Nature of Hydrogen Interaction and Saturation on Small Titanium Clusters

Tarakeshwar, P.; Kumar, T. J. Dhilip; Balakrishnan, N.

doi:10.1021/jp076718j

Cited by 29 publications

(27 citation statements)

References 75 publications

(111 reference statements)

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“…Full geometry optimizations were followed by an evaluation of the vibrational frequencies and the Raman activities. In a recent study carried out by one of us on titanium containing complexes, it was shown that calculations using this method yield geometries and vibrational frequencies in good agreement with experiment [25]. It was also shown in an earlier study that the B3LYP/6-31G* vibrational frequencies, scaled by a factor of 0.9614, yield values in close agreement with experiment [26].…”

Section: Computational Detailssupporting

confidence: 53%

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO₂ nanoparticles

Tarakeshwar

Finkelstein-Shapiro

Rajh

et al. 2010

Int J of Quantum Chemistry

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ABSTRACT:The role of quantum confinement, size, and solvent effects on the surface enhanced Raman spectra of biologically important molecules absorbed on semiconducting titanium dioxide (TiO 2 ) nanoparticles is investigated using density functional calculations. The results obtained for both the gas phase and solvated systems indicate significant changes in the electronic structure and the Raman spectra of molecules like formic acid and dopamine, when they are adsorbed on small TiO 2 nanoparticles. A number of distinctive features that are determined by the formation of a charge-transfer complex at the nanoparticle-molecule interface can be noted in the Raman spectra. Both the spectra and the electronic properties are strongly size dependent and are also sensitive to the presence of the solvent and the nature of adsorbate interaction. Although these calculations reinforce recent experimental findings on the role of quantum confinement, they also pose new questions about the extension of collective effects and the effect of pH and other environmental variables.

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Section: Computational Detailssupporting

confidence: 53%

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO₂ nanoparticles

Tarakeshwar

Finkelstein-Shapiro

Rajh

et al. 2010

Int J of Quantum Chemistry

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“…59,[61][62][63][64][65][66][67][68][69] This level of theory has been found to yield reliable geometries and vibrational frequencies for a number of first-row transition metal systems. [70][71][72][73][74] Nonetheless, in light of recent studies indicating the improved performance of the BP86 and TPSS functionals in describing transition metal containing systems, the geometries and energies of 2 were also calculated using these functionals and the larger TZVPP basis sets. [75][76][77] These results are shown in Table S4 which indicate that the B3LYP/6-31G* level of theory is reliable for the systems investigated in this study.…”

Section: Methodsmentioning

confidence: 99%

Catalytic Hydrogen Evolution by Fe(II) Carbonyls Featuring a Dithiolate and a Chelating Phosphine

et al. 2014

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Abstract:Two pentacoordinate mononuclear iron carbonyls of the form (bdt)Fe(CO)P 2 [bdt = benzene-1,2-dithiolate; P 2 = 1,1'-diphenylphosphinoferrocene (1) or methyl-2-{bis(diphenylphosphinomethyl)amino}acetate (2)] were prepared as functional, biomimetic models for the distal iron (Fe d ) of the active site of [FeFe]-hydrogenase. Xray crystal structures of the complexes reveal that, despite similar ν(CO) stretching band frequencies, the two complexes have different coordination geometries. In X-ray crystal structures, the iron center of 1 is in a distorted trigonal bipyramidal arrangement, and that of 2 is in a distorted square pyramidal geometry. Electrochemical investigation shows that both complexes catalyze electrochemical proton reduction from acetic acid at mild overpotential, 0.17 and 0.38 V for 1 and 2, respectively. Although coordinatively unsaturated, the complexes display only weak, reversible binding affinity towards CO(1 bar). However, ligand centered protonation by the strong acid, HBF 4 .OEt 2 , triggers quantitative CO uptake by 1 to form a dicarbonyl analogue [1(H)-CO] + that can be reversibly converted back to 1 by deprotonation using NEt 3 . Both crystallographically determined distances within the bdt ligand and DFT calculations suggest that the iron centers in both 1 and 2 are partially reduced at the expense of partial oxidation of the bdt ligand. Ligand protonation interrupts this extensive electronic delocalization between the Fe and bdt making 1(H) + susceptible to external CO binding.3

