Complexation Of Alkali Metal Cations Research Articles

Ionic Ir(III) complex-interfacial layer for efficient carrier collection via induced electric dipole.

The power conversion efficiency (PCE) of polymer solar cells (PSCs) has recently reached >19% through the development of photoactive materials, particularly non-fullerene acceptors. Interfacial layers (ILs) have been another essential factor in optimizing device charge extraction. In this study, we propose a series of ILs, in which ionic iridium(III) (Ir(III)) complexes of different alkali metal cations (Li+, Na+, and K+) enhance the charge collection efficiency between zinc oxide and active layers through an induced internal electric field. The anionic coordinate sphere and counter-cations of the Ir(III) complexes are distributed according to the operating voltage of the PSCs, causing electric dipoles that enhance the internal electric field and charge collection efficiency. Ion species migration in the ILs is confirmed using electrochemical impedance spectroscopy. The PCE of the PM6:Y6-based PSCs was improved from 14.0% to 15.6% by introducing an IL (Ir-K+). Furthermore, the stability of PSCs containing ionic Ir(III) complexes is enhanced significantly under ultraviolet (UV) light and AM 1.5 G one-sun irradiation owing to the intense UV absorption capacity and photo durability of the ILs. A device containing the Ir(III) complex-based ILs retained ∼60% of its initial PCE after UV irradiation, whereas the control device retained only ∼20%.

Ion Mobility and Fourier Transform Ion Cyclotron Resonance Collision Cross Section Techniques Yield Long-Range and Hard-Sphere Results, Respectively.

We determined collision cross section (CCS) values for singly and doubly charged cucurbit[n]uril (n = 5-7), decamethylcucurbit[5]uril, and cyclohexanocucurbit[5]uril complexes of alkali metal cations (Li+-Cs+). These hosts are relatively rigid. CCS values calculated using the projection approximation (PA) for computationally modeled structures of a given host are nearly identical for +1 and +2 complexes, with weak metal ion dependence, whereas trajectory method (TM) calculations of CCS for the same structures consistently yield values 7-10% larger for the +2 complexes than for the corresponding +1 complexes and little metal ion dependence. Experimentally, we measured relative CCS values in SF6 for pairs of +1 and +2 complexes of the cucurbituril hosts using the cross-sectional areas by Fourier transform ion cyclotron resonance ("CRAFTI") method. At center-of-mass collision energies <∼30 eV, CRAFTI CCS values are sensitive to the relative binding energies in the +1 and +2 complexes, but at collision energies >∼40 eV (sufficient that ion decoherence occurs on essentially every collision) that dependence is not evident. Consistent with the PA calculations, these experiments found that the +2 complex ions have CCS values ranging between 94 and 105% of those of their +1 counterparts (increasing with metal ion size). In contrast, but consistent with the TM CCS calculations, ion mobility measurements of the same complexes at close to thermal energies in much less polarizable N2 find the CCS of +2 complexes to be in all cases 9-12% larger than those of the corresponding +1 complexes, with little metal ion dependence.

The Role of Triazole and Glucose Moieties in Alkali Metal Cation Complexation by Lower-Rim Tertiary-Amide Calix[4]arene Derivatives.

The binding of alkali metal cations with two tertiary-amide lower-rim calix[4]arenes was studied in methanol, N,N-dimethylformamide, and acetonitrile in order to explore the role of triazole and glucose functionalities in the coordination reactions. The standard thermodynamic complexation parameters were determined microcalorimetrically and spectrophotometrically. On the basis of receptor dissolution enthalpies and the literature data, the enthalpies for transfer of reactants and products between the solvents were calculated. The solvent inclusion within a calixarene hydrophobic basket was explored by means of 1H NMR spectroscopy. Classical molecular dynamics of the calixarene ligands and their complexes were carried out as well. The affinity of receptors for cations in methanol and N,N-dimethylformamide was quite similar, irrespective of whether they contained glucose subunits or not. This indicated that sugar moieties did not participate or influence the cation binding. All studied reactions were enthalpically controlled. The peak affinity of receptors for sodium cation was noticed in all complexation media. The complex stabilities were the highest in acetonitrile, followed by methanol and N,N-dimethylformamide. The solubilities of receptors were greatly affected by the presence of sugar subunits. The medium effect on the affinities of calixarene derivatives towards cations was thoroughly discussed regarding the structural properties and solvation abilities of the investigated solvents.

