Luminescent 2,7-disubstituted germafluorenes

Abstract

A series of six luminescent 2,7-alkynyl(aryl)-3,6-dimethoxy-9,9-diphenylgermafluorenes were synthesized from the corresponding 2,7-dibromo-3,6-dimethoxy-9,9-diphenylgermafluorene utilizing a palladium-catalyzed Sonogashira cross-coupling reaction to incorporate different alkynyl(aryl) groups at the 2,7-positions of the germafluorene ring. The new germafluorenes show an intense absorption band centered between 371-388 nm and moderate to strong emission in solution between 401-443 nm (Φ F = 0.65-0.83) as well as emission from the solid-state. Germafluorenes 4a-4f were characterized by multinuclear 1 H and 13 C{ 1 H} NMR, EA, DSC, TGA, UV-Vis, and fluorescence spectroscopy. TGA and DSC studies of germafluorenes 4a-4f showed high thermal stability. The molecular structures of four of the germafluorenes, 4c-4f were determined by X-ray crystallography.

Group 14 Metallafluorenes as Sensitive Luminescent Probes of Surfactants in Aqueous Solution

“…Fluorescent 2,7-disubstituted sila-and germa uorenes 1-4 were synthesized as previously described using an appropriate ethynyl aryl precursor in a palladium-catalyzed Sonagashira cross-coupling reaction [1,2].…”

“…Sila-and germa-uorenes, also known as dibenzosiloles or dibenzogermoles, are a class of photoluminescent compounds with high quantum yields in organic solvents [1,2]. Interest in their potential applications as OLEDs recently drove us to synthetically explore 2,7-alkynyl(aryl) substitutions (Fig.…”

“…Interest in their potential applications as OLEDs recently drove us to synthetically explore 2,7-alkynyl(aryl) substitutions (Fig. 1A), which could be exploited to tune spectral behavior by extending the high degree of conjugation [1,2]. Such substitutions can also attenuate solubility in various solvents.…”

“…Metalla uorenes (MFs) of su cient solubility in aqueous solution and sensitivity to surfactants would represent a new class of uorescent detectors for the detection and study of surfactants and relevant biological structures. Here we characterize the aqueous solution emission behaviors of four previously synthesized metalla uorenes [1,2] and their interactions with a variety of surfactant solutions. Indeed, we demonstrate here that these MFs are soluble in aqueous solution at low µM concentrations and luminesce under these conditions with competitive quantum yields.…”

Group 14 Metallafluorenes for Lipid Structure Detection and Cellular Imaging

“…Recently, we evaluated a small library of sila-and germafluorenes (metallafluorenes or MFs) containing alkynyl(aryl) substituents at the 2,7-position ( [8,9]; Figure 1) for their potential as fluorescent probes of surfactants. These compounds are soluble and luminescent in aqueous solution and exhibit high quantum yields and dramatic emission enhancements in the presence of various surfactants (5-25-fold) [10].…”