Multi-orbital charge transfer at highly oriented organic/metal interfaces

Zamborlini, Giovanni; Lüftner, Daniel; Feng, Zhijing; Kollmann, Bernd; Puschnig, Peter; Dri, Carlo; Panighel, Mirco; Santo, Giovanni Di; Goldoni, Andrea; Comelli, Giovanni; Jugovac, Matteo; Feyer, Vitaliy; Schneidery, Claus Michael

doi:10.1038/s41467-017-00402-0

Cited by 63 publications

(97 citation statements)

References 55 publications

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“…[20,26] Interestingly,t he QAz molecule does not structurally deform on the surface,whereas in the case of TCNQ, porphyrins,o ro ther donor-acceptor blends,t he active moieties need to modify their structure to strongly bond to the surface. [2][3][4] STM provides further indirect proof for the azine linkage. Firstly,noconfigurational isomers (cis-trans forms) typical of azo-groups are found, not even at the island borders or steps, where such molecular structures might be more easily accommodated.…”

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confidence: 99%

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On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

et al. 2018

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On-surface synthesis is an emerging approach to obtain, in asingle step,precisely defined chemical species that cannot be obtained by other synthetic routes.The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices.A facile on-surface chemistry route has now been used to synthesize the strong electron-acceptor organic molecule quinoneazine directly on aC u(110) surface,v ia thermally activated covalent coupling of para-aminophenol precursors. The mechanism is described using ac ombination of in situ surface characterization techniques and theoretical methods. Owing to astrong surface-molecule interaction, the quinoneazine molecule accommodates 1.2 electrons at its carbonyl ends, inducing an intramolecular charge redistribution and leading to partial conjugation of the rings,conferring azo-character at the nitrogen sites.Organicheterostructuresbasedonelectronacceptor-donor organic molecules on surfaces have become strategic materials owing to their huge technological impact in fields such as organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs), or solar cell devices,amongst others.In electronic devices,o rganic layers are placed on metallic surfaces for electrical contact, and the structure of the metalorganic interface enormously affects the performance.[1] In particular,s ome molecules promote charge transfer at the interface with metal electrodes owing to their donor (acceptor) nature,which may induce energy level realignment that can be exploited to tune the transport properties of the system. [1][2][3][4][5] Despite the potential impact of this approach, only af ew molecules have been shown to efficiently donate (or accept) significant charge,t his quality being related to the presence of donor (acceptor) moieties in their structures.[6] A typical example is tetracyano-p-quinodimethane (TCNQ), as trong acceptor molecule that when deposited on Cu(100) accommodates around 1.6 electrons whereby almost one electron aromatizes the central hexagonal ring and the remaining fraction of the charge is accommodated in one of the peripheral nitrogen atoms of the cyano groups.[3]On the other hand, on-surface synthesis can generate unique molecules or extended molecular architectures that have been rationally formed via alternative synthetic routes to those available through solution-based chemistry. [7,8] These surface-stabilized species can lead to compounds that are difficult or impossible to obtain via conventional synthetic procedures. [9][10][11][12] Herein, we combine both of the aforementioned features. We show that the on-surface coupling reaction of two simple and inexpensive para-aminophenol (p-Ap) molecules can be employed to form aq uinonoid-like derivative,q uinoneazine (QAz). This molecule has been theoretically proposed for organic electrodes owing to their extreme redox voltages,and it can also be employed as an intermediate in the preparation of several chemically and biologically active ...

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confidence: 99%

“…[1][2][3][4][5] Despite the potential impact of this approach, only af ew molecules have been shown to efficiently donate (or accept) significant charge,t his quality being related to the presence of donor (acceptor) moieties in their structures.…”

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confidence: 99%

On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

et al. 2018

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“…Another possibility for the observed topographical differences in the STM images is that the energy distribution of the electronic states of the molecule can be different at each potential. A recent paper shows that the frontier orbitals of porphyrins are located on the macrocycle (Zamborlini et al ., ). Therefore, it is expected that the main differences observed in the STM images are confined to this region.…”

Section: Resultsmentioning

confidence: 99%

Sparse‐coding denoising applied to reversible conformational switching of a porphyrin self‐assembled monolayer induced by scanning tunnelling microscopy

