Π-conjugated Systems Research Articles

From X- To J-Aggregation: Subtly Managing Intermolecular Interactions for Superior Phototheranostics with Precise 1064 nm Excitation.

The stacking mode in aggregate state results from a delicate balance of supramolecular interactions, which closely affects the optoelectronic properties of organic π-conjugated systems. Then, managing these interactions is crucial for advancing phototheranostics, yet remains challenging. A subtle strategy involving peripheral phenyl groups is debuted herein to transform X-aggregated SQ-H into J-aggregated SQ-Ph, reorienting intermolecular dipole interactions while rationally modulating π-π interactions. Co-assembled with liposomes (DSPE-PEG2000), SQ-Ph nanoparticles (NPs) exhibit low toxicity, superior biocompatibility, and a bathochromic shift to the 1064nm match-excited NIR-II region, with a fluorescence brightness (ε1064nm ΦNIR-II) of 4129M-1 cm-1 and a photothermal conversion efficiency (PCE) of 48.3%. Preliminary in vivo experiments demonstrate that SQ-Ph NPs achieve a signal-to-background ratio (SBR) of up to 14.29 in NIR-II fluorescence imaging (FLI), enabling highly efficient photothermal therapy (PTT) of tumors guided by combined photoacoustic imaging (PAI). This study not only enriches the J-aggregation library but also provides a paradigm for optimizing photosensitizers at the supramolecular level.

Enantioselective construction of silicon-stereogenic vinylsilanes from simple alkenes

The diverse utility of acyclic vinylsilanes has driven the interest in the synthesis of enantioenriched vinylsilanes bearing a Si-stereogenic center. However, the predominant approaches for catalytic asymmetric generation of Si-stereogenic vinylsilanes have mainly relied on transition metal-catalyzed reactions of alkynes with different silicon sources. Here we successfully realize the enantioselective synthesis of linear silicon-stereogenic vinylsilanes with good yields and enantiomeric ratios from simple alkenes under rhodium catalysis. The significance of this transformation lies in its ability to achieve regioconvergent and enantioconvergent conversion, efficiently transforming petroleum-derived isomeric mixtures of olefin feedstocks into a single regio- and stereoisomer product. The practicality of this method is further exemplified by the diverse downstream transformations of these enantioenriched silicon-stereogenic vinylsilanes leveraging the olefin functionality and the leaving group nature of the aryl substituent on silicon as well as the development of chiral π-conjugated double bond systems.

Bonding Features of Period 3 and Period 1 Two-Dimensional Superatoms.

Despite being studied for almost two centuries, aromaticity has always been a controversial concept. We previously proposed a unified aromatic rule for π-conjugated systems by two-dimensional (2D) superatomic-molecule theory, where benzenoid rings are treated as period 2 2D superatoms (3π-◊N, 4π-◊O, 5π-◊F, 6π-◊Ne) and, further, bond to form 2D superatomic molecules. Herein, to build a 2D periodic table, we further extend the theory to period 3 (7π-◊P, 8π-◊S, 9π-◊Cl, 10π-◊Ar) and period 1 (1π-◊H, 2π-◊He) elements. Various polycyclic π-conjugated species, namely, C18H16, C14H12, C18H14, [C21H15]-, and C2B4H4, are treated as ◊Cl2, ◊Cl◊F, ◊S◊F2, ◊P◊F3, and ◊H2 superatomic molecules, respectively, where each 2D superatom achieves π electronic shell-closure via superatomic lone pairs and/or two supercenter-two electron (2sc-2e) bonds. Due to the special π electron arrangement and small superatomic orbital energy gaps, period 3 superatoms engage in novel DD, PD orbital interactions and PD, SD2 hybridizations. This work replenishes the 2D periodic table and their bonding rules.

Excited-State Carrier Dynamics in Semiconducting Heterostructures from Self-Sorted NIR Active Dyes.

