New Hindered BODIPY Derivatives: Solution and Amorphous State Fluorescence Properties

Abstract

Four new hindered boron-dipyrromethene (BODIPY) dyes have been engineered and synthesized by modification of the pyrrole substituents. The chromophores were designed to shift their absorption and emission wavelengths to the red and to show quantitative emission in solid amorphous deposits. [2.2]Paracyclophane (PcP) was grafted on the BODIPY core as well as alkyl chains of various length to force the molecules away one from each other and prevent π−π stacking. The optical spectroscopic and electrochemical properties in solution are presented. Absorption, emission and FLIM were done on drop-casted films of the fluorophores. The addition of alkyl substituents (-Me, -Et, n-Pr) next to the PcP group clearly affects the emission properties in solid state since the dyes display sharper emission bands than in solution and their relative fluorescence quantum yield increases with the number of carbons in the alkyl chain. Fluorescence lifetime images analysis reveals complex decay profiles. Quite a fair description ...