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Although several porous carbon/graphene nanoribbons (GNRs) have been prepared, a direct comparison of the electronic properties between a nonporous GNR and its periodically perforated counterpart is still missing. Here, we report the synthesis of porous 12-atom-wide armchair-edged GNRs from a bromoarene precursor on a Au(111) surface via hierarchical Ullmann and dehydrogenative coupling. The selective formation of porous 12-GNRs was achieved through thermodynamic and kinetic reaction control combined with tailored precursor design. The structure and electronic properties of the porous 12-GNR were elucidated by scanning tunneling microscopy/spectroscopy and density functional theory calculations, revealing that the pores induce a 2.17 eV band gap increase compared to the nonporous 12-AGNR on the same surface.

Two-dimensional (2D) materials exhibit the potential to transform semiconductor technology. Their rich compositional and stacking varieties allow tailoring materials' properties toward device applications. Monolayer to multilayer gallium sulfide (GaS) with its ultraviolet band gap, which can be tuned by varying the layer number, holds promise for solar-blind photodiodes and light-emitting diodes as applications. However, achieving commercial viability requires wafer-scale integration, contrasting with established, limited methods such as mechanical exfoliation. Here the one-step synthesis of 2D GaS is introduced via metal-organic chemical vapor deposition on sapphire substrates. The pulsed-mode deposition of industry-standard precursors promotes 2D growth by inhibiting the vapor phase and on-surface pre-reactions. The interface chemistry with the growth of a Ga adlayer that results in an epitaxial relationship is revealed. Probing structure and composition validate thin-film quality and 2D nature with the possibility to control the thickness by the number of GaS pulses. The results highlight the adaptability of established growth facilities for producing atomically thin to multilayered 2D semiconductor materials, paving the way for practical applications., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Acenes represent a unique class of polycyclic aromatic hydrocarbons that have fascinated chemists and physicists due to their exceptional potential for use in organic electronics. While recent advances in on-surface synthesis have resulted in higher acenes up to dodecacene, a comprehensive understanding of their fundamental properties necessitates their expansion toward even longer homologues. Here, we demonstrate the on-surface synthesis of tridecacene via atom-manipulation-induced conformational preparation and dissociation of a trietheno-bridged precursor on a Au(111) surface. The generated tridecacene has been investigated by scanning tunneling microscopy and spectroscopy (STM/STS), combined with first-principles calculations. We observe that the STS transport gap (1.09 eV) shrinks again following the gap reopening of dodecacene (1.4 eV). Spin-polarized density functional theory calculations confirm an antiferromagnetic open-shell ground-state electronic configuration for tridecacene in the gas phase. Interestingly, tridecacene's open-shell character is significantly reduced upon interaction with the Au(111) surface despite being only physisorbed. The interaction with the surface leads to a lowering of the magnetization of tridecacene, a reduced gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), compared to the gas phase, and a reduced relative energy to the nonmagnetic state, making it nearly isoenergetic. These observations show qualitatively that the influence of the Au(111) substrate on the properties of long acenes is significant, which is important for interpreting the measured STS transport gaps. Our work contributes to a fundamental understanding of the electronic properties of long acenes, confirming a nonmonotonous length-dependent HOMO-LUMO gap, and to the development of multistep tip-assisted synthesis of elusive compounds.

We have computationally studied the formation mechanism of the biphenylene network via the intermolecular HF zipping, as well as identified key intermediates experimentally, on the Au(111) surface. We elucidate that the zipping process consists of a series of defluorinations, dehydrogenations, and C-C coupling reactions. The Au substrate not only serves as the active site for defluorination and dehydrogenation, but also forms C-Au bonds that stabilize the defluorinated and dehydrogenated phenylene radicals, leading to "standing" benzyne groups. Despite that the C-C coupling between the "standing" benzyne groups is identified as the rate-limiting step, the limiting barrier can be reduced by the adjacent chemisorbed benzyne groups. The theoretically proposed mechanism is further supported by scanning tunneling microscopy experiments, in which the key intermediate state containing chemisorbed benzyne groups can be observed. This study provides a comprehensive understanding towards the on-surface intermolecular HF zipping, anticipated to be instructive for its future applications.

Supertetrahedral chalcogenido (semi)metalate cluster-based frameworks possess high selectivity for alkali metal cations, matching the specific charge density of their inner surfaces, which enables their use as ion-exchange materials. Aggregates of the supertetrahedral chalcogenido metalate cluster offer even new perspectives for metal ion capture and separation. Herein, we report on ionothermal preparation of two corresponding model compounds, (C 2 C 1 Im) 7 [Cs@Ge II 4 (Ge IV 4 Se 10 ) 4 ] ( 1 ) and (C 2 C 1 Im) 10 [Na 5 (CN) 6 @Cu 6 (Ge 4 Se 10 ) 4 (Cu)] ( 2 ). Their formation is reliant on one specific cation type each, Cs + for 1 and Na + for 2 , thus providing promising separation potential during crystallization. Compound 1 is based on the largest discrete binary selenido germanate cluster reported to date and the first mixed-valent chalcogenido germanate(II/IV) supertetrahedron. Moreover, it adds to the few examples of chalcogenides capable of capturing Cs + ions. Its high selectivity for Cs + compared to that of Li + , Na + , K + , and Rb + was confirmed by single-crystal X-ray diffraction, energy-dispersive X-ray spectroscopy, and electrospray ionization mass spectrometry. Quantum chemical studies indicate that smaller ions, K + and Rb + , could also be embedded in an isolated cluster assembly, but as the cluster aggregate slightly distorts for crystallization, the selectivity for Cs + becomes exclusive in the salt. The anionic substructure of compound 2 is based on a two-dimensional network of supramolecular assemblies and exhibits an exclusive preference for Na + . This work thus provides the first comprehensive insight into the selective incorporation of specific alkali metal ions into supramolecular aggregates of supertetrahedral chalcogenide clusters, as a promising basis for new ion trapping techniques─especially for heavy alkali metal ions that pose environmental challenges.

