Fluorene analogues of xanthenes – low molecular weight near-infrared dyes

Abstract

Fluorene-based analogues of fluorescein, rhodol, and rhodamine exhibit absorption and fluorescence beyond 800-900 nm in water, 300-400 nm redshifted compared to the original oxygen-bridged xanthene dyes, giving a potential access...

Novel Method for the Synthesis of Merocyanines: New Photophysical Possibilities for a Known Class of Fluorophores

“…The synthesis from phenols/aminophenols and phthalic anhydride, however, limited the studies on the relationship between the structure of these dyes and their photophysical properties to substituents at position 9 (see numbering in Scheme 1). During the last two decades, the second bridging atom, i. e. oxygen, was replaced with silicon, [2][3][4] phosphorus, [5,6] sulfur, [7] or carbon [8][9][10] in rhodamine, [11][12][13][14] fluorescein, [15,16] and rhodol [17] scaffolds or it was removed entirely, [18] with spectacular success in terms of bathochromic shift of fluorescence and increased stability. The remaining positions 1, 2, 4, 5, 7 and 8 were dormant, although in Alexa-type fluoresceins two fluorine atoms are inserted at the left ring, featuring increased stability.…”

Migration from Lysosome to Nucleus: Monitoring Lysosomal Alkalization-Related Biological Processes with an Aminofluorene-Based Probe

“…Herein, by removing the bridging atom of the rhodamine scaffold, the brand-new aminofluorene-based probes could be obtained (Scheme ). By introducing different amino substituents at the 3 and 6 positions on the fluorene, the ethyl-substituted, methyl-substituted, azetidine-1-yl-substituted, and pyrrolyl-substituted derivatives (namely FEN , FMN , FAN , and FPN , respectively) were developed; among them, FMN , FAN , and FPN could target lysosomes and nucleus by right of their characteristics of lipophilic amino and affinity to DNA.…”

“…21,25 Considering larger molecular planarity was the premise for a small molecule to interact with DNA by intercalative binding, 26,27 we would focus our attention on the tricyclic fused amino-fluorene skeleton, which has been reported to combine with DNA by intercalation or minor groove in recent years, and the binding constants of these probes with DNA were more potent than that of ethidium bromide, 28−31 which provided a robust guideline for our design. Herein, by removing the bridging atom of the rhodamine scaffold, 32 the brand-new aminofluorene-based probes could be obtained (Scheme 1). By introducing different amino substituents at the 3 and 6 positions on the fluorene, the ethyl-substituted, methyl-substituted, azetidine-1-yl-substituted, and pyrrolyl-substituted derivatives (namely FEN, FMN, FAN, and FPN, respectively) were developed; among them, FMN, FAN, and FPN could target lysosomes and nucleus by right of their characteristics of lipophilic amino and affinity to DNA.…”

A Thiophenoradialene-Embedded Polycyclic Heteroterphenoquinone Exhibiting Dominant Antiaromatic Traits

“…The emission maximum of 6 at 576 nm in DCM showed a small Stokes shift of 19 nm due to a planar and rigid backbone. Interestingly, the fluorescence disappeared upon oxidative dehydrogenation of 6 to 7 , which could likely be attributed to the dominant antiaromaticity of 7 opening the radiationless relaxation pathway due to conical intersection between the excited state and ground state potential energy surfaces . Notably, formally aromatic thia-hybrid [5]­radialenes are fluorescent.…”

“…SCXRD and (anti)­aromaticity analyses [NICS(1) zz and ACID] suggested the large BLA and dominant antiaromatic character of the embedded pentafulvene subunits for 7 , as a result of the electron-withdrawing π-extended carbonyl substituents exo to the five-membered ring . The antiaromaticity was demonstrated experimentally by the weakly intense absorption band in the range of 535–800 nm owing to a forbidden HOMO → LUMO transition, facile two-stage electron reductions with good reversibility, and non-emissive properties. ,, Our current synthetic approach has the potential to construct other heteroatom (i.e., selenium) counterparts of 7 (and 6 ) with tunable solid state ordering and HOMO–LUMO energy gaps for potential application as ambipolar organic semiconductors, which is underway.…”