Small-Molecule Fluorophores with Large Stokes Shifts: 9-Iminopyronin Analogues as Clickable Tags

Abstract

The design, synthesis, and both experimental and theoretical studies of several novel 9-(acylimino)- and 9-(sulfonylimino)pyronin derivatives containing either an oxygen or a silicon atom at position 10 are reported. These compounds, especially the Si analogues, exhibit remarkably large Stokes shifts (around 200 nm) while still possessing a high fluorophore brightness, absorption bands in the near-UV and visible part of the spectrum, and high thermal and photochemical stabilities in protic solvents. The reason for the observed large Stokes shifts is an intramolecular charge-transfer excitation of an electron from the HOMO to the LUMO of the chromophore, accompanied by elongation of the C9-N bond and considerable solvent reorganization due to hydrogen bonding to the solvent. Due to the photophysical properties of the studied compounds and their facile and high-yielding synthesis, as well as a simple protocol for their bioorthogonal ligation to a model saccharide using a Huisgen alkyne-azide cycloaddition, they represent excellent candidates for biochemical and biological applications as fluorescent tags and indicators for multichannel imaging. 9-(Acylimino)pyronins alter their optical properties upon protonation and may also be used as pH sensors.

Study of Donor–Acceptor–π–Acceptor Architecture Sensitizers with Benzothiazole Acceptor for Dye‐Sensitized Solar Cells

“…As shown in Figure 3c,h igh Stokes shift values (117, 104, 159, and 125 nm, respectively)f or all dyes might be attributed to the ICT excitation of an electron from the HOMOt ot he LUMO of the sensitizer. [39] Time-dependent (TD) DFT calculations were carried out to analyze the photophysical behavior of these complexes and to understand the transitionsi nt erms of the molecular orbitals in DMF at the CAM-B3LYP/6-311G(d,p) level of theory. Then ormalized simulated and experimental UV/Vis spectra of MCG1-MCG4 are given in Figure S3 in the Supporting Information.T he spectra were produced by deconvoluting Gaussian functions with af ull-width at half-maximum (FWHM) of 0.37 eV centered at the excitation wavenumbers.…”

Preparation and application of a BODIPY-labeled probe for a real-time polymerase chain reaction

“…The results of qPCR showed that the oligo nucleotide probes with TMB can be applied in qPCR experiments on a par with hydrophilic fluorescent labels, such as FAM. TaqMan type fluorescent probes were prepared by conjugation of the alkyne substituted dye (com pound (2) or FAM alkyne (N (prop 2 yn 1 yl) 5 carboxamide fluorescein, Lumiprobe, United States)) with the azide containing oligonucleotide (Syntol, Russia) using the Cu(I) TBTA catalyst (Lumiprobe, United States) according to manufac turer's procedure. Probes were purified by HPLC on a C4 reversed phase column (Phenomenex) equili brated with 100 mM ammonium acetate in the aceto nitrile gradient (from 8 to 60% of acetonitrile per 40 min); the flow rate was 0.7 mL/min.…”

“…In the present work, the fluorescent probes for qPCR were obtained by the scheme where an alkyne containing fluorophore is attached to an oligonucleotide with a fluorescence quencher at one end and the azide group at another end by the click reaction. This approach expands the choice of fluorophores by a set of alkyne derivatives of dyes, which are commercially available or can be synthesized easily [2][3][4].…”

Tuning ‘Stokes Shift’ and ICT Character by Varying the Donor Group in Imidazo[1,5 a]pyridines: A Combined Optical, DFT, TD‐DFT and NLO Approach

“…Molecules with small Stokes shift generally suffer from self‐quenching . Therefore, large Stokes shift is an important aspect to diminish reabsorption and light scattering in optical materials, such as fluorescent probes,, organic lasers, and quantum dots .…”

“…Therefore, large Stokes shift is an important aspect to diminish reabsorption and light scattering in optical materials, such as fluorescent probes,, organic lasers, and quantum dots . The enhanced Stokes shift can be achieved by excited‐state geometry relaxation accompanied by solvent reorganization ,. Consequently, efforts were taken for the creation of functionalized imidazo[1, 5a]pyridine derivatives with a large Stokes shift to achieve the fine‐tuned photophysical properties.…”