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1.
Anurag Noonikara-Poyil Shawn G. Ridlen Israel Fernndez H. V. Rasika Dias 《Chemical science》2022,13(24):7190
Copper and silver play important roles in acetylene transformations but isolable molecules with acetylene bonded to Cu(i) and Ag(i) ions are scarce. This report describes the stabilization of π-acetylene complexes of such metal ions supported by fluorinated and non-fluorinated, pyrazole-based chelators. These Cu(i) and Ag(i) complexes were formed readily in solutions under an atmosphere of excess acetylene and the appropriate ligand supported metal precursor, and could be isolated as crystalline solids, enabling complete characterization using multiple tools including X-ray crystallography. Molecules that display κ2-or κ3-ligand coordination modes and trigonal planar or tetrahedral metal centers have been observed. Different trends in coordination shifts of the acetylenic carbon resonance were revealed by 13C NMR spectroscopy for the Cu(i) and Ag(i) complexes. The reduction in acetylene C C due to metal ion coordination is relatively large for copper adducts. Computational tools were also used to quantitatively understand in detail the bonding situation in these species. It is found that the interaction between the transition metal fragment and the acetylene ligand is significantly stronger in the copper complexes, which is consistent with the experimental findings. The C C distance of these copper and silver acetylene complexes resulting from routine X-ray models suffers due to incomplete deconvolution of thermal smearing and anisotropy of the electron density in acetylene, and is shorter than expected. A method to estimate the C C distance of these metal complexes based on their experimental C C is also presented.Gaseous acetylene can be trapped on copper(i) and silver(i) sites supported by pyrazole-based scorpionates to produce isolable molecules for detailed investigations and the study of metal-acetylene bonding. 相似文献
2.
Juchao Yan Reid W. Wilson Jason T. Buck David C. Grills Eric W. Reinheimer Tomoyasu Mani 《Chemical science》2021,12(36):12107
Conjugated molecular chains have the potential to act as “molecular wires” that can be employed in a variety of technologies, including catalysis, molecular electronics, and quantum information technologies. Their successful application relies on a detailed understanding of the factors governing the electronic energy landscape and the dynamics of electrons in such molecules. We can gain insights into the energetics and dynamics of charges in conjugated molecules using time-resolved infrared (TRIR) detection combined with pulse radiolysis. Nitrile ν(C N) bands can act as IR probes for charges, based on IR frequency shifts, because of their exquisite sensitivity to the degree of electron delocalization and induced electric field. Here, we show that the IR intensity and linewidth can also provide unique and complementary information on the nature of charges. Quantifications of IR intensity and linewidth in a series of nitrile-functionalized oligophenylenes reveal that the C N vibration is coupled to the nuclear and electronic structural changes, which become more prominent when an excess charge is present. We synthesized a new series of ladder-type oligophenylenes that possess planar aromatic structures, as revealed by X-ray crystallography. Using these, we demonstrate that C N vibrations can report charge fluctuations associated with nuclear movements, namely those driven by motions of flexible dihedral angles. This happens only when a charge has room to fluctuate in space.Quantification of the intensity and linewidth of the ν(C N) IR band in a series of neutral and anionic nitrile-functionalized oligophenylenes reveals that the C N vibration is coupled to nuclear and electronic structural changes. 相似文献
3.
The denitrogenative reductive coupling of two molecules of CNtBu to afford a disilylketenimine with an aza-disilacyclobutane skeleton was achieved on a multinuclear silylene-bridged Ni cluster framework in the absence of any strong reducing reagents. During this reaction, sequential cleavage of a C N bond and formation of a C C bond involving two molecules of CNtBu were achieved on a nickel cluster surrounded by four silylene moieties. First, the cleavage of the C N bond of one molecule of CNtBu provided a silylene-supported carbide and an NtBu moiety on the dinuclear nickel skeleton. Further metalation induced coupling between the carbide moiety and an additional molecule of CNtBu on the pentanuclear nickel-cluster framework to form a moiety via formation of a C C bond. Thermolysis of this pentanuclear cluster produced a disilylketenimine with an aza-disilacyclobutane skeleton in 58% yield.The denitrogenative reductive coupling of two molecules of CNtBu was achieved on a multinuclear silylene-bridged Ni cluster framework, and two possible intermediary Ni clusters were isolated. 相似文献
4.
