A Series of Polyamide Receptor Based PET Fluorescent Sensor Molecules: Positively Cooperative Hg²⁺ Ion Binding with High Sensitivity

A series of PET fluorescent sensor molecules were designed and synthesized based on BODIPY fluorophore and polyamide receptors. Comparison of the photophysical properties of these sensor molecules, equipped with di-, tri-, and tetraamide receptor, provided a deep insight into the polyamide−Hg2+ interactions, and an unusual positively cooperative tetraamide−Hg2+ complexation was disclosed. In addition, sensor S3 displayed several favorable sensing properties

Detecting Hg²⁺ Ions with an ICT Fluorescent Sensor Molecule: Remarkable Emission Spectra Shift and Unique Selectivity

A fluorescent ratiometric Hg2+ ion sensor RMS, based on a coumarin platform coupled with a tetraamide receptor, is presented. This sensor, employing the ICT mechanism, could be used to specifically detect Hg2+ ions in a neutral buffered water solution with an ∼100-nm blue shift in emission spectra

Fusing of Seven HBCs toward a Green Nanographene Propeller

This work presents a green chiral nanographene propeller (NP), which is built by fusing seven hexa­benzo­coronenes in a helical arrangement. It contains 258 conjugated carbon atoms and represents the largest three-dimensional conjugated polycyclic aromatic hydrocarbons ever prepared using scalable solution chemistry. Despite its unusual molecular size, single-crystal X-ray structural analysis (resolution 0.9 Å) and baseline chiral resolution are achieved. NP is soluble in various organic solvents and can be fully characterized by common spectroscopic and voltammetric techniques. It has a strong panchromatic absorption from the ultraviolet to the near-infrared (λmax = 659 nm, ε = 179 000 M–1 cm–1). For instance, more than half of the spectral range between 300 and 800 nm witnesses an extinction coefficient larger than 100 000 M–1 cm–1. Moreover, a record-high Cotton effect in the visible spectrum is observed for enantiopure NP, with |Δε| values of 1182 and 1090 M–1 cm–1 at 374 and 405 nm, respectively. These photophysical properties evolve significantly compared to those of the propeller-shaped hexapole [7]­helicene

Fusing of Seven HBCs toward a Green Nanographene Propeller

This work presents a green chiral nanographene propeller (NP), which is built by fusing seven hexa­benzo­coronenes in a helical arrangement. It contains 258 conjugated carbon atoms and represents the largest three-dimensional conjugated polycyclic aromatic hydrocarbons ever prepared using scalable solution chemistry. Despite its unusual molecular size, single-crystal X-ray structural analysis (resolution 0.9 Å) and baseline chiral resolution are achieved. NP is soluble in various organic solvents and can be fully characterized by common spectroscopic and voltammetric techniques. It has a strong panchromatic absorption from the ultraviolet to the near-infrared (λmax = 659 nm, ε = 179 000 M–1 cm–1). For instance, more than half of the spectral range between 300 and 800 nm witnesses an extinction coefficient larger than 100 000 M–1 cm–1. Moreover, a record-high Cotton effect in the visible spectrum is observed for enantiopure NP, with |Δε| values of 1182 and 1090 M–1 cm–1 at 374 and 405 nm, respectively. These photophysical properties evolve significantly compared to those of the propeller-shaped hexapole [7]­helicene

Photoswitchable Intramolecular Through-Space Magnetic Interaction

The interaction between two TEMPO spin centers connected to a photoswitchable overcrowded alkene changes from noncoupled (three-line EPR spectrum) in the trans state, where the two spin centers are separated by ∼22 Å, to strongly coupled (five-line EPR spectrum) in the cis state, where the separation is ∼7 Å, upon photoswitching. Importantly, the performance of the alkene switching unit is essentially unaffected by the spin centers