Defects play a critical role for the functionality and performance of materials, but the understanding of the related effects is often lacking, because the typically low concentrations of defects make them difficult to study. A prominent case is the topological defects in two-dimensional materials such as graphene. The performance of graphene-based (opto-)electronic devices depends critically on the properties of the graphene/metal interfaces at the contacting electrodes. The question of how these interface properties depend on the ubiquitous topological defects in graphene is of high practical relevance, but could not be answered so far. Here, we focus on the prototypical Stone-Wales (S-W) topological defect and combine theoretical analysis with experimental investigations of molecular model systems. We show that the embedded defects undergo enhanced bonding and electron transfer with a copper surface, compared to regular graphene. These findings are experimentally corroborated using molecular models, where azupyrene mimics the S-W defect, while its isomer pyrene represents the ideal graphene structure. Experimental interaction energies, electronic-structure analysis, and adsorption distance differences confirm the defect-controlled bonding quantitatively. Our study reveals the important role of defects for the electronic coupling at graphene/metal interfaces and suggests that topological defect engineering can be used for performance control.

Tracing the modifications of molecules in surface chemical reactions benefits from the possibility to image their orbitals. While delocalized frontier orbitals with π character are imaged routinely with photoemission orbital tomography, they are not always sensitive to local chemical modifications, particularly the making and breaking of bonds at the molecular periphery. For such bonds, σ orbitals would be far more revealing. Here, we show that these orbitals can indeed be imaged in a remarkably broad energy range and that the plane wave approximation, an important ingredient of photoemission orbital tomography, is also well fulfilled for these orbitals. This makes photoemission orbital tomography a unique tool for the detailed analysis of surface chemical reactions. We demonstrate this by identifying the reaction product of a dehalogenation and cyclodehydrogenation reaction.

Although the exact knowledge of the binding energy of organic adsorbates on solid surfaces is of vital importance for the realization of molecular nanostructures and the theoretical modelling of molecule-substrate interactions, an experimental determination is by no means trivial. Temperature-programmed desorption (TPD) is a widely used technique that can provide such information, but a quantitative analysis requires detailed knowledge of the pre-exponential factor of desorption and is therefore rarely performed on a quantitative level for larger molecules that often exhibit notable mutual intermolecular interactions. Here, we provide a thorough anlysis of TPD data of monolayers of pentacene and perfluoropentacene adsorbed on Au(111) that serve as a model system for polycyclic aromatic hydrocarbons adsorbed on noble metal surfaces. We show that the pre-exponential factor varies by several orders of magnitude with the surface coverage and evolves in a step-like fashion due to the sudden activation of a rotational degree of freedom during thermally controlled monolayer desorption. Using complementary coverage-dependent work function measurements, the interface dipole moments were determined. This allows to identify the origin and quantify the relative contributions of the lateral intermolecular interactions, which we modelled by force field calculations. This analysis clearly shows that the main cause for intermolecular repulsion are electrostatic interactions between the intramolecular charge distributions, while interface dipoles play only a minor role.

Metal complexes at surfaces and interfaces play an important role in many areas of modern technology, including catalysis, sensors, and organic electronics. An important aspect of these interfaces is the possible exchange of the metal center, because this reaction can drastically alter the properties of the metal complex and thus of the interface. Here, we demonstrate that such metal exchange reactions are indeed possible and can proceed already at moderate temperatures even in the absence of solvents. Specifically, we studied the redox transmetalation of a monolayer of lead(ii)-tetraphenylporphyrin (PbTPP) with copper from a Cu(111) surface under ultrahigh-vacuum (UHV) conditions using multiple surface-sensitive techniques. Temperature-dependent X-ray photoelectron spectroscopy (XPS) reveals that the Pb/Cu exchange starts already below 380 K and is complete at 600 K. The identity of the reaction product, CuTPP, is confirmed by mass spectrometric detection in a temperature-programmed reaction (TPR) experiment. Scanning tunneling microscopy (STM) sheds light on the adsorbate structure of PbTPP at 300 K and uncovers the structural changes accompanying the transmetalation and side-reactions of the phenyl substituents. Moreover, individual free Pb atoms are observed as a product of the metal exchange.

Pyrene derivatives play a prominent role in organic electronic devices, including field effect transistors, light emitting diodes, and solar cells. The flexibility in the desired properties has previously been achieved by variation of substituents at the periphery of the pyrene backbone. In contrast, the influence of the topology of the central π-electron system on the relevant properties such as the band gap or the fluorescence behavior has not yet been addressed. In this work, pyrene is compared with its structural isomer azupyrene, which has a π-electron system with non-alternant topology. Using photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy, and other methods, it is shown that the electronic band gap of azupyrene is by 0.72 eV smaller than that of pyrene. The difference of the optical band gaps is even larger with 1.09 eV, as determined by ultraviolet-visible absorption spectroscopy. The non-alternant nature of azupyrene is also associated with a more localized charge distribution. Further insight is provided by density functional theory (DFT) calculations of the molecular properties and ab initio coupled cluster calculations of the optical transitions. The concept of aromaticity is used to interpret the major topology-related differences., (© 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

The quest for planar sp 2 -hybridized carbon allotropes other than graphene, such as graphenylene and biphenylene networks, has stimulated substantial research efforts because of the materials' predicted mechanical, electronic, and transport properties. However, their syntheses remain challenging given the lack of reliable protocols for generating nonhexagonal rings during the in-plane tiling of carbon atoms. We report the bottom-up growth of an ultraflat biphenylene network with periodically arranged four-, six-, and eight-membered rings of sp 2 -hybridized carbon atoms through an on-surface interpolymer dehydrofluorination (HF-zipping) reaction. The characterization of this biphenylene network by scanning probe methods reveals that it is metallic rather than a dielectric. We expect the interpolymer HF-zipping method to complement the toolbox for the synthesis of other nonbenzenoid carbon allotropes., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Acepleiadylene ( APD ), a nonbenzenoid nonalternant isomer of pyrene, exhibits different electronic properties from pyrene, but has been rarely studied since its first synthesis in 1956, probably due to the difficulties in synthesis and further derivatization. In this work, we revisited this long-known compound and developed a new two-step synthetic route to efficiently access APD on the gram scale. Theoretical and experimental characterizations elucidated the unique properties of APD as compared with its benzenoid isomer pyrene, particularly revealing its dipolar structure with a narrow optical gap. The functionalization of APD was demonstrated for the first time, providing doubly brominated APD as a key precursor for further π-extension. As a proof of concept, a π-extended APD and a cyclotrimer nanographene (C 48 H 24 ) were constructed, opening up new avenues to nonbenzenoid nanographenes with low HOMO-LUMO gaps.

