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A halogen-substituted cyclic disilene compound, bromocyclotrisilene, Si3Br(Eind)3 (3a), bearing fused-ring bulky Eind (a: R1 = R2 = Et) groups, has been synthesized as an extraordinarily air-stable compound by the reduction of 1,2-dibromodisilene, (Eind)BrSiâSiBr(Eind) (2a), or tribromosilane, (Eind)SiBr3 (1a), with the Mg or Li metal. The X-ray diffraction analysis of 3a showed that the disilene moiety has an almost planar, but slightly trans-bent structure. Even though 3a is quite air-stable both in solutions and in the solid state, its Si-Br bond is reactive under reducing conditions. The further treatment of 3a with the Li metal leads to the formation of room-temperature thermally stable silicon homologues of the cyclopropyl radical, i.e., the cyclotrisilanyl radicals (6a) [6a(syn) and 6a(anti)], via intramolecular C-H bond activation in a transient silicon homologue of the cyclopropenyl radical, i.e., the cyclotrisilenyl radical, [Si3(Eind)3]⢠(5a). The formation mechanism of 6a from 5a is discussed based on the theoretical calculations. The unique structural and electronic properties of these Si3 three-membered ring species incorporating the Eind groups have been experimentally and theoretically investigated.
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Isomerism in covalent organic frameworks (COFs) has scarcely been known. Here, for the first time we show 3D COFs with three framework isomers or polymorphs constructed from the same building blocks. All isomers were obtained as large (>10 µm) crystals; although their crystal shapes were distinctly different, they showed identical FT-IR and solid-state NMR spectra. Our structural analyses revealed unprecedented triple isomerism in 3D COFs (noninterpenetrated dia, qtz, and 3-fold interpenetrated dia-c3 nets). Furthermore, this Communication reports the first known COF with qtz topology for which the structure determination was based on Rietveld analysis. We achieved triple framework isomerism by reticulating a tetrahedral building block with a flexible junction and a linear building block with PEO side chains and by varying solution compositions. Our energy calculations, along with the discovery of interisomer transition, revealed that the isomer with qtz topology was a kinetic isomer. Thus, this simple yet little-explored concept of reticulating only flexible building blocks is an effective pathway to significantly broaden the diversity of 3D COFs, which have been proposed for a myriad of applications.
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Although second near-infrared (NIR-II, 1000-1500â nm) light has attracted considerable attention, especially for life sciences applications, the development of organic dyes with NIR-II absorption remains a formidable challenge. Herein we report the design, synthesis, and electronic properties of 20π-electron antiaromatic benziphthalocyanines (BPcs) that exhibit intense absorption bands in the NIR region. The strong, low-energy absorption of the antiaromatic BPcs is attributed to electric-dipole-allowed HOMO-LUMO transitions with narrow band gaps, enabled by the reduced structural symmetry of BPc compared with regular porphyrins and phthalocyanines. The combination of peripheral substituents and a central metal decreases the HOMO-LUMO energy gaps, leading to the extension of the absorption bands into the NIR-II region (reaching 1100â nm) under reductive conditions.
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A silyliumylidene ion 2 stabilized by two σ-donating Ni(0)- and Pd(0)-fragments was successfully synthesized. Due to the σ-donation of MâSi interactions, 2 presents a pyramidalized cationic silicon center with a localized lone pair. The additional coordination of basic Pd(0) fragment to the mono-Ni(0)-stabilized silyliumylidene 1 results in a higher HOMO level and an unchanged HOMO-LUMO gap and thus, 2 remains highly reactive. Interestingly, the coordination mode at the Si center is closely related to the nature of M-ligands. Indeed, the donor/donor-stabilized silyliumylidene ion 2 has been transformed into a donor/acceptor-stabilized ion 13, featuring a trigonal planar Si center with a vacant orbital, just via a ligand exchange reaction from PCy3/NHC toward PMe3.
