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279 results on '"Stará, Irena G."'

1. Mechanical Tuning of Conductance and Thermopower in Helicene Molecular Junctions

Author

Vacek, Jaroslav, Chocholousová, Jana Vacek, Stará, Irena G., Starý, Ivo, and Dubi, Yonatan

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Helicenes are inherently chiral polyaromatic molecules composed of all-ortho fused benzene rings possessing a spring-like structure. Here, using a combination of density functional theory and tight-binding calculations, it is demonstrated that controlling the length of the helicene molecule by mechanically stretching or compressing the molecular junction can dramatically change the electronic properties of the helicene, leading to a tunable switching behavior of the conductance and thermopower of the junction with on/off ratios of several orders of magnitude. Furthermore, control over the helicene length and number of rings is shown to lead to more than an order of magnitude increase in the thermopower and thermoelectric figure-of-merit over typical molecular junctions, presenting new possibilities of making efficient thermoelectric molecular devices. The physical origin of the strong dependence of the transport properties of the junction is investigated, and found to be related to a shift in the position of the molecular orbitals., Comment: 12 pages, 8 figs, manuscript accepted to RSC Nanoscale

Published
2015
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2. On‐Surface Synthesis of Helicene Oligomers.

Author

Pinar Solé, Andrés, Klívar, Jiří, Šámal, Michal, Stará, Irena G., Starý, Ivo, Mendieta‐Moreno, Jesús I., Ernst, Karl‐Heinz, Jelínek, Pavel, and Stetsovych, Oleksandr

Subjects
OLIGOMERIZATION, SCANNING probe microscopy, RACEMIC mixtures, ULTRAHIGH vacuum, OLIGOMERS, CHIRALITY, DIMERS
Abstract

We report on‐surface synthesis of heterochiral 1D heptahelicene oligomers after deposition of a racemic heptahelicene monomer on an Au(111) surface followed by Ullmann coupling under ultrahigh vacuum conditions. Structure, chirality and mode of adsorption of the resulting dimers to octamers are inferred from the scanning probe microscopy and theoretical calculations. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Helical Bilayer Nanographenes: Impact of the Helicene Length on the Structural, Electrochemical, Photophysical, and Chiroptical Properties

Author

Izquierdo-García, Patricia, primary, Fernández-García, Jesús M., additional, Medina Rivero, Samara, additional, Šámal, Michal, additional, Rybáček, Jiří, additional, Bednárová, Lucie, additional, Ramírez-Barroso, Sergio, additional, Ramírez, Francisco J., additional, Rodríguez, Rafael, additional, Perles, Josefina, additional, García-Fresnadillo, David, additional, Crassous, Jeanne, additional, Casado, Juan, additional, Stará, Irena G., additional, and Martín, Nazario, additional

Published
2023
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6. Helical Bilayer Nanographenes: Impact of the Helicene Length on the Structural, Electrochemical, Photophysical, and Chiroptical Properties

Author

Izquierdo-García, Patricia, Fernández-García, Jesús M., Medina Rivero, Samara, Šámal, Michal, Rybáček, Jiří, Bednárová, Lucie, Ramírez-Barroso, Sergio, Ramírez, Francisco J., Rodríguez, Rafael, Perles, Josefina, García-Fresnadillo, David, Crassous, Jeanne, Casado, Juan, Stará, Irena G., Martín, Nazario, Izquierdo-García, Patricia, Fernández-García, Jesús M., Medina Rivero, Samara, Šámal, Michal, Rybáček, Jiří, Bednárová, Lucie, Ramírez-Barroso, Sergio, Ramírez, Francisco J., Rodríguez, Rafael, Perles, Josefina, García-Fresnadillo, David, Crassous, Jeanne, Casado, Juan, Stará, Irena G., and Martín, Nazario