Heterostructures comprise two or more different semiconducting materials stacked either as co-assemblies or self-sorted based on their dynamics of aggregates. However, self-sorting in heterostructures is rather significant in improving the short exciton diffusion length and charge separation. Despite small organic molecules being known for their self-sorting nature, macrocyclic are hitherto unknown owing to unrestrained assemblies from extended π-conjugated systems. Herein, two near infrared region (NIR) active molecules comprised of porphyrin appended D-π-D (1) and A-π-A (2) have been reported to show the self-assembled 0D and 2D nanostructures via J-aggregates. Interestingly, the mixture of 1 and 2 reveals self-sorting at the molecular level promoting nanosphere and sheet structures which further rolled over to spheres through π-π stacking leading to core-shell type heterostructure. Consequently, electrical conductivity is 10 times higher than the individual assemblies due to excited state electron transfer from 1 to 2 in a mixture, confirmed by femto second-transient absorption spectroscopy and electrochemical impedance spectroscopy. These results suggest that controlling the self-sorted heterostructures fosters refining the electronic properties which pave the way for designing novel NIR-absorbed molecules for organic solar cells (OSCs).

Engaging a highly fluorescent conjugated polymer network for probing endogenous hypochlorite in macrophage cells: improved sensitivity via signal amplification.

We have employed a triazine-based conjugated polymer network (CPN) for the selective detection of hypochlorite in a semi-aqueous environment. CPNs have been widely employed in gas capture, separation, and adsorption, but the fluorescent properties of CPNs possessing extensive π-conjugated systems tend to be unexplored. Herein, we report the photophysical properties of the CPN and investigate its sensing capability towards hypochlorite. Spectroscopic investigations reveal that the CPN forms π-stacked aggregates in aqueous medium, while loose aggregates were observed to be formed in hydrophobic solvents. The fluorogenic CPN demonstrates remarkable selectivity via fluorescence quenching and a blueshift response towards hypochlorite in a semi-aqueous medium, accompanied by a color change under UV light. Such a turn-off fluorescence response, along with the blue shift upon hypochlorite sensing, was attributed to the oxidation of the sulfur atom of the thiophene functionality of the CPN, consequently resulting in suppression of Intramolecular Charge Transfer (ICT) in the corresponding oxidized adduct. The fluorescence intensity of the CPN exhibits a linear response to hypochlorite concentration, achieving a low detection limit of 1.2 nM. Furthermore, the practical applicability was demonstrated by the detection of hypochlorite in water samples and fluorescent test-paper strips. Additionally, the present system is utilized for bio-imaging of endogenous hypochlorite in RAW 264.7 cells.

Rational design of a carbon nitride photocatalyst with in-plane electron delocalization for photocatalytic hydrogen evolution

Introducing B doping into the π-conjugated system of CN not only induces electron delocalization but enhances the separation and transfer of photoinduced electron–hole pairs. This leads to a 8.6-fold improvement in the photocatalytic H2 evolution.

Synthesis and Electrochromic Properties of Ferrocene-Aryl Dicyanovinylene-Based Donor-Acceptor Systems.

The favorable redox properties of ferrocene have led to the extensive development of ferrocene-based systems for several electrochemical applications but have scarcely been explored for electrochromism. Here, we report the synthesis and electrochromic properties of novel π-conjugated ferrocene-dicyanovinylene systems (M1-M5 and D1-D3). Monosubstituted (M1-M5) and disubstituted (D1-D3) compounds have been developed via Knoevenagel condensation of methyl-dicyanovinyl ferrocenes (4 or 5) with various aromatic aldehydes. The compounds' optical (λmax = 320-515 nm) and electronic properties (band gap = 2.6-3.1 eV) have been tuned by the appropriate choice of the aryl substituents. The strong D-A interactions between ferrocene and dicyanovinylene moieties rendered intense colors in the solution and thin-film state and demonstrated high-contrast electrochromism. The electrochromic behavior of these compounds is highly reversible (>48 cycles) and fast (0.98-1.06 s) in both solution and thin-film states. These are the first examples of stand-alone ferrocene systems explored for electrochromism.

