SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF MANGANESE(II) AND NICKEL(II) COMPLEXES OF 7- DIETHYLAMINOBENZYL-8-HYDROXYQUINOLINE

4324 | P a g e F e b r u a r y 0 2 , 2 0 1 6 SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF MANGANESE(II) AND NICKEL(II) COMPLEXES OF 7DIETHYLAMINOBENZYL-8-HYDROXYQUINOLINE C.Muthukumar , A.Sabastiyan, S.Valarselvan, M.Subramanian, M.Shanmugavadivel *a Dept.of Chemistry,J.J.College of Arts and Science(Autonomous), Pudukkottai-622 422 cmkumar72@gmail.com b Dept.of Chemistry,Shivani Engineering College, Tiruchirappalli-620 009 c Dept.of Chemistry,H.H.The Rajh’s College, Pudukkottai – 622 001 msninfonet@gmail.com Abstract


Introduction
Synthetic chemists and pharmacologists show much interest in heterocyclic compounds containing quinoline moiety because of their unique chemical and pharmacological properties (Balasubramanium M and Keay, JG, 1996;Micheal IP, 1997; Maguire M P et al, 1994 al., 1981) such as antiinflammatory, antibacterial, antifungal, antiallergic, antidepressant, antiasthmatic, antimalarial, antiviral, antitumour, neuroleptic, antihypertensive, cytotoxic, hypnotic, sedative,bronchodilator etc activities.8-Hydroxyquinoline is toxic if injected directly but its derivatives are useful as medicine in view of their biological activities . 8-Hydroxyquinoline is much useful in analytical chemistry also due to its chelating ability (Bassett J et al, 2000).When 8-hydroxyquinoline is subjected to Mannich condensation with aldehydes and secondary amines it yields Mannich bases which could display more potent pharmacological properties and also stronger chelating tendencies. Mannich base coordination chemistry has been a popular area of research due to the diverse range of biological, analytical and industrial applications of the Mannich base metal chelates (Sathya et

Materials and Methods
All the chemicals and solvents used were AR grade products. The microelemental analyses were performed using Carlo Erba 1108 CHN analyzer. Metals and anions were estimated by conventional wet chemical analyses. Molar conductivities were measured in ~ 10 -3 M DMF solutions at room temperature using Systronics Conductivity Meter 304. FT-IR Spectral measurements were made with Perkin -Elmer Spectrum -1 FT-IR Spectrometer as KBr pellets. Mass spectra were recorded using JEOL D-300 (EI) Mass Spectrometer. 1 H NMR and 13 C NMR spectra were recorded on JEOL GSX-400 FT NMR Spectrometer (400 MHz) employing TMS as internal reference and DMSO-d6 as solvent. Electronic absorption spectra were measured in DMF solutions using Perkin -Elmer EZ301 Spectrophotometer. Magnetic susceptibility measurements were made on a Gouy magnetic balance at room temperature using Hg[Co(SCN)4] as calibrant. Simultaneous TG/DTA/DTG thermograms were recorded in the admosphere of air on a Perkin-Elmer Thermal analyzer.

Preparation of Mn II and Ni II complexes of DEBQ
The Mn II and Ni II complexes were isolated by interacting the respective hydrated metal salt (0.01 mole) with the ligand DEBQ(0.01mole) in hot ethanolic medium. The precipitated metal complexes were filtered, washed with ethanol and dried in a hot air oven at ~70 0 C.

Invitro antimicrobial screening
Antimicrobial screening of the organic ligand and its metal complexes was carried out by agar well diffusion technique (Cruickshankt R,1975). S.aureus and E.coli were the bacterial strains and P.Chrysogenum and A.niger were the fungal species employed. The concentrations of test samples in DMSO solutions were 50 and 100 µg/mL. Antimicrobial activities of samples were determined by measuring the diameters of zones of inhibition (mm) in Muller Hinton agar medium after 24 hours of incubation for bacterial species and after 48 hours of incubation for fungal species. All the experiments were performed in triplicate. Growth inhibition produced by a particular sample was compared with that of the standard bacterial drug ampicillin and that of standard fungal drug amphotericin-B. Based on these physico-chemical data, the structure of DEBQ is confirmed as given in Figure 1.

