Coverage- and temperature-induced self-metalation of tetraphenyltransdibenzoporphyrin on Cu(111).

We have investigated the adsorption and self-metalation of free-base tetraphenyltransdibenzoporphyrin (2H-TPtdBP) on Cu(111) as a function of coverage and temperature using scanning tunneling microscopy, x-ray photoelectron spectroscopy, temperature programmed desorption, and density-functional theory calculations. At low coverages (<0.16 molecules nm), we observe isolated individual molecules with an inverted conformation and no self-metalation up to 363 K.

β--Fused pyrene-porphyrin scaffolds with panchromatic absorption features.

The π-extension of porphyrins with pyrenes through the β--fusion of five-membered rings is demonstrated. Three architectures resulting from combining up to two porphyrins and pyrenes were obtained straightforwardly in good overall yields. Although significantly planarized, the molecules retain excellent solubility and processability.

Manifold-Fused Porphyrin-Nanographene Conjugates.

A library of novel π-extended porphyrin-hexabenzocoronene (HBC) architectures is presented. Two distinct synthetic pathways were utilized to obtain either phenyl- or HBC-fused compounds. Absorption experiments reveal the species' exciting photophysical and optoelectronic properties.

Fused Hexabenzocoronene-Porphyrin Conjugates with Tailorable Excited-State Lifetimes.

A new clear-cut strategy for fusing N-heterocyclic and carbon-pure systems is introduced en route to a versatile platform of multi-purpose tetrapyrrolic chromophores. In particular, three novel C-C bond-fused porphyrin-hexabenzocoronene (HBC) conjugates were synthesized under oxidative cyclodehydrogenation conditions, starting from tailor-made nickel porphyrin precursors. The fusion of the individual aromatic systems via 5-membered rings led to highly soluble π-extended porphyrins in excellent yields.

Experimental and Theoretical Structure Elucidation of the [2 : 1] Complex Ion of Carbo[n]helicene with n=6, 7 and 8 and Ag.

The front cover artwork illustrates the competition of [6]-, [7]- and [8]helicene for attaining a silver(I) cation. This struggle takes place in the electrospray process during solvent evaporation, leading to the well-known tweezer-like surrounding of Ag by the helicene in the [1:1] complex. In this competition, the larger helicenes outperform the smaller ones.

Structure and Conformation of Individual Molecules upon Adsorption of a Mixture of Benzoporphyrins on Ag(111), Cu(111), and Cu(110) Surfaces.

The front cover artwork is provided by the groups of Prof. Dr. Hans-Peter Steinrück and Prof.

Experimental and Theoretical Structure Elucidation of the [2 : 1] Complex Ion of Carbo[n]helicene with n=6, 7 and 8 and Ag.

Gas-phase complexes of [n]helicenes with n=6, 7 and 8 and the silver(I) cation are generated utilizing electrospray ionization mass spectrometry (ESI-MS). Besides the well-established [1 : 1] helicene/Ag -complex in which the helicene provides a tweezer-like surrounding for the Ag , there is also a [2 : 1] complex formed. Density functional theory (DFT) calculations in conjunction with energy-resolved collision-induced dissociation (ER-CID) experiments reveal that the second helicene attaches via π-π stacking to the first helicene, which is part of the pre-formed [1 : 1] tweezer complex with Ag .

Time-resolved imaging and analysis of the electron beam-induced formation of an open-cage metallo-azafullerene.

The visualization of single-molecule reactions provides crucial insights into chemical processes, and the ability to do so has grown with the advances in high-resolution transmission electron microscopy. There is currently a limited mechanistic understanding of chemical reactions under the electron beam. However, such reactions may enable synthetic methodologies that cannot be accessed by traditional organic chemistry methods.

Structure and Conformation of Individual Molecules upon Adsorption of a Mixture of Benzoporphyrins on Ag(111), Cu(111), and Cu(110) Surfaces.

We investigated the adsorption behavior of a mixture of six 2H-tetrakis-(3, 5-di-tert-butylphenyl)(x)benzoporphyrins (2H-diTTBP(x)BPs, x=0, 1, 2-cis, 2-trans, 3, and 4) on Ag(111), Cu(111) and Cu(110) at room temperature by scanning tunneling microscopy (STM) under ultra-high vacuum conditions. On Ag(111), we observe an ordered two-dimensional square phase, which is stable up to 400 K. On Cu(111), the same square phase coexists with a stripe phase, which disappears at 400 K.

Superhelicenes in the gas phase: experimental and computational evidence of stable radical cation dimers.

