Electron-deficient Cu site catalyzed acetylene hydrochlorination

Rational design of catalytic sites to activate the C≡C bond is of paramount importance to advance acetylene hydrochlorination. Herein, Cu sites with electron-rich and electron-deficient states were constructed by controlling the impregnation solutions. The π electrons flowing from acetylene to Cu site are facilitated over the electron-deficient Cu sites, achieving high activation of C≡C bond. The contradiction between the increased activation of acetylene required for enhanced catalytic activity and the resistance of Cu site to reduction by acetylene required for maintaining catalytic stability can be balanced by establishing strong interactions of Cu site with pyrrolic-N species. The catalytic activity displays a volcano shape scaling relationship as a function of Cu particle size. Tribasic copper chloride is concomitantly generated with the construction of electron-deficient Cu sites. The H–Cl bond of HCl can be activated over the tribasic copper chloride, accelerating the surface reaction of vinyl chloride production. This strategy of inducing electron deficiency provides new insight into the rational design of catalysts for the synthesis of vinyl chloride with a high catalytic performance.

Superior aggregation, morphology and photovoltaic performance enabled by fine tuning of fused electron-deficient units in polymer donors

Copolymerization of an electron-rich donor(D)unit with an electron-deficient acceptor(A)unit to construct efficient D-π-A-πtype donors is an effective strategy for organic solar cell applications.The electron-deficient unit fusion,endows extendedπ-conjugation plane and insures excellent photoelectronic property,has great advantages to build A moiety and gradually receives considerable attention.In this work,we adopt benzo[2,1-b:3,4-b’]dithiophene and benzopyrazine(BP),benzothiadiazole(BT)and benzoselenadiazole(BS)to cleverly construct a series of fused A units with different electrondeficient ability,and further synthesize three polymer donors PBDP-BP,PBDP-BT,and PBDP-BS,respectively.The relationships between structure and performance were systematically investigated.PBDPBT shows a moderate aggregation behavior in both solution and film,and the highest hole mobility among the three polymers.After blending with Y6,the PBDP-BT:Y6-based film has the strongest absorption,favorable compatibility,superior crystallinity,and uniform phase separation morphology compared with PBDP-BP or PBDP-BS based blend films.Thus,the device based on PBDP-BT:Y6 has the highest and balanced charge mobility,suppressive recombination,reduced energy loss and achieves an outstanding PCE of 15.14%,which is superior to PBDP-BP:Y6(8.55%)and PBDP-BS:Y6(6.85%).These results provide learnable guidelines for future fused electron-deficient unit-based donor design for photovoltaic application.

Regulating the Electron-Deficient Component in A-DA1D-A Typed Small-Molecule Acceptors for High-Performance Organic Solar Cells

Fine-tuning of the electron-deficient unit in A-DA1D-A typed small-molecule acceptors (SMAs) plays a crucial role in developing efficient SMAs for organic solar cells (OSCs).Here,we developed a SMA based on benzo[4,5]thieno[2,3-b]quinoxaline,designated as QW1,as well as three SMAs based on 1-methylindoline-2,3-dione,identified as QW2,QW3,and QW4.Compared with QW2,QW1 displays slightly blue-shifted absorption spectra and a lower LUMO energy level due to the stronger electron-withdrawing capability of BTQx in contrast to MDO.On the other hand,the introduction of a bromine atom in QW3 and QW4 causes a blue shift in absorption and a reduction in the LUMO energy level compared to QW2.Density functional theory analysis reveals that QW1 exhibits the best molecular planarity,which endows QW1 with larger electron mobility and tighter molecular stacking.Consequently,PM6:QW1 device affords a better efficiency of 15.63% than those of the devices based on QW2 (14.25%),QW3 (13.21%) and QW4 (15.03%).Moreover,the QW4-based device yields the highest open-circuit voltage of 0.933 V,and the PM6:L8-BO:QW4 ternary device realizes a PCE of 19.03%.Overall,our work demonstrates that regulation of electron-deficient central units is an effective strategy to improve the photovoltaic performance of the resulting A-DA1D-A SMAs.

