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Chelating behaviour of 4-[N-(3:4-methylene dioxy benzylidene) amino] antipyrine semicarbazone towards uranyl ion.


4-acyl pyrazolones (Jensen 1959, Zolotov et al 1966, 1968, Karalova and Pyzhova 1968, Monseev and Monokhov 1968) have been shown to be good extraction reagents for metals in acidic solutions. Akama et al (1985,1986) in their systematic study of alkyl substituted-4-acyl derivatives of 3-methyl-1-phenyl pyrazol-5-one showed that due to its slightly lower Pka-values, the 4-benzoyl derivative proved to be more efficient in the extraction of metal ions than the other 4-acyl pyrazolones studied (Akama et al 1985, Akama et al 1986).

This report describes the preparation and characterization of uranyl complexes of 4-[N-(3:4-methylene dioxy benzylidene) amino antipyrine semicarbazone, on the basis of their IR, magnetic moment and molar conductance measurement.



4-Aminoantipyrine (Fluka) 3:4-methylene dioxy benzaldehyde and semicarbazide hydrochloride (all B.D.H./ C.D.H.) were obtained commercial and purified before use (Perrin et al 1966).

(i) 4-Amino antipyrine semicarbazone

It was synthesised by the method described earlier (Siddalingaiah and Veerabhadra Swang 2000, Bullock and Hand 1956) (11.15 gm; 0.1 mol) of semicarbazide hydrochloride and 15 gm of sodium acetate was dissolved in 50 ml distilled water and mixed with 4-amino antipyrine (26 gm, 0.1 mol) was heated for about two hours on water bath. On concentration and cooling colourless mass separated out, filltered washed with ethanol and crystallized with ether. Yield 68%; m.p.-134[degrees]C ([C.sub.12][H.sub.16][N.sub.6]O)

(ii) 4-[N-(3:4-methylene dioxy benzylidene) amino] antipyrine semicarbazone:

4-amino antipyrine semicarbazone (26 g; 0.1 mol) and 3:4-methylene dioxy benzaldehyde (15 ml, 0.1 mol) were heated together on water bath for two hour. Subsequently, the contents were cooled slowly with constant stirring. A white solid separated out which was filtered off and dried at 100[degrees]C. The crude 4-[N-(3:4-methylene dioxy benzylidene) amino] antipyrine semicarbazone was recrystallised from ethanol as white crystalline solid, m.p. 165[degrees]C, yield 62% ([C.sub.20][H.sub.20][N.sub.6][O.sub.3]).

Praparation of metal complexes: The uranyl salt (5 m mol) was dissolved in aqueous ethanol. This was added slowly with stirring to a solution of ligand (10 m mol) in 25 ml ethanol. The reaction stoichiometry of metal-ligand mole ratio was 1:2. Whole content was refluxed for two hours on water bath. Yellow coloured precipitate separated, filtered and washed with aqueous ethanol (1:1) solution. The products were recrystallised from aqueous ethanol, dried in air and stored over fused Ca[Cl.sub.2] in a desiccator.

Carbon, hydrogen and nitrogen were determined by the microanalytical methods. Magnetic moments at 25[degrees]C were determined using a Johnson Matthey magnetic susceptibility balance and Hg[CO[(SCN).sub.4]] as calibrant. IR-spectra were measured, using KBr disc on a matson 5000 FTIR-spectrometer molar conductivities in nitrobenzene were measured on Toshniwal conductivity bridge.


The analytical data of the complexes are in agreement with their molecular formulae, as shown in table. The molar conductivities in nitrobenzene of 25[degrees]C suggest their non-electrolytic nature (Table-1).

