Quantum Chemical Study of Potential Energy Surface in the Formation of Atmospheric Sulfuric Acid?

A new potential energy surface (PES) for the atmospheric formation of sulfuric acid from OH+SO₂ is investigated using density functional theory and high-level ab initio molecular orbital theory. A pathway focused on the new PES assumes the reaction to take place between the radical complex SO₃·HO₂ and H₂O. The unusual stability of SO₃·HO₂ is the principal basis of the new pathway, which has the same final outcome as the current reaction mechanism in the literature but it avoids the production and complete release of SO₃. The entire reaction pathway is composed of three consecutive elementary steps:(1) HOSO₂+O₂→SO₃·HO₂, (2) SO₃·HO₂+H₂O→SO₃·H₂O·HO₂, (3) SO₃·H₂O·HO₂→H₂SO₄+HO₂. All three steps have small energy barriers, under 10 kcal/mol, and are exothermic, and the new pathway is therefore favorable both kinetically and thermodynamically. As a key step of the reactions, step (3), HO₂ serves as a bridge molecule for low-barrier hydrogen transfer in the hydrolysis of SO₃. Two significant atmospheric implications are expected from the present study. First, SO₃ is not released from the oxidation of SO₂ by OH radical in the atmosphere. Second, the conversion of SO₂ into sulfuric acid is weakly dependent on the humidity of air.     

Intramolecular hydrogen bond in the hydroxycyclohexadienyl peroxy radicals

The hydroxycyclohexadienyl peroxy radicals (HO? C₆H₆? O₂) produced from the reaction of OH‐benzene adduct with O₂ were studied with density functional theory (DFT) calculations to determine their characteristics. The optimized geometries, vibrational frequencies, and total energies of 2‐hydroxycyclohexadienyl peroxy radical II_s and 4‐hydroxycyclohexadienyl peroxy radical III_s were calculated at the following theoretical levels, B3LYP/6‐31G(d), B3LYP/6‐311G(d,p), and B3LYP/6‐311+G(d,p). Both were shown to contain a red‐shifted intramolecular hydrogen bond (O? H … O? H bond). According to atoms‐in‐molecules (AIM) analysis, the intramolecular hydrogen bond in the 2‐hydroxycyclohexadienyl peroxy radical II_s is stronger than that one in 4‐hydroxycyclohexadienyl peroxy radical III_s, and the former is the most stable conformation among its isomers. Generally speaking, hydrogen bonding in these radicals plays an important role to make them more stable. Based on natural bond orbital (NBO) analysis, the stabilization energy between orbitals is the main factor to produce red‐shifted intramolecular hydrogen bond within these peroxy radicals. The hyperconjugative interactions can promote the transfer of some electron density to the O? H antibonding orbital, while the increased electron density in the O? H antibonding orbital leads to the elongation of the O? H bond and the red shift of the O? H stretching frequency. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Water Vapor Enhancement of Rates of Peroxy Radical Reactions

Peroxy radicals can complex with water vapor. These complexes affect tropospheric chemistry. In this study, β‐HEP (hydroxyethyl peroxy radical) serves as a model system for investigating the effect of water vapor on the kinetics and product branching ratio of the self‐reaction of peroxy radicals. The self‐reaction rate coefficient was determined at 274–296 K with water vapor between 1.0 × 10¹⁵ and 2.5 × 10¹⁷ molecules cm^?3 at 200 Torr total pressure by slow‐flow laser flash photolysis coupled with UV time‐resolved spectroscopy and long‐path, wavelength modulated, diode‐laser spectroscopy. The overall self‐reaction rate constant expressed as the product of both a temperature‐dependent and water vapor–dependent term is , suggesting formation of a β‐HEP‐H₂O complex is responsible for the increase in the self‐reaction rate coefficient with increasing water concentration. Complex formation is supported by computational results identifying three local energy minima for the β‐HEP‐H₂O complex. As the troposphere continues to get warmer and wetter, more of the peroxy radicals present will be complexed with water. Investigating the effect of water vapor on kinetics of atmospherically relevant radicals and determining the effects of these altered kinetics on tropospheric ozone concentrations is thus important.     

