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Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D -camphor-β-sulfonate
Inorganic Chemistry Communications 4 (2001) 409±412
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Chiral lanthanide(III) complexes of sulphur±nitrogen±oxygen ligand derived from aminothiourea and sodium D -camphor-b-sulfonate B. Wang *, H.-Zh. Ma, Q-Zh. Shi Department of Chemistry, Northwest University, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, 710068, Xi'An, China
Abstract Six new chiral lanthanide complexes derived from sodium D -camphor-b-sulfonate and aminothiourea with Ln La3 ; Pr3 ; Nd3 ; Sm3 ; Eu3 and Gd3 of the type LnL3 have been synthesized and characterized on the bases of their elemental analysis, molar conductance, IR, XPS, CD, electronic spectra, magnetic moments and thermal analysis methods. It was found that NaL acts as an SNO tridentate ligand. The visible spectra of PrIII and SmIII show characteristic f±f transitions and the nephelauxetic parameter b, the bonding parameter b1=2 and covalency parameter d of these transitions has been evaluated. These data indicate the weak involvement of the 4f orbitals in complex formation. A nine-coordinated model has been proposed for these complexes. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Chiral complexes; Schi base; Aminothiourea; Sodium
D -camphor-b-sulfonate
1. Introduction
2.2. Physical measurements
Synthesis of chiral complex as a new area have attracted much attention in the past few years [1], the emphasis of most current studies is on the complexes derived from chirality-controlling chelate (CCC) ligands such as chiral diamine ligands which can be used as anticancer agents [2]. As part of our research we have reported the ternary chiral lanthanide complexes of D -camphor-bsulfonic acid and 1,10-phenanthroline [3,4] but few reported on optical lanthanide Schi base complex. On continuation of our study on chiral complexes of lanthanide [5], we report here the synthesis and characterization of optical Schi base ligand (NaL) derived from sodium D -camphor-b-sulfonate and aminothiourea.
The C, H, N and S contents were microanalysed on a Perkin±Elmer 240C elemental analyzer. Lanthanide contents were determined volumetrically by EDTA titrations using xylenol orange as the indicators [6]. Room temperature magnetic susceptibility measurements were made on solid samples by the Guoy method using HgCo CNS4 as calibrant. Thermal analysis were made under nitrogen between room temperature and 800°C using a thermo¯ex Q-1500D meter. Molar conductance, electronic spectra, IR spectra, XPS and the chiral properties of the complexes were investigated as our early paper [5]. 2.3. Preparation of NaL
2. Experiment 2.1. Materials All chemicals and solvents were analytical grade and used without further puri®cation. Lanthanide perchlorates were made from their oxides and perchloric acid. *
Corresponding author. E-mail address: [email protected] (B. Wang).
In 1,4-dioxane solution 100 cm3 of 0.05 mol (12.6 g) sodium D - camphor-b-sulfonate and 0.05 mol (0.46 g) aminothiourea were added and adjusted pH 5.0 by 1:1HCl solution then re¯uxed for 1 h and concentrated under reduced pressure, a red±orange solid separated by cooled the mixture. The product were recrystallized in EtOH twice, 15.8 g was obtained, yield 60%, m.p. 20 156.5±157.5°C, aD 45±47°. The product gave satisfactory elemental analysis, IR and electronic spectra (Tables 1±3).
