Selective and Efficient Upcycling of Polyesters from Waste Plastic Blends Enabled by a Rationally Designed Manganese Pincer Catalyst.

Herein, we report a new class of earth-abundant pincer manganese catalysts that not only enable the efficient conversion of single-component post-consumer polyesters with a turnover number (TON) of up to 5300, but more importantly, allow the selective upcycling of polyesters from waste plastic blends (e.g., nylon, PA; polyethylene, PE; polyurethane, PU; polyvinyl chloride, PVC; cotton) or contaminants such as pigment, aluminum, or glass into highly valuable oxygenated products under mild conditions.

Aryl-Radical-Initiated -Olefin Synthesis via Synergistic Palladium and Photocatalysis.

We report a novel photocatalyzed selective functionalization of terminal olefins for the synthesis of -olefins and cyclobutanes under mild conditions in excellent yields. A series of -cinnamic acid derivatives, enamines, and amide-containing cyclobutanes were efficiently synthesized using this method. Mechanistic studies indicated that the success of this reaction is based on the triple radical relay strategy, anion-π interaction for aryl halide activation and aryl radical generation, palladium for controlling chemoselectivity of the aryl radical, and photocatalyst for controlling stereoselectivity via diradical species, respectively.

Rapid and Controlled Assembly of Polysubstituted Furans and Their Oligoaryls from Alkynes and Aldehydes Facilitated by Sequential Deprotonation.

A new sequential deprotonation strategy of dimethyl sulfoxide (DMSO) and propargyl alcohol in the presence of a base was developed for the generation of the α-hydroxyl carbanion, which enables rapid and controllable access to a wide range of valuable highly functionalized furans in one pot from alkynes and aldehydes under transition-metal- and additive-free conditions. Preliminary mechanistic studies revealed the crucial role of the base and DMSO. More importantly, deuterium labeling experiments confirmed the formation of the α-hydroxyl carbanion.

A Poly(2,7-anthrylene) with peri-Fused Porphyrin Edges.

Anthracene has served as an important building block of conjugated polymers with the connecting positions playing a crucial role for the electronic structures. Herein, anthracene units have been coupled through their 2,7-carbons to develop an unprecedented, conjugated polymer, namely, poly(2,7-anthrylene) featuring additional peri-fused porphyrin edges. The synthesis starts from a 2,7-dibromo-9-nickel(II) porphyrinyl-anthracene as the pivotal precursor.

The Role of Alkyl Chains in the Thermoresponse of Supramolecular Network.

Supramolecular materials provide a pathway for achieving precise, highly ordered structures while exhibiting remarkable response to external stimuli, a characteristic not commonly found in covalently bonded materials. The design of self-assembled materials, where properties could be predicted/design from chemical nature of the individual building blocks, hinges upon our ability to relate macroscopic properties to individual building blocks - a feat which has thus far remained elusive. Here, a design approach is demonstrated to chemically engineer the thermal expansion coefficient of 2D supramolecular networks by over an order of magnitude (\boldmath 120 to \boldmath 1000 × 10 K).

Stable π-Extended Thio[7]helicene-Based Diradical with Predominant Through-Space Spin-Spin Coupling.

In this work, a novel π-extended thio[7]helicene scaffold was synthesized, where the α-position of the thiophene unit could be functionalized with bulky phenoxy radicals after considerable synthetic attempts. This open-shell helical diradical, , possesses high stability in the air, nontrivial π conjugation, persistent chirality, and a high diradical character ( of 0.998).

Recent Advances in Reversible Liquid Organic Hydrogen Carrier Systems: From Hydrogen Carriers to Catalysts.

Liquid organic hydrogen carriers (LOHCs) have gained significant attention for large-scale hydrogen storage due to their remarkable gravimetric hydrogen storage capacity (HSC) and compatibility with existing oil and gas transportation networks for long-distance transport. However, the practical application of reversible LOHC systems has been constrained by the intrinsic thermodynamic properties of hydrogen carriers and the performances of associated catalysts in the (de)hydrogenation cycles. To overcome these challenges, thermodynamically favored carriers, high-performance catalysts, and catalytic procedures need to be developed.

Heck Migratory Insertion Catalyzed by a Single Pt Atom Site.