Rui Guo Xin Zhang Tong Li Qianli Li David A. Ruiz Liu Leo Liu Chen-Ho Tung Lingbing Kong 《Chemical science》2022,13(8):2303
A cationic terminal iminoborane [Mes*N B ← IPr2Me2][AlBr4] (3+[AlBr4]−) (Mes* = 2,4,6-tri-tert-butylphenyl and IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) has been synthesized and characterized. The employment of an aryl group and N-heterocyclic carbene (NHC) ligand enables 3+[AlBr4]− to exhibit both B-centered Lewis acidity and BN multiple bond reactivities, thus allowing for the construction of tri-coordinate boron cations 5+–12+. More importantly, initial reactions involving coordination, addition, and [2 + 3] cycloadditions have been observed for the cationic iminoborane, demonstrating the potential to build numerous organoboron species via several synthetic routes.An NHC-stabilized aryliminoboryl cation exhibits both boron-centered Lewis acidity and multiple bond reactivity and could be utilized as an effective synthon for unusual cationic boron species. 相似文献
5.
Jing Xiang Min Peng Yi Pan Li-Juan Luo Shun-Cheung Cheng Xin-Xin Jin Shek-Man Yiu Wai-Lun Man Chi-Chiu Ko Kai-Chung Lau Tai-Chu Lau 《Chemical science》2021,12(43):14494
N-Dealkylation of amines by metal oxo intermediates (M O) is related to drug detoxification and DNA repair in biological systems. In this study, we report the first example of N-dealkylation of various alkylamines by a luminescent osmium(vi) nitrido complex induced by visible light.The visible light-induced N-dealkylation of various alkylamines by a luminescent osmium(vi) nitrido complex has been investigated. We provide definitive evidence that these reactions occur via an ET/PT mechanism.High-valent metal oxo (M O) species play key roles in many chemical and biological oxidation processes.1 They are versatile oxidants that can perform oxidation of substrates via a variety of pathways, including electron transfer, H-atom transfer, hydride transfer and O-atom transfer. In principle, high-valent metal nitrido (M N) complexes should also function as versatile oxidants similar to M O. Although there have been significant advances in M N oxidation chemistry in recent years, the reactivity of M N is still rather limited in scope compared to M O.2 M N is intrinsically less oxidizing than M O due to the stronger electron donating property of the N3− ligand than the O2− ligand. Attempts to increase the oxidizing power of M N by increasing the oxidation state or by using less electron-donating ancillary ligands often led to decomposition of the complexes, mainly due to facile coupling of the nitrido ligands to yield N2 (2M N → 2M + N2).3 One appealing strategy to enhance the reactivity of M N is photochemical excitation. We have recently designed an osmium(vi) nitrido complex [OsVI(N)(L)(CN)3]− (NO2-OsN, HL = 2-(2-hydroxy-5-nitrophenyl)benzoxazole) that is strongly luminescent in the solid state and in fluid solutions.4 It readily absorbs visible light to generate a long-lived and highly oxidizing excited state with a redox potential of ca. 1.4 V. The excited state of this complex also possesses [Os N˙] nitridyl characteristics that enable it to readily abstract H-atoms from inert organic substrates.5We report herein the visible-light induced N-dealkylation of various alkylamines by NO2-OsN. Iron oxo species have been used by heme and nonheme enzymes to carry out N-dealkylation reactions of tertiary amines, which are important processes involved in detoxification and DNA repair.6 A number of synthetic iron(iv) oxo complexes are also able to carry out such N-dealkylation reactions.7 Mechanistic studies using cytochrome P450 and synthetic iron oxo complexes indicate that there are two possible mechanisms for N-dealkylation of amines, namely hydrogen-atom transfer (HAT) and electron transfer–proton transfer (ET–PT) (Fig. 1).8 In this work we report the first example of N-dealkylation of various aromatic as well as aliphatic tertiary amines by a nitrido complex upon visible light excitation. We also provide unambiguous evidence that these reactions occur via an ET/PT mechanism.Open in a separate windowFig. 1Two possible mechanisms for N-demethylation of tertiary amines by cytochrome P450 and synthetic Fe(iv) oxo complexes (P = porphyrin). 相似文献
6.
