Dipolar 3-methoxychromones as bright and highly solvatochromic fluorescent dyes

Abstract

Herein, three environment-sensitive (solvatochromic) fluorescent dyes presenting a strong electron acceptor 3-methoxychromone unit and varied electron donor 2-aryl were developed. All three dyes showed remarkable polarity-dependent shifts of the emission maximum, which increase with extension of the dye conjugation. For the 3-methoxychromone bearing a 7-(diethylamino)-9,9-dimethylfluoren-2-yl donor group the difference between the excited and the ground state dipole moments, estimated from the Lippert-Mataga expression, reached 20 D, which is among the largest reported for neutral dipolar fluorophores. Moreover, the new dyes are characterized by significant two-photon absorption cross-section (up to 450 GM) and large fluorescence quantum yields. The strong decrease in the fluorescence quantum yields of the dyes in polar protic solvents was observed together with the increase in the non-radiative deactivation rates, which can originate from twisted intramolecular charge transfer and intermolecular proton transfer phenomena. In comparison to the parent 3-hydroxychromone derivatives, the new dyes presented significantly improved photostability, which confirms that photodegradation of 3-hydroxychromones occurs from a product of the excited-state intramolecular proton transfer (phototautomer). Finally, an application of the new dyes for probing local binding site polarity of serum albumin was shown. This new class of fluorescent dyes may serve as attractive building blocks for future molecular sensors utilizing environment-sensitive fluorophores.

A protective layer approach to solvatochromic sensors

“…Various organic12345678910, organometallic1112, metal organic framework1314 and hybrid1516 materials have been investigated to determine their solvatochromic properties in diverse solvents. Conventional colorimetric sensors, however, inevitably display changes in absorption and emission peaks that are in indiscriminant in their response to organic solvents.…”

Solvatochromic Pyrene Analogues of Prodan Exhibiting Extremely High Fluorescence Quantum Yields in Apolar and Polar Solvents

“…[4,5] Therefore, a large number of organic fluorescent dyes have been developed, and criteria for designing them with the desired properties and functions have been established. [6][7][8][9][10][11][12][13][14][15][16][17] In addition, a high fluorescence quantum yield (QY) is important for the aforementioned applications and is generally achieved by extending the p-conjugation systems of appropriate chromophores, [18] for example, as observed in the relationship between pyrene (F Fl = 0.26 in chloroform) [19] and 1,3,6,8-tetraarylpyrene (F Fl % 0.90 in dichloromethane). [2] Solvatochromism is often achieved by introducing electronic donor and acceptor moieties, such as in "push-pulltype" dyes.…”

The Laurdan Spectral Phasor Method to Explore Membrane Micro-heterogeneity and Lipid Domains in Live Cells

“…These probes have equal and high affinity for every region of the membrane. Some examples of these fluorescent membrane markers are Laurdan (with its derivatives) [15][16][17][18][19][20][21], di-4-ANEPPDHQ [22,23], and other solvatochrome derivatives [24][25][26]. In this work we focus on the Laurdan probe and its capability to sense the polarity of its environment [27].…”