Herein, we present the synthesis of two pyrene-functionalized clusters, [(R pyr Sn) 4 S 6 ]⋅2 CH 2 Cl 2 (4) and [(R pyr Sn) 4 Sn 2 S 10 ]⋅n CH 2 Cl 2 (n=4, 5 a; n=2, 5 b; R pyr =CMe 2 CH 2 C(Me)N-NC(H)C 16 H 9 ), both of which form in reactions of the organotin sulfide cluster [(R N Sn) 4 S 6 ] (C; R N =CMe 2 CH 2 C(Me)N-NH 2 ) with the well-known fluorescent dye 1-pyrenecarboxaldehyde (B). In contrast, reactions using an organotin sulfide cluster with another core structure, [(R N Sn) 3 S 4 Cl] (A), leads to formation of small molecular fragments, [(R pyr Cl 2 Sn) 2 S] (1), (pyren-1-ylmethylene)hydrazine (2), and 1,2-bis(pyren-1-ylmethylene)hydrazine (3). Besides synthesis and structures of the new compounds, we report the influence of the inorganic core on the optical properties of the dye, which was analyzed exemplarily for compound 5 a via absorption and fluorescence spectroscopy. This cluster was also used for exploring the potential of such non-volatile clusters for deposition on a metal surface under vacuum conditions., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Hybrid systems of two-dimensional (2D) materials such as transition metal dichalcogenides (TMDCs) and organic semiconductors (OSCs) have become subject of great interest for future device architectures. Although OSC-TMDC hybrid systems have been used in first device demonstrations, the precise preparation of ultra-thin OSC films on TMDCs has not been addressed. Due to the weak van der Waals interaction between TMDCs and OSCs, this requires precise knowledge of the thermodynamics at hand. Here, we use temperature-programmed desorption (TPD) and Monte Carlo (MC) simulations of TPD traces to characterize the desorption kinetics of pentacene (PEN) and perfluoropentacene (PFP) on MoS 2 as a model system for OSCs on TMDCs. We show that the monolayers of PEN and PFP are thermally stabilized compared to their multilayers, which allows preparation of nominal monolayers by selective desorption of multilayers. This stabilization is, however, caused by entropy due to a high molecular mobility rather than an enhanced molecule-substrate bond. Consequently, the nominal monolayers are not densely packed films. Molecular mobility can be suppressed in mixed monolayers of PEN and PFP that, due to intermolecular attraction, form highly ordered films as shown by scanning tunneling microscopy. Although this reduces the entropic stabilization, the intermolecular attraction further stabilizes mixed films., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We revisit the question of kekulene's aromaticity by focusing on the electronic structure of its frontier orbitals as determined by angle-resolved photoemission spectroscopy. To this end, we have developed a specially designed precursor, 1,4,7(2,7)-triphenanthrenacyclononaphane-2,5,8-triene, which allows us to prepare sufficient quantities of kekulene of high purity directly on a Cu(111) surface, as confirmed by scanning tunneling microscopy. Supported by density functional calculations, we determine the orbital structure of kekulene's highest occupied molecular orbital by photoemission tomography. In agreement with a recent aromaticity assessment of kekulene based solely on C-C bond lengths, we conclude that the π-conjugation of kekulene is better described by the Clar model rather than a superaromatic model. Thus, by exploiting the capabilities of photoemission tomography, we shed light on the question which consequences aromaticity holds for the frontier electronic structure of a π-conjugated molecule.

Ring/chain competition in oligomerization reactions represents a long-standing topic of synthetic chemistry and was treated extensively for solution reactions but is not well-understood for the two-dimensional confinement of surface reactions. Here, the kinetic and thermodynamic principles of ring/chain competition in on-surface synthesis are addressed by scanning tunneling microscopy, X-ray photoelectron spectroscopy, and Monte Carlo simulations applied to azulene-based organometallic oligomers on Cu(111). Analysis of experiments and simulations reveals how the ring/chain ratio can be controlled through variation of coverage and temperature. At room temperature, non-equilibrium conditions prevail and kinetic control leads to preferential formation of the entropically favored chains. In contrast, high-temperature equilibrium conditions are associated with thermodynamic control, resulting in increased yields of the energetically favored rings. The optimum conditions for ring formation include the lowest possible temperature within the regime of thermodynamic control and a low coverage. The general implications are discussed and compared to the solution case., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The synthesis of cycloarenes in solution is challenging because of their low solubility and the often hindered cyclodehydrogenation reaction of their nonplanar precursors. Using an alternative on-surface synthesis protocol, we achieved an unprecedented double-stranded hexagonal cycloarene containing 108 sp 2 carbon atoms. Its synthesis is based on hierarchical Ullmann coupling and cyclodehydrogenation of a specially designed precursor on a Au(111) surface. The structure and other properties of the cycloarene are investigated by scanning tunneling microscopy/spectroscopy, atomic force microscopy, and density functional theory calculations.

The binary lead fluoride Pb 3 F 8 was synthesized by the reaction of anhydrous HF with Pb 3 O 4 or by the reaction of BrF 3 with PbF 2 . The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS 19 F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

A solvent-free dilithium porphyrin was synthesized by direct reaction of free-base meso-tetraphenylporphyrin with elemental lithium in ultra-high vacuum. The reaction product dilithium tetraphenylporphyrin was studied by temperature-programmed desorption mass spectrometry (TPD-MS) and hard X-ray photoelectron spectroscopy (HAXPES). The solid-state reaction is thermodynamically favored, according to density functional theory (DFT) calculations.