Design, DFT, experimental, and NLO studies of a new hybrid containing 1,3,4-oxadiazole and indole moieties

Abstract In this article, design and nonlinear optical (NLO) response studies of a new synthesized hybrid molecule (HM 6) containing 1, 3, 4-oxadiazole and indole moieties are introduced. The spatial structure of the target hybrid is analytically determined using 1HNMR, 13CNMR, FT-IR, UV–vis., and Mass spectra. Efficiency of the fully optimized geometry of the synthesized HM (6) is elucidated via energy gap (EHOMO-ELUMO), potential ionization, and electron affinity. The small energy gap leads to efficient NLO response. The cooperation of 1, 3, 4-oxadiazol moiety as a good acceptor and indole as a good donor in the HM (6) enhances long π-conjugation system, led to large hyperpolarizability (β = 2.79 × 10−28 esu). Density functional theory and TD-DFT-assisted calculations proved high potential intramolecular charge transfer and effective β value verify NLO activities. The NLO activities of the HM (6) are examined under the excitation with 473 nm, single transverse, low power laser beam via diffraction patterns (DPs), and Z-scan techniques. As high as 5.49 × 10−11 m2/W of nonlinear refractive index due to the DPs technique has been obtained. Both the nonlinear refractive index and nonlinear absorption coefficient are estimated via the standard Z-scan methods. The all-optical switching, both static and dynamic, prove to occur in the HM (6) using two visible laser beams.

Triggering the Interplay of sp2-sp3 Carbon-Assisted Sustained Tribofilm via Two-Dimensional Surface Modulation for Exceptional Wear Resistance of Steel Surfaces.

The relentless wear and friction of steel-based moving machinery have created ongoing challenges that hinder their industrial applications. One promising solution is the use of reduced graphene oxide (rGO) as a lubricant due to its excellent mechanical strength and promising tribological properties. However, its tendency to self-agglomerate presents a major hurdle for its practical use. This study aims to combat the restacking of rGO nanosheets by strategically intercalating self-assembled α-ZrP between the rGO layers, unlocking exceptional wear resistance in mild steel through hot-dip galvanization. The multilayer architecture of the developed coatings ensures lubrication through layer slippage during friction, while the coexistence of sp2-sp3 hybridized carbons further extends wear life, with the Zn-0.22/ZP_5@G coating exhibiting the highest wear resistance (0.277 × 10-7 mm3 N-1 m-1). The as-tailored composite coating, featuring a tribolayer composed of graphitic sp2 carbons, ZrO2, Zr(PO4)2, and Fe2O3, serves as an effective dissipative medium for contact stress. The formation of diamond-like sp3 carbons induced by the tribological process further contributes to the increased hardness of the resulting tribofilm. The reduced generation of the π-conjugated system in the composite prevents the movement of electrons toward the cathodic site, while the passivation effect induced by the composite effectively inhibits electrolyte permeation, resulting in substantial corrosion resistance. The exemplary wear resistance with remarkable anticorrosion performance achieved in this study offers significant improvement in the realm of hard coatings for mechanical applications, including moving machinery and manufacturing. Hence, the system can find effective use in such industries following the completion of relevant case studies.

Theoretical insights into H2S desulfurization: Catalysis by binuclear cobalt phthalocyanine

The desulfurization process of H2S catalyzed by binuclear cobalt phthalocyanine (bi-CoPc) has been explored theoretically. With the support of density functional theory (DFT) calculation, the desulfurization mechanism consists of active species and sulfur chain growing. Firstly, the active species has been identified, where the specific electron transfer occurs from HS−, traverses through the phthalocyanine ring, and culminates at O2. This process leads to the formation of Co(I)-Co(I) complexes. Secondly, the sulfur chain growing to S2 on bi-CoPc and detaching in the form of S22− have been considered as the optimal path. Furthermore, a feasible and efficient bi-CoPc-based catalysts with larger π-conjugated system (naphthyl or anthracyl) has been proposed, seem to positively impact electron storage capacity and desulfurization efficiency.

