Identical Cation Research Articles

1L-3,4-Bis-O-(diphenylphosphino)-1,2,5,6-tetra-O-methyl-chiro-inositol-κ2P,P′][η4-(Z,Z)-cycloocta-1,5-diene]rhodium(I) tetrafluoridoborate chloroform solvate

The title compound, [Rh(C(8)H(12))(C(34)H(38)O(6)P(2))]BF(4) x CHCl(3), a novel asymmetric hydrogenation catalyst, crystallizes with two independent almost identical cations and anions. Cell-packing interactions are provided by nonclassical hydrogen bonding between phenyl and chloroform H atoms and fluoro and chloro donors of the BF(4)(-) anion and the chloroform solvent molecule.

A remarkable anion effect on the crystal packing of two analogous copper complexes from a thiophene-containing phenol-based ligand

The new asymmetric phenol-based N,O,S-ligand Hpy2th1as was prepared by the straightforward reductive amination of 3-{[bis(pyridin-2-ylmethyl)amino]methyl}-2-hydroxybenzaldehyde with (thiophen-2-yl)methylamine. This potentially hexadentate ligand was used to coordinate to copper(II) chloride. Two dinuclear copper complexes were thus synthesised and fully characterized. Although the two coordination compounds exhibit identical complex cations, the crystal packings of both molecules significantly differ, which is most likely induced by the distinct, but geometrically related anions, namely tetrachlorocuprate(II) and perchlorate.

Transition metal complexes with thiosemicarbazide-based ligands. Part 51. Square-planer nickel(II)complex with acetylacetone bis(S-n-propylisothiosemicarbazone)(L).Crystal and molecular structure of [

The template reaction of a warm methanolic solution of Ni(OAc)2?4H2O S-n-propylisothiosemicarbazide hydroiodide and acetylacetone yielded the needle- like, brown, diamagnetic complex [Ni(L-H)]I?MeOH, and in the presence of an excess of NH 4NCS, brown, prismatic crystals of the complex [Ni(L-H)]NCS (1), both compounds involving the monoanionic form of the ligand, acetylacetone bis(S-n-propylisothiosemicarbazone), L. Slow recrystallization fromMeOH, EtOH, iPrOH and Me2CO gave the corresponding monosolvent complexes [Ni(L-H)]I?solvent, of which only those involving EtOH and iPrOH were suitable for structural analysis. The crystallographic parameters of [Ni(L-H)]I?EtOH (2) and [Ni(L-H)]I?iPrOH (3) are very similar to each other, showing their structures are isomorphic. The crystal structures of the title compounds consist of the independent ions: NCS-, or I-, and the chemically identical cation [Ni(L-H)]+, where L-H is the monoanion resulting from deprotonation of the acetylacetone moiety, a tetradentate N4 ligand forming a square-planar coordination around a Ni(II) ion. It was found that the isothiosemicarbazide fragment of the ligand has an imido form. The complex cations of the compounds [Ni(L-H)]NCS and [Ni(L-H)]I?EtOH exhibit significant difference only in the conformation of their propyl groups.

Anion and Solvent Effects upon the Structures of Platinum(II) Complexes with Thiacrown Ligands: The Crystal Structures of [Pt(9S3)2](PF6)2·2 CH3NO2, [Pt(9S3)2](BF4)2·2 CH3NO2, [Pt(9S3)2](OTf)2·2 CH3NO2, and [Pt(18S6)](BF4)2

AbstractThe synthesis and crystal structures of four mononuclear PtII homoleptic complexes with two thiacrown ligands are presented. The binding mode for both macrocycles to the platinum center contrasts with previous structural reports involving identical complex cations but differing anions or crystallization solvents. All three bis(1,4,7‐trithiacyclononane(9S3))platinum(II) complexes (with tetrafluoroborate, hexafluorophosphate, and triflate as counterions) are centrosymmetric, with endodentate binding of the trithioether resulting in [S4 + S2] coordination. The PtII complex of 1,4,7,10,13,16‐hexathiacyclooctadecane(18S6) shows an elongated square pyramidal structure with one exodentate sulfur in a [S4 + S1] mode. Our work illustrates how changes of counterion and solvent dramatically affect the crystal structures for such complexes, suggesting that packing forces are more important than ligand conformation in determining solid‐state structures. In addition, the full spectroscopic and electrochemical properties of the complex [Pt(18S6)](BF4)2 are reported. The electronic spectrum shows a d−d transition near 430 nm, and an irreversible PtII/PtIII couple occurs at +564 mV vs. Fc/Fc+ in cyclic voltammetry. Both these data are consistent with other hexakis(thioether) PtII complexes. 13C NMR measurements show a non‐fluxional 18S6 ligand in the complex while the platinum‐195 NMR resonance at −4152 ppm indicates a mixed orientation of lone pair electrons on the sulfur donors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Bis(2-amino-6-methylpyridinium) tetrachlorozincate(II)

