Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts

[EN] The potential of oxide-supported rhodium single atom catalysts (SACs) for heterogeneous hydroformylation was investigated both theoretically and experimentally. Using high-level domain-based local-pair natural orbital coupled cluster singles doubles with perturbative triples contribution (DLPNO-CCSD(T)) calculations, both stability and catalytic activity were investigated for Rh single atoms on different oxide surfaces. Atomically dispersed, supported Rh catalysts were synthesized on MgO and CeO2. While the CeO2-supported rhodium catalyst is found to be highly active, this is not the case for MgO, most likely due to increased confinement, as determined by extended X-ray absorption fine structure spectroscopy (EXAFS), that diminishes the reactivity of Rh complexes on MgO. This agrees well with our computational investigation, where we find that rhodium carbonyl hydride complexes on flat oxide surfaces such as CeO2(111) have catalytic activities comparable to those of molecular complexes. For a step edge on a MgO(301) surface, however, calculations show a significantly reduced catalytic activity. At the same time, calculations predict that stronger adsorption at the higher coordinated adsorption site leads to a more stable catalyst. Keeping the balance between stability and activity appears to be the main challenge for oxide supported Rh hydroformylation catalysts. In addition to the chemical bonding between rhodium complex and support, the confinement experienced by the active site plays an important role for the catalytic activity.X-ray absorption experiments were performed at the ALBA Synchrotron Light Source (Spain), experiment 2019023278. Beamline scientists L. Simonelli and C. Marini are gratefully acknowledged for their contribution to beam setup. E. Andrés, E. Martínez-Monje, I. López, and M. García-Farpón (ITQ) are acknowledged for their assistance with XAS data acquisition. J. Ternedien (MPI-KOFO) is acknowledged for the performance of XRD experiments. N. Pfänder (MPI-CEC) is acknowledged for his contribution to STEM characterization. The authors acknowledge support by the state of Baden-Württemberg through bwHPC (bwUnicluster and JUSTUS, RV bw17D01). The authors gratefully acknowledge support by the GRK 2450. Financial support from the Helmholtz Association is also gratefully acknowledged. The experimental work received funding from the Max Planck Society and the Spanish Ministry of Science, Innovation and Universities (projects SEV-2016-0683 and RTI2018-096399-A-I00). B.B.S. acknowledges the Alexander von Humboldt Foundation for a postdoctoral scholarship.Amsler, J.; Sarma, BB.; Agostini, G.; Prieto González, G.; Plessow, P.; Studt, F. (2020). Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts. Journal of the American Chemical Society. 142(11):5087-5096. https://doi.org/10.1021/jacs.9b12171S5087509614211Franke, R., Selent, D., & Börner, A. (2012). Applied Hydroformylation. Chemical Reviews, 112(11), 5675-5732. doi:10.1021/cr3001803Serna, P., Yardimci, D., Kistler, J. D., & Gates, B. C. (2014). Formation of supported rhodium clusters from mononuclear rhodium complexes controlled by the support and ligands on rhodium. Phys. Chem. Chem. Phys., 16(3), 1262-1270. doi:10.1039/c3cp53057dGuan, E., & Gates, B. C. (2017). Stable Rhodium Pair Sites on MgO: Influence of Ligands and Rhodium Nuclearity on Catalysis of Ethylene Hydrogenation and H–D Exchange in the Reaction of H2 with D2. ACS Catalysis, 8(1), 482-487. doi:10.1021/acscatal.7b03549Dossi, C., Fusi, A., Garlaschelli, L., Roberto, D., Ugo, R., & Psaro, R. (1991). Ethylene hydroformylation with the silica-supported K2[Rh12(CO)30] cluster: evidence for vapor-phase cluster catalysis. Catalysis Letters, 11(3-6), 335-339. doi:10.1007/bf00764325Ehresmann, J. O., Kletnieks, P. W., Liang, A., Bhirud, V. A., Bagatchenko, O. P., Lee, E. J., … Haw, J. F. (2006). Evidence from NMR and EXAFS Studies of a Dynamically Uniform Mononuclear Single-Site Zeolite-Supported Rhodium Catalyst. Angewandte Chemie International Edition, 45(4), 574-576. doi:10.1002/anie.200502864Sun, Q., Dai, Z., Liu, X., Sheng, N., Deng, F., Meng, X., & Xiao, F.