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Abstract: Two series of dyes have been designed and theoretically characterized through density functional theory and timedependent density functional theory to systematically explore the structure--property relationship of dyes with D-A-π-A [...]

Graphical abstract The photoelectrons of excited state EY mainly focused on the upper surface of C 5 O ring with the COO− side. The dominating adsorption of EY on Ru was beneficial for the photoelectron transfer from EY to Ru. Highlight • The adsorption of EY on Ru 4 and Pt 4 and the exited state of EY were investigated using the density functional theory (DFT). • The photoelectrons of excited state EY mainly focused on the upper surface of C 5 O ring with the COO− side. • The dominating adsorption of EY on Ru was beneficial for the photoelectron transfer. Abstract This work investigated the adsorption of Eosin Y (EY) on the surface of Ru 4 and Pt 4 clusters and the UV–vis adsorption of EY by the DFT and TD-DFT method, respectively. The relationship of adsorption action, adsorption energy and hydrogen production efficiency in EY-sensitized system were studied as well. It is proved that the enhancement in the interaction energy of key group in sensitizer and co-catalyst was an efficient method to improve hydrogen evolution performance. The TD-DFT calculation showed that the photoelectrons of excited state EY mainly focused on the upper surface of C 5 O ring with the COO− side. In the EY-Ru 4 system, the maximum adsorption energy originated from the concurrent interaction of the COO− and C 5 O groups of EY with the Ru 4 cluster was −237.8 kJ/mol, while in the EY-Pt 4 system the maximum adsorption energy from the interaction between the C atom on C 6 ring of EY and the Pt 4 cluster was −230.5 kJ/mol. Compared with EY-Pt system, the dominating adsorption of EY on Ru was conducive to the quick transfer of photoelectron from EY to Ru. Therefore, the EY-Ru system exhibited higher hydrogen generation efficiency than the EY-Pt system. [ABSTRACT FROM AUTHOR]

Allyl alcohol could provide an interesting model for chemocontrol in transition metal-catalyzed insertion of carbenoid into O H bond and olefin cyclopropanation. The chemoselectivity of PtCl 2 - and PtCl 4 -catalyzed (compared to Rh and Cu) reactions between methyl α-diazophenylacetate and unsaturated allyl alcohol has been carried out by DFT calculations. The potential energy profiles confirm that the intermediate free enol formed by intramolecular proton transfer is more favorable compared to the formation of the free ylide and cyclopropanation. The [1,3]-proton shift of the enol readily provides the final O H insertion product, which has a barrier of 4.5 and 6.9 kcal/mol using metal-assisted two-allyl-alcohol clusters as a proton shuttle. Calculations provide a good explanation for the O H insertion vs cyclopropanation of platinum, copper and rhodium catalysts have been used in these reactions. This study is expected to improve the understanding of platinum-catalyzed reactions for the C X bond construction and provide guidance for the future design of new catalysts and new reactions. [ABSTRACT FROM AUTHOR]

The dehydrogenation reaction mechanism of cyclohexane catalyzed by dimer transition metal cluster V2+ has been investigated at the B3LYP/6-31G (d, p) level of density functional theory. Density of states (DOS) graph is used to understand more deeply the roles of the front molecular orbital of the initial complexes. After the first molecular dehydrogenation, the reaction mainly consists of two competition mechanisms. First, the C-H bonds of cyclohexane can be effectively activated by the V2+ cation, yielding the same-face dehydrogenation products. Second, the C-C bonds are activated, forming the different-face dehydrogenation products. Our calculations indicate that the reaction takes place more easily along the low-spin potential energy surface on the same-face and is a low-barrier or even barrier-free transformation. Carbon-carbon single bonds are nonpolar and generally far less reactive. A comparison of the reaction mechanism of V2+ and congener Ti2+ with cyclohexane has been presented. The bond dissociation energies (BDEs) of V2+ are greater than that of Ti2+, leading to difficulties in forming sandwich complexes in the different-face dehydrogenation of cyclohexane, and the same-face dehydrogenation is an important reaction channel. [ABSTRACT FROM AUTHOR]