Various two-dimensional (2D) carbon allotropes with nonalternant topologies, such as pentaheptites and phagraphene, have been proposed. Predictions indicate that these metastable carbon polymorphs, which contain odd-numbered rings, possess unusual (opto)electronic properties. However, none of these materials has been achieved experimentally due to synthetic challenges. In this work, by using on-surface synthesis, nanoribbons of the nonalternant graphene allotropes, phagraphene and tetra-penta-hepta(TPH)-graphene, have been obtained by dehydrogenative C-C coupling of 2,6-polyazulene chains. These chains were formed in a preceding reaction step via on-surface Ullmann coupling of 2,6-dibromoazulene. Low-temperature scanning probe microscopies with CO-functionalized tips and density functional theory calculations have been used to elucidate their structural properties. The proposed synthesis of nonalternant carbon nanoribbons from the fusion of synthetic line-defects may pave the way for large-area preparation of novel 2D carbon allotropes.

Phthalocyanines possess unique optical and electronic properties and thus are widely used in (opto)electronic devices, coatings, photodynamic therapy, etc. Extension of their π-electron systems could produce molecular materials with red-shifted absorption for a broader range of applications. However, access to expanded phthalocyanine analogues with more than four isoindoline units is challenging due to the limited synthetic possibilities. Here, we report the controlled on-surface synthesis of a gadolinium-supernaphthalocyanine macrocycle and its open-chain counterpart poly(benzodiiminoisoindoline) on a silver surface from a naphthalene dicarbonitrile precursor. Their formation is controlled by the on-surface high-dilution principle and steered by different metal templates, i.e., gadolinium atoms and the bare silver surface, which also act as oligomerization catalysts. By using scanning tunneling microscopy, photoemission spectroscopy, and density functional theory calculations, the chemical structures along with the mechanical and electronic properties of these phthalocyanine analogues with extended π-conjugation are investigated in detail.

In polymerization reactions, controlling the formation of open-chain versus cyclic product topologies is necessary because of the different properties of polymer chains and macrocycles. Here, we report a topology-selective Ullmann coupling on metal surfaces with control of the ring/chain competition. The precursor employed is 4,4''-dibromo-ortho-terphenyl (DBOTP), which features a 60° bent feature and polymerizes into zigzag polyphenylene chains on both Au(111) and Ag(111) surface via Ullmann coupling. However, the cyclotrimerization of the precursor occurs only on Ag(111) but not Au(111). It is proposed that the cyclotrimerization reaction on Au(111) is blocked, because the necessary C-C coupling of two carbon radicals with different vertical heights is unfavored. Such height difference stems from the intrinsic steric repulsion between the two ortho-substituted phenyl groups. On Ag(111), the stronger adsorbate-substrate interaction reduces the extent of the tilting of the phenyl group, resulting in a smaller height difference of the carbon radicals and consequently in the increased probability for the formation of the cyclic trimer., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Interfaces between organic semiconductors and metallic layers are ubiquitous in organic (opto-) electronic devices and can significantly influence their functionality. Here, we studied in situ prepared metal-organic interfaces, which were obtained by vapor deposition of metals (Co, Fe) onto organic semiconductor films (2H-tetraphenylporphyrin), with hard x-ray photoelectron spectroscopy. In these systems, the interphase zones, which are formed by diffusion and reaction of the metal in the organic material, can be clearly distinguished spectroscopically from the unreacted organic bulk, since they comprise the corresponding metalloporphyrins, CoTPP and FeTPP. In order to gain control over the thickness of the interphase layers, we varied process parameters such as sample temperature and metal-atom flux during interface preparation. We found that the temperature of the organic film during metal deposition was the only parameter that significantly influenced the formation of the interphase layers: their thicknesses were typically ~0.5 nm for deposition at 90 K, compared to ~1 nm at 300 K, irrespective of metal atom flux and chemical nature of the metal atom (Fe versus Co). Notably, these values are significantly smaller than the thicknesses of other metal/organics interphase regions reported in the literature.

Designing molecular organic semiconductors with distinct frontier orbitals is key for the development of devices with desirable properties. Generating defined organic nanostructures with atomic precision can be accomplished by on-surface synthesis. We use this "dry" chemistry to introduce topological variations in a conjugated poly( para-phenylene) chain in the form of meta-junctions. As evidenced by STM and LEED, we produce a macroscopically ordered, monolayer thin zigzag chain film on a vicinal silver crystal. These cross-conjugated nanostructures are expected to display altered electronic properties, which are now unraveled by highly complementary experimental techniques (ARPES and STS) and theoretical calculations (DFT and EPWE). We find that meta-junctions dominate the weakly dispersive band structure, while the band gap is tunable by altering the linear segment's length. These periodic topology effects induce significant loss of the electronic coupling between neighboring linear segments leading to partial electron confinement in the form of weakly coupled quantum dots. Such periodic quantum interference effects determine the overall semiconducting character and functionality of the chains.

We investigated the compound 1T-Cu x Ta 1-x S 2 with respect to its synthesis, homogeneity range, structure and electronic properties. The average structure of 1T-Cu x Ta 1-x S 2 resembles that of the high-temperature phase of the layered transition metal dichalcogenide 1T-TaS 2 in which tantalum is partially substituted by copper. 1T-Cu x Ta 1-x S 2 readily decomposes at elevated temperatures and can only be prepared and stabilized by a sufficiently high amount of sulfur excess. XPS and NEXAFS measurements reveal that copper has the oxidation state  +I in 1T-Cu x Ta 1-x S 2 , which is supported by quantum chemical calculations. The disorder introduced by copper doping causes an Anderson-type localization of the conduction electrons as manifested by a strong increase of the electrical resistivity and a Curie-type paramagnetism at low temperatures as in other doped systems 1T-M x Ta 1-x S 2 with higher valent metals. Quantum chemical calculations support this interpretation.

Control over the competition between an organometallic hexamer macrocycle and oligomer chains formed from the non-alternant aromatic 1,3-dibromoazulene (DBAz) precursor has been achieved in surface-assisted synthesis on a copper(111) surface. In contrast to kinetic reaction control via the high-dilution principle, the ring formation is achieved here by thermodynamic control, which is based on two-dimensional (2D) confinement and reversible bonds.