Electrospray-ionization mass spectrometry (ESI-MS) readily produces stable radical cation π-dimers of the superhelicenes. Energy-resolved collision experiments reveal the dissociation of the dicationic dimer into two singly charged superhelicenes. DFT calculations indicate that open-shell dications composed of two radical cations are thermochemically more attractive than the closed-shell dimer formed by a doubly charged and a neutral superhelicene.

Probing Charge Management across the π-Systems of Nanographenes in Regioisomeric Electron Donor-Acceptor Architectures.

Inspired by light-induced processes in nature to mimic the primary events in the photosynthetic reaction centers, novel functional materials combine electron donors and acceptors, i.e., (metallo)porphyrins (ZnP) and fullerenes (C), respectively, with emerging materials, i.

Panchromatic light funneling through the synergy in hexabenzocoronene-(metallo)porphyrin-fullerene assemblies to realize the separation of charges.

Here, we present a novel butadiyne-linked HBC-ethynyl-porphyrin dimer, which exhibits in the ground state strong absorption cross sections throughout the UV and visible ranges of the solar spectrum. In short, a unidirectional flow of excited state energy from the HBC termini to the (metallo)porphyrin focal points enables concentrating light at the latter. Control over excitonic interactions within, for example, the electron-donating porphyrin dimers was realized by complexation of bidentate ligands to set up panchromatic absorption that extends all the way into the near-infrared range.

Wet-Chemically Prepared Porphyrin Layers on Rutile TiO(110).

Porphyrins are large organic molecules that are interesting for different applications, such as photovoltaic cells, gas sensors, or in catalysis. For many of these applications, the interactions between adsorbed molecules and surfaces play a crucial role. Studies of porphyrins on surfaces typically fall into one of two groups: (1) evaporation onto well-defined single-crystal surfaces under well-controlled ultrahigh vacuum conditions or (2) more application-oriented wet chemical deposition onto less well-defined high surface area surfaces under ambient conditions.

Four-Step Domino Reaction Enables Fully Controlled Non-Statistical Synthesis of Hexaarylbenzene with Six Different Aryl Groups*.

Hexaarylbenzene (HAB) derivatives are versatile aromatic systems playing a significant role as chromophores, liquid crystalline materials, molecular receptors, molecular-scale devices, organic light-emitting diodes and candidates for organic electronics. Statistical synthesis of simple symmetrical HABs is known via cyclotrimerization or Diels-Alder reactions. By contrast, the synthesis of more complex, asymmetrical systems, and without involvement of statistical steps, remains an unsolved problem.

A Singular Molecule-to-Molecule Transformation on Video: The Bottom-Up Synthesis of Fullerene C from Truxene Derivative CH.

Singular reaction events of small molecules and their dynamics remain a hardly understood territory in chemical sciences since spectroscopy relies on ensemble-averaged data, and microscopic scanning probe techniques show snapshots of frozen scenes. Herein, we report on continuous high-resolution transmission electron microscopic video imaging of the electron-beam-induced bottom-up synthesis of fullerene C through cyclodehydrogenation of tailor-made truxene derivative (CH), which was deposited on graphene as substrate. During the reaction, CH transformed in a multistep process to fullerene C.

A Family of Superhelicenes: Easily Tunable, Chiral Nanographenes by Merging Helicity with Planar π Systems.

We designed a straightforward synthetic route towards a full-fledged family of π-extended helicenes: superhelicenes. They have two hexa-peri-hexabenzocoronenes (HBCs) in common that are connected via a central five-membered ring. By means of structurally altering this 5-membered ring, we realized a versatile library of molecular building blocks.

On the photophysics of nanographenes - investigation of functionalized hexa--hexabenzocoronenes as model systems.

In this study, we report on hexa-peri-hexabenzocoronenes (HBCs) as representative models for nanographenes. To this end, we synthesized a family of functionalized HBCs and investigated the impact of the substituents on the π-extended systems of the HBCs. DFT and TD-DFT calculations suggested a charge transfer character, which intensified as the electron density withdrawing effects of the substituents (-M-effect) increased.

Metalation of 2HTCNPP on Ag(111) with Zn: Evidence for the Sitting atop Complex at Room Temperature.

We study the interaction and metalation reaction of a free base 5,10,15,20-terakis(4-cyanophenyl)porphyrin (2HTCNPP) with post-deposited Zn atoms and the targeted reaction product Zn-5,10,15,20-terakis(4-cyanophenyl)porphyrin (ZnTCNPP) on a Ag(111) surface. The investigations are performed with scanning tunneling microscopy at room temperature after Zn deposition and subsequent heating. The goal is to obtain further insights in the metalation reaction and the influence of the cyanogroups on this reaction.

Pyridinic Nanographenes by Novel Precursor Design.

