научная статья по теме COORDINATION BEHAVIOR BASED ON SPECTROSCOPIC STUDIES OF THE CARBOXYLATE GROUP IN ORGANOTIN(IV) DERIVATIVES OF 2-[(2,4,6- TRIBROMOPHENYLAMIDO)]BENZOIC ACID AND 3-[(2,4,6-TRIBROMOPHENYLAMIDO)]PROPENOIC ACID Химия

КООРДИНАЦИОННАЯ ХИМИЯ, 2007, том 33, № 6, с. 414-421

УДК 541.49

Coordination Behavior Based on Spectroscopic Studies of the Carboxylate group in Organotin(IV) Derivatives of 2-[(2',4',6'- Tribromophenylamido)]benzoic Acid and 3-[(2',4f,6f-Tribromophenylamido)]propenoic Acid

© 2007 S. Shahzadi, K. Shahid, and S. Ali

Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan Received April 13, 2006

The complexes of two organic carboxylates (containing {O,O}-donor atoms) with Me2Sn(IV)Q2, n-Bu2Sn(IV)Cl2, Bz2Sn(IV)Cl2, Oct2Sn(IV)O, Me3Sn(IV)Cl, n-Bu3Sn(IV)Cl, Ph3Sn(IV)Cl, and Bz3Sn(IV)Cl having ligand-to-metal ratios of 1 : 2 and 1 : 1 were prepared by two different methods. The FT-IR spectra clearly demonstrated that organotin(IV) moieties react with {O,O}-atoms of the ligands. It was found that in all cases the COO- group was acting as bidentate in the solid state. The 119Sn NMR data revealed that the organotin(IV) moiety has a tetrahedral geometry in non-coordinating solvents. The biological activity of these compounds was compared with that of their precursors, and all the synthesized compounds show significant antibacterial activity. The antifungal activity of the complexes against six plant pathogens has been estimated. The complexes display marked toxicity against these fungi and are more fungitoxic than free acids. The compounds have also shown significant cytotoxicity against Brine Shrimp (Artemia salina).

INTRODUCTION

Organotin(IV) carboxylates form an important class of compounds and have been receiving increased attention in recent years, not only because of their intrinsic interest but owing to their varied applications.

These applications include the use of organotin(IV) compounds commercially as industrial and agricultural biocides because of their antifungal properties [1]. Furthermore, organotin compounds also possess antitu-mour activity [2]. Diorganotin(IV) derivatives, e.g., Et2Sn(IV) and Bu2Sn(IV) carboxylates, are known as antitumour agents [3-5]. Some examples find wide use as catalysts, and stabilizers, and certain derivatives are used as antifouling paints and as wood preservatives. Organotin(IV) compounds also possess toxicity towards biological targets, which depends substantially on the structure of organotin toxicants [6].

Recently, considerable attention has been paid to the triorganotin(IV) derivatives having high in vitro anti-fungal activities against some medically important fungi. The low aqueous solubility of organotin compound is a limiting factor in the further research of their use in medicine [7]. On the basis of the known electron-acceptor properties of these compounds, it can be proposed that their toxicity is related to their interaction with electron- donor groups in biologically important molecules. Refer to various applications of organotin carboxylates and continuation of our studies of biologically active organotin(IV) derivatives of substituted anilines [8, 9], we synthesized some organotin(IV) derivatives of 2-[(2',4',6'-tribromophenylamido)]benzoic acid (HL1) and 3-[(2',4',6'-tribromophenylamido)] pro-penoic acid (HL2). These complexes were character-

ized by elemental analysis, infrared, multinuclear NMR (XH, 13C, 119Sn), and mass spectrometry. Their biological activity data have also been reported.

EXPERIMENTAL

Material and methods. All the reactions were carried out under an anhydrous atmosphere. Solvents were purified and dried before use. All the chemicals were of analytical grade and used without further purification. Di- and tribenzyltinchlorides were prepared according to reported methods [10]. Melting points are uncorrect-ed and were taken in a capillary tube on a MP-D Mita-mura Rikero Kogyo (Japan). IR spectra were recorded on a Bio-Rad FT-IR spectrophotometer as KBr discs. 1H, 13C, and 119Sn NMR spectra were recorded on a Bruker AM-250 spectrometer (Germany) using CDCl3 as an internal reference. 119Sn NMR spectra were obtained with Me4Sn as an external reference. Mass spectra were recorded on a MAT 8500 Finnigan instrument (Germany) at 70 eV.

