Triplet-triplet annihilation (TTA)-mediated photon upconversion (UC) offers a promising route for transforming low-energy photons into higher-energy ones under low-power, incoherent excitation, with applications in photovoltaics, bioimaging, 3D printing, etc. However, a central constraint on UC efficiency is the limited spin-statistical factor (f), which dictates the yield of singlet state formation and is especially challenging in the desirable far-red/NIR spectral range. Here, we explore a new approach of tuning the annihilator's f factor through controlled aggregation. The study covers a systematic investigation of triethylsilyl-substituted anthradithiophene (TES-ADT) annihilator solutions across a range of concentrations, complemented by studies on a neat TES-ADT film and density functional theory (DFT) calculations. We report a remarkable 3-fold enhancement in singlet yield, boosting the f value from ca. 20% to an impressive ca. 60% upon increasing annihilator concentration, which is shown to be directly linked to annihilator aggregation. DFT calculations further suggest that dimerization-induced shifts in energy levels and the accessibility of higher-energy triplet states (up to T6) facilitate spin-conversion processes. Our findings unveil aggregation-enhanced singlet generation via TTA in TES-ADT, providing a valuable insight for designing more efficient UC systems by tailoring energy landscapes through molecular packing.

The ability to introduce modular C1 units directly into arene C-H bonds remains a fundamental challenge in synthetic design, limiting access to highly diversified molecular architectures from simple feedstocks. We disclose a photoredox-neutral platform that enables direct transfer of a methylene pyridinium linchpin to unactivated arenes, transforming inert C-H sites into versatile synthetic handles. The resulting benzylpyridinium products function as broadly addressable intermediates, supporting a wide range of C-C and C-heteroatom bond formation and granting streamlined access to medicinally privileged substituted methyls.

The ability to introduce modular C1 units directly into arene C-H bonds remains a fundamental challenge in synthetic design, limiting access to highly diversified molecular architectures from simple feedstocks. We disclose a photoredox-neutral platform that enables direct transfer of a methylene pyridinium linchpin to unactivated arenes, transforming inert C-H sites into versatile synthetic handles. The resulting benzylpyridinium products function as broadly addressable intermediates, supporting a wide range of C-C and C-heteroatom bond formation and granting streamlined access to medicinally privileged substituted methyls.

ABSTRACT Shifting action spectrum of azobenzene‐based photopharmaceuticals toward bio‐optical window is highly desired, since red/far‐red light offers improved tissue penetration and reduced cellular toxicity. While unidirectional photoswitching (trans‐to‐cis and cis‐to‐trans) of azobenzenes (AZO) with red/far‐red light is known in separate systems, achieving bidirectional photoswitching in a single system faces issues of spectral overlaps. Here, bidirectional photoswitching of a tailored azobenzene is achieved in a single bio‐relevant solution with red and far‐red light excitation. A new azobenzene molecule (AZO‐N) bearing four ortho‐methoxy, and one para‐N donor lipophile is synthesized. The AZO‐N exhibits separate n‐π* absorption bands and triplet energies for trans and cis isomers. As a result, trans‐to‐cis photoswitching is observed upon 625 nm excitation at the tail of the red‐shifted n‐π*absorption band via direct absorption, whereas cis‐to‐trans photoswitching is enabled upon 730 nm excitation through triplet sensitization. Further, triplet sensitization of AZO‐based molecules could lead to singlet oxygen generation—experiments in the presence of serum albumin and glutathione (biological oxidative stress addressors), suggest no effect of singlet oxygen on the triplet‐sensitization of cis‐AZO‐N, and non‐significant change in the fingerprint all‐α secondary structure of serum albumin. This advance presents modular design principles to develop practically functional azo‐based photopharmaceuticals.

Multi-photon photopolymerisation (MPP) based on organic-inorganic resins has emerged as a promising technique for the fabrication of complex three-dimensional nano- and micro-structures. Among the prepolymers used for MPP, SZ2080™, synthesised via sol-gel method, stands out for its hybrid nature, comprised of an organic and inorganic network. This photoresist is usually photosensitised with the photoinitiators IRG369 and Michler's ketone, that are responsible for initiating polymerisation. The incorporation of these photoinitiators induces significant changes in the ground-state absorption of the material and enables a broad fabrication window. Despite its broad application, the fundamental processes governing the performance of SZ2080™ remain poorly understood. In this study, we systematically investigate the optical characteristics of SZ2080™ sensitised with IRG369 and Michler's ketone using UV/Vis absorption, steady-state fluorescence, Raman, along with Fourier-transformed infrared and nuclear magnetic resonance (NMR) spectroscopies. The UV/Vis spectra reveal pronounced alterations in ground-state absorption, suggesting coordination-related interactions. Vibrational spectroscopy further supports these findings, indicating that the observed modifications are linked to changes in the inorganic network of SZ2080™. Finally, 1H NMR confirms that the diethylamino groups of Michler's ketone, along with the carbonyl groups of IRG369, coordinate with the Zr(iv) centres in the SZ2080™ matrix. The link between spectroscopic characterisation and MPP fabrication highlights that controlled complex formation could greatly improve the fabrication window.