-S. (2015). Highly Efficient Heterogeneous Hydroformylation over Rh-Metalated Porous Organic Polymers: Synergistic Effect of High Ligand Concentration and Flexible Framework. Journal of the American Chemical Society, 137(15), 5204-5209. doi:10.1021/jacs.5b02122De Munck, N. A., Verbruggen, M. W., & Scholten, J. J. F. (1981). Gas phase hydroformylation of propylene with porous resin anchored rhodium complexes part I. Methods of catalyst preparation and characterization. Journal of Molecular Catalysis, 10(3), 313-330. doi:10.1016/0304-5102(81)85052-3Lang, R., Li, T., Matsumura, D., Miao, S., Ren, Y., Cui, Y.-T., … Zhang, T. (2016). Hydroformylation of Olefins by a Rhodium Single-Atom Catalyst with Activity Comparable to RhCl(PPh3)3. Angewandte Chemie International Edition, 55(52), 16054-16058. doi:10.1002/anie.201607885Yang, X.-F., Wang, A., Qiao, B., Li, J., Liu, J., & Zhang, T. (2013). Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis. Accounts of Chemical Research, 46(8), 1740-1748. doi:10.1021/ar300361mPaolucci, C., Khurana, I., Parekh, A. A., Li, S., Shih, A. J., Li, H., … Gounder, R. (2017). Dynamic multinuclear sites formed by mobilized copper ions in NO x selective catalytic reduction. Science, 357(6354), 898-903. doi:10.1126/science.aan5630Jangjou, Y., Do, Q., Gu, Y., Lim, L.-G., Sun, H., Wang, D., … Epling, W. S. (2018). Nature of Cu Active Centers in Cu-SSZ-13 and Their Responses to SO2 Exposure. ACS Catalysis, 8(2), 1325-1337. doi:10.1021/acscatal.7b03095Wang, L., Zhang, W., Wang, S., Gao, Z., Luo, Z., Wang, X., … Zeng, J. (2016). Atomic-level insights in optimizing reaction paths for hydroformylation reaction over Rh/CoO single-atom catalyst. Nature Communications, 7(1). doi:10.1038/ncomms14036Li, T., Chen, F., Lang, R., Wang, H., Su, Y., Qiao, B., … Zhang, T. (2020). Styrene Hydroformylation with In Situ Hydrogen: Regioselectivity Control by Coupling with the Low‐Temperature Water–Gas Shift Reaction. Angewandte Chemie International Edition, 59(19), 7430-7434. doi:10.1002/anie.202000998Heck, R. F., & Breslow, D. S. (1961). The Reaction of Cobalt Hydrotetracarbonyl with Olefins. Journal of the American Chemical Society, 83(19), 4023-4027. doi:10.1021/ja01480a017Van Leeuwen, P. W. N. M., & Claver, C. (Eds.). (2002). Rhodium Catalyzed Hydroformylation. Catalysis by Metal Complexes. doi:10.1007/0-306-46947-2Van Rooy, A. (1996). Rhodium-catalysed hydroformylation of branched 1-alkenes; bulky phosphite vs. triphenylphosphine as modifying ligand. Journal of Organometallic Chemistry, 507(1-2), 69-73. doi:10.1016/0022-328x(95)05748-eSparta, M., Børve, K. J., & Jensen, V. R. (2007). Activity of Rhodium-Catalyzed Hydroformylation:  Added Insight and Predictions from Theory. Journal of the American Chemical Society, 129(27), 8487-8499. doi:10.1021/ja070395nGellrich, U., Himmel, D., Meuwly, M., & Breit, B. (2013). Realistic Energy Surfaces for Real-World Systems: An IMOMO CCSD(T):DFT Scheme for Rhodium-Catalyzed Hydroformylation with the 6-DPPon Ligand. Chemistry - A European Journal, 19(48), 16272-16281. doi:10.1002/chem.201302132Kumar, M., Chaudhari, R. V., Subramaniam, B., & Jackson, T. A. (2014). Ligand Effects on the Regioselectivity of Rhodium-Catalyzed Hydroformylation: Density Functional Calculations Illuminate the Role of Long-Range Noncovalent Interactions. Organometallics, 33(16), 4183-4191. doi:10.1021/om500196gJiao, Y., Torne, M. S., Gracia, J., Niemantsverdriet, J. W. (Hans), & van Leeuwen, P. W. N. M. (2017). Ligand effects in rhodium-catalyzed hydroformylation with bisphosphines: steric or electronic? Catalysis Science & Technology, 7(6), 1404-1414. doi:10.1039/c6cy01990kSchmidt, S., Deglmann, P., & Hofmann, P. (2014). Density Functional Investigations of the Rh-Catalyzed Hydroformylation of 1,3-Butadiene with Bisphosphite Ligands. ACS Catalysis, 4(10), 3593-3604. doi:10.1021/cs500718vJacobs, I., de Bruin, B., & Reek, J. N. H. (2015). Comparison of the Full Catalytic Cycle of Hydroformylation Mediated by Mono- and Bis-Ligated Triphenylphosphine-Rhodium Complexes by Using DFT Calculations. ChemCatChem, 7(11), 1708-1718. doi:10.1002/cctc.201500087Kégl, T. (2015). Computational aspects of hydroformylation. RSC Advances, 5(6), 4304-4327. doi:10.1039/c4ra13121eWodrich, M. D., Busch, M., & Corminboeuf, C. (2016). Accessing and predicting the kinetic profiles of homogeneous catalysts from volcano plots. Chemical Science, 7(9), 5723-5735. doi:10.1039/c6sc01660jLiu, J., Bunes, B. R., Zang, L., & Wang, C. (2017). Supported single-atom catalysts: synthesis, characterization, properties, and applications. Environmental Chemistry Letters, 16(2), 477-505. doi:10.1007/s10311-017-0679-2Kwon, Y., Kim, T. Y., Kwon, G., Yi, J., & Lee, H. (2017). Selective Activation of Methane on Single-Atom Catalyst of Rhodium Dispersed on Zirconia for Direct Conversion. Journal of the American Chemical Society, 139(48), 17694-17699. doi:10.1021/jacs.7b11010Sarma, B. B., Kim, J., Amsler, J., Agostini, G., Weidenthaler, C., Pfänder, N., … Prieto, G. (2020). One‐Pot Cooperation of Single‐Atom Rh and Ru Solid Catalysts for a Selective Tandem Olefin Isomerization‐Hydrosilylation Process. Angewandte Chemie International Edition, 59(14), 5806-5815. doi:10.1002/anie.201915255Qiao, B., Wang, A., Yang, X., Allard, L. F., Jiang, Z., Cui, Y., … Zhang, T. (2011). Single-atom catalysis of CO oxidation using Pt1/FeOx. Nature Chemistry, 3(8), 634-641. doi:10.1038/nchem.1095Sun, S., Zhang, G., Gauquelin, N., Chen, N., Zhou, J., Yang, S., … Sun, X. (2013). Single-atom Catalysis Using Pt/Graphene Achieved through Atomic Layer Deposition. Scientific Reports, 3(1). doi:10.1038/srep01775Abbet, S., Sanchez, A., Heiz, U., Schneider, W.-D., Ferrari, A. M., Pacchioni, G., & Rösch, N. (2000). Acetylene Cyclotrimerization on Supported Size-Selected Pdn Clusters (1 ≤ n ≤ 30): One Atom Is Enough! Journal of the American Chemical Society, 122(14), 3453-3457. doi:10.1021/ja9922476Lin, J., Wang, A., Qiao, B., Liu, X., Yang, X., Wang, X., … Zhang, T. (2013). Remarkable Performance of Ir1/FeOx Single-Atom Catalyst in Water Gas Shift Reaction. Journal of the American Chemical Society, 135(41), 15314-15317. doi:10.1021/ja408574mGu, X.-K., Qiao, B., Huang, C.-Q., Ding, W.-C., Sun, K., Zhan, E., … Li, W.-X. (2014). Supported Single Pt1/Au1 Atoms for Methanol Steam Reforming. ACS Catalysis, 4(11), 3886-3890. doi:10.1021/cs500740uJones, J., Xiong, H., DeLaRiva, A. T., Peterson, E. J., Pham, H., Challa, S. R., … Datye, A. K. (2016). Thermally stable single-atom platinum-on-ceria catalysts via atom trapping. Science, 353(6295), 150-154. doi:10.1126/science.aaf8800Fei, H., Dong, J., Arellano-Jiménez, M. J., Ye, G., Dong Kim, N., Samuel, E. L. G., … Tour, J. M. (2015). Atomic cobalt on nitrogen-doped graphene for hydrogen generation. Nature Communications, 6(1). doi:10.1038/ncomms9668Wei, H., Liu, X., Wang, A., Zhang, L., Qiao, B., Yang, X., … Zhang, T. (2014). FeOx-supported platinum single-atom and pseudo-single-atom catalysts for chemoselective hydrogenation of functionalized nitroarenes. Nature Communications, 5(1). doi:10.1038/ncomms6634Wang, X., van Bokhoven, J. A., & Palagin, D. (2020). Atomically dispersed platinum on low index and stepped ceria surfaces: phase diagrams and stability analysis. Physical Chemistry Chemical Physics, 22(1), 28-38. doi:10.1039/c9cp04973hNeitzel, A., Figueroba, A., Lykhach, Y., Skála, T., Vorokhta, M., Tsud, N., … Libuda, J. (2016). Atomically