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On‐surface synthesis has become a prominent method for growing low‐dimensional carbon‐based nanomaterials on metal surfaces. However, the necessity of decoupling organic nanostructures from metal substrates to exploit their properties requires either transfer methods or new strategies to perform reactions directly on inert surfaces. The use of on‐surface light‐induced reactions directly on semiconductor/insulating surfaces represents an alternative approach to address these challenges. Here, exploring the photochemical activity of different organic molecules on a SnSe semiconductor surface under ultra‐high vacuum, we present a novel on‐surface light‐induced reaction. The selective photodissociation of the anhydride group is observed, releasing CO and CO2. Moreover, we rationalize the relationship between the photochemical activity and the π‐conjugation of the molecular core. The different experimental behaviour of two model anhydrides was elucidated by theoretical calculations, showing how the molecular structure influences the distribution of the excited states. Our findings open new pathways for on‐surface synthesis directly on technologically relevant substrates. [ABSTRACT FROM AUTHOR]

This letter introduces an unconditionally stable finite‐difference time‐domain (FDTD) method, based on the locally one‐dimensional (LOD) technique, for the solution of the two‐dimensional scalar wave equation (WE) in homogeneous media. The second spatial derivatives in the WE are discretized by using a three‐point compact (implicit) finite‐difference formula with a free parameter. This formula has second‐order accuracy and becomes fourth‐order by properly selecting the parameter value. Moreover, the resulting algorithm only involves tridiagonal matrices, as when using standard (explicit) second‐order finite differences. Additionally, a stability analysis is performed and the numerical dispersion relation of the method is derived. The proposed compact LOD‐WE‐FDTD technique has been applied to the calculation of resonant frequencies in a metallic ridge cavity. The accuracy of the results obtained has been studied as a function of the parameter value. [ABSTRACT FROM AUTHOR]

The incorporation of non‐benzenoid motifs in graphene nanostructures significantly impacts their properties, making them attractive for applications in carbon‐based electronics. However, understanding how specific non‐benzenoid structures influence their properties remains limited, and further investigations are needed to fully comprehend their implications. Here, we report an on‐surface synthetic strategy toward fabricating non‐benzenoid nanographenes containing different combinations of pentagonal and heptagonal rings. Their structure and electronic properties were investigated via scanning tunneling microscopy and spectroscopy, complemented by computational investigations. After thermal activation of the precursor P on the Au(111) surface, we detected two major nanographene products. Nanographene Aa−a embeds two azulene units formed through oxidative ring‐closure of methyl substituents, while Aa−s contains one azulene unit and one Stone‐Wales defect, formed by the combination of oxidative ring‐closure and skeletal ring‐rearrangement reactions. Aa−a exhibits an antiferromagnetic ground state with the highest magnetic exchange coupling reported up to date for a non‐benzenoid containing nanographene, coexisting with side‐products with closed shell configurations resulted from the combination of ring‐closure and ring‐rearragement reactions (Ba−a, Ba−s, Bs‐a and Bs−s). Our results provide insights into the single gold atom assisted synthesis of novel NGs containing non‐benzenoid motifs and their tailored electronic/magnetic properties. [ABSTRACT FROM AUTHOR]

Nanocars are carbon‐based single‐molecules with a precise design that facilitates their atomic‐scale control on a surface. The rational design of these molecules is important in atomic and molecular‐scale manipulation to advance the development of molecular machines, as well as for a better understanding of self‐assembly, diffusion and desorption processes. Here, we introduce the molecular design and construction of a collection of minimalistic nanocars. They feature an anthracene chassis and four benzene derivatives as wheels. After sublimation and adsorption on an Au(111) surface, we show controlled and fast manipulation of the nanocars along the surface using the tip of a scanning tunneling microscope (STM). The mechanism behind the successful displacement is the induced dipole created over the nanocar by the STM tip. We utilized carbon monoxide functionalized tips both to avoid decomposition and accidentally picking the nanocars up during the manipulation. This strategy allowed thousands of maneuvers to successfully win the Nanocar Race II championship. [ABSTRACT FROM AUTHOR]