Tracking the Process of a Solvothermal Domino Reaction Leading to a Stable Triheteroarylmethyl Radical: A Combined Crystallographic and Mass‐Spectrometric Study

A new free carbon radical was obtained in a microwave‐assisted solvothermal reaction of the primary amine (1‐methyl‐1H‐benzo[d]imidazol‐2‐yl)methanamine with FeCl₃?6 H₂O in methanol at 140 °C. Through a combination of crystallography and electrospray ionization mass spectrometry, the reaction process was studied. The longest domino reaction includes 14 steps and forms up to 12 new covalent bonds (9 C?N and 3 C?C bonds) and 3 five‐membered heterocycles. For the first time, the homolytic cleavage of a C?O bond was used to synthesize a triarylmethyl radical.     

Direct Arylation of N‐Heteroarenes with Aryldiazonium Salts by Photoredox Catalysis in Water

A highly effective visible light‐promoted “radical‐type” coupling of N‐heteroarenes with aryldiazonium salts in water has been developed. The reaction proceeds at room temperature with [Ru(bpy)₃]Cl₂ ? 6 H₂O as a photosensitizer and a commercial household light bulb as a light source. Pyridine and a variety of substituted pyridines are effective substrates under these reaction conditions, and only monosubstituted products are formed with different regioselectivities. Using aqueous formic acid as solvent, an array of xanthenes, thiazole, pyrazine, and pyridazine are compatible with this new arylation approach. The broad substrate scope, mild reaction conditions, and use of water as reaction solvent make this procedure a practical and environmentally friendly method for the synthesis of compounds containing aryl‐heteroaryl motifs.     

Visible‐Light‐Induced Water Oxidation Mediated by a Mononuclear‐Cobalt(II)‐Substituted Silicotungstate

A mononuclear‐cobalt(II)‐substituted silicotungstate, K₁₀[Co(H₂O)₂(γ‐SiW₁₀O₃₅)₂] ? 23 H₂O (POM‐ 1 ), has been evaluated as a light‐driven water‐oxidation catalyst. With in situ photogenerated [Ru(bpy)₃]³⁺ (bpy=2,2′‐bipyridine) as the oxidant, quite high catalytic turnover number (TON; 313), turnover frequency (TOF; 3.2 s^?1), and quantum yield (Φ_QY; 27 %) for oxygen evolution at pH 9.0 were acquired. Comparison experiments with its structural analogues, namely [Ni(H₂O)₂(γ‐SiW₁₀O₃₅)₂]^10? (POM‐ 2 ) and [Mn(H₂O)₂(γ‐SiW₁₀O₃₅)₂]^10? (POM‐ 3 ), gave the conclusion that the cobalt center in POM‐ 1 is the active site. The hydrolytic stability of the title polyoxometalate (POM) was confirmed by extensive experiments, including UV/Vis spectroscopy, linear sweep voltammetry (LSV), and cathodic adsorption stripping analysis (CASA). As the [Ru(bpy)₃]²⁺/visible light/sodium persulfate system was introduced, a POM–photosensitizer complex formed within minutes before visible‐light irradiation. It was demonstrated that this complex functioned as the active species, which remained intact after the oxygen‐evolution reaction. Multiple experimental parameters were investigated and the catalytic activity was also compared with the well‐studied POM‐based water‐oxidation catalysts (i.e., [Co₄(H₂O)₂(α‐PW₉O₃₄)₂]^10? (Co₄‐POM) and [Co^IIICo^II(H₂O)W₁₁O₃₉]^7? (Co₂‐POM)) under optimum conditions.     

Oxidative and Photochemical Stability of Ionomers for Fuel‐Cell Membranes

To predict hydroxyl‐radical‐initiated degradation of new proton‐conducting polymer membranes based on sulfonated polyetherketones (PEK) and polysulfones (PSU), three nonfluorinated aromatics are chosen as model compounds for EPR experiments, aiming at the identification of products of HO^.‐radical reactions with these monomers. Photolysis of H₂O₂ was chosen as the source of HO^. radicals. To distinguish HO^.‐radical attack from direct photolysis of the monomers, experiments were carried out in the presence and absence of H₂O₂. A detailed investigation of the pH dependence was performed for 4,4′‐sulfonylbis[phenol] ( SBP ), bisphenol A (= 4,4′‐isopropylidenebis[phenol]; BPA ), and [1,1′‐biphenyl]‐4,4′‐diol ( BPD ). At pH ≥ pK_A of HO^. and H₂O₂, reactions between the model compounds and O₂^.? or ¹O₂ are the most probable ways to the phenoxy and ‘semiquinone’ radicals observed in this pH range in our EPR spectra. A large number of new radicals give evidence of multiple hydroxylation of the aromatic rings. Investigations at low pH are particularly relevant for understanding degradation in polymer‐electrolyte fuel cells (PEFCs). However, the chemistry depends strongly on pH, a fact that is highly significant in view of possible pH inhomogeneities in fuel cells at high currents. It is shown that also direct photolysis of the monomers leads to ‘semiquinone’‐type radicals. For SBP and BPA , this involves cleavage of a C? C bond.     

