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1.
Artigo em Inglês | MEDLINE | ID: mdl-34846087

RESUMO

A new class of axially chiral styrene-based thiourea-tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements and multiple activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo-, diastereo- and enantioselective (2+4) cyclization of 2-benzothiazolimines with homophthalic anhydrides in good yields (up to 96%) with excellent stereoselectivities (all >95:5 dr, up to 98% ee). More importantly, theoretical calculations elucidated the important role of axially chiral styrene moiety in controlling both the reactivity and the enantioselectivity. This work not only represents the first design of styrene-based chiral thiourea-tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2-benzothiazolimines, but also gives an in-depth understanding of axially chiral styrene-based organocatalysts.

2.
Molecules ; 26(21)2021 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-34771158

RESUMO

Catalytic asymmetric [2 + 4] cycloadditions of 3-vinylindoles with ortho-quinone methides and their precursors were carried out in the presence of chiral phosphoric acid to afford a series of indole-containing chroman derivatives with structural diversity in overall high yields (up to 98%), good diastereoselectivities (up to 93:7 dr) and moderate to excellent enantioselectivities (up to 98% ee). This approach not only enriches the chemistry of catalytic asymmetric cycloadditions involving 3-vinylindoles but is also useful for synthesizing chiral chroman derivatives.

3.
Inorg Chem ; 59(1): 523-532, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31809032

RESUMO

Synthesis of the multidentate coordinated chelate N3C-H2, composed of a linked functional pyridyl pyrazole fragment plus a peripheral phenyl and pyridyl unit, was obtained using a multistep protocol. Preparation of Ir(III) metal complexes bearing a N3C chelate in the tridentate (κ3), tetradentate (κ4), and pentadentate (κ5) modes was executed en route from two nonemissive dimer intermediates [Ir(κ3-N3CH)Cl2]2 (1) and [Ir(κ4-N3C)Cl]2 (2). Next, a series of mononuclear Ir(III) complexes with the formulas [Ir(κ4-N3C)Cl(py)] (3), [Ir(κ4-N3C)Cl(dmap)] (4), [Ir(κ4-N3C)Cl(mpzH)] (5), and [Ir(κ4-N3C)Cl(dmpzH)] (6), as well as diiridium complexes [Ir2(κ5-N3C)(mpz)2(CO)(H)2] (7) and [Ir2(κ5-N3C)(dmpz)2(CO)(H)2] (8), were obtained upon treatment of dimer 2 with pyridine (py), 4-dimethylaminopyridine (dmap), 4-methylpyrazole (mpzH), and 3,5-dimethylpyrazole (dmpzH), respectively. These Ir(III) metal complexes were identified using spectroscopic methods and by X-ray crystallographic analysis of representative derivatives 3, 5, and 7. Their photophysical and electrochemical properties were investigated and confirmed by the theoretical simulations. Notably, green-emitting organic light-emitting diode (OLED) on the basis of Ir(III) complex 7 gives a maximum external quantum efficiency up to 25.1%. This result sheds light on the enormous potential of this tetradentate coordinated chelate in the development of highly efficient iridium complexes for OLED applications.

4.
Chem Commun (Camb) ; 55(95): 14383-14386, 2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31723947

RESUMO

An AgI-promoted regioselective [4+2] annulation reaction of indoles with alkenes has been established. During the transformation, N-centered radicals are generated by the oxidation of the N-H bond of N-alkoxyamides. Control experiments and DFT calculations reveal a plausible mechanism. This synergistic process achieves the direct construction of new C-C and C-N bonds under relatively mild conditions with broad substrate scope, high atom economy, and easy-to-handle nature.

5.
J Org Chem ; 84(15): 9454-9459, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31283220

RESUMO

The progressively improved heterobimetallic antimony transition metal complex PSbP-Pt (I1) provides superior activity in catalyzed 1,6-enyne cycloisomerization. Our DFT calculations demonstrate that the noninnocent character of the antimony ligand enhances the self-activation of the catalyst precursor through a substrate-aided intramolecular chloride migration, which triggers subsequent reaction. Designed alternative redox noninnocent active species with strong electron-withdrawing groups also show promising catalytic ability due to an electron-deficient antimony ligand, which lowers the typical reaction barrier for the cycloisomerization of 1,6-enyne.