Ram Pratap Yoshinori Tominaga Milton L. Lee Raymond N. Castle 《Journal of heterocyclic chemistry》1981,18(5):973-975
The synthesis of all the isomers of pyreno[b]thiophene namely, pyreno[1,2-b]thiophene, pyreno[2,1-b]thiophene and pyreno[4,5-b]thiophene is described. Their spectral characteristics are also discussed. 相似文献
7.
Spencer A. Kerns Junhyeok Seo Vincent M. Lynch Jason Shearer Sean T. Goralski Eileen R. Sullivan Michael J. Rose 《Chemical science》2021,12(38):12838
We report the synthesis and reactivity of a model of [Fe]-hydrogenase derived from an anthracene-based scaffold that includes the endogenous, organometallic acyl(methylene) donor. In comparison to other non-scaffolded acyl-containing complexes, the complex described herein retains molecularly well-defined chemistry upon addition of multiple equivalents of exogenous base. Clean deprotonation of the acyl(methylene) C–H bond with a phenolate base results in the formation of a dimeric motif that contains a new Fe–C(methine) bond resulting from coordination of the deprotonated methylene unit to an adjacent iron center. This effective second carbanion in the ligand framework was demonstrated to drive heterolytic H2 activation across the Fe(ii) center. However, this process results in reductive elimination and liberation of the ligand to extrude a lower-valent Fe–carbonyl complex. Through a series of isotopic labelling experiments, structural characterization (XRD, XAS), and spectroscopic characterization (IR, NMR, EXAFS), a mechanistic pathway is presented for H2/hydride-induced loss of the organometallic acyl unit (i.e. pyCH2–C O → pyCH3+C O). The known reduced hydride species [HFe(CO)4]− and [HFe3(CO)11]− have been observed as products by 1H/2H NMR and IR spectroscopies, as well as independent syntheses of PNP[HFe(CO)4]. The former species (i.e. [HFe(CO)4]−) is deduced to be the actual hydride transfer agent in the hydride transfer reaction (nominally catalyzed by the title compound) to a biomimetic substrate ([TolIm](BArF) = fluorinated imidazolium as hydride acceptor). This work provides mechanistic insight into the reasons for lack of functional biomimetic behavior (hydride transfer) in acyl(methylene)pyridine based mimics of [Fe]-hydrogenase.We report the synthesis and reactivity of a model of [Fe]-hydrogenase derived from an anthracene-based scaffold that includes the endogenous, organometallic acyl(methylene) donor. 相似文献
8.
Connor W. Frye Dominic T. Egger Errikos Kounalis Adam J. Pearce Yukun Cheng Ian A. Tonks 《Chemical science》2022,13(5):1469
α-Diimines are commonly used as supporting ligands for a variety of transition metal-catalyzed processes, most notably in α-olefin polymerization. They are also precursors to valuable synthetic targets, such as chiral 1,2-diamines. Their synthesis is usually performed through acid-catalyzed condensation of amines with α-diketones. Despite the simplicity of this approach, accessing unsymmetrical α-diimines is challenging. Herein, we report the Ti-mediated intermolecular diimination of alkynes to afford a variety of symmetrical and unsymmetrical α-diimines through the reaction of diazatitanacyclohexadiene intermediates with C-nitrosos. These diazatitanacycles can be readily accessed in situ via the multicomponent coupling of Ti NR imidos with alkynes and nitriles. The formation of α-diimines is achieved through formal [4 + 2]-cycloaddition of the C-nitroso to the Ti and γ-carbon of the diazatitanacyclohexadiene followed by two subsequent cycloreversion steps to eliminate nitrile and afford the α-diimine and a Ti oxo.Alkyne diimination to unsymmetric α-diimines can be achieved via multicomponent reaction of Ti imidos and C-nitrosos. C-nitroso [4 + 2] cycloaddition across a diazatitanacyclohexadiene initiates cascading retrocycloadditions, liberating the α-diimine. 相似文献
9.
