The use of molecular materials in solar cells and nano‐electronics demands a fundamental understanding and control of their electronic properties. Particularly relevant is the molecular response to the environment, that is, the interaction with the support and adjacent molecules, as well as the influence of electrostatic gating. Here, the control of molecular level alignment and charge states of fluorinated cobalt phthalocyanines (F16CoPc) on atomically thin hexagonal boron nitride (h‐BN) sheets on Cu(111) is reported using scanning tunneling microscopy (STM) and spectroscopy (STS), as well as atomic force microscopy (AFM) and complementary density functional theory (DFT) calculations. Three parameters that govern the electronic level alignment of F16CoPc orbitals are investigated: i) template‐induced gating by the work function variation of the h‐BN/Cu(111) substrate, ii) gating by the STM tip, and iii) screening by neighboring molecules. The interplay of these parameters influences the charge distribution in the studied molecular arrangements and thus provides the possibility to tune their physicochemical behavior, for instance, the response toward electronic or optical excitation, charge transport, or binding of axial adducts.

We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n-band material.

Actinide-based metal−organic complexes and coordination architectures encompass intriguing properties and functionalities but are still largely unexplored on surfaces. We introduce the in situ synthesis of actinide tetrapyrrole complexes under ultrahighvacuum conditions, on both a metallic support and a 2D material. Specifically, exposure of a tetraphenylporphyrin (TPP) multilayer to an elemental beam of thorium followed by a temperatureprogrammed reaction and desorption of surplus molecules yields bis(porphyrinato)thorium (Th(TPP) 2 ) assemblies on Ag(111) and hexagonal boron nitride/Cu(111). A multimethod characterization including X-ray photoelectron spectroscopy, scanning tunneling microscopy, temperature-programmed desorption, and complementary density functional theory modeling provides insights into conformational and electronic properties. Supramolecular assemblies of Th(TPP) 2 as well as individual double-deckers are addressed with submolecular precision, e.g., demonstrating the reversible rotation of the top porphyrin in Th(TPP) 2 by molecular manipulation. Our findings thus demonstrate prospects for actinide-based functional nanoarchitectures.

We report a low-temperature scanning tunneling microscopy investigation of the in-situ growth of gadolinium phthalocyaninato complexes by combined deposition of free-base phthalocyanines and gadolinium atoms on a smooth Ag(111) substrate. A careful control of the stoichiometry allows the expression of a multilevel structurecomposed of irregularly distributed Gd x-1 (Pc) x complexes, x = 2-5, thus paving new avenues for surfaceconfined columnar growth.Tetrapyrrole compounds such as porphyrins and phthalocyanines are functional pigments that have attracted much interest in the last decades due to their importance in biology and technology. [1] Specifically, phthalocyanines (Pcs) are attractive synthetic molecules for nanotechnology [2][3][4][5] presenting an appealing variety of functional properties in pigments, organic solar cells and optoelectronics. [6] In the last decade, scanning tunneling microscopy (STM) as well as scanning tunneling spectroscopy (STS) techniques have facilitated the study and characterization with atomic-scale precision of the assembly and electronic properties of such compounds. [7][8][9][10][11][12][13][14][15] Contemporarily, the successful synthesis of phthalocyanine sandwich-type double and triple-decker lanthanide complexes reveals distinctive features that cannot be achieved for their non-sandwich analogues, i. e., single-molecule magnetism and axial molecular rotation. On one hand, rare-earth metal atoms promote octa-coordinated sandwich-type complexes [16][17][18][19][20][21] that have been recently under the spotlight due to the large magnetic moment and anisotropy [22,23] of the lanthanide elements, which results in the expression of single molecular magnetism, [24][25][26][27][28][29] thus with great potential for organic fieldeffect transistors, [30] molecular magnets, [26] chemical sensors and liquid crystals, [31] and single-molecule qubits. Steered by these functionalities, surface science studies have addressed the sublimation, self-assembly, electronic and magnetic properties of such compounds when deposited on surfaces. [17,22,23,[32][33][34][35][36][37][38][39] On the other hand, surface-confined multi-decker species have revealed their capability to be used as axial molecular rotors, [40][41][42][43] while simultaneously introducing columnar growth on surfaces, though limited to triple-deckers. [18] In this work, we demonstrate the formation of homoleptic gadolinium phthalocyaninato complexes, up to stacked penta (phthalocyaninato) species, on a smooth Ag(111) substrate under ultra-high-vacuum (UHV) conditions. Figure 1a shows a large-scale high-resolution STM image after deposition of 0.02 ML of Gd atoms onto a precursor multilayer of phthalocyanine species and subsequent annealing to 550 K on the Ag(111) substrate. Herein, three molecular layers of different apparent heights are recognized. A detailed analysis of the first-layer reveals four-lobed species attributed to 2HÀ Pc molecular entities with a two-fold symmetry, D 1 axis deviating by 3°from the close packed ...

On-surface synthesis made the fabrication of extended, atomically precise π-conjugated nanostructures on solid supports possible, with graphene nanoribbons (GNRs) and porphyrin-derived oligomers standing out. To date, examples combining these two prominent material classes are scarce, even though the chemically versatile porphyrins and the atomistic details of the nanographene spacers promise an easy tunability of structural and functional properties of the resulting hybrid structures. Here, we report the on-surface synthesis of extended benzenoid- and nonbenzenoid-coupled porphyrin–graphene nanoribbon hybrids by sequential Ullmann-type and cyclodehydrogenation reactions of a tailored Zn­(II) 5,15-bis­(5-bromo-1-naphthyl)­porphyrin (Por­(BrNaph)2) precursor on Au(111) and Ag(111). Using bond-resolved noncontact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM), we characterize the structures of reaction intermediates and products in detail and provide insight into the effects of the annealing protocol. We further demonstrate the stability and rigidity of the extended one-dimensional porphyrin–GNR oligomers by employing an STM-based manipulation procedure, which allows for spectroscopic measurement upon lifting.