Interpenetrated 3D Polymeric Metal−Radical Networks Built from a Tetranitroxide Radical and Bis(hexafluoroacethylacetonato) Manganese(II)

Interpenetrated 3D Polymeric Metal−Radical Networks Built from a Tetranitroxide Radical and Bis(hexafluoroacethylacetonato) Manganese(II

Smectic Liquid Crystals from Supramolecular Guanidinium Alkanesulfonates^†

The thermotropic polymorphism of a series of guanidinium alkanesulfonates (6 ≤ n ≤ 18) was investigated by optical microscopy and differential scanning calorimetry. Hydrogen bonding was analyzed by infrared spectroscopy. Molecular volumes were measured by dilatometry. The structure of the crystal, smectic A, and ordered smectic phases observed were studied by X-ray diffraction and utilized to prove that the supramolecular arrangement of the molecules in the crystal survives in the smectic phases at high temperature

Single-Molecule Dynamics in a Self-Assembled 2D Molecular Sieve

A two-dimensional molecular sieve has been realized. It consists of a host matrix of molecularly engineered building blocks self-assembled at the liquid−solid interface. The simultaneous size- and shape-dependent dynamics of different guest molecules is observed in situ, in real time with submolecular resolution using a scanning tunneling microscope both at the liquid−solid interface and under vacuum. The temperature-dependent dynamics reveals that the diffusion proceeds through thermally activated channeling between single-molecule surface cavities

Ordinary and Hot Electroluminescence from Single-Molecule Devices: Controlling the Emission Color by Chemical Engineering

Single-molecule junctions specifically designed for their optical properties are operated as light-emitting devices using a cryogenic scanning tunneling microscope. They are composed of an emitting unita molecular chromophoresuspended between a Au(111) surface and the tip of the microscope by organic linkers. Tunneling electrons flowing through these junctions generate a narrow-line emission of light whose color is controlled by carefully selecting the chemical structure of the emitting unit. Besides the main emission line, red and blue-shifted vibronic features of low intensity are also detected. While the red-shifted features provide a spectroscopic fingerprint of the emitting unit, the blue-shifted ones are interpreted in terms of hot luminescence from vibrationally excited states of the molecule

Single-Molecule Dynamics in a Self-Assembled 2D Molecular Sieve

A two-dimensional molecular sieve has been realized. It consists of a host matrix of molecularly engineered building blocks self-assembled at the liquid−solid interface. The simultaneous size- and shape-dependent dynamics of different guest molecules is observed in situ, in real time with submolecular resolution using a scanning tunneling microscope both at the liquid−solid interface and under vacuum. The temperature-dependent dynamics reveals that the diffusion proceeds through thermally activated channeling between single-molecule surface cavities

Fluorescent Self-Assembled Molecular Monolayer on Graphene

We report the first fluorescent molecular self-assembly on graphene. The quenching of the fluorescence of the adsorbed dye by the adjacent graphene is hindered at the molecular scale based on a spacer approach, through a specifically designed dual-functionalized self-assembling building block. This 3D tecton presents two faces, one forming a noncovalent graphene-binding pedestal and the other carrying a dye group linked by a spacer to the pedestal. The spontaneous ordering of the adsorbed layer is investigated by scanning tunneling microscopy, whereas the resulting optical properties of the whole graphene–dye hybrid system are characterized by absorption and fluorescence spectroscopies

Single Atom Substitution for Marking and Motion Tracking of Individual Molecules by Scanning Tunneling Microscopy

We report on a simple way to mark and track individual molecules self-assembled on a surface by scanning tunneling microscopy. The tracer mechanism consists in a minimal one-atom chemical substitution. While this substitution leads to significant modifications in the STM signature of the molecules, no substantial changes of the physics of self-assembling are observed when using the modified or unmodified molecular building blocks. This allows us to follow the intrinsic dynamical properties of the self-assembled molecular patterns

Structure and Epitaxial Registry on Graphite of a Series of Nanoporous Self-Assembled Molecular Monolayers

We have analyzed by STM the detailed structures of a series of nanoporous honeycomb networks stabilized by alkyl chain interdigitation on graphite at the liquid−solid interface, that is, clip-like noncovalent bonding. The variations observed as a function of the length of the peripheral aliphatic chains show that the assembly is directed not only by lateral intermolecular interactions but also by the adsorption site on the substrate. We derive an atomically accurate model for the registry with graphite of our nanoporous model series of systems. In full agreement with the quantitative model, the pore areas vary step-by-step by more than one order of magnitude along the whole series while preserving the detailed features of the graphite-induced alkyl chain interdigitation. The largest pores observed correspond to a ratio of uncovered substrate area as large as 35%

Lamello-Columnar Mesophase Formation in a Side-Chain Liquid Crystal π-Conjugated Polymer Architecture

Lamello-Columnar Mesophase Formation in a Side-Chain Liquid Crystal π-Conjugated Polymer Architectur

6-(Arylvinylene)-3-bromopyridine Derivatives as Lego Building Blocks for Liquid Crystal, Nonlinear Optical, and Blue Light Emitting Chromophores

A novel general synthetic strategy, based on a convergent approach, allowed us to prepare a series of conjugated 6,6‘-distyryl-3,3‘-bipyridine derivatives via the Suzuki reaction. First, the key electron-donor and electron-acceptor 6-(arylvinylene)-3-bromopyridine building blocks were synthesized by Knoevenagel- or Siegrist-type reactions. Second, some of them were transformed to the corresponding pyridylboronic esters. Finally, for the first time, we successfully demonstrated that such blocks can be homo- and cross-coupled in high yields and multigram scales, leading to noncentrosymmetic or symmetric chromophores. Their mesogenic, electrochemical, and optical properties have been investigated depending on the electronic structure. In this series, push−pull compounds are liquid crystals and promising for NLO applications. Whatever the structure, all of these compounds exhibit a high electron affinity and are strongly fluorescent. As an application, lasing properties of one push−pull and one symmetrical compound are reported. In addition, a blue-emitting LED was fabricated whose performances at 10 mA/cm2 are a luminous efficiency of 3.9 cd/A, a power efficiency of 1.4 lm/W, and an external quantum efficiency of 2.9%. Thus, this versatile synthetic route is of particular interest due to the potential applications of the chromophores in several optoelectronic fields