Monolayer Phases of a Dipolar Perylene Derivative on Au(111) and Surface Potential Build-Up in Multilayers

Abstract

9-(Bis-p-tert-octylphenyl)-amino-perylene-3,4-dicarboxy anhydride (BOPA-PDCA) is a strongly dipolar molecule representing a group of asymmetrically substituted perylenes that are employed in dye-sensitized solar cells and hold great promise for discotic liquid crystal applications. Thin BOPA-PDCA films with orientated dipole moments can potentially be used to tune the energy-level alignment in electronic devices and store information. To help assessing these prospects, we here elucidate the molecular self-assembly and electronic structure of BOPA-PCDA employing room temperature scanning tunneling microscopy and spectroscopy in combination with ultraviolet and X-ray photoelectron spectroscopies. BOPA-PCDA monolayers on Au(111) exclusively form in-plane antiferroelectric phases. The molecular arrangements, the increase of the average number of molecules per unit cell via ripening, and the rearrangement upon manipulation with the STM tip indicate an influence of the dipole moment on the molecular assembly and the rearrangement. A slightly preferred out-of-plane orientation of the molecules in the multilayer induces a surface potential of 1.2 eV. This resembles the giant surface potential effect that was reported for vacuum-deposited tris(8-hydroxyquinoline)aluminum and deemed applicable for data storage. Notably, the surface potential in the case of BOPA-PDCA can in part be reversibly removed by visible light irradiation.

Scanning Tunneling Microscope Tip-Induced Formation of a Supramolecular Network of Terarylene Molecules on Cu(111)

“…The tunneling current during scanning does not seem to affect the stable assemblies as there are no spontaneous changes in the assembly during scanning of the islands (Figure 3a−c). This is unlike the observation by Niederhausen et al, in which a dipolar perylene derivative (with a large dipole moment of 12 D) undergoes phase changes while scanning, 18 nor that of Li et al, in which hot electrons induce the formation of assemblies. 19 The dipole moment (2.1 D) of the terarylene is large enough to be influenced by the 3 V electric field induced 1 nm away but weak enough not to be affected during scans at −1 V when the tip is close to the surface.…”

“…A couple of recent works come close to this, but the ordering of assemblies was induced by hot tunneling electrons. In one, the hot electrons coming from the STM tip to the surface were shown to induce surface phase changes of an assembly of a dipolar perylene derivative, 18 while, in another, transition from disordered to an ordered assembly was induced by injecting hot electrons onto the surface. 19 In this study, we investigate the formation of on-surface molecular networks of a diarylethene derivative.…”

Subtle Fluorination of Conjugated Molecules Enables Stable Nanoscale Assemblies on Metal Surfaces

“…By nature, these comprise intramolecular polar bonds. Therefore, electrostatic dipole and multipole interactions play an important role in structure formation. , Likewise, hydrogen bonds can be a dominant factor in molecular self-assembly. , In addition to these interactions of permanent charges, mutual polarization and dispersion interactions contribute substantially. All of these are particularly important for molecules on solid surfaces such as metals, as the pairwise interaction magnitude may vary considerably for molecule–molecule and molecule–substrate. , Yet, predicting the self-assembled structure for a given material combination, based on a known molecular and substrate structure, remains one of the major challenges, as a reliable hierarchical ranking of the governing interaction energies based on empirical knowledge is not sufficiently possible.…”

Chirality in porous self-assembled monolayer networks at liquid/solid interfaces: induction, reversion, recognition and transfer

“…However, only a few such studies have been reported for densely packed double layers grown using chiral molecules bearing twisted or helical backbones such as rubrene 63 and helices 64,65 under UHV condition and alkyl-substituted amino acid derivatives at the liquid/solid interface, 66 in contrast to much more abundant studies on self-assembled bi-and multilayer formation without specific registry through π-π stacking or dipolar interactions. [67][68][69][70][71] For porous bilayer networks grown by self-assembly of acyclic building blocks, chirality did not take part, since only achiral bilayers were known. 72,73 In this connection, to shed light on the possibility of stereocontrolled epitaxial growth of porous SAMNs, we designed cDBA-OC6-OH(S) and its enantiomer cDBA-OC6-OH(R) (Chart 1) bearing hydroxy groups at the stereogenic centres.…”