Solution-based Synthesis Research Articles

Solid–Solution–Solid (SSS) phase transitions for Gram-Scale and High-Throughput synthesis of noble metal nanoparticles in deep eutectic solvents

Modern colloidal chemistry has enabled the controlled synthesis of various noble metal nanoparticles with unique physical and chemical properties. However, solution-based synthesis still suffers from limited productivity, particularly in industrial applications. We have developed the gram-scale synthesis of gold nanoparticles (AuNPs) using a polymerizable deep eutectic solvent (DES) via solid–solution–solid phase transitions. The DES plays two important roles, as a designer solvent. First, the solvating power of the DES allows the precursors to dissolve easily, even at high concentrations. Second, the concomitant polymerization of the DES with the synthesis of highly concentrated AuNPs and their consequent fixation in the polymer matrix is crucial for their stabilization. This rapid one-pot synthesis provides the highest productivity, among the other previously reported gram-scale syntheses of AuNPs. The procedure can be easily extended to conduct multiple reactions in a high-throughput manner. The chemical and physical properties and synthesis mechanisms of the AuNPs are thoroughly investigated. The synthesis of other noble metal (Pd, Ag, Au) nanoparticles, which are mono- and bimetallic, has also been demonstrated using the DES. As a practical application, a large-area transparent display is demonstrated using AuNPs synthesized in the DES, implying the scope for further industrial applications.

Rapid and solvent-free mechanochemical synthesis of Na iron hexacyanoferrate for high-performance Na-ion batteries

Sodium iron hexacyanoferrate (NaFeHCF) containing Fe as the only transition metal element has attained extensive interest for Na-ion batteries due to the low raw material cost and high resource abundance; however, the traditional solution-based synthesis methods, including coprecipitation and hydrothermal reaction, are usually time-consuming and difficult to control the interstitial water and Na content in the lattice, which puts a challenge on the high-efficiency and controllable preparation of NaFeHCF. Herein, we demonstrate a rapid and solvent-free mechanochemical route under the Ar atmosphere to synthesize Na1.59Fe[Fe(CN)6]0.95□0.051.92H2O cathode, which delivers an initial discharge capacity of ∼130 mA h g−1 at 0.2 C and 118 mA h g−1 at a high rate of 10 C. Besides, ex situ XRD confirms that NaFeHCF cathode experienced a phase transition from the initial cubic phase to Na-free cubic structure during the first charging process and followed by a reversible phase change between the monoclinic and Na-free cubic structures in the subsequent cycles. More impressively, the optimized NaFeHCF/NaTi2(PO4)3 full cell reveals a decent capacity retention of 80% over 1000 cycles at 1 C, exhibiting a promising prospect in the practical application. Our current work sheds light on the high-efficient scalable production of high-performance NaFeHCF cathodes for Na-ion batteries via mechanochemical approach.

Sonochemically-coated transparent wood with ZnO: Passive radiative cooling materials for energy saving applications

Improving the energy efficiency of buildings through the use of enhanced passive radiative cooling materials would have a great relief to the global energy and climate crises. Through a purely solution-based sonochemical synthesis method raising no requirements on temperature and vacuum, we fabricated a ZnO-coated transparent wood (CTW) composite with high emissivity (∼0.91) across infrared wavelengths, allowing great potential for radiative cooling applications. The CTW exhibited a reasonable luminous transmittance (∼66.04% at a film thickness of ∼360 nm) for both visual comfort and luminous purposes. The ZnO coating improves the mechanical (43% enhancement of tensile strength) and thermal insulation (0.157 W.m−1.K−1) properties of the transparent wood substrate, making it a potential replacement for existing glazing materials. Energy-saving simulations for Hong Kong, Shanghai and Chongqing have revealed that CTW can save up to ∼17% more energy than conventional commercial window materials.

Mechanochemical vs Wet Approach for Directing CO2 Capture toward Various Carbonate and Bicarbonate Networks.

The distinct research areas related to CO2 capture and mechanochemistry are both highly attractive in the context of green chemistry. However, merger of these two areas, i.e., mechanochemical CO2 capture, is still in an early stage of development. Here, the application of biguanidine as an active species for CO2 capture is investigated using both solution-based and liquid-assisted mechanochemical approaches, which lead to a variety of biguanidinium carbonate and bicarbonate hydrogen-bonded networks. We demonstrate that in solution, the formation of the carbonate vs bicarbonate networks can be directed by the organic solvent, while, remarkably, in the liquid-assisted mechanochemical synthesis employing the same solvents as additives, the selectivity in network formation is inversed. In general, our findings support the view of mechanochemistry not only as a sustainable alternative but rather as a complementary strategy to solution-based synthesis.

