Synthesis and charecterization of a new ligand Schiff bases and its complexes Co(II),Ni(II), Cu(II), and Zn(II) ions Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 38 Synthesis, Characterization and Antibacterial Activities of Ligand Type N2O4 Schiff base and its Novel Complexes with Co(II), Ni(II), Cu(II) and Zn(II) ions. Ahmed T. Numan * , Manhel R. Aziz *,1 and Sinaa M. Shaker ** *Department of Chemistry,College of Education, Ibn-Al-Haitham,University of Baghdad,Baghdad, Iraq. ** Microbiology, Medical City, Teaching Laboratories, Baghdad, Iraq. Abstract The reaction of 2-amino benzoic acid with 1,2-dichloroethane under reflux in methanol and KOH as a base to gave the precursor [H4L]. The precursor under reflux and drops of CH3COOH which reacted with (2mole) from salicycaldehyde in methanol to gave a new type N2O4 ligand [H2L], this ligand was reacted with (MCl2) Where [M= Co (II), Ni(II), Cu(II) and Zn(II)] in (1:1) ratio at reflux in methanol using KOH as a base, to give complexes of the general formula [M(L)]. All compounds have been characterized by spectroscopic methods [ 1 H NMR ( just to the ligand), FTIR, uv-vis, atomic absorption], melting point, conductivity, chloride content, as well as magnetic susceptibility measurements. From the above data, the proposed molecular structure of [Co(L)], [Ni(L)], [Cu(L)] and[Zn(L)] complexes adopting an octahedral about this metal ions. The synthesized ligand, along with their metal complexes were screened for their in vitro antibacterial activity against ten local strains of E. coli as gram-negative bacteria in addition to ten strains of Salmonella typhi and to ten strains of Acinetobacter baumannii and Ten gram- positive bacteria utilizing for locally strains of Staphylococcus aureus, were tested also using the agar diffusion technique. Keywords: Schiff base , Complexes . الخالصة تحا الصعاديد داي كلاووو أكااا -2,1ما أمينو حاام البنووكاك -2وذلك من مفاعلة [H2L] تضمن البحث تحضير الليكاند ومان الا ب تفاعاا الماادذ [H4L] ود هيدووكسايد العاودكوك كماعادذ اذ اعاات الصفاعاا الماادذ الو اايةاالوجااع يا الميااانوب و وجا عاات الالجا اذ ا CH3COOHتح الصعاديد االوجااع يا الميااانوب ولاارا مان Salicylaldehydeموب من 2م الو اية ( 1:1) ثم مفاعلة الليكاند ما دا الدنا ار الفلوكاة ا اصاداك الميااانوب و اااع للصفاعاا و نسابة (N2O2)نوع [H2L]الصفاعا الليكاند , حياث [M(L)]وتح الصعديد األوجاع , حيث تكون مدمدا جدكدذ ذوا العيغة الداماة كماعدذ وجود هيدووكسيد البوتا يوكو M= Co(II), Ni(II), Cu(II), and Zn(II) . شاع جمي المركبا الارق الايفية الصالية )االشادة تحا الحماراا واالشادة ياوق وطيا الارنين الناووي المغناطيسا و المرئية –البنفسجية 1 HNMR )الصحلياا الكما الادليك للدنا ار ما الصو ايلية و( )يماظ لليكاناد دوجااة االنعااباو والحسا ااية المغناطيسااية ماان نصااائا البحااث كااا التااكا الفرا اا الممصاار الموالوكااة الكبر ائيااة ومحصااوو الكلااوو و [Co(L)], [Ni(L)], [Cu(L)], [Zn(L)] . عتار دو الفدالية الباكولوجية الاوج الالية الحية لليكاناد ومدمداتاض ادثمان الساو ماان وعتاار عااوال Salmonella typhiالاارو ماان اب أ و عتاار عااوال كبكصركااا ااالبة لعاابغة كااراك E. coliماان اب عااوال Acinetobacter baumannii ماان اب عتاار عااوال وStaphylococcus aureus بكصركااا موجبااة لعاابغة كااراك حيااث جمياا ك األ ناف أالصبر أ صاداك تمنية الحيود. Introduction Schiff bases and their coordination compounds have played a great importance in medicine, industry and biochemistry. Schiff bases are characterized by the (-N=CH-) (imine) group which imports in elucidating the mechanism of transamination rasemination reaction in biological (1,2) . During the past two decades, considerable attention has been paid to the chemistry of metal complexes containing nitrogen and other donor (3) . This may be