Gary James Richards

A yellow chiral crystal shows red emission under UV and green SHG under NIR, exhibiting dual-mode optical response.

Early detection and late-stage cell fate assessment are key factors to develop therapeutic strategies, although current methods cannot capture early responses or distinguish multiple injury states, especially in ultraviolet-visible (UV-vis)–sensitive cells. Here, we introduce a method to simultaneously detect variations in RNA and DNA under near-infrared photoexcitation. Using a pyrazinacene-based probe ( TEG ₈ -N14 ), we unexpectedly achieved discrimination of multiple cell states, including apoptosis, necrosis, necroptosis, and senescence, based on RNA/DNA changes. Specifically, TEG ₈ -N14 selectively stains necrotic cells in live samples, while after fixation, it allows detection of ultraearly senescence in UV-vis–sensitive cells, providing approximately twofold greater informational content than existing RNA or DNA fluorophores. These findings break current imaging barriers by enabling comprehensive visualization of single-cell fate histories without being affected by UV-vis or genetic manipulation.

In single crystals of C–N atropisomeric N-(2-halophenyl)quinolin-2-one and the thione analogue, a unique association based on a halogen–π interaction was detected. In racemic and optically pure N-(2-bromo- or 2-chlorophenyl)quinolin-2-ones, homochiral layered polymers, which consist of (P)- or (M)-atropisomers, were formed through intermolecular halogen–π association. The halogen–π association in the racemates is due to a halogen bond (C–X···π) between a σ-hole on the halogen atom and a π-electron on the quinolinone benzene ring, while that in optically pure forms is caused by an n–π* interaction between a lone electron pair on the halogen atom and a π* orbital of the quinolinone. In contrast to the formation of the homochiral layered polymer in quinolinones, in racemic N-(2-bromophenyl)quinoline-2-thione, heterochiral layered polymers, in which (P)- and (M)-atropisomers were alternately connected, were formed through an n–π* interaction between a lone electron pair on the bromine atom and a π* orbital of the quinoline-2-thione.

Anaerobic digestors (ADs) have the potential to become a major green energy source in a future sustainable society. To achieve this, effective operational parameters of the reactors must be established and maintained preferably by automation. In situ monitoring and control of AD systems is currently a challenging matter based on inconsistent feedstuff composition and the complexity of the biological processes involved, so that reactor shutdowns associated with costly downtime are a common problem. Here, a sensing device is developed for the monitoring of volatile fatty acids (VFAs), key intermediates during bioreactor operation, in the headspaces of anaerobic reactors. The device is compact, contains a sensing element based on a self‐assembled molecular layer in conjunction with a nanomechanical sensor, and can be used to monitor VFA contents in bioreactors by estimating their relative contents in the reactor headspace in real time. This device allows the close monitoring of VFA concentrations in admixture toward cost‐effective operation of bioreactors by reducing or eliminating reactor downtime. It represents a simple solution to the problem of real‐time reactor monitoring, making anaerobic digesters a realistic alternative energy source.

Phenyl-substituted pyrazinacene and naphthalene form yellow and red co-crystal polymorphs via π-hole⋯π interactions. The red form, with a herringbone motif, shows tenfold enhanced emission via exciplex, while the yellow form has a columnar motif.

A new Donor‐Acceptor type pyrazinacene derivative (1) featuring strong ICT was synthesized by linking electron‐donating triphenylamine (TPA) and electron‐accepting CN groups via a pyrazinacene core. The compound exhibits a dramatic color change from greenish blue to red‐violet upon selective recognition of naphthalene (3) to form a 1:1 co‐crystal (1•3). This color change is induced by intermolecular CT between pyrazinacene and naphthalene's aromatic moieties, driven by π‐hole⋅⋅⋅π interactions. Crystal structure analysis and DFT calculations confirm that the molecular recognition process is facilitated by the unique π‐hole⋅⋅⋅π interactions, leading to a reversible color switching mechanism. The findings offer new insights into selective molecular recognition and ICT‐CT interplay in nonporous adaptive crystals.

Perfluorinated dinuclear metal complexes, [M₂L₂] (M = Ni²⁺ (1), Cu²⁺ (2), and H₂L = 1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one), were examined as host crystals to encapsulate alcohol molecules. Complex 1 was crystallized from EtOH and MeOH to give unique single crystals 1·2EtOH·2H₂O and 1·8MeOH, respectively, showing a unique hydrogen bonded motif of solvent molecules due to the hydrophobic crystalline cavities surrounded by the pentafluorophenyl moieties on the dinuclear Ni²⁺ sites. This open and specific cavity on the metals is not suitable for EtOH or H₂O in the crystallization process whereas MeOH, a physiologically harmful substance used in industry, is effectively and selectively encapsulated. The encapsulated MeOH molecules form tetrameric clusters that are stabilized by hydrogen bonding. Vapor adsorption of the powder samples shows reversible and accelerated recognition of alcohol only for the perfluorinated complex 1, while two coordination solvates were observed for 2.

Pyrazinacenes are linearly fused heteroaromatic rings, with N atoms replacing all apical CH moieties. Component rings may exist in a reduced state, having NH groups instead of N, causing cross-conjugation. These compounds have interesting optical and electronic properties, including strong fluorescence in the near-infrared region and photocatalytic properties, leading to diverse possible applications in bio-imaging and organic synthesis, as well as obvious molecular electronic uses. In this study, we investigated the behavior of seven-ring pyrazinacene 2,3,11,12-tetraphenyl-7,16-dihydro-1,4,5,6,7,8,9,12,13,14,15,16,17,18-tetradecaazaheptacene (Ph₄H₂N₁₄HEPT), with an emphasis on protic processes, including oxidation, tautomerism, deprotonation, and protonation, and the species resulting from those processes. We used computational methods to optimize the structures of the different species and generate/compare molecular orbital structures. The aromaticity of the species generated by the different processes was assessed using the nucleus-independent chemical shifts, and trends in the values were associated with the different transformations of the pyrazinacene core. The computational data were compared with experimental data obtained from synthetic samples of the molecule tBu₈Ph₄H₂N₁₄HEPT.

The reaction of allyl bromide derivatives with the enolate prepared from enantioenriched N-C axially chiral N-(2,5-di-tert-butylphenyl)-3,4-dihydroquinolin-2-one (lactam) and -thione (thiolactam) proceeded in a completely regio- and stereoselective manner to afford S_N2 and S_N2'-like products, respectively. Furthermore, through the conversion of thiolactam to lactam, the regiodivergent and stereoselective synthesis of N-C axially chiral lactams bearing a chiral tertiary α-carbon was achieved.