a sustained research activity has been devoted to lanthanide complexes , because 
 of their successful application as diagnostic tools in biomedical analysis as 
 mri contrast agents [ 1 , 2 ] .
they have been used even as effective catalysts   for the hydrolytic cleavage of phosphate ester bonds .
4(4h)-quinazolines have been tested successfully against cancer and hiv virus [ 5 , 6 ] .
the synthetic analogues of quinazolines have been found to exhibit antimalarial , anti - inflammatory , and anticancer activity .
apart from the above , 2,3-disubstituted quinazoline-4-(3h)-ones have been reported for their wide variety of 
 pharmacological activity [ 12 , 13 ] .
the title ligand hmpbaq possesses multiple coordinating sites such as phenolic oxygen , carbonyl oxygen , nitrogen of the benzoyl amino group , and nitrogen of the quinazoline ring .
we have observed its tridentating behavior with transition metal ions . in continuation of our work on quinazolines , here we report the conformational changes in the ligand on coordination with lanthanides and the relative antimicrobial activity .
hydrazine hydrate , methyl 2-aminobenzoate , and o - vanillin were procured from rankem , merck , and himedia , respectively .
the lanthanide nitrates were obtained by heating lanthanide oxides ( 99.9% ) ( indian rare earths limited , 
 mumbai , india ) with dilute nitric acid ( 50% ) and evaporating the excessive acid . 

synthesesthe ligand hmpbaq was synthesized as in our earlier report   ( see scheme 1 ) .
a solution of ln(no3)3 ( 1 mmol ) and hmpbaq 0.838 gm ( 2 mmol ) was refluxed in ethanol ( 25 ml ) for 2 - 3 hours .
the ph of the solution was then raised to 6.5 by the addition of sodium acetate and refluxed further for an 
 hour .
the precipitate obtained after concentrating the solution was filtered off , washed with water , and dried in air ( yield : 90% , mp 
 > 245 
 c ) . 
 
the ligand hmpbaq was synthesized as in our earlier report   ( see scheme 1 ) .
a solution of ln(no3)3 ( 1 mmol ) and hmpbaq 0.838 gm ( 2 mmol ) was refluxed in ethanol ( 25 ml ) for 2 - 3 hours .
the ph of the solution was then raised to 6.5 by the addition of sodium acetate and refluxed further for an 
 hour .
the precipitate obtained after concentrating the solution was filtered off , washed with water , and dried in air ( yield : 90% , mp 
 > 245 
 c ) .
elemental analysis was performed on a carlo erba strumentazione ( milan , italy ) 
 chn analyzer .
ir spectra were obtained on a nicolet 170 sx ft - ir spectrometer 
 using kbr pellets , in the range 4004000 cm . 

h- and c nmr spectra were monitored on a jeol - amx-400 nmr spectrometer , using dmso - d6 as the solvent .
tg / dta were recorded on a perkinelmer ( mass , usa ) ( pyris diamond ) analyzer in n2 atmosphere at a heating rate of 
 10c .
mass spectra of the ligand and complex were recorded on a thermofinnigan 1020-automated gcms and jeol sx 102/da-6000 mass spectrometer / data system using argon and xenon 
 ( 6 kv , 10 ma ) as the fab gas , respectively .
epr spectra of the gd(iii ) and tb(iii ) complexes were monitored on a varian e-4x band spectrometer .
the metal contents were determined by complexometric titrations with edta using xylene 
 orange as an indicator .
the antibacterial activity of the ligand , metal salts , and the corresponding complexes were assayed simultaneously against pseudomonas aeruginosa ( pa ) , bacillus 
 cirroflagellosus ( bc ) , by cup - plate method .
nutrient broth was 
 prepared by dissolving peptone ( 0.5% ) , yeast extract ( 0.15% ) , beef extract 
 ( 0.15% ) , sodium chloride ( 0.36% ) , and monopotassium phosphate ( 0.13% ) in 
 distilled water ( 100 ml ) .
the ph of the solution was adjusted to 7.2 by adding sodium hydroxide solution ( 4% ) and the resulting solution was autoclaved for 20 minutes at 15 psi .
