More Like this

1. Plasmon-driven photocatalytic molecular transformations on metallic nanostructure surfaces: mechanistic insights gained from plasmon-enhanced Raman spectroscopy

   https://doi.org/10.1039/d1me00016k  

   Chen, Kexun; Wang, Hui (April 2021, Molecular Systems Design & Engineering)

   null (Ed.)

   Optically excited plasmonic nanostructures exhibit unique capabilities to catalyze interfacial chemical transformations of molecules adsorbed on their surfaces in a regioselective manner through anomalous reaction pathways that are inaccessible under thermal conditions. The mechanistic complexity of plasmon-driven photocatalysis is intimately tied to a series of photophysical and photochemical processes associated with the radiative and non-radiative decay of localized plasmon resonances in metallic nanostructures. Plasmon-enhanced Raman spectroscopy combines ultrahigh detection sensitivity with unique time-resolving and molecular finger-printing capabilities, ideal for detailed kinetic and mechanistic studies of photocatalytic interfacial transformations of molecular adsorbates residing in the plasmonic hot spots. Through systematic case studies of several representative reactions, we demonstrate how plasmon-enhanced Raman spectroscopy can be judiciously utilized as a unique in situ spectroscopic tool to fine-resolve the detailed molecule-transforming processes on the surfaces of optically excited plasmonic nanostructures in real time during the photocatalytic reactions. We further epitomize the mechanistic insights gained from in situ plasmon-enhanced Raman spectroscopic measurements into several central materials design principles that can be employed to guide the rational optimization of the photocatalyst structures and the nanostructure-molecule interfaces for plasmon-mediated surface chemistry. 

   more » « less
2. Highly Strained para-Phenylene-Bridged Macrocycles from Unstrained 1,4-Diketo Macrocycles

   https://doi.org/10.1055/s-0036-1589081  

   Mitra, Nirmal; Merryman, Caroline; Merner, Bradley (October 2017, Synlett)

   The conversion of macrocyclic 1,4-diketones to highly strained para-phenylene rings has recently been reported by our laboratory. This synthetic strategy represents a non-cross-coupling-based approach to arene-bridged macrocycles, and an alternative to palladium- and nickel-mediated processes. In this Synpacts article we discuss the development of endgame aromatization protocols for the synthesis of increasingly strained arene systems, as well as potential advantages of the macrocyclic 1,4-diketone approach to selectively functionalized benzenoid macrocycles for future complexity building reactions. 1 Introduction 2 A Non-Cross-Coupling-Based Approach to Arene-Bridged Macro cycles 3 Macrocyclic 1,4-Diketones: Streamlined Synthesis and Size-­Dependent Diastereoselective Grignard Reactions 4 Dehydrative Aromatization Reactions: A Powerful Tool for Synthesizing Highly Strained para-Phenylene Units 5 Conclusion 

   more » « less
3. Experimental and Computational Exploration of para ‐Selective Silylation with a Hydrogen‐Bonded Template

   https://doi.org/10.1002/anie.201708449  

   Maji, Arun; Guin, Srimanta; Feng, Sheng; Dahiya, Amit; Singh, Vikas Kumar; Liu, Peng; Maiti, Debabrata (October 2017, Angewandte Chemie International Edition)

   Abstract The regioselective conversion of C−H bonds into C−Si bonds is extremely important owing to the natural abundance and non‐toxicity of silicon. Classical silylation reactions often suffer from poor functional group compatibility, low atom economy, and insufficient regioselectivity. Herein, we disclose a template‐assisted method for the regioselectivepara silylation of toluene derivatives. A new template was designed, and the origin of selectivity was analyzed experimentally and computationally. An interesting substrate–solvent hydrogen‐bonding interaction was observed. Kinetic, spectroscopic, and computational studies shed light on the reaction mechanism. The synthetic significance of this strategy was highlighted by the generation of a precursor of a potential lipophilic bioisostere of γ‐aminobutyric acid (GABA), various late‐stage diversifications, and by mimicking enzymatic transformations. 

   more » « less
4. Modeling Current-Potential Responses of Homogeneous-Heterogeneous Photocathodes

   Wadsworth, B. L.; Beiler, A. M; Khusnutdinova, D.; Moore, G. F. (April 2019, Abstract of Papers, Materials and Research Society Spring Meeting and Exhibit)

   Chemical modification of semiconductor surfaces with molecular electrocatalysts provides a strategy for developing integrated homogeneous-heterogeneous materials capable of converting sunlight to fuels and other value-added products, but their development is hampered by an incomplete understanding of the factors limiting their performance. Although kinetic models have been separately developed to describe photoelectrochemical or homogeneous electrocatalytic reactions, related modeling for molecular-modified hybrid photoelectrodes has not been as extensively elaborated. This presentation addresses the interplay between light absorption, charge transfer, and catalytic activity during photoelectrosynthetic transformations at a molecular-modified semiconductor surface. The analysis provides opportunities to better understand the principles governing these hierarchal constructs and develop improved photocatalytic assemblies. 

   more » « less
5. Deciphering the mechanism of the Ni-photocatalyzed C‒O cross-coupling reaction using a tridentate pyridinophane ligand

   https://doi.org/10.1038/s41467-022-28948-8  

   Na, Hanah; Mirica, Liviu M. (March 2022, Nature Communications)

   Abstract Photoredox nickel catalysis has emerged as a powerful strategy for cross-coupling reactions. Although the involvement of paramagnetic Ni(I)/Ni(III) species as active intermediates in the catalytic cycle has been proposed, a thorough spectroscopic investigation of these species is lacking. Herein, we report the tridentate pyridinophane ligands^RN3 that allow for detailed mechanistic studies of the photocatalytic C–O coupling reaction. The derived (^RN3)Ni complexes are active catalysts under mild conditions and without an additional photocatalyst. We also provide direct evidence for the key steps involving paramagnetic Ni species in the proposed catalytic cycle: the oxidative addition of an aryl halide to a Ni(I) species, the ligand exchange/transmetalation at a Ni(III) center, and the C–O reductive elimination from a Ni(III) species. Overall, the present work suggests the^RN3 ligands are a practical platform for mechanistic studies of Ni-catalyzed reactions and for the development of new catalytic applications. 

   more » « less