attributed to their stability, biological activity (4) and potential application in many fields such as oxidation catalysis (5) and electrochemistry (6) . We have already drawn attention (7-11) to the strong relationship between metals or their complexes, and antibacterial (12-18) , and anticancer (19,20) activities. In 2009 A. Thabit and co-workers reported the synthesis of a Novel ligand type N2O2 and its complexes with Co(II), Cu(II), Zn(II), and Cd(II), which have been characterized by spectroscopy and elemental analysis (21) . This paper reports the synthesis and characterization of new derived from the reaction of α-amino carboxylic acid with 1,2- dichloroethane in methanol, resulted (precursor)[H4L], which reacted with salicylaldehyde and its Co(II), Ni(II), Cu(II) and Zn(II) complexes. 1Corresponding author E- mail : manhelreaziz@yahoo.com Received : 13/10/2009 Accepted : 24/1/2010 Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 39 Experimental Chemicals used were analytical grades; metals were used as chloride salts. The complexes were determined by absorption technique, using Shimadza (A.A) 680 G atomic absorption spectrophotometer. I.R data were recorded as (KBr) disc using a Schimadza 4800 s FTIR spectrophotometer in the range (4000-400) cm -1 which measured at the laboratories of Ibn-Sinaa Company. 1 H- NMR spectra were recorded in DMSO-d6 using Burcker 300 MHz spectrometer 1 which measured at Amman - Jordan. (UV-Vis.) spectra were obtained in (MeOH) on a CECIL, CE 2700 spectrophotometer in the range (200- 900) nm using quartz cell which measured at the college of Ibn- Al-Haithem. Magnetic measurements were carried out on solid compounds using 6 Bruker B.M. Melting points were recorded on an electro thermal Stuart apparatus and are not corrected. Electrical conductivity measurements of the complexes were recorded at 25C for 10 -3 M solutions in (MOH) as a solvent using a Wissenchaftilich technique werksttaten, D1820 bweilheimI.F 42 conductivity meter which measured at the college of Ibn- Al-Haithem. The chloride contents for complexes was determined by potentiometric titration method on (686-titro processor-665), Dosinat-metrom Swiss, which measured at the laboratories of Ibn-Sinaa Company. Antibacterial screening was done at laboratories of medical city, Baghdad using agar diffusion technique (22,23) . The ligand along with their metal complexes were screened for their in vitro antibacterial activity against gram negative bacteria (E. coli), gram-positive bacteria (Staphylococcus aureus), Salmonella typhi and Acinetobacter baumannii bacterial strains. The ligand and their complexes have shown varied antibacterial activities against one or more bacterial strains and this activity enhanced on coordination / chelating. Preparation of the ligand [H2L] The ligand was prepared by two steps: Step (1): A solution of α-amino carboxylic acid (0.35 g, 2.25 mmole) in methanol (10ml) was added to it dichloroethane (0.2g, 2.23mmole) , (0.2 ml) with KOH (0.18ml) as a base, the mixture was refluxed for 3 hours with stirring. Then the mixture was allowed to cool at room temperature. The resulting a gray solid (precursor) [H4L] was obtained which filtered off and then washed with ethanol. Yield (37%), (0.25g), mp (245-250 C˚ dec.). Step (2): A solution of salicalyaldehyde (0.2 g, 1.66mmole), (0.18 ml) in methanol (5 ml) was added to the precursor solution [H4L] (0.25 g, 0.83 mmole), then (8) drops of CH3COOH was added slowly to the reaction mixture. The mixture was refluxed for (5 hours) with stirring. The resulting was orange solid of [H2L] as product was filtered of and then washed with ethanol. Yield (42%), (0.18g), mp (220-226 C˚ dec.). Preparation of the ligand [H2L] with metal ions (0.15 g, 2.94 mmole) of ligand solution in methanol (10ml), with KOH as a base was added to a solution of (0.07 g, 2.94 mmole) CoCl2.6H2O in methanol (10ml), the mixture was refluxed with stirring for (4 hours). The resulting was dark brown solid as product which was filtered of and then washed by water and re-crystallized with ethanol. The complexes [Ni(L)], [Cu(L)] and[Zn(L)], were obtained in a similar method to that mentioned in the preparation of [Co(H2L)2] complex described above, (Table1) stated the quantity of starting materials and some physical properties of the prepared complexes. Table 1 : The microanalysis results and some physical properties for the prepared ligand H2L and its complexes Compounds Formula Colour M.p(C˚) Yield% Chloride Metal M .wt H4L C16H16N2O4 Gray 245-250 dec. 37 Nil ----- 300.31 H2L C30H24N2O6 Orange 220-226 dec. 42 Nil ----- 508.52 [Co(L)](1) C30H22N2CoO6 Dark brown 230 dec. 60 Nil 10.42 (9.18) 565.44 [Ni(L)](2) C30H22N2NiO6 Yellowish green 292 dec. 78 Nil 10.38 (11.18) 565.20 [Cu(L)](3) C30H22N2CuO6 Dark green 320 dec. 52 Nil 11.15 (11.37) 570.05 [Zn(L)](4) C30H22N2ZnO6 Light green 230 dec. 53 Nil 11.43 (12.44) 571.90 Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 40 NH2 COOH + ClCH2CH2Cl 2 KOH Methanol Ref lux 3 hours 2-amin obenzoic acid dichloroethane H2N C O O CH2H2C O C O NH2 +2 CH OH O 2-hydroxybenzaldehyde ethane-1,2-diyl bis(2-aminobenzoate) N C O O CH2H2C O C O N CH HC HOOH (Z)-ethane-1,2-diyl bis(2-((Z)-2-hydroxybenzylideneamino)benzoate) Ref lux 5 hours Methanol CH3COOH 8 drops + MCl2 N C O O CH2H2C O C O N CH HC OO M KOH Methanol Ref lux 4 hours Results and Discussion Synthesis of the ligand The ligand [H2L] was prepared according to the general method shown in Scheme (1). The I.R spectral of the precursor [H4L] of the ligand [H2L], is shown in Fig (1), the results were summarized in Table (2) The figure exhibited band at (3329,3379) cm -1 which attributed to the stretching vibration of asymmetric and symmetric (N-H) for NH2 group, also the spectrum was showed bands at (1612)cm -1 , (1249) cm -1 and (1192) cm -1 attributed to υ (C=O) of ester group, υ (C-O) ester group and υ (C-O) phenolic respectively (21,24-27) , By comparing with the I.R spectrum of the ligand [H2L], Fig (2), Table (2) exhibited bands (3421) cm -1 , which can be attributed to υ (O-H) and (disappeared NH2 groups), also the spectrum showed bands at (1612)cm -1 , (1608) cm -1 , (1273) cm -1 and (1239) cm -1 attributed to υ (C=O) ester group, υ (C=N) imine group, υ (C-O) ester group and υ (C-O) phenolic respectively [21,24-27]. The (U.V-Vis) spectra for precursor [H4L], Fig (3), the results were summarized in Table (3), the figure exhibits two high intense absorption peaks at (248) nm εmax (2532) molar -1 cm -1 , and (319) nm εmax (2484) molar -1 cm -1 , which assigned to (π→π * ), and (n→π * ) transition respectively [28,29], While The (U.V-Vis) spectrum of the ligand [H2L] Fig (4), (Table3) exhibits three high intense absorption peaks at (250) nm εmax (2631) molar -1 cm -1 , (293) nm εmax (2660) molar -1 cm -1 , and (360) nm εmax (2581) molar -1 cm -1 , which assigned to (π→π * ), (π→π * ) and (n→π * ) transition respectively (28,29) . The 1 H NMR spectrum of the ligand (H2L), in DMSO-d 6 , Fig (5) shows proton of (O–H) group (ph–OH) which appears as a singlet peak signal at (10.2) ppm. The proton of (C–H) imine group appears as a singlet peak at (8.7) ppm. The multiples signals peaks at the range between (7-8)ppm, are due to aromatic hydrogen of carbon for the benzene ring which bonded