Dithiocarbamate ligands as heavy metal expectorants from aqueous solutions

Figures & data

Figure 1. Resonance stabilization of the dithiocarbamate anions (a-c) and thiouride (d) tautomer.

Scheme 1. Synthetic route of ligands synthesis K₂L¹ (1b), K₂L² (2b).

Figure 2. ¹³C NMR spectral representation of ligand K₂L¹ in deuterium oxide (D₂O).

Figure 3. ¹HNMR spectral representation of ligand K₂L² in deuterium oxide (D₂O).

Figure 4. ¹³C NMR spectral representation of ligand K₂L² in deuterium oxide (D₂O).

Table 1. Comparison of infrared spectral details of ligands and their complexes with the literature.

	IR Band (cm^−1)
Compound	νOH (H2O)	νNH (NH-CO)	νCH -CH2-	νC = O (N-C = O)	νC-O (N = C-O)	νC-N (N = C-SS)	νCS2asymm (C = S)	νC-Ssymm (C-SS)	ν(N-N)	νM-S/K	Ref.
K2L^1-2	–	3401–3226b*	–	1627s*	1596sh*	1425vs*	1112sh*	994m*	930w*
	–	3333b**	2975w**	1650w**	1551sh**	1456sh**	1042**	950**	978s**	420**
Fe2(L^1-2)2	–	–	–	1620vs*	1577sh*	1472sh*	–	993*	877*	396*, 345*
	–	3256**	2926**	1658s**	1572**	1461**	–	999w**	867**	346**
CO2(L^1-2)2	–	3275*	–	–	1590b*	1472b*	–	952w*	878w*	400*, 383*
	–	3250**	2917**	1640**	1588**	1470**	–	954**	874**	405**
Ni2(L^1-2)2	–	–	–	1628s*	1598s*	1486w*	–	962*	878m*	395*, 347*
	–	–	2923**	1647**	1545**	1493**	–	996**	783**	342**
Cu2(L^1-2)2	–	3382–3217*	–	1621vs*	1580m*	1477 w*	–	1008*	928*	416*, 391*
	–	3391–3246**	29216*	1640**s	–	1456**	–	997**	9429**	357**
Cd2(L^1-2)2	–	3269*		1645*	–	1450*	–	998*	890*	424*
	–	3267**	2886**	1642**	–	1446**	–	987**	900**	421**
Ag2(L^1-2)2	–	3323*	–	1652sh*	1558m*	1446m*	1048vs*	998m*	806*	338*
	–	3304**	2975**	1640**	1581**	1497**	1053**	1010**	827**	339**
Zn2(L^1-2)2	–	3358–3261*	–	1636*	1541*	1499*	–	962*	948*	350*
	–	3312	–	1659**	–	1456**	–	978**	780**	422**
Pb2(L^1-2)2	–	3262–3170*	–	1630*	1554*	1468*	–	936vs*	855*	418*
	–	3200**	2925**	1630**	1572**	1477**	–	955**	825**	428**
	Literature
[K-(L^2)2(H2O)2]	–	–	–	1735	1463	1002	921	–	–	–	[23]
[Co(L^2)2(H2O)2]H2O	3550	3188	–	1737	1421	921	887	–	–	–
[Cu(L^2)2(H2O)2]	3440	–	–	1737	1421	958	857	–	–	–
[Ni(L^2)2(H2O)2]H2O	3550	–	–	1737	1421	–	–	–	–	–
NH4 DHDC	–	–	–	–	1460	1010		–	–	–	[23]
Zn(DHDC)2	–	–	–	–	1480	985	–	–	–	345
Cd(DHDC)2	–	–	–	–	1480vs	–		–	–	350
[Cu(S2CNC4H10)2]	–	–	–	–	1500.72	–	995.69	–	–	424.16	[25]
[Pb(S2CNC4H10)2]	–	–	–	–	1480.27	–	981.06	–	–	418.16
[Cd(S2CNC4H10)2]	–	–	–	–	1495.70	–	985.96	–	–	427.01
K2[Co(L)2Cl2]H2O	–	–	–	1666	1620	999	1022	–	–	432	[26]
K2[Ni(L)2Cl2]H2O	–	–	–	1681	1616	999	1022	–	–	432
K2[Cu(L)2Cl2]H2O	–	–	–	1681	1616	999	1022	–	–	439
K2[Cd(L)2Cl2]H2O	–	–	–	1701	1620	946	1022	–	–	428

K₂L²; ** ML₂, s = strong, vs = very strong, sh = shoulder, m = medium, w = weak, b = broad.

Scheme 2. The ligand-to-metal ratio in the complex formation of Ligand K₂L¹ (M=Fe, Co, Ni, Cu, Cd, Ag, Zn, and Pb) at various temperatures and pH (1c).

