Fluorescent Molecular Rotors for Viscosity Sensors

Abstract

Fluorescent molecular rotors (FMRs) can act as viscosity sensors in various media including subcellular organelles and microfluidic channels. In FMRs, the rotation of rotators connected to a fluorescent π-conjugated bridge is suppressed by increasing environmental viscosity, resulting in increasing fluorescence (FL) intensity. In this minireview, we describe recently developed FMRs including push-pull type π-conjugated chromophores, meso-phenyl (borondipyrromethene) (BODIPY) derivatives, dioxaborine derivatives, cyanine derivatives, and porphyrin derivatives whose FL mechanism is viscosity-responsive. In addition, FMR design strategies for addressing various issues (e.g., obtaining high FL contrast, internal FL references, and FL intensity-contrast trade-off) and their biological and microfluidic applications are also discussed.

Rational Design of Dual‐State Emission Luminogens with Solvatochromism by Combining a Partially Shared Donor–Acceptor Pattern and Twisted Structures

“…A twisted intramolecular charge transfer (TICT) mechanism may be responsible for solvatochromism behaviours of these DSEgens, similar to traditional TICT molecules for viscosity measurement . To verify this hypothesis, the PL spectra changes caused by the protonation and the following deprotonation of DPAB were recorded as shown in Figure S18, Supporting Information.…”

“…At wistedi ntramolecular charge transfer (TICT) mechanism may be responsible for solvatochromismb ehaviours of these DSEgens, similar to traditional TICT molecules for viscosity measurement. [14,15] To verify this hypothesis, the PL spectra changes caused by the protonation andt he followingd eprotonation of DPAB were recordeda ss hown in Figure S18, Supporting Information. The intense blue fluorescenceo fD PABi n toluene gradually declines with the addition of trifluoroacetic acid, but then progressively recovers following the introduction of excess triethylamine into the above system.T hese observations suggest that the bright-blue emission of DPAB in tolueneo riginates from aT ICT state because this emission can be greatly inhibited by the protonation of the triphenylamine moiety which converts the electron-donating triphenylamine to an electron-withdrawing triphenylaminonium ion.…”

Cell Fuelling and Metabolic Energy Conservation in Synthetic Cells

“…[88,89] pHluorini sb ased on GFP and has spectral properties in the yellow and green region. [97,98] Potassium:K IRIN1/KIRIN-GR and GINKO1a re potassium ions ensors that are based on the same K + binding protein,b ut differ in the fluorescentp roteins used. [90,91] These are commerciallya vailable and allowi maging for longer periodso ft ime than the protein-baseds ensors.…”

“…Fluorescentm olecularr otors are available as intensio-and ratiometric sensors. [97,98] Potassium:K IRIN1/KIRIN-GR and GINKO1a re potassium ions ensors that are based on the same K + binding protein,b ut differ in the fluorescentp roteins used. The two KIRIN sensorsu se different FRET pairs, whereas GINKO1h as only one circularp ermutated FP.…”

Mesityl or Imide Acridinium Photocatalysts: Accessible Versus Inaccessible Charge‐Transfer States in Photoredox Catalysis

“…The large bathochromic shift of 2 b could be related to the partial planarization of the NÀ Ph caused by the hindrance of the rotation of the bulky imide protecting group. [13] The fluorescence quantum yield (Φ F ) of 2 a and 2 b resulted consistently higher (Φ F = 0.10 and 0.25, respectively) compared to the Fukuzumi acridinium salt 1 b (Φ F = 0.02) ( Table 1). Such characteristics, as the fluorescence lifetime and quantum yield, were substantially lower for 1 b than for 1 a.…”