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“…[33][34][35][36][37][38][39][40][41][42][43][44][45] Recent studies have indicated that small icosahedral titanium clusters form stable hydrogen-saturated complexes. [46][47][48] In this paper we investigate icosahedral and cuboctahedral clusters of Sc, Ti, and Zr and examine if this is a general phenomenon exhibited by neighboring elements of titanium from the same row or group. In the absence of any experimental and theoretical studies of hydrogen adsorption and saturation on these metal clusters, we compare and contrast our findings with the more widely studied aluminum clusters.…”

Section: Introductionmentioning

confidence: 99%

“…21,22 Electronic structures of isolated and hydrogen-loaded titanium clusters have been the topic of a number of recent investigations. [46][47][48][49][50][51] To the best of our knowledge, effects of hydrogen adsorption and saturation have not been investigated for zirconium or scandium clusters. However, electronic structures of isolated zirconium and scandium clusters have been the focus of some recent theoretical studies.…”

Section: Introductionmentioning

confidence: 99%

Geometric and electronic structures of hydrogenated transition metal (Sc, Ti, Zr) clusters

2009

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We report first-principles electronic structure calculations of hydrogen adsorption and saturation on M 13 ͑M =Sc,Ti,Zr͒ clusters of icosahedral ͑I h ͒ and cuboctahedral ͑O h ͒ symmetries. Hydrogen saturation of the I h metal clusters yields energetically stable M 13 H 20 and M 13 H 30 systems compared to M 13 H 14 and M 13 H 24 systems for O h clusters. In all these clusters, the hydrogen adsorption involves dissociative chemisorption of H 2 molecules. Upon initial hydrogenation, the dissociated hydrogen atoms lie above either the triangular or quadrangular face of the metal cluster. A further increase in hydrogen saturation leads to the formation of bridged hydrogen bond between adjacent metal atoms. The role of the unfilled d orbitals in imparting stability to the hydrogenated clusters is explored by examining their density of states ͑DOS͒ near the Fermi level. It has been found that the inverse correlation between the d-band center and the chemisorption energies is valid only at low hydrogen concentrations. At higher hydrogen coverages, the trend is reversed. The results illustrate that at high adsorbate concentrations or surface coverage, the correlation of the chemisorption energies with the d-band center of the pure metal cluster or nanoparticle may not be realistic but one has to take into account the changes in the d-orbital DOS due to the presence of coadsorbed molecules. To obtain further insights into the initial steps involved in hydrogen adsorption and dissociation, the transition states and activation energies of the M 13 H 2 system have been determined and found to conform with the empirical Brønsted-Evans-Polanyi relationship. A highly intense infrared band in the 1000-1500 cm −1 region, associated with the adsorbed hydrogens in these hydrogenated metal clusters, may be used to experimentally monitor hydrogen coverage.

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Nature of Hydrogen Interaction and Saturation on Small Titanium Clusters

Cited by 29 publications

References 75 publications

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO₂ nanoparticles

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO₂ nanoparticles

Catalytic Hydrogen Evolution by Fe(II) Carbonyls Featuring a Dithiolate and a Chelating Phosphine

Geometric and electronic structures of hydrogenated transition metal (Sc, Ti, Zr) clusters

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Nature of Hydrogen Interaction and Saturation on Small Titanium Clusters

Cited by 29 publications

References 75 publications

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO2 nanoparticles

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO2 nanoparticles

Catalytic Hydrogen Evolution by Fe(II) Carbonyls Featuring a Dithiolate and a Chelating Phosphine

Geometric and electronic structures of hydrogenated transition metal (Sc, Ti, Zr) clusters

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Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO₂ nanoparticles

Quantum confinement effects on the surface enhanced Raman spectra of hybrid systems molecule‐TiO₂ nanoparticles