A supramolecular hydrogen‐bonded complex between 1,3,5‐tris(diisobutylhydroxysilyl)benzene and trans‐bis(4‐pyridyl)ethylene

The trisilanol 1,3,5‐(HOi‐Bu₂Si)₃C₆H₃ ( 7 ), prepared in three steps from 1,3,5‐tribromobenzene via the intermediates 1,3,5‐(Hi‐Bu₂Si)₃C₆H₃ ( 8 ) and 1,3,5‐(Cli‐Bu₂Si)₃C₆H₃ ( 9 ) forms an equimolar complex with trans‐bis(4‐pyridyl)ethylene (bpe), 7 ·bpe, whose structure was investigated by X‐ray crystallography. The hydrogen‐bonded network features a number of SiO? H(H)Si and SiO? H hydrogen bridges. Evidence was found for cooperative strengthening within the sequential hydrogen bonds. Copyright © 2007 John Wiley & Sons, Ltd.     

The Dependence on H2O and on NH3 of the Kinetics of the self-reaction of HO2 in the gas-phase formation of HO2·H2O and HO2·NH3 complexes

Electron pulse radiolysis at ?298°K of 2 atm H₂ containing 5 torr O₂ produces HO₂ free radical whose disappearance by reaction (1), HO₂ + HO₂ →H₂O₂ + O₂, is monitored by kinetic spectrophotometry at 230.5 nm. Using a literature value for the HO₂ absorption cross section, the values k₁ = 2.5×10^?12 cm³/molec·sec, which is in reasonable agreement with two earlier studies, and G(H) G(HO₂) ?13 are obtained. In the presence of small amounts of added H₂O or NH₃, the observed second-order decay rate of the HO₂ signal is found to increase by up to a factor of ?2.5. A proposed kinetic model quantitatively explains these data in terms of the formation of previously unpostulated 1:1 complexes, HO₂ + H₂O ? HO₂·H₂O (4a) and HO₂ + NH₃? HO₂·NH₃ (4b), which are more reactive than uncomplexed HO₂ toward a second uncomplexed HO₂ radical. The following equilibrium constants, which agree with independent theoretical calculations on these complexes, are derived from the data: 2×10^?20?K_4a?6.3 × 10^?19 cm³/molec at 295°K and K_4b = 3.4 × 10^?18 cm³/molec at 298°K. Several deuterium isotope effects are also reported, including k_H/k_D = 2.8 for reaction (1). The atmospheric significance of these results is pointed out.     

Water effect on peroxy radical measurement by chemical amplification: Experimental determination and chemical mechanism

The water effect on peroxy radical measurement by chemical amplification was determined experimentally for HO2 and HO2 OH, respectively at room temperature (298±2) K and atmospheric pressure (1×105 Pa). No significant difference in water effect was observed with the type of radicals. A theoretical study of the reaction of HO2·H2O adduct with NO was performed using density functional theory at CCSD(T)/6-311 G(2d, 2p)//B3LYP/6-311 G(2d, 2p) level of theory. It was found that the primary reaction channel for the reaction is HO2·H2O NO→HNO3 H2O (R4a). On the basis of the theoretical study, the rate constant for (R4a) was calculated using Polyrate Version 8.02 program. The fitted Arrenhnius equation for (R4a) is k = 5.49×107 T 1.03exp(?14798/T) between 200 and 2000 K. A chemical model incorporated with (R4a) was used to simulate the water effect. The water effect curve obtained by the model is in accordance with that of the experiment, suggesting that the water effect is probably caused mainly by (R4a).     

A Crystalline Diazadiborinine Radical Cation and Its Boron‐Centered Radical Reactivity

One‐electron oxidation of 1,4,2,5‐diazadiborinine 1 has been studied. While the reaction of 1 a bearing phenyl groups on the B atoms with AgAl{OC(CF₃)₃}₄ afforded a complex mixture, the same oxidation reaction with 1 b featuring bulky mesityl substituents on the B atoms rendered the corresponding cation radical 2 b as an isolable species. X‐ray diffraction analysis, EPR spectroscopy, and DFT calculations of 2 b revealed the delocalization of the unpaired electron over the entire π‐system of 2 b , as well as a large spin density (0.76 in total) on the two equivalent boron atoms. The chemical trapping reaction of 2 b with p‐benzoquinone and triphenyltin hydride afforded the dicationic species 3 containing two newly formed B?O bonds and the monocationic product 2b‐H containing a B?H bond, respectively, thus confirming the boron‐centered radical reactivity of 2 b .     

