Master of Science
Luyt, Leonard G.
1,8-Naphthalimide fluorophores with amino-substituents absorb and emit in the visible region. The photophysical properties of this class of fluorophores can be modulated by altering the degree of Intramolecular Charge Transfer (ICT) in the excited state. Thus, several metal complexes with the 1,8-naphthalimide motif have been developed as cell imaging agents. In this project, four 1,8-naphthalimide ligands were synthesized by incorporating rigid linkers. Among these, three ligands also allowed the extension of π-conjugation to the naphthalimide moiety. In addition, a ligand was also synthesized without the use of a linker. Re(I) tricarbonyl complexes of these ligands were also synthesized and their photophysical properties were studied. Extension of π-conjugation was seen to shift the emission of the fluorophores to shorter wavelengths that are not ideal for cell imaging. However, ligands that lack the extended π-conjugation fluoresce at ca. 420 nm, implying their use as fluorescence imaging agents and possible development as SPECT tracers.
Summary for Lay Audience
Optical imaging is an imaging technique that is non-invasive and uses light to image the tissue and organs. Due to the scattering of light by the tissues and cell components, specific drug-like molecules, called imaging probes, are used to enhance the contrast of the tissue. Molecules that exhibit fluorescence are often used as probes for optical imaging. 1,8-Naphthalimde is one such molecule that shows fluorescence behaviour when irradiated by visible light. The wavelength of light emitted by 1,8-naphthalimide can be modified by adding certain molecules, called linkers. Simple hydrocarbon chains have been previously utilized as linkers to make 1,8-naphthalimide based imaging agents. In this study, we use 4 different rigid molecules such as a benzene ring, as linkers and analyze the changes in the wavelength of emitted light. Another derivative was also synthesized without the use of a linker. Complexes of rhenium metal are also known to be good cell imaging agents. In addition, they also allow the possibility of developing imaging probes for a different imaging technique, that utilizes gamma rays from radioactive metals to image the organs. Hence, complexes were synthesized by using 1,8-naphthalimide derivatives as ligands to from rhenium metal complexes. Measurement of the fluorescence properties of these ligands and rhenium complexes revealed that the use of rigid linkers resulted in emission of light which has wavelengths below 400 nm. Since the microscope that is used to image cells utilizes light in the range of 400 to 800 nm, the newly synthesized ligands and their rhenium complexes may not be useful as cell imaging agents. However, successful formation of rhenium complexes implies the possibility of using 99mTc as the radioactive metal to develop nuclear imaging probes.
Jagadeesa Prabhu, Priyanka, "Synthesis And Characterization of Re(I) Tricarbonyl Complexes of 1,8-Naphthalimide" (2021). Electronic Thesis and Dissertation Repository. 8111.
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