Oliveira

Bragança

Alcácer

et al. 2018

Journal of Microscopy

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Scanning tunnelling microscopy (STM) was used to induce conformational molecular switching on a self-assembled monolayer of zinc-octaethylporphyrin on a graphite/tetradecane interface at room temperature. A reversible conformational change controlled by applying a tip voltage was observed. Consecutive STM images acquired at alternating tip voltages showed that at 0.4 V the porphyrin monolayer presents a molecular arrangement formed by alternate rows with two different types of structural conformations and when the potential is increased to 0.7 V the monolayer presents only one type of conformation. In this paper, we characterize these porphyrin conformational dynamics by analyzing the STM images, which were improved for better quality and interpretation by means of a denoising algorithm, adapted to process STM images from state of the art image processing and analysis methods. STM remains the best technique to 'see' and to manipulate the matter at atomic scale. A very sharp tip a few angstroms of the surface can provide images of molecules and atoms with a powerful resolution. However, these images are strongly affected by noise which is necessary to correct and eliminate. This paper is about new computational tools specifically developed to denoise the images acquired with STM. The new algorithms were tested in STM images, obtained at room temperature, of porphyrin monolayer which presents reversible conformational change in function of the tip bias voltage. Images with high resolution, acquired in real time, show that the porphyrins have different molecular arrangements whether the tip voltage is 0.4 V or 0.7 V.

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“…The latter is the case, for example, of NiTPPs adsorbed at the Cu(100) termination ( figure 16(e)). The strong molecule-surface interaction, associated with a significant charge transfer, yields the rotation of the phenyl residues, the consequent bright appearance of the peripheral, distorted terminations, and a dim molecular macrocycle, despite the presence of the central Ni atom [97]. Information about the local density of states close to the Fermi level can be obtained by means of STS, allowing distinction between metalated and non-metalated tetrapyrroles, as well as identification of possible ligands [10].…”

Section: Chemistry/biochemistry and Surface Science Absorptionmentioning

confidence: 99%

Tetrapyrroles at near-ambient pressure: porphyrins and phthalocyanines beyond the pressure gap

Vesselli

2020

J. Phys. Mater.

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Many complex mechanisms underlying the fascinating functionalities provided by tetrapyrrolic macrocycles in biochemistry have been already unraveled. Light harvesting, molecular transport, and catalytic conversion are some of the processes performed by tetrapyrrole-based centers embedded in protein pockets. The main function is determined by the single atom species that is caged in the macrocycle, while a finer tuning (band gap, chemical selectivity etc) is granted by the geometric and electronic structure of the tetrapyrrole, including its residues, and by the proximal and distal structures of the protein surroundings that exploit the molecular trans-effect and direct weak interactions, respectively. Hence, a scientific and technological challenge consists in the artificial replication of both structure and functionality of natural reaction centers in 2D ordered arrays at surfaces. Nano-architected 2D metalorganic frameworks can be indeed self-assembled under controlled conditions at supporting surfaces and, in the specific, porphyrin-and phthalocyaninebased systems have been widely investigated in ultra-high vacuum conditions by means of surface science approaches. Deep insight into the geometry, electronic structure, magnetic properties, ligand adsorption mechanisms, and light absorption has been obtained, with the strong experimental constraint of vacuum. Especially in the case of the interaction of tetrapyrroles with ligands, this limit represents a relevant gap with respect to both comparison with natural counterparts from the liquid environment and potential applicative views at both solid-liquid and solid-gas interfaces. Thus, a step forward in the direction of near-ambient pressure is strongly necessary, while maintaining the atomiclevel detail characterization accuracy. Nowadays this becomes feasible by exploiting state-of-the-art experimental techniques, in combination with computational simulations. This review focusses on the latest advances in this direction.

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Multi-orbital charge transfer at highly oriented organic/metal interfaces

Cited by 63 publications

References 55 publications

On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

Sparse‐coding denoising applied to reversible conformational switching of a porphyrin self‐assembled monolayer induced by scanning tunnelling microscopy

Tetrapyrroles at near-ambient pressure: porphyrins and phthalocyanines beyond the pressure gap

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