p-tert-Butyldihomooxacalix[4]arene/p-tert-Butylcalix[4]arene: Transition and Heavy Metal Cation Extraction and Transport Studies by Ketone and Ester Derivatives

The binding properties of two phenylketones (2a and 3a) and two ethylesters (2b and {3b) derived from p-tert-butyldihomooxacalix[4]arene or from p-tert-butylcalix[4]arene, in the cone conformation, towards transition (Ag⁺, Ni²⁺, Cu²⁺, Co²⁺, Zn²⁺, Fe²⁺ and Mn²⁺) and heavy (Cd²⁺, Hg²⁺ and Pb²⁺) metal cations have been determined by extraction studies with metal picrates and liquid membrane transport experiments with the same salts. The affinity of these ligands for Ag⁺ has also been investigated by ¹H NMR spectroscopy. Both ketones are better extractants than the esters, and show a strong preference for Ag⁺, while Cu²⁺ is the most extracted cation with the esters. ¹H NMR titrations with AgSO₃CF₃ indicate 1 : 1 complexes for all ligands, those with ketones are more stable, on the NMR time scale, than those with esters. Both esters are good carriers for Ag⁺, and 2b exhibits the highest transport rate (4.7 mol h^-1) found until now with dihomooxacalix[4]arene derivatives.     

Ester and Ketone Groups Substituted Mono- and Di- Azo-coupled Azocalix[4]arenes as Extractant for Hg+ and Hg2+, or Cr3+Cations

This article describes extraction properties of mono- (A1–A8) and di- (B1–B8) substituted azocalix[4]arene analogues. The ionophore solvent extractions of alkaline-earth (Sr²⁺), basic metal (Pb²⁺) and transition metal cations (Ag⁺, Hg⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cr³⁺) from aqueous phase to organic phase were carried out by azocalix[4]arene derivatives. It has been observed that they show a good extraction behavior toward selected heavy metal (Hg) and toxic metal (Cr), while A4 and B4 prefer Hg⁺, Hg²⁺ and Cr³⁺ among transition metal cations, respectively. The azocalix[4]arenes (A1–A8) and (B1–B8) are not efficient extractants for all of the selected metal cations, whereas A4 and B4 are selective only for Hg metal cation.     

Cation Complexation by a Lower Rim Calix(4)arene Derivative: Structural,Electrochemical and Thermodynamic Studies

The synthesis and characterization (¹H and ¹³C NMR) of a partially substituted lower rim p-tert-butylcalix(4)arene, namely, 5,11,17,23-tetra-4-tert-butyl-25,27-bis(diethylphosphate amino)ethoxy-26,28-dihydroxycalix[4]arene (1), are reported. The solution thermodynamics of the ligand in a variety of solvents at 298.15?K was investigated through solubility (hence standard Gibbs energy of solution) measurements while the calorimetric technique was used to derive the standard solution enthalpy. These data were used to calculate the standard entropy of solution. An enthalpy–entropy compensation effect is shown and, as a result, slight variations are observed in the transfer Gibbs energies of this ligand from the reference to other solvents. ¹H NMR, conductance and calorimetric measurements were carried out to establish the degree of interaction of the ligand with univalent (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and Ag⁺) and bivalent (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Hg²⁺, Cu²⁺, Zn²⁺) cations in acetonitrile, methanol, N,N-dimethylformamide and propylene carbonate. No complexation was found between this ligand and univalent cations in these solvents. As far as the bivalent cations are concerned, interaction between 1 and these cations was found only in acetonitrile. The versatile behaviour of this ligand with bivalent cations in this solvent is reflected by the formation of complexes of different stoichiometry. Thus the interaction of 1 with alkaline-earth (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) and Pb²⁺ metal cations leads to the formation of 1:2 (cation:ligand) complexes. However, for other bivalent metal cations (Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺) the complex stoichiometry was found to be 1:1. The results are discussed in terms of the key role played by acetonitrile in processes involving calix[4]arene derivatives.     

