Synthesis , Characterization and Antifungal Activity of Novel Quinazolin-4-one Derivatives Containing 8-Hydroxyquinazoline Ligand and its Various Metal Complexes

Novel ligands containing quinazoline-4-one-8-hydroxyquinoline (QQ) merged moieties were prepared and characterized. For this anthranilic acid and 5bromoanthranilic acid were converted respectively into 2-chloromethyl–3-(4-methyl phenyl)-3(H)-quinazoline-4-one and 2-chloromethyl–3-(methyl phenyl)-6-bromo3(H)-quinazoline-4-one. Both these compounds were condensed with 5-amino-8hydroxyquinoline. The so called resulted compounds were named respectively as 2[(8-hydroxy-quinolinyl) –5amino methyl] -3-(4-methylphenyl)3(H)quinazoline 4one and 2-[(8-hydroxyquinolinyl)-5-aminomethyl] -3(methyl phenyl)-6-bromo3(H)-quinazoline-4-one. Both the compounds were designated respectively as HL1 and HL2 ligands. The transition metal (Cu , Ni, Zn, Mn and Co) complexes of both these ligands were prepared. The ligands and their complexes as case may be were characterized by elemental analysis, spectral studies and number of hydroxyl groups. The stoichiometry of the complexes has been found to be 1:2 (metal: ligand). An octahedral geometry around Co, Ni and Mn, distorted octahedral geometry around Cu and tetrahedral geometry of around Zn have been proposed. These complexes also been tested for their antifungal activities.


Introduction
The heterocyclic nitrogen compounds especially quinazolinone derivatives play a vital role in many biological processes and as synthetic drugs [1][2][3] .Quinazolin-4-one is also well known for many pharmaceutical products [4][5][6] .Ligand 8-hydroxyquinoline is not only act as a complexing agent but also applied for drug synthesis 7 .The formation of 8-hydroxyquinoline and quinazolin-4-one molecules into one molecule has not received any attention in spite of well-defined applications of both the molecules.Hence the initial work in this direction has been carried out 8 .Thus in the extension of this work 8 , present communication comprises the synthesis, characterization and chelating properties of novel qunazolin-4-one-8-hydroxyquinoline derivatives.The whole work is summarized in Scheme 1.

Experimental
All the chemicals used were of pure grade (Merck and B.D.H).The melting points of both ligands HL 1 and HL 2 were determined by DSC method and were uncorrected.

Synthesis of complexes
A dried ligand sample HL 1 or HL 2 (0.01 M) was stirred in 85 % (v/v) formic acid and then it was diluted by water until complete dissolution.The resultant solution was designated as reagent solution.This solution was used for preparation of complexes with transition metal ions.The formic acid solution of ligand was added drop wise to a solution of cupric nitrate hexahydrate, nickel nitrate hexahydrate, cobalt nitrate hexahydrate, manganese chloride hexahyrade, zinc nitrate hexahydrate (0.005 mole) in 100 mL of water respectively with rapid stirring.The resultant pH 4.5 (for Cu +2 ), pH 6.0 (for Ni +2 and Co +2 ) and pH 5.6 (Mn +2 and Zn +2 ) was maintained by adding of sodium acetate.A dark coloured solid was precipitated out.It was allowed to settle and digested on water bath at 70 °C for about 2 h.The solid mass was filtered, washed with 1:1 mixture of water-ethanol and finally with acetone and dried.The percentage yield of complexes was in the range of 65-82%.All the complexes were powdered well and dried at 70 °C over a period of 24 h.

Measurements
The C, H and N contents of metal complexes were determined on elemental analyzer Thermofiniggan 1101 Flash EA (ITALY).The metal contents were estimated using standard methods 9 . 1 H NMR spectra of ligands were recorded on Bruker NMR spectrophotometer using TMS as an internal standard in CDCl 3 /DMSO-d 6 10 .The molar conductance of the complexes in DMF (10 -3 M) solutions were measured at room temperature using Systronics model 305 direct reading conductivity bridge.The infrared spectra (KBr) were recorded in the range 4000-600 cm -1 with a Nicolet-760 spectrophotometer.Reflectance spectra of complexes were recorded on a Beckman-DK-2A spectrophotometer using MgO as reference.Magnetic susceptibility was measured by Gouy's method 11 at room temperature (300 K) using Hg[Co(CNS) 4 ] as calibrant 12 , and the effective magnetic moment were calculated from relation 13 , µ eff = 2.84√Xm x T, where T is the absolute temperature.Diamagnetic corrections were made by using Pascal's constants.
The ligands and their metal complexes were screen at 1000 ppm concentration in vitro for their antifungal activity against five fungi viz.Erysiphe pisi, Nigrospora sp., Trichoderma sp., Aspergillus niger, Curvularia lunata.The antifungal activity of the compounds was measured by plate method.Five days old cultures were suspended in potato dextrose agar (PDA) medium and autoclaved at 1200 °C for 15 minutes at 15 atmospheric pressure.The percentage inhibition of fungi was calculated after 5 days using the formula given below, Percentage of Inhibition = 100 (X-Y) / X Where X = area of colony in control plate (without sample) and Y = area of colony in test plate.

Results and Discussion
The synthesis of ligands HL 1 and HL 2 was performed by method reported for 2-chloromethyl-3-(4-methylphenyl)-3(H)-quinazoline-4-one.The C, H and N of both ligands are consistent with predicted structure.