with (C=O) carbonyl group, while the multiples signals peaks at the range between (6-7)ppm, are due to aromatic hydrogen of carbon for the benzene ring which bonded with (C=N) imine group, also the spectrum of the ligand appears a triplet peak at (4.7)ppm, which assigned to (-CH2-) methelene group, as soon as a singlet high peak at (2.5)pmm for the DMSO-d 6 solvent [24,25,30,31]. Where M= Co(II),Ni(II),Cu(II),and Zn(II) Scheme 1 : The preparation of the ligand [H2L] and its complexes Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 41 Table 2 : Infrared spectral data(wave number ύ) cm -1 for the ligand H2L and its complexes Figure 1: Infrared spectrum of the precursor (H4L) Figure 2 : Infrared spectrum of the ligand (H2L) Figure 3 : Electronic spectrum of the precursor (H4L) Compound υ(C=N) υ(C=O) ester υ(C-O) ester υ(C-O) phenolic υ(O-H) υ(M-O) phenolic υ(M-O) esteric υ(M-N) H4L ----- 1612 1249 1192 ----- ---- ----- ----- H2L 1608 1612 1273 1239 3421 ----- ----- ----- [Co(L)](1) 1593 1612 1327 1300 ----- 505 461 416 [Ni (L)](2) 1593 1612 1327 1300 ------ 536 440 430 [Cu (L)](3) 1585 1609 1319 1288 ------ 540 468 428 [Zn (L)](4) 1593 1611 1327 1300 ----- 516 459 445 Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 42 Table 3 : Electronic spectral data for the ligand H2L and its complexes C.T= Charge transfer Figure 4: Electronic spectrum of the ligand (H2L) Figure 5: 1 H NMR spectrum of the ligand (H2L) Compound Λ nm εmax molar -1 cm -1 Assignment Ratio Molar conductivity S.cm 2 .mol -1 Magnetic susceptibility B.M coordination H4L 248.9 319.7 2532 2484 π→π* n→π* ----- ------ ------ ------- H2L 250.0 293.6 360.8 2631 2660 2581 π→π* π→π* n→π* ----- ------- ------ ------ [Co(L)](1) 248.5 295.6 414.0 629.8 2642 2531 1264 96 Ligand field Ligand field C.T 4 T1g(F)→ 4 T2g(F) neutral 18.1 3.87 (4.15) Octahedral [Ni(L)](2) 245.0 305.3 400.1 580.0 2597 1617 1317 62 Ligand field Ligand field C.T 3 A2(g)→ 3 T1g (p) neutral 14.9 2.83 (3.2) Octahedral [Cu(L)](3) 243.5 300.0 406.1 698.9 2608 2551 2636 52 Ligand field Ligand field C.T 2 E → 2 T2 neutral 12.46 1.7 (1.9) Octahedral [Zn(L)](4) 220.3 289.0 388.5 1483 584 371 Ligand field Ligand field C.T neutral 13.65 ------ Octahedral Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 43 Synthesis of the complexes The reaction the of ligand [H2L] with Co(II), Ni(II), Cu(II) and Zn(II) was carried out in MeOH. These complexes are stable in solution. The analytical and physical data, Table (1) and spectral data, Table (2) and Table (3) are compatible with the suggested structure Scheme (1). The I.R spectra of the complexes [Co(L)](1), [Ni(L)](2), [Cu(L)](3), and [Zn(L)](4). Fig (6) and Fig (7), respectively, the results were summarized in Table (2), the figure exhibited at (1608) cm -1 in the free ligand spectrum which assigned to υ (C=N) imine group Shifted to lower frequency and appeared at (1593) cm -1 , (1593) cm -1 , (1585) cm -1 and (1593) cm -1 for the complexes (1),(2),(3), and (4) respectively (25-28) . These bands were assigned the υ (C=N) stretches of reduced bond order, this can be attributed to the delocalization of metal-electron density into the ligand π-system (HOMO→LUMO) [32,33]. (HOMO=Highest occupied molecular orbital, LUMO= Lowest unoccupied molecular orbital). The phenolic (C-O) stretching vibration appeared at (1239) cm -1 in the free ligand was Shifted to higher frequency and appeared at (1300) cm -1 , (1300) cm -1 , (1288) cm -1 , and (1300) cm -1 for the complexes (1), (2), (3) and (4) respectively, as well as ester group (C-O) stretching vibration appeared at (1273) cm -1 in the free ligand was shifted to higher frequency too, and