The complexes are anhydrous which is evident from the analytical, infrared and thermal studies. All the complexes are quite stable and can be stored for long periods without loss in mass. The dioxouranium(VI) complexes U[O.sub.2][X.sub.2.n]([C.sub.20] [H.sub.20][N.sub.6][O.sub.3]) (X= [Cl.sup.-], [Br.sup.-], [I.sup.-], [NCS.sup.-], n=2, X=N[O.sup.3.sup.-] or C[H.sub.3]CO[O.sup.-], n=1) are all essentiality non-electrolytes in nitrobenzene. The conductivity of the halo complexes is in general agreement with the stability of the U-halogen bond found earlier (Jha and Saxena 1978). The conductance values for the perchlorato complexes [U[O.sub.2]([C.sub.20][H.sub.20][N.sub.6][O.sub.3])][(Cl[O.sub.4]).sub.2] suggest ionic perchlorate groups, the presence of which was further confirmed by the infrared spectra. The molecular weights of the complexes as determined by Rasta method using diphenyl as solvent, indicate monomeric structures for the complexes and dimeric structures for other complexes, but do not favour the polymeric structure. Uranyl complexes are diamagnetic (Beamish and Page 1956, Arora and Rao 1981) in nature, since ground states of dioxouranium salts contain one impaired electrons, the compounds are therefore weakly diamagnetic as observed by other (Roeek 2002, Evans and Lin 2002, Gokel and Mukopadhyay 2001).

In the present complexes the hydrazinic nitrogen of-N[H.sub.2] (1622-1630 [cm.sup.-1]) is absent in the infrared absorption spectra of ligand ([C.sub.20][H.sub.20][N.sub.6][O.sub.3]) showing the condensation of amino antipyrine with different aldehydes (Hedewy et al 1986). It has been noticed that the amide-II band get shifted towards the lower energy side compared to that of the semicarbazone. This effect is due to shift of the electron density from the hydrazinic nitrogen (Masond et al 1987).

The shift in the band positions in the IR-spectra of the complexes of these metal ions have been found to be similar. The following are the general observations in their spectra.

(i) The v(NH) of the ligand at 3200 [cm.sup.-1] remain at the same position in all the complexes suggesting the non involvement of v(NH) proton in the complexes.

(ii) The amide band-I (vC=O) (1700-1680 [cm.sup.-1]) in the complexes was shifted to the lower wave numbers ([DELTA]v-25-30) due to bond formation (Masond and El-Dessonky 1987).

(iii) The amide-II band in the free ligands has been appeared 1560 [cm.sup.-1]. In all the complexes this band is also shifted towards lower wave number by about 25-30 [cm.sup.-1]. This observation suggest coordination through the carbonyl oxygen atom (Masond et al 1990). The strong band ca. 1600 [cm.sup.-1] in these semicarbazones apparently has a large contribution from the v(C=N) mode of semicarbazone moiety (Masond et al 1998). This has been observed as a blue shift in the position of the v(C=N) band in all complexes as compared to the free ligands.

(iv) The free schiff bases exhibit in the IR-spectra a strong band at 1615-1625 [cm.sup.-1] which is assigned to the v(C=N) mode. This band shifts to lower energy side by 5-30 [cm.sup.-1] in the complexes indicating coordination of nitrogen to the metal ion (Chaudhary et al 2001, McCollum et al 1994, Bush and Alcock 1994).

A single peack is observed in the region 3225-3239 [cm.sup.-1] which reveal the presence of v(NH) of amide group. In addition the appearance of four bands mainly in the regions 1670-1681, 1505-1521 and 1238-1254 [cm.sup.-1] assigned to amide-I, amide-II, and amide-III vibrations, respectively (Pandey et al 1987). Further suggest the formation of proposed macrocyclic frame work. The presence of aromatic (C-N) band in the complexes appeared in the region 831-847 [cm.sup.-1]. Aromatic ring stretch (C-C) (Silverstein et al 1981) appeared at 1645, 1528 and 1451 [cm.sup.-1].

Uranyl complexes shows (Belwal and Singh 1997, Day et al 2000) strong IR-band at 925 [cm.sup.-1] which may be assigned to [](U[O.sub.2]) of the trans (O=U=O) moiety (Griffith and Mostafa 1992). The observations of new bands near (450-470), 395 and 265 [cm.sup.-1] in the complexes may (Hingorani et al 1994) probably be assigned to v(M-O), v(M-N) (Bansal et al 1991) and v(M-Cl) (Ferraro 1971) respectively.

