L1–L4.

Figure 6. log D vs. log [L] for the extraction of Fe²⁺ using L2–L4.

Figure 7. Shapes of MOs frontiers of L1–L4obtained by TD-DFT (B3LYP/6-31G(d, p)).

Figure 8. Correlation graphic of the calculated and experimental frequencies of L1–L4.