On-Surface Synthesis of Electron-Deficient Bisanthene Tetraimide

Imide-based conjugated molecules have emerged as a highly promising class of building blocks for constructing n-type semiconducting materials with lowlying lowest unoccupied molecular orbitals and exceptional stability.Although imides,such as naphthalene diimides,perylene diimides and their lateral fused analogs,have been synthesized extensively,the design and synthesis of largerπ-extended molecules incorporating more than two imide groups are desirable but still very challenging.Herein,we report the synthesis of an unprecedented electron-deficient bisanthene tetraimide(ATI)containing a bisantheneconjugated core and four five-membered imide groups,which was successfully achieved via a combined approach of solution and on-surface synthesis.The chemical structures,electronic states,formation mechanism and aromaticity of ATI were systematically investigated by scanning tunneling microscopy,noncontact atomic force microscopy,scanning tunneling spectroscopy,and density functional theory calculations.

An asymmetric non-fused electron-deficient building block for low-cost polymer acceptor in all-polymer solar cells

The development of polymerized fused-ring small molecule acceptors(FRA-PAs) has boosted the performance of all-polymer solar cells(all-PSCs).However,these FRA-PAs suffer from lengthy synthesis steps and high production costs due to the high degree of synthetic complexity for fused-ring small molecule acceptors(FRAs).Furthermore,most FRA-PAs exhibit strong batch-to-batch variation,limiting further industrial applications.Herein,we designed and synthesized asymmetric non-fused electron-deficient building block TIC-Br with a simple structure(only three synthetic steps),showing a planar configuration,excellent electron affinity,and large dipole moment.A simple polymer acceptor PTIB was further developed by polymerization of TIC-Br and sensitized fluorinated-thienyl benzodithiophene(BDT-TF-Sn).PTIB exhibits a broad absorption from 300 to 800 nm,a suitable lowest unoccupied molecular orbital(LUMO) energy level of-3.86 e V,and moderate electron mobility(1.02×10^(-4)cm^(2)V^(-1)s^(-1)).When matched with PM6,the device achieved the best PCE of 10.11%with a high V_(OC) of 0.97 V,which is one of the highest among those reported all-PSCs.More importantly,PTIB exhibits a lower synthetic complexity index(SC=35.0%)and higher figure-of-merit values(FOM=29.0%) than all the reported high-performance PAs.The polymer also exhibits excellent batch-to-batch reproducibility and great potential for scale-up fabrication.This study indicates that TIC-Br is a promising building block for constructing low-cost polymer acceptors for large-scale applications in all-PSCs.

Asymmetric Dearomatization of Electron-Deficient Heteroarenes by a Phosphine-Catalyzed[3+2]Annulation with Vinylcyclopropanes

Asymmetric dearomatization reactions of various electron-deficient heteroarenes,including benzofurans,benzothiophenes,and indoles,have been described.Through a phosphine-catalyzed[3+2]annulation with vinylcyclopropanes,readily available heteroarene feedstocks undergo smooth dearomatization reactions,delivering a diverse array of valuable chiral cyclopentabenzodihydrofuran and cyclopentaindoline scaffolds in a highly diastero-and enantioselective manner.Notably,the employment of cyclopropanes in phosphine-mediated annulation for the dearomatization of electron-deficient arenes is unknown.

Electron-deficient core fused-ring based non-fullerene acceptor enables over 15% efficiency in single junction organic solar cells

Organic solar cells(OSCs)are promising to access flexible,light weight and semi-transparent photovoltaic devices by low-cost solution fabrication.Recently,the fused-ring nonfullerene acceptors play an important role in promoting the research progress of the OSCs.The power conversion efficiencies(PCEs)have been rapidly boosted to over 14%in single junction OSCs with the development of new nonfullerene acceptors and the related devices[1-3].Although the PCEs of OSCs are still inferior to their inorganic counterparts,further improvement of the PCEs could be expected by the development of new photovoltaic materials.

