Preparation, Spectral Properties and Biological ...

Preparation, Spectral Properties and Biological Activity of Cu(II), Zn(II) and Cd(II) Chelates of 8-Hydroxyquinoline-5-suIfonamides S. A. Ibrahim *, M. A. El-G aham i, R. M. Mahfouz Chem istry D epartm ent, Faculty o f Science, Assiut University, A ssiut, Egypt

and K. A. Farghali B otany D epartm ent, Faculty o f Science, Assiut University, Assiut, Egypt Z. Naturforsch.

44b, 1488—1492 (1989); received June 26/Septem ber 11, 1989

B iological A ctivity, Chelates o f C u(II), Zn(II) and Cd(II), Q uinolinol Sulfonam ides The com plexes o f som e quinolinol sulfonam ides with Cu(II), Z n(II), and C d(II) have been synthesized and formulated as [Cu(L)2(H 20 ) 2] and [M (L)2]rcH20 , M = Z n(II), or C d (II), n = 0 —3 and L = anion o f the corresponding ligand. Their structures have been suggested by elem en tal analysis, electronic and IR spectroscopy, and conductivity m easurem ents. It was found that the sulfonam ide ligands are m onobasic bidentate ON donors of the quinolinol group. C onsequently, the Z n(II) and Cd(II) com plexes are formulated as tetrahedral, whereas in C u(II) com plexes a distorted octahedral environm ent o f the metal ion is proposed. It was proven that the metal chelates inhibit and actively affect the germination o f wheat seed.

Introduction In recent years an increasing num ber of metal complexes of 8-hydroxyquinoline and sulfonamide derivatives has been studied due to the established biological activity of these classes of compounds and the novel structural features presented by the metal complexes of such ligands [1—4], Some sulfonamides are used in the treatm ent of cancer [5], malaria [6], leprosy [7], and tuberculosis [8]. Sulfonamides are drugs of proven therapeutic im portance and are used against a wide spectrum of bacterial ailments [9—11]. O u r interest in the coordination chemistry of biologi cally active com pounds led us to study the ligating properties of some 8-hydroxyquinoline-5-sulfonamides whose coordination chemistry is less devel oped in the literature [12]. Also, these kinds of molecules display a quite varied coordination be haviour. We report herein on the preparation and characterization of C u(II), Z n(II) and C d(II) com plexes of 8-hydroxyquinoline-5-sulfonamide with the aim of investigating their biological activity. Experim ental Solvents used in this study were of A R grade. All other m aterials were of G .R . grade. The sulfon amide ligands were prepared by the following gener al procedure [4, 13]. 8-Hydroxyquinoline was treated with chlorosulfonic acid. The resulting sulfonyl * Reprint requests to Dr. S. A . Ibrahim. Verlag der Zeitschrift für Naturforschung, D -7400 Tübingen 0 9 3 2 -0 7 7 6 /8 9 /1 2 0 0 -1 4 8 8 /$ 01.00/0

chloride was allowed to react with hydrazine hydrate (98% ), 2-am inopyridine, -1-pipyridine, or -1-morpholine in benzene. The purity of these sulfonamide ligands was checked by elemental analysis and IR spectra. Synthesis o f the solid chelates

The following general procedure has been adopted for the preparation of the metal chelates. The re quired am ount of the ligand was dissolved in the least am ount of ethanol and treated with the appropriate am ount of a solution of CuC12-2 H 20 , ZnCl2 or CdCl2-2 H 20 in the m olar ratio 2:1. The reaction mixture was then evaporated to a small volume and left to cool whereby the solid chelates separated. The deposited solids were filtered off, washed with hot water, and dried in vacuo over P20 5. The results of elemental analysis of the prepared chelates together with their color, decomposition tem perature, and molar conductance values are shown in Table I. Preparation o f seed germ ination fo r m etal chelates testing

Synthetic metal chelates were tested on the ger mination characteristics of mature wheat seeds (Triticum aestivum L .). Seeds were germ inated in sterilized glass Petri dishes. Each dish contained 10 seeds and 20 ml of each com pound solution (100 ppm ), and incubated in the dark at 25 °C for a maximum germination (20 days) in an incubator. Physical measurement UV-visible spectra were re corded on a CECIL 599 spectrophotom eter using 1 cm matched silica cells. IR spectra were obtained as KBr disks using a Perkin Elm er 599-B spectro-