Counter Anion Effects on the Formation and Structural Transformations of Mo(vi)-Hydrazone Coordination Assemblies: Salts, Solvates, Co-Crystals, and Neutral Complexes

Complex salts [1H]X and [1H](XA)0.5·2MeOH, and co-crystals [1H]X·0.5VA (X = chloride or bromide, XA = chloranilate or bromanilate, VA = o-vanillin azine), comprising [MoO2(HL)(MeOH)]+ ([1H]+) cation (H2L = 3-methoxysalicylaldehyde isonicotinoyl hydrazone), were prepared either by solution-based synthesis or by mechanochemical synthesis. Whereas [1H]X salts were extremely sensitive to humidity, their stability could be reinforced by the azine incorporation into the complex network. Solvent-mediated transformations of [1H]X led to methanol co-ligand replacement and afforded complexes [MoO2(HL)X] (2Cl·MeOH, 2Cl, and 2Br·0.5MeCN). However, solvates [1H](XA)0.5·2MeOH, under the same conditions, gave stable complexes [1H](XA)0.5 in which methanol remained coordinated. The differences in the assembly’s behavior were attributed to the packing arrangements, the relative orientation of cations and anions, and interactions between them. Polymorph [MoO2(L)(MeOH)] (1), not attainable by other routes, was the only product when compounds [MoO2(HL)X] were treated with a weak base at low temperatures. Tetranuclear [MoO2(L)]4 and polynuclear [MoO2(L)]n (2) supramolecular isomers, concomitantly crystallized when the reaction was conducted solvothermally. All of the complexes were characterized using X-ray diffraction methods (SCXRD and PXRD), spectroscopic methods (ATR-IR and solution-state and solid-state MAS NMR), and elemental and thermal analyses. The cytotoxicity of the different types of compounds against THP-1 and HepG2 cells was also evaluated.

Two-dimensional covalent organic framework films prepared on various substrates through vapor induced conversion

Covalent organic frameworks (COFs) can exhibit high specific surface area and catalytic activity, but traditional solution-based synthesis methods often lead to insoluble and infusible powders or fragile films on solution surface. Herein we report large-area –C=N– linked two-dimensional (2D) COF films with controllable thicknesses via vapor induced conversion in a chemical vapor deposition (CVD) system. The assembly process is achieved by reversible Schiff base polycondensation between PyTTA film and TPA vapor, which results in a uniform organic framework film directly on growth substrate, and is driven by π‐π stacking interactions with the aid of water and acetic acid. Wafer-scale 2D COF films with different structures have been successfully synthesized by adjusting their building blocks, suggesting its generic applicability. The carrier mobility of PyTTA-TPA COF films can reach 1.89 × 10−3 cm2 V−1 s−1. When employed as catalysts in hydrogen evolution reaction (HER), they show high electrocatalytic activity compared with metal-free COFs or even some metallic catalysts. Our results represent a versatile route for the direct construction of large-area uniform 2D COF films on substrates towards multi-functional applications of 2D π‐conjugated systems.

Solution route processed and organically-Capped Quinary CuIn1-xGax(SySe1-y)2 (CIGSSe) inks for use in low-cost photovoltaics

Multicomponent chalcogenides are a class of derived materials that present a compelling vision that allows for the realization of benefits that are limited in their pristine counterparts. CIGSSe is one such material that constitutes the dual role of prominent chalcogens, i.e., sulfur and selenium. The benefits possessed due to both sulfur and selenium's presence influence the improvement in properties compared to their other counterparts. The dual role offered by both the constituents is noteworthy as one of them, i.e., sulfur, aids in enhancing the material's bandgap. Simultaneously, the other, i.e., selenium, is responsible for eliminating the porosity in thin-films of these chalcogenides. Comparing the properties of individual CIGSe and CIGS with quinary CIGSSe can lead to the discernment of a material with properties particularly desirable for the potential photovoltaic absorber. To the best of the author's knowledge, the quinary CIGSSe nanocrystals' colloidal synthesis employs organic ligands-TOP(tri octyl phosphine)/TOPO (tri octyl phosphine oxide) has been reported for the first time. Technologically, this solution-based synthesis's main benefit is the ease of formation of the colloidal-ink for a scalable film formation on various compatible substrates (rigid/flexible) via the printing route for photovoltaics application.