1387-7003/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 7 - 7 0 0 3 ( 0 1 ) 0 0 2 2 3 - 4
410
B. Wang et al. / Inorganic Chemistry Communications 4 (2001) 409±412
Table 1 Elemental analysis and physical properties of the complexes Compounds
Found (Calcd.) (%) Ln
C
13.22 (13.21) 13.35 (13.37) 13.64 (13.63) 14.10 (14.13) 14.22 (14.26) 14.66 (14.69)
40.30 (40.26) 37.59 (37.67) 37.64 (37.66) 37.42 (37.42) 37.25 (37.27) 37.25 (37.21) 37.04 (37.03)
NaL LaL3 PrL3 NdL3 SmL3 EuL3 GdL3
l (B.M.) 298 H 5.51 (5.52) 5.14 (5.17) 5.14 (5.16) 5.12 (5.15) 5.13 (5.12) 5.11 (5.11) 5.05 (5.08)
N
S
12.80 (12.81) 11.88 (11.98) 11.93 (11.96) 11.90 (11.92) 11.82 (11.85) 11.87 (11.84) 11.76 (11.78)
19.44 (19.54) 18.24 (18.28) 18.22 (18.25) 18.17 (18.19) 18.05 (18.09) 18.06 (18.06) 17.96 (17.97)
a20 D (°)
KM s cm2 mol 1
K +45±47 dia
+120.5
12.0
3.66
+128.5
10.0
3.42
+124.5
9.0
1.68
+114.5
8.2
3.45
+132.5
9.1
7.68
+122.5
8.2
Table 2 Principal IR bands of the ligand and the complexes cm 1 Compound
mNAH
mC@N
mNAN
mC@S
mas ±SO3 ±
ms ±SO3 ±
Dm±SO3 ±
mLnAN
mLnAS
mLnAO
NaL LaL3 PrL3 NdL3 SmL3 EuL3 GdL3
3369br 3370br 3365br 3371br 3368br 3369br 3370br
1620 1605 1602 1603 1602 1605 1600
1126 1130 1130 1132 1131 1134 1133
852 828 820 821 822 819 820
1175 1205 1207 1208 1200 1206 1198
1050 1051 1052 1050 1049 1051 1046
125 154 155 158 151 155 152
260 263 263 262 265 266
390 394 392 395 389 391
225 224 226 226 224 223
Table 3 Electronic spectra of PrIII and SmIII complexesa Complex PrL3
SmL3
a
kmax cm 1
Assignments
Solution
Solid
16,825 20,615 21,195 22,325 20,675 21,300 23,790 24,410
16,710 20,400 21,070 22,140 20,895 21,375 23,810 24,510
H4 Ð1 D2 Ð 3 P0 Ð 3 P1 Ð 3 P2 6 H5=2 Ð4 I9=2 Ð4 I13=2 Ð 6 P; 4 P9=2 Ð4 F7=2 ; 4 L13=2
Calculated spectral parameter b b1=2
(%)
0.982
0.081
0.040
0.989
0.052
0.52
3
Various spectral parameters were calculated from the solid-state spectra of the complexes only.
2.4. Synthesis of the complexes An absolute EtOH solution 20 cm3 of NaL (0.003 mol, 1.99 g) was added with stirring to an EtOH solution 20 cm3 of the respective lanthanide(III) perchlorate (0.001 mol) and the mixture was re¯uxed on water for 1 h, then cooled to room temperature. The precipitate were separated by ®ltration, washed with cooled EtOH and ®nally dried at 110°C for 1 h, yield 75±85%.
3. Results and discussion Physical properties and analytical data for the trivalent lanthanide complexes are given in Table 1. The
complexes are air stable in water, chloroform, ether, EtOH, acetone, DMSO and dimethylformamide. The molar conductance values in DMSO indicate that the complexes are non-electrolytes in solution [7]. The thermal analysis revealed that all the complexes are anhydrous. 3.1. IR spectra The main IR bands with their tentative assignments are listed in Table 2. The bands in the region 3371± 3365 cm 1 of the free ligand and its complexes are assigned to NH stretching frequencies. The mC@N band of the ligand at 1620 cm 1 was shifted down to 1600± 1605 cm 1 in the complexes indicating participation of
B. Wang et al. / Inorganic Chemistry Communications 4 (2001) 409±412
the azomethine nitrogen. The bands at 1126 cm 1 of the free ligand assigned to mNAN absorption was shifted up to 1130±1134 cm 1 , the fact evidently indicates that the nitrogen atom in azomethine group coordinated to lanthanide ion(III). The decrease of mC@S from 852 cm 1 in free ligand to ca. 820 cm 1 shows the coordination of thiolsulphur atom. Two stretching vibrations of ±SO3 ±, mas ±SO3 ± and ms ±SO3 ± in the spectra of the complexes are observed at 1198±1208 and 1046±1052 cm 1 , but in free ligand the two bands appeared at 1175 and 1050 cm 1 , respectively, the Dm value is ca. 155 cm 1 in the complexes which is greater than that of the ligand Dv 125 cm 1 being consistent with unidentate ± SO3 ± coordination. Several bands at 223±226, 260± 266 and 389±394 cm 1 assigned to mLnAO ; mLnAN and mLnAS , respectively, indicate the coordination of the O, N and S atoms. It is possible to conclude that the ligand is attached to the metal ion at three coordination sites involving one sulfonate oxygen, one thiosulphur [8] and one nitrogen atom in azomethine group and an overall coordination number of nine is achieved in all the complexes. 