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Next-generation biomedical devices1-9 will need to be self-powered and conformable to human skin or other tissue. Such devices would enable the accurate and continuous detection of physiological signals without the need for an external power supply or bulky connecting wires. Self-powering functionality could be provided by flexible photovoltaics that can adhere to moveable and complex three-dimensional biological tissues1-4 and skin5-9. Ultra-flexible organic power sources10-13 that can be wrapped around an object have proven mechanical and thermal stability in long-term operation13, making them potentially useful in human-compatible electronics. However, the integration of these power sources with functional electric devices including sensors has not yet been demonstrated because of their unstable output power under mechanical deformation and angular change. Also, it will be necessary to minimize high-temperature and energy-intensive processes10,12 when fabricating an integrated power source and sensor, because such processes can damage the active material of the functional device and deform the few-micrometre-thick polymeric substrates. Here we realize self-powered ultra-flexible electronic devices that can measure biometric signals with very high signal-to-noise ratios when applied to skin or other tissue. We integrated organic electrochemical transistors used as sensors with organic photovoltaic power sources on a one-micrometre-thick ultra-flexible substrate. A high-throughput room-temperature moulding process was used to form nano-grating morphologies (with a periodicity of 760 nanometres) on the charge transporting layers. This substantially increased the efficiency of the organophotovoltaics, giving a high power-conversion efficiency that reached 10.5 per cent and resulted in a high power-per-weight value of 11.46 watts per gram. The organic electrochemical transistors exhibited a transconductance of 0.8 millisiemens and fast responsivity above one kilohertz under physiological conditions, which resulted in a maximum signal-to-noise ratio of 40.02 decibels for cardiac signal detection. Our findings offer a general platform for next-generation self-powered electronics.
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Fontes de Energia Elétrica , Eletrônica/instrumentação , Monitorização Fisiológica/instrumentação , Nanotecnologia , Animais , Monitorização Hemodinâmica/instrumentação , Temperatura Alta , Humanos , Masculino , Nanotecnologia/instrumentação , Maleabilidade , Polímeros , Ratos , Transistores EletrônicosRESUMO
The treatment of the bulky Rind-based dibromosilanes, (Rind)2SiBr2 (2) [Rind = 1,1,7,7-tetra-R1-3,3,5,5-tetra-R2-s-hydrindacen-4-yl: EMind (a: R1 = Et, R2 = Me) and Eind (b: R1 = R2 = Et)], with two equivalents of tBuLi in Et2O at low temperatures resulted in the formation of blue solutions derived from the diarylsilylenes, (Rind)2Si: (3). Upon warming the solutions above -20 °C, the blue color gradually faded, accompanying the decomposition of 3 and yielding cyclic hydrosilanes (4) via intramolecular C-H bond insertion at the Si(II) center. The molecular structures of the bulky Eind-based 3b and 4b were confirmed by X-ray crystallography. Thus, at -20 °C, blue crystals were formed (Crystal-A), which were identified as mixed crystals of 3b and 4b. Additionally, colorless crystals of 4b as a singular component were isolated (Crystal-B), whose structure was also determined by an X-ray diffraction analysis. Although the isolation of 3 was difficult due to their thermally labile nature, their structural characteristics and electronic properties were discussed based on the experimental findings complemented by computational results. We also examined the hydrolysis of 3b to afford the silanol, (Eind)2SiH(OH) (5b).
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Temperatura Baixa , Fibras na Dieta , Cristalografia por Raios X , Eletrônica , HidróliseRESUMO
Strategic design for the construction of contiguous tetrasubstituted carbon centers represents a daunting challenge in synthetic organic chemistry. Herein, we report a combined experimental and computational investigation aimed at developing catalytic aerobic carbooxygenation, involving the intramolecular addition of tertiary radicals to geminally disubstituted alkenes, followed by aerobic oxygenation. This reaction provides a straightforward route to various α,α,ß,ß-tetrasubstituted γ-lactones, which can be readily transformed into hexasubstituted γ-lactones through allylation/translactonization. Computational analysis reveals that the key mechanistic foundation for achieving the developed aerobic carbooxygenation involves the design of endothermic (energetically uphill) C-C bond formation followed by exothermic (energetically downhill) oxygenation. Furthermore, we highlight a unique fluorine-induced stereoelectronic effect that stabilizes the endothermic stereodetermining transition state.
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Toward renewable energy for global leveling, compounds that can store ammonia (NH3), a carbon-free energy carrier of hydrogen, will be of great value. Here, we report an organic-inorganic halide perovskite compound that can chemically store NH3 through dynamic structural transformation. Upon NH3 uptake, a chemical structure change occurs from a one-dimensional columnar structure to a two-dimensional layered structure by addition reaction. NH3 uptake is estimated to be 10.2 mmol g-1 at 1 bar and 25 °C. In addition, NH3 extraction can be performed by a condensation reaction at 50 °C under vacuum. X-ray diffraction analysis reveals that reversible NH3 uptake/extraction originates from a cation/anion exchange reaction. This structural transformation shows the potential to integrate efficient uptake and extraction in a hybrid perovskite compound through chemical reaction. These findings will pave the way for further exploration of dynamic, reversible, and functionally useful compounds for chemical storage of NH3.
