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Developing dopant‐free hole transporting materials (HTMs) is of vital importance for addressing the notorious stability issue of perovskite solar cells (PSCs). However, efficient dopant‐free HTMs are scarce. Herein, we improve the performance of dopant‐free HTMs featuring with a quinoxaline core via rational π‐extension. Upon incorporating rotatable or chemically fixed thienyl substitutes on the pyrazine ring, the resulting molecular HTMs TQ3 and TQ4 show completely different molecular arrangement as well as charge transporting capabilities. Comparing with TQ3, the coplanar π‐extended quinoxaline based TQ4 endows enriched intermolecular interactions and stronger π–π stacking, thus achieving a higher hole mobility of 2.08×10−4 cm2 V−1 s−1. It also shows matched energy levels and high thermal stability for application in PSCs. Planar n‐i‐p structured PSCs employing dopant‐free TQ4 as HTM exhibits power conversion efficiency (PCE) over 21 % with excellent long‐term stability. [ABSTRACT FROM AUTHOR]

With perovskite‐based solar cells (PSCs) now reaching efficiencies of greater than 20 %, the stability of PSC devices has become a critical challenge for commercialization. However, most efficient hole‐transporting materials (HTMs) thus far still rely on the state‐of‐the‐art methoxy triphenylamine (MOTPA) donor unit in which methoxy groups usually reduce the device stability. Herein, a carbazole‐fluorene hybrid has been employed as a methoxy‐free donor to construct organic HTMs. The indeno[1,2‐b]carbazole group not only inherits the characteristics of carbazole and fluorene, but also exhibits additional advantages arising from the bulky planar structure. Consequently, M129, endowed with indeno[1,2‐b]carbazole simultaneously exhibits a promising efficiency of over 20 % and superior long‐term stability. The hybrid strategy toward the methoxy‐free donor opens a new avenue for developing efficient and stable HTMs. [ABSTRACT FROM AUTHOR]

S-Adenosylmethionine (SAM) is one of the most common co-substrates in enzyme-catalyzed methylation reactions. Most SAM-dependent reactions proceed through an SN2 mechanism, whereas a subset of them involves radical intermediates for methylating non-nucleophilic substrates. Herein, we report the characterization and mechanistic investigation of NosN, a class C radical SAM methyltransferase involved in the biosynthesis of the thiopeptide antibiotic nosiheptide. We show that, in contrast to all known SAM-dependent methyltransferases, NosN does not produce S-adenosylhomocysteine (SAH) as a co-product. Instead, NosN converts SAM into 5′-methylthioadenosine as a direct methyl donor, employing a radical-based mechanism for methylation and releasing 5′-thioadenosine as a co-product. A series of biochemical and computational studies allowed us to propose a comprehensive mechanism for NosN catalysis, which represents a new paradigm for enzyme-catalyzed methylation reactions. [ABSTRACT FROM AUTHOR]

The radical S-adenosyl- l-methionine (SAM) enzyme NosL catalyzes the transformation of l-tryptophan into 3-methyl-2-indolic acid (MIA), which is a key intermediate in the biosynthesis of a clinically interesting antibiotic nosiheptide. NosL catalysis was investigated by using the substrate analogue 2-methyl-3-(indol-3-yl)propanoic acid (MIPA), which can be converted into MIA by NosL. Biochemical assays with different MIPA isotopomers in D2O and H2O unambiguously indicated that the 5′-deoxyadenosyl (dAdo)-radical-mediated hydrogen abstraction is from the amino group of l-tryptophan and not a protein residue. Surprisingly, the dAdo-radical-mediated hydrogen abstraction occurs at two different sites of MIPA, thereby partitioning the substrate into different reaction pathways. Together with identification of an α,β-unsaturated ketone shunt product, our study provides valuable mechanistic insight into NosL catalysis and highlights the remarkable catalytic flexibility of radical SAM enzymes. [ABSTRACT FROM AUTHOR]

A simple and robust microfluidic device was developed to synthesize organometallic polymers with highly organized structures. The device is compatible with organic solvents. Reactants are loaded into pairs of reservoirs connected by a 15 cm long microchannel prefilled with solvents, thus allowing long-term counter diffusion for self-assembly of organometallic polymers. The process can be monitored, and the resulting crystalline polymers are harvested without damage. The device was used to synthesize three insoluble silver acetylides as single crystals of X-ray diffraction quality. Importantly, for the first time, the single-crystal structure of silver phenylacetylide was determined. The reported approach may have wide applications, such as crystallization of membrane proteins, synthesis and crystal growth of organic, inorganic, and polymeric coordination compounds, whose single crystals cannot be obtained using traditional methods. [ABSTRACT FROM AUTHOR]

Direct aromatization of cyclohexanones to synthesize substituted phenols represents a significant challenge in modern synthetic chemistry. Herein, we describe a novel ene‐reductase (TsER) catalytic system that converts substituted cyclohexanones into the corresponding phenols. This process involves the successive dehydrogenation of two saturated carbon‐carbon bonds within the six‐membered ring of cyclohexanones and utilizes molecular oxygen to drive the reaction cycle. It demonstrates a versatile and efficient approach for the synthesis of substituted phenols, providing a valuable complement to existing chemical methodologies. [ABSTRACT FROM AUTHOR]