Ether Complexes Research Articles

Solvent-induced reversible high-temperature phase transition in crown ether clathrates

The phase transitions of crown ether complexes with molecular motor motion triggered by the solvent-induced effect are reported.

Assessment of a host-guest interaction in a bilayer membrane model.

Supramolecular interactions are well recognized and many of them have been extensively studied in chemistry. The formation of supramolecular complexes that rely on weak force interactions are less well studied in bilayer membranes. Herein, a supported bilayer membrane is used to probe the penetration of a complex between tetracycline and a macrocyclic polyether. In a number of bacterial systems, the presence of the macrocycle has been found to significantly enhance the potency of the antimicrobial in vitro. The crown·tetracycline complex has been characterized in solution, neutron reflectometry has probed complex penetration, and the phenomena have been modeled by computational methods.

A niobium pentafulvene ethylene complex: synthesis, properties and reaction pathways.

The π-η5:σ-η1 coordination mode of early transition metal pentafulvene ligands yields a strongly nucleophilic exocyclic carbon atom (Cexo). The substitution of the chlorido ligand of bis(η5:η1-(di-p-tolyl)pentafulvene)niobium chloride (1) by reaction with ethyl magnesium bromide is subsequently followed by a β-C-H activation employing this Cexo, forming the pentafulvene niobium ethylene complex 2. The intermediately formed ethyl complex can be intercepted with water, protonating both pentafulvene moieties and thereby retaining the ethyl moiety to give the terminal oxo complex 3. Complex 2 shows cooperative reactions of the remaining pentafulvene and the ethylene ligand. While the pentafulvene functions as a proton acceptor, the ethylene can be liberated to provide a NbIII metal center, available for E-H bond addition. Thereby, the imido hydride complex 4 and niobaaziridine hydride 5 are obtained. These hydride complex formations are investigated by deuterium labeling, concluding the redox mechanism. An alternative β-hydride elimination pathway is further disproven by purposely synthesizing a proposed intermediate and thermally treating it, to show that it does not undergo the β-hydride elimination under reaction conditions.

A (partial) resolution of binding enthalpy discrepancies in ITC studies of Ba2+ crown ether complexation: The importance of calibration

By conducting binding experiments at a range of temperatures T using isothermal titration calorimetry (ITC), one can obtain two estimates of the binding enthalpy — calorimetric (ΔH°cal) from the experiments at each T, and van't Hoff (ΔH°vH) from the T dependence of the binding constant K°. From thermodynamics it is clear that these two must be identical, but early efforts to demonstrate this for ITC data indicated significant inconsistency. In an extensive 2004 study of the Ba2+ + 18-crown-6 ether complexation used in prior comparisons, Mizoue and Tellinghuisen found modest (10–20%) but statistically significant differences, which were tentatively attributed to problems converting the calorimetric estimates to their standard state values, as implied by the superscript ° in the notation. In the present work the 2004 results are reanalyzed using results obtained since then from temperature, heat, and volume calibration of the instrument and a better determination of the data variance function required for the weighted least-squares fitting of the data. The new results show consistency for temperatures 5–30 °C but persistent statistically significant differences from 35 to 46 °C. Several possible explanations for the remaining discrepancies are examined, with methods that include fitting the K and ΔHcal data together.

Cationic Effects on the Structural Dynamics of the Metal Ion-Crown Ether Complexes Investigated by Ultrafast Infrared Spectroscopy.

It is usually believed that the binding affinity and selectivity of an alkali metal ion with crown ether are defined by the size matching model. However, the underlying mechanism of the specific host-guest interactions and the structural dynamics of the metal ions confined in the cavity of the crown ethers in the solutions are still not clear. In this report, a series of alkali thiocyanate salts (XSCN; X = Li, Na, K, and Cs) complexed with 18-crown-6 (a typical crown ether) in the chloroform solutions were studied by the polarization-selective infrared pump-probe spectroscopy and the ultrafast two-dimensional infrared (2D IR) spectroscopy. The SCN- counteranions were employed as the local vibrational probe to reveal the specific host-guest interactions in the crown ether complexes. The rotational dynamics and spectral diffusion of SCN- vibration were both measured by ultrafast IR spectroscopy, and it was found that the metal cations hosted by the crown ethers can have a pronounced effect on the rotational dynamics of the counteranions. The reorientational time constants of the SCN- vibration in the complexation follow the order Li+ > Na+ > K+ ≃ Cs+. More importantly, the spectral diffusion dynamics of SCN-, which quantifies the decay of the correlation of the frequency fluctuations in the complexation, was also affected by the metal ions but showed a different order of cationic effect. A detailed analysis of the 2D IR data showed that the spectral diffusion of SCN- counteranion clearly decayed with two different time scales in the complex of 18-crown-6 with K+. The 3-4-fold slowdown in spectral diffusion indicated that the fluctuation of SCN- vibrational transition frequency was strongly affected by the K+ cation due to the geometric constraint imposed by the crown ether. The results should help the researchers to unravel the specific host-guest interactions and further reveal the origination of the binding selectivity of crown ether for metal cations in the condensed phases from the perspective of structural dynamics.