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The titanium dioxide (TiO2 ) photocatalyst is only active under UV irradiation due to its wide-gap nature. A novel excitation pathway denoted as interfacial charge transfer (IFCT) has been reported to activate copper(II) oxide nanoclusters-loaded TiO2 powder (Cu(II)/TiO2 ) under visible-light irradiation for only organic decomposition (downhill reaction) so far. Here, the photoelectrochemical study shows that the Cu(II)/TiO2 electrode exhibits a cathodic photoresponse under visible-light and UV irradiation. It originates from H2 evolution on the Cu(II)/TiO2 electrode, while O2 evolution takes place on the anodic side. Based on the concept of IFCT, a direct excitation of electrons from the valence band of TiO2 to Cu(II) clusters initiates the reaction. This is the first demonstration of a direct interfacial excitation-induced cathodic photoresponse for water splitting without any addition of a sacrificial agent. This study is expected to contribute to the development of abundant visible-light-active photocathode materials for fuel production (uphill reaction).
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Chiral Ni complexes have revolutionized both asymmetric acid-base and redox catalysis. However, the coordination isomerism of Ni complexes and their open-shell property still often hinder the elucidation of the origin of their observed stereoselectivity. Here, we report our experimental and computational investigations to clarify the mechanism of ß-nitrostyrene facial selectivity switching in Ni(II)-diamine-(OAc)2-catalyzed asymmetric Michael reactions. In the reaction with a dimethyl malonate, the Evans transition state (TS), in which the enolate binds in the same plane with the diamine ligand, is identified as the lowest-energy TS to promote C-C bond formation from the Si face in ß-nitrostyrene. In contrast, a detailed survey of the multiple potential pathways in the reaction with α-keto esters points to a clear preference for our proposed C-C bond-forming TS, in which the enolate coordinates to the Ni(II) center in apical-equatorial positions relative to the diamine ligand, thereby promoting Re face addition in ß-nitrostyrene. The N-H group plays a key orientational role in minimizing steric repulsion.
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Diaminas , Níquel , Níquel/química , Ligantes , Ácidos Carboxílicos , CatáliseRESUMO
Allenes (>C=C=C<) are classified as cumulated dienes with a linear structure and an sp-hybridized central carbon atom. We have synthesized and isolated a stable 2-germapropadiene with bulky silyl substituents. The 2-germapropadiene allene moiety adopts a linear structure both in the solid state and in solution. An X-ray diffraction electron-density-distribution (EDD) analysis of this 2-germapropadiene confirmed the linear C=Ge=C geometry with a formally sp-hybridized germanium atom that bears two orthogonal C=Ge π-bonds. Based on detailed structural and computational studies, we concluded that the linear geometry of the isolated 2-germapropadiene most likely arises from the negative hyperconjugation of the silyl substituents at the terminal carbon atoms. The 2-germapropadiene reacts rapidly with nucleophiles, indicating that the linearly oriented germanium atom is highly electrophilic.
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We present the experimental visualization of the valence-electron-density distribution in benzene and its kinetically stabilized heavier-element analogues, i.e., 1,2-disilabenzene and 1,2-digermabenzene. The valence-electron-density-distribution (EDD) analysis on the 1,2-disila- and 1,2-digermabenzenes revealed that these contain incompletely delocalized π electrons on their cyclic conjugation systems, making them less aromatic compared to benzene. Based on the results of this EDD analysis in combination with anisotropy of the current-induced density (ACID) calculations, considerable contributions from the characteristic resonance structures of 1,2-disila- and 1,2-digermabenzenes with cleaved EîE bonds can be expected.
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Reaction design in asymmetric catalysis has traditionally been predicated on a structurally robust scaffold in both substrates and catalysts, to reduce the number of possible diastereomeric transition states. Herein, we present the stereochemical dynamics in the Ni(II)-catalyzed diastereoconvergent (3 + 2) cycloadditions of isomerizable nitrile-conjugated nitrones with α-keto ester enolates. Even in the presence of multiple equilibrating species, the catalytic protocol displays a wide substrate scope to access a range of CN-containing building blocks bearing adjacent stereocenters with high enantio- and diastereoselectivities. Our computational investigations suggest that the enantioselectivity is governed in the deprotonation process to form (Z)-Ni-enolates, while the unique syn addition is mainly controlled by weak noncovalent bonding interactions between the nitrone and ligand.