Aromatic C-H bond activation has attracted much attention due to its versatile applications in the synthesis of aryl-containing chemicals. The major challenge lies in the minimization of the activation barrier and maximization of the regioselectivity. Here, we report the highly selective activation of the central aromatic C-H bond in meta-aryne species anchored to a copper surface, which catalyzes the C-H bond dissociation. Two prototype molecules, i.e., 4',6'-dibromo- meta-terphenyl and 3',5'-dibromo- ortho-terphenyl, have been employed to perform C-C coupling reactions on Cu(111). The chemical structures of the resulting products have been clarified by a combination of scanning tunneling microscopy and noncontact atomic force microscopy. Both methods demonstrate a remarkable weakening of the targeted C-H bond. Density functional theory calculations reveal that this efficient C-H activation stems from the extraordinary chemisorption of the meta-aryne on the Cu(111) surface, resulting in the close proximity of the targeted C-H group to the Cu(111) surface and the absence of planarity of the phenyl ring. These effects lead to a lowering of the C-H dissociation barrier from 1.80 to 1.12 eV, in agreement with the experimental data.

Structural transformations of supramolecular systems triggered by external stimuli maintain great potential for application in the fabrication of molecular storage devices. Using combined ultrahigh vacuum scanning tunneling microscopy, X-ray photoemission spectroscopy, and density functional theory calculations, we observed the surface adatom mediated structural transformation from 4,4''-dibromo- m-terphenyl (DMTP)-based halogen-bonded networks to DMTP-Cu(Ag) coordination networks on Cu(111) and Ag(111) at low temperatures. The halogen-bonded networks, which were formed on Cu(111) at 97 K and on Ag(111) at 93 K, consist of intact DMTP molecules stabilized by triple Br···Br bonds. The DMTP-Cu(Ag) coordination networks form on Cu(111) at 113 K and on Ag(111) at 103 K. They contain alternatingly arranged intact DMTP molecules and Cu(Ag) adatoms stabilized by weak C-Br···Cu(Ag) coordination bonds. Annealing the DMTP-Ag structure to 333 K leads to the initiation of C-Br bond scission. This observation suggests that the DMTP-Ag coordination network represents the intermediate phase ready for dehalogenation, which is the first step of the surface Ullmann reaction.

Heptacene was generated by surface-assisted didecarbonylation of an α-diketone precursor on a Ag(111) surface. Monitoring of the surface reaction and characterization of the adsorbed heptacene was performed with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT) calculations. The surface-assisted formation of heptacene occurs around 460 K. Both the heptacene and the precursor molecules are oriented along the high-symmetry directions of the (111) surface and their molecular π systems face towards the substrate. The interaction with the Ag(111) substrate is not laterally uniform, but appears to be strongest on the central part of the molecule, in line with the expectations from Clar's rule. In the STM images, heptacene shows a dumbbell shape, which may correspond to the substantial out-of-plane deformations of heptacene on Ag(111). As revealed by DFT, the center of the molecule is closer to the surface than the outer parts. In addition, the inner rings are most affected by charge redistribution between surface and molecule. Heptacene acts as an acceptor and receives a negative charge of -0.6e from the Ag(111) surface. Since vacuum-sublimable α-diketone precursors for even larger acenes are available, the approach is promising for the on-surface synthesis of higher acene homologues such as octacene and nonacene.

Macrocycles have attracted much attention due to their specific "endless" topology, which results in extraordinary properties compared to related linear (open-chain) molecules. However, challenges still remain in their controlled synthesis with well-defined constitution and geometry. Here, we report the successful application of the (pseudo-)high-dilution method to the conditions of on-surface synthesis in ultrahigh vacuum. This approach leads to high yields (up to 84%) of cyclic hyperbenzene ([18]-honeycombene) via an Ullmann-type reaction from 4,4″-dibromo-meta-terphenyl (DMTP) as precursor on a Ag(111) surface. The mechanism of macrocycle formation was explored in detail using scanning tunneling microscopy and X-ray photoemission spectroscopy. We propose that the dominant pathway for hyperbenzene (MTP) 6 formation is the stepwise desilverization of an organometallic (MTP-Ag) 6 macrocycle, which forms via cyclization of (MTP-Ag) 6 chains under pseudo-high-dilution conditions. The high probability of cyclization on the stage of the organometallic phase results from the reversibility of the C-Ag bond. The case is different from that in solution, in which cyclization typically occurs on the stage of a covalently bonded open-chain precursor. This difference in the cyclization mechanism on a surface compared to that in solution stems mainly from the 2D confinement exerted by the surface template, which hinders the flipping of chain segments necessary for cyclization.

We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C 180 H 120 ) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.

The interface formation upon vapor deposition of a metal onto a molecular organic semiconductor was studied using a well-defined complexation reaction between a metal and a porphyrin. Specifically, metallic cobalt (Co) was vapor deposited onto a thin film of 2H-tetraphenylporphyrin (2HTPP) at room temperature. The resulting interface was probed with Hard X-ray Photoelectron Spectroscopy (HAXPES) using photon energies between 2 and 6 keV to obtain a detailed depth profile of the chemical composition. Characteristic changes in the N 1s core level signals reveal the formation of a cobalt tetraphenylporphyrin (CoTPP) layer between the Co and 2HTPP layers. Assuming an abrupt interface between CoTPP and 2HTPP (layer-by-layer model), analysis of the XPS data results in a thickness of the CoTPP reaction layer of 1.6 nm. However, a more advanced numerical analysis allowed us to reconstruct details of the actual depth distribution of the CoTPP interphase layer: up to a depth of 1.5 nm, all 2HTPP molecules were converted into CoTPP. Beyond this depth, the CoTPP concentration decreases sharply within 0.15 nm to zero.

Air-unstable magnetic aluminum phthalocyanine (AlPc) molecules are prepared by an on-surface metalation reaction of phthalocyanine with aluminum (Al) atoms on Au(111) in ultrahigh vacuum. Experiments and density functional theory calculations show that an unpaired spin is located on the conjugated isoindole lobes of the molecule rather than at the Al position.