The first thorough theoretical mechanism analysis of heteronuclear bimetallic cation NiAl + with cyclohexane has been investigated on singlet and triplet potential energy surfaces (PESs) by using density functional theory. Our calculated results show that NiAl + can assist in the decomposition of cyclohexane to form benzene through two types of reaction channel: C H bond activation and H 2 formation; C C bond activation and HD formation. The most important conclusion is that NiAl + exhibits high efficiency and also high regioselectivity for C H bond oxidation. However, the high zero-point vibrational energy (ZPVE) value for the cleavage of inert C C bond is also the origin of its failure to form HD. In the process of the first C H and C C bond activations, crossing points (CPs) have been appeared between the two adiabatic surfaces, respectively. The minimum energy crossing points (MECPs) are gotten using the algorithmin Harvey method. Density of states (DOS) is used to obtain a deeper understanding for the roles of the front molecular orbital of the initial complexes. The bonding properties of the special intermediates involved in the process of C C bond activations are discussed by the IR spectrum methods. [ABSTRACT FROM AUTHOR]

In this paper, the reaction mechanism for N 2 O with CO on the surface of Ni 5 cluster was investigated by the B3LYP method of density functional theory (DFT). Ni atom of various species was calculated using B3LYP/ LANL2DZ basis set, and C, N, O atoms at B3LYP/6-31G ∗ level. In the temperature range of 100–1000 K, the statistical thermodynamics and Eyring transition state theory with Winger correction were used to study the kinetic characters of reaction. The calculation results indicated that the reaction of N 2 O with CO on Ni 5 cluster had two major reacting processes: (1) O atom first dissociated from N 2 O on Ni 5 cluster, and then reacted with CO on Ni 5 and (2) on the surface of Ni 5 catalyst, O atom of N 2 O direct interacted with C atom of CO, resulting into the dissociation of N 2 O and the form of CO 2 . The direct O extraction channel was the main channel due to its low potential energy and high rate constant. [ABSTRACT FROM AUTHOR]

The mechanism of Ti 2 + catalyzed cyclohexane dehydrogenation had been studied at the B3LYP level of density functional theory (DFT). The first molecular dehydrogenation products were [Ti 2 (C 6 H 10 )] + and H 2 , this process proceeded quite facile. After the elimination of the first molecular H 2 , there were two competitive mechanisms, one was the same-face dehydrogenation, the other was the H/D scrambling mechanism. The activation barrier for rate determining step of same-face dehydrogenation was 15.34 kcal/mol, while 14.49 kcal/mol for the different-face dehydrogenation which was more favorable than same-face one. Whole reaction proceeded in mixed potential energy surfaces (PESs) and the reaction products were mixture of the doublet and the quartet states. We calculated also all minimum energy crossing points (MECPs) between potential energy surfaces and analyzed bonding orbital of MECPs. [ABSTRACT FROM AUTHOR]

• The mechanism of HER on Mo-Edge with the unsaturated Mo and S were investigated. • The H 2 evolution reaction mainly occurred on Mo U. • The formation of molybdenum hydride (Mo U -H) was the rate-limiting step. In this paper, the mechanisms of H 2 evolution over the Mo-Edge of 2H-MoS 2 with the unsaturated Mo (Mo U) and S (S U) were investigated by the density functional theory. The calculations indicated that Mo U was a key active site for H 2 evolution. In the process of H 2 evolution, the S U firstly absorbed H atom by the Volmer reaction, which caused the aggregation of electron on Mo U , resulting in the barriers reduction of H transfer and H 2 evolution on Mo U. The formation of molybdenum hydride was the rate-limiting step. Compared to Mo-edge in 2H-MoS 2 , the barrier of key step for H 2 evolution on Mo-edge with S U and Mo U decreased obviously. This implied that the removal fractional S from the Mo-edge of 2H-MoS 2 could enhance its H 2 evolution activity and the electron trapping ability of active site for H 2 evolution by the Volmer-Heyrovsky reaction might affect its activity. [ABSTRACT FROM AUTHOR]