one day prior to 
 the experiment , the cultures of pseudomonas aeruginosa and 
 bacillus cirroflagellosus were inoculated in nutrient broth ( inoculation medium ) and incubated overnight at 37c .
nutrient agar medium was prepared by dissolving peptone ( 1% ) , yeast extract ( 0.6% ) , beef extract ( 0.5% ) , and sodium chloride ( 0.5% ) in distilled water .
the ph of the solution was adjusted to 7.2 by adding 4% 
 aqueous sodium hydroxide solution .
agar ( 2.4% ) was then added and the whole 
 solution was autoclaved for 20 minutes at 15 psi . each test sample ( 1 mg )
was dissolved in dmso ( 1 ml ) , and 0.1 ml of this solution ( 10 g ) 
 was used for testing .
inoculation medium containing 24-hours grown culture was 
 added aseptically to the nutrient medium and mixed thoroughly to get the 
 uniform distribution .
this solution was poured ( 25 ml in each dish ) into petri 
 dishes and then allowed to attain room temperature .
thereafter , punching the 
 set of agar with a sterile cork borer and scooping out the punched part made 
 the cups
the test samples and the standard 
 were tested at a concentration of 10 g .
the plates were allowed to stand for an hour in order to facilitate the diffusion of the drug solution .
the antifungal activity of the ligand and the corresponding metal complexes were tested 
 against the pathogenic fungi aspergillus niger ( an ) and penicillium 
 notatum ( pn ) by cup - plate method .
nutrient agar medium was prepared by the same method 
 as explained under evaluation of antibacterial activity .
one and half day prior to the experiment , the fungal cultures of aspergillus niger and penicillium notatum prepared in the 
 inoculation medium were incubated at 37c for 36 hours .
the fungal medium was prepared by dissolving peptone ( 0.5% ) , sodium chloride ( 0.36% ) , monopotassium phosphate ( 0.13% ) , and glucose ( 2% ) in distilled water ( 100 ml ) .
the ph of the solution was adjusted to 7.2 by adding sodium hydroxide solution ( 4% ) and the resulting solution was autoclaved for 20 minutes at 15 psi .
one and half day , grown cultures were added aseptically to this medium and 
 mixed thoroughly to get uniform distribution .
the solutions of the test samples 
 and standard were evaluated for antifungal activity by cup - plate method at a 
 concentration of 10 g .
the zone of inhibition was measured in millimeter for the particular test sample with each organism at 48 hours interval .
the analytical data ( see table 1 ) indicate that the complexes have 
 1 : 2 ( metal : ligand ) stoichiometry and can be represented by the general formula 
 [ la(mpbaq)2(h2o)2]no3 .
they are soluble in dmso and dmf , sparingly soluble in ethanol and methanol , but insoluble in benzene , ether , and chloroform . the molar conductance data ( see table 1 ) of the complexes in dmso at 
 10 m is in the range of 44.0049.00 ohmcmmol , which indicates 1 : 1 electrolytic nature of the complexes .
the diagnostic ir frequencies of the ligand hmpbaq and its complexes are compiled in table 2 . in the spectrum of the hmpbaq ,
the strong band observed at 1653 cm is assigned to (c = o ) of the quinazoline ring .
the appearance of this band at a lower wave number is due to the existence of strong 
 intermolecular hydrogen bonding between the oxygen of c = o and the hydrogen of 
 the 2-[2-hydroxy-3-methoxy phenyl ) group , as observed in its crystal structure 
 .
the two nonequivalent phenolic oh groups are observed at 34602940 cm as a strong unresolved broad band .
a medium intensity band at 3280 cm is assigned to (nh ) of the quinazoline ring . in the spectra of 
 all the complexes ,
the (c = o ) has shifted to lower wave numbers indicating the involvement of carbonyl oxygen in coordination .
the band due to (c = n ) has shifted to lower energy ( 16161572 cm ) , indicating coordination through benzyl amine nitrogen .
the band due to phenolic oh groups was not observed in the spectra of the complexes , it might have been obscured by a 
 broad band due to water .