Novel stimuli-responsive zwitterionic modules based on ureidopyrimidinone and isocytosine scaffolds are presented in this work.

Two hydrogen-bonding monomers containing tetraethylene glycol (TEG) chains have been synthesized and characterized. The monomers are based on a bicyclic scaffold appended with either 4H-bonding benzyl-substituted ureidopyrimidinone motifs or 2H-bonding unsubstituted pyrrole-fused ureidopyrimidinone motifs, with the TEG chains introduced with the aim of developing amphiphilic monomers soluble in nonpolar and polar organic solvents in order to extend the utility of H-bonding in supramolecular chemistry. In CDCl3, both monomers formed cyclic tetramers. The monomer containing 2H-bonding motifs was found to form significantly less-stable aggregates than its previously reported alkylated analogue, most likely due to interference from the TEG chains. Despite the weaker aggregation, the 2H-bonded tetramers were able to stack into tubular polymers through orthogonal H-bonding in less polar solvent (toluene) or when a suitable guest (C70) was introduced. Comparison of the TEGylated monomers with previously reported alkylated analogues showed that the introduction of TEG chains resulted in increased solubility in a wide range of solvents. By using one of the TEGylated monomers, nonpolar C60 could be solubilized in polar solvent acetonitrile by forming an inclusion complex. This complex was used as a homogeneous catalyst for photochemical oxidation of sulfides to sulfoxides in acetonitrile.

Incoherent photon upconversion (UC) mediated by triplet-triplet annihilation (TTA) offers multiple implementation pathways, from bio-related applications to energy harvesting in photovoltaics. Despite its potential, TTA-UC efficiency in the near-infrared (NIR) range is notably low, particularly in solid-state systems. Rubrene (Rub), a key annihilator in this spectral range, faces significant concentration quenching, primarily due to singlet fission (SF). To mitigate this issue, herein, the cyano (CN) functionalization of Rub is explored to reduce SF and boost solid-state UC performance. By systematically increasing the number of CN groups, the modified Rub is examined in both solution and solid-state environments, benchmarking it against unmodified Rub and assessing each energy transfer step. The findings reveal that CN modification, while detrimental to UC efficiency in solution, markedly improves solid-state UC performance. Specifically, Rub functionalized with two peripheral CN groups achieves a UC quantum yield (Phi UC) of 3.0% (out of a theoretical maximum of 50%) in the solid-state-nearly tripling the maximum yield achieved with unmodified Rub. This advancement not only presents a more efficient and stable alternative to conventional Rub annihilators but also highlights the potential of CN-tuning for enhancing other NIR annihilators in the solid state.

Rapid reverse intersystem crossing (RISC) is one of the prime concerns for blue thermally activated delayed fluorescence (TADF) emitters, as it reduces triplet exciton population, the root cause of detrimental triplet-mediated annihilation processes that accelerate device efficiency roll-off and degradation. This work introduces a new concept to tailor the RISC of TADF emitters through their molecular geometry adaptation to crystalline hosts bearing a similar donor-acceptor structure. A meticulously designed crystalline host comprising isophthalonitrile acceptor (A) and carbazole-derived donor (D) units, characterized by nearly orthogonal D-A arrangement, has been demonstrated to alleviate singlet-triplet energy gap (Delta EST) of the TADF dopant by forcing it to adopt a more twisted D-A configuration, as corroborated by X-ray diffraction (XRD) measurements. The approach not only significantly reduces the RISC activation energy, resulting in a remarkable tenfold boost of the RISC rate (above 107 s-1) and fourfold shortening of delayed FL lifetime (down to 1.5 mu s), but also offers the additional benefit of suppressing conformational disorder of TADF dopant, producing a narrower emission bandwidth. The presented concept, based on crystalline host-driven RISC engineering, is anticipated to have a profound impact on the development of high-performance, stable blue-emitting TADF organic light-emitting diodes (OLEDs). This work introduces a new concept to tailor the RISC of TADF emitters through their molecular geometry adaptation to crystalline hosts bearing a similar donor-acceptor structure. The approach significantly reduces the RISC activation energy, resulting in a remarkable tenfold boost of the RISC rate (above 107 s-1). image

Rapid access to both enantiomers of vellosimine and its derivatives is secured from a readily affordable C2-symmetric 9-azabicyclo[3.3.1]nonane precursor available in both enantiomeric forms. The strategy reported leverages desymmetrization via intramolecular cyclization used to assemble the key intermediate with two differentiated carbonyl groups. Late-stage site selective indolization enables a concise synthesis of vellosimines and a straightforward diversification of the alkaloid scaffold.

