Uptake of one and two molecules of CO2 by the molybdate dianion: a soluble, molecular oxide model system for carbon dioxide fixation

Tetrahedral [MoO4][superscript 2−] readily binds CO[subscript 2] at room temperature to produce a robust monocarbonate complex, [MoO[subscript 3](κ[superscript 2]-CO[subscript 3])][superscript 2−], that does not release CO[subscript 2] even at modestly elevated temperatures (up to 56 °C in solution and 70 °C in the solid state). In the presence of excess carbon dioxide, a second molecule of CO[subscript 2] binds to afford a pseudo-octahedral dioxo dicarbonate complex, [MoO[subscript 2](κ[superscript 2]-CO[subscript 3])[subscript 2][superscript 2−], the first structurally characterized transition-metal dicarbonate complex derived from CO[subscript 2]. The monocarbonate [MoO[subscript 3](κ[superscript 2]-CO[subscript 3])][superscript 2−] reacts with triethylsilane in acetonitrile under an atmosphere of CO[subscript 2] to produce formate (69% isolated yield) together with silylated molybdate (quantitative conversion to [MoO[subscript 3](OSiEt[subscript 3])][superscript −], 50% isolated yield) after 22 hours at 85 °C. This system thus illustrates both the reversible binding of CO[subscript 2] by a simple transition-metal oxoanion and the ability of the latter molecular metal oxide to facilitate chemical CO[subscript 2] reduction.Saudi Basic Industries CorporationSpain. Ministerio de Educación, Cultura y DeporteSpain. Ministerio de Economía y Competitividad (CTQ2012-36966)National Science Foundation (U.S.) (CHE-1111357)National Science Foundation (U.S.) (CHE- 0946721

Reactivity of Tuck-over Titanium Oxo Complexes with Isocyanides

The reactivity of the "tuck-over" species [Ti2(η5-C5Me5)(CH2Ph)3(μ-η5-C5Me4CH2-κC)(μ-O)] (1) and [Ti2(η5-C5Me5)(CH2CMe3)(μ-η5-C5Me4CH2-κC)(μ-CH2CMe2CH2)(μ-O)] (2) toward isocyanides has been examined both synthetically and theoretically. Treatment of 1with the isocyanides RNC, R = Me3SiCH2, 2,6-Me2C6H3, tBu,iPr, leads to a series of η2-iminoacyl species (3−6) where the molecule of isocyanide inserts into one of the terminal metal−alkyl bonds. The analogous reaction of the "tuck-over" metallacycle species 2 with 2,6-Me2C6H3NC andtBuNC results inthe initial insertion of one isocyanide into the terminal Ti−alkyl bondto form the iminoacyl complexes 7 and 8, followed by a secondinsertion into the metallacycle moiety to generate 9, in the case of tertbutylisocyanide. DFT calculations support the selective reactivity observed experimentally with a kinetic and thermodynamicpreference for RNC insertion on the terminal alkyl groups bound to both metallic centers over the alternative insertion on the "tuck-over"ligand.Ministerio de Economía y Competitividad Universidad de Alcal

Structural Diversity in the Reactions of Dimetallic Alkyl Titanium Oxides with Isonitriles and Nitriles.

A detailed study of the reaction of the dinuclear [{Ti(eta(5)-C5Me5)R-2}(2)(mu-O)] (R = Me 1, CH2Ph 2) compounds with a series of organic isonitriles (R'NC, R' = tBu, iPr, CH2SiMe3, Xyl) (Xyl = 2,6-Me2C6H3) and nitriles (R'CN, R' = tBu, iPr, SiMe3) has been carried out. Single-crystal X-ray structural studies revealed a variety of reactivity and structural moieties. Theoretical calculations (density functional theory, DFT) were used to understand the mechanism of some uncommon reactions observed experimentally. Reactions of 1 and 2 with isocyanides tBuNC, iPrNC, and Me3SiCH2NC led to the formation of dimetallic eta(2)-iminoacyl species [{Ti(eta(5)-C5Me5)(R'NCR)R}(2)(mu-O)] (R = Me, R' = tBu 3, iPr 4, CH2SiMe3 5; R = CH2Ph, R' = CH2SiMe3 6). Complex 4 underwent net rearrangements at room temperature to give the imido-vinylamido derivative [Ti-2(eta(5)-C5Me5)(2)(mu-O)(mu-NiPr) {N(iPr)CMe=CMe2}Me] (7), whereas the reaction of complex 2 with XylNC rendered the N-C bond cleavage product [{Ti(eta(5)-C5Me5)(CH=CHPh)}(mu-O)(mu-kappa(2)-N,C-N(MeC6H3)CH2){Ti(eta(5)-C5Me5)}] (8). The reactions of 1 with nitriles tBuCN and iPrCN gave the ketimido products [{Ti(eta(5)-C5Me5)Me(CN(Me)R')}(2) (mu-O)] (R' = tBu 9, iPr 10), whereas the analogous processes with 2 gave the alkenyl-imido complexes [{Ti(eta(5)-C5Me5)(CH2Ph)(2)}(mu-O){Ti(eta(5)-C5Me5)(=NC(R')=C(H)Ph)(NCR')}] (R' = tBu 11, iPr 12) with the concomitant coordination of a nitrile molecule. Complex 1 reacts with Me3SiCN to afford the nitrile-isonitrile isomerization product [{Ti(eta(5)-C5Me5)Me-2}(mu-O){Ti(eta(5)-C5Me5)(kappa(2)-C,N-Me-2 CNSiMe3 )(CNSiMe3)] (13).Consorcio Madroño - Universidad de Alcal