Greggory T. Kent Xiaojuan Yu Guang Wu Jochen Autschbach Trevor W. Hayton 《Chemical science》2021,12(43):14383
The reaction of [AnCl(NR2)3] (An = U, Th, R = SiMe3) with in situ generated lithium-3,3-diphenylcyclopropene results in the formation of [{(NR2)3}An(CH C CPh2)] (An = U, 1; Th, 2) in good yields after work-up. Deprotonation of 1 or 2 with LDA/2.2.2-cryptand results in formation of the anionic allenylidenes, [Li(2.2.2-cryptand)][{(NR2)3}An(CCCPh2)] (An = U, 3; Th, 4). The calculated 13C NMR chemical shifts of the Cα, Cβ, and Cγ nuclei in 2 and 4 nicely reproduce the experimentally assigned order, and exhibit a characteristic spin–orbit induced downfield shift at Cα due to involvement of the 5f orbitals in the Th–C bonds. Additionally, the bonding analyses for 3 and 4 show a delocalized multi-center character of the ligand π orbitals involving the actinide. While a single–triple–single-bond resonance structure (e.g., An–C C–CPh2) predominates, the An C C CPh2 resonance form contributes, as well, more so for 3 than for 4.The actinide allenylidenes [{(NR2)3}An(CCCPh2)]− (An = U, Th, R = SiMe3) feature significant ligand-to-metal donation bonding and partial An C double bond character. 相似文献
10.
Megan Keener Farzaneh Fadaei-Tirani Rosario Scopelliti Ivica Zivkovic Marinella Mazzanti 《Chemical science》2022,13(27):8025
Multimetallic-multielectron cooperativity plays a key role in the metal-mediated cleavage of N2 to nitrides (N3−). In particular, low-valent uranium complexes coupled with strong alkali metal reducing agents can lead to N2 cleavage, but often, it is ambiguous how many electrons are transferred from the uranium centers to cleave N2. Herein, we designed new dinuclear uranium nitride complexes presenting a combination of electronically diverse ancillary ligands to promote the multielectron transformation of N2. Two heteroleptic diuranium nitride complexes, [K{UIV(OSi(OtBu)3)(N(SiMe3)2)2}2(μ-N)] (1) and [Cs{UIV(OSi(OtBu)3)2(N(SiMe3)2)}2(μ-N)] (3-Cs), containing different combinations of OSi(OtBu)3 and N(SiMe3)2 ancillary ligands, were synthesized. We found that both complexes could be reduced to their U(iii)/U(iv) analogues, and the complex, [K2{UIV/III(OSi(OtBu)3)2(N(SiMe3)2)}2(μ-N)] (6-K), could be further reduced to a putative U(iii)/U(iii) species that is capable of promoting the 4e− reduction of N2, yielding the N24−complex [K3{UV(OSi(OtBu)3)2(N(SiMe3)2)}2(μ-N)(μ-η2:η2-N2)], 7. Parallel N2 reduction pathways were also identified, leading to the isolation of N2 cleavage products, [K3{UVI(OSi(OtBu)3)2(N(SiMe3)2)( N)}(μ-N)2{UV(OSi(OtBu)3)2(N(SiMe3)2)}]2, 8, and [K4{(OSi(OtBu)3)2UV)( N)}(μ-NH)(μ-κ2:C,N-CH2SiMe2NSiMe3)-{UV(OSi(OtBu)3)2][K(N(SiMe3)2]2, 9. These complexes provide the first example of N2 cleavage to nitride by a uranium complex in the absence of reducing alkali metals.Combinations of ligands were used to tune U N U complexes yielding a U(iii)/U(iii) nitride, which activates N2. Parallel N2 reduction pathways were identified, leading to the first example of N2 cleavage by U without external alkali reducing agents. 相似文献
11.
