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

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-PR_nP)] 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 .