Atomic scale defects significantly affect the mechanical, electronic, and optical properties of π‐conjugated polymers. Here, isolated atomic‐scale defects are deliberately introduced into a prototypical anthracene‐ethynylene π‐conjugated polymer, and its local density of states is carefully examined on the atomic scale to show how individual defects modify the inherent electronic and magnetic properties of this one‐dimensional systems. Scanning tunneling and atomic force microscopy experiments, supplemented with density functional theory calculations, reveal the existence of a sharp electronic resonance at the Fermi energy around certain defects, which is associated with the formation of a local magnetic moment accompanied by substantial mitigation of the mobility of charge carriers. While defects in traditionally synthesized polymers lead to arbitrary conformations, the presented results clearly reflect the preferential formation of low dimensional defects at specific polymer sites, which may introduce the possibility of engineering macroscopic defects in surface‐synthesized conjugated polymers. [ABSTRACT FROM AUTHOR]

On‐surface synthesis has recently emerged as a powerful strategy to design conjugated polymers previously precluded in conventional solution chemistry. Here, an N‐containing pentacene‐based precursor (tetraazapentacene) is ex‐professo synthesized endowed with terminal dibromomethylene (:CBr2) groups to steer homocoupling via dehalogenation on metallic supports. Combined scanning probe microscopy investigations complemented by theoretical calculations reveal how the substrate selection drives different reaction mechanisms. On Ag(111) the dissociation of bromine atoms at room temperature triggers the homocoupling of tetraazapentacene units together with the binding of silver adatoms to the nitrogen atoms of the monomers giving rise to a N‐containing conjugated coordination polymer (P1). Subsequently, P1 undergoes ladderization at 200 °C, affording a pyrrolopyrrole‐bridged conjugated polymer (P2). On Au(111) the formation of the intermediate polymer P1 is not observed and, instead, after annealing at 100 °C, the conjugated ladder polymer P2 is obtained, revealing the crucial role of metal adatoms on Ag(111) as compared to Au(111). Finally, on Ag(100) the loss of :CBr2 groups affords the formation of tetraazapentacene monomers, which coexist with polymer P1. Our results contribute to introduce protocols for the synthesis of N‐containing conjugated polymers, illustrating the selective role of the metallic support in the underlying reaction mechanisms. [ABSTRACT FROM AUTHOR]

The synthesis of long n‐peri‐acenes (n‐PAs) is challenging as a result of their inherent open‐shell radical character, which arises from the presence of parallel zigzag edges beyond a certain n value. They are considered as π‐electron model systems to study magnetism in graphene nanostructures; being potential candidates in the fabrication of optoelectronic and spintronic devices. Here, we report the on‐surface formation of the largest pristine member of the n‐PA family, i.e. peri‐heptacene (n=7, 7‐PA), obtained on an Au(111) substrate under ultra‐high vacuum conditions. Our high‐resolution scanning tunneling microscopy investigations, complemented by theoretical simulations, provide insight into the chemical structure of this previously elusive compound. In addition, scanning tunneling spectroscopy reveals the antiferromagnetic open‐shell singlet ground state of 7‐PA, exhibiting singlet–triplet spin‐flip inelastic excitations with an effective exchange coupling (Jeff) of 49 meV. [ABSTRACT FROM AUTHOR]

The atomically precise control over the size, shape and structure of nanographenes (NGs) or the introduction of heteroatom dopants into their sp2‐carbon lattice confer them valuable electronic, optical and magnetic properties. Herein, we report on the design and synthesis of a hexabenzocoronene derivative embedded with graphitic nitrogen in its honeycomb lattice, achieved via on‐surface assisted cyclodehydrogenation on the Au(111) surface. Combined scanning tunnelling microscopy/spectroscopy and non‐contact atomic force microscopy investigations unveil the chemical and electronic structures of the obtained dicationic NG. Kelvin probe force microscopy measurements reveal a considerable variation of the local contact potential difference toward lower values with respect to the gold surface, indicative of its positive net charge. Altogether, we introduce the concept of cationic nitrogen doping of NGs on surfaces, opening new avenues for the design of novel carbon nanostructures. [ABSTRACT FROM AUTHOR]