In this work we present the solution-synthesis of pyridine analogues to hexa-peri-hexabenzocoronene (HBC)-which might be called superpyridines-via a novel precursor design. The key step in our strategy was the pre-formation of the C-C bonds between the 3/3' positions of the pyridine and the adjacent phenyl rings-bonds that are otherwise unreactive and difficult to close under Scholl-conditions. Apart from the synthesis of the parent compound we show that classical pyridine chemistry, namely oxidation, N-alkylation and metal-coordination is applicable to the π-extended analogue.

A Functional Hexaphenylbenzene Library Comprising of One, Three, and Six Peripheral Rylene-Diimide Substituents.

Synthesis and characterization of a series of rylene-diimide substituted hexaphenylbenzenes (HPBs) is presented. The direct connection of the rylene-diimide units to the HPBs via the imide-N-position without any linkers as well as the use of naphthalene-diimides (NDIs) next to perylene-diimides (PDIs) is unprecedented. While mono-substituted products were obtained by imidization reactions with amino-HPB and the respective rylene-monoimides, key step for the formation of tri- and hexa-substituted HPBs is the Co-catalysed cyclotrimerization.

500-Fold Amplification of Small Molecule Circularly Polarised Luminescence through Circularly Polarised FRET.

Strongly dissymmetric circularly polarised (CP) luminescence from small organic molecules could transform a range of technologies, such as display devices. However, highly dissymmetric emission is usually not possible with small organic molecules, which typically give dissymmetric factors of photoluminescence (g ) less than 10 . Here we describe an almost 10 -fold chiroptical amplification of a π-extended superhelicene when embedded in an achiral conjugated polymer matrix.

Hexa--hexabenzocoronene decorated with an allenylidene ruthenium complex - almost a flyswatter.

Carbon-rich ruthenium allenylidene complexes bearing either a hexaarylbenzene (HAB) or a hexa-peri-hexabenzocoronene (HBC) substituent were synthesised. This was achieved via the corresponding propargyl alcohols with HAB and HBC substituents, which were accessible via 3 or 4 step reaction cascades. Reaction of the propargyl alcohols HC[triple bond, length as m-dash]C(OH)Ph(HAB) and HC[triple bond, length as m-dash]C(OH)Ph(HBC) with [RuCl(η5-C5H5)(PPh3)2] yielded the complexes [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C(HAB)(Ph))(PPh3)2]PF6 and [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C(HBC)(Ph))(PPh3)2]PF6.

Gas-Phase Transformation of Fluorinated Benzoporphyrins to Porphyrin-Embedded Conical Nanocarbons.

Geodesic nitrogen-containing graphene fragments are interesting candidates for various material applications, but the available synthetic protocols, which need to overcome intrinsic strain energy during the formation of the bowl-shaped skeletons, are often incompatible with heteroatom-embedded structures. Through this mass spectrometry-based gas-phase study, we show by means of collision-induced dissociation experiments and supported by density functional theory calculations, the first evidence for the formation of a porphyrin-embedded conical nanocarbon. The influences of metalation and functionalization of the used tetrabenzoporphyrins have been investigated, which revealed different cyclization efficiencies, different ionization possibilities, and a variation of the dissociation pathway.

Formation of Highly Ordered Molecular Porous 2D Networks from Cyano-Functionalized Porphyrins on Cu(111).

We investigated the adsorption of three related cyano-functionalized tetraphenyl porphyrin derivatives on Cu(111) by scanning tunneling microscopy (STM) in ultra-high vacuum (UHV) with the goal to identify the role of the cyano group and the central Cu atom for the intermolecular and supramolecular arrangement. The porphyrin derivatives studied were Cu-TCNPP, Cu-cisDCNPP, and 2H-cisDCNPP, that is, Cu-5,10,15,20-tetrakis-(p-cyano)-phenylporphyrin, Cu-meso-cis-di(p-cyano)-phenylporphyrin and 2H-meso-cis-di(p-cyano)-phenylporphyrin, respectively. Starting from different structures obtained after deposition at room temperature, all three molecules form the same long-range ordered hexagonal honeycomb-type structure with triangular pores and three molecules per unit cell.

Investigations of Low-Symmetrical Tetraaryltetrabenzoporphyrins Produced by Mixed Condensation Reactions.

Within the past decade, tetraaryltetrabenzoporphyrins (TATBPs) have gained rising attention due to their potential in various fields of materials science and medicinal chemistry. However, this class of compounds still lacks in structural diversity, especially in the case of low-symmetrical compounds. Herein, mixed condensations were utilized to generate TATBPs with different substituents either in the -positions or the periphery of the macrocycle with total yields of 55-58%.