This thesis outlines a review of the history, synthetic procedures, optical properties, and applications of quinoline-containing cyanine dyes in the first chapter. The second chapter introduces the synthesis, characterization, and optical properties of new symmetrical pentamethine cyanine dyes and their potential application in photodynamic therapy (PDT). The structure identification of final compounds was done by 1H and 13C nuclear magnetic resonance (NMR) and mass spectrometry. The studies were performed after full characterization and determination of optical and physicochemical properties. Several representative dyes were selected for analysis of their DNA photocleavage activity.