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We report on our investigation of C-C bonding longer than 2.0 Å, which can be realized by perpendicularly facing two fluorenyl rings in the title compound. A small orbital overlap between the distantly positioned carbon atoms is observed as a small concentration of electrons on the X-ray electron density map. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the compound originate from the in-phase and out-of-phase interactions of the overlapping orbitals, respectively, with a gap of 2.39 eV. Solid-state 13C NMR spectroscopy shows a sharp peak at 82.9 ppm for the long-bonded carbons, and a CASSCF(6,6) calculation indicates small diradical character. The experimental and theoretical analyses reveal sufficient covalent-bonding interaction in the long-bonded carbon pair.
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Layer flexibility in two-dimensional coordination polymers (2D-CPs) contributes to several functional materials as it results in anisotropic structural response to external stimuli. Chemical modification is a common technique for modifying layer structures. This study demonstrates that crystal morphology of a cyanide-bridged 2D-CP of type [Mn(salen)]2 [ReN(CN)4 ] (1) consisting of flexible undulating layers significantly impacts the layer configuration and assembly. Nanoplates of 1 showed an in-plane contraction of layers with a longer interlayer distance compared to the micrometer-sized rod-type particles. These effects by crystal morphology on the structure of the 2D-CP impacted the structural flexibility, resulting in dual-functional changes: the enhancement of the sensitivity of structural transformation to water adsorption and modification of anisotropic thermal expansion of 1. Moreover, the nanoplates incorporated new adsorption sites within the layers, resulting in the uptake of an additional water molecule compared to the micrometer-sized rods.
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We created dual interactive sites in a porous coordination network using a CuI cluster and a rotation-restricted ligand, tetra(3-pyridyl)phenylmethane (3-TPPM). The dual interactive sites of iodide and Cu ions can adsorb I2 via four-step processes including two chemisorption processes. Initially, one I2 molecule was physisorbed in a pore and successively chemisorbed on iodide sites of the pore surface, and then the next I2 molecule was physisorbed and chemisorbed on Cu ions to form a cross-linked network. We revealed the four-step I2 diffusion process by single-crystal X-ray structure determination and spectroscopic kinetic analysis.
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We prepared coordination networks that show relatively strong emission with through-space charge-transfer (TSCT) transitions. Thermolysis of a kinetically assembled network with Cu2Br2 dimer connectors, which was assembled from a CuBr cluster and the Td ligand 4-4-tetrapyridyltetraphenylmethane (4-TPPM), generated a highly luminescent network composed of Cu+ connectors and 4-TPPM linkers with CuBr2- guests. We clarified that the electronic transitions in this network include TSCT in addition to the typical metal-ligand charge transfer (MLCT) observed in conventional Cu complexes.
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Graphitic carbon nitride (GCN) has garnered broad research interest due to its unique catalytic properties. However, GCN, prepared by general methods, possesses myriad structural defects and it has been difficult to elucidate their intrinsic physical properties. We report the development of azacalix[3]triazines (AC3Ts), a substructure of triazine-based GCN (Tz-GCN). Despite the electron-deficient natures of triazine, AC3Ts capture protons as organic superbases. We reveal the unique anion-π interactions of AC3Ts that alters the ionization potentials of AC3Ts. To the best of our knowledge, these features have not yet been recognized for Tz-GCN. These unveiled features of AC3Ts are expected to expand the usage scope and possibilities for GCNs.
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A novel stable donor/acceptor-supported MnI -metallasilanone 3 was synthesized. The intramolecular silanone-MnI interaction induces a highly strained three-membered cyclic structure, leading to an exceptionally high reactivity of 3 as a donor/acceptor complex of silanone. Indeed, metallasilanone 3 readily reacts with various small molecules such as H2 or ethylene gas in mild conditions.
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Polar materials attract wide research interest due to their unique properties, such as ferroelectricity and the bulk photovoltaic effect (BPVE), which are not accessible with nonpolar materials. However, in general, rationally designing polar materials is difficult because nonpolar materials are more favorable in terms of dipole-dipole interactions. Here, we report a rational strategy to form polar assemblies with bowl-shaped π-conjugated molecules and a molecular design principle for this strategy. We synthesized and thoroughly characterized 12 single crystals with the help of various theoretical calculations. Furthermore, we demonstrated that it can be possible to predict whether polar assemblies become more favorable or not by estimating their lattice energies. We believe that this study contributes to the development of organic polar materials and their related studies.