Dispersed Pd, Ni, and Pt Species in Ceria-Based Catalysts: Principal Differences in Stability and Reactivity. The Journal of Physical Chemistry C, 120(18), 9852-9862. doi:10.1021/acs.jpcc.6b02264Tang, Y., Asokan, C., Xu, M., Graham, G. W., Pan, X., Christopher, P., … Sautet, P. (2019). Rh single atoms on TiO2 dynamically respond to reaction conditions by adapting their site. Nature Communications, 10(1). doi:10.1038/s41467-019-12461-6DeRita, L., Resasco, J., Dai, S., Boubnov, A., Thang, H. V., Hoffman, A. S., … Christopher, P. (2019). Structural evolution of atomically dispersed Pt catalysts dictates reactivity. Nature Materials, 18(7), 746-751. doi:10.1038/s41563-019-0349-9Su, Y.-Q., Wang, Y., Liu, J.-X., Filot, I. A. W., Alexopoulos, K., Zhang, L., … Hensen, E. J. M. (2019). Theoretical Approach To Predict the Stability of Supported Single-Atom Catalysts. ACS Catalysis, 9(4), 3289-3297. doi:10.1021/acscatal.9b00252O’Connor, N. J., Jonayat, A. S. M., Janik, M. J., & Senftle, T. P. (2018). Interaction trends between single metal atoms and oxide supports identified with density functional theory and statistical learning. Nature Catalysis, 1(7), 531-539. doi:10.1038/s41929-018-0094-5Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Grimme, S., Antony, J., Ehrlich, S., & Krieg, H. (2010). A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. The Journal of Chemical Physics, 132(15), 154104. doi:10.1063/1.3382344Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Kresse, G., & Furthmüller, J. (1996). Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set. Physical Review B, 54(16), 11169-11186. doi:10.1103/physrevb.54.11169Blöchl, P. E. (1994). Projector augmented-wave method. Physical Review B, 50(24), 17953-17979. doi:10.1103/physrevb.50.17953Anisimov, V. I., Zaanen, J., & Andersen, O. K. (1991). Band theory and Mott insulators: HubbardUinstead of StonerI. Physical Review B, 44(3), 943-954. doi:10.1103/physrevb.44.943Dudarev, S. L., Botton, G. A., Savrasov, S. Y., Humphreys, C. J., & Sutton, A. P. (1998). Electron-energy-loss spectra and the structural stability of nickel oxide:  An LSDA+U study. Physical Review B, 57(3), 1505-1509. doi:10.1103/physrevb.57.1505Song, Y.-L., Yin, L.-L., Zhang, J., Hu, P., Gong, X.-Q., & Lu, G. (2013). A DFT+U study of CO oxidation at CeO2(110) and (111) surfaces with oxygen vacancies. Surface Science, 618, 140-147. doi:10.1016/j.susc.2013.09.001Nolan, M., Grigoleit, S., Sayle, D. C., Parker, S. C., & Watson, G. W. (2005). Density functional theory studies of the structure and electronic structure of pure and defective low index surfaces of ceria. Surface Science, 576(1-3), 217-229. doi:10.1016/j.susc.2004.12.016Huang, M., & Fabris, S. (2008). CO Adsorption and Oxidation on Ceria Surfaces from DFT+U Calculations. The Journal of Physical Chemistry C, 112(23), 8643-8648. doi:10.1021/jp709898rMonkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Plessow, P. N. (2018). Efficient Transition State Optimization of Periodic Structures through Automated Relaxed Potential Energy Surface Scans. Journal of Chemical Theory and Computation, 14(2), 981-990. doi:10.1021/acs.jctc.7b01070Zhao, Y., & Truhlar, D. G. (2007). The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theoretical Chemistry Accounts, 120(1-3), 215-241. doi:10.1007/s00214-007-0310-xStephens, P. J., Devlin, F. J., Chabalowski, C. F., & Frisch, M. J. (1994). Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields. The Journal of Physical Chemistry, 98(45), 11623-11627. doi:10.1021/j100096a001TURBOMOLE, V.7.1 2016, a development of Karlsruhe Institute of Technology, Karlsruhe, 1989–2019, TURBOMOLE GmbH, since 2007; available from http://www.turbomole.com. Turbomole GmbH: 2016.Weigend, F. (2006). Accurate Coulomb-fitting basis sets for H to Rn. Physical Chemistry Chemical Physics, 8(9), 1057. doi:10.1039/b515623hWeigend, F., & Ahlrichs, R. (2005). Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Physical Chemistry Chemical Physics, 7(18), 3297. doi:10.1039/b508541aNeese, F. (2011). The ORCA program system. WIREs Computational Molecular Science, 2(1), 73-78. doi:10.1002/wcms.81Neese, F. (2017). Software update: the ORCA program system, version 4.0. WIREs Computational Molecular Science, 8(1). doi:10.1002/wcms.1327Ekström, U., Visscher, L., Bast, R., Thorvaldsen, A. J., & Ruud, K. (2010). Arbitrary-Order Density Functional Response Theory from Automatic Differentiation. Journal of Chemical Theory and Computation, 6(7), 1971-1980. doi:10.1021/ct100117sAndrae, D., H�u�ermann, U., Dolg, M., Stoll, H., & Preu�, H. (1990). Energy-adjustedab initio pseudopotentials for the second and third row transition elements. Theoretica Chimica Acta, 77(2), 123-141. doi:10.1007/bf01114537Marenich, A. V., Cramer, C. J., & Truhlar, D. G. (2009). Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. The Journal of Physical Chemistry B, 113(18), 6378-6396. doi:10.1021/jp810292nRiplinger, C., Pinski, P., Becker, U., Valeev, E. F., & Neese, F. (2016). Sparse maps—A systematic infrastructure for reduced-scaling electronic structure methods. II. Linear scaling domain based pair natural orbital coupled cluster theory. The Journal of Chemical Physics, 144(2), 024109. doi:10.1063/1.4939030Ugliengo, P., & Damin, A. (2002). Are dispersive forces relevant for CO adsorption on the MgO(001) surface? Chemical Physics Letters, 366(5-6), 683-690. doi:10.1016/s0009-2614(02)01657-3Alessio, M., Usvyat, D., & Sauer, J. (2018). Chemically Accurate Adsorption Energies: CO and H2O on the MgO(001) Surface. Journal of Chemical Theory and Computation, 15(2), 1329-1344. doi:10.1021/acs.jctc.8b01122Utamapanya, S., Klabunde, K. J., & Schlup, J. R. (1991). Nanoscale metal oxide particles/clusters as chemical reagents. Synthesis and properties of ultrahigh surface area magnesium hydroxide and magnesium oxide. Chemistry of Materials, 3(1), 175-181. doi:10.1021/cm00013a036Ravel, B., & Newville, M. (2005). ATHENA,ARTEMIS,HEPHAESTUS: data analysis for X-ray absorption spectroscopy usingIFEFFIT. Journal of Synchrotron Radiation, 12(4), 537-541. doi:10.1107/s0909049505012719Connett, J. E. (1972). Chemical equilibria 5. Measurement of equilibrium constants for the dehydrogenation of propanol by a vapour flow technique. The Journal of Chemical Thermodynamics, 4(2), 233-237. doi:10.1016/0021-9614(72)90061-4Wodrich, M. D., Busch, M., & Corminboeuf, C. (2018). Expedited Screening of Active and Regioselective Catalysts for the Hydroformylation Reaction. Helvetica Chimica Acta, 101(9), e1800107. doi:10.1002/hlca.201800107Goula, G., Botzolaki, G., Osatiashtiani, A., Parlett, C. M. A., Kyriakou, G., Lambert, R. M., & Yentekakis, I. V. (2019). Oxidative Thermal Sintering and Redispersion of Rh Nanoparticles on Supports with High Oxygen Ion Lability. Catalysts, 9(6), 541. doi:10.3390/catal9060541Lazzaroni, R., Raffaelli, A., Settambolo, R., Bertozzi, S., & Vitulli, G. (1989). Regioselectivity in the rhodium-catalyzed hydroformylation of styrene as a function of reaction temperature and gas pressure. Journal of Molecular Catalysis, 50(1), 1-9. doi:10.1016/0304-5102(89)80104-xYu, S., Chie, Y., Guan, Z., Zou, Y., Li, W., & Zhang, X. (2008). Highly Regioselective Hydroformylation of Styrene and Its Derivatives Catalyzed by Rh Complex with Tetraphosphorus Ligands. Organic Letters, 11(1), 241-244. doi:10.1021/ol802479

