Helical Cage Rotors Switched on by Brake Molecule with Variable Fluorescence and Circularly Polarized Luminescence.

While chiral molecular rotors have unique frames and cavities to possibly generate switchable chiroptical functions, it still remains a formidable challenge to precisely restrict their rotations to activate certain functions such as fluorescence as well as circularly polarized luminescence (CPL), which are strongly related to the local molecular rotations. Herein, we design a pair of enantiopure helical cage rotors, which emit light neither at the molecular state nor in the crystal or aggregation states, although they contain luminophore groups. However, upon mounting with fluoroaromatic borane (TFPB) as a molecular brake, the phenyl rotation of the helical cage can be effectively hindered and fluorescence and CPL activities of the molecular cage are switched on. Crystal structure analysis reveals that the rotation is restricted through synergistic B-O-H-N bonding and a fluoroaromatic-aromatic (ArF-Ar) dipole interaction. Moreover, the helical cages are switched on stepwise with color-variable fluorescence and CPL by the inner brake in the molecular state and the outer brake in the supramolecular assemblies, respectively. This work not only provides the design idea of chiroptical molecular rotors but also unveils how fluorescence and CPL could be generated in cage rotor systems.

N,N-Bis(2,4-Dibenzhydryl-6-cycloalkylphenyl)butane-2,3-diimine-Nickel Complexes as Tunable and Effective Catalysts for High-Molecular-Weight PE Elastomers.

Four examples of N,N-bis(aryl)butane-2,3-diimine-nickel(II) bromide complexes, [ArN=C(Me)-C(Me)=NAr]NiBr2 (where Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2 (Ni1), Ar = 2-(C6H11)-4,6-(CHPh2)2C6H2 (Ni2), 2-(C8H15)-4,6-(CHPh2)2C6H2 (Ni3) and 2-(C12H23)-4,6-(CHPh2)2C6H2 (Ni4)), disparate in the ring size of the ortho-cycloalkyl substituents, were prepared using a straightforward one-pot synthetic method. The molecular structures of Ni2 and Ni4 highlight the variation in the steric hindrance of the ortho-cyclohexyl and -cyclododecyl rings exerted on the nickel center, respectively. By employing EtAlCl2, Et2AlCl or MAO as activators, Ni1-Ni4 displayed moderate to high activity as catalysts for ethylene polymerization, with levels falling in the order Ni2 (cyclohexyl) > Ni1 (cyclopentyl) > Ni4 (cyclododecyl) > Ni3 (cyclooctyl). Notably, cyclohexyl-containing Ni2/MAO reached a peak level of 13.2 × 106 g(PE) of (mol of Ni)-1 h-1 at 40 °C, yielding high-molecular-weight (ca. 1 million g mol-1) and highly branched polyethylene elastomers with generally narrow dispersity. The analysis of polyethylenes with 13C NMR spectroscopy revealed branching density between 73 and 104 per 1000 carbon atoms, with the run temperature and the nature of the aluminum activator being influential; selectivity for short-chain methyl branches (81.8% (EtAlCl2); 81.1% (Et2AlCl); 82.9% (MAO)) was a notable feature. The mechanical properties of these polyethylene samples measured at either 30 °C or 60 °C were also evaluated and confirmed that crystallinity (Xc) and molecular weight (Mw) were the main factors affecting tensile strength and strain at break (εb = 353-861%). In addition, the stress-strain recovery tests indicated that these polyethylenes possessed good elastic recovery (47.4-71.2%), properties that align with thermoplastic elastomers (TPEs).

Volatile Dual-Solvent Assisted Intermediate Phase Regulation for Anti-Solvent-Free Perovskite Photovoltaics.

The unprecedented development of perovskite solar cells (PSCs) makes them one of the most promising candidates for terawatt-scale green energy production with low cost. However, the high boiling point solvents during the solution-processed film deposition cause anisotropic crystal growth and toxic solvent vapor during high-throughput manufacturing. Here, a dual-component green solvent consisting of isopropyl acetate and acetonitrile is proposed to form a volatile perovskite precursor, which can realize the high-quality perovskite thin film deposition by intermediate phase regulation. A room-temperature stable perovskite intermediate phase is constructed with the engagement of isopropyl acetate as co-solvent, which suppresses the exploding nucleation rate in volatile perovskite precursor, providing a fine grain growth rate and wide processing window in scalable film deposition. The corresponding PSCs fabricated by blade coating without anti-solvents or gas quenching achieve power conversion efficiency (PCE) of 16.37 % and 15.29 % for the areas of 14.08 cm2 and 37.83 cm2 , respectively.

