Heteroatom-Doped Perihexacene from a Double Helicene Precursor: On-Surface Synthesis and Properties

Abstract

We report on the surface-assisted synthesis and spectroscopic characterization of the hitherto longest periacene analogue with oxygen-boron-oxygen (OBO) segments along the zigzag edges, that is, a heteroatom-doped perihexacene 1. Surface-catalyzed cyclodehydrogenation successfully transformed the double helicene precursor 2, i.e., 12a,26a-dibora-12,13,26,27-tetraoxa-benzo[1,2,3-hi:4,5,6-h'i']dihexacene, into the planar perihexacene analogue 1, which was visualized by scanning tunneling microscopy and noncontact atomic force microscopy. X-ray photoelectron spectroscopy, Raman spectroscopy, together with theoretical modeling, on both precursor 2 and product 1, provided further insights into the cyclodehydrogenation process. Moreover, the nonplanar precursor 2 underwent a conformational change upon adsorption on surfaces, and one-dimensional self-assembled superstructures were observed for both 2 and 1 due to the presence of OBO units along the zigzag edges.

Functionalization of nanostructured gold substrates with chiral chromophores for SERS applications: The case of 5‐Aza[5]helicene

“…The off-resonance Raman spectrum of solid 1, reported in Figure 3, shows the typical structured G and D features observed in other helicenes 40,41 and related graphene molecules. 39,42 As reported in Figure 4, good quality SERS spectra can be promptly detected from the functionalized Au substrates illuminated with 785-nm laser excitation. The expected G and D signals of the aza [5]helicene moiety, with good signal to noise ratios, can be detected even with small integration times, of the order of 30 seconds.…”

“…The off‐resonance Raman spectrum of solid 1 , reported in Figure , shows the typical structured G and D features observed in other helicenes and related graphene molecules …”

“…Vibrational wave numbers of the normal modes of each model were obtained and analyzed in correspondence of each optimized geometry. Raman spectra were generated, and frequencies were scaled with a 0.98 scaling factor …”

Spiers Memorial Lecture : Carbon nanostructures by macromolecular design – from branched polyphenylenes to nanographenes and graphene nanoribbons

“…124 The interaction between the π-system and the metal appears to favour the planarization. One can thus change the course of a reaction in a solution by immobilizing a precursor on a surface and, more importantly, obtain access to molecular structures that cannot be made or are too unstable in solution, such as extended acenes, 125,126 peripentacene, 127,128 and triangulenes. [129][130][131] NGs thus appear to be ideal model cases for the new chemistry of GNRs.…”

Boron–Nitrogen‐Doped Nanographenes: A Synthetic Tale from Borazine Precursors

“…The dopingo fp olycyclic aromatic hydrocarbons (PAHs) is currently emerging as one of the most promising approaches to tailor the optoelectronic properties of organic semiconductors. [1][2][3][4] The substitution of C=Cb onds with isoelectronic and isostructural dipolar boron-nitrogen (BN) [5][6][7] andb oronoxygen (BO) [8][9][10][11] couples is an efficient method to gain control of the HOMO-LUMO bandgap withouts ignificant structural modifications of the molecular scaffold. [12,13] The use of polar BN and BO bonds typicallyw iden the HOMO-LUMO gap [14,15] and imparts dipole-driven self-assembly behaviors in the solid state [3,16] ando ns urfaces.…”