Synthesis of novel fluorescence cationic gold(I) complexes as potent anti cancer agent

Novel acridine ligands were synthesized and converted to the corresponding cationic gold(I) complexes to provide new fluorescent tools for the study of their mechanism of action using confocal microscopy. These complexes were characterized by X-ray crystallography and their activity was evaluated against liver hepatocellular carcinoma HepG2 cells. A new series of cationic gold(I) pyrazole complexes were also prepared in excellent yields as their perchlorate salts. Results of cell viability assays show that these novel complexes have good cytotoxic properties against the human HepG2 cancer cell line. These complexes showed promising anti-cancer activities and pyrazoles have never been tested against this cell line in prior art. The regioselectivity of the complexation is also discussed in regards to the substitution pattern of the pyrazoles. The investigation of the reactivity of gold(I) with triphenyl phosphine and trihexyl phosphine provided an insight into the behaviour of cationic gold(I) in solution. The exchange of ligands could be observed at low temperature (-80 oC) with higher coordination numbers. The photophysical properties of substituted acridine ligands and their complexes have also been investigated. The substituted acridine functionalised by small electronically active groups showed a hypsochromic shift to shorter wavelengths when the conjugated p-system is electron deficient and bathochromic shift to longer wavelengths when the delocalised ring bore electron donating group and electron withdrawing group. Investigations into the effect of halogen substituents indicated a similar trend in the excitation and emission wavelengths. The position of the substitution and the nature of the substituent(s) has been shown to have a great impact on the Stokes shift and the quantum yield of the compounds. For instance, the addition of one or more methoxy groups lead to bathochromic shift which also reflects in the Stokes shift of the acridine derivatives.