Journal of Saudi Chemical Society (2013) 17, 353–359

King Saud University

Journal of Saudi Chemical Society

www.ksu.edu.sawww.sciencedirect.com

ORIGINAL ARTICLE

Synthesis, pyrolytic and bioassay studies of complexes

Ni(II), Cu(II) and Zn(II) bromides with a chelating ligand

of N,N donor sites

Saeed-Ur-Rehmana,*, Sadia Rehman

a, Muhammad Ikram

a, Farhat Ullah

b

a Institute of Chemical Sciences, University of Peshawar, Peshawar, Pakistanb Department of Pharmaceutical Sciences, Kohat University, Kohat, Pakistan

Received 16 February 2011; accepted 27 April 2011

Available online 3 May 2011

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KEYWORDS

Aminobenzohydrazine;

Coordination compounds;

Thermal;

Bioassay

Corresponding author. Tel.

-mail address: srachem@yah

19-6103 ª 2011 Production

King Saud University.

er review under responsibilit

i:10.1016/j.jscs.2011.04.012

Production and h

: +92 91

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and hosti

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Abstract Coordination complexes of modified hydrazine are prepared with Ni(II), Cu(II), and

Zn(II) metal ions. The ligand is synthesized by removing the methoxy moiety of methyl anthranilate

with nitrogen of hydrazine hydrate, creating new coordination site. The coordination complexes are

synthesized by reacting the ABH ligand with dehydrated M(II) [Cu2+, Zn2+ and Ni2+] bromide in

an inert environment. The structures of the coordination complexes are elucidated basing on the

physical measurements including elemental analysis, NMR, IR, UV–Vis spectra, magnetic and con-

ductance measurements. These results reflect the M(ABH)Br2 composition of the corresponding

complexes. Thermal studies show the Irving William trend for the stability of complexes. Antibac-

terial activities and antifungal studies are also carried out in order to investigate the biological activ-

ity upon complexation.ª 2011 Production and hosting by Elsevier B.V. on behalf of King Saud University.

5641658/5843456.

( Saeed-Ur-Rehman).

ng by Elsevier B.V. on behalf

Saud University.

lsevier

1. Introduction

Lot of work has been done in the last three decades on thecoordination compounds of diamines, where H2N–NH2

(hydrazine) is the basic unit. Various research workers havefurther extended their work on the cyclic amines (diazacycloheptane and octane) by modifying them with introducing car-

bonyl or carboxylic acids in their structure. The modificationof cyclic diamines was further continued to restrict the freedomof C3 and C7 of diazacyclooctane to make the space availablefor further coordination (Hendra and Powell, 1960; Mann and

Watson, 1958; Musker and Hussain, 1966, 1969; Rehmanet al., 2009). These different diamine (cyclic or acyclic) confervarious geometries to the metal ion from tetrahedral square

planar to octahedral depending on the structure of diamine.

354 Saeed-Ur-Rehman et al.

Hydrazides are used in medicine; these include the anti-tuberculosis drug, isoniazid and the anti-hypertensive andperipheral vasodilator drug hydralazine (Hussain and

Saeed-ur-Rehman, 1982; Hoose et al., 1990; Saliaev et al.,1980). Isoniazid (isonicotinic acid hydrazide) has been shownto produce lung tumors in mice (Vidrio et al., 2003) and to in-

duce chromosome aberrations and sister chromatid exchangesin cultured rodent cells (Delaney and Timbrell, 1995). Hydra-zides are also a component in many complex drugs, such as

nitrofurans, triazole etc. (Holla et al., 2005; MacRae and Stich,1979; Strolin-Benedetti and Tipton, 1998; Saunders and Karo,1968). Furazolidone [N-(5-nitro-2-furfurylidine)-3-amino-2-oxazolidone], contains two rings: a nitrofuran-ring, responsi-

ble for the antibacterial and antiprotozoal activities, and anoxazolidone-ring, also known as hydrazide. They are used asantibacterial drugs in veterinary medicines. One of these

known hydrazides, finds application as an ion exchange resinsince they can react with carbonyl compounds (Strolin-Benedetti and Tipton, 1998). It has been found that metals like

copper, zinc, cobalt and iron bound to ligand containingoxygen, nitrogen or sulfur show enhanced property of antihy-pertensive drugs, antimalarial, antimicrobial, electron transfer

or any type of oxygen transport reaction (Bray and George,1985; George et al., 1986; Varadinova et al., 1993; Wasi andSingh, 1988; Tumer et al., 1999; Dolaz et al., 2009; Tumer,2000; Galal et al., 2009; Atta-ur-Rahman et al., 2001; Zhang

and Guarente, 1996), therefore, metal(II) salts were reactedwith synthesized coordinating ligand chelating from N,N sitesto bear new complexes with improved characteristics.