Novel Efficient Light-Emitting Polyfluorene Derivatives Modified by Electron-Deficient Moieties with Nonlinear Structure

Two novel fluorene-based copolymers (PFSD and PFMD) containing squaric acid or maleimide unit in the main chain were synthesized in good yields by Suzuki coupling reaction. The resulting polymers possess excellent thermal stability, high electron affinity and high photoluminescence (PL) quantum yields. They can fluoresce in yellow-light range due to either the charge transfer between a fluorene segment and an electron-deficient containing squaric acid/maleimide segment of the polymers or the Forster energy transfer between different polymer chains. The results from PL measurements of the isothermally heated polymer thin films show that the commonly observed aggregate excimer formation in polyfluorenes is very effectively suppressed in these two polymers due to the nonlinear structures of maleimide and squaric acid moieties. Double-layer polymer light-emitting diodes (PLED) were fabricated using the resulting polymers as the emitting layers and Ba or Mg : Ag (V : V= 10 : 1) as cathodes. All the devices show bright yellow emission (562-579 nm) with different maximum external quantum efficiencies (0.006%-1.13%). Compared with the other devices, indium-tin oxide (ITO)/polyethylenedioxythiophene (PEDOT) : polystyrene sulfonic acid (PSS)PFMD/Mg : Ag has the higher maximum external quantum efficiency of 1.13% at 564 cd/m2 with a bias of 8.4 V.

Theory-guided construction of electron-deficient sites via removal of lattice oxygen for the boosted electrocatalytic synthesis of ammonia

Rational design of catalytic sites to activate the inert N≡N bond is of paramount importance to advance N2 electroreduction. Here, guided by the theoretical predictions, we construct a NiFe layered double hydroxide (NiFe-LDH) nanosheet catalyst with a high density of electron-deficient sites, which were achieved by introducing oxygen vacancies in NiFe-LDH. Density functional theory calculations indicate that the electron-deficient sites show a much lower energy barrier (0.76 eV) for the potential determining step compared with that of the pristine NiFe-LDH (2.02 eV). Benefiting from this, the NiFe-LDH with oxygen vacancies exhibits the greatly improved electrocatalytic activity, presenting a high NH3 yield rate of 19.44 µg·h−1·mgcat−1, Faradaic efficiency of 19.41% at −0.20 V vs. reversible hydrogen electrode (RHE) in 0.1 M KOH electrolyte, as well as the outstanding stability. The present work not only provides an active electrocatalyst toward N2 reduction but also offers a facile strategy to boost the N2 reduction.

BF_3·Et_2O promoted conjugate addition of ethanethiol to electron-deficient alkynes

An effective method for the synthesis of vinyl thioethers through the conjugate addition of ethanethiol to electron-deficient alkynes promoted by BF3.Et20 has been developed. Electron-deficient internal alkynes react with ethanethiol in this system to yield mainly Z-isomer of vinyl thioether adducts, while electron-deficient terminal alkynes afford mainly E-isomer of vinyl thioether adducts.

Selective annulation of benzamides with internal alkynes catalyzed by an electron-deficient rhodium catalyst

An electron-deficient[CpERhCl2]2 catalyzed annulation of N-pentafluorophenylbenzamides with internal alkynes was successfully established under mild reaction conditions,with the assistance of Lewis acid silver salt.Particularly,electron-deficient benzamide substrates were smoothly transformed into the desired products in this catalytic system.The catalytic system showed a broad tolerance for different substituents on the aromatic rings or aryl,alkyl-substituted alkynes.

Molecular diversity of triphenylphosphine promoted reaction of electron-deficient alkynes and arylidene Meldrum acid(N,N’-dimethylbarbituric acid)

The three-component reaction of triphenylphosphine,dimethyl hex-2-en-4-ynedioate and arylidene N,N’-dimethylbarbituric acids in dry methylene dichloride at room temperature afforded trans-1,3-disubstituted 7,9-diazaspiro[4.5]dec-1-enes in good yields and with high diastereoselectivity.However,the similar three-component reaction with arylidene Meldrum acids resulted in a mixtures of cis/trans-1,2-disubstituted 7,9-dioxaspiro[4.5]dec-1-enes.Additionally,the three-component reaction of triphenylphosphine,dimethyl but-2-ynedioate and arylidene Meldrum acids gave polysubstituted 5-(triphe nyl-λ~5-phosphanylidene)cyclopenta-1,3-die nes.A plausible reaction mechanism was proposed for the formation of various products with different regioselectivity and diastereoselectivity.