We report on the synthesis and characterization of atomically precise one‐dimensional diradical peripentacene polymers on a Au(111) surface. By means of high‐resolution scanning probe microscopy complemented by theoretical simulations, we provide evidence of their magnetic properties, which arise from the presence of two unpaired spins at their termini. Additionally, we probe a transition of their magnetic properties related to the length of the polymer. Peripentacene dimers exhibit an antiferromagnetic (S=0) singlet ground state. They are characterized by singlet–triplet spin‐flip inelastic excitations with an effective exchange coupling (Jeff) of 2.5 meV, whereas trimers and longer peripentacene polymers reveal a paramagnetic nature and feature Kondo fingerprints at each terminus due to the unpaired spin. Our work provides access to the precise fabrication of polymers featuring diradical character which are potentially useful in carbon‐based optoelectronics and spintronics. [ABSTRACT FROM AUTHOR]

The calculation of dispersion diagrams and field patterns of metallic rectangular waveguides filled with an inhomogeneous dielectric whose permittivity varies continuously along the broad size of the guide is considered. In general, this problem has no exact solution, thus numerical techniques should be used. In this article, the pseudospectral frequency‐domain (PSFD) method is proposed to address the problem. Starting from the Helmholtz equation, a matrix eigenvalue problem is obtained by applying the collocation technique with Chebyshev polynomials as basis functions. The results obtained are compared with those calculated by the conventional finite‐difference frequency‐domain method showing that the PSFD technique provides an excellent accuracy. [ABSTRACT FROM AUTHOR]

Engineering low‐band‐gap π‐conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on‐surface synthesis protocol to overcome such difficulties and produce poly(p‐anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr2 moieties is deposited and annealed to 400 K, resulting in anthracene‐based polymers. High‐resolution nc‐AFM measurements confirm the nature of the ethynylene‐bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface‐stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design π‐conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on‐surface synthesis. [ABSTRACT FROM AUTHOR]

Molecular Machinery, Nanocars, Scanning Tunneling Microscopy, [4+2] Cycloaddition This nanomachine was able to win the Nanocar Race II championship, as reported by Jonas Björk, Emilio M. Pérez, David Écija et al. in their Research Article (e202212395). Keywords: Molecular Machinery; Nanocars; Scanning Tunneling Microscopy; [4+2] Cycloaddition EN Molecular Machinery Nanocars Scanning Tunneling Microscopy [4+2] Cycloaddition 1 1 1 01/31/23 20230201 NES 230201 B A minimalistic hydrocarbon nanocar b was synthesized, deposited on a Au(111) surface, and driven by a STM tip thanks to electrostatic interactions. [Extracted from the article]

Molecular Machinery, Nanocars, Scanning Tunneling Microscopy, [4+2] Cycloaddition Inside Cover: Design and Manipulation of a Minimalistic Hydrocarbon Nanocar on Au(111) (Angew. Keywords: Molecular Machinery; Nanocars; Scanning Tunneling Microscopy; [4+2] Cycloaddition EN Molecular Machinery Nanocars Scanning Tunneling Microscopy [4+2] Cycloaddition 1 1 1 01/31/23 20230201 NES 230201 B A minimalistic hydrocarbon nanocar b was synthesized, deposited on a Au(111) surface, and driven by a STM tip thanks to electrostatic interactions. [Extracted from the article]

