Trimesityltriangulene: a persistent derivative of Clar's hydrocarbon

Triangulene, known as Clar’s hydrocarbon, is a prototypical non-Kekule ́ diradical comprised of six benzenoid rings fused in a trian-gular shape. We synthesized and characterized its trimesityl derivative, illustrating that three bulky substituents installed in the centers of the zigzag edges suffice to protect all reactive positions. This work brings prospects to use triangulene and its open-shell analogs in spintronic materials via solution-phase synthesis

Trimesityltriangulene: a persistent derivative of Clar's hydrocarbon.

Triangulene, known as Clar's hydrocarbon, is a prototypical non-Kekulé diradical comprised of six benzenoid rings fused in a triangular shape. We synthesized and characterized its trimesityl derivative, illustrating that three bulky substituents installed in the centers of the zigzag edges suffice to protect all reactive positions. This work brings prospects to use triangulene and its open-shell analogs in spintronic materials via solution-phase synthesis

Validation of the triplet ground state in a persistent derivative of Clar’s hydrocarbon

Triangulene is a prototypical non-Kekulé diradical known as Clar’s hydrocarbon. It is the smallest non-Kekulé graphene fragment comprised of six benzenoid rings fused in a triangular shape. In accordance with Hund’s rule, a triplet ground state is predicted for this hydrocarbon. However, because of its high reactivity, synthesis of a stable or persistent derivative of neutral triangulene to validate this prediction has been an elusive goal for almost 70 years. Herein, we report the synthesis and characterization of the first persistent derivative of triangulene, kinetically stabilized by three sterically demanding substituents installed at the most reactive positions in the centers of the zigzag edges. The triplet ground state of this hydrocarbon is unequivocally confirmed by pulse electron paramagnetic resonance spectroscopy and supported by density functional theory. The realization of a long-sought-after persistent triangulene derivative will motivate the synthesis of analogous open-shell graphene fragments as prospective building blocks of high-spin materials for the newly emerging field of organic spintronics

Acoustic divergence in the communication of cryptic species of nocturnal primates (<it>Microcebus ssp</it>.)

<p>Abstract</p> <p>Background</p> <p>A central question in evolutionary biology is how cryptic species maintain species cohesiveness in an area of sympatry. The coexistence of sympatrically living cryptic species requires the evolution of species-specific signalling and recognition systems. In nocturnal, dispersed living species, specific vocalisations have been suggested to act as an ideal premating isolation mechanism. We studied the structure and perception of male advertisement calls of three nocturnal, dispersed living mouse lemur species, the grey mouse lemur (<it>Microcebus murinus</it>), the golden brown mouse lemur (<it>M. ravelobensis</it>) and the Goodman's mouse lemur (<it>M. lehilahytsara</it>). The first two species occur sympatrically, the latter lives allopatrically to them.</p> <p>Results</p> <p>A multi-parameter sound analysis revealed prominent differences in the frequency contour and in the duration of advertisement calls. To test whether mouse lemurs respond specifically to calls of the different species, we conducted a playback experiment with <it>M. murinus </it>from the field using advertisement calls and alarm whistle calls of all three species. Individuals responded significantly stronger to conspecific than to heterospecific advertisement calls but there were no differences in response behaviour towards statistically similar whistle calls of the three species. Furthermore, sympatric calls evoked weaker interest than allopatric advertisement calls.</p> <p>Conclusion</p> <p>Our results provide the first evidence for a specific relevance of social calls for speciation in cryptic primates. They furthermore support that specific differences in signalling and recognition systems represent an efficient premating isolation mechanism contributing to species cohesiveness in sympatrically living species.</p