Synthesis of photoluminescent rhenium(I) naphthalimide complexes as biological probe

The synthesis and characterization of the ligand N-(pyridin-3-yl)-4-aminobutyl-1,8-naphthalimide (L2) and its rhenium(I) complex [Re(Phen)(CO)3(L2)](BF4) (4) (Phen = 1,10-phenantroline) through coordination of the nitrogen atom of the pyridyl ring are the aim of this thesis. In fact, the luminescent properties of naphtalimides can be combined with the ones of rhenium(I) complexes to act as metal-based carrier, and this can be useful as bacterial imaging probe, due to the ability of rhenium derivatives to penetrate the cell envelopes of bacteria and making different sub-cellular structures visible. The ligand L2 was obtained via two synthetic steps starting from 1,8-naphthalic anhydride and reaction with 3-aminopyridine first, and then with n-butylamine. The best reaction conditions in order to obtain 4 were studied, starting from halogen abstraction from [Re(Br)(Phen)(CO)3] (1) with AgBF4, followed by reaction with L2. The desired complex revealed to be difficult to be purified from the reaction mixture. Once isolated it was characterised via 1H NMR, IR and UVVis spectroscopies, elemental analysis and MS ESI+ spectrometry. In particular, the competition between deuterated DMSO and L2 revealed to be a delicate issue when characterizing 4 via NMR spectroscopy. The photophysical measurements on 4 show an emission predominantly arising from the naphthalimidic ligand due to the partial overlap of the ICT naphthalimide absorption band with the expected 3MReLphenCT emission profile. Future studies on the bacterial cellular uptake of 4 will be performed in order to exploit the luminescent properties of the coordinated ligand L2 and take advantage of rhenium complex as metal-based carrier.