Open-Cage Fullerene as a Selective Molecular Trap for LiF/[BeF].

The insertion of ionic compounds into open-cage fullerenes is a challenging task due to the electropositive nature of the cavity. The present work reports the preparation of an open-cage C60 derivative with a hydroxy group pointing towards the centre of the cavity, which can coordinate to a metal cation, thus acting as a bait/hook to trap the metal cation such as the lithium cation in neutral LiF and the beryllium cation in the cationic [BeF]+ species. Other metal salts could not be inserted under similar conditions. The structure of MF in the cage was unambiguously determined by single-crystal X-ray diffraction. Owing to its tendency to undergo polycoordination, Li+ monomer salts have not been isolated before, despite extensive research on Li bonds. The present results provide a unique example of a Li bond.

Exploring fluoride effects in sterically enhanced cobalt ethylene polymerisation catalysts; a combined experimental and DFT study.

The fluoro-substituted 2,6-bis(arylimino)pyridine dichlorocobalt complexes, [2-{CMeN(2,6-(Ph2CH)2-3,4-F2C6H)}-6-(CMeNAr)C5H3N]CoCl2 (Ar = 2,6-Me2C6H3 Co1, 2,6-Et2C6H3Co2, 2,6-iPr2C6H3Co3, 2,4,6-Me3C6H2Co4, 2,6-Et-4-MeC6H2Co5), were synthesized in good yield from the corresponding unsymmetrical N,N,N'-ligands, L1-L5. Besides characterization of Co1-Co5 by FT-IR spectroscopy, 19F NMR spectroscopy and elemental analysis, the molecular structures of Co2 and Co5 were also determined highlighting the unsymmetrical nature of the terdentate ligand and the pseudo-square pyramidal geometry about the metal center. When either MAO or MMAO were employed as activators, Co1-Co5 were able to achieve a wide range of catalytic activities for ethylene polymerisation. Co5/MAO exhibited the highest activity of the study at 60 °C (7.6 × 106 g PE mol-1 (Co) h-1) which decreased to 3.3 × 106 g PE mol-1 (Co) h-1 at 80 °C. In addition, it was found that the polymerisation activity increased as the steric hindrance imparted by the ortho groups was enhanced (for MMAO: Co3 > Co5 > Co2 > Co1 > Co4), a finding that was supported by DFT calculations. Furthermore, it was shown that particularly high molecular weight polyethylene could be generated (up to 483.8 kg mol-1) when using Co5/MMAO at 30 °C, while narrow dispersities (M w/M n range: 1.8-4.7) and high linearity (T m > 131.4 °C) were a feature of all polymers produced. By comparison of Co3 with its non-fluorinated analogue using experimental data and DFT calculations, the substitution of fluorides at the meta- and para-positions was demonstrated to boost catalytic activity and improve thermal stability.

High molecular weight PE elastomers through 4,4-difluorobenzhydryl substitution in symmetrical α-diimino-nickel ethylene polymerization catalysts.