Structural characterization of metal complexes
The analytical and conductivity data of the metal complexes of DEBQ are provided in Table1. These data indicate that the isolated metal complexes have 1:1 stoichiometry and are non-ionic in behaviour (Greay WJ, 1971). Further, the mass spectrum of the Ni II sulphato complex( Fig.2) registers the molecular ion peak at 461,which indicates 1:1 stoichiometry for the same. The non-electrolytic behaviour of metal complexes suggests the bonding of anions to the respective metal ion in the complex species.   Table 2.A broad absorption at 3392cm -1 is attributed to the presence of a phenolic OH group in the quinoline moiety of the organic ligand. In the vibrational spectra of the Mn II and Ni II metal complexes, this band appears split and shifted to 3383-3326cm -1 region predicting the coordination of the phenolic oxygen atom to the metal ion. Normally when an aqueous solution of a 8hydroxyquinoline derivative is added to an aqueous solution of the metal salt, the quinoline N and ionized phenolate O chelate to the metal ion to precipitate the coordination compound. But in the precent study, the complex preparation was attempted in an ethanolic medium and the ionization of the phenolic OH in to O was not possible.Also the presence of anionic groups such as Cl -,NO3 and SO4 2in the complex species excludes the existence of phenolate anion in the coordination compounds. Further the pyridine ring vibrations which are usually observed at about 604cm -1 (inplane ring deformation) and 405cm -1 (out of plane ring deformation) have not shifted to high frequencies in the spectra of the complexes indicating non -involvement of the pyridine ring nitrogen atom in coordination The ligand absorption bands observed at 1284-1275cm -1 are ascribed to the C-N-C stretching vibrations of the diethylamino moiety. But in the IR spectra of the metal complexes, these vibrations have shifted to a lower region of 1273-1208cm -1 pointing to the bonding of the aliphatic tertiary amino nitrogen atom to the metal ion. The coordination of a tertiary amino nitrogen is not sterically favourable, but the possibility of chelation tends to its coordination to a metal ion. Further the existence of new non-ligand bands in the regions 606-529cm -1 and 526-420cm -1 which indicate νMO and νMN vibrations respectively also predict the bidentate coordination of the Mannich base ligand through the phenolic OH group and the diethylamino nitrogen atoms. The nitrato groups in Mn II complex exhibit vibrations at 1575(ν5),1371(ν1)and 1031cm -1 (ν2). The very high separation between ν1 and ν5 peaks(204cm -1 ) confirms the bidentate chelation of nitrato groups. But in the nickel(II) nitrato complex the corresponding vibrations are found at 1462,1384 and 1033cm -1 . The very low separation between ν5 and ν1(78cm -1 ) confirms the unidentate behaviour of nitrato groups.

Magnetic and electronic spectral studies
The colours, magnetic moments and the electronic absorptions (Lever ABP,1968) of the Mn II and Ni II complexes are summarized in Table 3  the tetrahedral stereochemistry for the Ni II chloro complex.The Ni II nitrato complex is also blue in colour and shows electronic absorption bands at 3860,8370,15100 and 28820cm -1 and these absorption are attributed to 3 T1(F)→ 3 T2(F), 3 T1(F)→ 3 A2(F), 3 T1(F)→ 3 T1(P) and CT transitions respectively. The ν2/ν1, ratio for the nitrato nickel(II)complex is also with in stipulated range for the tetrahedral geometry. The Ni II sulphato complex measures absorptions at 3990, 8720, 15207 and 28490cm -1 which are attributed to 3 T1(F)→ 3 T1(F), 3 T1(F)→ 3 A2 (F), 3 T1(F)→ 3 T1(P) and CT respectively. The ν2/ ν1 ratio for this complex is measured at 2.185 which is within the stipulated range for the tetrahedral geometry. Hence the Ni II sulphato complex is assigned a tetrahedral geometry on the basis of the electronic spectrum.

Thermal decomposition Ni(NO 3 ) 2. DEBQ
Ni(NO3)2.DEBQ also displays a two stage thermal decomposition as shown in Figure 7. The compound experiences a small weight loss in the beginning of heating due to loss of adsorbed water. The dry complex is stable upto 180 0 C and it decomposes in the temperature range 180-325 0 C. This first stage of decomposition involves elimination of DEBQ and the formation of Ni(NO3)2. as the intermediate. This decomposition is evidenced by the DTG peak centered at 245 0 C. The intermediate Ni(NO3)2 undergoes further decomposition(second stage) to produce NiO as the final residue. The decomposition of Ni(NO3)2 to produce NiO is supported by the DTG peak centering at 514 0 C. The weight of the final residue is found to be at 16% of the original anhydrous complex. In this thermal decomposition study also the DTA pattern is not useful to follow the information given by TG. F e b r u a r y 02, 2016

Antimicrobial studies
The Mannich base ligand (DEBQ) and its Mn II and Ni II chloro complexes have been screened for antimicrobial activity against E.coli, S.aureus, A.niger and P.chrysogenum. The levels of antimicrobial activity in terms of the zones of inhibition produced by the test compounds are presented in Table 4. The Mannich base is highly active against both the bacterial and the fungal strains tested. The Mannich base ligand exhibits comparable activity with the standard antibacterial drug used (ampicillin). But antifungal activity the Mannich base is more potent than that of standard drug (amphotericin -B). It shows that this organic compound may very well be used as an antifungal antibiotic. The mangese(II) complex exhibits more significant activity than the nickel(II) complex against both the bacterial and the fungal organisms tested.  Table 4 Antimicrobial activity of DEBQ and its metal chloro complexes

Conclusion
Manganese(II) and nickel(II) ion complexes of 7-diethylaminobenzyl-8-hydroxyquinoline have been synthesized and their spectral, thermal and antimicrobial properties have been investigated. Though this ligand has several binding sites it prefers to coordinate to the metal ion through the phenolic oxygen and the diethylamino nitrogen atoms. The structures of the coordination compounds prepared have been established based on analytical and spectral data as shown in Figures  3a-c and 4. From antimicrobial screening studies it is concluded that the Mannich base ligand is possessing more significant activity than the metal complexes as well as the standard drugs employed . Among the coordination compounds investigated manganese(II) complex is more active than nickel(II).The complexes undergo two stage thermal decomposition to form metal oxides as final residues.