Molecular Actuator: Redox-Controlled Clam-Like Motion in a Bichromophoric Electron Donor

The one-electron oxidation of tetramethoxydibenzobicyclo[4.4.1]undecane (4) prompts it to undergo a clam-like electromechanical actuation into a cofacially π-stacked conformer as established by (i) electrochemical analysis, (ii) by the observation of the intense charge-resonance transition in the near IR region in its cation radical spectrum, and (iii) by X-ray crystallographic characterization of the isolated cation radical salt (4+• SbCl6−)

Poly-p-hydroquinone Ethers: Isoenergetic Molecular Wires with Length-Invariant Oxidation Potentials and Cation Radical Excitation Energies

Typical poly-p-phenylene wires are characterized by strong interchromophoric electronic coupling with redox and optical properties being highly length-dependent. Herein we show that an incorporation of a pair of para-methoxy groups at each p-phenylene unit in poly-p-phenylene wires (i.e., PHEn) changes the nodal structure of HOMO that leads to length-invariant oxidation potentials and cation radical excitation energies. As such, PHEn represents a unique class of isoenergetic wires where hole delocalization mainly occurs via dynamic hopping and thus may serve as an efficient medium for long-range charge transfer. Availability of these wires will allow demonstration of long-range electron transfer via incoherent hopping using donor-bridge-acceptor systems with isoenergetic PHEn-based wires as bridges

X-ray Structural Characterization of Charge Delocalization onto the Three Equivalent Benzenoid Rings in Hexamethoxytriptycene Cation Radical

Definitive X-ray crystallographic evidence is obtained for a single hole (or a polaron) to be uniformly distributed on the three equivalent 1,2-dimethoxybenzenoid (or veratrole) rings in the hexamethoxytriptycene cation radical. This conclusion is further supported by electrochemical analysis and by the observation of an intense near-IR transition in its electronic spectrum, as well as by comparison of the spectral and electrochemical characteristics with the model compounds containing one and two dimethoxybenzene rings

Simultaneous Ejection of Six Electrons at a Constant Potential by Hexakis(4-ferrocenylphenyl)benzene

A simple synthesis of a dendritic hexaferrocenyl electron donor (5) is described in which six ferrocene moieties are connected at the vertices of the propeller of the hexaphenylbenzene core. The molecular structure of 5 is confirmed by X-ray crystallography. An electrochemical analysis along with redox titrations (which are tantamount to coulometry) confirmed that it ejects six electrons at a single potential

Facile synthetic procedure for and electrochemical properties of hexa(2-thienyl)benzenes directed toward electroactive materials

In the presence of RhCl3 center dot 3H(2)O and i-Pr2NEt, the cyclotrimerization of di(2-thienyl)acetylenes proceeded smoothly to afford hexa(2-thienyl)benzenes. CV analysis of the hexa(2-thienyl)benzenes showed that they may be useful as electroactive materials.</p

Charge Delocalization in Self-Assembled Mixed-Valence Aromatic Cation Radicals

The spontaneous assembly of aromatic cation radicals (D+•) with their neutral counterpart (D) affords dimer cation radicals (D2+•). The intermolecular dimeric cation radicals are readily characterized by the appearance of an intervalence charge-resonance transition in the NIR region of their electronic spectra and by ESR spectroscopy. The X-ray crystal structure analysis and DFT calculations of a representative dimer cation radical (i.e., the octamethylbiphenylene dimer cation radical) have established that a hole (or single positive charge) is completely delocalized over both aromatic moieties. The energetics and the geometrical considerations for the formation of dimer cation radicals is deliberated with the aid of a series of cyclophane-like bichromophoric donors with drastically varied interplanar angles between the cofacially arranged aryl moieties. X-ray crystallography of a number of mixed-valence cation radicals derived from monochromophoric benzenoid donors established that they generally assemble in 1D stacks in the solid state. However, the use of polychromophoric intervalence cation radicals, where a single charge is effectively delocalized among all of the chromophores, can lead to higher-order assemblies with potential applications in long-range charge transport. As a proof of concept, we show that a single charge in the cation radical of a triptycene derivative is evenly distributed on all three benzenoid rings and this triptycene cation radical forms a 2D electronically coupled assembly, as established by X-ray crystallography

The HOMO Nodal Arrangement in Polychromophoric Molecules and Assemblies Controls the Interchromophoric Electronic Coupling

