Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly ...to the electron–phonon coupling and ensuing thermal energetic disorder in some of the most widely studied high‐mobility molecular semiconductors, state‐of‐the‐art quantum mechanical simulations of the vibrational modes and the ensuing electron–phonon coupling constants are combined with experimental measurements of the low‐frequency vibrations using inelastic neutron scattering and terahertz time‐domain spectroscopy. In this way, the long‐axis sliding motion is identified as a “killer” phonon mode, which in some molecules contributes more than 80% to the total thermal disorder. Based on this insight, a way to rationalize mobility trends between different materials and derive important molecular design guidelines for new high‐mobility molecular semiconductors is suggested.
Molecular vibrations strongly impact the charge transport properties of weakly van der Waals bonded organic semiconductors. Quantum mechanical simulations, combined with low‐frequency vibrational spectroscopy, enable resolution of vibrational modes and ensuing electron–phonon coupling constants. The long‐axis sliding motion of molecular subunits is identified as a “killer” phonon mode, which in some materials contributes more than 80% to the total thermal disorder.
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Combining a bulky bis(amide) and a reactive one-coordinate TMP (2,2,6,6-tetramethylpiperidide) ligand, a new mixed K/Zn heteroleptic base has been developed for regioselective zincation of ...fluoroarenes. This special ligand set allows for trapping and structural authentication of the first intermediates of direct Zn-H exchange of fluoroarenes obtained
via
deprotonative metallation, providing mechanistic insights of the processes involved.
Providing unique structural insights, regioselective zincation of a range of fluoroarenes has been accomplished using a novel heterobimetallic K/Zn amide base.
The structural and electronic properties of four isomers of didodecyl1‐benzothieno3,2‐b1benzothiophene (C12‐BTBT) have been investigated. Results show the strong impact of the molecular packing on ...charge carrier transport and electronic polarization properties. Field‐induced time‐resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm2 V−1 s−1 for the 2,7‐isomer, holding great promise for the field of organic electronics.
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Detailed kinetic studies of the reaction of a model Ni0 complex with a range of aryl electrophiles have been conducted. The reactions proceed via a fast ligand exchange pre-equilibrium, followed by ...oxidative addition to produce either NiIX(dppf) (and biaryl) or NiII(Ar)X(dppf); the ortho substituent of the aryl halide determines selectivity between these possibilities. A reactivity scale is presented in which a range of substrates is quantitatively ranked in order of the rate at which they undergo oxidative addition. The rate of oxidative addition is loosely correlated to conversion in prototypical cross-coupling reactions. Substrates that lead to NiI products in kinetic experiments produce more homocoupling products under catalytic conditions.
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Merging two topical themes in main-group chemistry, namely, cooperative bimetallics and frustrated-Lewis-pair (FLP) activity, this Forum Article focuses on the cooperativity-induced outcomes observed ...when the tris(alkyl)gallium compound GaR3 (R = CH2SiMe3) is paired with the lithium amide LiTMP (TMP = 2,2,6,6-tetramethylpiperidide) or the sterically hindered N-heterocyclic carbene (NHC) 1,3-bis(tert-butyl)imidazol-2-ylidene (I t Bu). When some previously published work are drawn together with new results, unique tandem reactivities are presented that are driven by the steric mismatch between the individual reagents of these multicomponent reagents. Thus, the LiTMP/GaR3 combination, which on its own fails to form a cocomplex, functions as a highly regioselective base (LiTMP)/trap (GaR3) partnership for the metalation of N-heterocycles such as diazines, 1,3-benzoazoles, and 2-picolines in a trans-metal-trapping (TMT) process that stabilizes the emerging sensitive carbanions. Taking advantage of related steric incompatibility, a novel monometallic FLP system pairing GaR3 with I t Bu has been developed for the activation of carbonyl compounds (via CO insertion) and other molecules with acidic hydrogen atoms such as phenol and phenylacetylene. Shedding new light on how these non-cocomplexing partnerships operate and showcasing the potential of gallium reagents to engage in metalation reactions or FLP activations, areas where the use of this group 13 metal is scant, this Forum Article aims to stimulate more interest and activity toward the advancement of organogallium chemistry.