Thiocyanate complex shows an additional band at 2100 [cm.sup.-1] indicating the presence of N-bonded (SCN) group (Clarke and Williams 1966, Devis et al 1970). Bands at 1535 and 1320 [cm.sup.-1] are observed in acetato complexes suggesting a unidentate mode of coordination of acetate to uranyl ion (Nakamoto 1978). Bands at 1000, 1305 and 1400 [cm.sup.-1] are assigned to the coordinated nitrate group. The occurrence of two strong bands ca (1070 [cm.sup.-1] and 620 [cm.sup.-1] in the spectra of the perchlorate complexes attributed to [v.sub.3]- and [b.sub.4]-vibratiions of ionic perchlorate suggests the presence of perchlorate group out side the coordination sphere in the complex (Sarda et al 1988).

Pyrolysis results of U[O.sub.2](VI) complexes of 4-[N-(3:4-methylene dioxy benzylidene) amino] antipyrine semicarbazone ([C.sub.20][H.sub.20][N.sub.6][O.sub.3]) indicate that water molecule does not present in the complexes. All the complexes behave similarly, and display the decomposition of the complexes at 220[degrees]C and completed at 480[degrees]C. The break in the curves in the region 320-340[degrees]C correspond to loss of one molecule of ligand at high temperature another ligand molecule detached from the complex and finally form [U.sub.3][O.sub.8] around 630[degrees]C.

Based on infrared spectroscopy, conductivity measurements, molecular weight determination and magnetic studies, the ligand behave as tridentate, having azomethine nitrogen, imine nitrogen and amido oxygen as the coordinating sites, with the molecular formulae [U[O.sub.2][([C.sub.20][H.sub.20][Ns.ub.6][O.sub.3]).sub.2][X.sub.2]] [X=Cl, Br or NCS) (CN=10); [U[O.sub.2][([C.sub.20][H.sub.20][N.sub.6][O.sub.3]).sub.2]] [(Cl[O.sub.4]).sub.2] (CN=8), [U[O.sub.2]([C.sub.20][H.sub.20][N.sub.6] [O.sub.3])[(NCS).sub.2]] (CN=9) and [U[O.sub.2]([C.sub.20][H.sub.20] [N.sub.6][O.sub.3])[(C[H.sub.3]COO).sub.2]] (CN=9).


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Unnati Vishnoi

Chemistry Deptt., K.L.D.A.V. (P.G.) College, Roorkee (Uttranchal), India

Correspondence Address: Dr. Unnati Vishnoi, P-3/19, Canal Colony, P.O. Gurukul Kangri Singh Dwar, Hardwar-249404, India
Table 1: Analytical, Conductivity and molecular weight date of
U[O.sub.2] (VI) complexes of 4-[N-3:4-methylene dioxy benzylidene)
amino] antipyrine semicarbazone ([C.sub.20][H.sub.20][N.sub.6]

S. Complex Yield (%) Colour

1. U[O.sub.2][Cl.sub.2].2 60 Yellow

2. U[O.sub.2][Br.sub.2].2 68 Dark Yellow

3. U[O.sub.2][I.sub.2].2 65 Brownish Yellow

4. U[O.sub.2] 70 Yellow

5. U[O.sub.2] 60 Yellow

6. U[O.sub.2] 65 Yellow

7. U[O.sub.2] 60 Yellow

Complex m.p. Analysis; Found
 ([degrees]C) (Calcd.) %

U[O.sub.2][Cl.sub.2].2 210 21.05
([C.sub.20][H.sub.20] (21.15)

U[O.sub.2][Br.sub.2].2 206 19.50
([C.sub.20][H.sub.20] (19.60)

U[O.sub.2][I.sub.2].2 204 18.12
([C.sub.20][H.sub.20] (18.19)

U[O.sub.2] 200 20.26
[(NCS).sub.2].2 (20.34)

U[O.sub.2] 180 18.90
[(ClO).sub.4].2 (18.99)

U[O.sub.2] 200 30.20
[(NO).sub.3].2 (30.28)

U[O.sub.2] 202 30.45
[(CH.sub.3COO)].2 (30.51)

Complex Analysis; Found (Calcd.) %
 N Anion C

U[O.sub.2][Cl.sub.2].2 14.88 6.25 42.60
([C.sub.20][H.sub.20] (14.93) (6.31) (42.66)

U[O.sub.2][Br.sub.2].2 13.78 13.12 39.45
([C.sub.20][H.sub.20] (13.83) (13.17) (39.53)