appeared at (1327) cm -1 , (1327) cm -1 , (1319) cm -1 and (1327) cm -1 for the complexes (1), (2), (3) and (4) respectively, all that indicated a linkage between oxygen of phenolic group and oxygen of ester group and the metal (24,32,34) . The spectra showed the appearance of bands at (416) cm -1 , (430) cm -1 , (428) cm -1 and (445) cm -1 refer to υ (M-N) for complexes (1), (2), (3) and (4) respectively, These bands confirm the coordination of the nitrogen atom to the metal center, while the bands at [(505),(461)] cm -1 , [(536),(440)] cm -1 and [(540),(468)] cm -1 [(516),(459)] cm -1 assigned to υ (M-O) of complexes (1),(2),(3), and (4) respectively, Theses bands indicating the phenolic and esteric oxygen in the ligand is involved the coordination with metal ions in complexes [34- 37]. The (U.V-Vis) spectra for the complexes are shown in Fig (8) and Fig (9), Table(3), Complex [Co(L)]: showed two high intense peak at (248) nm εmax (2642) molar -1 cm -1 and (295) nm εmax (2531) molar -1 cm -1 were assigned to the ligand field, while a medium intense peak at (414) nm εmax (1264) molar - 1 cm -1 was assigned to the charge transfer (C.T), a weak broad peak at (629) nm εmax (96) molar -1 cm -1 was assigned to(d-d)electronic transition ( 4 T1g(F)→ 4 T2g(F)) suggesting octrahedral geometry (29) . Complex[Ni(L)]: showed two high intense absorption peaks at (245) nm εmax (2597) molar -1 cm -1 and (305) nm εmax (1617) molar -1 cm -1 are due to the ligand field, another high intense peak at (400) nm εmax (1317) molar -1 cm -1 was assigned to (C.T), while a weak broad peak at (580)nm εmax (62) molar -1 cm -1 was assigned to (d-d) electronic transition (3A2(g)→ 3 T1g(p)) suggesting octahedral geometry (29) . Complex[Cu(L)]: showed two high intense absorption peaks at (243) nm εmax (2608) molar -1 cm -1 and (300) nm εmax (2551) molar -1 cm -1 are due to the ligand field. a high intense absorption peak at (406) nm εmax (2636) molar -1 cm -1 was assigned to (C.T), while a weak broad peak at (698) nm εmax (52) molar -1 cm -1 was assigned to (d-d) electronic transition ( 2E →2T2 ) suggesting octahedral geometry (29) . Complex[Zn(L)]: showed two peaks at (220) nm εmax (1483) molar -1 cm -1 and (289) nm εmax (584) molar -1 cm -1 are due to the ligand field. while a weak broad peak at (388) nm εmax (371) molar -1 cm -1 was assigned to (C.T), the d 10 configuration of Zn II ion along with the data obtained confirms a octahedral structure around the ion (29) . The molar conductance of the complexes in methanol lie in the range(12.46-18.1 Ohm -1 cm -2 mol -1 ), Table(3), indicting their non-electrolyte having molar ratio of metal:ligand as 1:1 (38) . The magnetic moments for the complexes are shown in Table (3) (39) . Figure 6: Infrared spectrum of the complex [Co(L)](1) Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 44 Figure 7: Infrared spectrum of the complex [Ni(L)](2) Figure 8: Electronic spectrum of the ligand [Co(L)](1) Figure 9: Electronic spectrum of the ligand [Ni(L)](2) Biological activity The antibacterial activity of the synthesized ligand [H2L] and its complexes [Co(L)](1), [Ni(L)](2) , [Cu(L)](3) , and [Zn(L)](4) Table (4, 5, 6 and7), Fig(10 and 11) were tested utilizing the agar diffusion technique (40) . The organisms tested were Staphylococcus aureus , E. collie , Salmonella typhi , and Acinetobacter baumannii. The agar media (Muller-Hinton agar) were inoculated with test organisms and a solution of the tested compound (100μg/ml) (41) , was placed separately in cups (6 mm diameter) in the agar medium. The inhibition zones were measured after 24 hours incubation at 35 C ˚ . Separate studies were