Red to NIR-emissive anthracene-conjugated PMI dyes with dual functions: singlet-oxygen response and lipid-droplet imaging

Ultrafast symmetry-breaking charge separation in Perylenemonoimide-embedded multichromophores: impact of regioisomerism

Symmetry-breaking charge separation (SB-CS) has recently evolved as an emerging concept offering its potential to the latest generation of organic photovoltaics. However there are several concerns that need to be addressed to reach the state-of-the-art in SB-CS chemistry, for instance, the desirable molecular geometry, interchromophoric distance and extent of electronic coupling. To shed light on those features, it is reported herein, that ortho-functionalized perylene monoimide (PMI) constituted regioisomeric dimer and trimer derivatives with varied molecular twisting and electronic conjugation have been synthesized. In steady-state photophysical studies, all the dimers and trimer derivatives exhibit a larger bathochromic shift in the emission spectra and a significant reduction of fluorescence quantum yield in polar DMF. Among the series of multichromophores, ortho- and self-coupled dimers display the strikingly different optical feature of SB-CS with a very fast charge separation rate (τCS = 80.2 ps) upon photoexcitation in DMF, which is unveiled by femtosecond transient absorption (fs-TA) studies. The SB-CS for two dimers is well-supported by the formation of PMI˙+ and PMI˙- bands in the fs-TA spectra. Further analysis of fs-TA data revealed that, among the other multichromophores the trimer also exhibits a clear charge separation, whereas SB-CS signatures are less prominent, but can not be completely disregarded, for the meta- and para-dimers. Additionally, the charge separation dynamics of those above-mentioned PMI derivatives are devoid of a kinetically favorable excimer or triplet formation. The evidence of a profound charge transfer phenomenon in the ortho-dimer is characterized by density functional theory (DFT) calculations on excited state electronic structures. The excitonic communications in the excited state electronic arrangements unravel the key role of dihedral twisting in SB-CS. The thermodynamic feasibility of CS (ΔGCS) and activation barrier (ΔG≠) of the derivatives in DMF are established from the Rehm-Weller equation and Marcus's theory, respectively. This work is an in-depth study of the effect of mutual orientation of PMIs and regioisomerism in determining sustainable guidelines for using SB-CS.

Dyads and Triads of Boron Difluoride Formazanate and Boron Difluoride Dipyrromethene Dyes

Dye-dye conjugates have attracted significant interest for their utility in applications such as bioimaging, theranostics, and light-harvesting. Many classes of organic dyes have been employed in this regard; however, building blocks don't typically extend beyond small chromophores. This can lead to minor changes to the optoelectronic properties of the original dye. The exploration of dye-dye structures is impeded by long synthetic routes, incompatible synthetic conditions, or a mismatch of the desired properties. Here, we present the first-of-their-kind dye-dye conjugates of boron difluoride complexes of formazanate and dipyrromethene ligands. These conjugates exhibit dual photoluminescence bands that reach the near-infrared spectral region and implicate anti-Kasha processes. Cyclic voltammetry experiments revealed the generation of polyanionic species that can reversibly tolerate the uptake of up to 6 electrons. Ultimately, we demonstrate that BF2 formazanates can serve as a synthetically accessible platform to build upon new classes of dye-dye conjugates.

A perylenemonoimide-based fluorescent probe: ultrasensitive and selective tracing of endogenous peroxynitrite in living cells

Peroxynitrite (ONOO-), a highly reactive species, plays a key role in various physiological and pathological processes. Herein, a red-emitting fluorescent reporter perylenemonoimide-boronate ester (PMI-BE) was synthesized and utilized for ultrasensitive detection of ONOO-. The unique feature of PMI-BE is its nanomolar sensitivity with high selectivity towards ONOO-. Moreover, PMI-BE also detects endogenously generated ONOO- in live cells.

Perylene-Based Smart Fluoroprobe with Dual Function: Ratiometric Response toward Hazardous Organic Peroxides and Pure White Light Generation via Self-Assembly

In this report, we have designed and synthesized a perylene-based smart fluoroprobe (PBE) in which the perylene core has been functionalized with the boronate group at the peri-position. PBE shows a very fast and ratiometric response toward harmful organic peroxides (OPs) generated in old ethereal solvents via auto-oxidation. The response toward OPs takes place with a visible color change from green to yellow, which could be easily observed with the naked eye. The reaction between PBE and OPs involves the cleavage of the boronate group and its consequent conversion into the -OH group. The response of PBE toward OPs was monitored using UV-vis absorption, fluorescence emission, IR spectroscopy, and mass spectrometry. Additionally, we have also explored the self-assembly of PBE in an organic-aqueous solvent mixture, which shows pure white light emission (WLE) with the CIE coordinates (0.33, 0.33) in a 50% dimethyl sulfoxide-water mixture. This work clearly reveals that PBE fluoroprobe can be employed for sensitive detection of hazardous OPs present in old ethereal solvents. Moreover, the ability of PBE to generate the perfect pure WLE makes it a potential candidate for application in organic light-emitting devices.

Bioimaging of labile lysosomal iron through naphthalimide-based fluorescent probe

Lysosomal labile iron detection is immensely important as it is related to various diseases like Alzheimer's disease, Huntington's disease, Parkinson's disease, and cell apoptosis like ferroptosis. The fluorescent-based detection methods are preferred due to their sensitive, non-invasive, and spatial-temporal detection in biological samples. However, this remains a great challenge due to the lysosomal compartment being acidic alters the photophysical properties of the probe. Herein, we have rationally designed and synthesized multi-component naphthalimide-based fluorescent marker with preferred optical properties and bio-compatibility for selective detection of labile iron present in the lysosomal compartment. The synthesized probe was characterized structurally and optically by NMR, mass spectrometry, UV-visible, and fluorescence spectroscopy. The developed probe with an appropriate linking strategy turns out to be tolerant to fluorescence alternation in lysosomal pH. The probe exhibits great selectivity and high sensitivity for Fe(III) with limit of detection of 0.44 μM and is also able to detect Fenton-type reactions. Further, the probe has been successfully applied for lysosomal imaging and detecting labile Fe(III) present in the lysosomal lumen of the live cells.