Atomistic Origin of Selective Cs Accumulation in Mushrooms: DFT Analysis for Alkali Metal Cation Complexation Selectivity of Scissors-like Pigments

Atomistic Origin of Selective Cs Accumulation in Mushrooms: DFT Analysis for Alkali Metal Cation Complexation Selectivity of Scissors-like Pigments

Quantum chemical calculation studies toward microscopic understanding of retention mechanism of Cs radioisotopes and other alkali metals in lichens

We evaluate stability of cesium (Cs) and other alkali-metal cation complexes of lichen metabolites in both gas and aqueous phases to discuss why lichens can retain radioactive Cs in the thalli over several years. We focus on oxalic acid, (+)-usnic acid, atranorin, lecanoric acid, and protocetraric acid, which are common metabolite substances in various lichens including, e.g., Flavoparmelia caperata and Parmotrema tinctorum retaining Cs in Fukushima, Japan. By performing quantum chemical calculations, their gas-phase complexation energies and aqueous-solution complexation free energies with alkali-metal cations are computed for their neutral and deprotonated cases. Consequently, all the molecules are found to energetically favor cation complexations and the preference order is Li^+>Na^+>K^+>Rb^+>Cs^+ for all conditions, indicating no specific Cs selectivity but strong binding with all alkali cations. Comparing complexation stabilities among these metabolites, lecanoric and protocetraric acids seen in medullary layer are found to keep higher affinity in their neutral case, while (+)-usnic acid and atranorin in upper cortex exhibit rather strong affinity only in deprotonated cases through forming stable six atoms’ ring containing alkali cation chelated by two oxygens. These results suggest that the medullary layer can catch all alkali cations in a wide pH range around the physiological one, while the upper cortex can effectively block penetration of metal ions when the metal stress grows. Such insights highlight a physiological role of metabolites like blocking of metal-cation migrations into intracellular tissues, and explain long-term retention of alkali cations including Cs in lichens containing enough such metabolites to bind them.

Complexation of Alkali and Alkaline-Earth Metal Cations at Spodumene-Saltwater Interfaces by Molecular Simulation: Impact on Oleate Adsorption

Spodumene, a lithium aluminum inosilicate, is recovered by froth flotation using surfactants, so-called collectors. Therefore, the behavior and properties of the water-mineral interface in saline solutions are central. Here, molecular dynamics simulations are used to study the adsorption of alkali and alkaline-earth metal cations from concentrated solutions on the weakest (110) surface plane of negatively-charged spodumene. Results include the envelope density function of inner-sphere complexes for each cation and the density of complexes according to their adsorption contacts. Visualization of complexes for each cation is also included. Once the structure of the cation layers adsorbed on the surface of spodumene is defined, its role as a catalyst or barrier for adsorption of the spodumene collector in flotation is evaluated. The collector studied is the typical sodium oleate. The results show that oleate adsorption is poor and that the few adsorption contacts are mainly via cation bridges. The findings here indicate that molecular simulation can facilitate the search for effective collectors for environmentally sustainable spodumene flotation processes in saltwater.

Supramolecular Approach for Fine-Tuning of the Bright Luminescence from Zero-Dimensional Antimony(III) Halides.

Halides of ns2 metal ions have recently regained broad research interest as bright narrowband and broadband emitters. Sb(III) is particularly appealing for its oxidative stability (compared to Ge2+ and Sn2+) and low toxicity (compared to Pb2+). Square pyramidal SbX5 anion had thus far been the most common structural motif for realizing high luminescence efficiency, typically when cocrystallized with an organic cation. Luminescent hybrid organic–inorganic halides with octahedral coordination of Sb(III) remain understudied, whereas fully inorganic compounds show very limited structural engineerability. We show that the host–guest complexation of alkali metal cations with crown ethers fosters the formation of zero-dimensional Sb(III) halides and allows for adjusting the coordination number (5 or 6). The obtained compounds exhibit bright photoluminescence with quantum yields of up to 89% originating from self-trapped excitons, with emission energies, Stokes shifts, and luminescence lifetimes finely-adjustable by structural engineering. A combination of environmental stability and strong, intrinsic temperature-dependence of the luminescence lifetimes in the nanosecond-to-microsecond range nominate these compounds as highly potent luminophores for remote thermometry and thermography owing to their sensitivity range of 200–450 K and high specific sensitivities of 0.04 °C–1.

