We report on avery unusual case of surface catalysis involving azobenzenes in contact with aA u(111) surface.A rate acceleration of the cis-trans isomerization on gold up to af actor of 1300 compared to solution is observed. By using carefully designed molecular frameworks,t he electronic coupling to the surface can be systematically tuned. The isomerization kinetics of molecules with very weak coupling to the metal is similar to that found in solution. Fortheir counterparts with strong coupling,the relaxation rate is shown to depend on the spin-density distribution in the triplet states of the molecules.T his suggests that an intersystem crossing is involved in the relaxation process.A side from their impact on catalytic processes,t hese effects could be used to trigger reactions over long distances.

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The synthesis of a borylated Ni porphyrin and its application as a versatile precursor for building up functional ortho-substituted tetraaryl porphyrin architectures is reported. This precursor porphyrin provides the basis for efficient modular syntheses of porphyrin compounds with covalently attached axial ligands which are important as enzyme model complexes, electron transfer dyads, and many other applications. In the present study, the precursor porphyrin was used for the synthesis of molecular spin switches which previously showed high potential as photoresponsive contrast agents for magnetic resonance imaging.

We report on avery unusual case of surface catalysis involving azobenzenes in contact with aA u(111) surface.A rate acceleration of the cis-trans isomerization on gold up to af actor of 1300 compared to solution is observed. By using carefully designed molecular frameworks,t he electronic coupling to the surface can be systematically tuned. The isomerization kinetics of molecules with very weak coupling to the metal is similar to that found in solution. Fortheir counterparts with strong coupling,the relaxation rate is shown to depend on the spin-density distribution in the triplet states of the molecules.T his suggests that an intersystem crossing is involved in the relaxation process.A side from their impact on catalytic processes,t hese effects could be used to trigger reactions over long distances.

Triazatriangulenium (TATA) and trioxatriangulenium (TOTA) ions are particularly suited systems to mount functional molecules onto atomically flat surfaces such as Au(111). The TATA and TOTA units serve as platforms that absorb onto the surface and form ordered monolayers, while the functional groups are protruding upright and freestanding from the central carbon atoms. Azobenzene derivatized TATA’s are known to exhibit extremely fast cis→trans isomerization on metal surfaces, via a peculiar non-adiabatic singlet→triplet→singlet mechanism. We now prepared norbornadienes (NBD) and quadricyclanes (QC) attached to TATA and TOTA platforms which can be used to check if these accelerated rates and the spin change mechanism also apply to [2 + 2] cycloreversions (QC→NBD).