Design of Weak‐Donor Alkyl‐Functionalized Push–Pull Pyrene Dyes Exhibiting Enhanced Fluorescence Quantum Yields and Unique On/Off Switching Properties

Abstract

We designed, synthesized, and evaluated environmentally responsive solvatochromic fluorescent dyes by incorporating weak push-pull moieties. The quantum yields of the push (alkyl)-pull (formyl) pyrene dyes were dramatically enhanced by the introduction of alkyl groups into formylpyrene (1-formylpyrene: Φ(F) =0.10; 3,6,8-tri-n-butyl-1-formylpyrene: Φ(F) =0.90; in MeOH). The new dyes exhibited unique sensitivity to solvent polarity and hydrogen-bond donor ability, and specific fluorescence turn-on/off properties (e.g., 3,6,8-tri-n-butyl-1-formylpyrene: Φ(F) =0.004, 0.80, 0.37, and 0.90 in hexane, chloroform, DMSO, and MeOH, respectively). Here, the alkyl groups act as weak donors to suppress intersystem crossing by destabilizing the HOMOs of 1-formylpyrene while maintaining weak intramolecular charge-transfer properties. By using alkyl groups as weak donors, environmentally responsive, and in particular, pH-responsive fluorescent materials may be developed in the future.

Directional Control of π-Conjugation Enabled by Distortion of the Donor Plane in Diarylaminoanthracenes: A Photophysical Study

“…Table also reveals that with the increase in the planarity of the diarylamine moieties, the nonradiative transition rate increases, which is usually observed for measurements in other solvents (Table S8). We have previously pointed out , that excited states with enhanced charge separations and far-red-shifted emissions are more likely to be quenched by internal conversion according to the energy gap rule . Also intersystem crossing should be considered as a deactivation path since anthracene undergoes rapid intersystem crossing due to a narrow S 1 –T 2 gap. , 9,10-Substitution of anthracene suppresses the S 1 –T 2 intersystem crossing , by lowering the S 1 level, and therefore, this type of intersystem crossing is unlikely to happen on our system.…”

The Coumarin‐Dimer Spring—The Struggle between Charge Transfer and Steric Interactions

“…The obvious key elements to the construction of such structures are the push–pull π‐conjugated building blocks . Such molecules possessing high dipole moments are a key class of dye widely employed both in practical applications as well as in various types of research . Their popularity stems from the appreciable combination of optical properties, such as high fluorescence quantum yield, large Stokes shift, and polarity‐sensitive fluorescence .…”

Fluorescent Solvatochromic Probes for Long‐Term Imaging of Lipid Order in Living Cells

“…The photostability of aromatic esters can be explained by photophysical processes using energy diagrams such as those used for Prodan derivatives. [10,20] Moreover, we have explored strategies for suppressing and manipulating ISC and photodegradation by fine-tuning their 𝜋-systems. However, achieving a delicate equilibrium between molecular size and planarity is crucial, as it directly influences biocompatibility and invasiveness.…”

“…[9] Subsequently, in 2013, we also designed the Prodan analog, pyrene (PA), to maintain high quantum yields from nonpolar (Φ fl 0.88 in n-hexane) to polar (Φ fl 0.85 in methanol) solvents. [10] PA was successfully used to identify the distribution of cholesterol and sphingomyelin clusters in model membranes in 2016. [11] However, aldehydes react with intracellular substrates or residues, leading to modifications of the chromophore and loss of luminescent properties.…”