The title compound, (C6H9N2)2[Zn(II)Cl4], consists of two 2-amino-6-methylpyridinium (AMP) cations and one [ZnCl4]2- anion, which are held together by N-H...Cl hydrogen bonds. Bond lengths within the AMP cation indicate that the imine tautomer makes a significant contribution to the structure. The molecules are associated by two different pi-pi interactions between identical antiparallel AMP cations, with face-to-face distances of 3.627 (4) and 3.342 (3) A, to form a one-dimensional chain.

Synthesis and Photoelectrochemical Properties of Cd4 – xHgxGeS6Solid Solutions

Cd4GeS6 , Hg4GeS6 , and Cd4 – xHg x GeS6 crystals are grown from presynthesized charges. The electrochemical and photoelectrochemical properties of a Cd1.2Hg2.8GeS6 electrode are studied. The energy positions of the conduction-band and valence-band edges are compared for two samples having identical cation compositions but differing in anion composition.

Symmetry aspects of exciton–exciton interactions and biexciton transitions in wurtzite semiconductor structures

AbstractThe inelastic collision of two excitons or the optical decay of a biexciton can induce a transition into an exciton and a photon. From the symmetry point of view, we have studied the states of free and bound biexcitons in bulk GaN with the wurtzite structure and in GaN/AlN heterostructures. Due to the antisymmetry properties arising from the exchange of identical fermions, the ground state of the free Γ biexcitons involving two holes from the same valence band is totally symmetric with respect to the symmetry group of the structure. We established the optical selection rules as well as the possible channels for the processes mentioned above and showed that, whatever is the symmetry of a biexciton, there are at least two channels for its optical recombination. That suggests fast recombination processes. If one (several) phonon(s) is (are) involved in a process, it is always possible to connect by an optical transition any initial state to any final one. An electric field applied parallel to the growth axis lowers the symmetry of superlattices to that of quantum wells. All the results remain valid for any bulk semiconductor with the wurtzite structure and for any wurtzite‐based heterostructure with identical cations or anions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Coordinative flexibility of 1,2-bis[1,4,7-triazacyclonon-1-yl]propan-2-ol in mononuclear and binuclear Ni(II) complexes.

Reaction of 1,2-bis[1,4,7-triazacyclonon-1-yl]propan-2-ol hexabromide (T(2)PrOH.6HBr) with Ni(ClO(4))(2)[middle dot]6H(2)O and adjustment of the pH to 7 resulted in the crystallization of pink and blue products from the one reaction mixture. The analytical data and X-ray structure determinations establish compositions corresponding to [Ni(T(2)PrOH)]Br(ClO(4))xH(2)O (pink crystals) and [Ni(2)(T(2)PrO)(OH(2))(3)Br]Br(ClO(4))x2H(2)O (blue crystals). A repeat synthesis of the latter yielded the diperchlorate monohydrate [Ni(2)(T(2)PrO)(OH(2))(3)Br](ClO(4))(2)xH(2)O. In the mononuclear complex, the 2-propanol group connecting the two 1,4,7-trizacyclononane (tacn) rings is protonated, the six nitrogen donors from the T(2)PrOH ligand coordinating to a single Ni(II) centre in a distorted octahedral geometry. In the binuclear complexes and, three coordination sites on each distorted octahedral Ni(II) centre are occupied fac by three nitrogen donors from the one tacn ring, the two metal centres being linked by an endogenous alkoxo bridge. A notable common feature of the two identical cations is that for one Ni(II) centre the remaining two sites are occupied by two water ligands, while in the other a bromo ligand replaces one ligated water. Similar binuclear systems have been recently defined [Zn(2)(T(2)PrO)X(H(2)O)(2)](ClO(4))(2)(X = Cl, Br), two complexes that exhibit coordination asymmetry with one pseudo-octahedral and one pseudo-square pyramidal Zn(ii) centre. The weak antiferromagnetic coupling in and is discussed and compared to di-phenoxo-bridged Ni(II) examples.

