Proteins are an endless source of inspiration. By carefully tuning the amino‐acid sequence of proteins, nature made them evolve from primary to quaternary structures, a property specific to protein oligomers and often crucial to accomplish their function. On the other hand, the synthetic macrocycles cucurbiturils (CBs) have shown outstanding recognition properties in water, and a growing number of (host)n:(guest)n supramolecular polymers involving CBs have been reported. However, the burgeoning field of discrete (n:n) host:guest oligomers has just started to attract attention. While 2:2 complexes are the major oligomers, 3:3 and up to 6:6 oligomers have been described, some associated with emerging applications, specific to the (n:n) arrangements. Design rules to target (n:n) host:guest oligomers are proposed toward new advanced host:guest systems.

The copolymerization of ethylene with polar monomers is a major challenge when it comes to the manufacture of materials with potential for a wide range of commercial applications. In the chemical industry, free-radical polymerization is used to make a large proportion of such copolymers, but the forcing conditions result in a lack of fine control over the architecture of the products. Herein we introduce a synthetic tool, effective under mild experimental conditions, for the precision design of unprecedented ethylene- and polar-monomer-based copolymers. We demonstrate how an organocobalt species can control the growth of the copolymer chains, their composition and the monomer distribution throughout the chain. By fine tuning the ethylene pressure during polymerization and by exploiting a unique reactive mode of the end of the organometallic chain, novel block-like copolymer structures can be prepared. This highly versatile synthetic platform provides access to a diverse range of polymer materials.

International audienceA short review on the role of photocatalysts in photopolymerization reactions is presented. A special emphasis is done on photoredox catalysts leading to i) high performance initiating systems for polymerization upon low light intensity for the use of light emitting diodes (LEDs) and/or visible light or ii) Controlled Radical PhotoPolymerization (CRP2) processes with formation/reactivation of dormant species triggered by light

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The determination of the nature and structure of surface sites after chemical modification of large surface area oxides such as silica is a key point for many applications and challenging from a spectroscopic point of view. This has been, for instance, a long-standing problem for silica reacted with alkylaluminum compounds, a system typically studied as a model for a supported methylaluminoxane and aluminum cocatalyst. While (27)Al solid-state NMR spectroscopy would be a method of choice, it has been difficult to apply this technique because of large quadrupolar broadenings. Here, from a combined use of the highest stable field NMR instruments (17.6, 20.0, and 23.5 T) and ultrafast magic angle spinning (>60 kHz), high-quality spectra were obtained, allowing isotropic chemical shifts, quadrupolar couplings, and asymmetric parameters to be extracted. Combined with first-principles calculations, these NMR signatures were then assigned to actual structures of surface aluminum sites. For silica (here SBA-15) reacted with triethylaluminum, the surface sites are in fact mainly dinuclear Al species, grafted on the silica surface via either two terminal or two bridging siloxy ligands. Tetrahedral sites, resulting from the incorporation of Al inside the silica matrix, are also seen as minor species. No evidence for putative tri-coordinated Al atoms has been found.

The P,N-type ligands 2-[(diphenylphosphino)methyl]pyridine (12), 2-[2-(diphenylphosphino)ethyl]pyridine (13), 2-methyloxy(diphenylphosphino)pyridine (14), 2-methyloxy(dibenzyl-1,2-oxaphosphorino)pyridine (15), and 2-methyloxy(di-tert-butylphosphino)pyridine (16) have been prepared in good yields, and 12 and 13 have been used to synthesize Ni(II) complexes of formula [Ni(P,N)Cl2], 17 (P,N = 12) and 18 (P,N = 13), by reaction with NiCl2 in methanol. The crystal structure of 18 has been determined by X-ray diffraction to be dinuclear with a distorted square-base pyramidal geometry around the Ni(II) centers. To examine the possible influence of the nature of the spacer link between the P and N donor atoms, we compared ligand 13, with a CH2CH2 spacer, with 14 and 16, which have a isosteric CH2-O spacer. Reactions of the phosphinitopyridine ligands 14 and 16 and of the phosphonitopyridine 15 with [NiX2(DME)] (X = Cl or Br) afforded the complexes [Ni(P,N)Cl2] 20 (X = Cl; P,N = 14), 21 (X = Br; P,N = 14), 22 (X = Cl; P,N = 16), and 23 (X = Cl; P,N = 15), respectively. The mononuclear structure of complex 22 has been established by X-ray diffraction and showed a distorted tetrahedral geometry around the metal center. Complexes 17, 18, and 20−22 have been tested as precatalysts in the oligomerization of ethylene, with AlEtCl2 or MAO as cocatalyst, in order to evaluate the influence of the stereoelectronic properties of the phosphorus substituents. With only 6 equiv of AlEtCl2 as cocatalyst and 4 × 10−5 mol precatalyst, complex 18 was the most active, with turnover frequencies (TOF) up to 91 200 C2H4/(mol Ni·h), and 20 with 2 equiv of AlEtCl2 showed the highest selectivities for ethylene dimers (up to 97%) and in 1-butene (up to 72%). When only 10−5 mol precatalyst was used, the TOF values went up to 207 600 for 18 and 150 100 for 20. With only 25 equiv of MAO as cocatalyst, complex 18 was again the most active, with TOF values up to 20 600 C2H4/(mol Ni·h). Despite the high selectivity for C4 olefins of 17, 18, 20, and 21 (up to 93% for 20), 22 presented the best selectivities for 1-butene (up to 73%) with MAO as cocatalyst, and its high reactivity for the reinsertion of 1-butene resulted in 2-ethyl-1-butene being the main product of the catalytic reaction (up to 91%).

Copper complexes are synthesized and evaluated as new photoredox catalysts/photoinitiators.

This work reveals the preponderance of an intramolecular metal chelation phenomenon in a controlled radical polymerization system involving the reversible trapping of the radical chains by a cobalt complex bis(acetylacetonato)cobalt(II). The cobalt-mediated radical polymerization (CMRP) of a series of N-vinyl amides was considered with the aim of studying the effect of the cobalt chelation by the amide moiety of the last monomer unit of the chain. The latter reinforces the cobalt-polymer bond in the order N-vinylpyrrolidone