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| 2. |
- Schroter, D, et al.
(författare)
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Ecosystem service supply and vulnerability to global change in Europe
- 2005
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 310:5752, s. 1333-1337
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Tidskriftsartikel (refereegranskat)abstract
- Global change will alter the supply of ecosystem services that are vital for human well-being. To investigate ecosystem service supply during the 21st century, we used a range of ecosystem models and scenarios of climate and land-use change to conduct a Europe-wide assessment. Large changes in climate and land use typically resulted in large changes in ecosystem service supply. Some of these trends may be positive (for example, increases in forest area and productivity) or offer opportunities (for example, "surplus land" for agricultural extensification and bioenergy production). However, many changes increase vulnerability as a result of a decreasing supply of ecosystem services (for example, declining soil fertility, declining water availability, increasing risk of forest fires), especially in the Mediterranean and mountain regions.
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| 3. |
- Huber, Stefan M., et al.
(författare)
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Generating Cu-II-oxyl/Cu-III-oxo species from Cu-I-alpha-ketocarboxylate complexes and O-2 : in silico studies on ligand effects and C-H-activation reactivity.
- 2009
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 15:19, s. 4886-4895
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Tidskriftsartikel (refereegranskat)abstract
- A mechanism for the oxygenation of Cu-I complexes with alpha-keto-carboxylate ligands that is based on a combination of density functional theory and multireference second-order perturbation theory (CASSCF/CASPT2) calculations is elaborated. The reaction proceeds in a manner largely analogous to those of similar Fe-II-alpha-ketocarboxylate systems, that is, by initial attack of a coordinated oxygen molecule on a ketocarboxylate ligand with concomitant decarboxylation. Subsequently, two reactive intermediates may be generated, a Cu-peracid structure and a [CuO](+) species, both of which are capable of oxidizing a phenyl ring component of the supporting ligand. Hydroxylation by the [CuO](+) species is predicted to proceed with a smaller activation free energy. The effects of electronic and steric variations on the oxygenation mechanisms were studied by introducing substituents at several positions of the ligand backbone and by investigating various N-donor ligands. In general, more electron donation by the N-donor ligand leads to increased stabilization of the more Cu-II/Cu-III-like intermediates (oxygen adducts and [CuO](+) species) relative to the more Cu-I-like peracid intermediate. For all ligands investigated the [CuO](+) intermediates are best described as Cu-II-O center dot(-) species with triplet ground states. The reactivity of these compounds in C-H abstraction reactions decreases with more electron-donating N-donor ligands, which also increase the Cu-O bond strength, although the Cu-O bond is generally predicted to be rather weak (with a bond order of about 0.5). A comparison of several methods to obtain singlet energies for the reaction intermediates indicates that multireference second-order perturbation theory is likely more accurate for the initial oxygen adducts, but not necessarily for subsequent reaction intermediates.
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| 4. |
- Huber, Stefan M., et al.
(författare)
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What Active Space Adequately Describes Oxygen Activation by a Late Transition Metal? : CASPT2 and RASPT2 Applied to Intermediates from the Reaction of O-2 with a Cu(I)-alpha-Ketocarboxylate
- 2009
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 5:11, s. 2967-2976
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Tidskriftsartikel (refereegranskat)abstract
- Multiconfigurational second-order perturbation theory calculations based on a complete active space reference wave function (CASPT2), employing active spaces of increasing size, are well converged at the level of 12 electrons in 12 orbitals for the singlet-triplet state-energy splittings of three supported copper-dioxygen and two supported copper-oxo complexes. Corresponding calculations using the restricted active space approach (RASPT2) offer similar accuracy with a significantly reduced computational overhead provided an inner (2,2) complete active space is included in the overall RAS space in order to account for strong biradical character in most of the compounds. The effects of the different active space choices and the outer RAS space excitations are examined, and conclusions are drawn with respect to the general applicability of the RASPT2 protocol.
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