Complexes of Alkali Metal Cations and Molecular Hydrogen: Potential Energy Surfaces and Bound States.

Complexes between metal cations and molecular hydrogen are systems quite amenable for precise spectroscopic and theoretical studies, and at the same time, they are relevant for applications in hydrogen storage and astrochemistry. In this work, we report new intermolecular potential energy surfaces and rovibrational states calculations for complexes involving molecular hydrogen and alkaline metal cations, M+-H2 (M+ = Na+, K+, Rb+, Cs+). The intermolecular potentials, formulated in an internally consistent way to emphasize differences in the properties of the systems, are represented by simple analytical expressions whose parameters have been optimized from comparison with accurate ab initio calculations. Properties of the low-lying bound states-binding energies, frequencies, and rotational constants-are compared with previous measurements or computations and an overall good agreement is achieved, supporting the reliability of the present formulation. Variations of these properties as a function of the cation size and isotopic substitution, with a proper sequence of ortho and para rotational levels, are also discussed.

Neutral glycoconjugated amide-based calix[4]arenes: complexation of alkali metal cations in water.

Cation complexation in water presents a unique challenge in calixarene chemistry, mostly due to the fact that a vast majority of calixarene-based cation receptors is not soluble in water or their solubility has been achieved by introducing functionalities capable of (de)protonation. Such an approach inevitably involves the presence of counterions which compete with target cations for the calixarene binding site, and also rather often requires the use of ion-containing buffer solutions in order to control the pH. Herein we devised a new strategy towards the solution of this problem, based on introducing carbohydrate units at the lower or upper rim of calix[4]arenes which comprise efficient cation binding sites. In this context, we prepared neutral, water-soluble receptors with secondary or tertiary amide coordinating groups, and studied their complexation with alkali metal cations in aqueous and methanol (for the comparison purpose) solutions. Complexation thermodynamics was quantitatively characterized by UV spectrometry and isothermal titration calorimetry, revealing that one of the prepared tertiary amide derivatives is capable of remarkably efficient (log K ≈ 5) and selective binding of sodium cations among alkali metal cations in water. Given the ease of the synthetic procedure used, and thus the variety of accessible analogues, this study can serve as a platform for the development of reagents for diverse purposes in aqueous media.

Solvation Effect on Complexation of Alkali Metal Cations by a Calix[4]arene Ketone Derivative.

The medium effect on the complexation of alkali metal cations with a calix[4]arene ketone derivative (L) was systematically examined in methanol, ethanol, N-methylformamide, N,N-dimethylformamide, dimethyl sulfoxide, and acetonitrile. In all solvents the binding of Na+ cation by L was rather efficient, whereas the complexation of other alkali metal cations was observed only in methanol and acetonitrile. Complexation reactions were enthalpically controlled, while ligand dissolution was endothermic in all cases. A notable influence of the solvent on NaL+ complex stability could be mainly attributed to the differences in complexation entropies. The higher NaL+ stability in comparison to complexes with other alkali metal cations in acetonitrile was predominantly due to a more favorable complexation enthalpy. The 1H NMR investigations revealed a relatively low affinity of the calixarene sodium complex for inclusion of the solvent molecule in the calixarene hydrophobic cavity, with the exception of acetonitrile. Differences in complex stabilities in the explored solvents, apart from N,N-dimethylformamide and acetonitrile, could be mostly explained by taking into account solely the cation and complex solvation. A considerable solvent effect on the complexation equilibria was proven to be due to an interesting interplay between the transfer enthalpies and entropies of the reactants and the complexes formed.

Complexation of Alkali Metal Cations by a Tertiary Amide Calix[4]Arene Derivative in Strongly Cation Solvating Solvents

The complexation of alkali-metal cations with calix[4]arene tertiary amide derivative (L) was studied in N- methylformamide (NMF), N, N- dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) by means of microcalorimetric and UV spectrophotometric titrations. The Gibbs energies, enthalpies, and entropies for transfer of reactants and products from N- methylformamide to other solvents were determined. Favorable enthalpic contribution to overall stability was found to be the most important for all complexation reactions, especially in the case of NaL+ formation, resulting in an affinity peak of L for this cation. The complexation entropy changes were always unfavorable. The ligand dissolution was endothermic in all solvents, accompanied by positive solution entropy. The highest complex stability constants were determined in NMF, whereas in DMSO the affinity of L towards alkali metal cations was the lowest. An interesting interplay between the transfer enthalpies and entropies of the reactants and complexes was revealed and discussed in detail.