6.
Org Lett ; 21(3): 700-704, 2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30675791

RESUMO

A new strategy was developed for the efficient synthesis of di-, tetra-, and hexa-substituted 1,3-butadienes. This one-pot procedure involves lithium-iodine exchange to generate the corresponding vinyllithium intermediates. A subsequent iron-catalyzed ligand-free oxidative homo-coupling eventually led to the formation of 1,3-butadienes in acceptable to excellent isolated yields.

7.
Chem Commun (Camb) ; 54(36): 4541-4544, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29662982

RESUMO

A novel host material featuring a spiro-annulated benzimidazole configuration is exploited for blue phosphorescent organic light-emitting devices (PhOLEDs). The new material exhibits a high triplet energy (3.07 eV) and a bipolar characteristic and is effective as the host for FIrpic-, FIr6- and FK306-based blue PhOLEDs with high performances.

8.
Chem Commun (Camb) ; 54(9): 1113-1116, 2018 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-29333555

RESUMO

Density functional theory (DFT) calculations show that H2 evolution is attributed to active sulfur hydrides derived from MoS2 complexes via two- or three-electron reduction from the synthesized [(PY5Me2)MoS2]2+. Water acts as a bridge for H2 evolution from the intermolecular H+/H- coupling between sulfur hydride complexes and hydrated protons.

9.
ACS Appl Mater Interfaces ; 9(8): 7331-7338, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28185447

RESUMO

Organic materials containing arylamines have been widely used as hole-transporting materials as well as emitters in organic light-emitting devices (OLEDs). However, it has been pointed out that the C-N bonds in these arylamines can easily suffer from degradation in excited states, especially in deep-blue OLEDs. In this work, phenanthro[9,10-d]imidazole (PI) is proposed as a potential donor with higher stability than those of arylamines. Using PI as the donor, a donor-acceptor type deep-blue fluorophore 1-phenyl-2-(4″-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1':4',1″-terphenyl]-4-yl)-1H-phenanthro[9,10-d]imidazole (BITPI) is designed and synthesized. Results from UV-aging test on neat films of BITPI and other three arylamine compounds demonstrate that PI is indeed a more stable donor comparing to common arylamines. An OLED using BITPI as an emitter exhibits good device performances (EQE over 7%) with stable deep-blue emission (color index: (0.15, 0.13)) and longer operation lifetime than the similarly structured device using arylamine-based emitter. Single-organic layer device based on BITPI also shows superior performances, which are comparable to the best results from the arylamine-based donor-acceptor emitters, suggesting that PI is a stable donor with good hole transport/injection capability.

10.
Chem Sci ; 8(5): 3599-3608, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30155205

RESUMO

In this work, we revealed a new approach for the development of efficient violet-blue emitting materials featuring a hybrid local and charge transfer (HLCT) excited state through the incorporation of naphthyl group(s) as a weak n-type π spacer in a donor-π-acceptor (D-π-A) system. The resulting materials (TPINCz and TPIBNCz) show improved intramolecular charge transfer properties and highly efficient violet-blue fluorescence. It is demonstrated that the pattern of the π spacers has significant influence on the photophysical properties. The incorporation of a naphthyl/binaphthyl spacer between the donor and acceptor moieties can alleviate the common dilemma that enhancing device performance by increasing the charge transfer excited properties often leads to red-shifted emissions. A device using TPINCz as an emissive dopant shows a violet-blue emission with CIE coordinates of (0.153, 0.059) and a record high EQE of 6.56 ± 0.11% at a brightness of 1000 cd m-2. To the best of our knowledge, this performance is the highest among the reported devices with CIE y ≤0.08. Our study provides a new pathway for the design of high-performance violet-blue emitters with a D-π-A architecture in organic electroluminescence applications.