Conductance Studies on Complex Formation Between Aza-18-Crown-6 with Ag+, Hg2+ and Pb2+ Cations in DMSO–H2O Binary Solutions

The complexation reactions between Ag⁺, Hg²⁺ and Pb²⁺ metal cations with aza-18-crown-6 (A18C6) were studied in dimethylsulfoxide (DMSO)–water (H₂O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complexes in most cases is 1:1(ML), but in some cases 1:2 (ML₂) complexes are formed in solutions. A non-linear behaviour was observed for the variation of log K _f of the complexes vs. the composition of the binary mixed solvents. Selectivity of A18C6 for Ag⁺, Hg²⁺ and Pb²⁺ cations is sensitive to the solvent composition and in some cases and in certain compositions of the mixed solvent systems, the selectivity order is changed. The values of thermodynamic parameters (ΔH _c^o, ΔS _c^o) for formation of A18C6–Ag⁺, A18C6–Hg²⁺ and A18C6–Pb²⁺ complexes in DMSO–H₂O binary systems were obtained from temperature dependence of stability constants and the results show that the thermodynamics of complexation reactions is affected by the nature and composition of the mixed solvents.     

Crystal Structures of Cs+-Crown Ether Complexes Containing Polynuclear Mercury Iodide Anions

Reactions of CsI and HgI₂ with benzo-15-crown-5 (B15C5) and 15-crown-5 (15C5) in an ethanol-acetone mixture produced [Cs(B15C5)₂]₂[Hg₂I₆] (1) and {[Cs(15C5)]₂[Hg₂I₆]}_n (2), respectively. The structures of the two complexes are quite different. Molar ratios of Cs⁺ : crown ether are 1 : 2 in 1 and 1 : 1 in 2. Complex 1 consists of two Cs(B15C5) ₂ ⁺ cations and a Hg₂I ₆ ^2- anion. Cs⁺ lies between the two crown-5 ligands, resulting in a sandwich-type cation. Cationic Cs(B15C5) ₂ ⁺ and anionic Hg₂I ₆ ^2- are linked together by electrostatic interactions and the complex 1 is an ion pair compound. Complex 2 consists of infinite [Cs(15C5)]₂[Hg₂I₆] units. Each structural unit contains two Cs(15C5)⁺ cations and a Hg₂I ₆ ^2- anion. Cs⁺ is coordinated by five oxygen atoms of 15C5, three iodine atoms of Hg₂I ₆ ^2- , and an iodine atom of Hg₂I ₆ ^2- in an adjacent structural unit. The interactions between the Cs⁺ of Cs(15C5)⁺ and an I^– in Hg₂I ₆ ^2- from adjacent structural units polymerize the complex 2, resulting in a one-dimensional network structure. The anions of Hg₂I ₆ ^2- in both complexes are similar. The two mercury atoms are linked through two bridging iodine atoms and each mercury is also coordinated by two terminal iodines. Crystal data for 1: space group P2₁/c (No. 14), a = 12.253(4), b = 20.945(7), c = 16.110(6) Å, = 111.0(1)°, V = 3860 ų, Z = 4, R = 0.082 (R _w = 0.089). Crystal data for 2: space group P2₁/c (No. 14), a = 12.157(4), b = 8.546(4), c = 20.666(6) Å, = 91.54(3)°, V = 2146 ų, Z = 4, R = 0.034 (R _w = 0.048).     

Synthesis,complexation, and <Emphasis Type="Italic">E—Z</Emphasis> photoisomerization of azadithiacrown-containing styryl dyes as new optical sensors for mercury cations

New styryl dyes containing azadithia-15-crown-5 fragments were synthesized. The complexation of these compounds with Ag⁺, Pb²⁺, Cu²⁺, Hg²⁺, and H⁺ cations was studied by ¹H NMR spectroscopy, steady-state, and time-resolved spectroscopy. The stability constants of the complexes were calculated from the spectrophotometric titration data. The photophysical properties and E—Z photoisomerization of styryl dyes and their complexes with mercury and copper(II) cations in acetonitrile were examined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 495–507, March, 2007. Centre de Physique Moléculaire Optique et Hertzienne-UMR CNRS 5798, Bordeaux University I, 351 Cours de la Libération, 33405 Talence, France.     