Published
2023

12. Cationic Triarylcarbenium Helicenes:Synthesis, Resolution, and Applications

Author

Crassous, Jeanne, Stará, Irena G., Starý, Ivo, Bosson, Johann, Bisballe, Niels, Laursen, Bo W., Lacour, Jérôme, Crassous, Jeanne, Stará, Irena G., Starý, Ivo, Bosson, Johann, Bisballe, Niels, Laursen, Bo W., and Lacour, Jérôme

Abstract

Cationic [n]helicenes ( n = 4,5,6), based on bridged triarylmethylium skeletons, are highly stable carbenium ions, which can be stored as carbocations under air. Most of them are inert even in strongly alkaline aqueous solutions. These colorful dyes can be tuned electronically by changing their intrarim heteroatoms or by diverse regioselective additions of substituents (auxochromes). Fluorescence in the red to NIR is also afforded with moderate to excellent quantum yields and lifetimes up to 10 ns and above. Many applications, detailed herein, have been reported, thanks to their simple and flexible synthesis that yields helicenes with (very) high configurational and chemical stability and tailored optical and redox properties.

Published
2022

14. An Organometallic Route to Long Helicenes

Author

Sehnal, Petr, Stará, Irena G., Šaman, David, Tichý, Miloš, Míšek, Jiří, Cvačka, Josef, Rulíšek, Lubomír, Chocholoušová, Jana, Vacek, Jaroslav, Goryl, Grzegorz, Szymonski, Marek, Císařová, Ivana, Starý, Ivo, and Meinwald, Jerrold

Published
2009
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17. Nonaqueous capillary electrophoresis and quantum chemical calculations applied to investigation of acid–base and electromigration properties of azahelicenes

Author

Šolínová, Veronika, primary, Štěpánová, Sille, additional, Jančařík, Andrej, additional, Klívar, Jiří, additional, Šámal, Michal, additional, Stará, Irena G., additional, Chocholoušová, Jana Vacek, additional, Vacek, Jaroslav, additional, Starý, Ivo, additional, and Kašička, Václav, additional

Published
2021
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18. Synthesis of Racemic, Diastereopure, and Enantiopure Carba- or Oxa[5]‑, [6]‑, [7]‑, and -[19]helicene (Di)thiol Derivatives

Author

Stará, Irena G., Starý, Ivo, Nejedlý, Jindřich, and Šámal, Michal

Abstract

A series of carba- or oxa[5]-, [6]-, [7]-, and -[19]helicene (di)thiols was prepared. The Miyazaki−Newman−Kwart rearrangement of (dimethylcarbamothioyl)oxy (oxa)helicenes in a flow reactor or nucleophilic substitution of dichloro(oxa)helicenes with alkanethiolates were used in the sulfanylation step. Despite the high temperatures employed in this key step, no conformational scrambling was observed during the asymmetric synthesis of the diastereo- and enantiopure oxahelicenes. Single-molecule conductivity of the longest oxa[19]helicene dithiol derivative was studied by the scanning tunneling microscopy break-junction method.

Published
2019

22. On‐Surface Synthesis of Polyferrocenylene and its Single‐Chain Conformational and Electrical Transport Properties

Author

Santhini, Vijai M., primary, Stetsovych, Oleksandr, additional, Ondráček, Martin, additional, Mendieta Moreno, Jesus I., additional, Mutombo, Pingo, additional, Torre, Bruno, additional, Švec, Martin, additional, Klívar, Jiří, additional, Stará, Irena G., additional, Vázquez, Héctor, additional, Starý, Ivo, additional, and Jelínek, Pavel, additional

Published
2020
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24. Synthesis of Racemic, Diastereopure, and Enantiopure Carba- or Oxa[5]-, [6]-, [7]-, and -[19]helicene (Di)thiol Derivatives

Author

Nejedlý, Jindřich, primary, Šámal, Michal, additional, Rybáček, Jiří, additional, Sánchez, Isabel Gay, additional, Houska, Václav, additional, Warzecha, Tomáš, additional, Vacek, Jaroslav, additional, Sieger, Ladislav, additional, Buděšínský, Miloš, additional, Bednárová, Lucie, additional, Fiedler, Pavel, additional, Císařová, Ivana, additional, Starý, Ivo, additional, and Stará, Irena G., additional

Published
2019
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25. Growth kinetics of racemic heptahelicene-2-carboxylic acid nanowires on calcite (104).