Structural Substituent Effect in the Excitation Energy of aChromophore: Quantitative Determination and Application toS-Nitrosothiols

A methodology for the prediction of excitation energies for substituted chromophores on the basis of ground state structures has been developed. The formalism introduces the concept of ?structural substituent excitation energy effect? for the rational prediction and quantification of the substituent effect in the excitation energy of a chromophore to an excited electronic state. This effect quantifies exclusively the excitation energy variation due to the structural changes of the chromophore induced by the substituent. Therefore, excitation bathochromic and hypsochromic shifts of substituted chromophores can be predicted on the basis of known ground and excited potential energy surfaces of a reference unsubstituted chromophore, together with the ground state minimum energy structure of the substituted chromophore. This formalism can be applied if the chemical substitution does not affect the nature of the electronic excitation, where the substituent effect can be understood as a force acting on the chromophore and provoking a structural change on it. The developed formalism provides a useful tool for quantitative and qualitative determination of the excitation energy of substituted chromophores and also for the analysis and determination of the structural changes affecting this energy. The proposed methodology has been applied to the prediction of the excitation energy to the first bright state of several S-nitrosothiols using the potential energy surfaces of methyl-S-nitrosothiol as a reference unsubstituted chromophore.Ministerio de Ciencia e InnovaciónUniversidad de Alcal

Substituent and ring effects on enthalpies of formation: 2-methyl- and 2-ethylbenzimidazoles versus benzene-and imidazole-derivatives

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-methylbenzimidazole (2MeBIM) and 2-ethylbenzimidazole (2EtBIM) are reported and the results compared with those of benzimidazole itself (BIM). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311+G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of benzenes, imidazoles and benzimidazoles bearing H (unsubstituted), methyl and ethyl groups shows remarkable homogeneity. The energetic group contribution transferability is not followed, but either using it or adding an empirical interaction term, it is possible to generate an enormous collection of reasonably accurate data for different substituted heterocycles (pyrazole-derivatives, pyridine-derivatives, etc.) from the large amount of values available for substituted benzenes and those of the parent (pyrazole, pyridine) heterocycles.We acknowledge the financial support of the DGI/MCyT (project nos. BQU-2003-00976, 01251 and 05827). This work has been partially supported by the DGI project no. BQU-2003-00894. A generous allocation of computational time at the CCC of the Universidad Auto´noma de Madrid is also gratefully acknowledged. Thanks are also due to Instituto de Cooperac¸a˜o Cientı´fica e Tecnolo´gica Internacional (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain, for a joint research project ICCTI/CSIC. MLPFA thanks Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (PRAXIS XXI/BPD/16319/98) and MT thanks MECD/SEEU (AP 2002-0603), Spain, for financial support

Substituent effects on enthalpies of formation of nitrogen heterocycles: 2-substituted benzimidazoles and related compounds

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-tert-butylbenzimidazole (2tBuBIM) and 2-phenylimidazole (2PhIM) are reported and the results compared with those of benzene derivatives and a series of azoles (imidazoles, pyrazoles, benzimidazoles and indazoles). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311++G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of all studied compounds bearing H (unsubstituted), methyl (Me) ethyl (Et), propyl (Pr), isopropyl (iPr), tert-butyl (tBu), benzyl (Bn) and phenyl (Ph) groups show remarkable homogeneity. The remarkable consistency of both the calculated and experimental results allows us to predict with reasonable certainty the missing experimental values. The crystal and molecular structure of the 2-benzylbenzimidazole (2BnBIM) has been determined by X-ray analysis. The observed molecular conformation permits the crystal being built up through N−H···N hydrogen bonds and van der Waals contacts between the molecules. An attempt has been made to relate the crystal structure to the enthalpies of sublimation.Thanks are due to Instituto de Cooperac¸a˜o Cientı´fica e Tecnolo´gica International (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain. L.M.P.F.A. thanks Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (PRAXIS XXI/BPD/16319/98). This work has also been financed by DGICYT (BQU-2003- 00894, -00976 and -01251)

Experimental thermochemical study of two 2-alkylbenzimidazole isomers (alkyl = propyl and isopropyl)