X-ray diffraction study of benzothiacrown compounds and their complexes with heavy metal cations

The structures of a series of substituted benzothiacrown compounds containing the dithia-15-crown-5, dithia-18-crown-6, or monothia-15-crown-5 fragment and their complexes with Ag⁺ and Pb2⁺ ions were studied by X-ray diffraction. In free benzothiacrown compounds, the sulfur atoms are preferably located outside the macrocyclic cavity, and their lone electron pairs (LEPs) point away from the center of the macrocycle, which is unfavorable for the formation of inclusion complexes. Flexible macrocyclic fragments can change their conformations in accord with the coordination requirements of heavy metal cations. As a result, benzothiacrown compounds involved in complexes adopt a crown conformation, in which LEPs of all hetero-atoms point toward the cation. The sulfur atoms are involved in coordination of Ag⁺ to a greater degree than the oxygen atoms due to high affinity of soft sulfur atoms for silver cations. On the contrary, the sulfur and oxygen atoms are involved to approximately the same degree in coordination of Pb2⁺ ions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 967–976, May, 2007.     

Unusual coordination features and self-assembly of a crown ether complex [Na2(2,3-naphtho-15-crown-5)2(NO3)][Cu(NO3)3(H2O)]

A novel supramolecular complex, [Na₂(2,3-naphtho-15-crown-5)₂(NO₃)][Cu(NO₃)₃(H₂O)] (1), has been prepared and characterized by X-ray single crystal diffraction. The complex crystallizes in the triclinic system, space group Pī, with a?=?11.233(6), b?=?13.342(7), c?=?16.601(8)?Å, α?=?89.836(7), β?=?79.132(8), γ?=?66.545(7)°, V?=?2234(2)?ų, Z?=?2 and final R ₁(wR ₂)?=?0.0467(0.1164). Novel coordination features and supramolecular architectures are found in the solid state of 1. Two [Na(2,3-naphtho-15-crown-5)]⁺ cations containing two different sodium coordination numbers (six and seven) are bridged by a tridentate nitrate group, to form a larger complex cation, [Na₂(2,3-naphtho-15-crown-5)₂(NO₃)], which is assembled into a novel 1D zigzag chain-like structure through aromatic C–H?···?π interactions.     

Synthesis and applications of (5-substituted benzimidazolo)-benzo-15-crown-5 and 4,4′-bis-benzimidazolo-dibenzo-15-crown-5 for the colorimetric detection of Au3+

In the present work, we have reported the synthesis of benzimidazoles functionalized crown ether derivatives of 4-formyl benzo-15-crown-5/4,4′-diformyl dibenzo-15-crown-5 and substituted diamine pyridine using sulfamic acid as a catalyst in DMSO. These molecules are used for the colorimetric determination of Au³⁺ selectively among other metal cations such as Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, Au³⁺ and Ag⁺ ions_.     

Recoordination of a metal ion in the cavity of a crown compound: a theoretical study

The absorption spectra of styrylbenzothiazolium dye derivatives were calculated by the time-dependent density functional (TD DFT) method. The dyes of interest were (p-dimethylamino)styrylbenzothiazolium dye and its protonated form as well as aza-15(18)-crown-5(6)-containing dyes and their complexes with alkali (K⁺ and Na⁺) and alkaline-earth (Ca²⁺, Sr²⁺, and Ba²⁺) cations. Several low-lying conformers of the azacrown-containing dyes were considered. The electronic and geometric structures of the excited states responsible for the appearance of the long-wave (π-π*) absorption bands are studied. Complexation causes a hypsochromic shift of the long-wave absorption band correlating with the pyramidality of the crown ether nitrogen in the complex. The interaction of the cation with 3–4 solvent molecules or a counterion (ClO₄ ^?) considerably reduces this shift, especially in the conformers without the metal-nitrogen bond. In some cases, the long-wave absorption band is close to the absorption band of the free dye. Similar results were obtained using the polarizable continuum model of solvation. Excited-state structures of the free model dye and the free azacrown-containing dyes exhibit a tendency to bond alternation. Conversely, the cationic complexes of the crown-containing dyes and the protonated model dye exhibit a tendency to bond equalization in the excited state. The changes in the excited-state geometries of the free dyes and their complexes account for the complexation-induced fluorescence enhancement observed in the experiments.     