RGB photoluminescence from single-component hydrocarbon single-crystals: Revealing excited-state dynamics in organic semiconductors

The development of single-component organic materials that exhibit tunable red, green and blue (RGB) luminescence under ambient conditions can pave the way of materials with tailored photophysical properties. The optical behavior of such organic materials is largely determined by their excited-state dynamics of the excitons, which are formed when electrons are excited in the material. The excited-state dynamics of an organic molecules can be sensitively tuned, where even marginal variations in crystal morphology and molecular arrangement can drastically modify their optical behavior. Herein, we report a discovery of π-conjugated single-component system that can exhibit the RGB emission. This was realized by altering the morphological crystal dimensionality of a highly tunable single-component hydrocarbon coronene molecule in a single-step crystallization processes into 1D wire, 2D plate, and 3D rod, without introducing additional components or varying external stimuli. Time-resolved photoluminescence (PL) and transient absorption spectroscopy revealed the excited-state absorption (ESA) and self-trapped exciton (STE) formation in the excited electrons in 1D wire crystal plays a key role in emission color change from blue to green. Furthermore, static PL and absorption spectroscopy and single-crystal XRD revealed the dimerization of coronene results in significant reduction of optical band-gap energy and red shift into red emission band. We elucidated the complex relationship between excited-state dynamics and crystal structure of the coronene crystals. Our work presents a novel strategy for tuning the optical properties of single-component organic materials through crystal engineering, offering new possibilities for the development of advanced organic semiconducting devices.

Enhanced Charge Transfer in Poly(Heptazine Imide) Synergistically Induced by Donor-Acceptor Motifs and Ohmic Junctions for Efficient Photocatalytic CO2 Reduction.

Poly(heptazine imide) (PHI) has received widely interest in the photocatalytic CO2 reduction due to its good crystallinity and complete in-plane structure. However, its poor photo-induced carrier separation and migration efficiency and insufficient active sites results in undesirable photocatalytic CO2 reduction performance. Herein, we designed and constructed a novel ohmic junction photocatalyst by integrating melamine edge-modified PHI (mel-PHI) with extended π-conjugated system with TiN (TiN/mel-PHI) for enhancing the photocatalytic CO2 reduction activity. Strikingly, the photocatalytic CO2 reduction yield of the optimal TiN/mel-PHI is 62.64 μmol g-1 h-1, which is 5.6 and 2.8 times higher than PHI (11.26 μmol g-1 h-1) and mel-PHI (22.32 μmol g-1 h-1), respectively. The superior photocatalytic CO2 reduction activity is attributed not only to the formation of D-A structure by the introduction of melamine, which extends the π-conjugation system, alters the electronic structure of PHI, and accelerates the charge separation and migration, but also to the induced internal electric field by ohmic junction further enhances the charge separation and migration efficiency. Meanwhile, the synergistic effect of mel-PHI and TiN enriched the electron number of TiN, reducing the CO2 reduction potential. This work highlights the synergistic enhancement of charge transfer between D-A motifs and ohmic junctions, confirming their potential in optimizing photocatalysts.