The following family of N,N-diaryl-2,3-dimethyl-1,4-diazabutadienes, ArN[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]NAr (Ar = 2,6-Me2-4-{CH(4-FC6H4)2}C6H2L1, 2-Me-6-Et-4-{CH(4-FC6H4)2}C6H2L2, 2,4-{CH(4-FC6H4)2}2-6-MeC6H2L3, 2,4-{CH(4-FC6H4)2}2-6-EtC6H2L4, 2,4-{CH(4-FC6H4)2}2-6-iPrC6H2L5), each incorporating para-substituted 4,4-difluorobenzhydryl groups but differing in the ortho-pairing, have been synthesized and used as precursors to their respective nickel(ii) bromide complexes, Ni1-Ni5. Compound characterization has been achieved through a combination of FT-IR, multinuclear NMR spectroscopy (1H, 13C, 19F) and elemental analysis. In addition, L1, Ni1 and Ni5 have been structurally characterized with Ni1 and Ni5 revealing similarly distorted tetrahedral geometries about nickel but with distinct differences in the steric protection offered by the ortho-substituents. All nickel complexes, under suitable activation, showed high activity for ethylene polymerization with a predilection towards forming branched high molecular weight polyethylene with narrow dispersity. Notably the most sterically bulky Ni5, under activation with either EtAlCl2, Et2AlCl or EASC, was exceptionally active (0.9-1.0 × 107 g of PE per (mol of Ni) per h) at an operating temperature of 40 °C. Furthermore, the polyethylene generated displayed molecular weights close to one million g mol-1 (M w range: 829-922 kg mol-1) with high branching densities (86-102/1000 carbons) and a selectivity for short chain branches (% Me = 94.3% (EtAlCl2), 87.2% (Et2AlCl), 87.7% (EASC)). Further analysis of the mechanical properties of the polymers produced at 40 °C and 50 °C using Ni5 highlighted the key role played by crystallinity (X c) and molecular weight (M w) on tensile strength (σ b) and elongation at break (ε b). In addition, stress-strain recovery tests reveal these high molecular weight polymers to exhibit characteristics of thermoplastic elastomers (TPEs).

Fluorinated 2,6-bis(arylimino)pyridyl iron complexes targeting bimodal dispersive polyethylenes: probing chain termination pathways via a combined experimental and DFT study.

In this work, fluorinated 2,6-bis(arylimino)pyridyl iron(II) complexes, [2-[CMeN{2,4-{(4-FC6H4)2CH}2-6-F}]-6-(CMeNAr)C5H3N]FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-iPr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, and 2,6-Et2-4-MeC6H2Fe5) and [2-[CMeN{2-{(4-FC6H4)2CH}-4-{(C6H5)CHAr'}-6-F}]-6-(CMeN(2,6-iPr2C6H3))C5H3N]FeCl2 (Ar' = 3-{(4-FC6H4)2CH}2-4-NH2-5-FC6H2Fe6), verified with different steric substituents, were synthesized and characterized. The molecular structures of Fe2 and Fe3 were determined by X-ray diffraction, revealing a pseudo-square-pyramidal geometry. High activities were achieved toward ethylene polymerization in each iron complex case. The sterically least demanding ligand enhanced the activity of its complex Fe1 with the highest activity up to 16.8 × 106 g of PE (mol of Fe)-1 h-1at 70 °C, while the bulkiest ligand led to the formation of the highest molecular weight of the resulting polyethylene using Fe6. Generally, the resulting polyethylenes are highly linear and most of them have a tendency to display bimodal distributions by virtue of the presence of multiple sites or competing chain transfer reactions. End-group analysis of polyethylenes confirms that the end groups include both unsaturated vinyl-end groups and saturated n-propyl or i-butyl, revealing the co-existence of two chain termination pathways including primary chain transfer to aluminium and secondary ß-H transfer. The chain termination processes were interpreted with the 1D sequence inverse-gated decoupled 13C NMR measurement of the resulting polyethylenes and DFT calculations along with the relevant polymerization mechanism.

Fluorinated Sterically Bulky Mononuclear and Binuclear 2-Iminopyridylnickel Halides for Ethylene Polymerization: Effects of Ligand Frameworks and Remote Substituents.