This paper reports the values of the standard (p∘=0.1 MPa) molar enthalpy of formation in the condensed, at T=298.15 K, for 2-R-benzimidazoles (R=propyl, isopropyl), derived from, the respective enthalpies of combustion in oxygen, measured by static bomb combustion calorimetry and the standard molar enthalpies of sublimation, at T=298.15 K, obtained using Calvet microcalorimetry in the case of 2-isopropylbenzimidazole and, by the variation of vapour pressures, determined by the Knudsen effusion technique, with temperatures between (344 and 365) K for 2-propylbenzimidazole. Heat capacities, in the temperature ranges from T=268 K to near their respective melting temperatures, T=421 K for 2-propylbenzimidazole and T=464 K for 2-isopropylbenzimidazole, were measured with a differential scanning calorimeter. These values were used to derive the standard molar enthalpies of formation, of the two 2-benzimidazole derivatives, in gaseous phase.Thanks are due to Instituto de Cooperação Cientı́fica e Tecnológica Industrial (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı́ficas (CSIC), Madrid, Spain for a joint research project CSIC/ICCTI; M.L.P.F.A. thanks Fundação para a Ciência e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (SRFH/BPD/5595/2001). The Spanish DGI/MCyT is acknowledged under projects BQU2000-0252, 0906 and 1497; M.T. thanks MECD/SEEU, AP2002-0603, Spain for financial support

Experimental and theoretical study of the structures and enthalpies of formation of the synthetic reagents l,3-thiazolidine-2-thione and l,3-oxazolidine-2-thione

This paper reports an experimental and a theoretical study of the structures and standard (po = 0.1 MPa) molar enthalpies of formation of the synthetic reagents 1,3-thiazolidine-2-thione [CAS 96-53-7] and 1,3-oxazolidine-2-thione [CAS 5840-81-3]. The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry, and the Knudsen effusion technique and gas-phase enthalpies of formation values at T = 298.15 K of (97.1 ± 4.0) and −(74.4 ± 4.6) kJ·mol−1 for 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in reasonable agreement with the experimental values. In the solid state, 1,3-thiazolidine-2-thione exists in two polymorphic forms (monoclinic and triclinic) and 1,3-oxazolidine-2-thione exits in the triclinic form. The isostructural nature of these compounds and comparison of their molecular and crystal structures have been analyzed. The experimental X-ray powder diffractograms have been compared with the calculated patterns from their structures for identification of the polymorphic samples used in this study. A comparison of our results with literature thermochemical and structural data for related compounds is also reported.M.T. would like to thank MEC/SEUI, FPU AP2002-0603, Spain, for financial support. A.V.D. thanks the National Science Foundation (CHE-0547566) and the American Heart Association (0855743G) for financial support of this research. The support of the Spanish Ministerio de Educación y Ciencia under Projects CTQ2007-60895/BQU and CTQ2006-10178/BQU is gratefully acknowledged

Experimental and Theoretical Study of the Structures and Enthalpies of Formation of the Synthetic Reagents 1,3-Thiazolidine-2-thione and 1,3-Oxazolidine-2-thione

This paper reports an experimental and a theoretical study of the structures and standard (p o ) 0.1 MPa) molar enthalpies of formation of the synthetic reagents 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione . The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry, and the Knudsen effusion technique and gas-phase enthalpies of formation values at T ) 298.15 K of (97.1 ( 4.0) and -(74.4 ( 4.6) kJ · mol -1 for 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in reasonable agreement with the experimental values. In the solid state, 1,3-thiazolidine-2-thione exists in two polymorphic forms (monoclinic and triclinic) and 1,3-oxazolidine-2-thione exits in the triclinic form. The isostructural nature of these compounds and comparison of their molecular and crystal structures have been analyzed. The experimental X-ray powder diffractograms have been compared with the calculated patterns from their structures for identification of the polymorphic samples used in this study. A comparison of our results with literature thermochemical and structural data for related compounds is also reported

Projecte d'una instal·lació fotovoltaica de 140 kW per a autoconsum a Benifaió

[ES] En este proyecto se realiza el diseño y dimensionado de una instalación solar fotovoltaica de 140 kW interconectada a red en la modalidad de autoconsumo sin excedentes para una empresa del sector cárnico ubicada en Benifaió. Para su elaboración se emplean los programas Excel, PVGIS y AutoCAD. El proyecto contempla el diseño y la selección de los diversos componentes de la instalación, así como los cálculos eléctricos necesarios. Finalmente se realiza un análisis de los beneficios energéticos, económicos y ambientales obtenidos, y se evalúa su contribución a los Objetivos de Desarrollo Sostenible.[EN] In this project, the design and dimensioning of a 140 kW photovoltaic solar installation interconnected to the grid in the modality of self-consumption without surpluses is carried out for a company in the meat sector located in Benifaió. For its elaboration, the Excel, PVGIS and AutoCAD programs are used. The project contemplates the design and selection of the various components of the installation, as well as the necessary electrical calculations. Finally, an analysis of the energy, economic and environmental benefits obtained is carried out, and their contribution to the Sustainable Development Goals is evaluated.Temprado Navarro, M. (2023). Proyecto de una instalación fotovoltaica de 140 kW para autoconsumo en Benifaió. Universitat Politècnica de València. http://hdl.handle.net/10251/19576