Triptycenes spontaneously assemble into two-dimensional networks in which long-range charge transport is facilitated by the extensive electronic coupling through the triptycene framework (intramolecularly) and by cofacial π-stacking (intermolecularly). While designing and synthesizing next-generation triptycenes containing polyaromatic chromophores, the electronic coupling amongst the chromophores was observed to be highly dependent on the nature and position of the substituents. Herein, we demonstrate using hexaalkoxytriptycenes that the electronic coupling amongst the chromophores is switched on and off by a simple repositioning of the substituents, which alters the nodal arrangement of the HOMOs of the individual chromophores. A visual inspection of the HOMOs can thus provide a ready evaluation of the electronic coupling in polychromophoric molecules/assemblies, and will serve as an important tool for the rational design of modern charge-transport materials

Benzodithiophene and benzotrithiophene as \ucf\u80 cores for two-and three-blade propeller-shaped ferrocenyl-based conjugated systems

The syntheses of linear and star-shaped bis- and tris(ferrocenyl) derivatives of benzo[1,2-b:4,5-b\u2032]dithiophene and benzo[1,2-b:3,4-b\u2032:5,6-b\u2032\u2032]trithiophene are achieved through one-pot CuI/TMEDA-catalyzed (TMEDA = tetramethylethylenediamine) multiple annulations of bromoethynylbenzenes with sodium sulfide. In addition, the preparation of the parent benzotrithiophene in a good yield with a short reaction time is achieved through the threefold annulation of 1,3,5-trifluoro- Introduction Benzo[b]thiophene (BT, Scheme 1) and its derivatives are an important class of fused thiophene compounds owing to their wide range of biological properties[1,2] and various applications in materials science.[3] Scheme 1. Fused thiophene compounds: benzo[b]thiophene (BT), benzo- [1,2-b:4,5-b\u2032]dithiophene (BDT), and benzo[1,2-b:3,4-b\u2032:5,6-b\u2032\u2032]trithiophene (BTT). In particular, (multi)thiophene fused aromatic compounds are attracting interest as promising electronic materials for organic conductors,[4] organic light-emitting diodes,[5] photovoltaic cells,[6] and field-effect transistors.[7] For this reason, thiophene- based \u3c0-conjugated oligomers have been investigated widely as organic semiconductors.[8] Recently, much effort has been focused on benzo[1,2-b:4,5-b\u2032]- dithiophene (BDT) and benzo[1,2-b:3,4-b\u2032:5,6-b\u2032\u2032]trithiophene (BTT, Scheme 1) as potential \u3c0 cores for a new class of organic semiconductors as they contain two or three identical thiophene moieties with C2h or C3h symmetries that enable twoand three-dimensional molecular extensions. [a] Department of Chemical Sciences, University of Padova Via Marzolo 1, 35131 Padova, Italy E-mail: [email protected] http://www.chimica.unipd.it/ Supporting information and ORCID(s) from the author(s) for this article are available on the WWW under https://doi.org/10.1002/ejoc.201701045. Eur. J. Org. Chem. 2017, 5966\u20135974 5966 \ua9 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2,4,6-tris(trimethylsilyl)ethynylbenzene. The computed structural and electronic features of these ferrocenyl derivatives as well as their UV/Vis spectra and electrochemistry are discussed, and the results provide insights into the effect of the presence of three rather than two ferrocenyl units. To the best of our knowledge, 2,5,8-tris(ferrocenyl)benzo[1,2-b;3,4-b\u2032;5,6-b\u2032\u2032]trithiophene is the first organometallic complex containing benzotrithiophene

Design, Syntheses, and Study of Electron Communication through Conformationally-Adaptable and Cofacially Arrayed Polybenzenoid Structures; Search of New Molecular Motifs for Molecular Wires

Among the various o- and formula complexes of silver cations with organic ligands, those derived from arene donors have the desired structural diversity for the construction of organometallic (solid-state) devices as electrical conductors, photoactive switches, chemical sensors, etc. This possibility stems in large part from the active synthetic interest in polycyclic hydrocarbons that bear two or more aromatic groups in interesting arrays, including diarylalkanes (-alkenes and -alkynes), cyclophanes, tryptycenes, triangulanes, deltaphanes, cylindrophanes, etc. The structural rigidity of the molecular frameworks of various macromolecular receptors for the exploration of metal ion-aromatic donor-acceptor complexes is highly sought after..