carried out with the solution alone of DMSO and the showed no activity against any bacterial strains (41) . The results of these studies revealed that metals complexes showed an effective in the inhibition of Acinetobacter baumannii, Table (4). The ligand and (Co +2 , Ni +2 , Cu +2 ,Zn +2 ) complexes were showed an inhibition in some strains in each of Staphylococcus, E. coli, and Salmonella typhi, as shown in Table (5, 6, and 7) . Biological activity of the previous compounds in inhibition of bacterial growth could be attributed to one of the following mechanisms, the first mechanism is by the inhibition of the bacterial cell wall synthesis by bounding to the precursor of the cell wall (42) , second mechanism revealed that some antibodies have similar stereo structure to substrate (D-alanyl D-alanine). So it will act competitive inhibitions for the enzymes (transpeptidase and /or carboxpeptidase) which are the main enzymes catalyzed the end step in the biosynthesis of peptidoglycans of the bacterial Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 45 cell wall (43) . Other mechanisms could contributed to the results found in the study which include the inhibition of biosynthesis of bacterial proteins by linking to the ribosoms by doing so, the ribosomes will not be in contact with tRNA, so the bacteria will not survive (44) . An other mechanisms were postulated that some antibodies inhibit the denovo synthesis of bacterial DNA by splitting DNA in DNA-enzyme complexes by inhibition DNA ligase (45) . Table 4 : Biological activity of Acinetobacter baumannii bacteria of the ligand [H2L] and its complexes A= Acinetobacter baumannii bacteria Table 5 : Biological activity of Staphylococcus aureus bacteria of the ligand [H2L] and its complexes S= Staphylococcus aureus bacteria Table 6 : Biological activity of E. coli bacteria of the ligand [H2L] and its complexes E= E. coli bacteria Table 7 : Biological activity of Salmonella typhi of the ligand [H2L] and its complexes Sal= Salmonella typhi bacteria Compound Bacteria (zone of inhibition (diameter mm)) A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 H2L 14 11 Nil 14 16 14 15 12 13 16 [Co(L)](1) 15 10 Nil 15 14 15 12 Nil 16 15 [Ni(L)](2) 14 10 12 14 13 16 13 12 15 15 [Cu(L)](3) 14 10 11 12 13 12 13 13 12 13 [Zn(L)](4) 11 11 Nil 14 13 14 14 12 15 16 Compound Bacteria (zone of inhibition (diameter mm)) S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 H2L Nil Nil 16 Nil Nil Nil Nil Nil Nil Nil [Co(L)](1) Nil Nil 16 Nil Nil Nil Nil Nil Nil Nil [Ni(L)](2) Nil Nil 16 Nil Nil Nil Nil Nil Nil Nil [Cu(L)](3) 9 8 17 9 10 9 8 9 8 11 [Zn(L)](4) Nil Nil 18 12 Nil Nil 12 Nil Nil Nil Compound Bacteria (zone of inhibition (diameter mm)) E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 H2L Nil Nil Nil 12 12 10 Nil 11 Nil 10 [Co(L)](1) 9 Nil Nil 10 7 10 Nil Nil Nil 10 [Ni(L)](2) 10 Nil Nil 11 8 12 Nil 10 Nil 8 [Cu(L)](3) Nil Nil Nil 12 8 12 Nil 10 Nil 10 [Zn(L)](4) Nil Nil Nil 8 8 8 Nil 10 Nil Nil Compound Bacteria (zone of inhibition (diameter mm)) Sal1 Sal 2 Sal 3 Sal 4 Sal 5 Sal 6 Sal 7 Sal 8 Sal 9 Sal10 H2L Nil 11 Nil Nil Nil Nil Nil Nil Nil Nil [Co(L)](1) 10 12 9 Nil Nil Nil Nil Nil Nil 12 [Ni(L)](2) Nil Nil 10 Nil Nil Nil Nil Nil Nil Nil [Cu(L)](3) Nil Nil Nil Nil Nil Nil 12 9 Nil Nil [Zn(L)](4) 10 Nil Nil Nil Nil Nil Nil Nil Nil Nil Iraqi J Pharm Sci, Vol.19(1) 2010 Schiff base of aminobenzoic acid 46 Figure 10: Inhibition zones for Acinetobacter baumannii utilizing agar diffusion technique Figure 11: Inhibition zones for Staphylococcus aureus utilizing agar diffusion technique References 1. 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