Self-assembly of platinum(ii) complexes to form supramolecular structures/nanostructures due to intermolecular ligand π–π stacking and metal–ligand dispersive interactions is widely used to develop functional molecular materials, but the application of such non-covalent molecular interactions has scarcely been explored in medical science. Herein is described the unprecedented biological properties of platinum(ii) complexes relevant to induction of cancer cell death via manifesting such intermolecular interactions. With conjugation of a glucose moiety to the planar platinum(ii) terpyridyl scaffold, the water-soluble complex [Pt(tpy)(C CArOGlu)](CF3SO3) (1a, tpy = 2,2′:6′,2′′-terpyridine, Glu = glucose) is able to self-assemble into about 100 nm nanoparticles in physiological medium, be taken up by lung cancer cells via energy-dependent endocytosis, and eventually transform into other superstructures distributed in endosomal/lysosomal and mitochondrial compartments apparently following cleavage of the glycosidic linkage. Accompanying the formation of platinum-containing superstructures are increased autophagic vacuole formation, lysosomal membrane permeabilization, and mitochondrial membrane depolarization, as well as anti-tumor activity of 1a in a mouse xenograft model. These findings highlight the dynamic, multi-stage extracellular and intracellular supramolecular self-assembly of planar platinum(ii) complexes driven by modular intermolecular interactions with potential anti-cancer application.Self-assembly of platinum(ii) glycosylated arylacetylide gave transformable superstructures upon enzymatic action in cellulo, leading to perturbation of an autophagy-lysosomal system and cancer cell death. 相似文献
12.
L. Bukowski 《Chemistry of Heterocyclic Compounds》2002,38(7):828-835
New imidazo[4,5-b]pyridine derivatives with various substituents in the 2-position (,-unsaturated ketones, imines, 2-pyrazolines, pyrimidines, 1,2,3,4-tetrahydropyrimidines) and derivatives of the new pyrido[3',2':4,5]imidazo[1,2-d][1,2,4]triazine ring system were synthesized. Biological data for selected compounds are presented. 相似文献
13.
Li-Hui Mou Yao Li Gong-Ping Wei Zi-Yu Li Qing-Yu Liu Hui Chen Sheng-Gui He 《Chemical science》2022,13(32):9366
The direct coupling of dinitrogen (N2) and methane (CH4) to construct the N–C bond is a fascinating but challenging approach for the energy-saving synthesis of N-containing organic compounds. Herein we identified a likely reaction pathway for N–C coupling from N2 and CH4 mediated by heteronuclear metal cluster anions CoTaC2−, which starts with the dissociative adsorption of N2 on CoTaC2− to generate a Taδ+–Ntδ− (terminal-nitrogen) Lewis acid–base pair (LABP), followed by the further activation of CH4 by CoTaC2N2− to construct the N–C bond. The N N cleavage by CoTaC2− affording two N atoms with strong charge buffering ability plays a key part, which facilitates the H3C–H cleavage via the LABP mechanism and the N–C formation via a CH3 migration mechanism. A novel Nt triggering strategy to couple N2 and CH4 molecules using metal clusters was accordingly proposed, which provides a new idea for the direct synthesis of N-containing compounds.A possible N–C bond formation directly from N2 and CH4 mediated by heteronuclear metal cluster anions CoTaC2− at room temperature was identified. 相似文献
14.
Lu Zhang Rongxiu Zhu Aili Feng Changyin Zhao Lei Chen Guidong Feng Lei Liu 《Chemical science》2020,11(17):4444
The first non-enzymatic redox deracemization method using molecular oxygen as the terminal oxidant has been described. The one-pot deracemization of β,γ-alkynyl α-amino esters consisted of a copper-catalyzed aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation with excellent functional group compatibility. By using benzothiazoline as the reducing reagent, an exclusive chemoselectivity at the C N bond over the C C bond was achieved, allowing for efficient deracemization of a series of α-amino esters bearing diverse α-alkynyl substituent patterns. The origins of chemo- and enantio-selectivities were elucidated by experimental and computational mechanistic investigation. The generality of the strategy is further demonstrated by efficient deracemization of β,γ-alkenyl α-amino esters.A one-pot deracemization of β,γ-alkynyl α-amino esters consisting of an aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation has been described. 相似文献
15.
