Investigation on Optical and Biological Properties of 2-(4-Dimethylaminophenyl)benzothiazole Based Cycloplatinated Complexes

Abstract

The optical and biological properties of 2-(4-dimethylaminophenyl)benzothiazole cycloplatinated complexes featuring bioactive ligands ([{Pt(Me2N-pbt)(C6F5)}L] [L=Me2N-pbtH 1, p-dpbH (4-(diphenylphosphino)benzoic acid) 2, o-dpbH (2-(diphenylphosphino)benzoic acid) 3), [Pt(Me2N-pbt)(o-dpb)] 4, [{Pt(Me2N-pbt)(C6F5)}2(μ-PRnP)] [PR4P=O(CH2CH2OC(O)C6H4PPh2)2 5, PR12P=O{(CH2CH2O)3C(O)C6H4PPh2}2 6] are presented. Complexes 1–6 display 1ILCT and metal-perturbed 3ILCT dual emissions. The ratio between both bands is excitation dependent, accomplishing warm-white emissions for 2, 5 and 6. The phosphorescent emission is lost in aerated solutions owing to photoinduced electron transfer to 3O2 and the formation of 1O2, as confirmed in complexes 2 and 4. They also exhibit photoinduced phosphorescence enhancement in non-degassed DMSO due to local oxidation of DMSO by sensitized 1O2, which causes a local degassing. Me2N-pbtH and the complexes specifically accumulate in the Golgi apparatus, although only 2, 3 and 6 were active against A549 and HeLa cancer cell lines, 6 being highly selective in respect to nontumoral cells. The potential photodynamic property of these complexes was demonstrated with complex 4.