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Table I. Analytical data, color, decom position tem perature, and molar conductance values o f the different chelates. Com pound

[Cu(C9H 8N 3S 0 3)2(H 20 ) 2] [Zn(C9H 8N 3S 0 3)2]H 20 [Cd(C9H 8N 3S 0 3)2] • 2 H 20

Color

yellowish green yellow

D ecom p. Analysis calculated (found) [%] temp. (°C) Carbon Hydrogen Nitrogen >300 270

[C u (C 14H u N 3S 0 3)2(H 20 ) 2]

yellowish 290 white deep green > 300

[Z n(C 14H nN 3S 0 3)2] -3 H 20

yellow

290

[Cd(C14H nN 3S 0 3)2] ■H 20

yellow

275

[C u (C 14H 14N 2S 0 3)2(H 20 ) 2] • h 2o

295

[Z n(C 14H 14N 2S 0 3)2]

greenish yellow yellow

[Cd(C14H 14N 2S 0 3)2] • H zO

yellow

>300

[C u (C 13H 13N 2S 0 4)2(H 20 ) 2]

yellow

>300

[Z n(C I3H 13N 2S 0 4)2] • H 20

yellow

260

[Cd(C13H 13N 2S 0 4)2] • 2 H 20

yellow

280

250

38.74 (37.92) 38.61 (38.61) 34.59 (35.23) 47.89 (48.62) 46.57 (46.21) 45.87 (45.30) 48.16 (47.93) 52.05 (52.63) 47.29 (47.80) 45.50 (44.80) 46.60 (46.32) 42.48 (43.10)

3.61 (4.11) 3.24 (3.70) 3.22 (3.60) 3.73 (4.20) 3.90 (3.25) 3.30 (3.20) 4.90 (5.31) 4.36 (4.66) 4.25 (3.80) 4.40 (4.21) 4.21 (4.63) 4.11 (4.30)

15.05 (14.82) 15.00 (15.60) 13.44 (14.00) 11.96 (12.23) 11.63 (12.40) 11.46 (11.82) 8.02 (8.30) 8.67 (8.32) 7.87 (8.21) 8.16 (7.73) 8.36 (7.83) 7.62 (8.35)

Sulfur

Qd

11.49 (12.12) 11.45 (12.33) 10.26 (10.70) 9.13 (8.65) 8.88 (8.61) 8.74 (8.32) 9.16 (9.61) 9.92 (9.63) 9.01 (8.63) 9.34 (8.87) 9.57 (9.21) 8.72 (8.60)

12.00 19.70 17.10 29.40 11.40 10.40 9.60 16.50 10.70 23.10 18.80 20.10

a In Ohm 1 cm 2 mol ‘.

photom eter (4000—200 cm -1). Conductivity m easure ments were carried out using an LF Digi (conductance bridge and an immersion cell at room tem perature (—25 °C). The 8-hydroxyquinoline-5-sulfonamides used have the following structure:

found to be in the range 9.60—29.40 O hm -1 m ol-1 cm2 which indicates a non-electrolytic nature of these com plexes since a reasonable range [14] for 1:1 electrolytes in ethanol solutions is 35—45 O hirT 1 m ol-1 cm2. Infrared spectra

R = N H 2, L,; = -2-am inopyridine, L2; = -1-pipyridine, L3; = -1-m orpholine, L4.

Results and Discussion Elem ental analysis data of the chelates along with their color, decomposition tem perature, and molar conductivity value are listed in Table I . The data clear ly indicate that the sulfonamides used act as monobasic bidentate ligands. The proposed formulae are [Cu(L)2-2 H 2Oj and [M (L)2]nH 20 for the 1:2 com plexes (where M = Z n(II) or C d(II), L = L j—L4 and y> = 0 —3) The molar conductance values of 10-3 M ethanolic solutions of the different complexes synthesized are

Relevant IR bands which provide structural evi dence for the mode of attachm ent of the ligands to the metal ions are reported in Table II. The strong bands appearing in the range 1610—1670 cm-1 in the spectra of the free ligands can be assigned to the quinoline vc=N [15]. This band was found at lower frequencies in the spectra of the complexes, a be haviour which is convincing evidence for coordina tion of the quinoline nitrogen to the metal ion. Also, the IR band due to v0.phenyl [16] found at 1280 cm-1 in the IR spectrum of L! or L4, and at 1265, 1285 cm-1 in the IR spectra of L2 and L3, respectively, is shifted to lower frequencies in the IR spectra of the com plexes (c/. Table II). This shift can be considered as an evidence for the participation of the quinolinol oxygen atoms in complex formation. Thus, the shifts in vc=N and v0_Ph suggest that the complexes are formed by coordination of the sulfonamide ligands to