In the present work, four new mono(imino)pyridine ligands, 2-((2,4-bis(bis(4-R-phenyl)methyl)-6-fluorophenylimino)methyl)pyridine (R = H, L1; R = OCH3, L2; R = F, L3) and 2-((2-(bis(4-fluorophenyl)methyl)-4-((3-(bis(4-fluorophenyl)methyl)-4-amine-5-fluoro-phenyl)(phenyl)methyl)-6-fluorophenylimino)methyl)pyridine (L4), have been designed in good yields. Additionally, three novel benzhydryl-bridged bis(imino)pyridine ligands, 2-(2-(bis(4-R-phenyl)methyl)-6-fluoro-phenylimino)pyridine (R = H, L5; R = OCH3, L6; R = F, L7), were also prepared for comparison. All these organic compounds have been characterized by FT-IR analysis, 1H/13C NMR spectroscopy, and elemental analysis. The treatment of L1-L7 with nickel halides afforded the corresponding monometallic (Ni1-Ni4) and bimetallic (Ni5-Ni7) nickel complexes in moderate to good overall yields. Upon activation with methylaluminoxane (MAO), Ni4 Cl showed the highest activity up to 8.3 × 106 g of polyethylene (PE) (mol of Ni)-1 h-1 among Ni1-Ni7 for ethylene polymerization. In all cases, unsaturated PEs with low molecular weights (0.7-13.3 kg mol-1) were produced effectively. The introduction of remote para-substituents into the benzhydryl groups showed a beneficial effect on catalytic activity with the overall activities following the order of Ni-F > Ni-OCH3 > Ni-H. In addition, these para-substituents were also found to affect not only the catalytic performance of catalysts but also the branching content of the PE product. Generally, the resultant PE waxes were moderately branched and contained both terminal vinyls (-CH=CH2) and internal vinylenes (-CH=CH-) while with different ratios of vinyls to vinylenes. Notably, the polymers produced using para-methoxy-substituted Ni2/MAO and Ni6/MAO possessed the least branching content and uniquely high vinyl contributions.

Enhancing Ethylene Polymerization of NNN-Cobalt(II) Precatalysts Adorned with a Fluoro-substituent.

Unsymmetrical 2-(1-(2,4-dibenzhydryl-6-fluorophenylimino)ethyl)-6-(1-alkylphenyl-imino)ethyl)pyridine compounds (Ar = 2,6-Me2C6H3 in L1; 2,6-Et2C6H3 in L2; 2,6- i Pr2C6H3 in L3; 2,4,6-Me3C6H2 in L4; 2,6-Et2-4-Me-C6H2 in L5) were prepared and characterized. The treatment of CoCl2 with the compounds L1-L5 afforded the corresponding cobalt complexes Co1-Co5 in excellent yields. The molecular structures of Co3 and Co4 were determined by single-crystal X-ray diffraction, revealing the distorted-square-pyramidal geometry with three nitrogen atoms and two chlorine atoms around the cobalt center. Compared with previous bis(imino)pyridylcobalt analogues, all of the cobalt precatalysts displayed exceptionally higher activities toward ethylene polymerization with 1.32 × 107 g (PE) mol-1 (Co) h-1 at 60 °C in the presence of a co-catalyst MAO or MMAO. These cobalt catalysts produced highly linear polyethylene (PE) waxes with vinyl end groups and low molecular weight (M w up to 8.23 kg mol-1) along with a relatively lower melting point (all-round T ms < 128 °C). The narrow dispersity of resultant polyethylenes indicated the single-site active species of the catalytic system.

Bimetallic aluminum complexes bearing novel spiro-phenanthrene-monoketone/OH derivatives: synthesis, characterization and the ring-opening polymerization of ε-caprolactone.

A series of spiro-phenanthrene-monoketone/OH derivatives (L1-L6) were synthesized and fully characterized with 1H/13C NMR spectroscopy and elemental analyses. By treating ligands with AlMe3, oxygen-bridged binuclear aluminum complexes (Al1-Al6) were isolated and characterized by 1H/13C NMR spectroscopy. The molecular structures of ligands (L2, L4 and L5) and complex Al1 were determined by single crystal X-ray diffraction. In the presence of benzyl alcohol (BnOH), these aluminum complexes demonstrated high efficiency towards the ring-opening polymerization of ε-caprolactone (ε-CL), resulting in PCL in a linear manner with the BnO-end group. In addition, complexes Al1 and Al5 exhibited good catalytic activities even without BnOH. Moreover, complexes Al3 and Al6 with the bulkier substituent of iPr at the ortho-position of the arylamines demonstrated better catalytic activities than the analogs. Moreover, substituents on the backbone also affected catalytic behaviors.

Bis(imino)-6,7-dihydro-5H-quinoline-cobalt complexes as highly active catalysts for the formation of vinyl-terminated PE waxes; steps towards inhibiting deactivation pathways through targeted ligand design.

