Crown Ether Complexes Research Articles

Crystallization Control to Prepare Uniform CsPbI2Br Thin Films for High-Efficiency Perovskite Solar Cells.

All-inorganic perovskite solar cells (PSCs) face challenges related to film inhomogeneity, which arises from nonideal crystallization. This issue significantly impedes the advancement of all-inorganic PSCs. In this study, we observed that during the crystallization process of CsPbI2Br, the Br-rich intermediate phase is often preferentially deposited, leading to an uneven distribution in the out-of-plane direction of the perovskite film. To address this issue, crown ether molecules (dibenzo-18-crown-6) were introduced into the perovskite precursor solution. The complexation of crown ether with Cs cations and Br anions optimizes the crystallization sequence of the perovskite, ensuring that the intermediate phase closely conforms to the standard stoichiometric ratio. This adjustment significantly mitigates the problem of uneven halogen ion distribution along the out-of-plane direction. Furthermore, the crown ether thermally decomposes during the high-temperature annealing process, thereby not affecting the composition of the final perovskite film. Following crown ether treatment, the efficiency of the PSCs reached 14.08%, and the unpackaged devices maintained 80% of their initial efficiency after 1000 h of exposure to light in an atmospheric environment.

Dichlorido(crown ether)lanthanoid(III) tetrachloroaluminate complexes

Reactions between LnCl3, AlCl3 and a crown ether (18-crown-6 and dibenzo18-crown-6) in MeCN have led to the isolation of four new lanthanoid halide crown ether complexes, [PrCl(μ-Cl)(18-crown-6)]2[AlCl4]2·2MeCN (1), [YbCl2(18-crown-6)][AlCl4]·MeCN (2), and [LnCl(μ-Cl)(dibenzo18-crown-6)}2][AlCl4]2·6.5MeCN (Ln = La, 3, Pr, 4). 1 was also obtained by unexpected halide transfer on addition of 18-crown-6 (18C6) to MeCN solutions of [Pr(MeCN)9][AlCl4]3. Complexes 1, 3 and 4 have dinuclear chloride-bridged nine-coordinate cations, and 2 has an eight coordinate mononuclear cation.

Synthesis and characterization of alkali metal iminophosphoranomethanide complexes

Herein we report the synthesis of three sets of alkali metal complexes with the iminophosphoranomethanide ligands {CH(SiMe3)P(Ph)2NSiMe3}− (TMSNPC-H) and {CH(SiMe2tBu)P(Ph)2NSiMe3}− (TBDMSNPC-H), the latter of which is first reported here. The compounds of general formula [M(RNPC-H)] (3-M and 4-M; M = Li, Na, K) were obtained via a protonolysis reaction between an alkyl reagent (n-butyllithium, benzylsodium, or benzylpotassium) and the proligand. All resulting compounds were characterized by multinuclear NMR, IR spectroscopy, elemental analysis and single crystal X-ray diffraction. We also attempted to prepare the separated ion pairs of [M(TMSNPC-H)] with the matched crown ethers, and obtained the ‘ate’ complexes [Li(12-crown-4)2]+[Li(TMSNPC-H)2]− (5-Li) and [Na(15-crown-5)2]+[Na(TMSNPC-H)2]− (5-Na), the coordination polymer [{K(18-crown-6)2}{K(TMSNPC-H)(18-crown-6)}(TMSNPC-H)]∞ (6) and separate ion pair complex [K(15-crown-5)2]+[TMSNPC-H]− (7). 5-Li is an unusual lithium-lithiate crown ether species, whilst 5-Na represents the first example of a sodium-sodiate crown-ether complex.

Catalytic synthesis of flavanone without stirring or heating

We developed a new approach for the synthesis of flavanone from chalcones without electrical energy, such as stirring or heating, by using a cesium fluoride–crown ether complex. This “zero electrical energy reaction” is a new category of reaction that has the potential to replace the general organic reaction.

Synthesis of cationic lanthanoid tetraphenylborate crown ether complexes

The efficacy of Me3NHBPh4 as a protolytic agent in the generation of reactive lanthanoid cations has been further explored. Reaction of [Nd(BH4)3(thf)4] with Me3NHBPh4 in a 1:3 mole ratio, and dibenzo-18-crown-6 (DB18C6) in thf did not yield [Nd(thf)n][BPh4]3, but [Nd(BH4)2(DB18C6)][BPh4]⋅2THF (1), a complex primed for further functionalisation, was isolated. The structure has an eight coordinate Nd atom with two trans tridentate BH4− ligands. Redox transmetallation/protolysis (RTP) reactions between Yb metal, PhHgC6F5, and Me3NHBPh4 in the presence of 18-crown-6 (18C6) or DB18C6 in MeCN or in thf followed by work up with MeCN yields [Yb(CE)(MeCN)3][BPh4]2⋅nMeCN (CE = 18C6, n = 0 (2), and DB18C6 n = 3 (3)), the structures of which have nine coordinate Yb atoms. Two pairs of MeCN ligands are transoid, whereas the third pair have a small cis NYbN angle. In the absence of a crown ether ligand, the RTP reaction in MeCN yields the known [Yb(MeCN)8] [BPh4]2.

