Borazatruxenes as precursors for hybrid C-BN 2D molecular networks

Synthesizing atomically thin, crystalline two-dimensional (2D) molecular materials which combine carbon with other elements is an emerging field requiring both custom-designed molecular precursors and their ability to organize into networks...

Structure-controllable growth of nitrogenated graphene quantum dots via solvent catalysis for selective C-N bond activation

Photophysical and photochemical properties of graphene quantum dots (GQDs) strongly depend on their morphological and chemical features. However, systematic and uniform manipulation of the chemical structures of GQDs remains challenging due to the difficulty in simultaneous control of competitive reactions, i.e., growth and doping, and the complicated post-purification processes. Here, we report an efficient and scalable production of chemically tailored N-doped GQDs (NGs) with high uniformity and crystallinity via a simple one-step solvent catalytic reaction for the thermolytic self-assembly of molecular precursors. We find that the graphitization of N-containing precursors during the formation of NGs can be modulated by intermolecular interaction with solvent molecules, the mechanism of wh ich is evidenced by theoretical calculations and various spectroscopic analyses. Given with the excellent visible-light photoresponse and photocatalytic activity of NGs, it is expected that the proposed approach will promote the practical utilization of GQDs for various applications in the near future.

Topological phase transition in chiral graphene nanoribbons: from edge bands to end states

Precise control over the size and shape of graphene nanostructures allows engineering spin-polarized edge and topological states, representing a novel source of non-conventional π-magnetism with promising applications in quantum spintronics. A prerequisite for their emergence is the existence of robust gapped phases, which are difficult to find in extended graphene systems. Here we show that semi-metallic chiral GNRs (chGNRs) narrowed down to nanometer widths undergo a topological phase transition. We fabricated atomically precise chGNRs of different chirality and size by on surface synthesis using predesigned molecular precursors. Combining scanning tunneling microscopy (STM) measurements and theory simulations, we follow the evolution of topological properties and bulk band gap depending on the width, length, and chirality of chGNRs. Our findings represent a new platform for producing topologically protected spin states and demonstrate the potential of connecting chiral edge and defect structure with band engineering.

Synthesis of Unsymmetrically Functionalized Violanthrenes by Reductive Aromatization of Violanthrone 79

The commercially available n-type semiconductive dye Violanthrone 79 is used as starting material to synthesize via a reductive aromatization and functionalization strategy so far unexplored substituted violanthrenes. Using the low-cost reducing agents zinc and sodium dithionite in combination with suitable electrophilic trapping reagents, three violanthrenes functionalized with two pivalyloxy, trimethylsiloxy or methoxy groups are selectively obtained in high yields. Due to their octyl ether moieties, these new red dyes are highly soluble. They are characterized by means of UV-Vis and fluorescence spectroscopy and their redox properties are studied via cyclic voltammetry. The spectroscopically determined frontier molecular orbital energies are compared to those calculated by density functional theory and suggest, that electron-poor Violanthrone 79 was transformed into electron-rich violonthrenes VE1-VE3 with molecular characteristics typically observed in molecular precursors for p-type organic semiconductors.