On the industrial scale, metal complexes of copper, nickel,cobalt and chromium have wide range of applications suchas dyes and pigments (Jeffery et al., 1978).

In the context of our current interest in methodologies forconstructing hydrazides, we envisioned a new and versatileaccess to novel chiral 2-aminobenzohydrazide (ABH). The

motivation behind the selection of ABH is to modify the basicunit diamine by replacing one of the hydrogen with that ofmethyl anthranilate moiety, thus introducing chiral centerwhich will impart bioactivity to the ABH. The chloride com-

plexes of the same category of the coordinating ligand arereported (Rehman et al., 2010). We are also interested inreporting the anion effect on the trend of bioactivities and

thermal degradation shown by the same metal.

2. Experimental

2.1. Materials and methods

All chemicals and solvents used were of Analar grade. Saltsof transition metals were obtained from Riedel-de-Haen,Germany and used without further purification. The partial

dehydration of the salts was carried out by drying the hydratedsalts in a vacuum oven for several hours at 80–100 �C. Methylanthranilate was obtained from Across Organics, USA andhydrazine monohydrate from PANREAC Quimica SA,

Barcelona, Espania. Solvents were distilled twice before use.

2.2. Instrumentation

Infrared spectra were taken in the range of 4000–600 cm�1 onPYE UNICAM Infrared Spectrophotometer using KBr disc.

The far IR spectra were examined in KBr discs in the regionof 400–200 cm�1 (FT-IR SHIMADZU).

The absorption spectra of solution of complexes in the

range of 900–200 nm employing different solvents, were ob-tained on Jasco DEC-1 Spectrophotometer with 1 cm matchedquartz cells.

Molar conductance of the solutions of the metal complexeswas determined with a conductivity meter type HI8333. Allmeasurements were carried out at room temperature with

freshly prepared solution.Magnetic susceptibilities were measured by Gouy method

at room temperature using Hg[Co[SCN]]4 as a standard (Figgiset al., 1960) leading to the calculation of magnetic moments.

Elemental analyses (carbon, hydrogen and nitrogen) weredetermined with CHN analyzer, Carloerba Model 1106 atHEJ Research Laboratories, Karachi. The cations and anions

were estimated by using analytical procedure (Jeffery et al.,1978). Melting points were recorded on Gallenkamp apparatusand reported as such. Biological activities were checked out by

the standard procedure (Atta-ur-Rahman et al., 2001).Thermoanalytical measurements were performed with

NETZSCH simultaneous thermal analyzer STA 429 in static

air. Samples were contained in an aluminum crucible Al2O3

(8 mm dia · 10 mm depth) with central base recess. The cruci-ble was then adjusted on palladium/ruthenium crucible sup-port platform, which gave proportional signal to the

recorder and computer interface to plot the weight loss of sam-ple against temperature.

2.3. Preparation of ligand

NH2

O

OCH3

HN

NH2

O

NH2

+ NH2-NH2

Reflux for 30-45min

90 0C

Methyl Anthranilate Hydrazine Aminobenzohydrazide (ABH)

According to the procedure adopted by Galal et al. (2009),

0.022 mole of methyl anthranilate was mixed with 0.022 moleof hydrazine monohydrate in a round bottom flask .The result-ing reaction mixture was refluxed at 90 �C, for 30–60 min with

a constant stirring. The glassy crystals of the ligand appearedwhen the reaction mixture was kept for about two hours in arefrigerator. Crystals were washed with n-hexane and recrys-

tallized from dry ethanol. The yield was 48%.