Synthesis, Isolation, and Study of Heterobimetallic Uranyl Crown Ether Complexes.

Although crown ethers can selectively bind many metal cations, little is known regarding the solution properties of crown ether complexes of the uranyl dication, UO22+. Here, the synthesis and characterization of isolable complexes in which the uranyl dication is bound in an 18-crown-6-like moiety are reported. A tailored macrocyclic ligand, templated with a Pt(II) center, captures UO22+ in the crown moiety, as demonstrated by results from single-crystal X-ray diffraction analysis. The U(V) oxidation state becomes accessible at a quite positive potential (E1/2) of -0.18 V vs Fc+/0 upon complexation, representing the most positive UVI/UV potential yet reported for the UO2n+ core. Isolation and characterization of the U(V) form of the crown complex are also reported here; there are no prior reports of reduced uranyl crown ether complexes, but U(V) is clearly stabilized by crown chelation. Joint computational studies show that the electronic structure of the U(V) form results in significant weakening of U-Ooxo bonding despite the quite positive reduction potential at which this species can be accessed, underscoring that crown-ligated uranyl species could demonstrate unique reactivity under only modestly reducing conditions.

Strong dependence of air stability on thickness in n-doped carbon nanotube thermoelectrics

We demonstrate that the observed (in-)stability of n-doped carbon nanotube films in air not only depends on the employed dopant but is also strongly affected by sample-specific factors, such as the film thickness and density. We show this for two typical dopants, polyethylenimine and a potassium crown ether complex, by preparing films of increasing thickness. We argue that reports on dopant stability cannot be properly assessed without knowledge of these sample-specific parameters, which explains some of the conflicting results in the literature.

Bis-Alkoxide Dysprosium(III) Crown Ether Complexes Exhibit Tunable Air Stability and Record Energy Barrier.

High-performance and air-stable single-molecule magnets (SMMs) can offer great convenience for the fabrication of information storage devices. However, the controversial requisition of high stability and magnetic axiality is hard to balance for lanthanide-based SMMs. Here, a family of dysprosium(III) crown ether complexes possessing hexagonal-bipyramidal (pseudo-D6h symmetry) local coordination geometry with tunable air stability and effective energy barrier for magnetization reversal (Ueff) are shown. The three complexes share the common formula of [Dy(18-C-6)L2][I3] (18-C-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; L = I, 1; L = OtBu 2 and L = 1-AdO 3). 1 is highly unstable in the air. 2 can survive in the air for a few minutes, while 3 remains unchanged in the air for more than 1 week. This is roughly in accordance with the percentage of buried volumes of the axial ligands. More strikingly, 2 and 3 show progressive enhancement of Ueff and 3 exhibits a record high Ueff of 2427(19) K, which significantly contributes to the 100 s blocking temperature up to 11 K for Yttrium-diluted sample, setting a new benchmark for solid-state air-stable SMMs.

Rapid Quantification of Ammonium Nitrate and Urea Nitrate Using Liquid Chromatography-High-Resolution Orbitrap Mass Spectrometry.

Resolution and sensitivity improvements in mass spectrometry technology have enabled renewed attempts at solving challenging analytical issues. One such issue involves the analysis of energetic ionic species. Energetic ionic species make up an important class of chemical materials, and a more robust and versatile analytical platform would provide tremendous value to the analytical community. Initial attempts at quantification of energetic ionic species employed high-resolution time-of-flight measurements with crown ether (CE) complexation and flow injection analysis (FIA). In this investigation, ammonium nitrate (AN) and urea nitrate (UN) in the presence of a crown ether complexation agent were explored by using high-resolution orbitrap mass spectrometry. Product ion scans of these signature complexes reveal positive identification of these energetic ionic species. Finally, quantification was demonstrated for both flow injection and liquid chromatography-mass spectrometry (LC-MS) analysis, suggesting the capability for routine and rapid analysis of these energetic ionic materials.

Intra-host π-π interactions in crown ether complexes revealed by cryogenic ion mobility-mass spectrometry.

