Synthesis and biological activity of Magnesium(II)complexes of heptaaza Schiff base macrocyclic ligands;~1H and ~(13)C chemical shifts computed by the GIAO-DFT and CSGT-DFT methodologies

摘要

Two new pendant armed Schiff base macro-cyclic complexes,[MgL~1](ClO4)2(1),and[MgL~2](ClO4)2(2),have been prepared via cyclocondensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with two hexadentate hexaamines,ten and tmen,in the presence of Mg(II)ion.The ligands are 15-membered pentaaza mac-rocycles having two 2-aminoethyl pendant arms.The newly prepared complexes are investigated by IR,~1H NMR,~(13)C{~1H} NMR,DEPT(135),COSY(H,H)and HMQC spectroscopic methods.The antimicrobial screening of newly prepared complexes,1 and 2,as well as previously prepared similar complexes,[MgL~3](ClO4)2(3)and[MgL~4 ](ClO4)2(4),against Escherichia coli,Staphylococcus aureus and candidia albicans showed that the macrocyclic complexes of Mg(II)containing 15-membered pentaaza ring(1,2 and 3)have no activity.Where as the compound 4,which contain 16-membered pentaaza ring,had remarkable inhibition zone on the culture of S.aureus and E.coli as compared with standard drugs.The ~1H and ~(13)C chemical shieldings of gas phase complexes were also studied by the gauge independent atomic orbital(GIAO)and continuous set of gauge transformations(CSGT)methods at the level of density functional theory(DFT).The computed ~(13)C chemical shifts are in reasonably good agreement with the experimental data.