Aromatic Clusters as Potential Hydrogen Storage Materials

The scientific community is engrossed in the thought of a probable solution to the future energy crisis keeping in mind a better environment-friendly alternative. Although there are many such alternatives, the green hydrogen energy has occupied most of the brilliant minds due to its abundance and numerous production resources. For the advancement of hydrogen economy, Government agencies are funding pertinent research projects. There is an avalanche of molecular systems which are studied by several chemists for storing atomic and molecular hydrogens. The present review on molecular hydrogen storage focuses on all-metal and nonmetal aromatic clusters. In addition to the effect of aromaticity on hydrogen trapping potential of different molecular moieties, the importance of using the conceptual density functional theory based reactivity descriptors is also highlighted. Investigations from our group have been revealing the fact that several aromatic metal clusters, metal doped nonmetal clusters as well as pure nonmetal clusters can serve as potential molecular hydrogen trapping agents. Reported systems include N4Li2, N6Ca2 clusters, Mgn, and Can (n = 8–10) cage-like moieties, B12N12 clathrate, transition metal doped ethylene complexes, M3+ (M = Li, Na) ions, E3-M2 (E = Be, Mg, Al; M = Li, Na, K) clusters, Li3Al4− ions, Li decorated star-like molecules, BxLiy (x = 3–6; y = 1, 2), Li-doped annular forms, Li-doped borazine derivatives, C12N12 clusters (N4C3H)6Li6 and associated 3-D functional material, cucurbiturils, lithium–phosphorus double-helices. Ni bound C12N12 moieties are also reported recently.

Modulation of a μ-1,2-Peroxo Dicopper(II) Intermediate by Strong Interaction with Alkali Metal Ions.

The properties of metal/dioxygen species, which are key intermediates in oxidation catalysis, can be modulated by interaction with redox-inactive Lewis acids, but structural information about these adducts is scarce. Here we demonstrate that even mildly Lewis acidic alkali metal ions, which are typically viewed as innocent "spectators", bind strongly to a reactive cis-peroxo dicopper(II) intermediate. Unprecedented structural insight has now been obtained from X-ray crystallographic characterization of the "bare" CuII2(μ-η1:η1-O2) motif and its Li+, Na+, and K+ complexes. UV-vis, Raman, and electrochemical studies show that the binding persists in MeCN solution, growing stronger in proportion to the cation's Lewis acidity. The affinity for Li+ is surprisingly high (∼70 × 104 M-1), leading to Li+ extraction from its crown ether complex. Computational analysis indicates that the alkali ions influence the entire Cu-OO-Cu core, modulating the degree of charge transfer from copper to dioxygen. This induces significant changes in the electronic, magnetic, and electrochemical signatures of the Cu2O2 species. These findings have far-reaching implications for analyses of transient metal/dioxygen intermediates, which are often studied in situ, and they may be relevant to many (bio)chemical oxidation processes when considering the widespread presence of alkali cations in synthetic and natural environments.

Influence of Outer-Sphere Anions on the Photoluminescence from Samarium(II) Crown Complexes.