Cryogenic ion mobility-mass spectrometry was performed to investigate the relative abundance of conformers of dinaphtho-24-crown-8 (DN24C8) complexes with alkali metal cations M+ (M = Li, Na, K, Rb, and Cs). The "closed" conformers of M+(DN24C8) with short distances between two naphthalene rings in the crown ethers were predominantly observed for all complexes at 86 K. The two noncovalent interactions, host-guest and intra-host interactions, were analyzed separately by density functional theory calculations to reveal the origin of the stability of the closed conformers. As a result, it was revealed that the intra-host π-π interactions have a more critical role in determining the stability of the conformers than the host-guest interactions. The closed conformers of M+(DN24C8) also have wider regions of the π-π interactions than those of the M+(dibenzo-24-crown-8) complexes.

Trifluoromethyl anion: Generation, stability, and SNAr reactivity in crown ether complex analyzed by theoretical calculations

The trifluoromethyl anion is a reactive species useful for the trifluoromethylation reaction of organic compounds. However, this species is prone to an elimination process via the generation of CF2 or reaction with water or alcohols by protonation, limiting its potential application in synthesis. Complexation of the in situ generated KCF3 salt with crown ethers increases its stability. In this work, we have investigated theoretically the generation, stability, and SNAr reactivity of the CF3− anion in the K+(18-crown-6)(CF3−) complex towards different substrates. Our results point out that the TESCF3 reagent is a good source of the CF3− anion under reaction with potassium methoxide, whereas the HCF3 species is less effective. The formal elimination of CF2 takes place via the [K+(18-crown-6)(CF3−)]2 dimeric species with overall ΔG‡ = 18.7 kcal mol−1, and the transient carbene interacts with another CF3− forming CF2CF3−. Six substrates were investigated for the SNAr reaction with K+(18-crown-6)(CF3−) complex. The reaction with phenyl bromide is very unfavorable, with ΔG‡ = 29.7 kcal mol−1. Two activating groups such as CN in the ortho and para positions are needed to produce an enough low barrier of ΔG‡ = 14.2 kcal mol−1, able to compete with the decomposition of the CF3− anion.

Crown Ether Complexes with Alkaline Earth Metal Chlorides as Catalysts for the Decomposition of Isopropylbenzene Hydroperoxide

Crown Ether Complexes with Alkaline Earth Metal Chlorides as Catalysts for the Decomposition of Isopropylbenzene Hydroperoxide

Crown Ether Complexes with Alkaline Earth Metal Chlorides ‒ Catalysts for the Decomposition of Isopropylbenzene Hydroperoxide

Kinetic and thermodynamic parameters of the decomposition of isopropylbenzene hydroperoxide in chlorobenzene in the presence of dibenzo-18-crown-6 ether (DBK) complexes with CaCl2, SrCl2, BaCl2 have been experimentally obtained. The catalytic activity of alkaline earth metal compounds decreases in the series SrCl2·DBK CaCl2·DBK BaCl2·DBK. The formation of intermediate intermediates in the metal‒complex-hydroperoxide system has been kinetically established. SrCl2·DBK forms the strongest and most ordered structures with isopropylbenzene hydroperoxide, which decay at the highest rates. The formation of intermediate intermediates has been confirmed using quantum chemical modeling.

Crown ether complexes as a possible template for hybrid organic–inorganic borates

Abstract Crystals of the first new organo–inorganic hybrid borate based on potassium crown ether complex, [K(C12H24O6)B5O6(OH)4](H2O) (1), have been produced from aqueous solutions and characterized by single-crystal X-ray diffraction. 1 crystalizes is orthorhombic system, Pnma, a = 10.1684(3) Å, b = 11.6289(3) Å, c = 21.2247(6) Å, V = 2509.76(12) Å3, R obs = 0.059. The structure of 1 consists of molecular [K(C12H24O6)B5O6(OH)4]0 complexes, common for crown ether complexes but yet not among borates, with a very rare monodentate coordination of the common pentaborate anion(1-). The molecular complexes are linked into weak chains via hydrogen bonding to outer-sphere water molecules. Hirshfeld surfaces analysis and complexity measurement of 1 were performed. Perspectives of borate structures containing crown ether complexes as templates are briefly outlined.

Free Energy Calculations and Conformational Analysis of Dibenzo-30-crown-10 with Sm2+, Eu2+, and Three Halide Salts in THF Using the AMOEBA Force Field.