U[O.sub.2][I.sub.2].2 12.76 19.35 36.60
([C.sub.20][H.sub.20] (12.84) (19.41) (36.69)

U[O.sub.2] 16.70 9.85 42.96
[(NCS).sub.2].2 (16.75) (9.91) (43.07)

U[O.sub.2] 13.30 15.80 38.26
[(ClO).sub.4].2 (13.40) (15.88) (38.30)

U[O.sub.2] 14.16 - 30.48
[(NO).sub.3].2 (14.24) (30.53)

U[O.sub.2] 10.70 15.00 36.86
[(CH.sub.3COO)].2 (10.76) (15.12) (36.92)

Complex M.W. [OMEGA]M
 Exp. ([ohm.sup.-1]
 (Theor.) [cm.sup.2]

U[O.sub.2][Cl.sub.2].2 1120.0 4.20
([C.sub.20][H.sub.20] (1125.03)

U[O.sub.2][Br.sub.2].2 1208 4.60
([C.sub.20][H.sub.20] (1214.03)

U[O.sub.2][I.sub.2].2 1300 4.80
([C.sub.20][H.sub.20] (1308.03)

U[O.sub.2] 1165 4.20
[(NCS).sub.2].2 (1170.03)

U[O.sub.2] 418 50.50
[(ClO).sub.4].2 (1253.03)

U[O.sub.2] 780 3.21
[(NO).sub.3].2 (726.03)

U[O.sub.2] 774.0 4.12
[(CH.sub.3COO)].2 (780.03)

Table 2: Infrared absorption frequencies ([cm.sup.-1]) of U[O.sub.2]
(VI) complexes of 4-[N-(3:4-methylene dioxy benzylidene) amino]
antipyrine semicarbaone ([C.sub.20][H.sub.20][N.sub.6][O.sub.3])

Assignments ([C.sub.20] U[O.sub.2]
 [H.sub.20] [Cl.sub.2]-
 [N.sub.6] 2([C.sub.20]
 [O.sub.3]) [H.sub.20]

v(C=N) 1620s 1580s

v(C=N) 1600s 1622s

v(C=O)I 1700s 1650s

v(C=O)II 1565m 1630s

v(C=O)III 1350m 1530m

v(U-O)/ - 450m
v(U-N)/ 390w

Assignments U[O.sub.2] U[O.sub.2]
 [Br.sub.2]- [I.sub.2]-
 2([C.sub.20] 2([C.sub.20]
 [H.sub.20] [H.sub.20]
 [N.sub.6] [N.sub.6]
 [O.sub.3]) [O.sub.3])

v(C=N) 1580s 1590s

v(C=N) 1620s 1625s

v(C=O)I 1640s 1645s

v(C=O)II 1530m 1625m

v(C=O)III 1335m 1330m

v(U-O)/ 455m 465m
v(U-N)/ 390w 395w

Assignments U[O.sub.2] U[O.sub.2]
 [(NCS).sub.2]- [(ClO.sub.4]).sub.2]-
 2([C.sub.20] 2([C.sub.20]
 [H.sub.20] [H.sub.20]
 [N.sub.6] [N.sub.6]
 [O.sub.3]) [O.sub.3])

v(C=N) 1580s 1575s

v(C=N) 1620s 1670s

v(C=O)I 1650s 1640s

v(C=O)II 1530m 1530m

v(C=O)III 1335m 1320m

v(U-O)/ 460m 465m
v(U-N)/ 395w 385w

Assignments U[O.sub.2] U[O.sub.2]
 [(NO.sub.3]).sub.2]- [(C[H.sub.3]
 2([C.sub.20] COO).sub.2]
 [H.sub.20] 2([C.sub.20]
 [N.sub.6] [H.sub.20]
 [O.sub.3]) [N.sub.6]

v(C=N) 1580s 1580s

v(C=N) 1620s 1620s

v(C=O)I 1645s 1640s

v(C=O)II 1530m 1530m

v(C=O)III 1332m 1325m

v(U-O)/ 455m 450m
v(U-N)/ 385w 380w
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Author:Vishnoi, Unnati
Publication:Bulletin of Pure & Applied Sciences-Chemistry
Date:Jul 1, 2006
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