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Background There is some evidence to suggest that ginseng and Ginkgo biloba can improve cognitive performance, however, very little is known about the mechanisms associated with such improvement. Here, we tested whether cardiovascular reactivity to a task is associated with cognitive improvement. Methodology/Principal findings Using a double-blind, placebo controlled, crossover design, participants (N = 24) received two doses of Panax Ginseng (500, 1000 mg) or Ginkgo Biloba (120, 240 mg) (N = 24), and underwent a series of cognitive tests while systolic, diastolic, and heart rate readings were taken. Ginkgo Biloba improved aspects of executive functioning (Stroop and Berg tasks) in females but not in males. Ginseng had no effect on cognition. Ginkgo biloba in females reversed the initial (i.e. placebo) increase in cardiovascular reactivity (systolic and diastolic readings increased compared to baseline) to cognitive tasks. This effect (reversal) was most notable after those tasks (Stroop and Iowa) that elicited the greatest cardiovascular reactivity during placebo. In males, although ginkgo also decreased cardiovascular readings, it did so from an initial (placebo) blunted response (i.e. decrease or no change from baseline) to cognitive tasks. Ginseng, on the contrary, increased cardiovascular readings compared to placebo. Conclusions/Significance These results suggest that cardiovascular reactivity may be a mechanism by which ginkgo but not ginseng, in females is associated with certain forms of cognitive improvement

Chemical characterization of cloud episodes at a ridge site in Tuscan Appennines, Italy

Cloudwater samples were collected from November 1992 to March 1995 in Vallombrosa, a mountain site of the Tuscan Apennines (central Italy). Chemical analyses show that all examined inorganic ions contributed significantly to the total ionic content (TIC). The ratio SO4/NO4 ranged from 0.92 to 3.46 and was > 1 for 86% of samples. There is a wide range in the chemical composition of the cloudwater. The total ionic content ranged from 640 to 7476 Aeq l 1 and pH from 3.17 to 6.22. The liquid water content (LWC) ranged from 0.06 to 0.94 g m 3 and electrical conductivity from 47 to 485 AV 1. The total ionic content decreases while the liquid water content increases. Also analyzed were soluble trace metals (Fe, Pb, Cu, Mn, Cd, Al), synthetic anionic surfactants and the methanesulphonic acid. Chemical analyses evidenced in some cases a high concentration of organic matter. The meteorological analysis for a few samples of individual passages was carried out for the possibility of establishing a correspondence between meteorological events and chemical composition. The sources (marine, crustal and anthropogenic) of chemical components were deduced

Individual differences in the context-dependent recruitment of cognitive control: Evidence from action versus state orientation

The ability to flexibly adapt to deviations from optimal performance is an important aspect of self-control. In the present study, the authors present first evidence that the personality trait action versus state orientation (Kuhl, 2000) modulates the ability of adaptive control adjustments in response to experienced conflicts. Sixty-two German individuals with extreme scores on the action-state dimension performed a response interference task, that is, 31 extreme action-oriented individuals (30 females; Mage  = 20.35 years) and 31 extreme state-oriented individuals (20 females; Mage  = 23.23 years), respectively. Action-oriented individuals displayed a stronger conflict adaptation effect as evidenced by a stronger reduction of interference on trials following conflict. These results were further corroborated by a correlational analysis including a sample of 105 participants: the higher the score on the action-state dimension, the lower the interference effect following conflict (i.e., stronger conflict adaptation). The results provide evidence that even low-level, bottom-up-driven processes of self-control such as conflict adaptation are systematically moderated by individual differences in control modes and provide insights into the cognitive mechanisms underlying action versus state orientation