Coupling Interactions between Sulfurous Acid and the Hydroperoxyl Radical

Radical–molecule complexes associated with the hydroperoxyl radical (HOO) play an important role in atmospheric chemistry. Herein, the nature of the coupling interactions between sulfurous acid (H₂SO₃) and the HOO radical is systematically investigated at the B3LYP/6‐311++G(3df,3pd) level of theory in combination with the atoms in molecules (AIM) theory, the natural bond orbital (NBO) method, and energy decomposition analyses (EDA). Eight stable stationary points possessing double H‐bonding features were located on the H₂SO₃???HOO potential energy surface. The largest binding energies of ?12.27 and ?11.72 kcal mol^?1 are observed for the two most stable complexes, where both of them possess strong double intermolecular H‐bonds of partially covalence. Moreover, the characteristics of the IR spectra for the two most stable complexes are discussed to provide some help for their possible experimental identification.     

Kinetic studies of the self‐reaction and reaction with HO2 of a tertiary β‐brominated peroxy radical between 298 and 393 K

The kinetics of reactions of the tertiary β‐brominated peroxy radical BrC(CH₃)₂C(CH₃)₂O₂ (2‐bromo‐1,1,2‐trimethylpropylperoxy) have been studied using the laser flash photolysis technique, photolysing HBr at 248 nm in the presence of O₂ and 2,3‐dimethylbut‐2‐ene. At room temperature, a rate constant of (2.0 ± 0.8) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹ was determined for the BrC(CH₃)₂C(CH₃)₂O₂ self‐reaction. The reaction of BrC(CH₃)₂C(CH₃)₂O₂ with HO₂ was investigated in the temperature range 306–393 K, yielding the following Arrhenius expression: k(BrC(CH₃)₂C(CH₃)₂O₂ + HO₂) = (2.04 ± 0.25) × 10⁻¹² exp[(501 ± 36)K/T] cm³ molecule⁻¹ s⁻¹, giving by extrapolation (1.10 ± 0.13) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 298 K. These results confirm the enhancement of the peroxy radical self‐reaction reactivity upon β‐substitution, which is similar for Br and OH substituents. In contrast, no significant effect of substituent has been observed on the rate constant for the reactions of peroxy radicals with HO₂. The global uncertainty factors on rate constants are equal to nearly 2 for the self‐reaction and to 1.35 for the reaction with HO₂. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 41–48, 2001     

5‐(1,2,3‐Triazol‐1‐yl)tetrazole Derivatives of an Azidotetrazole via Click Chemistry

N? C bonded (non‐bridged) 5‐(1,2,3‐triazol‐1‐yl)tetrazoles were synthesized by the Cu^I‐catalyzed 1,3‐dipolar azide–alkyne cycloaddition click reaction using 5‐azido‐N‐(propan‐2‐ylidene)‐1H‐tetrazole ( 1 ). For example, the click reaction of 1 in the presence of CuSO₄?5 H₂O and Na ascorbate at 65–70 °C for 48 h in CH₃CN/H₂O co‐solvent was found to be limited to only terminal alkynes that have electron‐withdrawing groups, CF₃C?CH ( 2 a ) and SF₅C?CH ( 2 b ), giving rise to isopropylidene‐[5‐(4‐trifluoromethyl‐1,2,3‐triazol‐1‐yl)tetrazol‐1‐yl]amine ( 3 a ) and isopropylidene‐[5‐(4‐pentafluorosulfanyl‐1,2,3‐triazol‐1‐yl)tetrazol‐1‐yl]amine ( 3 b ) in 47 % and 66 % yields, respectively. When carried out under conditions using CuI and 2,6‐lutidine as catalysts at 0 °C for 13 h in CHCl₃, the click reaction was versatile toward alkynes even those having electron‐donating groups. Properties of new products were determined and compared with those of 1 . Heats of formation, detonation pressures, detonation velocities and impact sensitivities are reported for these new 5‐(1,2,3‐triazol‐1‐yl)tetrazoles.     