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The psychology of reading investigates the process by which readers extract visual information from written text and make sense of it. Psychology Library Editions: Psychology of Reading (11 Volumes) ...brings together as one set, or individual volumes, a small series of previously out-of-print titles, originally published between 1980 and 1995. The set includes topics such as dyslexia and the relationship between speech and reading.
Shattering the long‐held dogma that organolithium chemistry needs to be performed under inert atmospheres in toxic organic solvents, chemoselective addition of organolithium reagents to non‐activated ...imines and quinolines has been accomplished in green, biorenewable deep eutectic solvents (DESs) at room temperature and in the presence of air, establishing a novel and sustainable access to amines. Improving on existing methods, this approach proceeds in the absence of additives; occurs without competitive enolization, reduction or coupling processes; and reactions were completed in seconds. Comparing RLi reactivities in DESs with those observed in pure glycerol or THF suggests a kinetic anionic activation of the alkylating reagents occurs, favoring nucleophilic addition over competitive hydrolysis.
The green(air), the better! Moving closer to the dream of hydrous/aerobic organolithium chemistry, replacing toxic organic solvents by green and biorenewable deep eutectic solvents (DESs) enables regioselective addition of organolithium reagents to non‐activated imines at room temperature in air.
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Bimetallic complexes combining an alkali‐metal with a lower electropositive metal have demonstrated unique chemical profiles which can be rationalised in terms of chemical cooperativity. Advancing ...the rational design of these types of complexes, a adaptable method is described to prepare a new family of potassium metal(ates) containing the highly sterically demanding silyl(bis)amide {Ph2Si(NAr*)2}2− (Ar*=2,6‐diisopropylphenyl). Using a sequential deprotonative co‐complexation approach, mono‐metallation of Ph2Si(NHAr*)2 (1) is accomplished using potassium alkyl KCH2SiMe3 yielding {Ph2Si(NHAr*)(NAr*)K}∞ (2), which, in turn, undergoes co‐complexation with the relevant M(CH2SiMe3)2 (M=Mg, Zn, Mn) enabling metallation of the remaining NHAr* group to furnish silylbis(amido) alkyl potassium metal(ates) {Ph2Si(NAr*)2M(THF)x(CH2SiMe3)}−{K(THF)y}+ (M=Zn, x=0, y=4, 3; M=Mg, x=1, y=3, 4; and M=Mn, x=0, y=4, 5). Reactivity studies of potassium manganate 5 with the amine HMDS(H) (HMDS=NSiMe32 revealed the kinetic activation of the remaining alkyl group on Mn furnishing K(THF)2{Ph2Si(NAr*)2}Mn(HMDS) (6). The structures of these bimetallic complexes along with that of the potassium precursor 2 have been established by X‐ray crystallographic studies.
Deprotonative/Co‐complexation: Using a stepwise approach, a new series of silyl(bis)amide potassium metal(ates) has been prepared via initial monometalation of bis(amino)silane Ph2Si(NHAr*)2, by KCH2SiMe3 followed by co‐complexation with M(CH2SiMe3)2 (M=Zn, Mg and Mn), enabling the second metallation step to take place.
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Cooperativity between the Li and Al centres is implicated in catalytic hydroboration reactions of aldehydes and ketones with pinacolborane via heteroleptic lithium diamidodihydridoaluminates. In ...addition to implementing hydroalumination, these versatile heteroleptic ates can also perform as amido bases as illustrated with an acidic triazole.
The regioselectivity of deprotonation reactions between arene substrates and basic metalating agents is usually governed by the electronic and/or coordinative characteristics of a directing group ...attached to the benzene ring. Generally, the reaction takes place in the ortho position, adjacent to the substituent. Here, we introduce a protocol by which the metalating agent, a disodium-monomagnesium alkyl-amide, forms a template that extends regioselectivity to more distant arene sites. Depending on the nature of the directing group, ortho-meta′ or meta-meta′ dimetalation is observed, in the latter case breaking the dogma of ortho metalation. This concept is elaborated through the characterization of both organometallic intermediates and electrophilically quenched products.
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