Dinuclear triple-helicate complexes of the formula [Fe2L3](BF4)4·solv (solv = CH3CN, CHCl3, H2O) have been synthesised and structurally characterised. The bis-bidentate ligands, L, present either strong-field 2-pyridylimine (1) or weaker-field 2-imidazolylimine (2) and 4-imidazolylimine (3) coordination spheres about Fe(ii) centres in an octahedral geometry. Whereas 1 is pervasively diamagnetic, spin crossover (SCO) behaviour is observed in 2 and 3 and has been studied using variable-temperature structural, UV-visible spectroscopic, magnetic and photo-magnetic techniques. Variable-temperature (1.8-400 K) magnetic-susceptibility measurements reveal the T1/2 values of 2 and 3 to be strongly dependent upon the solvent and degree of solvation. Photomagnetic studies at 10 K under white-light irradiation revealed an inefficient photo-induced SCO in 2, but full switching in 3.

All transitions in the experimentally designated and numbered Q, B, and N bands (< 4.8 eV) of the electronic absorption spectrum of zinc phthalocyanine (ZnPc) are assigned on the basis of one-to-one agreement between calculated and experimentally observed transition energies and oscillator strengths. Each band in this range of the spectrum represents a ligand-based transition that originates from a combination of occupied orbitals and terminates in the lowest unoccupied molecular orbital (LUMO, 6e(g)(pi)). Transition energies in the L and C regions (4.8-6.5 eV) are harder to capture quantitatively, due to the partial Rydberg character of some of the excited states, and so are tentatively assigned here. Most transitions in this range correspond to excitations from the HOMO or lower-energy orbitals to pi orbitals above the LUMO.

Multireference electronic structure methods are used to assign ground state electronic configurations for a series of metallophthalocyanines. Ligand orbital occupancies remain constant across the period and are consistent with a formal 2– charge on the ligand. The d electron configurations of some metallophthalocyanines are straightforward and can be unambiguously assigned, (d xy ) 2 (d xz ,d yz ) 2,2 ( [Formula: see text]) 2 ([Formula: see text]) n , with n = 2, 1, 0, respectively, for ZnPc, CuPc, and NiPc. Controversies over ground state electronic structure assignments for other metallophthalocyanines arise due to multiple complicating factors: accidental near-degeneracies, environmental effects, and different ligand field models used in interpreting experimental spectra. We demonstrate that explicit ligand field models provide more reliable and consistent interpretations of experimental data than implicit, parameterized alternatives. On this basis, we assign gas-phase electronic ground states for MnPc, (d xy ) 2 (d xz ,d yz ) 1,1 ([Formula: see text]) 1 and CoPc, (d xy ) 2 (d xz ,d yz ) 2,2 ([Formula: see text]) 1 , and show that the ground state of FePc cannot be resolved to a single state, with two near-degenerate states that are likely spin-orbit coupled: (d xy ) 2 (d xz ,d yz ) 1,1 ( [Formula: see text]) 2 and (d xy ) 2 (d xz ,d yz ) 2,1 ([Formula: see text]) 1 . Remaining differences between computational predictions and experimental observations are small and may be ascribed primarily to environmental effects but are also partly due to incomplete modelling of electron correlation.

The performance of catalysts made using Au101(PPh3)21Cl5 nanoparticles immobilized on Norit® activated carbon powder was investigated in the aerobic oxidation of benzyl alcohol in basic methanolic solution. The catalyst was activated by washing with hot toluene, followed by heat treatment in static air at 100 °C for 3 h. Effects of key parameters, such as the amounts of benzyl alcohol and base (K2CO3), reaction temperature, reaction time and solvent were explored, as was the longer-term stability of the catalyst during storage. The product mixtures were analysed by high-performance liquid chromatography. Under relatively mild conditions [p(O2) = 5 bar and T = 80 °C], catalysts with a loading of 1.0 wt% give up to 100 % conversion of benzyl alcohol in the presence of equimolar K2CO3 over 24 h. The main products are methyl benzoate and benzoic acid, with selectivities that vary with reaction conditions. Comparison with results obtained with ethanol solvent support a reaction mechanism involving benzaldehyde as an intermediate.