A supramolecular chiral hydrogen-bonded tetrameric aggregate possessing a large cavity and tetraarylporphyrin substituents was assembled using alternating 4H- and 2H-bonds between ureidopyrimidinone and isocytosine units, respectively. The aggregation mode was rationally shifted from social to narcissistic self-sorting by changing urea substituent size only. The H-bonded tetramer forms a strong complex with C60 guest, at the same time undergoing remarkable structural changes. Namely, the cavity adjusts to the guest via keto-to-enol tautomerization of the ureidopyrimidinone unit and as a result, porphyrin substituents move apart from each other in a scissor blade-like opening fashion. The rearrangement is accompanied by C–H···π interaction between the alkyl solubilizing groups and the nearby placed porphyrin π-systems. The latter interaction was found to be crucial for the guest complexation event, providing energetic compensation for otherwise costly tautomerization. We showed that only the systems possessing sufficiently long alkyl chains capable of interacting with a porphyrin ring are able to form a complex with C60. The structural rearrangement of the tetramer was quantitatively characterized by electron paramagnetic resonance pulsed dipolar spectroscopy measurements using photogenerated triplets of porphyrin and C60 as spin probes. Further exploring the C–H···π interaction as a decisive element for the C60 recognition, we investigated the guest-induced self-sorting phenomenon using scrambled tetramer assemblies composed of two types of monomers possessing alkyl chains of different lengths. The presence of the fullerene guest has enabled the selective scavenging of monomers capable of C–H···π interaction to form homo-tetrameric aggregates.

Diketopyrrolopyrrole derivatives demonstrating moderate NIR-to-Vis TTA-mediated photon upconversion quantum yield (up to 3.8% out of 50%) and statistical probability f (up to 15.6%) are promoted as stable alternatives to a rubrene emitter.

We report a straightforward method for creating large-area, microscale resolution patterns of functional amines on self-assembled monolayers by the photoinduced local acidification of a flat elastomeric stamp enriched with photoacid. The limited diffusivity of the photoactivated merocyanine acid in poly(dimethylsiloxane) (PDMS) enabled to confine efficient deprotection of N-tert-butyloxycarbonyl amino group (N-Boc) to line widths below 10 μm. The experimental setup is very simple and is built around the conventional HD-DVD optical pickup. The method allows cost-efficient, maskless, large-area chemical patterning while avoiding potentially cytotoxic photochemical reaction products. The activation of the embedded photoacid occurs within the stamp upon illumination with the laser beam and the process is fully reversible. Preliminary positive results highlight the possibility of repeatable use of the same stamp for the creation of different patterns.

Balanced charge carrier transport and broad carrier recombination zone are essential features for reducing triplet exciton concentration and suppressing triplet-mediated annihilation processes, which affect the performance and stability of blue-emitting organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) phenomenon. Doping of organic layers is among the most effective methods to control these features. Herein, the impact of ytterbium (Yb) doping of electron transport layer on the TADF-OLED performance, and particularly the lifetime, was thoroughly assessed. It was found that the lower doping concentrations of Yb (<10 wt%) cause electron trapping and reduced current density, whereas higher Yb concentrations facilitate electron transport in the device. Although the introduction of Yb somewhat deteriorated device efficiency, it extended operational lifetime of blue-emitting device by 2 orders of magnitude (up to 46 hours at 1000 cd/m(2)). This was shown to occur as a result of Yb-assisted non-radiative triplet exciton quenching at the electron transport and emission layer interface, thus diminishing detrimental exciton annihilation processes.(c) 2023 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

We report on the binding properties of deep cavitands for various industrial pollutants in water. Depending on the guest type, monomeric cavitands, dimeric capsules or both acted as receptors and formed complexes. The complexation studies revealed unique binding modes of long n-alkyl chain alcohols and n-alkylbenzenes. In cavitands, the hydroxy group of alcohols was found to be anchored at the polar rim while the rest of the chain undergoes fast coiling and folding. In capsules, regioselective bending of the polar end was observed. Accommodation of n-alkylbenzenes in capsules proceeded through folding of the alkyl chain over the aromatic ring. Water-miscible pollutants tetrahydropyran and 1,4-dioxane were also complexed by cavitands in aqueous media. The reported findings suggest the future use of water soluble cavitands in industrial waste treatment.