Author

Einax, Mario, Richter, Tobias, Nimmrich, Markus, Rahe, Philipp, Stará, Irena G., Starý,, Ivo, Kühnle, Angelika, and Maass, Philipp

Subjects
MOLECULAR self-assembly, CARBOXYLIC acids, DIELECTRIC materials, CRYSTAL growth, NANOWIRES, CALCITE crystals, CHEMICAL kinetics
Abstract

Molecular self-assembly of racemic heptahelicene-2-carboxylic acid on a dielectric substrate at room temperature can be used to generate wire-like organic nanostructures consisting of single and double molecular rows. By means of non-contact atomic force microscopy, we investigate the growth of the wire-like pattern after deposition by experimental and theoretical means. From analyzing the time dependence of the mean row length, two distinct regimes were found. At the early post-deposition stage, the mean length grows in time. Subsequently, a crossover to a second regime is observed, where the mean row length remains nearly constant. We explain these findings by a mean-field rate equation approach providing a comprehensive picture of the growth kinetics. As a result, we demonstrate that the crossover between the two distinct regimes is accomplished by vanishing of the homochiral single rows. At later stages only heterochiral double row structures remain. [ABSTRACT FROM AUTHOR]

Published
2016
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26. Front Cover: Chirality‐Controlled Self‐Assembly of Amphiphilic Dibenzo[6]helicenes into Langmuir–Blodgett Thin Films (Chem. Eur. J. 49/2019)

Author

Holec, Jan, primary, Rybáček, Jiří, additional, Vacek, Jaroslav, additional, Karras, Manfred, additional, Bednárová, Lucie, additional, Buděšínský, Miloš, additional, Slušná, Michaela, additional, Holý, Petr, additional, Schmidt, Bernd, additional, Stará, Irena G., additional, and Starý, Ivo, additional

Published
2019
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32. On‐Surface Synthesis of Polyferrocenylene and its Single‐Chain Conformational and Electrical Transport Properties.

Author

Santhini, Vijai M., Stetsovych, Oleksandr, Ondráček, Martin, Mendieta Moreno, Jesus I., Mutombo, Pingo, Torre, Bruno, Švec, Martin, Klívar, Jiří, Stará, Irena G., Vázquez, Héctor, Starý, Ivo, and Jelínek, Pavel

Subjects
ELECTRICAL conductivity measurement, SCANNING probe microscopy, CONDUCTING polymers, ORGANIC electronics, INHOMOGENEOUS materials
Abstract

Unlike intrinsically conductive organic polymers, which are central to organic electronics/photovoltaics, metallopolymers contain multiple redox‐active centers allowing extra control of their intriguing properties. Ferrocene polymers are particularly attractive in this regard, but research of the iconic poly(1,1′‐ferrocenylene), a main‐chain ferrocene polymer with the most densely bound redox‐active iron centers, has practically stopped because it is an insoluble and rather inhomogeneous material. Herein, its synthesis on the Ag(111) surface is reported, based on the Ullmann coupling of 1′,1″′‐diiodo‐1,1″‐biferrocene. Conformationally flexible single‐chain nanowires up to 50 nm in length, thus overcoming the limits of conventional solution polymerization, are characterized by scanning probe microscopy techniques achieving atomic resolution. Single‐chain electrical conductivity measurements are performed in the longitudinal directions revealing apparent metal‐to‐semiconductor transition (depending on the number of ferrocene units lifted from the surface). A simple transport model is established to rationalize this observation. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Synthesis of Long Oxahelicenes by Polycyclization in a Flow Reactor

Author

Stará, Irena G. and Starý, Ivo

Abstract

A series of oxahelicenes composed of ortho/metaannulated benzene/pyridine and 2H-pyran rings were synthesized on the basis of the cobalt(I)-mediated (or rhodium(I)- or nickel(0)-mediated) double, triple, or quadruple [2+2+2]cycloisomerization of branched aromatic hexa-, nona-, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyclization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]-, [13]-, [17]- and [19]helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single-molecule conductivity was studied by the mechanically controllable break-junction method with a pyridooxa[9]helicene.

