Tuning the Excimer Emission of Amphiphilic Platinum(II) Complexes Mediated by Phospholipid Vesicles

Two new amphiphilic platinum(B) complexes, [Pt(2-(4-fluorophenyl)-5-(4-dodecyloxyphenyl)pyridine) (acac)]-(Pt-1) and [Pt(2-(4-dodecyloxyphenyl)-5-(thien-2-yl)-c-C-yclopentenepyridine) (acac)] (Pt-2), where-acac is acetylacetonate, were synthesized and characterized. Apart from,conventional phosphorescence of single molecules (ME-monomer emission), complexes Pt-1 and Pt-2 also exhibit excimer emission (BB) when embedded into phospholipid vesicles, that is assigned to emissive Pt-Pt excimers. The BE intensity. in-vesicular media appeared to depend on the viscosity of the vesicles and the concentration of the embedded,complex. Differences in the EE properties of complexes Pt-1 and Pt-2 are Correlated with the energies of the pi-character frontier orbitals defined by the design of the cyclometalating phenylpyridine ligand. Higher energies of the frontier pi-orbitals (HOMO and LUMO) naturally promote stronger pi=pi interactions, thus obstructing the Pt-II-Pt-II interaction.