3.2. Magnetic moments and electronic spectra The magnetic moments of lanthanide complexes (Table 1) show little deviation from the Van Vleck values [9], thereby indicating that 4f-electrons do not participate in bond formation in these complexes. Thus, the magnetic moments of these complexes are within the range predicted and observed in the compounds of the lanthanide ions. The f±f transitions normally show weak perturbations on complexation. Increase in the intensity, shift of the center and splitting of certain bands due to crystal ®eld with respect to those of aquo ions are eects that can be observed on complex formation. The electronic spectra of PrIII and SmIII complexes were recorded in 2 10 3 mol dm 3 DMSO solutions. The spectra of the complexes show a shift of the spectra bands towards lower energy as compared to those of the aquo ions [10] due to the nephelauxetic eect (which is regarded as a measure of covalency). The band shape of hypersensitive
411
transition is similar in both the solid (Nujol) and solution (DMSO) phase, which clearly indicates that the complexes retain the same coordination number. The bonding parameter b1=2 , the covalency parameter d have been calculated [11] and nephelauxetic ratio b and compiled in Table 3. The lower nephelauxetic pa positive bonding parameter b1=2 and Sirameter b, nhas' parameter d indicate some covalent character of the bond between the metal and ligand and the weak involvement of the 4f orbitals in complex formation. 3.3. XPS spectra XPS spectra of the complexes and ligand were recorded in the powder form at room temperature (298 K). The results of the XPS semiquantitative analyses and the ratio of Ln:C:N:O:S is ca. 0.16:5.5:1.5:1.5:1.0 of the complexes are in agreement with the elemental analysis data and given in Table 4. The lanthanide 3d electron binding energy is close to the central atom charge and therefore to its valence [12]. The N1s electron spectra of the complexes are asymmetric and their deconvolution yields three binding energy components with an intensity ratio 1:1:1. The components with the highest BE value, belonging to the azomethine nitrogen, shifted up ca. 1.2±1.6 eV and with the intensity ratio 3:1 relative to that in the ligand indicates that the azomethine nitrogen is coordinated to the metal ion and the three coordinated nitrogen atoms are in a symmetric form or in a chemically identical coordination mode. Two bands of the S2p spectra observed at 165.5 and 162.4 eV for the ligand are shifted to ca. 165.4 and 163.0 eV in the complexes are asymmetric and can be assigned to the sulfur atom of ±SO3± and C@S group, respectively, indicating that the electron density at the sulfur atom in C@S group is less than that of the free ligand. Another information supporting the coordination of the sulfur atom in C@S group is the C1s (C@S) BE value show a little higher in the complexes comparing with that of the free ligand. The O1s electron spectra of the complexes are in an asymmetric form and the BE values are at ca. 532.5 and 530.4 eV related to symmetric band of free ligand at 532.5 eV indicate that two chemical
Table 4 The binding energies (eV) of the ligand and its complexes
a
Compound
C1s (C@S)
N1s (C@N)
O1s
NaL LaL3 PrL3 NdL3 SmL3 EuL3 GdL3
282.4 282.5 282.6 282.8 282.7 282.5 282.6
399.5 400.7 401.2 401.1 400.8 400.4 400.2
532.5 530.6, 530.5, 530.4, 530.1, 530.2, 530.3,
Atomic molar percent.
