Synthesis And Characterization of Re(I) Tricarbonyl Complexes of 1,8-Naphthalimide
Abstract
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.