Scheme 3. The ligand-to-metal ratio in the complex formation of Ligand K₂L² (M=Fe, Co, Ni, Cu, Cd, Ag, Zn, and Pb) at various temperatures and pH (2c).

Figure 5. Determination of Ni ration to K₂L¹ ligand.

Figure 6. Determination of Zn ration to K₂L² ligand.

Table 2. Metal removal efficiency of dithiocarbamate ligands (K₂L^1-2) at various pH.

					Removal efficiency (%)
Metal	Initial concentration (ppm)	Concentration in Solution (Mean ± SD) *	Concentration in Solution (Mean ± SD) **	pH	Present Study		Literature	Ref
Fe2(L^1-2)2	10	0.276 ± 0.012	0.225 ± 0.011	1	97.23*	97.75**	–	–
		0.08 ± 0.066	0.071 ± 0.020	2	98.77*	99.29**	40	[27]
		0.119 ± 0.010	0.101 ± 0.020	4	98.3*	98.99**	100
		0.030 ± 0.044	0.023 ± 0.021	7	99.7*	99.77**	87
		0.000 ± 0.011	0.000 ± 0.001	10	100*	100**	–	–
		0.20 ± 0.040	0.080 ± 0.010	10B	98*	99.2**	–	–
		0.26 ± 0.066	0.180 ± 0.066	13	97.7*	98.2**	–	–
		0.0052 ± 0.001	0.0015 ± 0.001**	3.27^#	99.95*	99.98**	–	–
Co2(L^1-2)2	10	1.6 ± 0.022	1.32 ± 0.022	1	84*	86.8**	–	–
		0.091 ± 0.012	0.0631 ± 0.012	2	99.0*	99.3**	36	[27]
		0.044 ± 0.004	0.039 ± 0.004	4	99.56*	99.6**	60
		0.052 ± 0.001	0.032 ± 0.001	7	99.48*	99.68**	80
		0.26 ± 0.007	0.099 ± 0.007	10	98*	99.0**	–	–
		0.36 ± 0.004	0.280 ± 0.002	10B	96.4*	97.2**	–	–
		1.0 ± 0.010	0.089 ± 0.001	13	90*	92.1**	–	–
		0.002 ± 0.010	0.029 ± 0.040	7.10	99.98*	97.05**	–	–
Ni2(L^1-2)2	10	2.4 ± 0.010	2.29 ± 0.021	1	75.4*	77.1**	–	–
		0.344 ± 0.020	0.299 ± 0.020	2	96.56*	97.01**	68	[28]
		0.04 ± 0.036	0.033 ± 0.036	4	99.6*	99.67**	100
		0.8 ± 0.052	0.69 ± 0.002	7	92*	93.1**	100
		1.8 ± 0.071	1.68 ± 0.020	10	82*	83.2**	–	–
		9.5 ± 0.085	9.3 ± 0.005	10B	5*	7**	–	–
		9.8 ± 0.020	9.5 ± 0.020	13	1*	2**	–	–
		0.005 ± 0.065	0.091 ± 0.040	6.78^#	99.9*	99.09**	–	–
Cu2(L^1-2)2	10	0.067 ± 0.002	0.059 ± 0.001	1	99.32*	99.41**	–	–
		0.008 ± 0.002	0.0053 ± 0.001	2	99.92*	99.9**	85	[27]
		0.002 ± 0.006	0.001 ± 0.002	4	99.98*	99.9**	100
		0.001 ± 0.005	0.000 ± 0.002	7	99.99*	100**	99.44	[29]
		0.11 ± 0.050	0.097 ± 0.030	10	98.9*	99.0**	91.36/11	[30]
		0.0017 ± 0.020	0.0008 ± 0.020	10B	99.98*	99.9**	–	–
		0.22 ± 0.031	0.188 ± 0.031	13	97.8*	98.12**	–	–
		0.0002 ± 0.003	0.0004 ± 0.091	2.94^#	99.99*	99.99**	99.45	[31]
Cd2(L^1-2)2	10	2.411 ± 0.032	2.276 ± 0.020	1	75.89*	77.2**	–	–
		0.6 ± 0.026	0.49 ± 0.015	2	94*	95.1**	62	[27]
		0.8 ± 0.037	0.76 ± 0.037	4	92*	92.4**	100
		0.006 ± 0.006	0.000 ± 0.002	7	99.94*	100**	87.20
		0.241 ± 0.017	0.189 ± 0.005	10	97.59*	98.11**	–	–
		0.003 ± 0.014	0.002 ± 0.002	10B	99.97*	99.98**	–	–
		0.005 ± 0.006	0.002 ± 0.001	13	99.95*	99.9**	–	–
		0.002 ± 0.001	0.0025 ± 0.0060	6.3^#	99.98*	99.97**	99.70	[31]
Ag2(L^1-2)2	10	0.00 ± 0.040	0.00 ± 0.020	1	100*	100**	–	–
		0.001 ± 0.036	0.002 ± 0.010	2	99.9*	99.98**	–	–
		0.002 ± 0.072	0.000 ± 0.020	4	99.98*	100**	–	–
		0.00 ± 0.0124	0.00 ± 0.023	7	100*	100**	–	–
		0.000 ± 0.011	0.001 ± 0.001	10	100*	99.99**	–	–
		0.000 ± 0.033	0.000 ± 0.001	10B	100*	100**	–	–
		0.004 ± 0.018	0.002 ± 0.001	13	99.96*	99.8**	–	–
		0.000 ± 0.022	0.000 ± 0.001	7.0^#	100*	100**	–	–
Zn2(L^1-2)2	10	0.022 ± 0.034	0.009 ± 0.013	1	99.78*	99.91**	–	–
		0.017 ± 0.040	0.0097 ± 0.008	2	99.83*	99.91**	28	[27]
		0.000 ± 0.018	0.000 ± 0.0186	4	100*	100**	89
		0.022 ± 0.034	0.0089 ± 0.0346	7	99.78*	99.91**	84.27	[28]
		0.021 ± 0.023	0.019 ± 0.0239	10	99.79*	99.8**	92.36/11	[30]
		0.022 ± 0.022	0.016 ± 0.020	10B	99.78*	99.8**	–	–
		0.021 ± 0.028	0.097 ± 0.006	13	99.79*	99.0**	–	–
		0.01 ± 0.066	0.008 ± 0.001	6.20^#	99.9*	99.9**	98.15	[31]
Pb2(L^1-2)2	10	0.022 ± 0.018	0.092 ± 0.0188	1	99.78*	99.9**	–	–
		0.000 ± 0.032	0.000 ± 0.025	2	100*	100**	82.18	[29]
		0.0000 ± 0.023	0.0000 ± 0.010	4	100*	100**	100	[27]
		0.00 ± 0.046	0.00 ± 0.012	7	100*	100**	98.74	[29]
		0.000 ± 0.051	0.000 ± 0.020	10	100*	100**	–	–
		0.00 ± 0.085	0.00 ± 0.005	10B	100*	100**	–	–
		0.002 ± 0.018	0.001 ± 0.008	13	99.98*	99.9**	–	–
		0.006 ± 0.043	0.047 ± 0.056	4.5^#	99.94*	99.5**	99.05	[31]