Enhancing the Spectroelectrochemical Performance of WO3 Films by Use of Structure-Directing Agents during Film Growth

Thin, porous films of WO3 were fabricated by solution-based synthesis via spin-coating using polyethylene glycol (PEG), a block copolymer (PIB50-b-PEO45), or a combination of PEG and PIB50-b-PEO45 as structure-directing agents. The influence of the polymers on the composition and porosity of WO3 was investigated by microwave plasma atomic emission spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, X-ray diffraction, and gas sorption analysis. The electrochromic performance of the WO3 thin films was characterized with LiClO4 in propylene carbonate as electrolyte. To analyze the intercalation of the Li+ ions, time-of-flight secondary ion mass spectrometry, and X-ray photoelectron spectroscopy were performed on films in a pristine or reduced state. The use of PEG led to networks of micropores allowing fast reversible electrochromic switching with a high modulation of the optical transmittance and a high coloration efficiency. The use of PIB50-b-PEO45 provided isolated spherical mesopores leading to an electrochromic performance similar to compact WO3, only. Optimum characteristics were obtained in films which had been prepared in the presence of both, PEG and PIB50-b-PEO45, since WO3 films with mesopores were obtained that were interconnected by a microporous network and showed a clear progress in electrochromic switching beyond compact or microporous WO3.

Cationic Vacancies in Anatase (TiO2): Synthesis, Defect Characterization, and Ion-Intercalation Properties.

As one of the most studied materials, research on titanium dioxide (TiO2) has flourished over the years owing to technological interest ranging from energy conversion and storage to medical implants and sensors, to name a few. Within this scope, the development of synthesis routes enabling the stabilization of reactive surface structure has been frequently investigated. Among these routes, solution-based synthesis has been utilized to tailor the material's properties spanning its atomic structural arrangement, or morphological aspects. One of the most investigated methods of stabilizing crystals with tailored facets relies on the use of fluoride-based precursors. Fluoride ions not only provide a driving force for the stabilization of metastable/reactive surface structures but also alter the reactivity of titanium molecular precursors and in turn the structural features of the stabilized crystals. Here, we review recent progress in the solution-based synthesis of anatase (one of the polymorphs of TiO2) employing a fluoride precursor, with an emphasis on how cationic vacancies are stabilized by a charge-compensating mechanism and the resulting structural features associated with these defects. Finally, we will discuss the ion-intercalation properties of these sites with respect to lithium and polyvalent ions such as Mg2+ and Al3+. We will discuss in more detail the relevant parameters of the synthesis that allow controlling the phase composition with the coexistence of oxide, fluoride, and hydroxide ions within the anatase framework. The mechanism of formation of defective anatase nanocrystals has highlighted a solid-state transformation mostly implying an oxolation reaction (the condensation of hydroxide ions) that results in a decrease in the vacancy content, which can be synthetically controlled. The investigation of local fluorine environments probed by solid-state 19F NMR revealed up to three coordination modes with different numbers of coordinated Ti4+ and vacancies. It further revealed the occurrence of single and adjacent pairs of vacancies. These different host sites including native interstitial (and single/paired vacancies) display different ion-intercalation properties. We notably discussed the influence of the local anionic environments of vacancies on the thermodynamics of intercalation properties. The selective intercalation of polyvalent cations such as Mg2+ and Al3+ further supports the beneficial uses of defect chemistry for developing post-lithium-ion batteries. It is expected that the ability to characterize the local structure of defects is key to the design of unique, tailored-made materials.

Ionic Liquid-Based Low-Temperature Synthesis of Crystalline Ti(OH)OF·0.66H2O: Elucidating the Molecular Reaction Steps by NMR Spectroscopy and Theoretical Studies.