Photoswitchable Intramolecular H-Stacking of Perylenebisimide

Dynamic control over the formation of H- or J-type aggregates of chromophores is of fundamental importance for developing responsive organic optoelectronic materials. In this study, the first example of photoswitching between a nonstacked and an intramolecularly H-stacked arrangement of perylenebisimides (PBI) is demonstrated. The system is composed of a central switching unit (overcrowded alkene) tethered to two PBI chromophores. cis−trans isomerization of the switching unit, induced by alternate irradiation at 312 and 365 nm, can drive two PBI chromophores reversibly between an intramolecularly “aggregated” and “nonaggregated” state. Distinct changes in UV−vis absorption and fluorescence spectra are observed following photoisomerization. This approach allows for efficient control of intramolecular H-stack formation with no significant intermolecular interactions spanning over at least 4 orders of magnitude of concentration (from 10−8 to 10−4 M) and a range of solvents and temperatures

Tuning On-Surface Synthesis of Graphene Nanoribbons by Noncovalent Intermolecular Interactions

On-surface synthesis has been widely used for the precise fabrication of surface-supported covalently bonded nanostructures. Here, we report on tuning the on-surface synthesis of graphene nanoribbons by noncovalent intermolecular interactions on Au(111) surfaces. By introducing noncovalent intermolecular interactions with the companion molecules (dianhydride derivative), intramolecular cyclodehydrogenation of nonplanar precursor molecules (bianthryl derivative) are promoted at 200 °C, with the monomers interlinked by gold atoms instead of the formation of polyanthrylene. By adjusting the deposition sequence of precursor and companion molecules, conjugated graphene nanoribbons can be finally obtained at a temperature of 240 °C, much lower than the synthesis procedures without companion molecules. Density functional theory calculations indicate that intermolecular interactions result in a dramatic shrinkage of the torsional angle between the adjacent anthryl groups of the precursor molecule, aiding the cyclodehydrogenation process. Our work demonstrates an intermolecular strategy for controllable fabrication of covalently bonded nanostructures by on-surface synthesis

Electron Transport and Electrochemistry of Mesomorphic Fullerenes with Long-Range Ordered Lamellae

Electron Transport and Electrochemistry of Mesomorphic Fullerenes with Long-Range Ordered Lamella

Thermally Induced Transformation of Nonhexagonal Carbon Rings in Graphene-like Nanoribbons

Exploring the structural transformation of nonhexagonal rings is of fundamental importance for understanding the thermal stability of nonhexagonal rings and revealing the structure–property relationships. Here, we report on the thermally induced transformation from the fused tetragon-hexagon (4–6) carbon rings to a pair of pentagon (5–5) rings in the graphene-like nanoribbons periodically embedded with tetragon and octagon (4–8–4) carbon rings. A distinct contrast among tetragon, pentagon, hexagon, and octagon carbon rings is provided by noncontact atomic force microscopy with atomic resolution. The thermally activated bond rotation with the dissociation of the shared carbon dimer between the 4–6 carbon rings is the key step for the 4–6 to 5–5 transformation. The energy barrier of the bond rotation, which results in the formation of an irregular octagon ring in the transition state, is calculated to be 1.13 eV. The 5–5 defects markedly change the electronic local density of states of the graphene-like nanoribbon, as observed by scanning tunneling microscopy. Our density functional theory calculations indicate that the introduction of periodically embedded 5–5 rings will significantly narrow the electronic band gap of the graphene-like nanoribbons

Synthesis and Characterization of Ferrocene Based Hemicages

We present a series of tripodal ligands L1–3, which fold into hemicages C1–3 by using coordination-driven dynamic combinational chemistry. The identities of these hemicages were characterized using 1H NMR, 1H–1H COSY, DOSY, and ESI-TWIM-MS. Free rotation of the ferrocene structural units in the ligands affords an adaptable directionality, which is essential for the construction of these hemicages. Encapsulation of adamantane by C2 indicates the presence of a well-defined inner cavity as the binding pocket