A comprehensive study of the complexation of alkali metal cations by lower rim calix[4]arene amide derivatives.

The complexation of alkali metal cations by lower rim N,N-dihexylacetamide (L1) and newly synthesized N-hexyl-N-methylacetamide (L2) calix[4]arene tertiary-amide derivatives was thoroughly studied at 25 °C in acetonitrile (MeCN), benzonitrile (PhCN), and methanol (MeOH) by means of direct and competitive microcalorimetric titrations, and UV and 1H NMR spectroscopies. In addition, by measuring the ligands' solubilities, the solution (transfer) Gibbs energies of the ligands and their alkali metal complexes were obtained. The inclusion of solvent molecules in the free and complexed calixarene hydrophobic cavities was also investigated. Computational (classical molecular dynamics) investigations of the studied systems were also carried out. The obtained results were compared with those previously obtained by studying the complexation ability of an N-hexylacetamidecalix[4]arene secondary-amide derivative (L3). The stability constants of 1 : 1 complexes were determined in all solvents used (the values obtained by different methods being in excellent agreement), as were the corresponding complexation enthalpies and entropies. Almost all of the examined reactions were enthalpically controlled. The most striking exceptions were reactions of Li+ with both ligands in methanol, for which the entropic contribution to the reaction Gibbs energy was substantial due the entropically favourable desolvation of the smallest lithium cation. The thermodynamic stabilities of the complexes were quite solvent dependent (the stability decreased in the solvent order: MeCN > PhCN ≫ MeOH), which could be accounted for by considering the differences in the solvation of the ligand and free and complexed alkali metal cations in the solvents used. Comparison of the stability constants of the ligand L1 and L2 complexes clearly revealed that the higher electron-donating ability of the hexyl with respect to the methyl group is of considerable importance in determining the equilibria of the complexation reactions. Additionally, the quite strong influence of intramolecular hydrogen bond formation in compound L3 (not present in ligands L1 and L2) and that of the inclusion of solvent molecules in the calixarene hydrophobic cone were shown to be of great importance in determining the thermodynamic stability of the calixarene-cation complexes. The experimental results were fully supported by those obtained by MD simulations.

Discriminating Properties of Alkali Metal Ions Towards the Constituents of Proteins and Nucleic Acids. Conclusions from Gas-Phase and Theoretical Studies.

Quantitative insight into the structures and thermodynamics of alkali metal cations interacting with biological molecules can be obtained from studies in the gas phase combined with theoretical work. In this chapter, the fundamentals of the experimental and theoretical techniques are first summarized and results for such work on complexes of alkali metal cations with amino acids, small peptides, and nucleobases are reviewed. Periodic trends in how these interactions vary as the alkali metal cations get heavier are highlighted.

Thermodynamics of alkali metal cation complexation by di-ionized calix[4]arene ligands

Binding of five alkali metal cation (AMC) species by di-ionized calix[4]arene ligands is investigated by isothermal calorimetric titration in methanol at 25.0 °C. Acidic functions attached through the phenolic oxygens to the calixarene scaffold are –OCH2CO2H and –OCH2C(O)NHS2X with X = –Me, –Ph, –C6H4–4–NO2 and –CF3. By use of strongly basicO methoxide media, di-ionized forms of the ligands are employed for titration of the AMCs. By variation of the two remaining lower-rim substituents from –OMe to –OBu, the ring conformation is changed from flexible to cone, partial-cone and 1,3-alternate. Effects of these structural variations on the binding constants for complexation of the AMCs are assessed.

Conformational and vibrational analysis of 18-crown-6–alkali metal cation complexes

Conformational analysis was performed for the 18-crown-6–alkali metal cation complexes, 18c6–AMCCs, using the CONFLEX method. The number of predicted conformations of the 18c6–Li+, Na+, K+, Rb+ and Cs+ complexes was 10, 24, 15, 9 and 4 conformations, respectively. Electronic and geometrical structures were calculated for the predicted conformations at the HF, B3LYP, CAM-B3LYP, M06 and MP2 levels. Binding energies and enthalpies of the ground state conformations were also calculated. Vibrational, IR and Raman, spectra of free 18c6 and 18c6–AMCCs were measured. Comparison between the calculated vibrational frequencies using multi-scale-factor scaling of the B3LYP force field and the experimental vibrational frequencies predicted that the 18c6–K+, Rb+ and Cs+ complexes exist in the D3d, C3v and C3v conformations, respectively. It was also predicted that the 18c6–Na+ complex exists in a D3d-like conformation. It was not possible to identify in what conformation the 18c6–Li+ complex exists.