A. Monge Vega I. Aldana M. M. Rabbani E. Fernandez-Alvarez 《Journal of heterocyclic chemistry》1980,17(1):77-80
This paper describes the synthesis of the previously unknown 11H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]indoles (2) and 11H-tetrazolo[4,5-b]pyridazino[4,5-b]indoles (3) from 4-hydrazino-5H-pyridazino[4,5-b]indoles (1) , as well as the synthesis of 1,2,4-triazolo[3,4-f]-1,2,4-triazino-[4,5-a]indoles (10) from 2-indolecarbohydrazide (4) . Compounds 2 were obtained by acylation of compounds 1 , followed of thermal cyclization and compounds 3 by treating compounds 1 with nitrous acid. The reactions of compound 4 with formic acid or ethyl orthoformiate gave 1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indole (6) . Treating this last compound with phosphorus oxychloride or phosphorus pentasulfide, followed by hydrazine, gave 1-hydrazino-1,2,4-triazino-[4,5-a]indole (9) . Acylation of this last compound, followed of cyclization gave compounds 10 . All the compounds were characterized by elemental analysis and ir and 1H-nmr spectra. 相似文献
16.
Intramolecular vicinal Frustrated Lewis Pairs (FLPs) have played a significant role in the activation of small molecules, and their stabilities and reactivities are found to strongly depend on the nature of the bridging units. This work reports a new carborane based FLP, 1-PPh2-2-BPh2-1,2-C2B10H10 (2), which reacts with an equimolar amount of p-R2NC6H4C CH (R = Me, Et, Ph) at room temperature to give C C triple bond addition products 1,2-[PPh2C(R2NC6H4) CHBPh2]-1,2-C2B10H10 (3) in high yields. Compounds 3 react further with two equiv. of p-R2NC6H4C CH (R = Me, Et) at 60–70 °C to give unprecedented stereoselective tri-insertion products, 3,3a,6,6a-tetrahydronaphtho[1,8a-b]borole tricycles (4), in which one of the aryl rings from arylacetylene moieties has been dearomatized with the formation of four stereocenters including one quaternary carbon center. It is noted that the phosphine unit functions as a catalyst during the reactions. After trapping and structural characterization of a key intermediate, a reaction mechanism is proposed, involving sequential alkyne insertion and 1,2-boryl migration.A carborane based frustrated Lewis pair enables tri-insertion with dearomatization of arylalkynes, forming unprecedented products, borole tricycles, with the construction of four stereocenters including one quaternary carbon center in one process. 相似文献
17.
I. Baranowska 《Monatshefte für Chemie / Chemical Monthly》1987,118(5):659-668
2,2-biquinoxyalyl and thieno[2,3-b:4,5-b]biquinoxyalyl can be photoreduced in acidified alcoholic solutions and in aqueous solutions of acids. Quantum yields of the photochemical reaction have been determined. The fluorescence and phosphorescence spectra of these compounds have been recorded and the fluorescence quantum yields have been determined. A mechanism of the photoreduction has been proposed.
Photochemische Eigenschaften von 2,2-Bichinoxalyl und Thieno[2,3-b:4,5-b]bichinoxalyl
Zusammenfassung 2,2-Bichinoxalyl und Thieno[2,3-b:4,5-b]bichinoxalyl unterliegen photochemischer Reaktion in angesäuerten Alkohollösungen und in wäßrigen Säurelösungen. Es wurde die photochemische Quantenausbeute bestimmt. Außerdem wurden die Fluoreszenz- und Phosphoreszenz-Spektren aufgezeichnet und die Fluoreszenz-Quantenausbeuten bestimmt. Zugleich wurde ein Mechanismus zur Photoreduktion vorgeschlagen.相似文献
18.
