Azofra, Luis Miguel; Veenboer, Richard M. P.; Falivene, Laura; Vummaleti, Sai V. C.; Poater, Albert; Nolan, Steven P.; Cavallo, Luigi(Physical Chemistry Chemical Physics, Royal Society of Chemistry (RSC), 2019)[Article]
A series of NHC–gold(I) (NHC = N-heterocyclic carbene) complexes has been studied by DFT calculations, enabling comparison of electronic and NMR behaviour with related protonated and free NHC molecules. Based on calculations, the NMR resonances of the carbenic C2 carbon atom in [Au(NHC)(Cl)] and [NHC(H)][Cl] exhibit increased shielding when compared to the free N-heterocyclic carbenes by an average of 46.6 ± 2.2 and 73.7 ± 4.3 ppm, respectively. A similar trend is observed when analysing the paramagnetic term of the magnetic shielding tensor. Although gold(I) and proton are considered isolobal fragments, imidazolium compounds lack π-backdonation due to the energetic unavailability of d-orbitals in H+. We propose that NHC–gold(I) complexes exhibit important π-backdonation irrespective of the relative amount of σ-donation between the NHC and gold(I)–X (X = anionic ligand) moieties in Au–NHC complexes. Interestingly, a correlation exists between the calculated shielding for gold (197Au) and the π-donation and π-backdonation contributions. We describe that this correlation also exists when analysing the σ-backdonation term, a property generally ignored yet representing a significant energetic contribution to the stability of the C2–Au bond.
Nolan, Steven P; Zinser, Caroline; Falivene, Laura; Nahra, Fady; Brill, Marcel; Cordes, David Bradford; Slawin, Alexandra; Cavallo, Luigi; Cazin, Catherine(Chemical Communications, Royal Society of Chemistry (RSC), 2019)[Article]
A new class of [Au(NHC)(Bpin)] complexes has been synthesized and their unusual reactivity was investigated using computational and experimental methods. The gold-boryl complexes exhibit unexpected high stability and reactivity.
Veenboer, Richard M P; Azofra, Luis Miguel; Gasperini, Danila; Collado, Alba; Cordes, David B; Slawin, Alexandra M Z; Cavallo, Luigi; Nolan, Steven P(Dalton Transactions, Royal Society of Chemistry (RSC), 2019)[Article]
New [Au(IPr)(CHR2)] complexes have been synthesised through protonolysis reactions of [Au(IPr)(OH)] with moderately acidic substrates, CH2R2. An array of spectroscopic (IR and NMR), structural (X-ray), electronic (DFT) and experimental (reactivity) parameters was collected to quantify the variation in stereoelectronic properties of these new and previously reported [Au(IPr)(CHR2)] complexes. Variation of the R substituents on the carbanion ligands (CHR2-) was found to have a crucial impact on parameters characterising the resulting gold complexes. A regression analysis of both experimental and modelled parameters, guided by network analysis techniques, produced linear models that supported trends within the [Au(IPr)(CHR2)] complexes.
Zhang, Jiao; Zhou, Lin; Ming, Hai; Wu, Yingqiang; Wahyudi, Wandi; Cao, Zhen; Cavallo, Luigi; Wang, Limin; Ming, Jun(Chemical Communications, Royal Society of Chemistry (RSC), 2019)[Article]
A new synergistic lithium ion solvation structure effect tailored by mixed organic/inorganic lithium salts is introduced to mitigate the growth of lithium-dendrites. A uniform lithium plating, lower polarization and higher coulombic efficiency are confirmed by lithium plating/stripping. The effect of different solvation structures was analyzed by Raman spectroscopy and simulations. Then, a reliable lithium-sulfur full battery with high performance over hundreds of cycles was configured.
Yue, Huifeng; Zhu, Chen; Shen, Li; Geng, Qiuyang; Hock, Katharina J.; Yuan, Tingting; Cavallo, Luigi; Rueping, Magnus(Chemical Science, Royal Society of Chemistry (RSC), 2019)[Article]
Nickel-catalyzed reductive cross coupling of activated primary amines with aryl halides under mild reaction conditions has been achieved for the first time. Due to the avoidance of stoichiometric organometallic reagents and external bases, the scope regarding both coupling partners is broad. Thus, a wide range of substrates, natural products and drugs with diverse functional groups are tolerated. Moreover, experimental mechanistic investigations and density functional theory (DFT) calculations in combination with wavefunction analysis have been performed to understand the catalytic cycle in more detail.
Bidal, Yannick D.; Urbina-Blanco, César A.; poater, albert; Cordes, David B.; Slawin, Alexandra M. Z.; Cavallo, Luigi; Cazin, Catherine S. J.(Dalton Transactions, Royal Society of Chemistry (RSC), 2019)[Article]
Five new complexes [RuCl2(SIMes)(Ind)(O-pXC5H4)] bearing different para-substituted triphenylphosphites (X = H, OCH3, CF3, Cl, SF5 and CN) were synthesised and used to study the effect of the electronic properties of the phosphite on olefin metathesis activity. Investigations of the physical properties of the new ligands and complexes were performed using physicochemical and DFT calculations. The catalytic activity of the complexes was benchmarked in challenging ring closing metathesis transformations featuring the formation of tetra-substituted double bonds. Complex [RuCl2(SIMes)(Ind)P(O-pCF3C5H4)3] (3c) exhibited a particularly high catalytic activity, superior to state-of-the-art catalysts, and was further tested on a wide range of substrates.