Guest‐Triggered Supramolecular Isomerism in a Pillared‐Layer Structure with Unusual Isomers of Paddle‐Wheel Secondary Building Units by Reversible Single‐Crystal‐to‐Single‐Crystal Transformation

Solvothermal reaction of Zn(NO₃)₂ ? 4 H₂O, 1,4‐bis[2‐(4‐pyridyl)ethenyl]benzene (bpeb) and 4,4′‐oxybisbenzoic acid (H₂obc) in the presence of dimethylacetamide (DMA) as one of the solvents yielded a threefold interpenetrated pillared‐layer porous coordination polymer with pcu topology, [Zn₂(bpeb)(obc)₂] ? 5 H₂O ( 1 ), which comprised an unusual isomer of the well‐known paddle‐wheel building block and the trans–trans–trans isomer of the bpeb pillar ligand. When dimethylformamide (DMF) was used instead of DMA, a supramolecular isomer [Zn₂(bpeb)(obc)₂] ? 2 DMF ? H₂O ( 2 ), with the trans–cis–trans isomer of the bpeb ligand with a slightly different variation of the paddle‐wheel repeating unit, was isolated. In MeOH, single crystals of 2 were transformed by solvent exchange in a single‐crystal‐to‐single‐crystal (SCSC) manner to yield [Zn₂(bpeb)(obc)₂] ? 2 H₂O ( 3 ), which is a polymorph of 1 . SCSC conversion of 3 to 2 was achieved by soaking 3 in DMF. Compounds 1 and 2 as well as 2 and 3 are supramolecular isomers.     

A Free‐Radical Prompted Barrierless Gas‐Phase Synthesis of Pentacene

A representative, low‐temperature gas‐phase reaction mechanism synthesizing polyacenes via ring annulation exemplified by the formation of pentacene (C₂₂H₁₄) along with its benzo[a]tetracene isomer (C₂₂H₁₄) is unraveled by probing the elementary reaction of the 2‐tetracenyl radical (C₁₈H₁₁^.) with vinylacetylene (C₄H₄). The pathway to pentacene—a prototype polyacene and a fundamental molecular building block in graphenes, fullerenes, and carbon nanotubes—is facilitated by a barrierless, vinylacetylene mediated gas‐phase process thus disputing conventional hypotheses that synthesis of polycyclic aromatic hydrocarbons (PAHs) solely proceeds at elevated temperatures. This low‐temperature pathway can launch isomer‐selective routes to aromatic structures through submerged reaction barriers, resonantly stabilized free‐radical intermediates, and methodical ring annulation in deep space eventually changing our perception about the chemistry of carbon in our universe.     

Mechanism and Kinetics of the Reaction of Nitrosamines with OH Radical: A Theoretical Study

The reaction of nitrosodimethylamine, nitrosoazetidine, nitrosopyrrolidine, and nitrosopiperidine with the hydroxyl radical has been studied using electronic structure calculations in gas and aqueous phases. The rate constant was calculated using variational transition state theory. The reactions are initiated by H‐atom abstraction from the αC─H group of nitrosamines and leads to the formation of alkyl radical intermediate. In the subsequent reactions, the initially formed alkyl radical intermediate reacts with O₂ forming a peroxy radical. The reaction of peroxy radical with other atmospheric oxidants, such as HO₂ and NO radicals, is studied. The structures of the reactive species were optimized by using the density functional theory methods, such as M06‐2X, MPW1K, and BHandHLYP, and hybrid methods G3B3. The single‐point energy calculations were also performed at CCSD(T)/6‐311+G(d,p)// M062X/6‐311+G(d,p) level. The calculated thermodynamical parameters show that the reactions corresponding to the formation of intermediates and products are highly exothermic. We have calculated the rate constant for the initial H‐atom abstraction and subsequent favorable secondary reactions using canonical variational transition state theory over the temperature range of 150–400 K. The calculated rate constant for initial H‐atom abstraction reaction is ∼3 × 10⁻¹² cm³ molecule⁻¹ s⁻¹ and is in agreement with the previous experimental results. The calculated thermochemical data and rate constants show that the reaction profile and kinetics of the reactions are less dependent on the number of methyl groups present in the nitrosoamines. Furthermore, it has been found that the atmospheric lifetime of nitrosamines is around 5 days in the normal atmospheric OH concentration.     

