Four new ternary Oxovanadium(IV) complexes, [VO(L)(B^1-4)](acac), where, L = (E)-2- (2-hydroxybenzylideneamino)-5-guanidinopentanoic acid (Argininesalisylidene) and B were 1H-imidazo-[4,5-f][1,10]-phenanthroline (B¹) (1), 2-phenyl-1H-imidazo [4,5-f][1,10] phenanthroline (B²) (2), 2-(naphthalen-1-yl)-1H-imidazo [4,5-f][1,10] phenanthroline (B³) (3) or 1-(pyren-2-yl)-1H-imidazo[4,5-f][1,10] phenanthroline(B⁴) (4) were synthesized, characterized and photocytotoxicity in A549 cell were studied in dark andvisible light (400–700 nm, 10 J cm^-2). Photochemistry of the complexes (1-4) related to the generation of singlet oxygen (¹O₂) was studied in detail. The presence of triplet excited state in the complexes was probedfrom perylene assay. Photo-activated generation of singlet oxygen from the complexes was probed by DPBF assay and the degree of photo-cytotoxicity of the complexes was related to their ability in photo-activated ¹O₂ generation. Complexes 4 exhibited remarkable photocytotoxicity in A549 cells with photo index (PI) ~ 16 invisible light (400–700 nm, 10 J cm^-2) (IC₅₀, 3.81 lμM), while complexes were almost less-toxic in dark (IC₅₀,59.7 lμM). Intracellular ROS generation was studied from 2Ꞌ,7Ꞌ-dichlorofluorescein diacetate (DCFH-DA).Annexin V-FITC/PI assay suggested apoptotic nature of cell death. Overall, the remarkable photocytotoxicefficacy of the new Oxovanadium(IV) complexes (1-4) making them the potential photochemotherapeutic agents in lieu of porphyrin-based PDT agents.