Phosphonylation of Conjugated Polymers By Redox Mediator-Induced Electrochemical Post-Functionalization

π-Conjugated polymers (CPs) are attractive optoelectronic materials due to the extended π-conjugation systems along with their main chains.1 Considering the π-conjugation systems, the introduction of functional groups or units into the aromatic main chain is an effective method to modify the properties of CPs. To introduce functional groups or units into molecules, an electrochemical reaction is a straightforward strategy due to its mild reaction conditions and reaction controllability. To date, electrochemical post-functionalization of CPs in the film state has been explored.2,3 Although this electrochemical reaction can realize the C–H functionalization with a simple protocol, the yield is not high owing to the detachment of polymer films during electrolysis. Given these challenges, there is a rising interest in another electrochemical post-functionalization approaches such as the use of redox mediators to functionalize dissolved polymer precursors.Nevertheless, there have been a few reports on electrochemical post-functionalization in a homogeneous state because of inefficient electron transfer at the limited reaction field of the working electrode (Figure 1 (a)). To enhance the efficiency, indirect electrolysis is a suitable approach (Figure 1 (b)).4 In this method, redox mediators (i.e., triphenylamine derivatives) are activated at an electrode, facilitating the electron transfer between the activated mediators and dissolved CPs (Figure 1 (b)). In this study, we aimed to achieve electrochemical post-functionalization in a homogeneous state through indirect electrochemical polymer reactions such as anodic phosphonylation.To investigate the electron transfer between redox mediators and CPs, we preformed cyclic voltammetry measurements of polyfluorene (PFO) and tris(2,4-dibromophenyl)amine (Ar3N) (Figure 1 (c)). Comparing the voltammograms, the oxidation current of the mediators was increased and the reduction current was decreased in the presence of CPs. This behavior indicates that the electron transfer occurred between the PFO and the mediator. The indirect anodic phosphonylation of PFO was carried out using triethyl phosphite as a nucleophile (Figure 1 (d)), and then we obtained phosphonylated PFO (PFO-Phos(Et)) (yield: 56%, degree of substitution: 0.58). In this presentation, the more detailed results and discussion will be explained.References(1) Qiu, Z.; Hammer, B. A. G.; Müllen, K. Conjugated Polymers – Problems and Promises. Prog. Polym. Sci. 2020, 100, 101179.(2) Taniguchi, K.; Kurioka, T.; Shida, N.; Tomita, I.; Inagi, S. Postfunctionalization of the Main Chain of Poly(3-Hexylthiophene) via Anodic C–H Phosphonylation. Polym. J. 2022, 54 (10), 1171–1178.(3) Kurioka, T.; Inagi, S. Electricity‐Driven Post‐Functionalization of Conducting Polymers. Chem. Rec. 2021, 21 (9), 2107–2119.(4) Francke, R.; Little, R. D. Redox catalysis in organic electrosynthesis: basic principles and recent developments. Chem. Soc. Rev. 2014, 43, 2492–2521. Figure 1

Pyrene Derived Donor-Acceptor as a Host for Fullerene Unveils the Crystallinity in Semiconducting Nanostructures.

Donor-acceptor in linear π-conjugated systems elicits the intramolecular charge transfer which improves the optical and electronic characteristics. Nevertheless, linear arrangement of electron donor and acceptor finely tune the charge or electron transfer process divulges the device performance. Therefore, molecular engineering of appropriate D-A with precise spacer is indeed challenging. Herein, we synthesized two bispyrene derivatives and attached with benzothiadazole and phenyl group through imidazole spacer (PyBTD and PyBz). PyBTD has shown solvatochromism demonstrates the intramolecular charge transfer (ICT) from pyrene to benzothiadiazole while PyBz remains as pristine spectra. Microscopic images reveal that network-type structures for PyBTD and elongated nanorods from self-assemblies of PyBz. Subsequently, host-guest interactions suggest that C60 was encapsulated in concave shaped bispyrene controls their crystallinity in nanostructures leads short nanosheets. Impedance analyses depict ICT assisted nanowires facilitate improved conductivity than host-guest complex. Therefore, imidazole spacer between D-A systems paves the way to design such type of molecules for future generated optoelectronics.

Electron-Deficient Indenofluorene-Based Systems: Multicolor and Visible-To-Near-Infrared (NIR) Electrochromism and OFF-OFF-ON Electrofluorochromism.

