Notes

We characterize the transition states between olympicene's isomers, observe differences in aromaticity among the different isomers, and compare the electronic properties of olympicene to those of pentacene
The olympicene molecule has the potential to complement pentacene as an organic semiconductor.A Stochastic Search for the Structures of Small Germanium Clusters and Their Anions: Enhanced Stability by Spherical Aromaticity of the Ge10 and Ge12(2-) Science Center, Katholieke Universiteit Leuven , B-3001 Leuven, Belgium.Investigations on germanium clusters in the neutral, anionic, and dianion states Gen(x) (n = 2-12 and x = 0, -1, -2) are performed using quantum chemical calculations with the B3LYP functional and the coupled-cluster singles and doubles [CCSD(T)] methods, in conjunction with the 6-311+G(d) basis set. An improved stochastic method is implemented for searching the low-lying isomers of clusters. Comparison of our results with previous reports on germanium clusters shows the efficiency of the search method. Seebio Photosensitive Acid Generator is presented in detail.

The anionic clusters Gen(-/2-) are studied theoretically and systematically for the first time, and their energetics are in good agreement with available experiments. The clusters Ge10, Ge10(2-), and Ge12(2-) are, in their ground state, characterized by large highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, high vertical and adiabatic detachment energies, and substantial average binding energies. The enhanced stability of these magic clusters can consistently be rationalized using the jellium electron shell model and the spherical aromatic character.Three-level topology switching in a molecular Möbius band.Möbius pi-conjugation in cyclic molecules leads to the reversal of Huckel aromaticity rules and affects the electronic and magnetic properties of these systems. We found the first example of a medium-sized macrocyclic structure that is sufficiently flexible to switch between three distinct pi-conjugation topologies, planar (T0), Möbius (T1), and twisted Huckel (T2), without changing its oxidation level. The switching is under thermodynamic and kinetic control and can be realized in a three- or four-step cycle.

On titration with trifluoroacetic acid (TFAH) or dichloroacetic acid (DCAH), the Möbius free base undergoes a series of acid-base reactions involving changes of the pi-conjugation topology. The forms observed in the course of titration involve a containing complex carboxylate anions. The protonated forms undergo a thermally activated ring planarization to yield an antiaromatic quasi-planar dication 1,3-Dipolar reactions involving corannulene: how does its rim and spoke addition [reaction: see text] Corannulene undergoes 1,3-dipolar reactions with the dipoles, diazomethane, nitrile oxide, and nitrone through its rim and spoke pi bonds; the rim addition yields "one possible" adduct whereas two "regioselective" adducts are formed by spoke addition. Mechanisms of these reactions have been investigated at the B3LYP/6-31G(d) level. Computations show that both rim and spoke additions prefer concerted pathways that lie 2-5 kcal/mol lower in energy than stepwise paths. Stepwise additions can take place in two ways and the activation energies of these two modes differ by 1-2 kcal/mol. A close inspection of the energy profiles reveals that rim addition is more favorable kinetically and thermodynamically than spoke addition in view of lower activation energy and higher exothermicity observed for rim addition.

The rim bond of corannulene is more flexible for distortion and also has a stronger double bond (i.e. pi-character) than the spoke bond and this facilitates rim addition over spoke addition. Deformation energy analysis also confirms the above through higher deformation in corannulene from the spoke addition when compared to rim addition. In the spoke addition, regio1 reaction is kinetically more favored than regio2 reaction. Attempts to react corannulene in an endohedral fashion have led to the exohedral adduct. Computed activation energies suggest that corannulene acts as a deactivated dipolarophile compared to ethylene.

Even more striking is the observation that rim and spoke double bonds in corannulene are part of the local aromatic system but it shows remarkable reactivity compared to benzene despite the loss of aromaticity during the reaction. This is well indicated by computed NICS values. Synthesis of 6-butyl-n-hydroxynaphthimide trifluoromethanesulfonic acid and its Variants of acetonitrile as solvent through the PCM model increases the reaction rate and A periodicity analysis of transmembrane helices.Chemistry, The Hebrew University, Givat-Ram, Jerusalem 91904, Israel.Transmembrane helices and the helical bundles which they form are the major building blocks of membrane proteins. Since helices are characterized by a given periodicity, it is possible to search for patterns of traits which typify one side of the helix and not the other (e.g.

amphipathic helices contain a polar and apolar sides). Using Fourier transformation we have analyzed solved membrane protein structures as well as sequences of membrane proteins from the Swiss-Prot database. The traits searched included aromaticity, volume and ionization. While a number of motifs were already recognized in the literature, many were not. One particular example involved helix VII of lactose permease which contains seven aromatic residues on six helical turns.
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