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Table II. Som e IR frequencies o f the sulfonam ide ligands and their metal chelates. Com pound

voh

Vnh

VC=N

vO-Ph

vs=o asymm.

vs=o symm.

vM-0

VM-N

L, Cu(II) —L, Zn(II) —Lj Cd(II) —L, l2 C u (II) —L i Zn(II) —L-> C d (I I )- L , U C u (II)—L3 Zn(II) —L3 Cd(II) —L3 l4 C u (II) —L4 Z n (II)—L4 Cd(II) —L4

- (3300) 3400 3420 broad band (3320) 3400 broad band 3400 (3320) broad band 3400 (3360) broad band 3420 3400

3160 3100 3200 3140 3100 3100 3100 3070 3090 3150 3080 3100

1610 1605 1600 1600 1670 1630 1605 1625 1625 1620 1620 1625 1625 1600 1620 1620

1280 1250 1245 1235 1265 1240 1250 1240 1285 1270 1270 1275 1280 1245 1240 1240

1370 1380 1370 1375 1365 1370 1375 1365 1370 1375 1370 1370 1375 1375 1375 1375

1160 1170 1170 1155 1160 1160 1170 1165 1165 1160 1165 1165 1165 1170 1165 1165

400 405 420 450 410 400 425 415 430 410 420 420

380 375 390 375 375 375 390 370 380 375 370 370

the m etal ions through the quinolinol moiety. The upward shifts of bands at 730—745 cm-1 to 750—760 cm -1 due to out-of plane ring deformation and from 480 to 500 cm -1 (the in plane ring deform a tion modes) also indicate the coordination of the metal ion through oxygen and nitrogen of 8-hydroxyquinoline [17]. The bands due to vM-o and vM_Nwere observed a t400—450 cm -1 and375—390 cm -1, respec tively [18]. The free ligands have two strong bands in the range 1365 —1375 cm -1 and 1160—1165 cm-1 as signable to asymmetric and symmetric vs=G [19], re spectively. These two bands were located in the IR spectra of the different complexes at almost the same frequencies as in the spectra of the free ligands. This indicates that the sulfonyl group did not participate in complex form ation. On the other hand vs_N of the spectra of free ligands was found to have the same location in the spectra of the complexes. The four sulfonamide ligands possess two bands in the highfrequency region due to the stretching vibration of the H -bonded O H and NH group at 3300, 3160 cm-1 for Lj, 3320, 3140 cm -1 for L 2 , 3320 cm -1 for L3 and 3360, 3150 cm -1 for L4. These two bands appears in the IR spectra of the complexes with some changes where instead one strong band covering their range was observed. Also, in some cases, a new band ap peared at higher frequencies (3400—3420 cm-1). This behaviour can be ascribed to the presence of w ater molecules in the complexes. The band ob served in the IR spectra of the Cu(II) complexes, in the range 840—950 cm -1 where the free ligands lack bands, is assignable to the rocking mode of coordi

nated water [20]. This behaviour is in accord with the results of elemental analysis and indicates that the water molecules of Cu(II) chelates are inside the coordination sphere of the metal ions. A conclusion which is further confirmed by thermogravimetric analysis of the Cu(II) complexes, where a weight loss at 100—120 °C corresponding to one or two lattice water molecules for Z n(II) or C d(II) complexes is observed. For Cu(II) chelates a weight loss corre sponding to two coordinated water molecules is found in the range 170—190 °C. Electronic spectra

The electronic spectra of solutions in ethanol were recorded. The Amax and vmax values of the absorption bands observed are listed in Table III. Solutions of Zn(II) and Cd(II) complexes exhibit characteristic CT bands in the range 26,315—20,640 cm-1 (cf. Table III). The bands which appeared within 38,460—30,303 cm -1 are due to intraligand electronic transitions. The long wavelength visible band ob served in the spectra of Cu(II) complexes can be attributed to a d —d electronic transition. The un expectedly high molar extinction coefficient of this band suggests a distorted octahedral geometry of such complexes [21]. Based on the suggested dis torted octahedral geometry the d —d band observed in the electronic spectra of the Cu(II) complexes can be assigned to the transition 2E 2g 2T2e. On the basis of the foregoing discussion the pro posed structure of metal complexes can be form u lated as follows:


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S. A . Ibrahim et al. • C u(II), Z n(II) and Cd(II) Chelates H,0

Structure II

Structure I Structure I. W here R = N H : ; -2-aminopyridine; -1 -pipyridine; -1-m orpholine.

