Synthesis And Characterization Of Coumarin- Indole /Quinoline Dyes And Their Spectral Properties

Small-molecule fluorescent probes are valuable tools for environmental and biochemical studies due to their favorable properties including high sensitivity, easy for implementation, and minimal disturbance to biological samples. To minimize cross-talk in emission windows for ratiometric measurement with high accuracy, a ratiometric fluorescent probe should be display a large emission wavelength shift (> 80 nm) after it interacts with a target molecule. However, most of the ICT-based ratiometric probes have rather limited emission spectral shift, which results in poor resolution of the two emission peaks and thus errors in ratiometric fluorescence measurement.We have presented a general dye conversion strategy to rational design of ICT-based fluorescent ratiometric probes with large absorption and emission spectral shifts, which is highly favorable for determining the fluorescence intensities and signal ratios with high accuracy and for enhancement of the dynamic range of signal ratios. Based on this strategy, we design and synthesize coumarin and cyanine derivatives, and particularly studied the target molecules spectral properties.1. A Ratiometric Fluorescent Probe 8 for Reactive Oxygen Species .We studied the spectral properties of probe 8, try our best knowledge, We found that probe 8 represents the first small-molecule fluorescent ratiometric probe for hydroxyl radical with the outstanding spectral properties. Probe 8 exhibits high stability in the air and high selectivity for hydroxyl radical over other species tested.2. Ratiometric Fluorescent Probes 1h for pH.Probe 1h is a ratiometric fluorescent probe with the outstanding spectral features including large absorption and emission shifts as well as a large ratio signal. With the decreasing of pH values from 7.51 to 3.50, a nearly 404-fold variation be found in the emission ratios. It is important to note that such a large change of signal ratios at two wavelengths is highly desirable for ratiometric fluorescent probes, as the sensitivity and the dynamic range of ratiometric probes are controlled by the ratios.3. Ratiometric Fluorescent Probes 1j for Zn²⁺.Probe 1j is an interesting candidate of ratiometric fluorescent Zn²⁺ probes with emission in the NIR region. Furthermore, ratiometric fluorescent probe 1j exhibited a good selectivity to Zn²⁺. The favorable spectral properties of compound 1j render it promising as a ratiometric fluorescent probe for investigating Zn²⁺ associated biological processes.