A Thermodynamic Study of Complex Formation Between 18-Crown-6 with T1 + , Hg 2+ and Ag + Metal Cations in Some Binary Mixed Non-aqueous Solvents Using the Conductometric Method

The complexation reactions betweenT1⁺, Hg²⁺ andAg⁺ metal cations with 18-Crown-6 (18C6)were studied in acetonitrile (AN)-methanol (MeOH) andbenzonitrile (BN)-methanol (MeOH) binary mixtures at differenttemperatures using the conductometric method. The conductance datashow that the stoichiometry of the complexes in most cases is1 : 1 (ML), but in the case of theTl⁺ cation, in addition to a1 : 1 complex, a 1 : 2 (ML₂)complex is formed in solutions. A non-linear behaviourwas observed for the variation of log K_fof the complexes vs the composition of the binary mixed solvents. The stability of 18C6 complexes with T1⁺, Hg²⁺ and Ag⁺ cations is sensitive to solvent composition and in some cases, the stability order is changed with changingthe composition of the mixed solvents. The values of the thermodynamic parameters (Δ H_c°, Δ S_c°) for formation of 18C6-T1⁺, 18C6-Hg⁺² and the 18C6-Ag⁺ complexes were obtained from the temperature dependence of the stability constants and the results show that the thermodynamics of the complexationreactions is affected by the nature and composition of the mixed solvents and in most cases, the complexes are enthalpy destabilized but entropy stabilized.     

NMR-Spektroskopische Untersuchungen der kinetischen Limitierung der Kationenselektivität eines cadmiumselektiven Ionophors

NMR Studies of the Kinetic Limitation of Cation Selectivity of a Cadmium-Selective Ionophore The Cd²⁺-selective ionophore N,N,N′,N′-tetrabutyl-3, 6-dioxaoctanedithioamide (1) looses its capability to induce cation selectivity in solvent polymeric membranes if these are contacted with Cu²⁺, Pd²⁺, Pt²⁺, Ag⁺ and Hg²⁺. For systems with a free energy of activation of the ligand exchange reaction of more than about 65 kJ mol^?1 (in acetonitrile) the cation complexes of the ionophore act as anion exchangers (Pt²⁺, Pd²⁺). Below about 45 kJ mol^?1 cation permselectivity is observed (Zn²⁺, Cd²⁺). Ag⁺ and Hg²⁺ induce a decomposition of the ionophore.     

A Study of Formation Equilibria of the Complexes of Some Metal Cations with Polyoxa Macrocyclic Ligands

Abstract

The complexes formed by the Na⁺, K⁺, Rb⁺, Ca²⁺, UO²⁺ ₂, and Ag⁺ cations with the macrocyclic polyethers 18-crown-6, benzo-15-crown-5, and dicyclohexy1-18-crown-6 are investigated. The stability constants of these complexes have been determined potentiometrically in (90% vol.) ethanol-water solutions at 25[ddot]C and an ionic strength μ= 0.1 (achieved with tetrabuty lammonium perchlorate). The stablity of the investigated complexes was interpreted in terms of “caging” the metal cation into the cavity of the macrocyclic ligand, an effect which depends on the ratio of the diameter of the complexed cation over the diameter of the cavity of the complexing ligand.     

Experimental and computational studies of the binding properties of lower rim tetra- and di-substituted calix[4]arene amide derivatives with metal ions

Abstract

Experimental and theoretical binding studies of representative alkali, alkaline earth, transition, heavy metal and lanthanide cations by tetra- and di-substituted calix[4]arene amide derivatives (diethyl amide 1a–c and morpholide amide 2a–c) in the cone conformation were carried out. Binding was assessed by extraction experiments of the metal picrates from water to dichloromethane and proton NMR titrations. Density functional theory calculations were also performed to determine the binding energy of the complexes formed and to analyse the host–guest interaction modes. In the cases of ligands 1b and 2c with Na⁺ and Ag⁺ picrates, the extraction energy was also determined using the polarisable continuum model. The results are discussed in terms of the nature of the amide residue and the substitution pattern (1,3 vs. 1,2). Both tetra-amide derivatives are good extractants, showing preference for Na⁺, Ca²⁺, Ag⁺ and Pb²⁺ cations, mainly di-ethylamide 1a. Concerning di-amide derivatives, the relative position of the substituents seems to be more important than the nature of the amide group in the extraction process. Proton NMR studies indicate the formation of 1:1 complexes between the amides and the cations studied, and DFT data show that all ligands form the most stable complexes with La³⁺.     