The influences of the substrate structure on the formation of one-dimensional organometallic and covalent oligomers on a Cu(110) surface were studied using scanning tunneling microscopy (STM), X-ray photoemission spectroscopy (XPS), and low energy electron diffraction (LEED) in ultrahigh vacuum (UHV). Vapor deposition of submonolayer 4,4''-dibromo-meta-terphenyl (DMTP) onto a Cu(110) surface at 300 K leads to scission of C-Br bonds and the formation of organometallic chains (cis/trans and all-trans) connected by C-Cu-C bonds. Larger islands (120 × 120 nm(2)) of all-trans zigzag organometallic chains as sole products were obtained by the deposition of DMTP onto Cu(110) held at 383 K. The domains are oriented along two directions with an angle of ±13° relative to the [0 0 1] direction due to the two-fold symmetry of the Cu(110) surface lattice. This study reveals at a sub-molecular level that the organometallic chains firstly lose copper atoms and then undergo C-C coupling into oligophenylene chains at a substrate temperature around 417 K. Annealing the large islands of organometallic chains at 458 K results in the formation of completely C-C covalently bonded zigzag oligophenylene chains. The zigzag angle of 125° slightly deviates from the ideal value of 120°. This is attributed to a stretching of the zigzag oligophenylene chains due to substrate template effects.

The bottom-up construction of low-dimensional macromolecular nanostructures directly on a surface is a promising approach for future application in molecular electronics and integrated circuit production. However, challenges still remain in controlling the formation of these nanostructures with predetermined patterns (such as linear or cyclic) or dimensions (such as the length of one-dimensional (1D) chains). Here, we demonstrate that a high degree of structural control can be achieved by employing a Cu(110)-(2×1)O nanotemplate for the confined synthesis of organometallic chains and macrocycles. This template contains ordered arrays of alternating stripes of Cu-O chains and bare Cu, the widths of which are controllable. Using scanning tunneling microscopy and low-energy electron diffraction, we show that well-defined, ordered 1D zigzag organometallic oligomeric chains with uniform lengths can be fabricated on the Cu stripes (width >5.6 nm) of the Cu(110)-(2×1)O surface. In addition, the lengths of the meta-terphenyl (MTP)-based chains can be adjusted by controlling the widths of the Cu stripes within a certain range. When reducing the widths of Cu stripes to a range of 2.6 to 5.6 nm, organometallic macrocycles including tetramer (MTP-Cu)4, hexamer (MTP-Cu)6, and octamer (MTP-Cu)8 species are formed due to the spatial confinement effect and attraction to the Cu-O chains. An overview of all formed organometallic macrocycles on the Cu stripes with different widths reveals that the origin of the formation of these macrocycles is the cis-configured organometallic dimer (MTP)2Cu3, which was observed on the extremely narrow Cu stripe with a width of 1.5 nm.

The in situ metalation of tetraphenylporphyrin (2HTPP) with Ni on the reconstructed TiO2(110)-1 × 2 surface, resulting in the formation of adsorbed nickel(II)-tetraphenylporphyrin (NiTPP), has been investigated by synchrotron radiation photoemission spectroscopy (SRPES), scanning tunnelling microscopy (STM) and ab initio Density Functional Theory (DFT) calculations. The metalation can be realized at room temperature irrespective of the deposition order of Ni and 2HTPP, which however leads to different metalation degrees. Increasing the substrate temperature or Ni : 2HTPP ratio results in higher metalation degree, which ultimately reaches its limit at ∼85% (Ni : 2HTPP = 3 : 1) and ∼49% (Ni : 2HTPP = 1 : 1) for post- and pre-deposition of Ni, respectively. The reaction from 2HTPP to NiTPP is accompanied by changes of the molecular adsorption conformation and the adsorption site from a tilted two-lobed feature on added Ti2O3 rows to a four-lobed feature on top of troughs or cross-links of the TiO2(110)-1 × 2 surface. This interpretation of the STM data is supported by DFT-based STM simulations.

A Li4Ti5O12 (LTO) film was coated as buffer layer onto a LiNi0.5Mn1.5O4 (LNMO) high-voltage cathode, and after cycling of the cathode in a battery electrolyte, the LTO film was investigated by means of synchrotron radiation based hard X-ray photoelectron spectroscopy (HAXPES). By tuning the photon energy between 2 keV and 6 keV, we obtained non-destructive depth profiles of the coating material with probing depths ranging from 6 nm to 20 nm. The coating was found to be covered by a few nanometers thin surface layer resulting from electrolyte decomposition. This layer consisted predominantly of organic polymers as well as metal fluorides and fluorophosphates. A positive influence of the Li4Ti5O12 coating with regard to the size and stability of the surface layer was found. The coating itself consisted of a uniform mixture of Li(I), Ti(IV), Ni(II) and Mn(IV) oxides that most likely adopted a spinel structure by forming a solid solution of the two spinels LiNi0.5Mn1.5O4 and Li4Ti5O12 with Li, Mn, Ni and Ti cations mixing on the spinel octahedral sites. The diffusion of Ni and Mn ions into the Li4Ti5O12 lattice occurred during the heat treatment when preparing the cathode. The doping of Li4Ti5O12 with the open d-shell ions Ni(2+) (d(8)) and Mn(4+) (d(3)) should increase the electronic conductivity of the coating significantly, as was found in previous studies. The complex signal structure of the Ti 2p, Ni 2p and Mn 2p core levels provides insight into the chemical nature of the transition metal ions.

