Synthesis, Characterization and Chelating Properties of Benzoxazolidin-2-one/ 4 - aminosalicylic Acid Clubbed Molecule. Part – I

: Aminomethylation of benzoxazolidin-2–one was carried out by treating benzoxazolidin-2–one with formaldehyde and 4 – aminosalicylic acid. The resultant compound was designated as 3–(4-carboxy–3 - hydroxyphenyl aminomethyl) benzoxazolidin-2-one (CHPA-BOX) The transition metal complexes of Cu 2+ Co 2+ Ni 2+ , Mn 2+ , Zn 2+ , UO 2+ and Fe 3+ of CHPA-BOX have been prepared. Elemental analyses, spectral studies, magnetic moment determination, molar conductivity measurement and microbial activity of CHPA-BOX and its metal complexes were carried out.


Introduction
Benzoxazolidin-2-one is found as an important heterocyclic compound.It is versatile compound and finds many derivatives for pharmaceutical applications [1][2][3][4][5] .Its amino methylation (i.e.Mannich reaction) has been carried out successfully by Indian scientists 6 .The area in which the amiono methylation of benzaxozolidin -2 -one by using aromatic amine having metal gripping group (i.e.ligand) has not been developed.Hence it was thought to undertake such work.With this view, the present communication describe the synthesis and characterization of benzaxoazolidin-2-one 4-amino salicylic acid clubbed molecule and its metal complexes.The work is illustrated in Scheme -1.

Materials
Benzoxazolidin-2-one was prepared by method reported in literature 7 .p-Amino salicylicacid (PAS) (i.e.4-Aminosalicylic acid) was obtained from local dealer.All other chemicals used were of analytical grade.

Synthesis of metal complexes of CHAP -BOX Formation of CHAP-BOX metal complexes
The Cu 2+ ,Co 2+ , Ni 2+ ,Mn 2+ , Zn 2+ ,UO 2+ and Fe 3+ metal ion complexes of CHAP-BOX have been prepared in a similar manner.The procedure is as follow.
To a solution of CHAP-BOX (0.1 mole) in ethanol-acetone(1:1) mixture (150ml), 0.1 N KOH solution was added drop wise with stirring.The pasty precipitates were obtained at neutral pH.These were dissolved by addition of water up to clear solution.It was diluted to 250 ml. by water and was known as stock solution 25 ml of the stock solution (which contains 0.01 mole CHAP-BOX) was added drop wise to the solution of metal salt (0.005 mole for divalent metal ions and 0.0033 mole for Fe 3+ ion) in water at room temperature.Sodium acetate or ammonia was added up to complete precipitation.The precipitates were digested on water bath at 80 o C for 2 h.The digested precipitates of complex were filtered washed with water and air dried.It was amorphous powder.Yield was almost quantitative.The details are given in Table-1.

Measurements
The elemental analysis for C, H and N were carried out on elemental analyzer.IR spectra of CHAP-BOX and its metal complexes were scanned on a Nicolet 760FTIR spectrophotometer in KBr.The metal content of the metal chelate were performed by decomposing a weighed amount of each metal complexes followed by EDTA titration as reported in literature 8 .Magnetic susceptibility measurement of all the metal complex was carried out at room temperature by the Gouy method.Mercury tetrathiocynatocobaltate (II) Hg [CO (NCS) 4 ] was used as a calibrant.The diffused reflectance spectra of solid metal complex were recorded on a Backman DK Spectrophotometer with a solid reflectance attachment, MgO was employed as the reflectance compound.The electrical conductivity of all the complexes was measure in CH 3 CN at 10 -3 M concentration.

Antifungal activity
The fungicidal activity of all the compounds were studied at 1000 ppm concentration in vitro.Plant pathogenic organisms listed in Table -3 were used.The antifungal activity of all the samples were measured by cup plate method 9 .Each of the plant pathogenic strains on a potato dextrose agar (PDA) medium.Such a PDA medium contained potato 200gms, dextrose 20gms, agar 20gms, and water 1 litre.5 days old culter were employed.The compounds to be tested were suspended (1000 ppm) in a PDA medium and autoclaved at 120 o C for 15 min.at 15 atm pressure.These medium were poured into sterile petri plate and the organisms were inoculated after cooling the Petri plated.The percentage inhabitation for 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 Y : Area of colony in test plate The fungicidal activity all compounds are shown in Table -3