2.4. General procedure for the preparation of solid complexes

All complexes of 2-aminobenzohydrazide (ABH) were pre-

pared using the same general procedure. The required amountof partially dehydrated salts was dissolved in a minimumamount of anhydrous ethanol. Dehydration of the metal salts

was carried out using dimethoxy propane as dehydratingagent. The metal salt solution was stirred up for about halfan hour with desiccant in order to ensure complete dehydra-

tion. Dissolved ligand having the same mole ratio to the metalsalt, was added slowly to the dehydrated metal salt solution.During the reaction, the solution is stirred continuously. The

Synthesis, pyrolytic and bioassay studies of complexes Ni(II), Cu(II) and Zn(II) bromides 355

solid complex was obtained immediately after mixing the metalsalt solution with the ligand solution and alternatively thesame can be attained by reducing the volume of the solution

by evaporation on a rotary evaporator. The products werefiltered through sintered glass crucible, washed several timeswith n-hexane or dried ethanol and dried under vacuum.

3. Results and discussions

The ABH is characterized by elemental analysis, mass spec-

trum and NMR (proton and 13C). Elemental compositionsfor ABH and its complexes are very close to the theoretical val-ues as shown in Table 1. Elemental analysis show that the me-

tal to ligand ratio is 1:1 and the composition of metal complexis M(ABH)X2 (Where X is Cl�, Br-, and NO�3 ). The mass spec-trum of ABH shows a peak at m/Z 152 assigned to ABH+.

2

1

3

6

4

5

NH10

8

NH27

NH211

O9

The proton NMR shows two multiplets at 6.7 and 7.2 ppmcorresponding to the hydrogens of amine and that of aromatic

ring. The 13C-NMR spectrum show three singlets at 115, 150and 170 ppm for carbon atoms at position 1, 2 and 8, fourdoublets in the range of 112–125 ppm for methyne carbons

occupying positions 3, 4, 5 and 6. The doublet correspondsto the carbonyl carbon where as, singlet peaks are of aromaticcarbons. The intensity ratio is considerably in agreement withtheir population.

The ligand ABH behaves as a bidentate ligand and bearsresemblances to various diamines and their derivatives. InTable 1 are listed melting points, molar conductance and mag-

netic moment values. The molar conductance values indicatethat the complexes are non-electrolytic, chlorides are not freely

Table 1 Analytical data of ABH and their complexes.

Complexes Color C (%) H (%

C7H9N3O White 55.62 (55.62) 6.08

[Ni(C7H9N3O)Br2] Shiny green 22.50 (22.74) 2.40

[Cu(C7H9N3O)Br2] Green 22.45 (22.35) 2.42

[Zn(C7H9N3O)Br2] Off white 22.40 (22.34) 2.05

Calculated values are given in parenthesis.

Table 2 Conductance, melting points and magnetic moments data.

Complex Solvent m.p (�C) Molar cond

C7H9N3O – 93 –

[Ni(C7H9N3O)Br2] DMF 150 56.62

[Cu(C7H9N3O)Br2] DMF 140 6.311

[Zn(C7H9N3O)Br2] DMF 165 10.56

available for conductivity. The infrared spectra of the complexesshow that there is shift and broadness ofN–H frequency around3300 cm�1 therefore complexation at this point of ABH ligand

is assigned, where as one of N–H frequency and that of the car-bonyl stretching frequency remains unaltered. Hence coordina-tion is only from the 7th and 11th amine groups. The far IR

spectra show theM–X bonding. The details are given in Table 3.Magnetic moments of the complexes are reported in Table 2.

3.1. Nickel complexes

The visible absorption spectra of Ni(II) complexes (Table 4 andFig. 1) show broad peak around 17,800 cm�1 with shoulder

around 16,600 cm�1, assigned to 3T1(F) fi 3T1(P) and3T1(F) fi 3T2(F) transition probably indicating distorted tetra-hedral geometry around nickel(II). The magnetic moment(3.16 B.M) and non-electrolytic behavior of these complexes

are consistent with distorted tetrahedral symmetry of atom in[Ni(ABH)Br2].

3.2. Copper complexes

The complexes of Cu(II) show an absorption band in the re-gion 13,000–15,000 cm�1(Table 4 and Fig. 2). The envelopes

of these bands are generally unsymmetrical, seeming to encom-pass several overlapping transitions. This band is similar toabsorption maximum at 16,000 cm�1 observed in the case of[Cu(daco-diac)2X2] (Musker and Hussain, 1969). The magnetic

moment is around 1.8 B.M; which is very close to the spin onlyvalue for the unpaired electron. The conductance behaviorshows that the complexes are non-electrolytic.