A simple and efficient catalyst, benzimidazole (BIMH)-modified copper foil, is developed to enhance the selective conversion of CO2 to C2/C3 products. The overall faradaic efficiency (FE) for CO2 reduction reaches 92.1% and the undesired hydrogen evolution reaction (HER) is lowered to a FE of 7% at -1.07 VRHE.
Wang, Ning; Cao, Zhen; Kong, Xiangbin; Liang, Junhui; Zhang, Qixing; Zheng, Lirong; Wei, Changchun; Chen, Xinliang; Zhao, Ying; Cavallo, Luigi; Zhang, Bo; Zhang, Xiaodan(Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), 2018)[Article]
The oxygen evolution reaction (OER) is a key process in electrocatalysis and is critical for achieving the cost-effective conversion of renewable electricity to chemicals and fuels. However, the high overpotential (η) originates from poor charge-transfer ability and low catalytic activity may lead to high power consumption. Herein, we alleviate these issues by introducing borate into the NiFe (oxy)hydroxide framework. Our density functional theory (DFT) calculations demonstrated that the borate could be efficiently adsorbed onto the Ni/NiFe (oxy)hydroxide surface. Microscopically, the adsorbed borate can induce a favorable electronic structure for the Ni active sites. Meanwhile, the macroscopic charge-transfer ability of this synthesized catalyst has been dramatically increased. Hence, the catalytic performance of this material is improved compared with its NiFe counterpart: we achieved a higher OER activity with an ultralow η of only 230 mV at 10 mA cm on a glassy carbon electrode (GCE) and of 200 mV at 10 mA cm on Ni foam in alkaline medium. Moreover, this borate mediated NiFe (oxy)hydroxide is very stable: no appreciable degradation is observed after more than 110 hours of operation.
Zhang, Junli; Fu, Jiecai; Shi, Fangyi; Peng, Yong; Si, Mingsu; Cavallo, Luigi; Cao, Zhen(Nanoscale, Royal Society of Chemistry (RSC), 2018)[Article]
Atomic layered two-dimensional (2D) materials have become fascinating research topics due to their intriguing performances, but the limitation of nonmagnetic properties hinders their further applications. Developing versatile strategies endowing 2D materials with ferromagnetism is one of the main trends in current research studies. Herein, a hydrogen plasma strategy is introduced to dope hydrogen (H) atoms into the prototypical layered α-MoO3 nanosheets, by which ferromagnetic and exchange bias (EB) effects can be induced by H atom doping into α-MoO3 to form HxMoO3. These effects were interpreted by density functional theory (DFT) calculations. We find that H atom doping can introduce unoccupied states and induce a net magnetic moment localized on the d orbital of the Mo atom, because of the generated asymmetric distribution of electronic states on the Mo atom near the Fermi level. Moreover, the saturation magnetization and the EB field (He) of hydrogenated α-MoO3 are found to be tunable through altering the amount of H dopant. This work provides new perspectives for the effective manipulation of ferromagnetism and exchange interaction through H doping. We hope that the presented hydrogenation strategy is applicable for other kinds of 2D materials.
Werghi, Baraa; Pump, Eva; Tretiakov, Mykyta; Abou-Hamad, Edy; Gurinov, Andrei; Doggali, Pradeep; Anjum, Dalaver H.; Cavallo, Luigi; Bendjeriou-Sedjerari, Anissa; Basset, Jean-Marie(Chemical Science, Royal Society of Chemistry (RSC), 2018)[Article]
Immobilization of the 2 generation Hoveyda-Grubbs catalyst HG-II onto well-ordered 2D hexagonal (SBA15) and 3D fibrous (KCC-1) mesostructured silica, which contained tetra-coordinated Al, has been investigated through the Surface Organometallic Chemistry (SOMC) methodology. The main interest of this study lies in the peculiarity of the silica supports, which display a well-defined tetrahedral aluminum hydride site displaying a strong Lewis acid character, [(Si-O-Si)(Si-O-)Al-H]. The resulting supported Hoveyda-Grubbs catalysts have been fully characterized by advanced solid state characterization techniques (FT-IR, H and C solid state NMR, DNP-SENS, EF-TEM...). Together with DFT calculations, the immobilization of HG-II does not occur through the formation of a covalent bond between the complex and the Al-modified mesoporous silica as expected, but through an Al⋯Cl-[Ru]-coordination. It is not surprising that in functionalized olefin metathesis of diethyldiallyl malonate, DEDAM (liquid phase), leaching of the catalyst is observed which is not the case in non-functionalized olefin metathesis of propene (gas phase). Besides, the results obtained in propene metathesis with HG-II immobilized either on SBA15 (d = 6 nm) or KCC-1 (d = 4 or 8 nm) highlight the importance of the accessibility of the catalytic site. Therefore, we demonstrate that KCC-1 is a promising and suitable 3D mesoporous support to overcome the diffusion of reactants into the porous network of heterogeneous catalysts.
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