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Composition, stability and structure of the vanadium(IV)-alizarin red s complex
SHORT
400
Composition, complex
stability
and structure
COMMUNICATIONS
of the vanadium(W)-alizarin
red S
The chromogenic properties of alizarin red S (Colour Index Mordant Red 3, 58005 ; sodium r,2-dihydroxyanthraquinone-3-sulphonatc) have often been utilizparticularly in spectrophotometric analysis. The zirconium-alizarin red S chclate received particular attention (see, e.g., rcfs. I and z) because of its importance in determination of fluoride. The colour changes of alizarin red S with change in PH have also been thoroughly studied3s’i. A new chelatc of vanadium(IV) with alizarin red S and a detailed investigation of the nature, composition and stability of the chelatc are described in the present paper. C.I. ed, has the
Reagents Solutions of sodium alizarin-3-sulphonate and vanadyl sulphate (A-R., R.D.H.) were prepared in twice-distilled water. All other reagents used were of analytical grade. For adjustment of PH, dilute solutions of sodium hydroxide and sulphuric acid were used.
Spectrophotomctric measurements were made with a Unicam SP 500 spcctrophotometer and IO-mm glass cells. PH measurements were carried out with a L and N direct reading PH meter with glass and calomel electrodes. Cololrr of the chelate Colour formation w&asfound to be instantaneous at room temperature and no effect was observed when the order of the mixing of the reagents w
Nature
and stoichiometry
of the &elate In order to determine the nature of the vanadium(IV) complex which involves the mesomeric forms of the dye obtained in partially neutralized media, the method of VOSBURGH AND COOPERS was adopted. The results are shown in Fig. I. The maximum wavelength for the chelate shifts to 4go m,u and there is a clear indication of the formation of only one complex under the conditions used. To investigate the stoichiometric ratio of vanadium(IV) to alizarin red S in the chelate, JOB'S method0 was applied at PH 4.0 and 490 n_ltc.The results clearly showed '.LQW Asal.
Claim. Ada,
35 (1gf3.5)400-403
,> ..Y’
SHORT COMMUNICATIONS
Wavelength Fig.
I. Absorption
of vnnadium( IV) -aliznrin reel S chclntc. Katurc of the complex formccl: pn +.o; clcvclopmcnt time 30 min; tcmpcraturc 25”. Find conccntrntion
spcctrn
Total volume 50 ml; Al * 10’1. __-VO.SO4 A liz. A 0.00 B 2.0 c 1.0 D 0.5 E 0.33
cm@
Rnlio V( II’) : .4 liz.
I.0
0
I.0 I.0 I.0 I.0
1.0: 1.0 1.0:2.0 1 :3.0
: I.0
x.0:0.5
b
0.7
0.6
VOSO,
(ml)
IFig. 2. (a) Dctcrmination of the composition of the chclatc by the mcthocl of continuous variation at 4go m,u; p~r = 4.0. Curve A. 5 - IO-J M; Curve 13, 4.0 . IO-J M; Curve C, 3.33 . x0-4 M. (b) Dctcrrnination of the conlposition of the chclatc by the mcthocl of continuous variation at 4go m,u; per = 4.0. Curve A, 5.0 - IO-J AT; Curve B, 2.50. x0-4 &I.
Asal.
Chirn. Acta, 35 (rgGG) 400-403
SHORT COMMUNICATIONS
402
the formation of a 1:2 vanadium(IV)-alizaiin red S &elate when the concentrations of the vanaclium(IV) and alizarin red S solutions were equal (Fig. 2a). The results shown in Fig. 2b were obtained for concentration ratios of aliznrin red S to vanadyl sulphate of 0.5 (curve A) and 2.0 (curve B). The stoichiomctric composition of the chclatc was also corroborated by the mole ratio mcthod7 (Fig. 3) and the slope ratio method8 (Fig. 4). The effect of IIH on the stability of the chelatc was recorded by measuring the absorbance of mixtures containing vanatlyl sulphatc and alizarin red S in a I : 2 ratio at diffcrcnt wavelengths. The complex WE shown to be stable in the 1)~ range 3.5-5.5.