Structure II. Where R = as the same in I, M = Zn(II); Cd(II).

Role o f com plexes on seed germination

reached to high yield (97%) under compounds L2 and Cd(II) —L3. Minimum percentage of seed germi nation is quite clear in a solutions of compounds C u (II)—L3, C u(II) —L4 and C d (I I)- L 4 (77%). Elon gation of radical seems to be more sensitive than that of plumule. As in em ergence, the elongation of radicle decrease in the presence of compounds C u (II)—L3, C u( I I ) - L 4 and C d (II )-L 4 (1 .5 -2 .5 cm), whereas an increase took place under com pound L4 (11.3 cm). On the other hand, accumulation of dry m atter in the embryonic axis is slight with compounds Z n (II)—L2, C u (II)—L2, C u(II)—L4 and C D ( I I ) - L 4, and tended to a maximum in the compound solutions Z n (II)—L3 and C d(II)—L3. Trace elements in single or in complex forms may be taken up by plants in toxic amounts from the soil. Their action involves interference with inhibition of photosynthesis and/or respiration, and/or alternation of m itochondria m em brane premeability [22]. Data obtained (Table IV) indicate that C u (II)—L3, C u( I I ) - L 4 and C d ( II) -L 4 complexes retard the biochemical activities of plants as hormons and en zymes. C u(II)—L2, Z n (II)—L3 and Cd(II) —L3 com plexes as well as L2 and L3 increase the emergence elongation and dry m atter translocation in seed or gans under certain levels.

Seed germ ination characteristics were shown in Table IV. Em ergence of radicle and plumule was

Table III. Electronic spectral data o f metal chelates. Com plex

^-max [cm “ ']

^max [m ol-1 cm 2]

A ssignm ent

C u (I I )-L ,

37,735 26,250 17,640 31,250 25,000 26,315 30,303 25,640 16,130 20,640 31,250 26,315 30,303 26,315 15,000 38,460 31,250 31,300 25,000 36,600 26,000

1,800 700 400 1,650 300 600 2,400 750 420 750 1,650 600 1,400 1,000 430 3,000 1,800 1,800 500 2,800 1,100

intraligand charge transfer 2E i2g —> 2T,2g intraligand charge transfer charge transfer intraligand charge transfer 2E-,2g —> 2T-, 12g charge transfer intraligand charge transfer intraligand charge transfer 2E 2g- 2T2g intraligand intraligand intraligand charge transfer intraligand charge transfer

Zn(II) —L, Cd(II) —L, Cu(II) —L2

Zn(II) —L, Cd(II) —L2 Cu(II) —L3

Zn(II) —L3 Cu(II) —L4 C d (II)—L4

Com pound

Em ergence

Elongation [cm] Plumule Radicle

Dry weight [%] Plumule Radicle

Storage Tissue

L, Cu(II) —L, Z n (II)-L , Cd(II) —L2

97 87 80 87

9.6 11.0 10.1 9.6

7.4 7.4 6.7 8.0

26.7 31.3 26.1 26.2

24.4 15.9 11.4 15.4

48.9 52.8 52.5 58.5

l3 Cu(II) —L3 Zn(II) —L3 Cd(II) —L3

90 77 87 97

8.9 9.6 11.0 9.6

5.2 1.6 10.4 6.6

26.8 27.9 38.8 20.7

14.3 10.6 19.7 22.2

58.9 61.5 41.5 57.1

l4 Cu(II) —L4 Zn(II) —L4 C u (II) —L4

80 77 83 77

8.7 9.6 8.6

20.3 25.2 27.6

20.0 9.6 18.8

59.7 65.0 53.6

S 6

11.3 1.5 8.5 2 5

25. a

11.2

M 4

Control

83

10.4

10.0

31.9

21.5

45.6

Table IV. Effect on the germ i nation characteristics o f wheat seeds by the C u(II), Z n(II) and Cd(II) com plexes.


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