Electron-deficient core fused-ring based non-fullerene acceptor enables over 15% efficiency in single junction organic solar cells

With the support from the National Natural Science Foundation of China and National Key Research&Development Project of China,the research team led by Prof.Zou YingPing(邹应萍)at the College of Chemistry and Chemical Engineering,Central South University,reported a new nonfullerene acceptor Y6 with a fused-ring structure containing electron-deficient bcnzothiadiazole core.

A new chlorinated non-fullerene acceptor based organic photovoltaic cells over 12%efficiency

The method to fluorinate the terminal group has achieved remarkable success and been widely used to fine-tune the intrinsic properties of organic acceptor materials.Referring to chlorination,however,it gets less attention and remains ambiguous effect on organic photovoltaic(OPV)cells.Herein,a new non-fullerene acceptor named Y19 was reported with benzotriazole as the electron-deficient core and 2Cl-ICs as the strong electron-withdrawing end groups.Y19 exhibits a wide film absorption band from 600 nm to 948 nm and low LUMO(the lowest unoccupied molecular orbital)energy level of−3.95 eV.Photovoltaic devices based on PM6:Y19 show high-power conversion efficiency(PCE)of 12.76%with high open-circuit voltage(Voc)of 0.84 V,short-circuit current density(Jsc)of 22.38 mA/cm2 and fill factor(FF)of 68.18%.Broad external quantum efficiency(EQE)response of over 60%in the range of 480−860 nm can be obtained.This study demonstrates that chlorination,as a low-cost molecular design strategy,has its own superiorities to improve device performance and promote the potential application in OPV.

A new class of crystalline X-ray induced photochromic materials assembled from anion-directed folding of a flexible cation

Electron-deficient viologens are widely used as ligands or structure-directing agents(SDAs)to synthesize crystalline X-ray induced photochromic materials.Here,a new rational strategy of anion-directed fold-ing a flexible cation(H_(2)imb)^(2+)((H_(2)imb)^(2+)=di-protonated 2,3-bis(imidazolin-2-yl)-2,3-dimethylbutane)has been developed.Electron-donating Cl−and(ZnCl4)2−are used to direct folding a flexible electron-deficient(H_(2)imb)^(2+)cation.Three complexes(H_(2)imb)(NO_(3))2(1),(H_(2)imb)Cl2·H_(2)O(2),and(H_(2)imb)ZnCl4(3)have been synthesized in which(H_(2)imb)^(2+)crystallize in an anti-conformation,88.8°-gauche,and 51.8°-gauche,respectively.In contrary to X-ray silent complex 1,X-ray induced photochromism has been achieved in both complex 2 and 3.An intermolecular charge-transfer mechanism has been elucidated and the anion directed folding of(H_(2)imb)^(2+)has been validated to be critical to yield colored long-lived charge-separated states.

Palladium Complexes with N,O-Bidentate Ligands Based on N-Oxide Units from Cyclic Secondary Amines:Synthesis and Catalytic Application in Mizoroki-Heck Reaction

Palladium-catalyzed Mizoroki-Heck reaction is a powerful and efficient method for construction of Csp2–Csp2 bonds.Herein,four palladium complexes(I—IV)with N,O-bidentate ligands(L1—L4)based on N-oxide units from cyclic secondary amines were easily synthesized and successfully applied in Mizoroki-Heck reaction of aryl bromides with electron-deficient olefins.X-ray diffraction analyses indicated the palladium(II)atom of II took the distorted square planar geometry and was four-coordinated by nitrogen and oxygen atoms from two ligands(L2).Two free chloride ions were presented as counter anions in complex II.But the palladium(II)center of IV was coordinated by nitrogen and oxygen atoms from one ligand(L4)as well as two chlorine atoms,which exhibited the nearly square-planar geometry.The study on catalytic properties of palladium complexes revealed that complex II exhibited high activity superior to the other complexes.The coupling reactions of a series of aryl bromides and olefin derivatives proceeded in the presence of 2—5 mol%palladium complex II,giving the desired products in good to excellent yields.The advantages of this method such as good compatibility of functional groups,high yields,and short reaction times made it more attractive for constructing Csp2–Csp2 bonds in the synthesis of functional molecules and materials.