Keywords: Carbon Magnetism; Open-Shell Character; Periacenes; Scanning Tunneling Microscopy; Surface Chemistry EN Carbon Magnetism Open-Shell Character Periacenes Scanning Tunneling Microscopy Surface Chemistry 1 1 1 06/01/22 20220607 NES 220607 B Die Vorstufe b 4,5,9,10-Tetrakis(3-methylnaphthalen-2-yl)pyren wurde in Lösung synthetisiert, unter Ultrahochvakuumbedingungen auf einem Au(111)-Substrat sublimiert und durch thermische Aktivierung mittels oberflächenunterstützter oxidativer Ringschluss- und Cyclodehydrierungsreaktionen in das Periheptacen-Molekül umgewandelt. Carbon Magnetism, Open-Shell Character, Periacenes, Scanning Tunneling Microscopy, Surface Chemistry Einzelheiten zu dieser Forschung finden sich in der Zuschrift von José I. Urgel, Pavel Jelínek, Xinliang Feng, David Écija et al. (e202114983). [Extracted from the article]

Details of this research can be found in the Communication by José I. Urgel, Pavel Jelínek, Xinliang Feng, David Écija, and co-workers (e202114983). Keywords: Carbon Magnetism; Open-Shell Character; Periacenes; Scanning Tunneling Microscopy; Surface Chemistry EN Carbon Magnetism Open-Shell Character Periacenes Scanning Tunneling Microscopy Surface Chemistry 1 1 1 06/01/22 20220607 NES 220607 B The precursor b 4,5,9,10-tetrakis(3-methylnaphthalen-2-yl)pyrene is synthesized in solution, sublimed on an Au(111) substrate under ultrahigh vacuum conditions, and converted into the I peri i -heptacene molecule by thermal activation via surface-assisted oxidative ring-closure and cyclodehydrogenation reactions. Carbon Magnetism, Open-Shell Character, Periacenes, Scanning Tunneling Microscopy, Surface Chemistry. [Extracted from the article]

This paper studies the stability and numerical dispersion of an extension of the original finite-difference time-domain (FDTD) method to incorporate magnetized ferrites. This extension is based on discretizing the ferrite equations by means of central differences and averages. Both partially magnetized and saturated ferrites are considered. With the aim of studying the numerical features of the resulting FDTD algorithms, we have considered the propagation of plane-waves along longitudinally magnetized ferrite materials. This is a simple 1D problem that enables the numerical properties of the algorithms to be studied analytically. A von Neumann stability analysis shows that the stability condition of the original FDTD method is preserved and that the algorithms do not exhibit numerical dissipation. The accuracy of the numerical results is not deteriorated with respect to those obtained in the demagnetized case. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A TLM model suitable to simulate the propagation of electromagnetic waves in Tellegen media is presented. The angle tilt between electromagnetic field vectors, the intrinsic impedances and the effective parameters of the medium are computed. The results for a monochromatic source are in very good agreement with the analytical solution. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 438–441, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11404 [ABSTRACT FROM AUTHOR]

The accurate time-domain simulation of the nonlinear dynamics of circuits containing distributed elements is of great interest. Specially at high frequencies, it is essential to consider phenomena, such as crosstalk, packaging effects, and electromagnetic interaction between active and passive elements. These effects are mainly due to the distribute components of the circuit. Therefore, the accuracy in the instability or oscillation analysis of nonlinear circuits is often limited by the models used for such elements. Commercial simulators based on the equivalent-circuit approach hardly take into account the mentioned effects. In this work, the finite-difference time-domain (FDTD) method is applied to the nonlinear simulation of a diode-based microstrip circuit exhibiting a parametric frequency division by two. The FDTD method rigorously solves Maxwell's curl equations in the time domain providing a full-wave characterization of the distributed elements of the circuit. In the example considered, a relatively low operating frequency has been selected to allow a reliable comparison between the results obtained by the proposed technique and those provided by a circuit-based commercial simulator. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1300–1302, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23352 [ABSTRACT FROM AUTHOR]

In this paper, a novel TLM algorithm for electromagnetic wave propagation in chiral media is presented. One of the main characteristics of the electromagnetic response of such media is the rotation of the polarization plane. The obtained TLM results for a monochromatic source are compared with the theoretical solution, and very good agreement is achieved. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 180–182, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20937 [ABSTRACT FROM AUTHOR]

© 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1132, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23280 [ABSTRACT FROM AUTHOR]