Thermodynamics of alkali metal cation complexation by ionised calixcrown ligands

Binding of alkali metal cations (AMCs) by 1,3-alternate, ionised calix[4]arene-benzocrown-6 ligands was investigated by isothermal calorimetric titration in methanol. The groups of –C(O)NHSO2CH3 and more acidic –C(O)NHSO2CF3 were attached to the 1,3-alternate calix[4]arene-benzocrown-6 skeleton in two locations. In one series, the acidic group was attached to the para position of one aromatic ring in the calixarene framework, thereby positioning it over the polyether cavity. In the other series, the ionisable group was a substituent on the benzo group in the polyether ring. This oriented the acidic group away from the crown ether cavity. For these calixcrown ligands, the effects of the location of the ionisable group and its acidity and the identity of the AMC on the binding constant, enthalpy and entropy of complexation are assessed.

The “True” Affinities of Metal Cations to p‐Sulfonatocalix[4]arene: A Thermodynamic Study at Neutral pH Reveals a Pitfall Due to Salt Effects in Microcalorimetry

A microcalorimetric study on the inclusion of monovalent and divalent metal cations by p-sulfonatocalix[4]arene was performed. The thermodynamic parameters for the complexation of alkali metal cations and Ag(+) were obtained for the first time at neutral pH. The Na(+) cation is routinely present as counterion of the calixarene in neutral aqueous solution, and this must be taken into account in the determination of the thermodynamic parameters for the complexation of Na(+) and the other cations by considering a sequential or a competitive binding scheme. The ΔH° and ΔS° values show that the inclusion process is entropically driven, although an influence of the temperature on the complexation reaction indicates that the enthalpic term is also an important contributor. The results also reveal that enthalpy/entropy compensation balances the gain in one contribution against a corresponding loss in the other. The obtained thermodynamic data are in contrast to the results from previous microcalorimetric studies, which showed binding constants that were orders of magnitude smaller and complexations, which were in part enthalpically driven but which neglected the influence of the alkali metal counterions.

Cation and Anion Dependence of Stable Geometries and Stabilization Energies of Alkali Metal Cation Complexes with FSA–, FTA–, and TFSA– Anions: Relationship with Physicochemical Properties of Molten Salts

Stable geometries and stabilization energies (Eform) of the alkali metal complexes with bis(fluorosulfonyl)amide, (fluorosulfonyl)(trifluoromethylslufonyl)amide and bis(trifluoromethylsulfonyl)amide (FSA(-), FTA(-) and TFSA(-)) were studied by ab initio molecular orbital calculations. The FSA(-) complexes prefer the bidentate structures in which two oxygen atoms of two SO2 groups have contact with the metal cation. The FTA(-) and TFSA(-) complexes with Li(+) and Na(+) prefer the bidentate structures, while the FTA(-) and TFSA(-) complexes with Cs(+) prefer tridentate structures in which the metal cation has contact with two oxygen atoms of an SO2 group and one oxygen atom of another SO2 group. The two structures are nearly isoenergetic in the FTA(-) and TFSA(-) complexes with K(+) and Rb(+). The magnitude of Eform depends on the alkali metal cation significantly. The Eform calculated for the most stable TFSA(-) complexes with Li(+), Na(+), K(+), Rb(+) and Cs(+) cations at the MP2/6-311G** level are -137.2, -110.5, -101.1, -89.6, and -84.1 kcal/mol, respectively. The viscosity and ionic conductivity of the alkali TFSA molten salts have strong correlation with the magnitude of the attraction. The viscosity increases and the ionic conductivity decreases with the increase of the attraction. The melting points of the alkali TFSA and alkali BETA molten salts also have correlation with the magnitude of the Eform, which strongly suggests that the magnitude of the attraction play important roles in determining the melting points of these molten salts. The anion dependence of the Eform calculated for the complexes is small (less than 2.9 kcal/mol). This shows that the magnitude of the attraction is not the cause of the low melting points of alkali FTA molten salts compared with those of corresponding alkali TFSA molten salts. The electrostatic interactions are the major source of the attraction in the complexes. The electrostatic energies for the most stable TFSA(-) complexes with the five alkali metal cations are -140.3, -119.4, -104.1, -96.9, and -91.1 kcal/mol, respectively. The induction interactions also contribute to the attraction. In particular, the induction interactions are large in the Li(+) complexes. The induction energies for the five complexes are -46.6, -25.2, -17.5, -13.3, and -10.4 kcal/mol, respectively.