0.6
0.5
0.4
.O
0.3
0.2
0.1
2
0
Mole
ratlo
4 V02+/Allr.
e
I
8
0
&iable
Zxnponent
e
(ml)
Fig. 3. IDctcrmination of the composition by the molt ratio mcthocl at 400 m/r; 1’11= conccntrntion of nliznrin reel S: Curve A, 2.0 * 10-4 M; Curve 13, 1.33 . 10-4 M.
Et
1c
4.0. Final
Fig. 4. Dotcrminntion of the composition by t?w slope ratio mcthocl. Curve A, 490 mp; Curve I3, 500 nip (VOSOd varying); Curve C, 490 mp; Curve I), 500 rnp (hliz. varying). 10 ml cxccss coniponcnt (G.GG - 10-4 M) -t_ x nil vrrrinblc component (2.22 * x0-4 M) + (Is s) ml of water. Evduation of th stnbil~ty constant The stability constant of the chelate was calculated by 3 clifferent the values obtained (Table I) arc in close agreement with each othci . Possibh
methods;
stvuctwe of t?u chbate In a reaction with alizarin red S, the metal ion may be attachccl to the two phcnolic oxygens, or to the quinoid oxygen ancl the Lu-phenolic oxygen. TABLE STAUILITY
J CONSTANTS
DEY AND MUKEIERJI~ Continuous variation Mole ratio
OF
VANADIUM
CllILLhTli
8.6 * 0.4 g,:! St 0.6 8.4 & 0.2
Aural. Cirirn. Acta, 3’5 (xgGG) 400-403
--rr.g f 0.4 -12.7 f 0.G -1X.5 f 0.2
SHORT COIILIUNICATIONS
403
Alizarin red S exists in 3 different structural forms depending on the hydrogen ion concentration. LARSES AND HIROZAWA~ have explained the half neutralisation of alizarin red S at PH 8.3 and subsequent shift to 525 rnp on the basis of the removal of the /?-hydrogen which enhances the resonance in the molecule as follows :
0-
0
0'
A practically identical shift in the ilma would be observed if the chelation of the metal ion with alizarin red S were due to the quinoid and n-phcnolic oxygens when a resonance similar to the above would be possible. If the metal ion were attached by the 2 phenolic oxygens, resonance would not be possible, and the shift in the &,, would probably be much smaller. The vanadium(IV) -alizarin red S chclate investigated at 13~ 4.0 showed maximum absorbance at 4go rnp which is below the resonance level ; the spectral evidence thus points to chelation through the two phcnolic oxygens and not through the quinoid and Lu-phenolic oxygens. Further, chelation of vanadium(IV) through the phcnolic oxygens would yield anionic complexes, and this w
S.
1’. SANYAL P. MUSHRAN
I E. M. LARSEN AND ST. T. HIROZAWA, J. Inorg. & Ntccl. Ckmn., 3 (1956) 198. z G. PARISSAKIS AND J_ KONTOYANNAICOS, Atznl. Chim. A&n, 29 (1963) 220. 3 Y. DORTA-SCHAHPPI, H. HURZIXZR AND W. D. TRIIADWPLL. llclv. Claim. Acfa, 34 (1951) 797. 4 D. V. N. SARMh AND B. S. V. R. RAO, Awnl. Ckirtt. ilctn, 13 (1955) 142. 5 W. C. VOSBURGII AND G. R. COOPISH, J. Am. CIJEUL. Sot., 63 (194’) 437: 4 (x94?-) 1630. 6 P. Jorg, Compt. Rtwd., 180 (1925) 928; Awr. C/ah. (Paris), (IO) 9 (1928) 113. 7 J. H. Yoo AND A. I,. JONES, rnd. Btrg. Clrem., ArJal. Ed.. 16 (1944) xx I. 8 A. E. HARVEY AND D. L. MANNING, J. Am. Chem. Sot., 72 (1950) 4488; 74 (1952) 4744. 9 A. K. Dou AND A. IC. MIJKHERJI, J. Inovg. & NJ&. Cirem., 6 (1958) 314.