A set of five related bis(imino)-6,7-dihydro-5H-quinoline-cobalt(ii) complexes, [2-(ArN = CPh)-8-(NAr)-C9H8N]CoCl2 (Ar = 2,6-Me2C6H3Co1, 2,6-Et2C6H3Co2, 2,6-i-Pr2C6H3Co3, 2,4,6-Me3C6H2Co4, 2,6-Et2-4-MeC6H2Co5), have been synthesized in reasonable yield by the template reaction of cobalt(ii) chloride hexahydrate, 2-benzoyl-6,7-dihydro-5H-quinolin-8-one and the corresponding aniline. The molecular structures of Co1 and Co4 highlight both the differences in the two imino-carbon environments (phenyl-capped chain vs. cyclic) and also the steric properties exerted by the bulky N imine-aryl groups. On pre-treatment with either modified methylaluminoxane (MMAO) or methylaluminoxane (MAO), all complexes proved productive catalysts for the polymerization of ethylene. In particular, Co1/MAO was the most active reaching a very high level of 1.62 × 107 g PE per mol (Co) per h over a 30 minute run time. Owing to the presence of the imino-phenyl substituent, Co1-Co5 were able to exhibit good thermal stability by displaying appreciable catalytic activity at temperatures between 50 and 80 °C, generating polyethylenes with narrow dispersities (M w/M n range: 1.66-3.28). In particular, the least sterically bulky precatalysts, Co1 and Co4 formed polyethylene waxes (M w range: 1.94-5.69 kg per mol) with high levels of vinyl unsaturation as confirmed by high temperature 1H/13C NMR spectroscopy and by IR spectroscopy.

Unifying Molecular Weights of Highly Linear Polyethylene Waxes through Unsymmetrical 2,4-Bis(imino)pyridylchromium Chlorides.

By dealing CrCl3∙3THF with the corresponding ligands (L1-L5), an array of fluoro-substituted chromium (III) chlorides (Cr1-Cr5) bearing 2-[1-(2,4-dibenzhydryl-6-fluoro- phenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine (aryl = 2,6-Me2Ph Cr1, 2,6-Et2Ph Cr2, 2,6-iPr2Ph Cr3, 2,4,6-Me3Ph Cr4, 2,6-Et2-4-MePh Cr5) was synthesized in good yield and validated via Fourier Transform Infrared (FT-IR) spectroscopy and elemental analysis. Besides the routine characterizations, the single-crystal X-ray diffraction study revealed the solid-state structures of complexes Cr2 and Cr4 as the distorted-octahedral geometry around the chromium center. Activated by either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the chromium catalysts exhibited high activities toward ethylene polymerization with the MMAO-promoted polymerizations far more productive than with MAO (20.14 × 106 g (PE) mol-1 (Cr) h-1 vs. 10.03 × 106 g (PE) mol-1 (Cr) h-1). In both cases, the resultant polyethylenes were found as highly linear polyethylene waxes with low molecular weights around 1-2 kg mol-1 and narrow molecular weight distribution (MWD range: 1.68-2.25). In general, both the catalytic performance of the ortho-fluorinated chromium complexes and polymer properties have been the subject of a detailed investigation and proved to be highly dependent on the polymerization reaction parameters (including cocatalyst type and amount, reaction temperature, ethylene pressure and run time).

Aza-crown compounds synthesised by the self-condensation of 2-amino-benzyl alcohol over a pincer ruthenium catalyst and applied in the transfer hydrogenation of ketones.

A well-defined PNN-Ru catalyst was revisited to self-condense 2-aminobenzyl alcohol in forming a series of novel aza-crown compounds [aza-12-crown-3 (1), aza-16-crown-4 (2) and aza-20-crown-5 (3)]. All aza-crown compounds are separated and determined by NMR, IR, and ESI-MS spectroscopy as well as X-ray crystallography, indicating the saddle structure of 1 and the twisted 1,3-alternate conformation structure of 3. These aza-crown compounds have been explored to study ferric initiation of transfer hydrogenation (TH) of ketones into their corresponding secondary alcohols in the presence of 2-propanol with a basic t-BuOK solution, achieving a high conversion (up to 95%) by a ferric complex with 2 in a low loading (0.05 mol%).