The Effect of Specific Solvent–Solute Interactions on Complexation of Alkali-Metal Cations by a Lower-Rim Calix[4]arene Amide Derivative

Complexation of alkali-metal cations with calix[4]arene secondary-amide derivative, 5,11,17,23-tetra(tert-butyl)-25,26,27,28-tetra(N-hexylcarbamoylmethoxy)calix[4]arene (L), in benzonitrile (PhCN) and methanol (MeOH) was studied by means of microcalorimetry, UV and NMR spectroscopies, and in the solid state by X-ray crystallography. The inclusion of solvent molecules (including acetonitrile, MeCN) in the calixarene hydrophobic cavity was also investigated. The classical molecular dynamics (MD) simulations of the systems studied were carried out. By combining the results obtained using the mentioned experimental and computational techniques, an attempt was made to get an as detailed insight into the complexation reactions as possible. The thermodynamic parameters, that is, equilibrium constants, reaction Gibbs energies, enthalpies, and entropies, of the investigated processes were determined and discussed. The stability constants of the 1:1 (metal:ligand) complexes measured by different methods were in very good agreement. Solution Gibbs energies of the ligand and its complexes with Na(+) and K(+) in methanol and acetonitrile were determined. It was established that from the thermodynamic point of view, apart from cation solvation, the most important reason for the huge difference in the stability of these complexes in the two solvents lay in the fact that the transfer of complex species from MeOH to MeCN was quite favorable. That could be at least partly explained by a more exergonic inclusion of the solvent molecule in the complexed calixarene cone in MeCN as compared to MeOH, which was supported by MD simulations. Molecular and crystal structures of the lithium cation complex of L with the benzonitrile molecule bound in the hydrophobic calixarene cavity were determined by single-crystal X-ray diffraction. As far as we are aware, for the first time the alkali-metal cation was found to be coordinated by the solvent nitrile group in a calixarene adduct. According to the results of MD simulations, the probability of such orientation of the benzonitrile molecule included in the ligand cone was by far the largest in the case of LiL(+) complex. Because of the favorable PhCN-Li(+) interaction, L was proven to have the highest affinity toward the lithium ion in benzonitrile, which was not the case in the other solvents examined (in acetonitrile, sodium complex was the most stable, whereas in methanol, complexation of lithium was not even observed). That could serve as a remarkable example showing the importance of specific solvent-solute interactions in determining the equilibrium in solution.

Computational study of ion-pair recognition by heteroditopic calix[4]diquinone derivative

The complexation characteristics of isophthalamide diether calix[4]diquinone macrobicycle (1) with ion-pairs (alkali metal or ammonium cation and halide anion) were investigated by quantum mechanical calculation methods. The total electronic and Gibbs free energies of the various (monotopic, heteroditopic, and contact motifs) complexes of alkali metal and ammonium cations and/or halide anions with 1 were analyzed and compared. The structures of the endo- or exo-complexes of the various cations and anions with the host (1) were optimized using the mPW1PW91/6-31G(d,p) method, followed by DFT B3LYP/6-31G(d,p) calculations. Although the cone conformer is less stable than the partial cone and 1,3-alternate conformers of the free host (1), the cone-type complexes are more stable than the partial cone and 1,3-alternate analogues. The contact-complexation efficiencies of the sodium-halide ion-pair inside the cavity of the lower rim of the cone-type hosts were better (∼20kcal/mol) than those of the potassium ion-pair. These calculated outcomes agree with the experimental results of the anion-binding behavior of 1·M+. The contact-complexation efficiencies of the ion-pairs inside the lower rim pocket of the host 1(cone) were much better (45–50kcal/mol) than those of its heteroditopic-complexation with host 1.The exo-complexation of the cone isomer with the ion-pair could be clearly confirmed by differences in the diagnostic CO bands in the free host and the infrared spectra of its complexes.