however , the coordination through only one or both of 
 the phenolic oxygen / s was further confirmed by h nmr spectral 
 studies .
strong band at 1381 cm in the spectra of all the 
 complexes indicates the presence of ionic nitrate .
the presence of coordinated 
 water molecules is suggested by the appearance of characteristic rocking 
 frequency at 825 cm .
h nmr spectra of the hmpbaq and its la(iii ) complex were recorded in 
 dmso - d6 and the data along with the assignments are displayed in table 3 .
the h nmr spectrum of 
 hmpbaq exhibits two sharp peaks at 11.31 and 9.42 ppm , corresponding to o(2)h 
 ( d2o exchangeable ) and o(4)h ( d2o exchangeable ) , 
 respectively .
two singlets and one doublet at 8.43 , 7.43 , and 7.81 ppm are due 
 to c(21)h , n(3)h ( d2o exchangeable ) and c(13)h , respectively .
n(3)h 
 and c(13)h , being cis to one another , coupled together and this coupling 
 results in the splitting of c(13)h signal .
four triplets [ c(17)h , c(16)h , 
 c(10)h , and c(4)h ] and six doublets [ c(18)h , c(15)h , c(11)h , c(9)h , c(5)h , and 
 c(3)h ] have merged to give a multiplet at 7.316.6 ppm corresponding to ten 
 aromatic protons .
the resonance due to o(3)c(22)h3 and o(5)c(23)h3 appeared at 3.85 ppm . in the spectrum of la(iii ) complex
, the resonance due to o(4)h has appeared at the same position as in the ligand ( 9.40 ppm ) indicating the noninvolvement of o(4)h in the 
 coordination .
the singlet at 11.31 ppm in the ligand spectrum ascribed to o(2)h 
 group is not observed in la(iii ) complex .
the other signals [ c(21)h , n(3)h , c(13)h , c(17)h , c(16)h , c(10)h , c(4)h ,
c(18)h , c(15)h , c(11)h , c(9)h , c(5)h , c(3)h , o(3)c(22)h3 , and o(5)c(23)h3 ] in 
 la(iii ) complex did not show any considerable shift .
the effective magnetic moments ( see table 1 ) of all the complexes indicate that they are paramagnetic in nature except la(iii ) and y(iii ) which are diamagnetic .
the values obtained are similar to the van vleck and frank   and hund 's values except in case of sm(iii ) and eu(iii ) where slightly higher values were obtained .
this is due to low j - j separation , which leads to thermal population of higher energy levels .
the values obtained are similar to those of typical lanthanide ions   and indicate the noninvolvement of 4f electrons in bonding due to their very effective shielding by the 5s 5p octet .
the energy level of the lowest excited state is very high with no contribution from orbital angular 
 momentum and the anisotropic effect .
 value of 1.99 ( at room temperature ) and 2.04 ( at liquid nitrogen temperature ) compared to the free - ion 
 value of tetracynoethylene ( 2.00277 ) with broad resonance lines was obtained .
the  g  values being almost the same and similar line widths indicate that the line widths are independent of temperature .
further , the complete absence of zero - field hyperfine splitting and the presence of broad bands indicate that the gd(iii ) ion is located in a rather disordered environment caused by strain . these strains
d - strain for the zero field splitting distribution ) arise due to random hydrogen bonds between water molecules and the complex leading to distortions , which lead to broad resonance epr lines [ 19 , 20 ] . the electronic spectral data of the two representative complexes are given in table 4 .
the free ligand shows an intense band at 32786 cmand two weak bands at 28328 and 38610 cm of which the first two 
 are assigned to the n * and the latter to the  * transitions , respectively .
the electronic spectra of the complexes are dominated by ligand bands , with a slight shift to higher or lower energy levels .
this slight shift was attributed to the effects of crystal field upon the interelectronic repulsion between the 4f electrons .
the bonding parameter ( b ) , sinha 's covalence parameter (  ) , nephelauxetic parameter (  ) , and angular covalence (  ) have been calculated according to literature procedure [ 22 , 23 ] .