Carbon-based nanostructures have attracted tremendous interest because of their versatile and tunable properties, which depend on the bonding type of the constituting carbon atoms. Graphene, as the most prominent representative of the π-conjugated carbon-based materials, consists entirely of sp(2)-hybridized carbon atoms and exhibits a zero band gap. Recently, countless efforts were made to open and tune the band gap of graphene for its applications in semiconductor devices. One promising method is periodic perforation, resulting in a graphene nanomesh (GNM), which opens the band gap while maintaining the exceptional transport properties. However, the typically employed lithographic approach for graphene perforation is difficult to control at the atomic level. The complementary bottom-up method using surface-assisted carbon-carbon (C-C) covalent coupling between organic molecules has opened up new possibilities for atomically precise fabrication of conjugated nanostructures like GNM and graphene nanoribbons (GNR), although with limited maturity. A general drawback of the bottom-up approach is that the desired structure usually does not represent the global thermodynamic minimum. It is therefore impossible to improve the long-range order by postannealing, because once the C-C bond formation becomes reversible, graphene as the thermodynamically most stable structure will be formed. This means that only carefully chosen precursors and reaction conditions can lead to the desired (non-graphene) material. One of the most popular and frequently used organic reactions for on-surface C-C coupling is the Ullmann reaction of aromatic halides. While experimentally simple to perform, the irreversibility of the C-C bond formation makes it a challenge to obtain long-range ordered nanostructures. With no postreaction structural improvement possible, the assembly process must be optimized to result in defect-free nanostructures during the initial reaction, requiring complete reaction of the precursors in the right positions. Incomplete connections typically result when mobile precursor monomers are blocked from reaching unsaturated reaction sites of the preformed nanostructures. For example, monomers may not be able to reach a randomly formed internal cavity of a two-dimensional (2D) nanostructure island due to steric hindrance in 2D confinement, leaving reaction sites in the internal cavity unsaturated. Wrong connections between precursor monomers, here defined as intermolecular C-C bonds forcing the monomer into a nonideal position within the structure, are usually irreversible and can induce further structural defects. The relative conformational flexibility of the monomer backbones permits connections between deformed monomers when they encounter strong steric hindrance. This, however, usually leads to heterogeneous structural motifs in the formed nanostructures. This Account reviews some of the latest developments regarding on-surface C-C coupling strategies toward the synthesis of carbon-based nanostructures by addressing the above-mentioned issues. The strategies include Ullmann coupling and other, "cleaner" alternative C-C coupling reactions like Glaser coupling, cyclo-dehydrogenation, and dehydrogenative coupling. The choice of substrate materials and precursor designs is crucial for optimizing substrate reactivity and precursor diffusion rates, and to reduce events of wrong linkage. Hierarchical polymerization is employed to steer the coupling route, which effectively improves the completeness of the reaction. Effects of byproducts on nanostructure formation is comprehended with both experimental and theoretical studies.

The redox reaction of superoxide (KO2) with highly charged iron porphyrins (Fe(P4+), Fe(P8+), and Fe(P8-)) has been investigated in the ionic liquids (IL) [EMIM][Tf2N] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) and [EMIM][B(CN)4] (1-ethyl-3-methylimidazolium tetracyanoborate) by using time-resolved UV/vis stopped-flow, electrochemistry, cryospray mass spectrometry, EPR, and XPS measurements. Stable KO2 solutions in [EMIM][Tf2N] can be prepared up to a 15 mM concentration and are characterized by a signal in EPR spectrum at g = 2.0039 and by the 1215 cm(-1) stretching vibration in the resonance Raman spectrum. While the negatively charged iron porphyrin Fe(P8-) does not react with superoxide in IL, Fe(P4+) and Fe(P8+) do react in a two-step process (first a reduction of the Fe(III) to the Fe(II) form, followed by the binding of superoxide to Fe(II)). In the reaction with KO2, Fe(P4+) and Fe(P8+) show similar rate constants (e.g., in the case of Fe(P4+): k1 = 18.6 ± 0.5 M(-1) s(-1) for the first reaction step, and k2 = 2.8 ± 0.1 M(-1) s(-1) for the second reaction step). Notably, these rate constants are four to five orders of magnitude lower in [EMIM][Tf2N] than in conventional solvents such as DMSO. The influence of the ionic liquid is also apparent during electrochemical experiments, where the redox potentials for the corresponding Fe(III)/Fe(II) couples are much more negative in [EMIM][Tf2N] than in DMSO. This modified redox and kinetic behavior of the positively charged iron porphyrins results from their interactions with the anions of the ionic liquid, while the nucleophilicity of the superoxide is reduced by its interactions with the cations of the ionic liquid. A negligible vapor pressure of [EMIM][B(CN)4] and a sufficient enrichment of Fe(P8+) in a close proximity to the surface enabled XPS measurements as a case study for monitoring direct changes in the electronic structure of the metal centers during redox processes in solution and at liquid/solid interfaces.

Fractals, being "exactly the same at every scale or nearly the same at different scales" as defined by Benoit B. Mandelbrot, are complicated yet fascinating patterns that are important in aesthetics, mathematics, science and engineering. Extended molecular fractals formed by the self-assembly of small-molecule components have long been pursued but, to the best of our knowledge, not achieved. To tackle this challenge we designed and made two aromatic bromo compounds (4,4″-dibromo-1,1':3',1″-terphenyl and 4,4‴-dibromo-1,1':3',1″:4″,1‴-quaterphenyl) to serve as building blocks. The formation of synergistic halogen and hydrogen bonds between these molecules is the driving force to assemble successfully a whole series of defect-free molecular fractals, specifically Sierpiński triangles, on a Ag(111) surface below 80 K. Several critical points that govern the preparation of the molecular Sierpiński triangles were scrutinized experimentally and revealed explicitly. This new strategy may be applied to prepare and explore various planar molecular fractals at surfaces.

The temperature-controlled surface-assisted synthesis of halogen bonded, organometallic, and covalent nanostructures based on 1,3,5-tribromo-benzene (TriBB) was studied with scanning tunneling microscopy and X-ray photoemission spectroscopy in ultrahigh vacuum. Vapor deposition of TriBB onto a Cu(111) surface held at 90 K leads to the formation of large domains of a honeycomb-like organic monolayer structure stabilized by triangular nodes with Br⋯Br intermolecular bonds. Upon annealing the organic monolayer to ∼140 K, a new hexagonal close-packed structure with intact TriBB molecules connected by Cu adatoms is formed. Further warming up the sample to 300 K gives rise to the scission of C-Br bonds and formation of C-Cu-C bonds between phenyl fragments such that stable dendritic organometallic networks are formed. Larger islands of organometallic networks are obtained by maintaining the temperature of Cu(111) at 420 K during deposition of TriBB. Simultaneously, large islands of Br atoms are formed around the organometallic networks. Annealing the more extended organometallic network (prepared at 420 K) to 520 K leads to the formation of a branched covalent organic framework (COF) which comprises structural elements of porous graphene and is surrounded by Br islands. These organometallic networks and COFs appear as small dendritic and branched domains, most likely due to the steric influence exerted by the Br islands.