11.
Chem Asian J ; 11(18): 2528-36, 2016 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-27500596

RESUMO

The reactivity difference between the hydrogenation of CO2 catalyzed by various ruthenium bidentate phosphine complexes was explored by DFT. In addition to the ligand dmpe (Me2 PCH2 CH2 PMe2 ), which was studied experimentally previously, a more bulky diphosphine ligand, dmpp (Me2 PCH2 CH2 CH2 PMe2 ), together with a more electron-withdrawing diphosphine ligand, PN(Me) P (Me2 PCH2 N(Me) CH2 PMe2 ), have been studied theoretically to analyze the steric and electronic effects on these catalyzed reactions. Results show that all of the most favorable pathways for the hydrogenation of CO2 catalyzed by bidentate phosphine ruthenium dihydride complexes undergo three major steps: cis-trans isomerization of ruthenium dihydride complex, CO2 insertion into the Ru-H bond, and H2 insertion into the ruthenium formate ion. Of these steps, CO2 insertion into the Ru-H bond has the lowest barrier compared with the other two steps in each preferred pathway. For the hydrogenation of CO2 catalyzed by ruthenium complexes of dmpe and dmpp, cis-trans isomerization of ruthenium dihydride complex has a similar barrier to that of H2 insertion into the ruthenium formate ion. However, in the reaction catalyzed by the PN(Me) PRu complex, cis-trans isomerization of the ruthenium dihydride complex has a lower barrier than H2 insertion into the ruthenium formate ion. These results suggest that the steric effect caused by the change of the outer sphere of the diphosphine ligand on the reaction is not clear, although the electronic effect is significant to cis-trans isomerization and H2 insertion. This finding refreshes understanding of the mechanism and provides necessary insights for ligand design in transition-metal-catalyzed CO2 transformation.

12.
Angew Chem Int Ed Engl ; 55(21): 6295-9, 2016 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-27061132

RESUMO

An enantioselective rhodium(I)-catalyzed cycloisomerization reaction of challenging (E)-1,6-enynes is reported. This novel process enables (E)-1,6-enynes with a wide range of functionalities, including nitrogen-, oxygen-, and carbon-tethered (E)-1,6-enynes, to undergo cycloisomerization with excellent enantioselectivity, in a high-yielding and operationally simple manner. Moreover, this Rh(I) -diphosphane catalytic system also exhibited superior reactivity and enantioselectivity for (Z)-1,6-enynes. A rationale for the striking reactivity difference between (E)- and (Z)-1,6-enynes using Rh(I) -BINAP and Rh(I) -TangPhos is outlined using DFT studies to provide the necessary insight for the design of new catalyst systems and the application to synthesis.

13.
Phys Chem Chem Phys ; 18(6): 4860-70, 2016 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-26804824

RESUMO

Improving the catalytic efficiency of CO2 hydrogenation is a big challenge in catalysed CO2 recycling and H2 conservation. The detailed mechanism of [Rh(PCH2X(R)CH2P)2](+) (X(R) = CH2, N-CH3, CF2) catalyzed CO2 hydrogenation is studied to obtain insights into the electronic effect of the substituents at diphosphine ligand on the catalytic efficiency. The most favorable reaction mechanism is found to be composed of three steps: (1) oxidative addition of dihydrogen onto the Rh center of the catalyst; (2) the first hydride abstraction by base from the Rh dihydride complexes; (3) the second hydride transfer from the Rh hydride complexes to CO2. It was found that the transition state for the first hydride abstraction from the Rh dihydride complex is the TOF-determining transition state (TDTS) in the most favorable mechanism. The energetic span (δE) of the cycle is suggested related to the thermodynamic hydricity of the Rh dihydride complex. Model catalyst [Rh(PCH2CF2CH2P)2](+) with a strong σ electron withdrawing group on the diphosphine ligand provides higher hydricity in the Rh dihydride complex and lower activation energy when compared with the other two catalysts. Our study shows that it is the σ electron withdrawing ability rather than the electron donating ability that enhances the catalytic efficiency in catalyzed CO2 hydrogenation. This finding will benefit ligand design in transition metal catalysts and lead to more efficient methods for CO2 transformation.