A Simple Colorimetric Sensor with High Selectivity for Mercury Cation in Aqueous Solution

Abstract

A simple and sensitive mercapto thiadiazole Schiff-base colorimetric chemosensor 2 was synthesized. It exhibits good selectivity and sensitivity for the mercury cation over other metal cations such as Zn²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Ag⁺, Ca²⁺, Mg²⁺, and Cr³⁺ in both aqueous solution and on paper-made test kits. The change in color is very easily observed by the naked eye for the presence of Hg²⁺ cation, whereas other metal cations do not induce such a change. The chemosensor 2 showed remarkably anti-interference ability toward other metal cations and the detection limit toward Hg²⁺ was 1.5 × 10^?5 M.

GRAPHICAL ABSTRACT      

Crystal Structure of (2.2.2-Cryptand)lithium Perchlorate

(2.2.2-Cryptand)lithium perchlorate [Li(2.2.2-Crypt)]⁺ClO^– ₄ (I) is prepared and characterized by X-ray structural analysis. Structure I (space group P2₁2₁2, a = 10.149 Å, b = 13.475 Å, c = 8.580 Å, Z = 2) is solved by the direct method and refined anisotropically by the full-matrix least-squares method to R = 0.056 for 2312 reflections (CAD4 automated diffractometer, MoK ). Crystal of complex I is built of [Li(2.2.2-Crypt)]⁺ complex cations of the host–guest type and randomly disordered ClO^– ₄ anions. Both ions are located on the twofold crystallographic axes. The Li⁺ cation, which is also randomly disordered about the 2 axis, is coordinated by the N atom and five O atoms from eight heteroatoms (2N + 6O) of the cryptand. Two Li–O and one Li–N bonds are noticeably elongated. The Li⁺ cation forms irregular six-vertex coordination polyhedron.     

Thermodynamic behavior of complexation process between dibenzo-18-crown-6 and K+, Ag+, NH 4 + , and Hg2+ cations in ethylacetate-dimethylformamide binary media

The complexation reactions between K⁺, Ag⁺, NH₄⁺, and Hg²⁺ cations and the macrocyclic ligand, dibenzo-18-crown-6 (DB18C6), were studied in ethylacetate (EtOAc)-dimethylformamide (DMF) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stochiometry of all the complexes is 1:1. A non-linear behavior was observed for the variation of log K _f of the complexes versus the composition of binary mixed solvents, which was discussed in terms of heteroselective solvation and solvent-solvent interactions in binary solutions. It was found that the stability order of the complexes changes with changing the composition of the mixed solvents. The sequence of stabilities for the K⁺, Ag⁺, NH₄⁺, and Hg²⁺ complexes with DB18C6 in EtOAc-DMF binary solutions (mol. % DMF 25.0) and (mol. % DMF 50.0) at 25°C is (DB18C6-Ag)⁺ > (DB18C6-K)⁺ > (DB18C6-Hg)²⁺ > (DB18C6-NH₄)⁺, but in the cases of pure DMF and a binary solution of EtOAc-DMF (mol. % DMF 75.0) is (DB18C6-K)⁺ > (DB18C6-Hg)²⁺ > (DB18C6-Ag)⁺ ≈ (DB18C6-NH₄)⁺. The values of thermodynamic quantities (ΔH _c ^o, ΔS _c ^o) for these complexation reactions have been determined from the temperature dependence of the stability constants, and the results show that the thermodynamics of the complexation reactions is affected by the nature and composition of the mixed solvents and, in all cases, positive values of ΔS _c ^o characterize the formation of these complexes. In addition, the experimental results show that the values of entropies for the complexation reactions between K⁺, Ag⁺, NH₄⁺, and Hg²⁺ cations and DB18C6 in EtOAc-DMF binary solutions do not change monotonically with the solvent composition. The text was submitted by the authors in English.     

Polarographic and voltammetric investigations in N-methylpyrrolidinone(2) and N-methylthiopyrrolidinone(2)

