In this article, a perspective is given of chemical dynamics simulations collisions biological ions with surfaces and collision-induced dissociation (CID) ions. The provide an atomic-level understanding the and, overall, are in quite good agreement experiment. An integral component ion/surface energy transfer to internal degrees freedom both ion surface. reveal how depends on collision energy, incident angle, ion, With ion's vibration fragmentation may occur, i.e. surface-induced (SID),...

Direct dynamics simulations, utilizing the RM1 semiempirical electronic structure theory, were performed to study thermal dissociation of doubly protonated tripeptide threonine-isoleucine-lysine ion, TIK(H+)2, for temperatures 1250-2500 K, corresponding classical energies 1778-3556 kJ/mol. The number different fragmentation pathways increases with increase in temperature. At 1250 K there are only three pathways, one contributing 85% fragmentation. In contrast, at 2500 61 and not dominates....

The encapsulation of an organic dye, 10-phenylphenothiazine (PTH), in the inner cavity single-walled carbon nanotubes (SWNTs) as a breaking heterogenization strategy is presented. PTH@oSWNT material was microscopically and spectroscopically characterized, showing intense photoemission when illuminated with visible light at nanoscale. Thus, employed heterogeneous photocatalyst single electron transfer dehalogenation reactions under irradiation. showed enhanced photocatalytic activity,...

An ambimodal transition state (TS) that leads to formation of four different pericyclic reaction products ([4 + 6]-, [2 8]-, [8 2]-, and [6 4]-cycloadducts) without any intervening minima has been designed explored with DFT computations quasiclassical molecular dynamics. Direct dynamics simulations propagated from the TS show evolution trajectories give cycloadducts. The topography PES is a key factor in product selectivity. A good correlation observed between geometrical resemblance...

An organocatalytic system is presented for the Michael addition of monoactivated glycine ketimine ylides with a bifunctional catalyst. The bears an ortho hydroxy group, which increases acidity methylene hydrogen atoms and enhances reactivity, thus allowing synthesis large variety α,γ-diamino acid derivatives excellent stereoselectivity.

In the present work we have investigated mechanisms of gas phase unimolecular dissociation a relatively simple dipeptide, di-proline anion, by means chemical dynamics simulations, using PM3 semi-empirical Hamiltonian. particular, considered two activation processes that are representative limits what occurs in collision induced experiments: (i) thermal activation, corresponding to several low energy collisions, which system is prepared with microcanonical distribution energy; (ii)...

By combining chemical dynamics simulations and RRKM statistical theory we have characterized collision induced dissociation (CID) mechanisms of [M(formamide)](2+) ions (M = Ca, Sr) at different timescales, from few femtoseconds to microseconds. Chemical account for the short-time dynamically driven reactivity, such as impulsive mechanism formamide neutral loss. From simulations, also got amounts energy transferred during and, especially important, vibrational rotational distributions that...

Beyond the established use of thermodynamic vs kinetic control to explain chemical reaction selectivity, concept bifurcations on a potential energy surface (PES) is proving be pivotal importance with regard selectivity. In this article, we studied by means post-transition state (TS) direct dynamics simulations effect that vibrational and rotational excitation at TS may have selectivity bifurcating PES. With aim, post-TS unimolecular reactivity [Ca(formamide)](2+) ion, for which Coulomb...

The gas-phase acidity of a series amine-borane complexes has been investigated through the use electrospray mass spectrometry (ESI-MS), with application extended Cooks kinetic method, and high-level G4 ab initio calculations. most significant finding is that typical nitrogen bases, such as aniline, react BH(3) to give complexes, which, in gas phase, have acidities high those either phosphoric, oxalic, or salicylic acid; their higher than many carboxylic acids, formic, acetic, propanoic acid....

Gas phase unimolecular fragmentation of the two model doubly protonated tripeptides threonine-isoleucine-lysine (TIK) and threonine-leucine-lysine (TLK) is studied using chemical dynamics simulations. Attention focused on different aspects collision induced dissociation (CID): pathways, energy transfer, theoretical mass spectra, mechanisms, possibility distinguishing isoleucine (I) leucine (L). Furthermore, discussion given regarding differences between single CID activation, which results...

BODIPY as an EWG in asymmetric catalysis is presented.