In situ metalation of tetraphenylporphyrin (2HTPP) (sub)monolayers with Ni on a TiO2(110) surface to nickel(II)-tetraphenylporphyrin (NiTPP) depends on temperature and order of deposition, and affects conformation and bonding geometry of the porphyrin.

The formation, structure, and dynamics of planar organometallic macrocycles (meta-terphenyl-Cu)n and zigzag-shaped one-dimensional organometallic polymers on a Cu(111) surface were studied with scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Vapor deposition of 4,4″-dibromo-meta-terphenyl (DMTP) onto Cu(111) at 300 K leads to C-Br bond scission and formation of C-Cu-C bonds, which connect neighboring meta-terphenyl fragments such that room-temperature stable macrocycles and zigzag chains are formed. The chains self-assemble to form islands, which are elongated in the direction of the chains. If DMTP is deposited onto Cu(111) held at 440 K, the island size is drastically increased (>200 × 200 nm(2)). STM sequences show the formation of ordered structures through reversible scission and reformation of the C-Cu-C bonds. The cyclic organometallic species such as the hexamer (meta-terphenyl-Cu)6 may represent intermediates in the surface-confined Ullmann synthesis of hydrocarbon macrocycles such as the recently discovered hyperbenzene.

Tip-enhanced Raman spectroscopy combines scanning probe techniques with Raman spectroscopy. Latest developments permit the chemical mapping of individual adsorbed molecules by monitoring molecular vibrations with sub-nanometer resolution. Increased efficiency and reduced photodegradation make this method suitable for studies of adsorbed organic and biomolecules in surface science, catalysis, biochemistry, and related fields., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A hexagonal macrocycle consisting of 18 phenylene units (hyperbenzene) was synthesized on a Cu(111) surface in ultrahigh vacuum by Ullmann coupling of six 4,4''-dibromo-m-terphenyl molecules. The large diameter of 21.3 Å and the ability to assemble in arrays makes hyperbenzene an interesting candidate for a nanotrough that could enclose metallic, semiconducting, or molecular quantum dots., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We investigated the coordination self-assembly and metalation reaction of Cu with 5,10,15,20-tetra(4-pyridyl)porphyrin (2HTPyP) on a Au(111) surface by means of scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. 2HTPyP was found to interact with Cu through both the peripheral pyridyl groups and the porphyrin core. Pairs of pyridyl groups from neighboring molecules coordinate Cu(0) atoms, which leads to the formation of a supramolecular metal-organic coordination network. The network formation occurs at room temperature; annealing at 450 K enhances the process. The interaction of Cu with the porphyrin core is more complex. At room temperature, formation of an initial complex Cu(0)-2HTPyP is observed. Annealing at 450 K activates an intramolecular redox reaction, by which the coordinated Cu(0) is oxidized to Cu(II) and the complex Cu(II)TPyP is formed. The coordination network consists then of Cu(II) complexes linked by Cu(0) atoms; that is, it represents a mixed-valence two-dimensional coordination network consisting of an ordered array of Cu(II) and Cu(0) centers. Above 520 K, the network degrades and the Cu atoms in the linking positions diffuse into the substrate, while the Cu(II)TPyP complexes form a close-packed structure that is stabilized by weak intermolecular interactions. Density functional theory investigations show that the reaction with Cu(0) proceeds via formation of an initial complex between metal atom and porphyrin followed by formation of Cu(II) porphyrin within the course of the reaction. The activation barrier of the rate limiting step was found to be 24-37 kcal mol(-1) depending on the method used. In addition, linear coordination of a Cu atom by two CuTPyP molecules is favorable according to gas-phase calculations., (© 2012 American Chemical Society)

The chemical bond between an adsorbed, laterally coordinated metal ion and a metal surface is affected by an additional axial ligand on the metal ion. This surface analogon of the trans effect was studied in detail using monolayers of various M(II)-tetraphenylporphyrins (MTTPs, M = Fe, Co, Zn) and their nitrosyl complexes on a Ag(111) surface. X-ray photoelectron spectroscopy (XPS) shows that the oxidation state of the Fe and Co (but not Zn) ions in the MTPP monolayers is reduced because of the interaction with the substrate. This partial reduction is accompanied by the appearance of new valence states in the UV photoelectron and scanning tunneling spectra (UPS and STS), revealing the covalent character of the ion-substrate bond. Subsequent coordination of nitric oxide (NO) to the metal ions (Fe, Co) reverses these surface-induced effects, resulting in an increase of the oxidation states and the disappearance of the new valence states. Removal of the NO ligands by thermal desorption restores the original spectroscopic features, indicating that the described processes are fully reversible. The NO coordination also changes the spin state and thus the magnetic properties of the metal ions. Density-functional theory (DFT) calculations on model systems provide structural and energetic data on the adsorbed molecules and the surface chemical bond. The calculations reveal that competition effects, similar to the trans effect, play a central role and lead to a mutual interference of the two axial ligands, NO and Ag, and their bonds to the metal center. These findings have important implications for sensor technology and catalysis using supported planar metal complexes, in which the activity of the metal center is sensitively influenced by the substrate.

Graphene, a truly two-dimensional and fully π-conjugated honeycomb carbon network, is currently evolving into the most promising successor to silicon in micro- and nanoelectronic applications. However, its wider application is impeded by the difficulties in opening a bandgap in its gapless band-structure, as well as the lack of processability in the resultant intrinscially insoluble material. Covalent chemical modification of the π-electron system is capable of addressing both of these issues through the introduction of variable chemical decoration. Although there has been significant research activity in the field of functionalized graphene, most work to date has focused on the use of graphene oxide. In this Article, we report on the first wet chemical bulk functionalization route beginning with pristine graphite that does not require initial oxidative damage of the graphene basal planes. Through effective reductive activation, covalent functionalization of the charged graphene is achieved by organic diazonium salts. Functionalization was observed spectroscopically, and successfully prevents reaggregation while providing solubility in common organic media.