Three samarium(II) crown ether complexes, [Sm(15-crown-5)2]I2 (1), [Sm(15-crown-5)2]I2·CH3CN (2), and [Sm(benzo-15-crown-5)2]I2 (3), have been prepared via the reaction of SmI2 with the corresponding crown ether in either THF or acetonitrile in good to moderate yields. The compounds have been characterized by single crystal X-ray diffraction and a variety of spectroscopic techniques. In all cases, the Sm(II) centers are sandwiched between two crown ether molecules and are bound by the five etheric oxygen atoms from each crown ether to yield 10-coordinate environments. Despite the higher symmetry crystal class of 1 (R3c), the samarium center resides on a general position, whereas in 2 and 3 (both in P21/c) the metal centers lie upon inversion centers. Moreover, the complexes in 2 and 3 are approximated well by D5d symmetry. The molecule in 1, however, is distorted from idealized D5d symmetry, and the crown ethers are more puckered than observed in 2 and 3. All three complexes luminesce in the NIR at low temperatures. However, the nature of the luminescence differs between the three compounds. 1 exhibits broadband photoluminescence at 20 °C but at low temperatures transitions to narrow peaks. 2 only exhibits nonradiative decay at 20 °C and at low temperatures retains a mixture of broadband and fine transitions. Finally, 3 displays broadband luminescence regardless of temperature. Spin-orbit (SO) CASSCF calculations reveal that the outer-sphere iodide anions influence whether broadband luminescence from 5d → 4f or fine 4f → 4f transitions occur through the alteration of symmetry around the metal centers and the nature of the excited states as a function of temperature.

Synthesis and Reactivity of Cationic Gallium(I) [12]Crown-4 Complexes.

The synthesis and reactivity of a gallium(I) cationic complex using [12]crown-4 as a stabilizing ligand were explored. The synthesis of [Ga([12]crown-4)][GaCl4] was achieved in one step from commercially available starting materials. Anion exchange was utilized to replace the reactive tetrachlorogallate anion for the perfluorophenylborate anion. [Ga([12]crown-4)][B(C6F5)4] was analyzed using XPS, which allowed for the classification of the gallium(I)-crown ether complex as electron-deficient. Reactions of the gallium(I)-crown ether complex with Cp*K and cryptand[2.2.2] demonstrated the facile synthesis of a known gallium(I) compound as well as the generation of new gallium(I) complexes, highlighting the use of the gallium(I)-crown ether complex as an effective starting material for new gallium(I) complexes.

Nonsymmetrical Benzene–Pyridine-Based Nickel Pincer Complexes Featuring Borohydride, Formate, Ethyl, and Nitrosyl Ligands

Nonsymmetrical nickel PCN pincer complexes [Ni(iPrPCNX)Cl] (X = NMe, CH2) are obtained by metalation of the benzene–pyridine-based pincer ligand iPrPCNX (X = NMe, CH2) with [Ni(dme)Cl2] (dme = 1,2-dimethoxyethane). These nickel species afforded the respective borohydride and ethyl complexes [Ni(iPrPCNX)L] (L = BH4, Et) upon treatment with NaBH4 and EtMgBr (or Et2Mg), respectively. Reacting [Ni(iPrPCNX)(κ2-BH4)] with CO2 gave the formate complexes [Ni(iPrPCNX)(OCHO)]. Treatment of [Ni(iPrPCNX)Cl] with the nitrosyl salt NOBF4 led to the formation of the unusual cationic square-pyramidal nickel nitrosyl pincer complexes [Ni(iPrPCNX)(NO)Cl]+ featuring a strongly bent NO ligand (∠Ni–N–O 128.5°). These systems can be described as {NiNO}10 according to the Enemark–Feltham convention. Despite of the bent nature of the NO ligand the νNO is observed at 1849 cm–1 which is more typical for a linear Ni–N–O arrangement. The structure of these complexes is rationalized by means of DFT calculations. The molecular structures of representative complexes are presented.

Cationic Tungsten Imido Alkylidene N-Heterocyclic Carbene Complexes That Contain Bulky Ligands

Neutral and cationic tungsten imido alkylidene complexes of the general formulas W(NtBu)(CHR1)(OR2)Cl(NHC), W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl2(NHC), [W(NtBu)(CHR1)(OR2)(NHC)][B(ArF)4] and [W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl(NHC)][B(ArF)4] (R1 = CMe3, CMe2Ph; R2 = sterically demanding alkoxide; B(ArF)4 = tetrakis(3,5-(CF3)2-C6H3)borate; NHC = N-heterocyclic carbene) were prepared. Two electronically different NHCs, namely 1,3-dimethylimidazol-2-ylidene (IMe) and 1,3-dimethyl-4,5-dichloroimidazol-2-ylidene (IMeCl), as well as a variety of terphenolates and a chiral biphenolate were employed. Z-selective homometathesis (HM) of unfunctionalized olefins was achieved with a selectivity of up to 90% and decent turnover numbers (TON) of up to 480 in the HM of 1-dodecene. Additionally, the reactivity of the cationic tungsten tert-butylimido complexes in the reaction with vinyltrimethylsilane and ethylene was investigated, which yielded the corresponding silyl-alkylidene complex and, for the first time, a fully characterized cationic tungsten(IV) NHC ethylene complex.