We present an in-depth mechanistic study of the first steps of the solution-based synthesis of the peculiar hexagonal tungsten bronze-type Ti(OH)OF·0.66H2O solid, using NMR analyses (1H, 13C, 19F, and 11B) as well as modeling based on density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation. The reaction uses an imidazolium-based ionic liquid (IL, e.g., Cxmim BF4) as a solvent and reaction partner. It is puzzling, as the fluorine-rich crystalline solid is obtained in a “beaker chemistry” procedure, starting from simple compounds forming a stable solution (BF4–-containing IL, TiCl4, H2O) at room temperature, and a remarkably low reaction temperature (95 °C) is sufficient. Building on NMR experiments and modeling, we are able to provide a consistent explanation of the peculiar features of the synthesis: evidently, the hydrolysis of the IL anion BF4– is a crucial step since the latter provides fluoride anions, which are incorporated into the crystal structure. Contrary to expectations, BF4– does not hydrolyze in water at room temperature but interacts with TiCl4, possibly forming a TiCl4 complex with one or two coordinated BF4– units. This interaction also prevents the heavy hydrolysis reaction of TiCl4 with H2O but—on the other side—spurs the hydrolysis of BF4– already at room temperature, releasing fluoride and building F-containing Ti(OH)xCl4–xFy complexes. The possible complexes formed were analyzed using DFT calculations with suitable functionals and basis sets. We show in addition that these complexes are also formed using other titanium precursors. As a further major finding, the heating step (95 °C) is only needed for the condensation of the Ti(OH)xCl4–xFy complexes to form the desired solid product but not for the hydrolysis of BF4–. Our study provides ample justification to state a “special IL effect”, as the liquid state, together with a stable solution, the ionic nature, and the resulting deactivation of H2O are key requirements for this synthesis.

Na2B11H13 and Na11(B11H14)3(B11H13)4 as potential solid-state electrolytes for Na-ion batteries.

Solid-state sodium batteries have attracted great attention owing to their improved safety, high energy density, large abundance and low cost of sodium compared to the current Li-ion batteries. Sodium-boranes have been studied as potential solid-state electrolytes and the search for new materials is necessary for future battery applications. Here, a facile and cost-effective solution-based synthesis of Na2B11H13 and Na11(B11H14)3(B11H13)4 is demonstrated. Na2B11H13 presents an ionic conductivity in the order of 10-7 S cm-1 at 30 °C, but undergoes an order-disorder phase transition and reaches 10-3 S cm-1 at 100 °C, close to that of liquids and the solid-state electrolyte Na-β-Al2O3. The formation of a mixed-anion solid-solution, Na11(B11H14)3(B11H13)4, partially stabilises the high temperature structural polymorph observed for Na2B11H13 at room temperature and it exhibits Na+ conductivity higher than its constituents (4.7 × 10-5 S cm-1 at 30 °C). Na2B11H13 and Na11(B11H14)3(B11H13)4 exhibit an oxidative stability limit of 2.1 V vs. Na+/Na.

Compositional and structural control in LLZO solid electrolytes.

Garnet-based solid-state electrolytes (SSEs) represent a promising class of materials for next-generation batteries with improved safety and performance. However, lack of control over the composition and crystal structure of the well-known Li7La3Zr2O12 (LLZO) garnet material has led to poor reproducibility with a wide range of ionic conductivities reported in the literature. In this study, the role of precursor homogeneity in controlling the compositional and structural evolution of Al-doped LLZO is explored. A novel solution-based synthesis approach is employed to demonstrate enhanced atomic-scale mixing of the starting materials in comparison to conventional solid-state preparation methods. Through this technique, it is shown that the stability and formation temperature of the highly conductive cubic phase is directly impacted by the spatial distribution of the doping element and reactant species in the precursor mixture. Precursor homogeneity was also an important factor in mitigating the formation of unwanted secondary impurities. These findings can be used to guide the synthesis of SSEs with reproducible material characteristics and enhanced electrolytic performance.

Solution-based synthesis of wafer-scale epitaxial BiVO4 thin films exhibiting high structural and optoelectronic quality.