532.0 532.3 532.1 532.6 532.4 532.5
S2p (C@S)
Ln 3d5=2
Ac%a (Ln/C/N/O/S)
162.4 162.8 163.0 163.1 163.2 163.1 162.9
835.9 933.3 984.5 1084.1 1136.2 1191.4
0.16:5.5:1.5:1.5:1.0 0.17:5.5:1.6:1.5:0.9 0.15:5.6:1.4:1.5:1.1 0.16:5.5:1.4:1.6:1.0 0.15:5.5:1.6:1.5:0.9 0.16:5.6:1.5:1.4:1.0
412
B. Wang et al. / Inorganic Chemistry Communications 4 (2001) 409±412
References
Fig. 1. CD and electronic spectra of LaL3 ; PrL3 M; SmL3 O and NaL .
the
complexes
environment was produced after coordination [13,14], combining with the relative intensity ratio 2:1, it can be deduced that the ±SO3 ± group coordinated with metal ion through oxygen atom in an unidentate form. 3.4. CD spectra To get further insight into the complexation, CD spectra of some complexes LaL3 ; PrL3 ; SmL3 were investigated. The distinct positive Cotton eect of the spectra of the complexes and the ligand (NaL) are observed (Fig. 1). The positive value at ca. 380 nm in these complexes is diagnostic of the preferred conformer with (s)-absolute con®guration is dominant for dichroic absorption similar to a positive eect in the ligand [15]. On the basis of the above discussion a nine-coordinated binding model is suggested for the complexes.
[1] G.M. Luigi, P.I. Francesco, K. Danita, C.W. Hing, O.A. Suusano, A.M. Patrica, N. Giovanni, Inorg. Chem. 37 (1998) 6898. [2] J. Reedijk, J. Chem. Soc. Chem. Commun. (1996) 801. [3] H.S. Dong, H.Z. Ma, B. Wang, S.Y. Yang, Polyhedron 16 (1997) 427. [4] B. Wang, H.Z. Ma, S.Y. Yang, Transition Met. Chem. 20 (1995) 391. [5] B. Wang, H.Z. Ma, Inorg. Chem. Commun. 3 (2000) 243. [6] S.J. Lyle, M.D.M. Rahman, Talanta 10 (1963) 1177. [7] W.J. Geary, Coord. Chem. Rev. 7 (1971) 110. [8] N. Kazuo, Infrared and Raman Spectra of Inorganic and Coordination Compounds, third ed., Wiley, New York, 1978, p. 350. [9] F.A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry, third ed., Wiley, New York, 1972. [10] W.T. Carnall, P.R. Fields, K. Rajnak, J. Chem. Phys. 34 (1961) 4424. [11] D.E. Henric, G.R. Choppin, J. Chem. Phys. 49 (1968) 477. [12] C.D. Wagner, J. Electron Spectrosc. Relat. Phenom. 32 (1983) 99. [13] Y. Niwar, H. Tsuchiya, T. Kobayashi, Inorg. Chem. 13 (1974) 2891. [14] M.V. Zeller, R.G. Hayes, J. Am. Chem. Soc. (1973) 3855. [15] R. Rita, C.S. Manik, S.R. Parag, Transition Met. Chem. 15 (1990) 51.
www.elsevier.com/locate/inoche
Chiral lanthanide(III) complexes of sulphur±nitrogen±oxygen ligand derived from aminothiourea and sodium D -camphor-b-sulfonate B. Wang *, H.-Zh. Ma, Q-Zh. Shi Department of Chemistry, Northwest University, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, 710068, Xi'An, China
Abstract Six new chiral lanthanide complexes derived from sodium D -camphor-b-sulfonate and aminothiourea with Ln La3 ; Pr3 ; Nd3 ; Sm3 ; Eu3 and Gd3 of the type LnL3 have been synthesized and characterized on the bases of their elemental analysis, molar conductance, IR, XPS, CD, electronic spectra, magnetic moments and thermal analysis methods. It was found that NaL acts as an SNO tridentate ligand. The visible spectra of PrIII and SmIII show characteristic f±f transitions and the nephelauxetic parameter b, the bonding parameter b1=2 and covalency parameter d of these transitions has been evaluated. These data indicate the weak involvement of the 4f orbitals in complex formation. A nine-coordinated model has been proposed for these complexes. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Chiral complexes; Schi base; Aminothiourea; Sodium
D -camphor-b-sulfonate
1. Introduction
2.2. Physical measurements
Synthesis of chiral complex as a new area have attracted much attention in the past few years [1], the emphasis of most current studies is on the complexes derived from chirality-controlling chelate (CCC) ligands such as chiral diamine ligands which can be used as anticancer agents [2]. As part of our research we have reported the ternary chiral lanthanide complexes of D -camphor-bsulfonic acid and 1,10-phenanthroline [3,4] but few reported on optical lanthanide Schi base complex. On continuation of our study on chiral complexes of lanthanide [5], we report here the synthesis and characterization of optical Schi base ligand (NaL) derived from sodium D -camphor-b-sulfonate and aminothiourea.
