We investigate the molecular interaction between sulfuric acid and a C6H8O7 ketodiperoxy acid compound (a proxy for highly oxidized products of, e.g., monoterpene autoxidation) in the presence of water, ammonia, or dimethylamine. The molecular geometries are obtained using density functional theory (M06-2X, PW91, and ωB97X-D) with the 6-31++G(d,p) basis set, and the binding energy is corrected utilizing a high-level DLPNO-CCSD(T)/def2-QZVPP calculation. The formation free energies were calculated (ΔG at 298 K and 1 atm), and the stability of the molecular clusters was evaluated. The presence of bases is found to enhance the interaction between ketodiperoxy acid compounds and sulfuric acid. The addition of C6H8O7 compounds to (H2SO4)(NH3) or (H2SO4)((CH3)2NH) clusters is, however, not able to compete with the corresponding uptake of another sulfuric acid molecule, even at a high loading of organic compounds. We furthermore investigate the origin of the weak binding of peroxyacid compounds using atoms in molecules and natural bonding orbital analysis. The weak binding is caused by an internal hydrogen bond and the lack of a strong hydrogen bond acceptor in the peroxyacid group. These findings indicate that autoxidation products containing solely or mainly hydroperoxide and carbonyl functional groups do not participate in the initial step of new particle formation and thereby only contribute to the growth of atmospheric particles.
The reaction of a methyl-substituted benzylazide on the silicon (001) surface was investigated by means of X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and density functional theory (DFT)-based computations. It was found that the reaction takes place via an intermediate state, which could be experimentally observed at low temperatures. XPS analysis showed that at temperatures of 150 K and above, the azide further reacts on the silicon surface via abstraction of N 2 . The final state sees the remaining nitrogen atom of the adsorbate binding covalently to the surface. In the STM images, this final state is associated with two different adsorption configurations. In comparison with DFT calculations, these two configurations are assigned to the molecule being bound via the nitrogen atom only and to a configuration with the molecule bound to the substrate via the nitrogen atom and carbon ring simultaneously.
Phthalocyanines possess unique optical and electronic properties and thus are widely used in (opto)electronic devices, coatings, photodynamic therapy, etc. Extension of their π-electron systems could produce molecular materials with red-shifted absorption for a broader range of applications. However, access to expanded phthalocyanine analogues with more than four isoindoline units is challenging due to the limited synthetic possibilities. Here, we report the controlled on-surface synthesis of a gadolinium-supernaphthalocyanine macrocycle and its open-chain counterpart poly(benzodiiminoisoindoline) on a silver surface from a naphthalene dicarbonitrile precursor. Their formation is controlled by the on-surface high-dilution principle and steered by different metal templates, i.e., gadolinium atoms and the bare silver surface, which also act as oligomerization catalysts. By using scanning tunneling microscopy, photoemission spectroscopy, and density functional theory calculations, the chemical structures along with the mechanical and electronic properties of these phthalocyanine analogues with extended π-conjugation are investigated in detail.
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