A-DA′D-A non-fullerene acceptors for high-performance organic solar cells

Since the world-record power conversion efficiency of 15.7%was achieved for organic solar cells(OSCs)in 2019,the newly developed non-fullerene acceptor(NFA)Y6 with an A-DA′D-A structure(A denotes an electron-accepting moiety,D denotes an electron-donating moiety)has attracted increasing attention.Subsequently,many new A-DA′D-A NFAs have been designed and synthesized,and the A-DA′D-A NFAs have played a significant role in the development of high-performance non-fullerene organic solar cells(NF-OSCs).Compared with the classical A-D-A-type acceptors,A-DA′D-A NFAs contain an electrondeficient core(such as benzothiadiazole(BT),benzotriazole(BTA),quinoxaline(Qx),or their derivatives)in the ladder-type fused rings to fine-tune the energy levels,broaden light absorption and achieve higher electron mobility of the NFAs.This review emphasizes the recent progress on these emerging A-DA′D-A(including Y-series)NFAs.The synthetic methods of DA′D-fused rings are introduced.The relationships between the chemical structure of the A-DA′D-A NFAs and the photovoltaic performance of the corresponding OSCs are summarized and discussed.Finally,issues and prospects for further improving photovoltaic performance of the OSCs are also proposed.

From Perylene Dimide Polymers to Fused-Ring Electron Acceptors:A 15-Year Exploration Journey of Nonfullerene Acceptors

Fullerene derivatives are classic electron acceptor materials for organic solar cells (Oscs) but possess some intrinsic drawbacks such as weak visiblelightabsorption,limitedoptoelectronic property tunability,dificult purification and photochemical/morphological instability.Fullereneacceptors area bottleneck restricting further development of this field. Ourgroup pioneered the exploration of novel nonfulerene acceptors in China in 2006,andinitiated the research of two representative acceptor systems, rylene dimide polymer and fused-ring electron acceptor (FREA).FREA breaks the theoreticalefficiencylimit of fullerene-based OsCs (-13%) and promotes the whole field to an unprecedented prosperity with efficiency of 20%, heraldinga nonfullerene era for OsCs.In this review, we revisit 15-year nonfullerene exploration journey,summarize the design principles,molecular engineeringstrategies, physical mechanisms and device applications of these two nonfullerene acceptor systems, and propose some possible researchtopics in the nearfuture.

Organocatalytic Enantioselective[8+4]Cycloadditions of Iso-benzofulvenes for the Construction of Bicyclo[4.2.1]nonanes

The[8+4]cycloaddition of indene-2-carbaldehydes with indole-2,3-quinodimethanes and pyrrolidone-3,4-dienes is described,affording indole and pyrrolidone annulated bicyclo[4.2.1]nonanes in a highly peri-,diastereo-,and enantioselective fashion in the presence of a secondary amine catalyst.This reaction,which proceeds through catalytically generated isobenzofulvenes,represents the first asymmetric version of high-order[8+4]cycloaddition.

Elaboration of phosphoramidite ligands enabling palladium-catalyzed diastereo-and enantioselective all carbon [4+3]cycloaddition

A palladium-catalyzed diastereo-and enantioselective all carbon [4+3] cycloaddition of trimethylenemethane was developed by employing the elaborate tetrahydroquinoline-derived phosphoramidite ligand. The exclusive regioselectivity was realized by using the aromatization-driven diene indole-2,3-quinodimethanes, affording biologically important cyclohepta[b]indoles with excellent diastereo-, and enantioselectivities(up to >20:1 dr, >99% ee). Furthermore, the more challenging pyrrolidone-3,4-dienes, in the absence of aromatization force, were also compatible inthereaction, providing novel cyclohepta[c]pyrrol-1(2H)-ones with excellent regio-, diastereo-, and enantioselectivities(up to >20:1 rr, >20:1 dr, >99% ee).