3.3. Zinc complexes

The conductance data of Zn(II) complexes are typical for the

non-ionic species. Complexes of the cyclic diamines are not re-ported so far, however they can be compared with cyclic ami-dines (Musker and Hussain, 1966, 1969). In view of the well

known tendencies of Zn(II) to form tetrahedral complexessuch structure may be proposed for ABH-Zn(II) complexeswith ABH acting as bidentate ligand. This structure would

) N (%) Cation (%) Anion (%)

(6.00) 27.81 (27.80) – –

(2.45) 11.20 (11.37) 15.00 (15.88) 42.49 (43.23)

(2.60) 16.97 (16.80) 16.97 (16.50) 42.67 (42.80)

(2.41) 12.34 (11.16) 16.60 (17.37) 40.32 (42.46)

uctance (S/cm) Cor · M · 10�6 (c.g.s) leff (B.M)

– –

3997.82 3.16

1216.50 1.71

Dia-magnetic

Figure 1 Visible spectra of nickel(II) complexes with ABH

ligand in DMF.

Figure 2 Visible spectra of copper(II) complex with ABH in

DMF.

Table 3 IR spectra of ABH and the complexes (cm-1) of selected region.

Complex N–HStretching frequency C‚OStretching frequency Other bands M–Br

C7H9N3O 3330 sh 1720 m 1600, 1570 400 s

[Ni(C7H9N3O)Br2] 3390 bd 3330 w 1720 m 1600, 1570 400 s

[Cu(C7H9N3O)Br2] 3370 bd 3340 w 1720 m 1600, 1570 400 s

[Zn(C7H9N3O)Br2] 3380 bd 3330 w 1720 m 1600, 1570 400 s

sh = sharp.

m = medium.

s = small.

bd = broad.

356 Saeed-Ur-Rehman et al.

be consistent with the I.R spectra and non-electrolytic behav-

ior of the complexes.

3.4. Thermal studies

Thermal stabilities of all the complexes along with ABH werestudied by TG-DTA techniques. The thermal behavior shows

Table 4 Electronic absorption data of ABH complexes.

Complex Solvent kmax/nm

[Ni(C7H9N3O)Br2] DMF 608

[Cu(C7H9N3O)Br2] DMF 750

that the dissociation occurs in regular sequence and thermalstabilities differ significantly from one another. The same trend

in dissociation/decomposition pattern indicates no differencein their structures (Table 5). In all the complexes the patternof dissociation/decomposition is such that the ligand decom-

poses before its vaporization as complete moiety, showingthe stability of coordination moiety. Later on the remainingcomponent of the ligand vaporizes in temperature range of

250–400 oC leaving the corresponding metal halide behindwhich decomposes into its oxide at high temperature. TheDTA shows that all the vaporizations are endothermic (repre-sentative thermograms of the ligand and one of the complex

are given in Figs. 3 and 4. The thermal behavior of the ligandand its complexes may be summarized by the following set ofequations.

ABH! CO2 þH2OþNO

MðABHÞBr2 ! ABHþMBr2

MBr2 þO2 ! Br2 þMO

Irving William trend is observed for the thermodegradativebehavior of the coordination complexes irrespective of the nat-ure of the ligand as can be depicted from Figs. 5 and 6 (Irving

and Williams, 1953). A publication based on thermal behaviorand activation energies is the subject of an independent com-munication in near future.

3.5. Bio-assay investigations

The complexes of ABH were investigated for their bioactivity

against various available microorganisms. These microorgan-isms include gram positive and gram negative bacteria alongwith a selected species of fungi. Gram Negative bacteria in-clude Escherichia coli, Salmonella typhi, Enterobacter aeroge-

nes, Proteus vulgaris and Pseudomonas aeruginosa, selectedgram positive bacterial strain is Staph aureus and fungus likeCandida albican.

These studies show that the metal complexes become morebiologically active as compared to neat organic moiety. The re-sults are reported in Table 6.

Bioactivities were investigated using agar-well diffusionmethod (Atta-ur-Rahman et al., 2001). Two to eight hours

t/cm�1 n/dm3/mol. cm Comments

14,300 180 3T1(F) fi 4T1(P)

13,300 180 d fi d

Figure 3 TGA/DTA of ABH ligand.

Figure 4 TGA/DTA of Zn(ABH)Br2.

Figure 6 Irving William trend for percent mass loss during

thermal decomposition. Where I, II and III are different stages of

decomposition.

