Ab initio crystal orbital studies on linear chains of H atoms

Anab initio crystal orbital method is used to calculate the energies of an infinite chain of H atoms and of linear arrangements of H₂ molecules with different interatomic distances. The H₂ arrangements are not stable in respect to isolated molecules. The cohesive energy of an optimized arrangement of H atoms chain is 0.0354 a.u.     

Structure and electronic structure of polyacene

It is shown that infinite long polyacene chains may have three energetically close but structurally distinct isomers (a symmetrical, sym, form and two lower symmetry forms: one with double bonds in a trans and another isomer with double bonds in a cis pattern). The energetics is based on solid state MNDO theory. We discuss that the symmetrical form has a substantial energy gap E_g in the Hartree–Fock approach owing to exact exchange terms, which are nonlocal. Broken symmetry Hartree–Fock (HF ) solutions for polyacene are also described. An angularly distorted structure suggested earlier on Jahn–Teller grounds is found to be energetically not favorable.     

Electrochemically initiated tagging of thiols using an electrospray ionization based liquid microjunction surface sampling probe two‐electrode cell

This paper reports on the conversion of a liquid microjunction surface sampling probe (LMJ‐SSP) into a two‐electrode electrochemical cell using a conductive sample surface and the probe as the two electrodes with an appropriate battery powered circuit. With this LMJ‐SSP, two‐electrode cell arrangement, tagging of analyte thiol functionalities (in this case peptide cysteine residues) with hydroquinone tags was initiated electrochemically using a hydroquinone‐doped solution when the analyte either was initially in solution or was sampled from a surface. Efficient tagging (～90%), at flow rates of 5–10 µL/min, could be achieved for up to at least two cysteines on a peptide. The high tagging efficiency observed was explained with a simple kinetic model. In general, the incorporation of a two‐electrode electrochemical cell, or other multiple electrode arrangement, into the LMJ‐SSP is expected to add to the versatility of this approach for surface sampling and ionization coupled with mass spectrometric detection. Published in 2009 by John Wiley & Sons, Ltd.