In present work Four new complexes of 2-hydroxy-5-methylbenzaldehyde
-N-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)hydrazine have been synthesized with some
transition metals, i.e. Ni+2, Cu+2 , Co+2 and Zn+2 in non-aqueous medium. Complexes
were characterized by magnetic moment, conductance, scanning electron microscopy
(SEM) and spectroscopic investigations including infrared, ultraviolet-visible and atomic
absorption spectroscopy. To support experimental characterization, quantum mechanical
and molecular mechanical (QM/MM) calculations were performed. Experimental results
with the support of QM and MM computations highlighted the proposition about the
ligand to be bound to the metal ions in a tridentate manner through its phenolic oxygen,
azomethine nitrogen and carbonyl group (C=O). On the basis of experimental and
computational results, tetrahedral geometry is proposed for Cu+2 complex and distorted
tetrahedral geometry is proposed for Zn+2 complex while octahedral geometries are
proposed for Co+2 and Ni+2 complexes. For all compounds, anti-cyanobacterial (algicidal)
activity was evaluated against three marine cyanobacteria i.e. Pseudoanabaena
lonchoides, Lyngbya contorta, and Spirulina major. It was found that the metal
complexes are more potent anti-cyanobacterial agents than the ligand
