10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 1 2012 (January - March) A series of Co(II) and Cu(II) complexes with N-amidino-N lessThan sup greaterThan 1 lessThan /sup greaterThan -naphthylthiourea (L) have been synthesized and the nature of bonding and structure of complexes have been deduced from elemental analysis, IR, lessThan sup greaterThan 1 lessThan /sup greaterThan H NMR, electronic spectra, magnetic susceptibility and conductivity measurements. The physico chemical studies and spectral data reveals that the ligand acts as neutral bidentate and coordinates through S and N. An octahedral geometry has been suggested for all the complexes and are formulated as [ML lessThan sub greaterThan 2 lessThan /sub greaterThan X lessThan sub greaterThan 2 lessThan /sub greaterThan ] where M = Co(II), Cu(II), X = Cl lessThan sup greaterThan - lessThan /sup greaterThan ,. The complexes [CoL lessThan sub greaterThan 2 lessThan /sub greaterThan Cl lessThan sub greaterThan 2 lessThan /sub greaterThan ] and [CuL lessThan sub greaterThan 2 lessThan /sub greaterThan Cl lessThan sub greaterThan 2 lessThan /sub greaterThan ] have been subjected to thermal decomposition study. The lessThan i greaterThan in-vitro lessThan /i greaterThan antimicrobial and antitumour properties of the ligand in comparison to their metal complexes have been evaluated and it is observed that the complexes show more potent activity than the ligand. G. Krishnan And S. Suprabha Co(II) complexes, Cu(II) complexes, N-amidino-N1-naphthylthiourea , thermal study, antimicrobial, antitumour 426-440