Table 5 Thermoanalytical results for the ligand and its complexes.

Compound DTA peak temperature/oC TG Mass loss (%) Phenomena

Temperature range/�C calc. Found

ABH 270(–) 150–270 100 99 CO2H2O & NO

[Ni(C7H9N3O)Br2] 100(–) 150–210 12.50 12.86 C4H2

380(–) 280–400 18.75 19.00 N3H5CO

600(–) 400–700 43.12 43.00 Br2>700 20.20 17.54 As NiO

[Cu(C7H9N3O)Br2] 100(–) 150–200 13.35 12.90 C4H2

390(–) 270–400 20.265 19.50 N3H5CO

600(–) 400–700 42.10 43.00 Br2>700 18.75 17.54 As CuO

[Zn(C7H9N3O)Br2] 100(–) 150–200 13.29 13.20 C4H2

370(–) 270–400 19.94 19.00 N3H5CO

600(–) 400–700 42.55 40.00 Br2>700 21.54 19.50 As ZnO

Figure 5 % Mass loss of ABH derived transition metal

complexes at different stages of varying temperature. Where I, II

and III are different stages of decomposition.

Synthesis, pyrolytic and bioassay studies of complexes Ni(II), Cu(II) and Zn(II) bromides 357

old bacterial strains in column containing approximately 104–106 colony forming units (CFU)/mL were used in these assays.

The wells were dug in the media with the help of a sterilemetallic borer with centers at least 24 mm. Recommended con-centration (100 ll) of the test sample 1 mg/mL in DMSO was

introduced in the respective wells. Other wells supplementedwith DMSO and reference antibacterial drug, impeniumserved as negative and positive controls, respectively. Theplates were incubated immediately at 37 �C for 20 h. Activity

was determined by measuring the diameter of zones showingcomplete inhibition (mm). Growth inhibition was comparedwith the standard drug. In order to clarify any participatingrole of DMSO in the biological screening, separate studies

Table 6 Biological activities of complexes against gram negative, gram positive and fungus.

Compound E. coli Staph aureus Salmonella typhi Enterobacter aerogenes Proteus vulgaris Pseudomonas aeruginosa Candida albican

Gentamycin 21 38 35 31 39 28 22

ABH 14 17 16 12 14 13 14

[Ni(C7H9N3O)Br2] 14 28 18 20 14 26 32

[Cu(C7H9N3O)Br2] 13 15 17 19 20 12 14

[Zn(C7H9N3O)Br2] 12 14 16 20 15 17 15

Gram negative: E. coli, Salmonella typhi, Enterobacter aerogenes, Proteus vulgaris and Pseudomonas aeruginosa.

Gram positive: Staph aureus.

Fungus: Candida albican.

358 Saeed-Ur-Rehman et al.

were carried out with the solutions alone of DMSO and theyshowed no activity against any bacterial strains. All these com-plexes were found to be potentially active against these bacte-

rial strains. It is evident that the overall potency of the ligandwas enhanced on coordination.

4. Conclusion

The synthesized complexes of ABH possess the composition,M(ABH)X2 and show tetrahedral geometries.

(I) The percent thermo-oxidative decomposition was obser-ved and found according to the Irving William Series.

(II) All the coordination compounds were found to beexhibiting the same trend of thermal decomposition;only differ in temperatures to a small extent due to var-

iation in metal center going from cobalt to zinc.(III) The synthesized hydrazine derived ligand has showed

antibacterial/ antifungal properties. Comparatively, thecopper(II), nickel(II) and zinc(II) metal complexes of

this compound were more active against one or morebacterial/fungal strains, thus giving rise to a novel classof metal-based bactericidal and fungicidal agents.

(IV) It is concluded that there is no exact sequence observedfor the biological studies but copper and nickel com-plexes were found to be potentially strong in inhibition

of microbial activities.

Acknowledgment

We are grateful to Higher Education Commission, Pakistanfor providing the fund to conduct this research work. HEJResearch Institute of Chemistry, University of Karachi,

Pakistan,are gratefully acknowledged for the instrumentalfacility of Mass spectroscopy. Thanks are due to ChemistryDepartment, Quaid-i-Azam University, Islamabad for extend-ing NMR instrumentation of samples. Our gratitude also goes

to the Department of Environmental Sciences, University ofPeshawar for availing their FTIR facility.

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