Reveal the growth mechanism in perovskite films via weakly coordinating solvent annealing

In this study, we investigated the nucleation mechanism of perovskite films by employing isopropanol(IPA), a weakly coordinating solvent, to anneal both PbI2 and CH3 NH3 PbI3 in the sequential deposition and CsPbI3 in the one-step deposition. IPA solvent annealing(IPA SA) of PbI2 films was carried out at different temperatures. The grain size,compactness, roughness and morphology of PbI2 and CH3 NH3 PbI3 films were seriously affected by annealing methods. Similarly, weakly coordinating solvent annealing process was also employed to anneal all inorganic CsPbI3 perovskite in a one-step method. A continuous and dense CsPbI3 film with uniform grain size was obtained. We recognized that weakly coordinating solvent annealing for perovskite could regulate the dissolution-recrystallization process via controlling the volume of residual solvent in perovskite intermediate films. The power conversion efficiency(PCE) of conventional CH3 NH3 PbI3 perovskite solar cells(PSCs)reached 17.4% and that of CsPbI3 PSCs reached 2.5% based on this sequential IPA SA process.

Weakly coordinating group directed rhodium-catalyzed unconventional site-selective C-H olefination of indolizines at the 8-position

A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additive under similar reaction conditions.Weakly coordinating groups,such as ketone,alde hyde,amide and ester,were used as directing groups.The ester group can be removed under acid conditions and therefore is used as a traceless directing group.

Facile and secure synthesis of porous partially fluorinated graphene employing weakly coordinating anion for enhanced high-performance symmetric supercapacitor

In this paper,porous partially fluorinated graphene(PFG)for supercapacitors(SCs)was fabricated by a mild and secure one-pot hydrothermal method utilizing weakly coordinating anion BF_(4)^(-) as the fluorine source.The hydrolysis rate of sodium fluoroborate was adjusted by controlling the reaction temperature and PFG containing semi-ionic C-F bonds was obtained,where the content of semi-ionic C-F bonds in PFG can be easily regulated.The final experimental results show that the incorporation of fluorine not only modulates the electrochemical properties of the material,but also creates abundant pores.When assembled in a symmetric supercapacitor,the PFG shows a high specific capacitance of 269.7 F g^(-1) at 1 A g^(-1) and a superior rate capability with 89.3%capacitance retained,as the current density is increased from 1 A g^(-1)even to 20 A g^(-1).Furthermore,the resultant energy density for PFG is 9.4 Wh kg^(-1) at a power density of 250.0 W kg^(-1)(1 A g^(-1)).All these results confirm that as-prepared partially fluorinated graphene is appropriate for the application in SCs and mass production.

Writing and Erasing Encryption Information Based on Frustrated Lewis Pair Chemistry

Lewis acid−base adducts resulting from instantaneous interactions provide a cost-effective strategy for color tuning and anticounterfeiting information.Herein,we report the construction of luminescent Lewis acid−base adducts via inkjet printing.Due to the unique weak coordination bond of B→N,it is feasible to construct anticounterfeiting information that is easy to erase.The in situ postsynthesis of the luminescent quick response codes via inkjet printing facilitates precision chemistry control to change the emission ranging from deep-blue(peaking at 407 nm)to orange-red(peaking at 597 nm).The encrypted information can be quickly erased either by modulating the temperature to dissociate the weak coordination or strong Lewis base to promote a neutralization reaction.

Some recent advances in transition-metal-catalyzed ortho SP^2 C–H functionalization using Ru, Rh, and Pd

In the past decade,transition-metal-catalyzed C–H functionalization by weak coordination has emerged as a practical and powerful tool to access many valuable chemicals.Two classes of weakly coordinating directing groups,commonly occurring functional groups,and easily removable auxiliaries,have been found to be efficient and practical for C–H activation reactions.This mini-review contains examples of recent research advances on transition-metal-catalyzed SP2 C–H functionalization via weak coordination,using Ru,Rh,and Pd.A number of weakly coordinating functional groups(e.g.,ketone,ester,carbamate,tertiary amide,ether,thioether,alcohol,and some others)are covered.As the field of transition-metal-catalyzed C–H functionalization continues to develop and more synthetically useful chemo-,regio-,and enantioselective reactions catalyzed by transition metal via weak coordination are discovered,this promising and attractive strategy will play a more important role in modern organic synthesis.

Pd-catalyzed ortho-olefination of aromatic acetyl esters

A Pd（Ⅱ）-catalyzed ortho-olefination of aromatic acetic esters is described which features with an excellent funcitional group tolerance, good yields, mild reaction conditions, good scalability as well as high chemo-and regio-selectivity.

Isolable Radical Ions of Main-Group Elements： Structures, Bonding and Properties

Synthesis of stable main-group element-based radicals represents one of the most interesting topics in contemporary organometallic chem- istry, because of their vital roles in organic, inorganic and biological chemistry as well as materials science. However, the access of stable main-group element-based radicals is highly challenging owing to the lack of energetically accessible orbitals in the main-group elements. During the last decades, several synthetic strategies have been developed in obtaining these reactive species. Among them, utilizing the stericaliy demanding substituents and x-conjugated ligands has proven to be an effective approach. Weakly coordinating ions （WCAs） have also been found to be exceptionally practical in synthesizing radical cations of main-group elements. By introducing these stabilization methods, we have successfully prepared a variety of radical ions of p-block elements in the crystalline forms, and investigated their properties by different experimental and quantum chemical calculation methods. According to the investigations, magnetic stability was observed, resulting from the intramolecular electron-exchange interaction. Furthermore, we also found that the singlet-triptet energy gaps of the bis（triarylamine） diradical dications can be tunable by varying the temperature. These investigations open new avenues of the main-group element-based radicals for a large variety of applications.