Multifunctional electrochromic systems with divergent functions are highly sought after but rare and challenging to develop. Here, we report the synthesis and multi-functional electrochromic behaviour (multi-colour modulation, visible-to-near IR absorption switching, and electrofluorochromism) of electron-deficient indenofluorene-based systems. The compounds (IF1-IF5) have been obtained via Knoevenagel condensation of indenofluorenone (IFK) with various nucleophiles (malononitrile, benzylcyanide, dimethyl malonate, methyl cyanoacetate, benzothiazole-2-acetonitrile). IF1-IF5 possess strong colours and absorb in the visible region (λmax=295-388 nm). These compounds are electroactive and exhibit two reversible reduction waves (-0.35--0.88 V and -0.65--1.30 V vs Ag/AgCl), generating radical anion and dianion systems. For the electrochromic studies, upon applying the one-electron reduction potential (-0.35 V vs Ag/AgCl), the absorption maximum of IF1 redshift from 382 nm to 1240 nm (IF1 -⋅), which subsequently blueshifts to 466 & 745 nm (IF1 2-⋅) upon increasing to two-electron reduction potential (-0.65 V vs Ag/AgCl). The color of the solution was switched from green to dark blue and further to light orange. The electrochromic behaviour is highly reversible and cycling. In addition, unlike the non-fluorescent (IF1 and IF1 -⋅), the two-electron reduced system (IF1 2-⋅) is red-emissive (λem=630 nm) due to the combination of radicals leading to the formation of antiaromatic quinoidal π-conjugated system (IF1 2-).

Non-alternant Benzodifluoranthene Tetraimides from 7,8,9,10-Fluoranthene Diimides: Synthesis, Structure, and Optical-Limiting Properties.

A novel tetraimide-functionalized non-alternant π-conjugated system, namely, benzodifluoranthene tetraimides (BDFTI), has been designed and synthesized through highly efficient UV-photocyclization of a vinyl-bridged fluoranthene diimide dimer (i.e., FDI-V). The synthesis of FDI-V starts from a straightforward three-step route to produce novel 7,8,9,10-fluoranthene diimide (FDIs) building-blocks, followed by nearly complete bromination and then Stille-coupling reaction to give the desired dimer. The analysis by X-ray crystallography confirms a near-coplanar geometry for FDIs, while BDFTI shows a U-shaped and distorted backbone configuration proven by theoretical optimizations. The tetraimide BDFTI exhibits several advantages over the FDI cores, including an extended absorption band and a red-shift in photoluminescence spectra. This enhancement can be attributed to the presence of additional electron-deficient imide units, which promotes increased intramolecular charge transfer and improved electron affinity. All the imides show a local aromatic characteristic owing to the incorporation of pentagon rings in the π-frameworks. The fully fused BDFTI exhibits nonlinear optical properties as analyzed by the open-aperture Z-scan technique, demonstrating superior optical-limiting performance compared to vinyl-bridged FDI-V. The versatile UV-photocyclization chemistries provide a pathway for developing complex and unique multiimide-functionalized π-conjugated systems, paving the way for creating high-performance optical-limiting materials.

Diarenofuran[b]-fused BODIPYs: One-Pot SNAr-Suzuki Synthesis and Properties.

We present a streamlined methodology that integrates regioselective tetrahalogen-BODIPY and o-hydroxyphenylboronic acid in a one-pot process, leveraging SNAr nucleophilic substitution in conjunction with Suzuki coupling to afford diarenofuran [b]-fused BODIPYs (DBFB1-9) with commendable yields (85-95%) and short reaction times (0.5-1.0 h). X-ray structure analyses of DBFB5,7-9 elucidate that these diarenofuran[b]-fused BODIPYs adopt a "butterfly" conformation, maintaining a highly rigid planarity. A comprehensive examination of the spectroscopic and electrochemical properties of these diarenofuran[b]-fused BODIPY derivatives, incorporating various substituents, reveals intriguing characteristics, including pronounced absorption and emission in the near-infrared region (NIR), elevated fluorescence quantum yields (ΦF = 75-89% in dichloromethane), and tunable HOMO-LUMO levels. Remarkably, compared to DBFB1-8, DBFB9 possesses a large extended π-conjugated system, resulting in significant red shifts in its absorption and emission maxima, reaching 623 and 635 nm, respectively, and a reduced HOMO-LUMO gap. Despite this substantial structural expansion, DBFB9 maintains a surprisingly high fluorescence quantum yield (ΦF = 80%), underscoring its exceptional photophysical performance and strong potential for applications requiring efficient NIR emission and robust fluorescence retention.