Crown ether complexes have been tailored for use in industrial separations of lanthanides (Ln) as a part of rare earth mining and refining. Dibenzo-30-crown-10 (DB30C10) is one of the most efficient complexants for the separation of rare earth mixtures based on the cation size. To understand the origin of this complexation, molecular dynamics (MD) simulations of DB30C10 have been performed using different combinations of divalent Sm and Eu and three halide salts Cl-, Br-, and I- in tetrahydrofuran (THF) solvent. DB30C10 was parameterized here for the polarizable atomic multipole optimized energetics for biomolecular simulation (AMOEBA) force field, and the existing parameters of THF, Sm2+, and Eu2+ were employed from our previous efforts. The large conformational fluctuations present in the DB30C10 systems were found to be dependent both on the identity of the lanthanide and halide complexes. For Cl- and Br- systems, there were no observed conformational changes at 200 ns, while in I- systems, there were two conformational changes with Sm2+ and one with Eu2+ within that same timeframe. In SmI2-DB30C10, there were three stages of conformational changes. In the first stage, the molecule is unfolded, in the second stage, the molecule is partly folded, and finally, in the third stage, the molecule is completely folded. Lastly, the Gibbs binding free energies of DB30C10 with SmBr2 and EuBr2 have been computed, which resulted in nearly identical ΔGcomp values for each lanthanide with Sm2+ being slightly more favorable. Considering the folding mechanism of the SmI2 system with DB30C10, the Gibbs binding free energies of DB30C10 and dicyclohexano-18-crown-6 (DCH18C6) with SmI2 were calculated separately and compared to probe their complexation affinities, in which the former was found to be more favorable.

Ab Initio Calculations on the Ground and Excited Electronic States of Thorium-Ammonia, Thorium-Aza-Crown, and Thorium-Crown Ether Complexes.

Positively charged metal-ammonia complexes are known to host peripheral, diffuse electrons around their molecular skeleton. The resulting neutral species form materials known as expanded or liquid metals. Alkali, alkaline earth, and transition metals have been investigated previously in experimental and theoretical studies of both the gas and condensed phase. This work is the first ab initio exploration of an f-block metal-ammonia complex. The ground and excited states are calculated for Th0-3+ complexes with ammonia, crown ethers, and aza-crown ethers. For Th3+ complexes, the one valence electron Th populates the metal's 6d or 7f orbitals. For Th0-2+, the additional electrons prefer occupation of the outer s- and p-type orbitals of the complex, except Th(NH3)10, which uniquely places all four electrons in outer orbitals of the complex. Although thorium coordinates up to ten ammonia ligands, octa-coordinated complexes are more stable. Crown ether complexes have a similar electronic spectrum to ammonia complexes, but excitations of electrons in the outer orbitals of the complex are higher in energy. Aza-crown ethers disfavor the orbitals perpendicular to the crowns, attributed to the N-H bonds pointing along the plane of the crowns.

Isolation of a californium(II) crown–ether complex

The actinides, from californium to nobelium (Z = 98-102), are known to have an accessible +2 oxidation state. Understanding the origin of this chemical behaviour requires characterizing CfII materials, but investigations are hampered by the fact that they have remained difficult to isolate. This partly arises from the intrinsic challenges of manipulating this unstable element, as well as a lack of suitable reductants that do not reduce CfIII to Cf°. Here we show that a CfII crown-ether complex, Cf(18-crown-6)I2, can be prepared using an Al/Hg amalgam as a reductant. Spectroscopic evidence shows that CfIII can be quantitatively reduced to CfII, and rapid radiolytic re-oxidation in solution yields co-crystallized mixtures of CfII and CfIII complexes without the Al/Hg amalgam. Quantum-chemical calculations show that the Cf‒ligand interactions are highly ionic and that 5f/6d mixing is absent, resulting in weak 5f→5f transitions and an absorption spectrum dominated by 5f→6d transitions.

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells

AbstractHost‐guest complexation has demonstrated potential for controlling hybrid organic‐inorganic metal halide perovskite materials. In particular, crown ethers have been used due to their capacity to interact with metal cations (e. g., Pb2+) and small organic cations (e. g., methylammonium (MA)), which can affect hybrid perovskite materials and their solar cells. However, this strategy has been underexploited in perovskite photovoltaics, and the underlying mechanisms are not well understood. In this study, we investigate the influence of 15‐crown‐5 (15C5) and its benzannulated derivative (benzo‐15‐crown‐5, B15C5), as well as amino‐functionalized analogues (15‐crown‐5)‐2‐methylamine, 2A‐15C5, and 4′‐aminobenzo‐15‐crown‐5, 4A‐B15C5, on MAPbI3 perovskite crystallization and inverted solar cell performance. We demonstrate the propensity of crown ether modulators to interact with Pb2+ cations at the perovskite interface by density functional theory calculations. This has been shown to facilitate oriented crystal growth and homogeneous film formation, as revealed by X‐ray diffraction analysis complemented by scanning electron microscopy. As a result, we demonstrate an increase in the power conversion efficiency of the solar cells of interest to advancing hybrid photovoltaics.

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells