Efficient Microwave-Assisted Synthesis of Sonogashira-Coupled Perylene Monoimide Derivatives: Impact of Electron-Donating Groups on Optoelectronic Properties

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.

1-Substituted Perylene Derivatives by Anionic Cyclodehydrogenation: Analysis of the Reaction Mechanism

Perylene derivatives constitute a promising class of compounds with technological applications mainly due to their optoelectronic properties. One mechanism proposed to synthesize them, starting from binaphthyl derivatives, is anionic cyclodehydrogenation (under reductive conditions). However, the scope of this reaction is limited. In the present study, we report a theoretical and experimental analysis of this particular reaction mechanism for its use in the synthesis of 1-substituted perylenes. Different substituents at position 2 of 1,1'-binaphthalene were evaluated: -OCH₃, -OSi(CH₃)₂C(CH₃)₃, and -N(CH₃)₂. Based on density functional theory (DFT) calculations on the proposed mechanism, we suggest that the cyclization takes place from binaphthyl dianion instead of its radical anion. This dianion has an open-shell diradical nature, and this could be the species that was detected by EPR in previous studies. The O-substituted derivatives could not afford the perylene derivatives since their radical anions fragment and the necessary binaphthyl dianion could not be formed. On the other hand, 49% of N,N-dimethylperylen-1-amine was obtained starting from the N-substituted 2-binapthyl derivative as a substrate, employing a simpler experimental methodology.

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

The rich chemistry of solution-processable red and near-infrared (NIR) organic emitters has emerged as an attractive and progressive research field because of their particular applications in organic optoelectronics and bioimaging. Also, one can see that the research area of perylene monoimide-based red and NIR-emissive fluorophores is underexplored, which prompted us to design and synthesize three anthracene-conjugated PMI dyes exhibiting strong emission in the red and NIR window in solution. Three PMI-based fluorophores were synthesized via conjoining anthracene and donor moieties (-Ph, -N,N-PhNMe₂) with a PMI core via an acetylene linkage at the peri-position, which helped to attain extensive electronic conjugation, which was reflected in red and NIR-emission in solution. The key molecular features to be highlighted here are: all three dyes are strongly emissive in solution, as unveiled by the excellent absolute fluorescence QYs; and they possess tuneable emission properties, guided by the donor strength and a profound Stokes shift (100-200 nm). The three fluorescent dyes demonstrated appreciable singlet-oxygen (¹O₂) sensitivity when photoirradiated with methylene blue (MB) in solution, showing a substantial blue-shift in emission in a ratiometric manner. Further, the treatment of dye-MB solution with α-tocopherol (¹O₂ scavenger) validated the presence of ¹O₂ as the only oxidizing species generated by MB in solution. Computational investigations gave insight into the twisting of donor moieties in their ground-state optimized geometries, the modulation of the FMO energy gap, and the thermodynamic feasibility of the ¹O₂ reaction. Finally, via taking advantage of the red and NIR-emission, we successfully utilized one of the fluorophores as a lipid-droplet marker for bioimaging in HepG2 cells.

Synthesis and photovoltaic application of NIR-emitting perylene-monoimide dyes with large Stokes-shift

An efficient Sonogashira coupling protocol is developed for tetra-alkynylation at the bay and peri-positions of the perylene-monoimide (PMI) dye in its PMI(Br)4 form. The absorption band for these PMI dyes covered from the visible to Near-infrared (NIR) region and PMI(NMe2)4 is found to exhibit a record-breaking Stokes-shifted NIR emission with good photovoltaic properties.

Synthesis of highly-soluble push-pull perylenemonoimide derivatives by regioselective peri-functionalization for switchable memory applications

A regioselective synthetic protocol is developed via tetrabromination of perylenemonoimide (PMI) which leads to a series of PMI derivatives. The push-pull characteristics of these derivatives are established by spectroscopic and theoretical investigations. Finally, the semiconducting properties of the PMI dyes are utilized for the development of a switchable memory device.

Deciphering micro-polarity inside the endoplasmic reticulum using a two-photon active solvatofluorochromic probe

A new class of two-photon active and solvatofluorochromic dyes for the determination of ER polarity is reported. The fluorescent colour spans almost the entire visible spectrum. One of the derivatives is rationally designed for specific ER targeting. Finally, the fluorescence spectral scanning technique has been utilised to determine the micro-polarity inside the ER which is found to be much lower than that of water.

Visible-Light-Triggered Generation of Ultrastable Radical Anion from Nitro-substituted Perylenediimides

An efficient method for visible-light-triggered generation of radicals from mono- and dinitro-substituted perylenediimide derivatives is developed. UV-vis-NIR and electron paramagnetic resonance measurements were carried out to confirm the formation of radicals. Most importantly, these radical anions were remarkably stable for several months. Subsequently, the reversible nature of anions was validated by both chemical and spectroelectrochemical methods for applications in electrochromic materials.

Large Stokes-shifted NIR-emission from nanospace-induced aggregation of perylenemonoimide-doped polymer nanoparticles: imaging of folate receptor expression

The development of a water-soluble, perylenemonoimide (PMI) dye-doped polymer nanoparticle (PNP) with NIR emission for live-cell imaging is demonstrated. The large Stokes-shifted NIR emission is due to confined nanospace-induced aggregation offered by the polymer matrix. Later, folic acid functionalised PNP (PNP-FA) is successfully employed to differentiate folate receptor positive and negative cancer cells.