Polarographic and voltammetric methods were employed to study the influence of N-methylpyrrolidinone(2) (NMP) and N-methylthiopyrrolidinone(2) (NMTP) towards a series of cations. In NMP reversible electrode reactions were observed for Na⁺, K⁺, Tl⁺, Zn²⁺, Cd²⁺, Cu²⁺, Ag⁺ and irreversible reductions for Ba²⁺, Mn²⁺, Co²⁺ and Ni²⁺. 0.1 mol l^?1 tetraethylammoniumperchlorate solutions served as supporting electrolytes. Li⁺ was not electroactive in the supporting electrolyte mentioned, but yielded an irreversible cathodic wave in tetra-n-butylammonium perchlorate. In NMTP, Li⁺, Na⁺, Tl⁺, Zn²⁺, Cd²⁺, Cu⁺ and Ag⁺ gave reversible cathodic waves on the DME, while Mn²⁺, Co²⁺ and Ni²⁺ were reduced in an irreversible electrode process. Bisbiphenylchromium iodide serving as a reference system throughout this study showed reversible behaviour in both solvents. A comparison of E_1/2 for given ions in both solvents showed a shift of about 0.5 V to more positive values in the case of a typically hard cation such as Na⁺ whereas soft cations such as Ag⁺ and Cu⁺ shifted by more than 0.8 V to more negative values. The effects of these two solvents on the cations studied is discussed in terms of donor acceptor interactions between the cation and the solvent molecules with special respect to the changes caused by replacing the oxygen atom in NMP by a sulphur atom.     

Synthesis and Characterization of the Cobalt Complexes of New BF2 + Bridged,Anthracene Substituted Bis(a-Dioxime) Macrocycles

Abstract

The synthesis, characterization and structure are described for new cobalt complexes, with a BF₂ ⁺ bridged, bis(a-dioxime) ligand, based upon a sterically demanding framework derived from an anthracene Diels-Alder adduct. The ligand provides a deep cleft within which axial ligands and/or O₂ can bind. The crystal structures of the bis- and mono(BF₂ ⁺) bridged complexes have space groups P2₁/c and P I, respectively, with unit cell dimensions a = 12.662(2) Å, b = 16.430(3) Å, c = 10.438(3) Å, β = 103.51(2)°, a = 12.046(1)Å, b = I7.596(3)Å, c = 9.939(I)Å, a = 105.15(1)°, β = 102.87(1)°, and γ = 78.13(1), respectively. For both complexes Z = 2 and the residuals R and R _w were 0.070, 0.104, and 0.059, 0.075, respectively. ESR studies show that the cobalt(II) complexes have a strong tendency to bind two axial nitrogen bases, adopting a coordination number of six. The dioxygen affinity of the new cobalt(II) dioxygen carrier is limited by the competition between axial base binding and O₂ binding. This extends the understanding of correlations between electrode potentials and O₂ affinities and possible sources of apparent contradictions.     

15-Hydroxybenzomonothia-15-crown-5 with the sulfur atom linked with the benzene ring and the derived sulfoxide: synthesis,structure, and complexation with the metal cations

Novel 15-hydroxybenzomonothia-15-crown-5 containing the sulfur atom linked with the benzene ring and its S-oxide were synthesized. The stability constants for the complexes of the obtained benzocrown ethers and a reference 15-hydroxybenzo-15-crown-5 with Na, Ca, Ag^I, Cd, Hg^II, and Pb^II perchlorates were determined by ¹H NMR titration. In MeCN-d₃, the benzothiacrown ether demonstrates a high selectivity towards the thio- and oxothiophilic Hg²⁺ (logK ₁ = 7.1) and Pb²⁺ ions (logK ₁ = 7.4). In MeCN-d₃-D₂O mixtures, the stabilities of the most of complexes decrease sharply due to competitive hydration of the metal cations except for the “soft” Ag⁺ and Hg²⁺ ions having low affinity for the “hard” oxygen atoms and, on the contrary, very high affinity for the “soft” S^II atoms. This results in the change in selectivity of complexation: at the water content in solution of 20%, the benzothiacrown ether binds preferably the Hg²⁺ (logK ₁ = 5.0) and Ag⁺ ions (logK ₁ = 2.7). In MeCN-d₃, the benzothiacrown-derived sulfoxide is a weak and non-selective complexing agent towards all the metal cations under study; the reference 15-hydroxybenzo-15-crown-5 forms more stable complexes with the oxophilic sodium, calcium, and lead(ii) cations. The conformational features of the benzocrown ethers and their metal complexes established by NMR spectroscopy and X-ray diffraction are discussed. The found characteristics of the complexing ability of benzomonothia-15-crown-5 where the sulfur atom is in conjugation with the benzene ring reveal that the macrocyclic ligands with such a structure are promising as high-selective and efficient complexing agents for the “soft” mercury(ii) and silver(i) cations in acetonitrile-water mixtures.