14.
Inorg Chem ; 53(18): 9692-702, 2014 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-25184506

RESUMO

Platinum bis(dithiolene) complexes have reactivity toward alkenes like nickel bis(dithiolene) complexes. We examined the uptake of 1,3-butadiene by platinum bis(dithiolene) [Pt(tfd)2] (tfd = S2C2(CF3)2) via a density functional theory study; both 1,2- and 1,4-additions of 1,3-butadiene to the ligands of Pt(tfd)2 to form both interligand and intraligand adducts were studied. For single 1,3-butadiene addition, direct 1,4-addition on interligand S-S, 1,2-addition on intraligand S-S, and 1,4-addition on intraligand S-C are all feasible at room temperature and are controlled by the symmetry of the highest occupied molecular orbital of 1,3-butadiene and the lowest unoccupied molecular orbital of Pt(tfd)2. However, the formation of the interligand S-S adduct through 1,4-addition of one molecule of cis-1,3-butadiene is the most favorable route, with a reaction barrier of 9.3 kcal/mol. The other two addition processes cannot compete with this one due to both higher reaction barriers and unstable adducts. Other possible pathways, such as formation of cis-interligand S-S adduct from 1,2-addition of one molecule of 1,3-butadiene via a twisted trans-interligand S-S adduct, have higher barriers. Our calculated results show that 1,4-addition of a single molecule of 1,3-butadiene on the interligand S-S gives the kinetically stable product by a one-step pathway. But of at least equal importance is the apofacial 1,4-addition of two molecules of 1,3-butadiene on the intraligand S-C of the same ligand on Pt(tfd)2, which yields the thermodynamically stable product, obtained via a short lifetime intermediate, the 1:1 intraligand S-C adduct, being formed through several pathways. The calculated results in this study well explain the experimental observation that 1:1 interligand S-S adduct was formed in a short time, and the intraligand S-C adduct from two molecules of cis-1,3-butadiene was accumulated in 20 h at 50° and characterized by X-ray crystallography.

15.
J Phys Chem A ; 116(47): 11656-67, 2012 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-23126300

RESUMO

The detailed potential energy surfaces (PESs) of poorly understood ion-molecule reactions of CH(3)O(-) with O(2)(X(3)Σ(g)(-)) and O(2)(a(1)Δ(g)) are accounted for by the density functional theory and ab initio of QCISD and CCSD(T) (single-point) theoretical levels with 6-311++G(d,p) and 6-311++G(3df,2pd) basis sets for the first time. For the reaction of CH(3)O(-) with O(2)(X(3)Σ(g)(-)) ((3)R), it is shown that a hydrogen-bonded complex (3)1 is initially formed on the triplet PES, which is 1.8 kcal/mol above reactants (3)R at the CCSD(T)//QCISD level, from which all the products P(1)-P(8) can be generated. As to the reaction of CH(3)O(-) with O(2)(a(1)Δ(g)) ((1)R), it is found that the two energetically low-lying complexes of (1)1(-31.5 kcal/mol) and (1)2(-24.1 kcal/mol) are initiated on the singlet PES. Starting from them, a total of seven products may be possible, that is, besides P(1), P(2), P(3), P(4), and P(8), which are the same as on the triplet PES, there exist also another two products, P(9) and P(10). For both reactions, taking the thermodynamics and kinetics into consideration, the hydride-transfer species P(1)(CH(2)O + HO(2)(-)) should be the most favorable product followed by P(8)(e + CH(2)O + HO(2)), which is a secondary product of electron-detachment from P(1), and the generation of endothermic P(7)(17.7 kcal/mol) for the reaction of CH(3)O(-) with O(2)(X(3)Σ(g)(-)) is also possible at high temperature, whereas the remaining products are negligible. The measured branching ratio of products for CH(3)O(-) with O(2)(X(3)Σ(g)(-)) by Midey et al. is 0.85:0.15 for P(1) and P(8), and that of CH(3)O(-) with O(2)(a(1)Δ(g)) is 0.52:0.48 with more P(8), which can be rationalized by our theoretical results that P(8) on the triplet PES is 4.9 kcal/mol above (3)R, whereas both P(1) and P(8) on the singlet PES are very low-lying at 45.6 and 25.2 kcal/mol below (1)R energetically. The measured total reaction rate constant of CH(3)O(-) with O(2)(a(1)Δ(g)) is k = 6.9 × 10(-10) cm(3) s(-1) at 300 K, which is larger than that of k = 1.1 × 10(-12) cm(3) s(-1) for the reaction of CH(3)O(-) with O(2)(X(3)Σ(g)(-)). This is understandable because both P(1) and P(8) on the singlet PES can be generated barrierlessly, whereas to give all the products on the triplet PES has to pass the barrier of (3)1(1.8 kcal/mol) at the CCSD(T)//QCISD level. It is expected that the present theoretical study may be helpful for understanding the reaction mechanisms related to CH(3)O(-) and even CH(3)S(-).

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