Template effects are at the origin of supramolecular chemistry, but the behavior of folded molecules is a relatively new undertaking. Water-soluble cavitand hosts bind hydrocarbons through hydrophobic effects and force long-chain guests into folded conformations. This brings their ends closer together, and sites that were remote in solution become neighbors in the confined space and affect each other's reactivity. Amphiphilic guests fold in the cavitand to bury hydrophobic surfaces and expose the hydrophilic surfaces to the bulk solution. This arrangement leads to product distributions in monofunctionalization reactions that are significantly altered from the statistically determined outcomes in solution. The cavitand also acts as a template for macrocyclic processes involving direct reaction of the guests' ends. We propose applying the effects of folding in cavitands to truly remote functionalization reactions and provide access to molecules that cannot be made by conventional means.

Polymerizable deep eutectic solvent-based mechanically strong and ultra-stretchable conductive elastomers were reported.

Activation of dinitrogen (N2) by well-defined metal hydrides is of much interest and importance, but studies in this area have remained limited to date. We report here N2 activation and hydrogenation by C5Me4SiMe3-ligated di- and trinuclear chromium polyhydride complexes. Hydrogenolysis of [Cp′Cr­(μ-Me)2CrCp′] (Cp′ = C5Me4SiMe3) (1) with H2 in a dilute hexane solution under N2-free conditions affords the dichromium dihydride complex [Cp′Cr­(μ-H)2CrCp′] (2), while hydrogenolysis of 1 in a concentrated solution or without solvent provides the trinuclear chromium tetrahydride complex [(Cp′Cr)3(μ3-H)­(μ-H)3] (3). When the reaction is carried out in the presence of N2 in a dilute hexane solution, the tetranuclear diimide/dihydride complex [(Cp′Cr)4(μ3-NH)2(μ3-H)2] (4) is formed via N–N bond cleavage and N–H bond formation. The reaction of 2 with N2 at room temperature gives the tetranuclear imide/nitride/dihydride complex [(Cp′Cr)3(C5Me3(CH2)­SiMe3)­Cr­(μ3-NH)­(μ3-N)­(μ-H)2] (5) via N2 cleavage and hydrogenation and C–H bond activation of a Cp methyl group. At –30 °C, the reaction of 2 with N2 affords the dinitride intermediate [(Cp′Cr)4(μ3-N)2(μ3-H)2] (6), which is quantitatively transformed to 5 at room temperature. Complex 5 reversibly converts to the stereoisomer 5′. The hydrogenation of a mixture of 5 and 5′ with H2 affords 4. The reaction of 3 with N2 proceeds at 100 °C to afford [(Cp′Cr)3(μ3-NH)2] (7). This transformation has also been investigated by DFT calculations. Both experimental and computational studies suggest that N2 incorporation into the chromium hydride cluster is involved in the rate-determining step. This work represents the first example of N2 cleavage and hydrogenation by well-defined chromium hydride complexes.

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The activation and functionalization of dinitrogen (N 2 ) with carbon dioxide (CO 2 ) are of great interest and importance but highly challenging. We report here for the first time the reaction of N 2 with CO 2 in a dititanium dihydride framework, which leads to N−C bond formation and N−N and C−O bond cleavage. Exposure of a dinitrogen dititanium hydride complex {[( acri PNP)Ti] 2 (μ 2 -η 1 :η 2 -N 2 )(μ 2 -H) 2 } (1) ( acri PNP = 4,5bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide) to a CO 2 atmosphere at room temperature rapidly yielded a nitrido/N,N-When the reaction of 1 with CO 2 (1 atm) was carried out at −50 °C, complex 2 was selectively formed in 82% yield within 5 min. Heating 2 at 80 °C under 1 atm CO 2 for 30 min afforded 3 in 67% yield. When 1 was allowed to react with 1.5 equiv of CO 2 at room temperature, an isocyanato/nitrido/oxo complex {[( acri PNP)Ti] 2 (NCO)(μ 2 -N)(μ 2 -O)} (4) was exclusively formed in 89% yield within 5 min. The reaction of 4 with CO 2 at room temperature almost quantitatively yielded the dioxo/diisocyanato complex 3 within 5 min. The mechanistic details were clarified by the 15 N-and 13 C-labeled experiments and density functional theory (DFT) calculations, providing unprecedented insights into the reaction of N 2 with CO 2 . A titanium-mediated cycle for the synthesis of trimethylsilyl isocyanate Me 3 SiNCO from N 2 , CO 2 , and Me 3 SiCl using H 2 as a reducing agent was also established.

The traditional end-to-end cyclization of long-chain linear precursors is difficult and often unpredictable because the unfavorable entropy of macrocyclic closure allows undesired intermolecular reactions to compete. Here, we apply cavitands to the selective intramolecular aldol/dehydration reaction of long-chain α,ω-dialdehydes in aqueous solution. Hydrophobic forces drive the dialdehydes into the cavitands in folded conformations and favor macrocyclization reactions over intermolecular reactions observed in bulk solution. The macrocyclic aldol reaction products are isolated in good yields (30−85%) over a wide range (11 to 17membered rings). Unlike conventional templates that become guests inside their assembled hosts, cavitands reverse the roles and resemble the situation in biological catalysisthe templates are hosts for guests undergoing the assisted reaction processes.

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The continuous-wave (cw) laser properties of an efficient diode-pumped Nd:GdVO 4 crystal operating at 1.06 µm formed with a simple flat-flat cavity have been studied. With the incident pump power of 25 W, an output power of 15.6 W was obtained, with the optical conversion efficiency of 62.4% and the maximum slop efficiency of 71.3%.