BeH₂and BH₃association with unsaturated bases of group 15 increases their acidity and changes the trend. Ethynyl : BeH₂complexes unexpectedly behave as Be acids.

Dissociation chemistry of the diproline anion [Pro2-H]− is studied using chemical dynamics simulations coupled with quantum-chemical calculations and RRKM analysis. Pro2– chosen due to its reduced size small number sites where deprotonation can take place. The mechanisms leading two dominant collision-induced dissociation (CID) product ions are elucidated. Trajectories from a variety isomers were followed in order sample larger range possible reactivity. While different yielding y1–...

Interactions between closed-shell systems exhibit some common features, four of which are particularly strong for beryllium bonds: geometrical distortion, cooperativity, changes in intrinsic reactivity and the magnetic properties interacting subunits, reflect perturbations their electron densities through polarization effects.Structural lead to interaction energies that can only be adequately accounted when effects distortion on system, not its deformation energy, taken into...

Abstract In this work, we describe the use of Boron Dipyrromethene (BODIPY) as electron‐withdrawing group for activation double bonds in asymmetric copper‐catalyzed [3+2] cycloaddition reactions with azomethine ylides. The take place under smooth conditions and high enantiomeric excess a large number different substituents, pointing out alkene by using boron dipyrromethene group. Experimental, theoretical studies comparison other common groups cycloadditions show reasons reactivity...

We present a detailed spectroscopic analysis of the first absorption band six possible conformers 1,6-diphenyl-1,3,5-hexatriene, obtained by changing configuration trans double bonds to cis. To this end, we computed spectra using FCclasses 3.0 code. First, assessed performance PBE0 and CAM-B3LYP density functional theory functionals with different basis sets reproduce experimental spectra. Additionally, considered models compute PBE0/def2tZVP an adiabatic hessian model internal coordinates...

The complexes formed by the interaction between a series of phosphines R-PH(2) (R = H, CH(3), c-C(3)H(5), C(6)H(5)) and AlH(3) have been investigated through use high-level G4 ab initio calculations. These very stable behave as much stronger acids than isolated phosphines. This dramatic acidity enhancement, which can be high 174 kJ mol(-1), results from greater stabilization anionic deprotonated species with respect to neutral one, upon association. effect depends quantitatively on nature...

In this work, we present a density functional theory study of the dipolar cycloaddition azamethylene imines to nitroalkenes, showing importance intramolecular activation hydroxyl group and role intermolecular hydrogen bond with Takemoto's catalyst. The non‐covalent interactions is evaluated by means simulations using interactions, natural bonding orbital analysis. combination these studies allows us understand played intra‐ in reactivity enantioselectivity process.

The addition of nucleophilic imines, using 2-hydroxybenzophenone as a chemical auxiliary, is presented.

A kinetic study of the unimolecular reactivity formamide–M2+ (M = Ca, Sr) systems was carried out by means RRKM statistical theory using high-level DFT. The results predict M2+, [M(NH2)]+ and [HCO]+ as main products, together with an intermediate that could eventually evolve to produce [M(NH3)]2+ CO, for high values internal energy. In this framework, we also evaluated influence external rotational energy on reaction rate constants. order find a method perform reliable electronic structure...

In the present contribution, we have summarized our recent work on comprehension of [Ca(formamide)] 2+ complex gas-phase unimolecular dissociation. By using different theoretical approaches, were able to revise original (and typical for such kind problems) understanding given in terms stationary points potential energy surface, which did not provide a satisfactory explanation experimentally observed reactivity. particular, point out how non-statistical and non-intrinsic reaction coordinate...

A formal highly enantioselective organocatalyzed [3 + 2] cycloaddition of furanones and azomethine ylides paired to a efficient kinetic resolution is presented.

The relative stability of the radicals that can be produced from amine-boranes and phosphine-boranes is investigated at G3-RAD level theory. Aminyl ([RNH](.) :BH3 ) phosphinyl ([RPH](.) are systematically more stable than boryl analogues, [RNH2 ]:BH2 (.) [RPH2 . Despite similar trends for [RNH](.) [RPH](.) with respect to radicals, there significant dissimilarities between amine- phosphine-boranes. homolytic bond dissociation energy NH decreases upon association amines BH3 , whereas PH...

Competing fragmentation pathways for far ultraviolet photodissociation (FUV-PD) of protonated leucine enkephalin. Mechamisms excited and ground state fragmentation.