(Received
October
rgth, 1965) rt IJd. c!Ji?Pl . .Icta, 35 (I gGG) 400-403
400
Composition, complex
stability
and structure
COMMUNICATIONS
of the vanadium(W)-alizarin
red S
The chromogenic properties of alizarin red S (Colour Index Mordant Red 3, 58005 ; sodium r,2-dihydroxyanthraquinone-3-sulphonatc) have often been utilizparticularly in spectrophotometric analysis. The zirconium-alizarin red S chclate received particular attention (see, e.g., rcfs. I and z) because of its importance in determination of fluoride. The colour changes of alizarin red S with change in PH have also been thoroughly studied3s’i. A new chelatc of vanadium(IV) with alizarin red S and a detailed investigation of the nature, composition and stability of the chelatc are described in the present paper. C.I. ed, has the
Reagents Solutions of sodium alizarin-3-sulphonate and vanadyl sulphate (A-R., R.D.H.) were prepared in twice-distilled water. All other reagents used were of analytical grade. For adjustment of PH, dilute solutions of sodium hydroxide and sulphuric acid were used.
Spectrophotomctric measurements were made with a Unicam SP 500 spcctrophotometer and IO-mm glass cells. PH measurements were carried out with a L and N direct reading PH meter with glass and calomel electrodes. Cololrr of the chelate Colour formation w&asfound to be instantaneous at room temperature and no effect was observed when the order of the mixing of the reagents w
Nature
and stoichiometry
of the &elate In order to determine the nature of the vanadium(IV) complex which involves the mesomeric forms of the dye obtained in partially neutralized media, the method of VOSBURGH AND COOPERS was adopted. The results are shown in Fig. I. The maximum wavelength for the chelate shifts to 4go m,u and there is a clear indication of the formation of only one complex under the conditions used. To investigate the stoichiometric ratio of vanadium(IV) to alizarin red S in the chelate, JOB'S method0 was applied at PH 4.0 and 490 n_ltc.The results clearly showed '.LQW Asal.
Claim. Ada,
35 (1gf3.5)400-403
,> ..Y’
SHORT COMMUNICATIONS
Wavelength Fig.
I. Absorption
of vnnadium( IV) -aliznrin reel S chclntc. Katurc of the complex formccl: pn +.o; clcvclopmcnt time 30 min; tcmpcraturc 25”. Find conccntrntion
spcctrn
Total volume 50 ml; Al * 10’1. __-VO.SO4 A liz. A 0.00 B 2.0 c 1.0 D 0.5 E 0.33
cm@
Rnlio V( II’) : .4 liz.
I.0
0
I.0 I.0 I.0 I.0
1.0: 1.0 1.0:2.0 1 :3.0
: I.0
x.0:0.5
b
0.7
0.6
VOSO,
(ml)
IFig. 2. (a) Dctcrmination of the composition of the chclatc by the mcthocl of continuous variation at 4go m,u; p~r = 4.0. Curve A. 5 - IO-J M; Curve 13, 4.0 . IO-J M; Curve C, 3.33 . x0-4 M. (b) Dctcrrnination of the conlposition of the chclatc by the mcthocl of continuous variation at 4go m,u; per = 4.0. Curve A, 5.0 - IO-J AT; Curve B, 2.50. x0-4 &I.
Asal.
Chirn. Acta, 35 (rgGG) 400-403
SHORT COMMUNICATIONS
402
the formation of a 1:2 vanadium(IV)-alizaiin red S &elate when the concentrations of the vanaclium(IV) and alizarin red S solutions were equal (Fig. 2a). The results shown in Fig. 2b were obtained for concentration ratios of aliznrin red S to vanadyl sulphate of 0.5 (curve A) and 2.0 (curve B). The stoichiomctric composition of the chclatc was also corroborated by the mole ratio mcthod7 (Fig. 3) and the slope ratio method8 (Fig. 4). The effect of IIH on the stability of the chelatc was recorded by measuring the absorbance of mixtures containing vanatlyl sulphatc and alizarin red S in a I : 2 ratio at diffcrcnt wavelengths. The complex WE shown to be stable in the 1)~ range 3.5-5.5.