200 mm diameter wafer-scale fabrication, metrology, and optical modeling results are reviewed for surface plasmon resonance (SPR) sensors based on 2-D metallic nano-dome and nano-hole arrays (NHA's) as well as 1-D photonic crystal sensors based on a leaky-waveguide mode resonance effect, with potential applications in label free sensing, surface enhanced Raman spectroscopy (SERS), and surface-enhanced fluorescence spectroscopy (SEFS). Potential markets include micro-arrays for medical diagnostics, forensic testing, environmental monitoring, and food safety. 1-D and 2-D nanostructures were fabricated on glass, fused silica, and silicon wafers using optical lithography and semiconductor processing techniques. Wafer-scale optical metrology results are compared to FDTD modeling and presented along with application-based performance results, including label-free plasmonic and photonic crystal sensing of both surface binding kinetics and bulk refractive index changes. In addition, SEFS and SERS results are presented for 1-D photonic crystal and 2-D metallic nano-array structures. Normal incidence transmittance results for a 550 nm pitch NHA showed good bulk refractive index sensitivity, however an intensity-based design with 665 nm pitch was chosen for use as a compact, label-free sensor at both 650 and 632.8 nm wavelengths. The optimized NHA sensor gives an SPR shift of about 480 nm per refractive index unit when detecting a series of 0-40% glucose solutions, but according to modeling shows about 10 times greater surface sensitivity when operating at 532 nm. Narrow-band photonic crystal resonance sensors showed quality factors over 200, with reasonable wafer-uniformity in terms of both resonance position and peak height.

The photocatalytic decolorization and degradation of an anthraquinone-based reactive dye, C.I. Reactive Blue 19, was carried out in laboratory-scale experiments with the systematic variation of several operational parameters, including electron acceptor (hydrogen peroxide) concentration, initial pH, use of buffer solution, aeration, and the specific chemical nature of the buffer solution. Photodegradation was performed under simulated natural light, and conditions were chosen to mimic those found in industry. Mineralization and decolorization were monitored by UV-vis spectroscopy and total organic carbon analysis, and kinetics were modelled using an in-series first-order combination mechanism. Reaction products were examined and monitored by high-resolution mass spectrometry. Under the conditions explored, the reaction rate was found to depend not only on pH and electron acceptor concentration, but also on the specific chemical nature of the buffer used.

We report here the host-guest behaviour of two isoelectronic [Fe4L4](8+) tetrahedral cages that differ only in the nature of their face-capping ligand and possess either triazine (L1) or benzene (L2) cores. Crystallography reveals these hosts to be flexible and adaptable, while NMR spectroscopy shows them to be selective and discriminating in their host-guest behaviour.

The selectivity of supported gold catalysts in solvent- and radical initiator-free aerobic oxidation of cyclohexene was tuned by either WO3 or MIL-101.

It is well understood by most chemistry students at advanced undergraduate levels that chemical reactions generally follow the Arrhenius law of temperature dependence with positive activation energies, proceeding faster at elevated temperatures. It is much less widely known that the rates of some Arrhenius-compliant reactions are retarded by increasing the temperature and are therefore associated with negative activation energies. The few readily accessible explanations of this phenomenon are rather cursory and limited to enthalpic considerations relating to the relative activation energies and thermicities of the component elementary steps of the process. However, these explanations are incomplete and consequently counterintuitive. Here we provide the required augmentation via entropic considerations.

Recently, it was shown that of the ozone‐depleting substances currently emitted, N2O emissions (the primary source of stratospheric NOx) dominate, and are likely to do so throughout the 21st century. To investigate the links between N2O and NOx concentrations, and the effects of NOxon ozone in a changing climate, the evolution of stratospheric ozone from 1960 to 2100 was simulated using the NIWA‐SOCOL chemistry‐climate model. The yield of NOx from N2O is reduced due to stratospheric cooling and a strengthening of the Brewer‐Dobson circulation. After accounting for the reduced NOx yield, additional weakening of the primary NOxcycle is attributed to reduced availability of atomic oxygen, due to a) stratospheric cooling decreasing the atomic oxygen/ozone ratio, and b) enhanced rates of chlorine‐catalyzed ozone loss cycles around 2000 and enhanced rates of HOx‐induced ozone depletion. Our results suggest that the effects of N2O on ozone depend on both the radiative and chemical environment of the upper stratosphere, specifically CO2‐induced cooling of the stratosphere and elevated CH4 emissions which enhance HOx‐induced ozone loss and remove the availability of atomic oxygen to participate in NOx ozone loss cycles.