Isuri U. Jayasooriya Abolghasem Bakhoda Rachel Palmer Kristi Ng Nour L. Khachemoune Jeffery A. Bertke Timothy H. Warren 《Chemical science》2021,12(47):15733
Commercially available benzophenone imine (HN CPh2) reacts with β-diketiminato copper(ii) tert-butoxide complexes [CuII]–OtBu to form isolable copper(ii) ketimides [CuII]–N CPh2. Structural characterization of the three coordinate copper(ii) ketimide [Me3NN]Cu–N CPh2 reveals a short Cu-Nketimide distance (1.700(2) Å) with a nearly linear Cu–N–C linkage (178.9(2)°). Copper(ii) ketimides [CuII]–N CPh2 readily capture alkyl radicals R˙ (PhCH(˙)Me and Cy˙) to form the corresponding R–N CPh2 products in a process that competes with N–N coupling of copper(ii) ketimides [CuII]–N CPh2 to form the azine Ph2C N–N CPh2. Copper(ii) ketimides [CuII]–N CAr2 serve as intermediates in catalytic sp3 C–H amination of substrates R–H with ketimines HN CAr2 and tBuOOtBu as oxidant to form N-alkyl ketimines R–N CAr2. This protocol enables the use of unactivated sp3 C–H bonds to give R–N CAr2 products easily converted to primary amines R–NH2via simple acidic deprotection.Commercially available benzophenone imine (HN CPh2) reacts with β-diketiminato copper(ii) tert-butoxide complexes [CuII]–OtBu to form isolable copper(ii) ketimides [CuII]–N CPh2 that serve as intermediates in catalytic sp3 C−H amination via radical relay. 相似文献
19.
Mariusz Tasior Pawe Kowalczyk Marta Przyby Magorzata Czichy Patryk Janasik Manon H. E. Bousquet Mieczysaw apkowski Matt Rammo Aleksander Rebane Denis Jacquemin Daniel T. Gryko 《Chemical science》2021,12(48):15935
A two-step route to strongly absorbing and efficiently orange to deep red fluorescent, doubly B/N-doped, ladder-type pyrrolo[3,2-b]pyrroles has been developed. We synthesize and study a series of derivatives of these four-coordinate boron-containing, nominally quadrupolar materials, which mostly exhibit one-photon absorption in the 500–600 nm range with the peak molar extinction coefficients reaching 150 000, and emission in the 520–670 nm range with the fluorescence quantum yields reaching 0.90. Within the family of these ultrastable dyes even small structural changes lead to significant variations of the photophysical properties, in some cases attributed to reversal of energy ordering of alternate-parity excited electronic states. Effective preservation of ground-state inversion symmetry was evidenced by very weak two-photon absorption (2PA) at excitation wavelengths corresponding to the lowest-energy, strongly one-photon allowed purely electronic transition. π-Expanded derivatives and those possessing electron-donating groups showed the most red-shifted absorption- and emission spectra, while displaying remarkably high peak 2PA cross-section (σ2PA) values reaching ∼2400 GM at around 760 nm, corresponding to a two-photon allowed higher-energy excited state. At the same time, derivatives lacking π-expansion were found to have a relatively weak 2PA peak centered at ca. 800–900 nm with the maximum σ2PA ∼50–250 GM. Our findings are augmented by theoretical calculations performed using TD-DFT method, which reproduce the main experimental trends, including the 2PA, in a nearly quantitative manner. Electrochemical studies revealed that the HOMO of the new dyes is located at ca. −5.35 eV making them relatively electron rich in spite of the presence of two B−–N+ dative bonds. These dyes undergo a fully reversible first oxidation, located on the diphenylpyrrolo[3,2-b]pyrrole core, directly to the di(radical cation) stage.Ladder-type heterocycles encompassing two B−–N+ dative bonds possess intense green to red emission, large 2PA cross-sections and superb photostability. 相似文献
20.
Jinsun Lee Xinghui Liu Ashwani Kumar Yosep Hwang Eunji Lee Jianmin Yu Young Dok Kim Hyoyoung Lee 《Chemical science》2021,12(28):9619
Photocatalytic N2 fixation to NH3via defect creation on TiO2 to activate ultra-stable N N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N2 preferentially adsorbs on phase-selective defect sites on TiO2 in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (Ad) preferentially exhibit higher N2 adsorption ability with a reduced energy barrier for a potential-determining-step (*N2 to NNH*) than the disordered rutile (Rd) phase of TiO2. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO2 photocatalyst (Na-Ad/Ro) by sodium-amine treatment of P25-TiO2 under ambient conditions, which exhibits an efficient NH3 formation rate of 432 μmol g−1 h−1, which is superior to that of any other defect-rich disordered TiO2 under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N2 chemisorption on the defect sites of Na-Ad with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with Ro enable substantially enhanced N2 fixation.This work highlights the importance of a rational design for more energetically suitable nitrogen reduction reaction routes and mechanisms by regulating the electronic band structures with phase-selective defect sites. 相似文献