Single-atom catalysts (SACs) have generated excitement for their potential to downsize metal particles to the atomic limit with engineerable local environments and improved catalytic reactivities and selectivities. However, successes have been limited to small-molecule transformations with little progress toward targeting complex-building reactions, such as metal-catalyzed cross-coupling. Using a supercritical carbon-dioxide-assisted protocol, we report a heterogeneous single-atom Pt-catalyzed Heck reaction, which provides the first C-C bond-forming migratory insertion on SACs.

Twisted Diindeno-Fused Dibenzo[a,h]anthracene Derivatives and their Dianions.

We report a facile synthesis of diindeno-fused dibenzo[a,h]anthracene derivatives (DIDBA-2Cl, DIDBA-2Ph, and DIDBA-2H) with different degrees of non-planarity using three substituents (chloro, phenyl, and hydrogen) of various sizes. The planarization of their cores, as evidenced by the decreased end-to-end torsional angles, was confirmed by X-ray crystallography. Their enhanced energy gaps with twisting were investigated by a combination of spectroscopic and electrochemical methods with density functional theory, which showed a transition from singlet open-shell to closed-shell configuration.

Zigzag-Edged Polycyclic Aromatic Hydrocarbons from Benzo[m]tetraphene Precursors.

A series of zigzag-edged polycyclic aromatic hydrocarbons (PAHs) (Z1-Z3) were synthesized from 2,12-dibromo-7,14-diphenyl-benzo[m]tetraphene (9) as a versatile building block. Their structures were unambiguously confirmed by laser desorption/ionization time-of-flight mass spectrometry, H NMR, Raman, and Fourier-transformed infrared (FTIR) spectroscopies as well as scanning tunneling microscopy. The fingerprint vibrational modes were elucidated with theoretical support.

Nanographenes and Graphene Nanoribbons as Multitalents of Present and Future Materials Science.

As cut-outs from a graphene sheet, nanographenes (NGs) and graphene nanoribbons (GNRs) are ideal cases with which to connect the world of molecules with that of bulk carbon materials. While various top-down approaches have been developed to produce such nanostructures in high yields, in the present perspective, precision structural control is emphasized for the length, width, and edge structures of NGs and GNRs achieved by modern solution and on-surface syntheses. Their structural possibilities have been further extended from "flatland" to the three-dimensional world, where chirality and handedness are the jewels in the crown.

Cove-Edged Hexa-peri-hexabenzo-bis-peri-octacene: Molecular Conformations and Amplified Spontaneous Emission.

The bottom-up synthesis of an unprecedentedly large cove-edged nanographene, hexa-peri-hexabenzo-bis-peri-octacene (HBPO), is reported in this work. Chiral high-performance liquid chromatography and density functional theory (DFT) calculations revealed multiple conformations in solution. Two different molecular conformations, "waggling" and "butterfly", were found in crystals by X-ray crystallography, and the selectivity of conformations could be tuned by solvents.

Electrochemical Synthesis, Deposition, and Doping of Polycyclic Aromatic Hydrocarbon Films.

Polycyclic aromatic hydrocarbons (PAHs) are employed as organic semiconductors because their delocalized π-electron systems and strong intermolecular interactions endow them with an exceptional charge-transport ability. However, the deposition of PAHs from solution onto high-quality thin films is often difficult. Here, we report a one-step electrochemical method to synthesize and deposit unsubstituted PAHs, starting from twisted oligophenyl precursors.

Dual Amplified Spontaneous Emission and Lasing from Nanographene Films.

Chemically synthesized zigzag-edged nanographenes (NG) have recently demonstrated great success as the active laser units in solution-processed organic distributed feedback (DFB) lasers. Here, we report the first observation of dual amplified spontaneous emission (ASE) from a large-size NG derivative (with 12 benzenoid rings) dispersed in a polystyrene film. ASE is observed simultaneously at the 685 and 739 nm wavelengths, which correspond to different transitions of the photoluminescence spectrum.

Stable Olympicenyl Radicals and Their π-Dimers.

An olympicenyl radical, a spin 1/2 hydrocarbon radical with symmetry and uneven spin distribution, remains elusive despite the considerable theoretical research interest. Herein, we report syntheses of two air-stable olympicenyl radical derivatives, and , with half-life times (τ) in air-saturated solution of 7 days and 34 days. The high stability was ascribed to kinetic blocking of reactive sites with high spin densities.