Published
2017

38. Large Converse Piezoelectric Effect Measured on a Single Molecule on a Metallic Surface

Author

Stetsovych, Oleksandr, primary, Mutombo, Pingo, additional, Švec, Martin, additional, Šámal, Michal, additional, Nejedlý, Jindřich, additional, Císařová, Ivana, additional, Vázquez, Héctor, additional, Moro-Lagares, María, additional, Berger, Jan, additional, Vacek, Jaroslav, additional, Stará, Irena G., additional, Starý, Ivo, additional, and Jelínek, Pavel, additional

Published
2018
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41. Spectroscopic characterization of the on-surface induced (cyclo)dehydrogenation of a N-heteroaromatic compound on noble metal surfaces

Author

Ministerio de Economía y Competitividad (España), European Commission, European Research Council, Palacio, Irene, Pinardi, Anna Lisa, Martínez, José I., Preobrajenski, Alexei, Cossaro, Albano, Jancarik, Andrej, Stará̈, Irena G., Méndez, Javier, Martín-Gago, José A., López, María Francisca, Ministerio de Economía y Competitividad (España), European Commission, European Research Council, Palacio, Irene, Pinardi, Anna Lisa, Martínez, José I., Preobrajenski, Alexei, Cossaro, Albano, Jancarik, Andrej, Stará̈, Irena G., Méndez, Javier, Martín-Gago, José A., and López, María Francisca

Abstract

New nanoarchitectures can be built from polycyclic aromatic hydrocarbons (PAHs) by exploiting the capability of some metal surfaces for inducing cyclodehydrogenation reactions. This bottom-up approach allows the formation of nanostructures with a different dimensionality from the same precursor as a consequence of the diffusion and coupling of the PAHs adsorbed on the surface. In this work we present a thorough study, by means of a combination of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure and scanning tunneling microscopy with first principle calculations of the structural and chemical transformations undergone by pyridyl-substituted dibenzo[5]helicene on three coinage surfaces, namely Cu(110), Cu(111) and Au(111). Upon annealing, on-surface chemical reactions are promoted affecting the adsorbate/substrate and the molecule/molecule interactions. This thermally induced process favours the transformation from diffusing isolated molecules to polymeric nanographene chains and finally to N-doped graphene.

Published
2017

42. From helical to planar chirality by on-surface chemistry

Author

Stará, Irena G., Starý, Ivo, and Jelínek, Pavel

Abstract

The chirality of molecular structures is paramount in many phenomena, including enantioselective reactions, molecular selfassembly, biological processes and light or electron-spin polarization. Flat prochiral molecules, which are achiral in the gas phase or solution, can exhibit adsorption-induced chirality when deposited on surfaces. The whole array of such molecular adsorbates is naturally racemic as spontaneous global mirror-symmetry breaking is disfavoured. Here we demonstrate a chemical method of obtaining flat prochiral molecules adsorbed on the solid achiral surface in such a way that a specific adsorbate handedness globally dominates. An optically pure helical precursor is flattened in a cascade of on-surface reactions, which enables chirality transfer. The individual reaction products are identified by high-resolution scanning-probe microscopy. The ultimate formation of globally non-racemic assemblies of flat molecules through stereocontrolled on-surface synthesis allows for chirality to be expressed in as yet unexplored types of organic–inorganic chiral interfaces.