Unraveling the role of ion-solvent chemistry in stabilizing small-molecule organic cathode for potassium-ion batteries

Redox-active organic cathodes are promising high-capacity and low-cost electrode materials for potassium-ion batteries (KIBs), but usually suffer from poor cyclability due to the severe dissolution and notorious K dendrites. Herein, the effects of salt concentrations and solvents on the performance of potassium-organic batteries based on a typical phenothiazine derivative, methylene blue (MB), are explored, and the high-concentration potassium bis(fluorosulfonyl)amide-based ether electrolyte is versatile to achieve long lifespan. The high donor number and strong solvation ability of ether solvent endow MB cathode with high voltage plateaus and reversible capacity as compared to the carbonate counterpart. Moreover, the enhanced interactions of K+-ether and anion-participated ion-ether complexes in concentrated electrolyte not only decrease the amount of free solvent, but also contribute to forming highly ionic-conducting and thin anion-derived interphase layers, which effectively mitigate the shuttle effect and inhibit K dendrite growth. Consequently, MB cathode exhibits a high capacity of 139.5 mAh g−1 after 500 cycles at 0.1 A g−1, and long-term cycling stability for 4500 cycles. The good performance of full cells matched with graphite anode further demonstrates the feasibility of MB as KIB cathode. This work highlights the roles of ion-solvent chemistry in stabilizing small-molecule organic cathodes, which may bring new insights in the electrolyte design for wide organic electrode-based battery systems.

Growth, characterization and theoretical studies of cadmium (II) thiourea complexes: a comparative study

Single crystals of bis(thiourea)cadmium(II) chloride, bis(ethylene thiourea)-cadmium(II) chloride, tris(allylthiourea)cadmium(II) chloride and tetrakis-(phenylthiourea)cadmium(II)chloride complexes were grown using conventional slow evaporation solution growth technique. The structure and crystallinity of the materials were confirmed by powder XRD analysis. The optical properties of specimens were analyzed by UV-DRS spectroscopy. FT-IR studies recognize the vibrations of functional groups present. SEM examines surface morphology. TGA and DTA expose the specimen's purity, and the decomposition was not identified until the melting point. Microhardness studies also studied the mechanical behavior of the samples. Kurtz and Perry powder technique estimates the second harmonic generation efficiency of the as-grown specimens. It is interesting to observe that the allylthiourea complex exhibits the maximum SHG efficiency. Ethylene and phenylthiourea complexes are SHG inactive since they crystallize in centrosymmetric space groups. The intermolecular interactions and crystal packing make known that close contacts are related with strong interactions.

Symmetry-Binding Correlations of Crown Ether Complexes with Li+ and Na.

The gas-phase structure of 18-crown-6 in the presence of Li+ and Na+ cations is highly flexible and generally distorted. Using density functional theory calculations, natural bond orbital analysis, and symmetry measures, we reveal the driving forces behind the structural and energy trends of 18-crown-6 and its phenyl substituents. We show that the structural deviation from C3-symmetry increases with the non-bonded interactions between the occupied spx orbitals of the crowns’ oxygen atoms and the unoccupied 2s orbital of the cation. These orbital interactions are strongly correlated with the overall host–guest interaction energy. Our approach highlights the role of non-bonded interactions and paves the way for deeper understanding of structure–reactivity relations of flexible host–guest systems.