Results and Discussion
The parent ligand CHAP-BOX was an amorphous yellow powered, soluble in various solvents like dioxane, DMSO and DMF.The results of elemental analysis of the ligands are reported in Table-1.They are consistant with the predicted structure as shown in Scheme-I the ligand was synthesized as shown in the Scheme-1.
Examination of IR spectrum (not shown) of CHAP-BOX reveals that a broad band of phenolic hydroxyl stretching is observed at 3200-3600 cm -1 as well as additional absorption bands at 3030, 1500 and 1600 are characteristics of the salicylic acid 10,11 The strong bands at 1680 for C=O and band at 3400 for sec.NH.The NMR data (shown in experimental part) also confirm the structure of CHAP-BOX.
The Metal complex of CHAP-BOX with the metal ions Cu 2+ , Co 2+ , Ni 2+ , Mn 2+ , Zn 2+ , Fe 3+ , UO 2 2+ vary in colours.On the basis of the proposed structure as shown in scheme-1, the molecular formula of the CHAP-BOX ligand is C 15 H 12 O 3 N 2 Which upon complexion coordinates with one central metal atom at four coordination sites and with two water molecules.Therefore the general molecular formula of the resulting metal complex is [C 15 H 11 O 5 N 2 ] 2 M.2H 2 O for divalent metal ions.This has been confirmed by results of elemental analysis of all the seven metal chelates and their parent ligand.The data of elemental analysis reported in Table-1 are in arrangement with the calculated values of C, H and N based on the above mentioned molecular formula of parent ligand as well as metal complex.The electrical conductivity (Table-1) of these complexes in acetonitrile indicate that the complexes are essentially non electrolytes.Inspection of the IR Spectra (not shown) of metal complexes reveals that all the spectra are identical in all respects.The comparison of IR spectrum of the parent ligand CHAP -BOX with that of its each metal complex has revealed certain characteristics differences.
1][12] .This is explaind by the fact that water molecules might have strongly absorbed to the metal chelates sample during their formation.Another noticeable difference is that the bands due to the COO -anion at 1600 cm -1 in the IR spectrum of the each metal complex.The band at 1400 cm -1 in the IR spectrum of HL assigned to inplane OH determation [10][11][12] is shifted towards higher frequency in the spectra of the metal complex due to the formation of metal oxygen bonds.This has been further confirmed by a week bands at 1105 cm -1 corresponding to C-O-M starching [10][11][12] .Thus all of these characteristics features of the IR studies suggested the structure of the metal complex as shown in scheme.
Examination of data of the metal content in each compound revealed a 1:2 metal: ligand (M:L) stoichiometry in all of the complex of divalent metal ions and 1:3 metal : ligand stoichiometry for Fe 3+ ions.
Megnetic moment (µ eff ) of each of the metal complex is given in Table -2.Examination of these data reveals that all complexes other than that of Zn 2+ and UO 2 2+ are para magnetic while those of Zn 2+ and UO 2 2+ are diamagnetic.The diffuse electronic spectrum of the [Cu HL (H 2 O) 2 ] metal complex shows broad bands at 15870 and 24690 cm -1 due to the 2 T 2 T 2g transition and charge transfer, respectively suggesting a distorted octahedral structure [13][14][15] 6 A 1g 4 T 1g (4G), 6 A 1g 4 T 2g (4G) and 6 A 1g (F) 4 T 1g , respectively suggesting an octahedral structure for the [Mn HL (H 2 O) 2 ] chelate.The spectrum of Fe 3+ complex has not been adequately characterized.The spectrum comprised the band ground 19002 cm -1 and other weak band ground 23006 cm -1 .The latter has not very long tail.These may have the transitions 6 A 1g 4 T 2 (4G) and 6 A 1 4 T 1 (4G).The high intensities of the bands suggests that they might be charge transfer in origin µeff is found to be lower than normal range.In the absence of low temperature moments it is difficult to give any significance.As the spectrum of the [Zn HL (H 2 O) 2 ] polymer is not well resolved, it is not interpreted but it is µ eff value shows that it is diamagnetic as expected.
Conductivities of all the complexes were measured in acetonitrile solvent and all the complexes were found to be electrolytic 16  The antifungal activity of all the compounds measured for various plant pathogens.Inspection of the result shown in Table-3 indicates that all compounds are good toxic for fungi.Out of all the compounds copper chelates is more toxic than other.These compounds almost inhibit the fungi about 70%.Hence produced metal chelates can be employed as garden fungicides.Further work in the direction is in progress.
in nature of 1:2 type and molar conductivity values are in the range of 121-152 Ohm -1 Cm 2 mol -1 .

Table 1 .
Analytical Data of the Metal Chelates of HL 1 (i.e.Q CHPA -BOX)

Table - 2
Magnetic Moment & Reflectance Spectral data of the Metal Complexes.