## 1 Introduction  
The importance of the heterocyclic compounds came from the diversity usage in industries, biological fields [1, 2] and in analytical chemistry as analytical reagents for metal ion detection [3] or dyes synthesis, cosmetics, plastics and pharmaceutical products. Moreover, they play a practical role in the drug industry by designing and developing medicines and their wide applications [4]. One of the essential chemical structure classes is nitrogen heterocycles which are particularly well represented between natural products, biologically active structures, and medical-related compounds [3]. Among the most distinguished types, phenanthridine, indole, pyrazine, quinoline, and isoquinoline compounds which have gained significant interest in organic synthesis, medical chemistry, and materials science [5]. Schiff bases are an important class of organic compounds especially the ones synthesized from heterocyclic compounds, due to their chelating properties and ability to coordinate with a wide range of actinide, lanthanide and transition ions in various oxidation states using oxygen and nitrogen or other atoms to form stable complexes [6]. Several Schiff bases were prepared to contain nitrogen atoms with crucial biological activity such as antimicrobial, antioxidant, anticancer, anti-HIV activity, analgesic, anti-inflammatory [3, 7].  
It was reported when metal ions are introducing into the molecules of the compound it could improve their biological properties by decreasing their toxicity and enhancing their lipophilicity, absorbance, and stability [7]. Additionally, the presence of an imine (-C=N-) or azomethine (-HC=N-) group in Schiff bases contributes to linkage provides much flexibility in the design ligands for metal ion coordination [3; 8]. Interestingly, most of the studies confirmed complexes of Schiff bases with transition metals are showed higher biological activities than their corresponding ligand [8]. [PERSON] et al. synthesized Pt(II) complexes with Schiff bases derived from salicaldehyde. The Schiff base ligand and its Pt(II)complexes have been tested in vitro to evaluate their antibacterial activity against eight types of bacteria. The activity data show that the Pt(II) complexes are more potent antimicrobials than the parent Schiff base ligands against one or more microorganisms [9]. [PERSON] et al. synthesized three salicaldehyde derivatives Schiff base ligand and their Zn(II), Cu(II), and Co(II) complexes. These compounds were screened and evaluated by antibacterial and antifungal bioassay and showed that the metal complexes have more active than the free ligan. Among these complexes, the Cu(II) complex was the most effective compared to other complexes [10]. Another reported work presented eight vanadium complexes derived from Schiff bases and tested their inhibition toward human recombinant PTP1B by selected complexes, glucose consumption and cytotoxicity tests in adipocytes in 3T3- L1 cell line. All vanadium complexes were noncytotoxic and three complexes were found to be active in the inhibition of human recombinant PTP1B [11].  
In this study, Schiff bases and their transition metal complexes Mn(II), Cu(II), Ni(II), Co(II), and Zn(II) were synthesis and characterization by various techniques. The interaction of Schiff bases and their transition metal complexes with biological targets were tested with CT-DNA. Molecular docking was used to simulate the binding of the investigated complexes with three types of cancer proteins. Finally, we tested the complexes in vitro activity against three cancer cell lines via (Ovar3), (M14), and (NSCLC).