Gas‐Phase Reaction of Monomethylhydrazine with Ozone: Kinetics and OH Radical Formation

The gas‐phase reaction of monomethylhydrazine (CH₃NH? NH₂; MMH) with ozone was investigated in a flow tube at atmospheric pressure and a temperature of 295 ± 2 K using N₂/O₂ mixtures (3–30 vol% O₂) as the carrier gas. Proton transfer reaction–mass spectrometry (PTR‐MS) and long‐path FT‐IR spectroscopy served as the main analytical techniques. The kinetics of the title reaction was investigated with a relative rate technique yielding k_MMH+O3 = (4.3 ± 1.0) × 10^?15 cm³ molecule^?1 s^?1. Methyldiazene (CH₃N?NH; MeDia) has been identified as the main product in this reaction system as a result of PTR‐MS analysis. The reactivity of MeDia toward ozone was estimated relative to the reaction of MMH with ozone resulting in k_MeDia+O3 = (2.7 ± 1.6) × 10^?15 cm³ molecule^?1 s^?1. OH radicals were followed indirectly by phenol formation from the reaction of OH radicals with benzene. Increasing OH radical yields with increasing MMH conversion have been observed pointing to the importance of secondary processes for OH radical generation. Generally, the detected OH radical yields were definitely smaller than thought so far. The results of this study do not support the mechanism of OH radical formation from the reaction of MMH with ozone as proposed in the literature.     

On the Role of Pre‐ and Post‐Electron‐Transfer Steps in the SmI2/Amine/H2O‐Mediated Reduction of Esters: New Mechanistic Insights and Kinetic Studies

The mechanism of the SmI₂‐mediated reduction of unactivated esters has been studied using a combination of kinetic, radical clocks and reactivity experiments. The kinetic data indicate that all reaction components (SmI₂, amine, H₂O) are involved in the rate equation and that electron transfer is facilitated by Brønsted base assisted deprotonation of water in the transition state. The use of validated cyclopropyl‐containing radical clocks demonstrates that the reaction occurs via fast, reversible first electron transfer, and that the electron transfer from simple Sm(II) complexes to aliphatic esters is rapid. Notably, the mechanistic details presented herein indicate that complexation between SmI₂, H₂O and amines affords a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to carboxylic acid derivatives as an attractive alternative to the classical hydride‐mediated reductions and as a source of acyl‐radical equivalents for C?C bond forming processes.     

Strong Lewis Acids of Air‐Stable Metallocene Bis(perfluorooctanesulfonate)s as High‐Efficiency Catalysts for Carbonyl‐Group Transformation Reactions

Strong Lewis acids of air‐stable metallocene bis(perfluorooctanesulfonate)s [M(Cp)₂][OSO₂C₈F₁₇]₂?nH₂O?THF (M=Zr ( 2 a ?3 H₂O?THF), M=Ti ( 2 b ?2 H₂O?THF)) were synthesized by the reaction of [M(Cp)₂]Cl₂ (M=Zr ( 1 a ), M=Ti ( 1 b )) with nBuLi and C₈F₁₇SO₃H (2 equiv) or with C₈F₁₇SO₃Ag (2 equiv). The hydrate numbers (n) of these complexes were variable, changing from 0 to 4 depending on conditions. In contrast to well‐known metallocene triflates, these complexes suffered no change in open air for a year. thermogravimetry–differential scanning calorimetry (TG‐DSC) analysis showed that 2 a and 2 b were thermally stable at 300 and 180 °C, respectively. These complexes exhibited unusually high solubility in polar organic solvents. Conductivity measurement showed that the complexes ( 2 a and 2 b ) were ionic dissociation in CH₃CN solution. X‐ray analysis result confirmed 2 a ?3 H₂O?THF was a cationic organometallic Lewis acid. UV/Vis spectra showed a significant red shift due to the strong complex formation between 10‐methylacridone and 2 a . Fluorescence spectra showed that the Lewis acidity of 2 a fell between those of Sc³⁺ (λ_em=474 nm) and Fe³⁺ (λ_em=478 nm). ESR spectra showed the Lewis acidity of 2 a (0.91 eV) was at the same level as that of Sc³⁺ (1.00 eV) and Y³⁺ (0.85 eV), while the Lewis acidity of 2 b (1.06 eV) was larger than that of Sc³⁺ (1.00 eV) and Y³⁺ (0.85 eV). They showed high catalytic ability in carbonyl‐compound transformation reactions, such as the Mannich reaction, the Mukaiyama aldol reaction, allylation of aldehydes, the Friedel–Crafts acylation of alkyl aromatic ethers, and cyclotrimerization of ketones. Moreover, the complexes possessed good reusability. On account of their excellent catalytic efficiency, stability, and reusability, the complexes will find broad catalytic applications in organic synthesis.