Synthesis of ligands HL1 and HL2. A solution of phthalic anhydride (50 mmol, 7.4 g) or maleic anhydride (50 mmol, 4.9 g) in glacial acetic acid (300 ml) was added to a solution of 2,4,6-tribromoaniline (50 mmol, 9.8 g) in glacial acetic acid (150 ml) and the mixture was stirred at room temperature overnight. The yellow formed precipitates were washed with cold distilled H2O (200 ml) and air-dried. The general chemical reaction is given in eqs. (1) and (2):

Br

Br

■nh2 +

Br-

Br

Br

Ö

-nh2 +

Br

Br

i) Glacial acetic acid ^ / ii) Overnight stirring

Ö

Br

O

O i) Glacial acetic acid b ii) Overnight stirring

O

Br

Ö

o

O II

-NH- C^^^r- COOH

(HL1)

O II

-NH— C—CH= CH— COOH

(1)

Br

(HL2)

(2)

General procedure for synthesis of complexes.

a) HL1 or HL2 (3 mmol, 1.3 or 1.2 g, respectively) was suspended in dry toluene (100 mL) and treated with Et3N (3 mmol, 0.41 ml). The mixture was refluxed for 2-3 h and to this solution diorganotin dichloride (1.5 mmol) or triorganotin chloride (3 mmol) was added as solid (or liquid in the case of Bu3SnCl) with constant stirring and then refluxed for 8-10 h. The reaction mixture containing Et3NHCl was filtered off leaving organotin(IV) derivatives in the filtrate. The solvent was removed on a rotary evaporator, and the mass left behind was recrystal-lized from a CHCl3-«-hexane (1 : 1) mixture. The reaction is given in eqs. (3) and (4):

R2SnCl2 + 2Et3NHL

i) Toluene

2Et3NHCl

i) Toluene

ii) Reflux for 8-10 h lv2

R2SnL2 +

(3)

R3SnCl + Et3NHL U) R^fs-ic h RsSnL + Et3NHCl (4) where R = Me, «-Bu, Ph, Bz and Oct; HL = HL1 or HL2

RESULTS AND DISCUSSION

Compounds I-XIV were obtained by the reactions given in eqs. (3)-(5). The melting points, percentage yields, molecular weights and molecular formulas of the synthesized complexes are given in Table 1. All the compounds show sharp melting points. Elemental analysis data show good agreement between the calculated and found values.

The infrared spectra of di- and triorganotin compounds were recorded in a range of 4000-400 cm-1 as KBr discs. The absorption bands for structural assignments are given in Table 2. The carboxylate group is able to coordinate the metal ions by three different modes:

M-O \

C-R M°C-// \ '/ O O

R

(1)

(2)

C

R

(3)

R Me2 n-Bu2 BZ2 Oct2

HL1 I II III IV

HL2 V VI VII

R Me3 n-Bu3 Ph3 BZ3

HL1 VIII IX X XI

HL2 XII XIII XIV

b) HL1 or HL2 (1.3 or 1.2 g, respectively) was suspended in dry toluene (100 ml). To this solution, Oct2SnO (1.5 mmol) was added as solid with constant stirring, and the mixture refluxed for 8-10 h. Water formed during the reaction was removed via Dean-Stark trap. The solvent was evaporated through a rotary apparatus, and the obtained product was recrystallized in CHCl3-«-hexane (1 : 1) mixture. The reaction is given in eq. (5):