Ethene Conversion at a Zeolite‐Supported Ir(I) Complex.A Computational Perspective on a Single‐Site Catalyst System

The Cover Feature illustrates that the product selectivity, ethane vs. butene, depends on the metal center, Ir vs. Rh, of a zeolite-supported complex M(I). In their Full Paper, S. V. C. Vummaleti et al. model an Ir-ethene complex located in a faujasite cavity by applying a quantum mechanics/molecular mechanics scheme involving DFT calculations. While most steps and barriers in the computed reaction network for Ir are rather similar to its Rh congener, the higher crucial C−C coupling barriers, by ∼50 kJ mol−1 relative to Rh, reverse the product selectivity from butene to ethane in the case of Ir. The center Ir(I) adsorbs ethene to form an active complex [Ir(C2H4)3]+/zeo that ultimately is able to activate hydrogen yielding ethane as main product, rationalizing the experiments. Both a Cossee-Arlmann and a metallacycle mechanism were studied with the former one being most active via an in situ generated ethyl complex [Ir(C2H4)(C2H5)2]+/zeo. More information can be found in the Full Paper by S. V. C. Vummaleti et al.

FORMULATION AND EVALUATION OF FAST DISSOLVING TABLETS OF LANSOPRAZOLE BY SOLUBILITY ENHANCEMENT TECHNIQUE

The present study was focused on preparation and evaluation of Lanzoprazole fast dissolving tablets. Lansoprazole (LAN) is a proton pump inhibitor drug and used for the treatment of gastric ulcer. Lansoprazole is acid labile drug and to avoid the acidic pH of the stomach LAN is formulated as oral fast dissolving tablets. Lansoprazole is the class II drug of the BCS classification and has a low aqueous solubility. Hence, to improve the solubility of the drug we have prepared Lansoprazole solid dispersion with poly ethylene glycol and complex with β cyclodextrin. Fast Dissolving tablets of LAN were formulated using different superdisintegrants like Sodium Starch Glycolate, Cross Povidone, Cross Carmellose Sodium by direct compression method. The prepared fast dissolving tablets were evaluated for various parameters like weight variation, hardness, friability, disintegration time, drug content, wetting time, in-vitro drug release and short term stability studies. Percentage weight variation, hardness, friability and drug content uniformity were found to be within the approved range for all the formulations. The in-vitro release studies showed that 99.6% of LAN within 90 sec. Overall, in the formulations prepared by the direct compression method, F3, which contains 6% CCS as super disintegrants release 99% of (LAN) in 2 min was found to be the best formulation. The results concluded that fast dissolving tablets of LAN showing enhanced dissolution might lead to improved bioavailability and effective therapy for gastric ulcer. KEYWORDS: β cyclodextrin, Cross Povidone, Fast dissolving tablets, Gastric ulcer, Lanzoprazole, Solid dispersion

Organometallic single-chain polymer nanoparticles via intra-chain cross-linking with dinuclear μ-halo(diene)Rh(I) complexes

An approach towards the expansion of Rh(I)-containing single-chain polymer nanoparticles (SCNPs) using linear polymers and μ-halo(diene)Rh(I) dimers as cross-linkers in high dilution was explored. Initially, the effects of utilizing different anionic ligands, i.e., halides, together with various labile alkene ligands, such as ethylene, 1,5-cyclooctadiene and 1,5-hexadiene, on the stability and activity of the resulting Rh(I) cross-linking complexes were examined. While the ethylene complexes for bromide and iodide bridges resulted too unstable and the 1,5-cyclooctadiene ligand produced inert complexes, the 1,5-hexadiene ligands provided the proper equilibrium of stability and lability to achieve efficient polymer folding. Thus, a range of new organometallic nanoparticles could be obtained via a direct exchange between the 1,5-hexadiene labile ligands of the Rh(I) complexes, and the corresponding 1,5-hexadiene elements present in ROMP derived 1,5-polycyclooctadiene (PCOD) and 1,4-polybutadiene (PBD). Notably, SEC analysis of the single-chain nanoparticles both for PCOD and PBD revealed the expected decrease in the hydrodynamic radius (Rh) of the parent polymer, indicating that other anions can also be used as elements in the cross-linking moieties to form these organometallic nanoparticles. Moreover, all of the Rh-SCNPs displayed intrinsic semi-conductivities in the range of similar undoped organic conjugated polymers, expanding the possible uses of this methodology for many applications.

Low-Coordinate Iron Chalcogenolates and Their Complexes with Diethyl Ether and Ammonia.