Positional isomers and non-covalent interactions of acrylonitrile-methylpyridinium iodide salts: Combined experimental and quantum chemical calculations investigations

Quaternary salts d-π-A+X- having a large π-conjugated system (I) 2-((Z)-1-cyano-2-[4-(dimethylaminophenyl]ethenyl)-1-methylpyridin-1-ium iodide, (II) 3-((Z)-1-cyano-2-[4-(dimethylaminophenyl]ethenyl)-1-methylpyridin-1-ium iodide, and (III) 4-((Z)-1-cyano-2 iodide -[4-(dimethylaminophenyl]ethenyl)-1-methylpyridin-1-ium iodide, were synthesized straightforwardly and easily and characterized by single-crystal X-ray diffraction, IR, UV–Vis, 1HNMR spectroscopy, DSC, and TGA. Quantum chemical calculations were performed to obtain electronic structure by using DFT. The salts I-III exhibited a hyperchromic shift and a strong bathochromic effect of 100 nm compared to the precursors, which indicates charge transfer (CT) due to ionic interactions. The Hirshfeld, MEPS, QTAIM, and NCI-RDG analyses showed that the -CN group and the counterion I(-) atom play major roles in the intermolecular interaction for crystal packing. The significance of non-covalent interactions for the stability of the molecules in their solid state is also revealed by natural bond orbital analysis.

Synthesis of an Insulated Oligo(phenylene ethynylene) Dimer Through Cyclodextrin-Based [c2]Daisy Chain Rotaxane

Oligo(phenylene ethynylene)s (OPEs) are π-conjugated systems with promising optical, bioactive, and electrical properties, making them valuable candidates for molecular electronics and biosensors. Controlling the arrangement and orientation of π-conjugated systems is crucial in developing molecular devices. Recently, we developed insulated diarylacetylene dimers using a [c2]daisy chain rotaxane strategy, which brings two cores into close proximity without covalent bonding and shields them with permethylated α-cyclodextrins. Here, we synthesized an insulated OPE dimer using a similar rotaxane strategy to investigate its optical properties. The rotaxane structure and optical properties were evaluated using nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization high-resolution mass spectrometry (ESI-HRMS), and absorption and fluorescence spectroscopy. This study is expected to contribute to the development of optical and electronic materials utilizing OPEs.

Highly Strained, Fully π-Conjugated Porphyrin Cyclophanes: Template-free Synthesis and Global Aromaticity.

Porphyrin-based nanohoops, nanorings, and cages with fully π-conjugated structures are highly sought after, but their synthesis remains challenging. Herein, we report the template-free synthesis of a highly strained, bithiophene-bridged porphyrin cyclophane (1) from a porphyrin quinone via a stereoselective nucleophilic addition followed by intermolecular Yamamoto coupling strategy. X-ray crystallographic analyses of 1 and its dication 12+ reveal significantly distorted cyclophane-like geometries, with calculated strain energies of 51.2 and 80.7 kcal/mol, respectively. While the neutral compound 1 exhibits localized aromaticity, the dication 12+ is globally aromatic, with the porphyrin unit displaying weak antiaromaticity. Additionally, the dication 12+ undergoes nucleophilic addition with chloride, relieving strain. This work presents a novel synthetic strategy for highly strained, fully π-conjugated systems with intriguing electronic properties and chemical reactivity.