The sensitivity of stratospheric ozone changes through the 21st century to N2O and CH4 L. E. Revell, G. E. Bodeker, P. E. Huck, B. E. Williamson, and E. Rozanov National Institute of Water and Atmospheric Research, Christchurch, New Zealand Department of Chemistry, University of Canterbury, New Zealand Bodeker Scientific, Alexandra, New Zealand Physical-Meteorological Observatory Davos/World Radiation Center, Davos, Switzerland Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland

Abstract. Through the 21st century, anthropogenic emissions of the greenhouse gases N2O and CH4 are projected to increase, thus increasing their atmospheric concentrations. Consequently, reactive nitrogen species produced from N2O and reactive hydrogen species produced from CH4 are expected to play an increasingly important role in determining stratospheric ozone concentrations. Eight chemistry-climate model simulations were performed to assess the sensitivity of stratospheric ozone to different emissions scenarios for N2O and CH4. Increases in reactive nitrogen-mediated ozone loss resulting from increasing N2O concentrations lead to a decrease in global-mean total column ozone. Increasing CH4 concentrations increase the rate of reactive hydrogen-mediated ozone loss in the upper stratosphere. Overall however, increasing CH4 concentrations lead to an increase in global-mean total column ozone. Stratospheric column ozone over the 21st century exhibits a near-linear response to changes in N2O and CH4 surface concentrations, which provides a simple parameterization for the ozone response to changes in these gases.

Through the 21st century, anthropogenic emissions of the greenhouse gases N2O and CH4 are projected to increase, thus increasing their atmospheric concentrations. Consequently, reactive nitrogen species produced from N2O and reactive hydrogen species produced from CH4 are expected to play an increasingly important role in determining stratospheric ozone concentrations. Eight chemistry-climate model simulations were performed to assess the sensitivity of stratospheric ozone to different emissions scenarios for N2O and CH4. Global-mean total column ozone increases through the 21st century in all eight simulations as a result of CO2-induced stratospheric cooling and decreasing stratospheric halogen concentrations. Larger N2O concentrations were associated with smaller ozone increases, due to reactive nitrogen-mediated ozone destruction. In the simulation with the largest N2O increase, global-mean total column ozone increased by 4.3 DU through the 21st century, compared with 10.0 DU in the simulation with the smallest N2O increase. In contrast, larger CH4 concentrations were associated with larger ozone increases; global-mean total column ozone increased by 16.7 DU through the 21st century in the simulation with the largest CH4 concentrations and by 4.4 DU in the simulation with the lowest CH4 concentrations. CH4 leads to ozone loss in the upper and lower stratosphere by increasing the rate of reactive hydrogen-mediated ozone loss cycles, however in the lower stratosphere and troposphere, CH4 leads to ozone increases due to photochemical smog-type chemistry. In addition to this mechanism, total column ozone increases due to H2O-induced cooling of the strato-sphere, and slowing of the chlorine-catalyzed ozone loss cycles due to an increased rate of the CH4 + Cl reaction. Stratospheric column ozone through the 21st century exhibits a near-linear response to changes in N2O and CH4 surface concentrations, which provides a simple parameterization for the ozone response to changes in these gases.

Biofuels are becoming increasingly popular sources of renewable energy as economic pressures and environmental consequences encourage the use of alternatives to fossil fuels. However, growing crops destined for use as biofuels incurs large N2O emissions associated with the use of nitrogen‐based fertilizers. Besides being a greenhouse gas, N2O is also the primary source of stratospheric NOx (NO + NO2) which leads to stratospheric ozone depletion. In this paper, the potential effects on the ozone layer of a large‐scale shift away from fossil fuel use to biofuels consumption over the 21st century are examined. Under such a scenario, global‐mean column ozone decreases by 2.6 DU between 2010 and 2100 in contrast to a 0.7 DU decrease under a control simulation (the IPCC SRES B1 scenario for greenhouse gases) and a 9.1 DU increase under the more commonly used SRES A1B scenario. Two factors cause the decrease in ozone in the biofuels simulation: 1) large N2O emissions lead to faster rates of the ozone‐depleting NOx cycles and; 2) reduced CO2 emissions (due to less fossil fuel burning) lead to relatively less stratospheric cooling over the 21st century, which decreases ozone abundances. Reducing CO2 emissions while neglecting to reduce N2O emissions could therefore be damaging to the ozone layer.