Furan-Containing Singlet Oxygen-Responsive Conjugated Polymers

Tuning the 1O2 Oxidation of a Phenol at the Air/Solid Interface of a Nanoparticle: Hydrophobic Surface Increases Oxophilicity

Although silica surfaces have been used in organic oxidations for the production of peroxides, studies of airborne singlet oxygen at interfaces are limited and have not found widespread advantages. Here, with prenyl phenol-coated silica and delivery of singlet oxygen (¹O₂) through the gas phase, we uncover significant selectivity for dihydrofuran formation over allylic hydroperoxide formation. The hydrophobic particle causes prenyl phenol to produce an iso-hydroperoxide intermediate with an internally protonated oxygen atom, which leads to dihydrofuran formation as well as O atom transfer. In contrast, hydrophilic particles cause prenyl phenol to produce allylic hydroperoxide, due to phenol OH hydrogen bonding with SiOH surface groups. Mechanistic insight is provided by air/nanoparticle interfaces coated with the prenyl phenol, in which product yield was 6-fold greater on the hydrophobic nanoparticles compared to the hydrophilic nanoparticles and total rate constants (ASI-k_T) of ¹O₂ were 13-fold greater on the hydrophobic vs hydrophilic nanoparticles. A slope intersection method was also developed that uses the airborne ¹O₂ lifetime (τ_airborne) and surface-associated ¹O₂ lifetime (τ_surf) to quantitate ¹O₂ transitioning from volatile to non-volatile and surface boundary (surface···¹O₂). Further mechanistic insights on the selectivity of the reaction of prenyl phenol with ¹O₂ was provided by density functional theory calculations.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.

Synthesis of 2,5-Diaryl Nonsymmetric Furans C6-Platform Chemicals via Catalytic Conversion of Biomass and the Formal Synthesis of Dantrolene

Biomass-derived commodity chemical 5-hydroxymethyl furfural is an underutilized C6-platform chemical derived from cellulose that is ideal to prepare next-generation value-added products. We have developed an efficient synthetic strategy to access 2,5-diaryl nonsymmetric furans from 5-hydroxymethyl furfural utilizing decarboxylative cross-couplings. A key finding was that the presence of the hydroxymethyl handle enhances the yields of the palladium-catalyzed decarboxylative cross-coupling reaction. The method provides access to a broad-range nonsymmetric 2,5-diaryl furans where each arene can be systematically introduced as required. Additionally, this green synthetic strategy was employed for a formal synthesis of the muscle relaxant Dantrolene in excellent yields.

Conjugated polymers as Langmuir and Langmuir-Blodgett films: Challenges and applications in nanostructured devices

Initially developed for classic systems composed of fatty acids and phospholipids, the Langmuir and Langmuir-Blodgett (LB) techniques allow the fabrication of nanometer-scale devices at self-assembly interfaces with high control over the thickness and molecular architecture. Their application in the research and production of new plastic materials has grown considerably over the past few decades due to the efficiency of conjugated polymers (CPs) for the production of light-emitting diodes, flexible displays, solar cells, and other photoelectronic devices. The structuring of polymers at different interfaces is not trivial as this class of macromolecules can undergo through different processes of folding/unfolding, which hinders the formation of stable Langmuir monolayers and, consequently, the production of Langmuir-Blodgett films. With these ideas in mind, the present article aims to review a series of elements related to the formation of stable Langmuir and Langmuir-Blodgett films of CPs, especially those based on poly(phenylene vinylene)s, polyfluorenes, and polythiophenes. This review is divided into two parts where we first discuss the formation of neat CP films, and then the strategies for the formation of stable CP films based on the co-immobilization with fatty acids, other polymers, and enzymes as mixed films.

Chemical tools for the generation and detection of singlet oxygen

Growing evidence indicates intermediacy of singlet dioxygen (1O2) in a variety of pathophysiological processes. 1O2 has also found great utility of destructive actions for clinical and environmental applications. However, many details of the molecular mechanisms mediated by 1O2 remain insufficiently understood. Efforts to elucidate the 1O2 chemistry have been hampered by the lack of chemical tools capable of generation and detection of 1O2. In this review, I summarize the recent advances in the development of the chemical tools of 1O2. This article focuses on two topics. The first part introduces chemical methods for ground-state generation of 1O2. Designs of the molecular carriers of 1O2 are also explained. The second part discloses molecular probes of 1O2. The probes are categorized into three groups, depending on signaling modalities: absorption-based probes, photoluminescent probes, and chemiluminescent probes. Focus is on the molecular design to maximize the signaling actions. Disadvantages of using the probes are also discussed to motivate the future research. I hope that this review will serve as helpful guidance to the exploitation and development of the chemical tools of 1O2.

Visible-Light Induced Direct Synthesis of Polysubstituted Furans from Cyclopropyl Ketones

In this article, a photoredox protocol for the synthesis of furans via oxidative coupling of olefin generated in situ from cyclopropyl ketones with ketonic oxygen atom is presented. Moreover, bromination of furans in the presence of overstoichiometric oxidant has been achieved with high regioselectivity.

A singlet oxygen photosensitizer enables photoluminescent monitoring of singlet oxygen doses

Dichromophoric molecular dyad enables photosensitization and detection of sinlget oxygen.

Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira-Glaser cyclization sequence

2,5-Di(hetero)arylfurans are readily accessible in a pseudo five-component reaction via a Sonogashira–Glaser coupling sequence followed by a superbase-mediated (KOH/DMSO) cyclization in a consecutive one-pot fashion. Besides the straightforward synthesis of natural products and biologically active molecules all representatives are particularly interesting due to their bright blue luminescence with remarkably high quantum yields. The electronic structure of the title compounds is additionally studied with DFT computations.

Poly(mono-, bi- or trifuran): effect of oligomer chain length on the electropolymerization performances and polymer properties

Herein we demonstrated the effect of oligomer chain length on the electropolymerization and properties of the resulting polyfuran films.

Furans and singlet oxygen – why there is more to come from this powerful partnership

Using the reaction of furans with singlet oxygen as a means to rapidly access huge structural diversity in a green & sustainable way.