The C, H, N and S contents were microanalysed on a Perkin±Elmer 240C elemental analyzer. Lanthanide contents were determined volumetrically by EDTA titrations using xylenol orange as the indicators [6]. Room temperature magnetic susceptibility measurements were made on solid samples by the Guoy method using HgCo CNS4 as calibrant. Thermal analysis were made under nitrogen between room temperature and 800°C using a thermo¯ex Q-1500D meter. Molar conductance, electronic spectra, IR spectra, XPS and the chiral properties of the complexes were investigated as our early paper [5]. 2.3. Preparation of NaL
2. Experiment 2.1. Materials All chemicals and solvents were analytical grade and used without further puri®cation. Lanthanide perchlorates were made from their oxides and perchloric acid. *
Corresponding author. E-mail address: [email protected] (B. Wang).
In 1,4-dioxane solution 100 cm3 of 0.05 mol (12.6 g) sodium D - camphor-b-sulfonate and 0.05 mol (0.46 g) aminothiourea were added and adjusted pH 5.0 by 1:1HCl solution then re¯uxed for 1 h and concentrated under reduced pressure, a red±orange solid separated by cooled the mixture. The product were recrystallized in EtOH twice, 15.8 g was obtained, yield 60%, m.p. 20 156.5±157.5°C, aD 45±47°. The product gave satisfactory elemental analysis, IR and electronic spectra (Tables 1±3).
1387-7003/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 7 - 7 0 0 3 ( 0 1 ) 0 0 2 2 3 - 4
410
B. Wang et al. / Inorganic Chemistry Communications 4 (2001) 409±412
Table 1 Elemental analysis and physical properties of the complexes Compounds
Found (Calcd.) (%) Ln
C
13.22 (13.21) 13.35 (13.37) 13.64 (13.63) 14.10 (14.13) 14.22 (14.26) 14.66 (14.69)
40.30 (40.26) 37.59 (37.67) 37.64 (37.66) 37.42 (37.42) 37.25 (37.27) 37.25 (37.21) 37.04 (37.03)
NaL LaL3 PrL3 NdL3 SmL3 EuL3 GdL3
l (B.M.) 298 H 5.51 (5.52) 5.14 (5.17) 5.14 (5.16) 5.12 (5.15) 5.13 (5.12) 5.11 (5.11) 5.05 (5.08)
N
S
12.80 (12.81) 11.88 (11.98) 11.93 (11.96) 11.90 (11.92) 11.82 (11.85) 11.87 (11.84) 11.76 (11.78)
19.44 (19.54) 18.24 (18.28) 18.22 (18.25) 18.17 (18.19) 18.05 (18.09) 18.06 (18.06) 17.96 (17.97)
a20 D (°)
KM s cm2 mol 1
K +45±47 dia
+120.5
12.0
3.66
+128.5
10.0
3.42
+124.5
9.0
1.68
+114.5
8.2
3.45
+132.5
9.1
7.68
+122.5
8.2
Table 2 Principal IR bands of the ligand and the complexes cm 1 Compound
mNAH
mC@N
mNAN
mC@S
mas ±SO3 ±
ms ±SO3 ±
Dm±SO3 ±
mLnAN
mLnAS
mLnAO
NaL LaL3 PrL3 NdL3 SmL3 EuL3 GdL3
3369br 3370br 3365br 3371br 3368br 3369br 3370br
1620 1605 1602 1603 1602 1605 1600
1126 1130 1130 1132 1131 1134 1133
852 828 820 821 822 819 820
1175 1205 1207 1208 1200 1206 1198
1050 1051 1052 1050 1049 1051 1046
125 154 155 158 151 155 152
260 263 263 262 265 266
390 394 392 395 389 391
225 224 226 226 224 223
Table 3 Electronic spectra of PrIII and SmIII complexesa Complex PrL3
SmL3
a
kmax cm 1
Assignments
Solution
Solid
16,825 20,615 21,195 22,325 20,675 21,300 23,790 24,410
16,710 20,400 21,070 22,140 20,895 21,375 23,810 24,510
H4 Ð1 D2 Ð 3 P0 Ð 3 P1 Ð 3 P2 6 H5=2 Ð4 I9=2 Ð4 I13=2 Ð 6 P; 4 P9=2 Ð4 F7=2 ; 4 L13=2
Calculated spectral parameter b b1=2
(%)
0.982
0.081
0.040
0.989
0.052
0.52
3
Various spectral parameters were calculated from the solid-state spectra of the complexes only.