0.6
0.5
0.4
.O
0.3
0.2
0.1
2
0
Mole
ratlo
4 V02+/Allr.
e
I
8
0
&iable
Zxnponent
e
(ml)
Fig. 3. IDctcrmination of the composition by the molt ratio mcthocl at 400 m/r; 1’11= conccntrntion of nliznrin reel S: Curve A, 2.0 * 10-4 M; Curve 13, 1.33 . 10-4 M.
Et
1c
4.0. Final
Fig. 4. Dotcrminntion of the composition by t?w slope ratio mcthocl. Curve A, 490 mp; Curve I3, 500 nip (VOSOd varying); Curve C, 490 mp; Curve I), 500 rnp (hliz. varying). 10 ml cxccss coniponcnt (G.GG - 10-4 M) -t_ x nil vrrrinblc component (2.22 * x0-4 M) + (Is s) ml of water. Evduation of th stnbil~ty constant The stability constant of the chelate was calculated by 3 clifferent the values obtained (Table I) arc in close agreement with each othci . Possibh
methods;
stvuctwe of t?u chbate In a reaction with alizarin red S, the metal ion may be attachccl to the two phcnolic oxygens, or to the quinoid oxygen ancl the Lu-phenolic oxygen. TABLE STAUILITY
J CONSTANTS
DEY AND MUKEIERJI~ Continuous variation Mole ratio
OF
VANADIUM
CllILLhTli
8.6 * 0.4 g,:! St 0.6 8.4 & 0.2
Aural. Cirirn. Acta, 3’5 (xgGG) 400-403
--rr.g f 0.4 -12.7 f 0.G -1X.5 f 0.2
SHORT COIILIUNICATIONS
403
Alizarin red S exists in 3 different structural forms depending on the hydrogen ion concentration. LARSES AND HIROZAWA~ have explained the half neutralisation of alizarin red S at PH 8.3 and subsequent shift to 525 rnp on the basis of the removal of the /?-hydrogen which enhances the resonance in the molecule as follows :
0-
0
0'
A practically identical shift in the ilma would be observed if the chelation of the metal ion with alizarin red S were due to the quinoid and n-phcnolic oxygens when a resonance similar to the above would be possible. If the metal ion were attached by the 2 phenolic oxygens, resonance would not be possible, and the shift in the &,, would probably be much smaller. The vanadium(IV) -alizarin red S chclate investigated at 13~ 4.0 showed maximum absorbance at 4go rnp which is below the resonance level ; the spectral evidence thus points to chelation through the two phcnolic oxygens and not through the quinoid and Lu-phenolic oxygens. Further, chelation of vanadium(IV) through the phcnolic oxygens would yield anionic complexes, and this w
S.
1’. SANYAL P. MUSHRAN
I E. M. LARSEN AND ST. T. HIROZAWA, J. Inorg. & Ntccl. Ckmn., 3 (1956) 198. z G. PARISSAKIS AND J_ KONTOYANNAICOS, Atznl. Chim. A&n, 29 (1963) 220. 3 Y. DORTA-SCHAHPPI, H. HURZIXZR AND W. D. TRIIADWPLL. llclv. Claim. Acfa, 34 (1951) 797. 4 D. V. N. SARMh AND B. S. V. R. RAO, Awnl. Ckirtt. ilctn, 13 (1955) 142. 5 W. C. VOSBURGII AND G. R. COOPISH, J. Am. CIJEUL. Sot., 63 (194’) 437: 4 (x94?-) 1630. 6 P. Jorg, Compt. Rtwd., 180 (1925) 928; Awr. C/ah. (Paris), (IO) 9 (1928) 113. 7 J. H. Yoo AND A. I,. JONES, rnd. Btrg. Clrem., ArJal. Ed.. 16 (1944) xx I. 8 A. E. HARVEY AND D. L. MANNING, J. Am. Chem. Sot., 72 (1950) 4488; 74 (1952) 4744. 9 A. K. Dou AND A. IC. MIJKHERJI, J. Inovg. & NJ&. Cirem., 6 (1958) 314.
(Received
October
rgth, 1965) rt IJd. c!Ji?Pl . .Icta, 35 (I gGG) 400-403