^# Corresponding initial pH of metal salts in solution in distilled water at room temperature without adding a buffer or any base or acid for pH adjustment.

*ML¹; **ML² (M = Fe, Co, Ni, Cu, Cd, Ag, Zn, Pb).

Figure 7. Representative IR spectrum of K₂L¹ and its NiL¹ complexes.

Figure 8. Representative IR spectrum of K₂L¹ and itsNiL¹ complexes.

Table 3. Metal removal efficiency of dithiocarbamate ligands (K₂L^1-2) at various temp (°C).

					Removal efficiency (%)
Metal	Initial concentration (ppm)	Concentration in Solution (Mean ± SD) *	Concentration in Solution (Mean ± SD) **	Temp (°C)	Present Study
Fe2(L^1-2)2	10	0.237 ± 0.047	0.272 ± 0.047	60	97.63*	97.28**
		1.09 ± 0.0128	0.925 ± 0.032	80	89.1*	90.75**
Co2(L^1-2)2	10	0.709 ± 0.0937	0.670 ± 0.022	60	92.91*	93.3**
		0.940 ± 0.0321	0.823 ± 0.023	80	90.6*	91.7**
Ni2(L^1-2)2	10	0.484 ± 0.0487	0.470 ± 0.0837	60	95.16*	95.3**
		1.08 ± 0.015	0.96 ± 0.00	80	89.2*	90.4**
Cu2(L^1-2)2	10	0.2 ± 0.000	0.09 ± 0.001	60	98.0*	99.1**
		0.8 ± 0.000	0.7 ± 0.001	80	92*	93**
Cd2(L^1-2)2	10	0.001 ± 0.0187	0.09 ± 0.043	60	99.9*	99.1**
		0.09 ± 0.003	0.083 ± 0.001	80	99*	99**
Ag2(L^1-2)2	10	0.000 ± 0.0351	0.0046 ± 0.013	60	100*	99.9**
		0.221 ± 0.009	0.29 ± 0.003	80	97.7*	92**
Zn2(L^1-2)2	10	0.022 ± 0.0275	0.022 ± 0.0213	60	99.7*	99.7**
		0.29 ± 0.054	0.90 ± 0.0213	80	97.1*	97.1**
Pb2(L^1-2)2	10	0.037 ± 0.4357	0.030 ± 0.0213	60	99.6*	99.7**
		0.25 ± 0.0275	0.20 ± 0.023	80	99.5*	98**

*ML¹; **ML (M = Fe, Co, Ni, Cu, Cd, Ag, Zn, Pb).

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