Formation of Azulene-Embedded Nanographene: Naphthalene to Azulene Rearrangement During the Scholl Reaction.

Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure.

Cove-Edged Nanographenes with Localized Double Bonds.

The efficient synthesis and electronic properties of two large-size cove-edged nanographenes (NGs), CN1 and CN2, are presented. X-ray crystallographic analysis reveals a contorted backbone for both molecules owing to the steric repulsion at the inner cove position. Noticeably, the dominant structures of these molecules contain four (for CN1) or six (for CN2) localized C=C double bonds embedded in nine (for CN1) or twelve (for CN2) aromatic sextet rings according to Clar's formula, which is supported by bond length analysis and theoretical (NICS, ACID) calculations.

Strain-Induced Isomerization in One-Dimensional Metal-Organic Chains.

The ability to use mechanical strain to steer chemical reactions creates completely new opportunities for solution- and solid-phase synthesis of functional molecules and materials. However, this strategy is not readily applied in the bottom-up on-surface synthesis of well-defined nanostructures. We report an internal strain-induced skeletal rearrangement of one-dimensional (1D) metal-organic chains (MOCs) via a concurrent atom shift and bond cleavage on Cu(111) at room temperature.

[6]Cyclo--phenylmethine: An Analog of Benzene Showing Global Aromaticity and Open-Shell Diradical Character.

We report a [6]cyclo--phenylmethine () macrocycle that shows benzene-like electronic properties. Its mesityl derivative, , was isolated in crystalline form. X-ray analysis reveals a symmetry, and the bond lengths of the benzenoid/quinoid rings are averaged via resonance.

Solution-processed nanographene distributed feedback lasers.

The chemical synthesis of nanographene molecules constitutes the bottom-up approach toward graphene, simultaneously providing rational chemical design, structure-property control and exploitation of their semiconducting and luminescence properties. Here, we report nanographene-based lasers from three zigzag-edged polycyclic aromatics. The devices consist of a passive polymer film hosting the nanographenes and a top-layer polymeric distributed feedback resonator.

peri-Acenoacenes.

We report the challenging synthesis and electronic properties of a new class of rhombic peri-fused acene dimers, the so-called peri-acenoacenes. Compared to rectangular peri-fused peri-acenes, peri-acenoacenes show less diradical character and higher stability. Two soluble and stable aryl-substituted peri-acenoacenes, peri-tetracenotetracene (TT-Ar) and peri-pentacenopentacene (PP-Ar), are synthesized and their structures are confirmed by X-ray crystallographic analysis.

Graphene-like Molecules with Four Zigzag Edges.

An efficient synthetic method toward graphene-like molecules (GLMs), having four zigzag edges, is described. They were obtained as stable materials and their structures were confirmed by X-ray crystallographic analysis. They exhibit topology- and size-dependent electronic properties and global aromaticity, which are all different from GLMs having either all-armchair edges, or three zigzag edges, or two armchair/two zigzag edges.

Multifunctional mononuclear bisthienylethene-cobalt(II) complexes: structures, slow magnetic relaxation and photochromic behavior.

Based on two new bisthienylethenes containing N,O-donor binding sites, 2-(2-hydroxy-5-bromo-phenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (BrLH) and 2-(2-hydroxy-5-diethylphosphono-phenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (PLH), multifunctional mononuclear complexes Co(BrL)2·3CH3OH (1) and Co(PL)2·2CH3OH (2) have been synthesized and characterized by crystallographic analysis. In the molecular structures of 1 and 2, the Co(II) ion adopts a distorted tetrahedral coordination geometry, and is coordinated by two nonequivalent bisthienylethene molecules (BrL− in 1, PL− in 2), showing non-photoactive parallel and photoactive antiparallel conformations, respectively. Compounds 1 and 2 show a distinct distortion of Co(II) coordination geometry, with bond angles of N–Co–N = 112.

A mononuclear cobalt(II)-dithienylethene complex showing slow magnetic relaxation and photochromic behavior.

Mononuclear complex Co(hpbdti)2·3CH3OH (1) was synthesized [hpbdtiH = 2-(2-hydroxyphenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole], showing multiple-step field-induced slow magnetic relaxation behaviors, and photochromic properties in CH2Cl2-CH3CN solution.