 values being less than unity and positive 
 value of b and  indicate metal - ligand covalent bonding . according to karraker ,
the shape of the hypersensitive transition 
 reflects the environment of the metal ion . on comparison of the spectra with that of known compounds
the tg / dta study of la(iii ) and pr(iii ) complexes was carried out as the representative . in case of la(iii ) complex , the initial weight loss of 11.24% ( cal .
the next weight loss in the temperature range of 250350c is due to the loss of one ionic nitrate molecule ( obs .
a further weight loss in the range of 350800c corresponds to two ligand molecules ( obs . 69.00% ; 
 cal .
69.89% ) . finally , the most stable oxide was formed , on further heating up to 
 1000c .
the percentage of metal obtained is in confirmation with the 
 analytical values for the metal content . in case of pr(iii ) , the thermogram exhibits a loss of 3.00% 
 ( cal .
a loss of 
 10.00% ( cal . 10.35% ) between 240260c is due to the removal of one ionic nitrate molecule . a further weight loss of 69.00% ( cal .
the mass spectrum of hmpbaq shows the formation of molecular ion 
 peak at m / z = 419 and corresponds to the total molecular weight of the ligand . 

the fab mass spectra of [ sm(mpbaq)2(h2o)2]no3 and [ eu(mpbaq)2(h2o)2]no3 show the molecular ion peaks at m / z = 1084 and 1086 , respectively , supporting the composition of the complexes . the results of the antibacterial and antifungal studies are given in table 5 .
the ligand hmpbaq was less active against pn , pa , and bc except against an where it has 
 shown moderate activity .
all the complexes , except la(iii ) , pr(iii ) , and nd(iii ) complexes , show moderate activity against bc . it was observed that , compared to the ligand and metal salts , the complexes exhibited enhanced antibacterial activity , which is due to the synergistic effect that increases the lipophilicity of the complexes .
chelation decreases the polarity 
 of the metal ion , which further leads to the enhancement of complex 's lipophilicity . since the microorganism cell is surrounded by a lipid membrane which favors the passage of lipid soluble materials , increased lipophilicities allows the penetration of complex into and through the membrane and deactivates 
 the active enzyme sites of the microorganisms
based on the above data , structure i is proposed for the lanthanide(iii ) complexes having the general 
 formula [ ln(mpbaq)2(h2o)2]no3 , where ln = la(iii ) , pr(iii ) , nd(iii ) , sm(iii ) , eu(iii ) , gd(iii ) , tb(iii ) , 
 dy(iii ) , and y(iii ) . in the present complexes , due to rotation about the n 
n bond , the ligand changes its conformation to facilitate the coordination in onn fashion as in the case of cd(ii ) complex as reported earlier .
the antibacterial activity of the ligand is enhanced on complexation , whereas no distinct change is observed in case of antifungal activity .
 new lanthanide(iii ) complexes with 2-[2-hydroxy-3-methoxyphenyl]-3-[hydroxyl-3-methoxybenzylamino]-1,2-dihydroquin-   
  azoline-4(3h)-one ( hmpbaq ) have been synthesized and characterized by elemental analysis , conductance measurements , magnetic susceptibilities , spectroscopic ( ir , nmr , uv , epr ) , and thermal studies . 
 molar conductance studies indicate 1 : 1 electrolytic behavior for these complexes . 
 ir spectra indicate that hmpbaq acts as a tridentate ligand coordinating through carbonyl oxygen , benzyl amine nitrogen , and deprotonated phenolic oxygen . 
 tg and dta studies of la(iii ) and pr(iii ) complexes indicate the presence of two coordinated water molecules . based on these studies , 
 the complexes have been formulated as [ la(mpbaq)2(h2o)2]no3 , where ln = la(iii ) , pr(iii ) , nd(iii ) , sm(iii ) , eu(iii ) , gd(iii ) , th(iii ) , dy(iii ) , and y(iii ) . 
 the ligand , lanthanide(iii ) salts , and the corresponding complexes have been simultaneously screened for their antibacterial and antifungal activities and compared with the drugs in use . 