Bis-cycloheptyl-fused bis(imino)pyridine-cobalt catalysts for PE wax formation: positive effects of fluoride substitution on catalytic performance and thermal stability.

The α,α'-bis(imino)-2,3:5,6-bis(pentamethylene)pyridyl-cobalt(ii) chlorides, [2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2))}2C5HN] CoCl2 (R1 = Me, R2 = R3 = CH(p-FPh)2Co1; R1 = Et, R2 = R3 = CH(p-FPh)2Co2; R1 = i-Pr, R2 = R3 = CH(p-FPh)2Co3; R1 = Cl, R2 = R3 = CH(p-FPh)2Co4; R1 = F, R2 = R3 = CH(p-FPh)2Co5; R1 = F, R2 = R3 = CHPh2Co5'', R1 = R2 = Me, R3 = CH(p-FPh)2Co6; R1 = R3 = Me, R2 = CH(p-FPh)2Co7), have been synthesized by a one-pot template reaction of α,α'-dioxo-2,3:5,6-bis(pentamethylene)pyridine, cobalt(ii) chloride and the respective aniline in n-butanol. By contrast, the mixed cobalt(ii) chloride/acetate complex, [2,3:5,6-{C4H8C(N(2-F-4,6-(CH(p-FPh)2)2C6H2))}2C5HN]CoCl(OAc) (Co5'), was isolated when the corresponding template reaction was carried out in acetic acid. Structural characterization of Co4, Co5 and Co5'' revealed distorted square pyramidal geometries while six-coordinate Co5', incorporating a chelating acetate ligand, exhibited a distorted octahedral geometry. On activation with either MAO or MMAO, 2-fluoride-4,6-bis{di(p-fluorophenyl)methyl}-substituted Co5 showed maximum catalytic activity for ethylene polymerization at a high operating temperature of 60 °C (up to 2.1 × 107 g (PE) mol-1 (Co) h-1), producing highly linear (Tms > 121 °C), low molecular weight polyethylene waxes (Mw range: 1.5-5.0 kg mol-1) with narrow dispersity (Mw/Mn range: 1.7-2.9). End-group analysis of the waxes reveals ß-H elimination as the dominant chain transfer process.

4,4'-Difluorobenzhydryl-modified bis(imino)-pyridyliron(ii) chlorides as thermally stable precatalysts for strictly linear polyethylenes with narrow dispersities.

The 4,4'-difluorobenzhydryl-modified bis(imino)pyridylferrous chlorides, [2-{CMeN(2,6-(4-FC6H4)2CH2-4-t-BuC6H2)}-6-(CMeNAr)C5H3N] FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-i-Pr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, 2,6-Et-4-MeC6H2Fe5 and 2,6-(4-FC6H4)2CH2-4-t-BuC6H2Fe6), were synthesized in good yields. All iron complexes were characterized by 1H/19F NMR and elemental analysis, and the molecular structures of representative complexes Fe1 and Fe6 were determined by single crystal X-ray diffraction, which revealed a slightly distorted square pyramid around the iron center. Activated with either MAO or MMAO, Fe1-Fe5 exhibited very high activities (up to 17.2 × 106 g (PE) mol-1 (Fe) h-1 for Fe1/MMAO) toward ethylene polymerization, producing highly linear polyethylenes with narrow dispersities as required by industry and value added PEs. Importantly, the Fe1/MAO maintained an activity of 9.5 × 106 g (PE) mol-1 (Fe) h-1 at 100 °C of operating temperature, making the catalytic system suitable for practical application. Simulation quantitatively revealed the mechanism of the enhanced catalytic performance from the electronic and steric point of view.

Charge transfer co-crystals based on donor-acceptor interactions for near-infrared photothermal conversion.

A co-crystal was obtained based on donor-acceptor interactions. The obvious charge transfer from the linear donor to the triangular acceptor units results in a quasi-two-dimensional CT complex with excellent near-infrared photothermal conversion efficiency. The co-crystals further acted as an excellent photothermal material in seawater desalination.

