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Two five‐coordinate mononuclear DyIII single‐molecule magnets [(TrapenTMS)Dy(L)] (Trapen=tris(2‐aminobenzyl) amine; TMS=SiMe3; L=OPMe31, OPEt32) have been synthesized by the reaction of [(TrapenTMS)Dy(THF)] and OPMe3, OPEt3, respectively. The molecular structures of 1 and 2 were fully established by single crystal X‐ray diffraction. The centre DyIII ions of both complexes exhibit distorted triangular bipyramid geometries, varying with different neutral ligands L on the apex. The TrapenTMS ligand forms the pyramid base of the trigonal bipyramid. Subtle structural modifications of the axial O‐ligand terminal substituent result in different dynamic magnetic behaviors. Magnetic data analysis reveals that 1 and 2 exhibit the characteristic behavior of SMM without a dc field, accompanying an unambiguous quantum tunneling of the magnetization. Field‐induced slow magnetic relaxation was observed for 1 and 2 under an applied bias dc field of 1000 Oe, the relaxation energy barriers are 107 K and 88 K for 1 and 2, respectively. We have investigated the differences in magnetism and magnetic anisotropy between the two complexes by ab initio calculations. [ABSTRACT FROM AUTHOR]

A detailed effects of catalyst X (X = H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4) on the HO4H → O3 + H2O reaction have been investigated by using quantum chemical calculations and canonical vibrational transition state theory with small curvature tunnelling. The calculated results show that (H2O)2-catalysed reactions much faster than H2O-catalysed one because of the former bimolecular rate constant larger by 2.6–25.9 times than that of the latter one. In addition, the basic H2O···NH3 catalyst was found to be a better than the neutral catalyst of (H2O)2. However it is marginally less efficient than the acidic catalysts of HCOOH, and H2SO4. The effective rate constant (k't) in the presence of catalyst X have been assessed. It was found from k't that H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K at 0 km altitude. However, compared with the rate constant of HO4H → H2O + O3 reaction, the keff values for H2O catalysed reaction are smaller by 1–2 orders of magnitude, indicating that the catalytic effect of H2O makes a negligible contribution to the gas phase reaction of HO4H → O3 + H2O. Highlights A detailed effects of catalyst of H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4 on the HO4H → O3 + H2O reaction has been performed. From energetic viewpoint, H2SO4 exerts the strongest catalytic role in HO4H → O3 + H2O reaction as compared with the other catalysts. At 0 km altitude H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K. HO4H → H2O + O3 reaction with H2O cannot be compete with the reaction without catalyst, due to the fact that the effective rate constants in the presence of H2O are smaller. [ABSTRACT FROM AUTHOR]

The hydrolysis of CH 2 OO is not only a dominant sink for the CH 2 OO intermediate in the atmosphere but also a key process in the formation of aerosols. Herein, the reaction mechanism and kinetics for the hydrolysis of CH 2 OO catalyzed by the precursors of atmospheric aerosols, including H 2 SO 4 , H 2 SO 4 ···H 2 O, and (H 2 SO 4 ) 2 , have been studied theoretically at the CCSD(T)-F12a/cc-pVDZ-F12//B3LYP/6-311+G(2 df ,2 pd ) level. The calculated results show that the three catalysts decrease the energy barrier by over 10.3 kcal·mol -1 ; at the same time, the product formation of HOCH 2 OOH is more strongly bonded to the three catalysts than to the reactants CH 2 OO and H 2 O, revealing that small clusters of sulfuric acid promote the hydrolysis of CH 2 OO both kinetically and thermodynamically. Kinetic simulations show that the H 2 SO 4 -assisted reaction is more favorable than the H 2 SO 4 ···H 2 O- (the pseudo-first-order rate constant being 27.9-11.5 times larger) and (H 2 SO 4 ) 2 - (between 2.8 × 10 4 and 3.4 × 10 5 times larger) catalyzed reactions. Additionally, due to relatively lower concentration of H 2 SO 4 , the hydrolysis of CH 2 OO with H 2 SO 4 cannot compete with the CH 2 OO + H 2 O or (H 2 O) 2 reaction within the temperature range of 280-320 K, since its pseudo-first-order rate ratio is smaller by 4-7 or 6-8 orders of magnitude, respectively. However, the present results provide a good example of how small clusters of sulfuric acid catalyze the hydrolysis of an important atmospheric species.

The H 2 O 2 + HO → HO 2 + H 2 O reaction is an important reservoir for both radicals of HO and HO 2 catalyzing the destruction of O 3 . Here, this reaction assisted by NH 3 and HCOOH catalysts was explored using the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH 3 and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH 3 (10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3-5 and 2-4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH 3 and HCOOH than H 2 O which indicates the positive water effect under atmospheric conditions. Although NH 3 and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO 2 catalyzing the destruction of O 3 , the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)