We demonstrate a facile approach to solution-based synthesis of wafer-scale epitaxial bismuth vanadate (BiVO4) thin films by spin-coating on yttria-stabilized zirconia. Epitaxial growth proceeds via solid-state transformation of initially formed polycrystalline films, driven by interface energy minimization. The (010)-oriented BiVO4 films are smooth and compact, possessing remarkably high structural quality across complete 2′′ wafers. Optical absorption is characterized by a sharp onset with a low sub-band gap response, confirming that the structural order of the films results in correspondingly high optoelectronic quality. This combination of structural and optoelectronic quality enables measurements that reveal a strong optical anisotropy of BiVO4, which leads to significantly increased in-plane optical constants near the fundamental band edge that are of particular importance for maximizing light harvesting in semiconductor photoanodes. Temperature-dependent transport measurements confirm a thermally activated hopping barrier of ∼570 meV, consistent with small electron polaron conduction. This simple approach for synthesis of high-quality epitaxial BiVO4, without the need for complex deposition equipment, enables a broadly accessible materials base to accelerate research aimed at understanding and optimizing photoelectrochemical energy conversion mechanisms.

Investigation of solution-based synthesis of non-toxic perovskite materials using Mg, Ca, Mn, Fe, Cu, and Zn as the B-site cation for photovoltaic applications

High-efficiency perovskite solar cells are reliant on lead-based materials, which causes toxicity issues for large-scale implementation.

Chemical durability and degradation mechanisms of CsPbI3 as a potential host phase for cesium and iodine sequestration.

Effective nuclear waste management of radioactive cesium and off-gas iodine from complex waste streams of used fuels is essential for the sustainable development of advanced nuclear fuel cycles. Once cesium and iodine are separated from their respective waste streams, host phases are required to immobilize them into a durable waste form matrix for long-term disposition. The inorganic metal halide perovskite, CsPbI3, has a unique crystal structure capable of incorporating both cesium and iodine simultaneously. Exposure to groundwater in geological repositories is a long-term concern for waste forms, as this may cause corrosion and decrease the waste form's ability to retain radionuclides. In this study, we explore the potential of CsPbI3 perovskite as a promising host phase to incorporate Cs and I, and investigate its chemical durability and degradation mechanisms in an aqueous environment. CsPbI3 was synthesized through a solution-based method and was consolidated into dense pellets by spark plasma sintering. The chemical durability of the CsPbI3 pellets was evaluated by static leaching tests in deionized water at different temperatures of 25, 58, and 90 °C. The elemental release mechanisms and surface alteration of the monolithic CsPbI3 pellets were investigated. Both I and Cs displayed a non-congruent leaching behavior and faster release rates as compared to Pb, particularly at longer leaching durations and higher temperatures. At the initial leaching stage, a PbI2 alteration layer formed on the surface of the pellet due to the rapid release of Cs and I, followed by the formation of a PbI(OH) alteration layer. The activation energies for both dissolution and diffusion controlled mechanisms were determined to be 44.90 kJ mol−1 and 45.40 kJ mol−1 for Pb, 27.10 kJ mol−1 and 40.82 kJ mol−1 for I and 24.27 kJ mol−1 and 23.86 kJ mol−1 for Cs, respectively. These results show a clear decrease in activation energies from Pb to I and Cs, suggesting a preferential release of I and Cs. The solution-based synthesis of CsPbI3 as a host phase for Cs and I and the fundamental understanding of the chemical durability and degradation behavior will be useful for further exploring its application for immobilizing iodine and cesium into final durable waste forms for long-term geological disposition.

SOLID-STATE SYNTHESIS, SPECTRAL AND BIOLOGICAL STUDIES OF Fe (II) COMPLEX DERIVED FROM PARACETAMOL

New solid-state metal complex of Fe (II) with paracetamol (ligand), that is, [Fe(para)2Cl2] were synthesized mechanically in 1:2 ratio. The complex has been characterized using physicochemical properties and spectral studies. From the IR and electronic spectral studies, the spectra of the complex were different from that of ligand suggesting the formation of coordination compound. Paracetamol was found to be bidentate ligand in which Fe (II) ion coordinated through the oxygen atom of carbonyl of ketone and nitrogen atom of amide in which the complex is assumed to have octahedral geometry. The complex has shown good antimicrobial activities. The solid-state synthetic method is quick and gives a higher yield, without the need of solvent or heating. Its present higher efficiency in terms of materials, time and energy compared to solution-based synthesis. It is therefore, recommended among others that, solid-state synthesis method should be used in the synthesizing drugs with metals.

