Novel indolo [3,2-c]isoquinoline-5-one-6-yl [1,2,4]triazolo [3,4-b] [1,3,4]thiadiazole analogues: Design, synthesis, anticancer activity, docking with SARS-CoV-2 Omicron protease and MESP/TD-DFT approaches

•Synthesis of indolo [2,3-c]isoquinoline derivatives containing different substitutions (Cl,CH3,H, NH2,NO2).•Structural conformation of the unknown compounds with the help of their TLC, spectral studies viz, IR, 1H,13C NMR, mass spectroscopy and elemental analysis (HRMS) etc.•Syntheiszed compounds were evaluated for their anticancer activity against various different human cancer cell lines, like (Breast Carcinoma), (Lung carcinoma) and (Cervical carcinoma) etc.•Molecular docking study of synthesized compounds against SARS-CoV-2 omicron protease approaches.•Molecular electrostatic potential (MESP) analysis.•Time-Dependent density functional theory (TDDFT) and frontier molecular orbitals studies .