Treatment of Fe{N(SiMe3)2}2 with 2 equiv of the appropriate phenol or thiol affords the dimers {Fe(OC6H2-2,6-But2-4-Me)2}2 (1) and {Fe(OC6H3-2,6-But2)2}2 (2) or the monomeric Fe{SC6H3-2,6-(C6H3-2,6-Pri2)2}2 (3) in moderate to excellent yields. Recrystallization of 1 and 2 from diethyl ether gives the corresponding three-coordinate ether complexes Fe(OC6H3-2,6-But2-4-Me)2(OEt2) (4) and Fe(OC6H3-2,6-But2)2(OEt2) (5). In contrast, no diethyl ether complex is formed by the dithiolate 3. The 1H NMR spectra of 4 and 5 show equilibria between the ether complexes and the base-free dimers. A comparison of these spectra with those of the dimeric 1 and 2 allows an unambiguous assignment of the paramagnetically shifted signals. Treatment of 1 with excess ammonia gives the tetrahedral diammine Fe(OC6H2-2,6-But2-4-Me)2(NH3)2 (6). Ammonia is strongly coordinated in 6, with no apparent loss of ammine ligand either in solution or upon heating under low pressure. In contrast, significantly weaker ammonia coordination is observed when dithiolate 3 is treated with excess ammonia, which gives the diammine Fe{SC6H3-2,6-(2,6-Pri2-C6H3)2}2(NH3)2 (7). Complex 7 readily loses ammonia either in solution or under reduced pressure to give the monoammine complex Fe{SC6H3-2,6-(2,6-Pri2-C6H3)2}2(NH3) (8). The weak binding of ammonia by iron thiolate 7 reflects the likely behavior of the proposed iron-sulfur active site in nitrogenases, where release of ammonia is required to close the catalytic cycle.

η2-Alkene Complexes of [Rh(PONOP-iPr)(L)]+ Cations (L = COD, NBD, Ethene). Intramolecular Alkene-Assisted Hydrogenation and Dihydrogen Complex [Rh(PONOP-iPr)(η-H2)]+

Rhodium-alkene complexes of the pincer ligand κ3-C5H3N-2,6-(OPiPr2)2 (PONOP-iPr) have been prepared and structurally characterized: [Rh(PONOP-iPr)(η2-alkene)][BArF4] [alkene = cyclooctadiene (COD), norbornadiene (NBD), ethene; ArF = 3,5-(CF3)2C6H3]. Only one of these, alkene = COD, undergoes a reaction with H2 (1 bar), to form [Rh(PONOP-iPr)(η2-COE)][BArF4] (COE = cyclooctene), while the others show no significant reactivity. This COE complex does not undergo further hydrogenation. This difference in reactivity between COD and the other alkenes is proposed to be due to intramolecular alkene-assisted reductive elimination in the COD complex, in which the η2-bound diene can engage in bonding with its additional alkene unit. H/D exchange experiments on the ethene complex show that reductive elimination from a reversibly formed alkyl hydride intermediate is likely rate-limiting and with a high barrier. The proposed final product of alkene hydrogenation would be the dihydrogen complex [Rh(PONOP-iPr)(η2-H2)][BArF4], which has been independently synthesized and undergoes exchange with free H2 on the NMR time scale, as well as with D2 to form free HD. When the H2 addition to [Rh(PONOP-iPr)(η2-ethene)][BArF4] is interrogated using pH2 at higher pressure (3 bar), this produces the dihydrogen complex as a transient product, for which enhancements in the 1H NMR signal for the bound H2 ligand, as well as that for free H2, are observed. This is a unique example of the partially negative line-shape effect, with the enhanced signals that are observed for the dihydrogen complex being explained by the exchange processes already noted.

(15‐crown‐5)BiI3 as a Building Block for Halogen Bonded Supramolecular Aggregates

AbstractWe present the synthesis and characterization of (15‐crown‐5)BiI3 (1) and (15‐crown‐5)BiI3 ⋅ 0.5TIE (2), a halogen bonded adduct with tetraiodoethylene (TIE), a typical halogen bond donor. Single crystal structure analysis of 2 suggests a halogen bonding interaction between crown ether complex and TIE. The two compounds’ thermal, optical and vibrational properties are investigated in comparison, with differences pointing towards a notable interaction between the two building blocks in 2. Our results show that crown ether complexes of main group metal halides can be employed as halogen bond acceptors for the synthesis of new supramolecular aggregates.