2.4. Synthesis of the complexes An absolute EtOH solution 20 cm3 of NaL (0.003 mol, 1.99 g) was added with stirring to an EtOH solution 20 cm3 of the respective lanthanide(III) perchlorate (0.001 mol) and the mixture was re¯uxed on water for 1 h, then cooled to room temperature. The precipitate were separated by ®ltration, washed with cooled EtOH and ®nally dried at 110°C for 1 h, yield 75±85%.
3. Results and discussion Physical properties and analytical data for the trivalent lanthanide complexes are given in Table 1. The
complexes are air stable in water, chloroform, ether, EtOH, acetone, DMSO and dimethylformamide. The molar conductance values in DMSO indicate that the complexes are non-electrolytes in solution [7]. The thermal analysis revealed that all the complexes are anhydrous. 3.1. IR spectra The main IR bands with their tentative assignments are listed in Table 2. The bands in the region 3371± 3365 cm 1 of the free ligand and its complexes are assigned to NH stretching frequencies. The mC@N band of the ligand at 1620 cm 1 was shifted down to 1600± 1605 cm 1 in the complexes indicating participation of
B. Wang et al. / Inorganic Chemistry Communications 4 (2001) 409±412
the azomethine nitrogen. The bands at 1126 cm 1 of the free ligand assigned to mNAN absorption was shifted up to 1130±1134 cm 1 , the fact evidently indicates that the nitrogen atom in azomethine group coordinated to lanthanide ion(III). The decrease of mC@S from 852 cm 1 in free ligand to ca. 820 cm 1 shows the coordination of thiolsulphur atom. Two stretching vibrations of ±SO3 ±, mas ±SO3 ± and ms ±SO3 ± in the spectra of the complexes are observed at 1198±1208 and 1046±1052 cm 1 , but in free ligand the two bands appeared at 1175 and 1050 cm 1 , respectively, the Dm value is ca. 155 cm 1 in the complexes which is greater than that of the ligand Dv 125 cm 1 being consistent with unidentate ± SO3 ± coordination. Several bands at 223±226, 260± 266 and 389±394 cm 1 assigned to mLnAO ; mLnAN and mLnAS , respectively, indicate the coordination of the O, N and S atoms. It is possible to conclude that the ligand is attached to the metal ion at three coordination sites involving one sulfonate oxygen, one thiosulphur [8] and one nitrogen atom in azomethine group and an overall coordination number of nine is achieved in all the complexes. 3.2. Magnetic moments and electronic spectra The magnetic moments of lanthanide complexes (Table 1) show little deviation from the Van Vleck values [9], thereby indicating that 4f-electrons do not participate in bond formation in these complexes. Thus, the magnetic moments of these complexes are within the range predicted and observed in the compounds of the lanthanide ions. The f±f transitions normally show weak perturbations on complexation. Increase in the intensity, shift of the center and splitting of certain bands due to crystal ®eld with respect to those of aquo ions are eects that can be observed on complex formation. The electronic spectra of PrIII and SmIII complexes were recorded in 2 10 3 mol dm 3 DMSO solutions. The spectra of the complexes show a shift of the spectra bands towards lower energy as compared to those of the aquo ions [10] due to the nephelauxetic eect (which is regarded as a measure of covalency). The band shape of hypersensitive
411
transition is similar in both the solid (Nujol) and solution (DMSO) phase, which clearly indicates that the complexes retain the same coordination number. The bonding parameter b1=2 , the covalency parameter d have been calculated [11] and nephelauxetic ratio b and compiled in Table 3. The lower nephelauxetic pa positive bonding parameter b1=2 and Sirameter b, nhas' parameter d indicate some covalent character of the bond between the metal and ligand and the weak involvement of the 4f orbitals in complex formation. 3.3. XPS spectra XPS spectra of the complexes and ligand were recorded in the powder form at room temperature (298 K). The results of the XPS semiquantitative analyses and the ratio of Ln:C:N:O:S is ca. 0.16:5.5:1.5:1.5:1.0 of the complexes are in agreement with the elemental analysis data and given in Table 4. The lanthanide 3d electron binding energy is close to the central atom charge and therefore to its valence [12]. The N1s electron spectra of the complexes are asymmetric and their deconvolution yields three binding energy components with an intensity ratio 1:1:1. The components with the highest BE value, belonging to the azomethine nitrogen, shifted up ca. 1.2±1.6 eV and with the intensity ratio 3:1 relative to that in the ligand indicates that the azomethine nitrogen is coordinated to the metal ion and the three coordinated nitrogen atoms are in a symmetric form or in a chemically identical coordination mode. Two bands of the S2p spectra observed at 165.5 and 162.4 eV for the ligand are shifted to ca. 165.4 and 163.0 eV in the complexes are asymmetric and can be assigned to the sulfur atom of ±SO3± and C@S group, respectively, indicating that the electron density at the sulfur atom in C@S group is less than that of the free ligand. Another information supporting the coordination of the sulfur atom in C@S group is the C1s (C@S) BE value show a little higher in the complexes comparing with that of the free ligand. The O1s electron spectra of the complexes are in an asymmetric form and the BE values are at ca. 532.5 and 530.4 eV related to symmetric band of free ligand at 532.5 eV indicate that two chemical
Table 4 The binding energies (eV) of the ligand and its complexes
a
Compound
C1s (C@S)
N1s (C@N)
O1s
NaL LaL3 PrL3 NdL3 SmL3 EuL3 GdL3
282.4 282.5 282.6 282.8 282.7 282.5 282.6
399.5 400.7 401.2 401.1 400.8 400.4 400.2
532.5 530.6, 530.5, 530.4, 530.1, 530.2, 530.3,
Atomic molar percent.
532.0 532.3 532.1 532.6 532.4 532.5
S2p (C@S)
Ln 3d5=2
Ac%a (Ln/C/N/O/S)
162.4 162.8 163.0 163.1 163.2 163.1 162.9
835.9 933.3 984.5 1084.1 1136.2 1191.4
0.16:5.5:1.5:1.5:1.0 0.17:5.5:1.6:1.5:0.9 0.15:5.6:1.4:1.5:1.1 0.16:5.5:1.4:1.6:1.0 0.15:5.5:1.6:1.5:0.9 0.16:5.6:1.5:1.4:1.0
412
B. Wang et al. / Inorganic Chemistry Communications 4 (2001) 409±412
References
Fig. 1. CD and electronic spectra of LaL3 ; PrL3 M; SmL3 O and NaL .
the
complexes
environment was produced after coordination [13,14], combining with the relative intensity ratio 2:1, it can be deduced that the ±SO3 ± group coordinated with metal ion through oxygen atom in an unidentate form. 3.4. CD spectra To get further insight into the complexation, CD spectra of some complexes LaL3 ; PrL3 ; SmL3 were investigated. The distinct positive Cotton eect of the spectra of the complexes and the ligand (NaL) are observed (Fig. 1). The positive value at ca. 380 nm in these complexes is diagnostic of the preferred conformer with (s)-absolute con®guration is dominant for dichroic absorption similar to a positive eect in the ligand [15]. On the basis of the above discussion a nine-coordinated binding model is suggested for the complexes.
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