Chiral Reticular Self-Assembly of Achiral AIEgen into Optically Pure Metal-Organic Frameworks (MOFs) with Dual Mechano-Switchable Circularly Polarized Luminescence.

Circularly polarized luminescence (CPL) is attractive in understanding the excited-state chirality and developing advanced materials. Herein, we propose a chiral reticular self-assembly strategy to unite achiral AIEgens, chirality donors, and metal ions to fabricate optically pure AIEgen metal-organic frameworks (MOFs) as efficient CPL materials. We have found that CPL activity of the single-crystal AIEgen MOF was generated by the framework-enabled strong emission from AIEgens and through-space chirality transfer from chirality donors to achiral AIEgens via metal-ion bridges. For the first time, a dual mechano-switched blue and red-shifted CPL activity was achieved via ultrasonication and grinding, which enabled the rotation or stacking change of AIEgen rotors with the intact homochiral framework. This work provided not only an insightful view of the aggregation induced emission (AIE) mechanism, but also an efficient and versatile strategy for the preparation of stimuli-responsive CPL materials.

High molecular weight polyethylenes of narrow dispersity promoted using bis(arylimino)cyclohepta[b]pyridine-cobalt catalysts ortho-substituted with benzhydryl & cycloalkyl groups.

A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(ii) chlorides, [2-{(Ar)N[double bond, length as m-dash]CMe}-9-{N(Ar)}C10H10N]CoCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Co1, 2-(C6H11)-4,6-(CHPh2)2C6H2Co2, 2-(C8H15)-4,6-(CHPh2)2C6H2Co3, 2-(C12H23)-4,6-(CHPh2)2C6H2Co4, 2,6-(C5H9)2-4-(CHPh2)C6H2Co5). All five complexes have been characterized by a combination of FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Co1, Co3 and Co5 highlight the substantial steric hindrance imparted by the 2-cycloalkyl-6-benzhydryl or 2,6-dicyclopentyl ortho-substitution pattern; distorted square pyramidal geometries are exhibited in each case. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the complexes (apart from Co4/MAO) were active ethylene polymerization catalysts (up to 3.70 × 106 g PE per mol (Co) per h for Co5/MMAO), operating effectively at temperatures between 50 °C and 60 °C, producing polyethylenes with high molecular weights (up to 589.5 kg mol-1 for Co3/MAO). Furthermore, all polymers were highly linear (Tm > 130 °C) with narrow dispersities (Mw/Mn range: 2.0-3.0). The coexistence of two chain termination pathways, ß-H elimination and transfer to aluminum, has been demonstrated using 13C/1H NMR spectroscopy.

Correction: A hexagonal Ni6 cluster protected by 2-phenylethanethiol for catalytic conversion of toluene to benzaldehyde.

Correction for 'A hexagonal Ni6 cluster protected by 2-phenylethanethiol for catalytic conversion of toluene to benzaldehyde' by Anthony M. S. Pembere et al., Phys. Chem. Chem. Phys., 2019, 21, 17933-17938.

Achieving polydispersive HDPE by N,N,N-Co precatalysts appended with N-2,4-bis(di(4-methoxyphenyl)methyl)-6-methylphenyl.

A family of unsymmetrical 2-(2,4-bis(di(4-methoxyphenyl)methyl)-6-MeC6H2N)-6-(1-(arylimino)ethyl)pyridine-cobalt dichloride complexes has been synthesized and characterized by NMR spectroscopy, FT-IR spectroscopy and elemental analysis as well as single crystal X-ray diffraction for Co2 and Co4. Activated with either MAO or MMAO, all the cobalt precatalysts displayed high activities toward ethylene polymerization and produced highly linear polyethylenes with high molecular weights as well as wide polydispersities; for example, the performance using Co1/MAO at 50 °C reached 9.17 × 106 g PE (mol of Co)-1 h-1 with the production polyethylene of molecular weight as high as M w = 3.14 × 105 g mol-1, T m = 134.3 °C besides its wide polydispersity of M w/M n of 54.6. Besides the terminal vinyl group of the resultant polyethylenes, it is rare for a late-transition metal catalyst to achieve highly linear polyethylenes with not only wide polydispersity but also high molecular weights, being similar to high-density polyethylenes produced using Phillips catalyst.