Addressing a lattice of rotatable molecular dipoles with the electric field of an STM tip

Abstract

Functional molecular groups mounted on specific foot structures are ideal model systems to study intermolecular interactions, due to the possibility to separate the functionality and the adsorption mechanism. Here, we...

Synthesis and Surface Behaviour of NDI Chromophores Mounted on a Tripodal Scaffold: Towards Self‐Decoupled Chromophores for Single‐Molecule Electroluminescence

“…Here we report the design, synthesis and characterisation of the three molecules Tpd‐hNDI , Tpd‐sNDI and Tpd‐nNDI (with h/s/n representing the (hetero)atom directly connected to the NDI core) as molecular emitters mounted on a tripodal scaffold as displayed in Figure 1a), together with first STM and STML studies of their (sub)monolayers obtained by spray deposition and subsequent annealing on Au(111) surfaces. While the molecular design is geared towards upright standing NDI chromophores fixed by the tripodal platform (Figure 1b), we learned in the past with model compounds comprising tetraphenylmethane based tripodal platforms about their hardly predictable surface behaviour [38,39] . Thus the scanning probe experiments enable to shed light on whether the three potential covalent sulfur gold bond of the tripodal platform dominate the monolayer formation and provide upright standing chromophores as displayed in Figure 1b), or the van der Waals attraction between the surface and the chromophore's extended π‐system dominate the molecule's surface behaviour as sketched in Figure 1c).…”

“…While the molecular design is geared towards upright standing NDI chromophores fixed by the tripodal platform (Figure 1 b), we learned in the past with model compounds comprising tetraphenylmethane based tripodal platforms about their hardly predictable surface behaviour. [ 38 , 39 ] Thus the scanning probe experiments enable to shed light on whether the three potential covalent sulfur gold bond of the tripodal platform dominate the monolayer formation and provide upright standing chromophores as displayed in Figure 1 b), or the van der Waals attraction between the surface and the chromophore's extended π‐system dominate the molecule's surface behaviour as sketched in Figure 1 c). In addition to the parent NDI structure, amino and sulfanyl groups are considered as core substituents to cover a broad range of emission wavelengths.…”

Real-space imaging of several molecular layers of C60 in the rotational glass phase

“…On terrace B (figure 3(b)) the molecules do not exhibit three-fold axes but a different symmetry of the molecular orbitals and the layer is rather rotationally disordered and some molecules appear noisy in the raw data due to swinging on the timescale of the measurement [42,43]. At this temperature, we can assume that the rotational freedom of molecules is not fully lost.…”

“…Instead of a fixed transition temperature between freezing and swinging, there is a broad range of transitions, because there is a random orientational environment of each molecule that leads to a not-well-defined energy barrier [44]. In addition, a rotational swinging of the molecules could be induced by the tunneling current [42,43]. This should be studied by varying the imaging parameters.…”

Azimuthal Dipolar Rotor Arrays on Surfaces

“…[ 16 , 17 , 18 ] A recent publication reports on molecular rotors with a dipolar head group mounted on a molecular tripod. [19] STM manipulation of the dipolar group leads to correlated motion of neighboring molecules. Ordered arrays of dipolar rotors could thus lead to the fabrication of ferroelectric materials.…”