Indenoannulated Tridecacyclene: An All-Carbon Seven-Stage Redox-Amphoter.

We disclose an indenoannulated tridecacyclene comprising a central cyclooctatetraene moiety with multiple adjacent pentagonal rings which is accessible in a concise synthetic sequence. The saddle-shaped geometry of the non-benzenoid polycyclic scaffold and its unique packing behavior in the solid state were characterized by X-ray crystallography. In electrochemical studies, the compound undergoes seven reversible redox events comprising five reductions and two oxidations. The dicationic and dianionic species obtained by chemical oxidation and reduction, respectively, were characterized spectroscopically in solution. Density functional theory calculations were applied to provide insights into aromaticity evolution in the respective charged species, highlighting the beneficial effect of the non-benzenoid moieties on charge stabilization.

Efficient Intramolecular Singlet Fission in Spiro-Linked Heterodimers.

We investigate intramolecular singlet fission (iSF) of spiro-linked azaacene heterodimers by time-resolved spectroscopy and quantum chemical calculations. Combining two different azaacenes through a nonconjugated linker using condensation chemistry furnishes azaacene heterodimers. Compared to their homodimers, iSF quantum yields are improved at an extended absorption range. The driving force of iSF, the energy difference ΔEiSF between the S1 state and the correlated triplet pair 1(TT), is tuned by the nature of the heterodimers. iSF is exothermic in all of the herein studied molecules. The overall quantum yield for triplet exciton formation reaches approximately 174%. This novel concept exploits large energy differences between singlet electronic states in combination with spatially fixed chromophores, which achieves efficient heterogeneous iSF, if the through-space interaction between the chromophores is minimal.

Self-forming double-crosslinked hydrogels by the marriage of catechols and enzyme mimetic polymers.

Self-forming double-crosslinked (DC) hydrogels were designed by incorporating enzyme-mimicking metal coordination polymer crosslinks and catechol chemistry. A macromolecular tris-histidine copper complex acted both as part of the hydrogel network and as a catalyst of catechol oxidation to induce a second hydrogel network by covalent crosslinking of catechol functionalized polymers thus giving catalytic control over hydrogel crosslinking.

TIPS-Ethynylated Naphthodiquinoline and Naphthodiacridine: Novel Diazabisacenes.

The synthesis of two diazabisacenes is reported. A bisboronated naphthalene was Suzuki-coupled to substituted ethyl nicotinates, then cyclized by intramolecular Friedel-Crafts acylation. The resulting diketones were alkynylated and reduced to give the title compounds, bis(TIPS-ethynyl)-substituted naphtha[1,8-gh:5,4-g'h']diquinoline and naphtho[1,8-bc:5,4-b'c']diacridine. Nitrogen incorporation stabilizes the bisacenes with respect to oxidation compared to their consanguine nonaza analogs.