Oct2SnO + 2HL

ii) ReflUXfrVlO h R2SnL2 + H2O (5)

where HL = HL1 or HL2

By comparison, the data reported for other organo-tin(IV) complexes formed with the {O}-donor atom containing ligands, the following assignments were suggested for the complexes studied here. In the 35002900 cm-1 region, the ligands exhibit medium bands typical of OH stretching vibrations, which were absent in the spectra of the complexes, indicating the coordination of deprotonated COO- group to the central tin atom. The C=O stretching vibrations of HL1 and HL2 were observed at 1775 and 1705 cm-1, respectively. The bands are strong and sharp. The difference between vas(COO) and vs(COO) is important in the prediction of the nature of the binding mode of the ligand [11-13]. The difference between the two vibration frequencies were in the range of 161-197 cm-1, indicating a bidentate coordination mode of the COO- in the complexes [14] in the solid state. In all the complexes, medium to weak bands in a region of 410-495 cm-1 are assigned to Sn-O, and those in the region 510-580 cm-1 are assigned to Sn-C bonds.

Table 1. The elemental analysis data and physical data for R2Snl2, R2Snl2 and R3SnL1, R3SnL2

Compound Empirical formula M.W. M.p., °C Yield, % Contents (calcd/found), %

C H N

Me2SnL2 (I) C3oH2oN2O6SnBr6 1103 93-94 73 32.63/32.54 1.81/1.72 2.53/2.46

Bu2SnL2 (II) C36H32N2O6SnBr6 1187 90 69 36.39/36.30 2.69/2.61 2.35/2.29

Bz2SnLl (III) C36H28N2O6SnBr6 1255 100-103 60 40.15/40.19 2.23/2.17 2.23/2.29

Oct2SnL2 (IV) C44H48N2O6SnBr6 1299 176 77 40.64/40.59 3.69/3.60 2.15/2.09

Me2SnL2 (V) C22HX8N2O6SnBr6 1005 82 90 26.32/26.22 1.59/1.52 2.79/2.73

Bu2SnL2 (VI) C28H23N2O6SnBr6 1082 100-101 82 30.91/30.83 2.57/2.50 2.57/2.48

Oct2SnL22 (VII) C36H46N2O6SnBr6 1201 80 77 36.03/36.10 3.66/3.61 2.33/2.27

Me3SnL (VIII) ClvH!6NO3SnBr3 641 96-98 65 31.82/31.73 2.49/2.39 2.18/2.09

Bu3SnL (IX) C26H34NO3SnBr3 767 107-108 85 37.63/37.69 4.10/4.01 3.37/3.29

Ph3SnL (X) C32H22NO3SnBr3 827 64 80 46.43/46.35 2.66/2.61 1.69/1.61

Bz3SnLx (XI) C35H28NO3SnBr3 869 115-117 70 48.33/48.27 3.22/3.12 1.61/1.53

Me3SnL2 (XII) Ci3Hi2NO3SnBr3 591 88-89 67 26.39/26.30 2.36/2.31 2.36/2.41

Bu3SnL2 (XIII) C22H33NO3SnBr3 718 86 80 36.82/36.72 4.46/4.38 1.95/1.89

Ph3SnL2 (XIV) C28H2lNO3SnBr3 778 76 59 43.24/43.17 2.57/2.42 1.80/1.72

The 70-eV mass spectral data (m/z and percentage intensity) for the investigated compounds are reported in Table 3. For both di- and triorganotin derivatives, the spectra are easily interpreted in terms of the fragmentation patterns for diorganotin (A) and triorganotin(IV) (B) dicarboxylates shown below:

[RSn(O2CR')2]+

[RSn(O2CR')R']+

[RSnR2]+

[R2Sn(O2CR')2]

|-CO.

'2

i\nn+

[R2Sn(O2CR')R']

I -O2CR'

[R2SnR']+

I

-[SnR']

[Sn]+ (A)

-CO2

[R2SnR']+

-2R

-R

[RSnR']+

[R3Sn]+ ^^ [R3SnO2CR']+^ [R2SnO2CR']+

l-R

[R2Sn] +

l-R

[RSn]+

[R2Sn02CR']+ where

[Sn]+-(B)

-RR'

|-CÜ2 [R2SnR']+

- [RSnR']+

Br

R' = Br

O II

■NH-C-

Br

u

and

Br

Br

a

-NH— C—CH= CH—

Br

R

R

2

2

R

Table 2. IR spectral data for R2SnL^, R2Snl2 and

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