NMR spectra
The The complexes are microcrystalline coloured powders having melting points higher than the ligands.They are stable in air at room temperature.All compounds gave satisfactory elemental analysis, suggesting 1:2 (metal:ligand) stoichiometry.Elemental and molar conductance data are shown in Table 1.The result indicates that they are less polar in DMF.Very low molar conductance values in the range of 5.11 to 21.72 ohm -1 cm 2 mol -1 in Mn 2+ , Ni 2+ , Cu 2+ and Zn 2+ complexes indicates that they are non-electrolytic 14 and monomeric in nature (ML 2 type complexes).The low Λ M values may be attributed to the large cations 15 .The electrical conductivity of these complexes found in the decreasing order as follows: Co > Ni > Zn > Mn > Cu.

Infrared spectra
IR spectrum of ligands HL 1 and HL 2 show a broad band extended from 3700 to 2600 cm -1 which might be responsible to phenolic -OH group bonded to N atom of 8-hydroxyquinoline moieties [16][17] .The inflextious at 2920, 2850 and 1470 cm -1 are due to aromatic -CH 2 and methylene group of bridge [18][19] .The strong band at 1700 cm -1 is attributed to -C=O of quinazoline 4-one moiety.Band at 3400 cm -1 for -NH group.Several bands appeared between 1500-1600 cm -1 region may arised from aromatic breathing.The IR band at 1580 cm -1 (C=N of 8-quinolinol system) of HL 1 and HL 2 ligands shifted to higher frequency side ~1600 cm -1 in the spectra of the metal complexes indicating involvement of nitrogen in the complexes formation 16,20 .Most of bands appeared in the spectra of corresponding ligand are observed at their metal complexes.Only a new band at 1095 cm -1 had appeared in the spectra of metal complexes.This may be assigned to υc-o of C-O-M bond formation.All the complexes show additional bands at 840-830 cm -1 indicating the presence of coordinated water 21 .

Magnetic moment and electronic spectra
At the room temperature, µ eff values for the Co +2 complexes (3.99-4.51B.M.) suggest high spin octahedral geometry, which is further supported by the electronic spectral data.The electronic spectrum of the Co 2+ complexes shows three bands at 8960, 18650-18980 and 22590-23710 cm -1 , assignable to 4 4 T 1g (F) 4 T 1g (P) (υ 3 ) transitions, respectively for an octahedral geometry 22 .The values of transition ratio υ 2 / υ 1 is 2.08 providing further evidences for octahedral geometry for the Co 2+ complexes.
In the Ni +2 complexes, µ eff values at room temperature are in the range 2.97-3.12B.M. as expected for six coordinated spin free Ni +2 species 23 .The reflectance spectra of the Ni 2+ complexes, exhibit two strong bands at 15620-15625 cm -1 and 22470-22478 cm -1 , assignable to 3 A 2g (F) 3 T 1g (F) (υ 1 ) and 3 A 2g (F) 3 T 1g (P) (υ 2 ) respectively.The spectral bands are well within the range observed for hexacoordinate octahedral complexes reported earlier 24 .The Cu +2 complexes exhibit normal magnetic moments (1.70-1.81B.M.) corresponding to one unpaired electron indicating the distorted octahedral geometry, which is in agreement with data reported by several research workers [25][26] .Electronic spectra of these complexes show broad asymmetric bands in the region 14980-15490 cm -1 and at 23690-24650 cm -1 assignable 2 B 1g 2 A 1g and charge transfer transition respectively 27 .These results reveal the distorted octahedral geometry for these complexes.The former band may be due to 2 E g 2 T 2g accounted due to Jahn Teller effect suggesting thereby a distorted octahedral geometry for these complexes 28 .Zn +2 complexes are diamagnetic in nature and their electronic spectra do not furnish any characteristic d-d transitions except charge transfer (C.T.) bands as expected for d 10 systems and may have tetrahedral geometry 29 .There is no evidence for the characteristic bands of coordinated water in IR spectra.

Antifungal activity
All the ligands and their complexes are found toxic more or less against fungi.HL 2 was more toxic than HL 1 .Off all the complexes Copper complex exhibit more toxicity than other metal complexes against fungi.These results are in agreement with the result obtained by the work of Patel I. J and Vohra I. M 33 .Hence such type of complexes may find as agricultural and garden fungicides.

Conclusion
• The ligand molecule acts as a hexadentate ligand in all the studied cases of complex.Bon ding either among N(4) depending upon the nature of the metal ions.• Octahedral structures for Ni 2+ , Co 2+ and Mn 2+ complexes, tetrahedral polymeric structure for Zn 2+ and distorted octahedral for Cu 2+ complex have been tentatively proposed.Present work will contribute in the field of new antifungal for some plant pathogenic organisms.
1H NMR spectra of both ligands gave the multiplate between 6.88-7.8δ ppm for aromatic protons, signal at 5.74-5.98δ ppm for singlet of phenolic -OH group, 3.35-3.77δ ppm due to CH 2 bridge, 1.23 d ppm for -CH 3 group and 11.1-11.35δ ppm due to -NH group.The non-aqueous conductometric titration at both ligands gave the proton of -CH 2 and -OH group in ligands.

Table 1 .
Analytical and physical data of ligand and complexes.