Published
2016

43. Synthesis of Long Oxahelicenes by Polycyclization in a Flow Reactor

Author

Nejedlý, Jindřich, primary, Šámal, Michal, additional, Rybáček, Jiří, additional, Tobrmanová, Miroslava, additional, Szydlo, Florence, additional, Coudret, Christophe, additional, Neumeier, Maria, additional, Vacek, Jaroslav, additional, Vacek Chocholoušová, Jana, additional, Buděšínský, Miloš, additional, Šaman, David, additional, Bednárová, Lucie, additional, Sieger, Ladislav, additional, Stará, Irena G., additional, and Starý, Ivo, additional

Published
2017
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44. Oxahelicene NHC ligands in the asymmetric synthesis of nonracemic helicenes

Author

Sánchez, Isabel Gay, primary, Šámal, Michal, additional, Nejedlý, Jindřich, additional, Karras, Manfred, additional, Klívar, Jiří, additional, Rybáček, Jiří, additional, Buděšínský, Miloš, additional, Bednárová, Lucie, additional, Seidlerová, Beata, additional, Stará, Irena G., additional, and Starý, Ivo, additional

Published
2017
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46. An Ultimate Stereocontrol in Asymmetric Synthesis of Optically Pure Fully Aromatic Helicenes

Author

Stará, Irena G., Starý, Ivo, and Šámal, Michal

Abstract

The role of the helicity of small molecules in enantioselective catalysis, molecular recognition, self-assembly, material science, biology, and nanoscience is much less understood than that of point-, axial-, or planar-chiral molecules. To uncover the envisaged potential of helically chiral polyaromatics represented by iconic helicenes, their availability in an optically pure form through asymmetric synthesis is urgently needed. We provide a solution to this problem present since the birth of helicene chemistry in 1956 by developing a general synthetic methodology for the preparation of uniformly enantiopure fully aromatic [5]-, [6]-, and [7]helicenes and their functionalized derivatives. [2 + 2 + 2] Cycloisomerization of chiral triynes combined with asymmetric transformation of the first kind (ultimately controlled by the 1,3-allylic-type strain) is central to this endeavor. The point-to-helical chirality transfer utilizing a traceless chiral auxiliary features a remarkable resistance to diverse structural perturbations.

Published
2015

47. Helically Chiral Aromatics: The Synthesis of Helicenes by [2 + 2 + 2] Cycloisomerization of π-Electron Systems

Author

Stará, Irena G. and Starý, Ivo

Abstract

Advanced molecular nanocarbons are now in the spotlight reflecting the basic discoveries of fullerenes, carbon nanotubes, and graphene. This research area includes also the chemistry, physics, and nanoscience of nonplanar polycyclic hydrocarbons, many of which exhibit helical chirality, such as iconic helicenes and their congeners. The combination of unique π-electron systems with the chirality phenomenon makes them highly attractive in various fields of science. Helicenes are polyaromatic compounds that are composed of all-angularly annulated benzene units, but other (hetero)cycles can also be embedded into their backbone. Even though they do not contain any stereogenic center, they are inherently chiral owing to the helical shape they adopt. Hexahelicene and higher homologues are conformationally stable within a reasonable range of temperatures and, therefore, can be obtained in an enantiopure form through a racemate resolution or asymmetric synthesis. An amazing array of synthetic methods for their preparation has been developed, but only a few of them have passed the tough scrutiny to be general, robust and practical methods such as traditional photocyclodehydrogenation of diaryl olefins and recently developed transition-metal-catalyzed [2 + 2 + 2] cycloisomerization of π-electron systems, which is discussed in this Account.

Published
2020
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49. From helical to planar chirality by on-surface chemistry

Author

Stetsovych, Oleksandr, primary, Švec, Martin, additional, Vacek, Jaroslav, additional, Chocholoušová, Jana Vacek, additional, Jančařík, Andrej, additional, Rybáček, Jiří, additional, Kosmider, Krzysztof, additional, Stará, Irena G., additional, Jelínek, Pavel, additional, and Starý, Ivo, additional

Published
2016
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