Facile solution-based synthesis of impurity-free hydroxyapatite nanocrystals at ambient conditions

Synthesis of nanocrystalline hydroxyapatite with high degree of crystallinity results in improved bioactivity responses due to its high specific surface area and low ion release. Therefore, the innovative methods resulting in these qualities are of significant importance especially for 3D printing of biomaterials and biocomponents made by hydroxyapatite. Addressing the qualities essential for bioperformance of hydroxyapatite, a new method was developed in this work, which is able to prepare impurity-free hydroxyapatite nanocrystals at ambient conditions. Characterization of role of processing conditions and their successive optimization resulted in a facile cost-effective process in contrast to the literature. Stoichiometric nanoscale hydroxyapatite free from by-products, unwanted materials (unwanted phase formation) and impurities was obtained by the approach. It was found that the longer drying time increases the crystallinity of the as-washed precipitate; however, to reach a high degree of crystallinity, application of a heat treatment process is essential. The designed short time heat treatment was able to enhance the crystallinity of the dried precipitate while its structure remained nanoscale after heat treatment. Keeping the nanoscale structure of the samples even after heat treatment allows using its benefits for improvement of biocompatibility, osteoconductivity and tissue in-growth of the biomaterials made by these nanoscale hydroxyapatite powder products. The results showed that the amino acid (glycine) has a significant effect on the crystallinity of the hydroxyapatite due to its effect on kinetic of hydroxyapatite crystallization (nucleation of new crystals) by enhancing the surface diffusion mechanism in the precipitate. In contrast, the glycine also controlled the growth process of the nucleated crystals by its adsorption on the growing surfaces and/or by introducing the strain to the growing crystals. These stresses controlled the growth of the nanocrystals and induced directional growth and morphological changes in the hydroxyapatite powder products.

Solution Synthesis of Sb2S3 and Na3SbS4 Solid-State Electrolyte

Sodium thioantimonate (Na3SbS4) is an attractive solid-state electrolyte for sodium-ion batteries due to its high ionic conductivity and stability in protic solvents. Herein, we describe solution-based routes for its synthesis. First, we demonstrate the synthesis of the Sb2S3 precursor via thermodynamically favorable metathesis between Na2S and SbCl3. This solution-based approach is further extended to couple the resulting Sb2S3 with Na2S for the synthesis of Na3SbS4. It is shown that ethanol is a superior solvent to water for solution-based synthesis of Na3SbS4 with respect to yield, morphology, and performance. Amorphous Sb2S3 synthesized from low-temperature metathesis produced highly crystalline Na3SbS4 with a room temperature Na+ conductivity of 0.52 mS cm−1 and low activation energy, comparable to leading values reported in the literature.

Synthesis of Electrospun NASICON Li1.5Al0.5Ge1.5(PO4)3 Solid Electrolyte Nanofibers by Control of Germanium Hydrolysis

We report the synthesis of ceramic Li1.5Al0.5Ge1.5(PO4)3 (LAGP) nanofibers by combining sol–gel and electrospinning techniques. A homogeneous and stable precursor solution based on chlorides was achieved by controlling Ge hydrolysis. Subsequent electrospinning and heat treatment resulted in highly porous nanostructured NASICON pellets. After a full chemical-physical characterization, various amounts of LAGP nanofibers were used as a filler to develop polyethylene oxide (PEO)-based composite electrolytes. The addition of 10% LAGP nanofibers has allowed doubling the ionic conductivity of the plain polymer electrolyte, by providing longer ion-conductive paths and reducing PEO crystallinity. These findings are promising towards developing solution-based synthesis approaches featuring Ge precursors. In addition, the achieved LAGP nanofibers proved to be a promising nanofiller candidate to develop composite electrolytes for next-generation solid-state batteries.

Facile Synthesis of Azahelicenes and Diaza[8]circulenes through the Intramolecular Scholl Reaction.

Carbazole-based aza[7]helicenes and hetero[9]helicenes were successfully obtained via the intramolecular Scholl reaction of 3,6-bis(biphenyl-2-yl)carbazole congeners, while the reaction of 3,6-bis(naphthylphenyl)-appended carbazole gave a triple helicene via an unexpected simultaneous double aryl rearrangement. DFT calculations suggested that the rearrangement proceeded via an arenium cation intermediate. In addition, the reaction of methoxy-appended substrate gave an azahepta[8]circulene via the concurrent C-C bond formation. These helical dyes showed circularly polarized luminescence. The azahepta[8]circulene was further transformed into deeply saddle-distorted dibenzodiaza[8]circulenes as the first example of its solution-based synthesis and unambiguous structural determination.