Synthesis of some 3-phenyl chromenone-crown ethers and equilibrium studies on complexation with ion-pair extraction of sodium and potassium dyes

6,7-Dihydroxy-3-phenyl- 2H-chromenones and 7,8-dihydroxy-3-(methoxyphenyl)- 2H-chromenones, o-dihydroxy-3-phenylcoumarins, were prepared from phenylacetic acid/2,4,5-trihydroxybenzaldehyde, methoxyphenylacetic acid/2,3,4-trihydroxybenzaldehyde in NaOAc/Ac 2O, respectively. 3-Aryl-6,7-dihydroxy- 2H-chromenone and 3-aryl-7,8-dihydroxy- 2H-chromenone reacted with the polyethylene glycol ditosylate in CH 3CN/Me 2CO 3 to afford 12-crown-4,15-crown-5, and 18-crown-6-chromenones. The purified products were identified with IR, 1NMR, low and high resolution mass spectroscopy and elemental analysis. Liquid–liquid extractive-spectrophotometric studies of sodium and potassium ion complexes of 3a– c, 4a– h coumarin-crown ethers and anionic dyes [4-(2-pyridylazo)-resorcinol monosodium salt monohydrate (SPAR), and sodium picrate (SP), and potassium picrate (PP)], as the counter ion are described. The overall extraction equilibrium constants for the 1:1 complexes of the above coumarin-crown ethers with sodium and potassium ions, between the organic solvent and water, have been determined at 25 °C. They were conducted in various solvent–water systems maintaining an identical initial cation concentration in water, [M 0 +] w, and a macrocyclic ligand concentration in the organic phase, [L 0] org, so that in all extractions [M 0 +] w:[L 0] org ratios were 1:1. An ion association complex formed between the alkali-crown ether complex ion and a dye anion was extracted into the CH 2Cl 2 organic solvent, and then the dye concentration of the separated aqueous phase was measured with an ultraviolet–visible spectrophotometer. According to the study, SPAR is the best associated dye with all the coumarin-crown ethers and the extracted dye occurs as the ion-pair complex. The extraction selectivity was interpreted quantitatively by the constituent equilibrium constants, i.e. K ext, the ion-pair extraction constant of ML + and A − in CH 2Cl 2.

Vipera lebetina Venom Contains Two Disintegrins Inhibiting Laminin-binding β1 Integrins

To explain the myotoxic effects of snake venoms, we searched for inhibitors of alpha7beta1 integrin, the major laminin-binding integrin in skeletal muscle. We discovered two inhibitors in the venom of Vipera lebetina. One of them, lebein-1 (known as lebein), has already been proposed to be a disintegrin because of its RGD-containing primary sequence. The other, lebein-2, is a novel protein that also interacts firmly with alpha3beta1, alpha6beta1, and alpha7beta1 integrins, but not with the collagen-binding alpha1beta1 and alpha2beta1 integrins. Ligand binding of laminin-recognizing beta1 integrins was efficiently blocked by both lebein-1 and lebein-2. In cell attachment assays, lebein-1 and lebein-2 inhibited myoblast attachment not only to laminin, but also to fibronectin. However, neither lebein-1 nor lebein-2 interacted with alpha7beta1 integrin in an RGD-dependent manner, similar to the interaction of the laminin with alpha7beta1 integrin. Identical divalent cation dependence of integrin binding to laminin and to either of the two inhibitors and their mutually exclusive binding suggest that both lebein-1 and lebein-2 interact with the ligand-binding site of laminin-binding beta1 integrins by mimicking the yet unknown integrin-binding structure of laminins. Like lebein-1, lebein-2 is a soluble heterodimeric disintegrin of low molecular mass. Together with membrane-bound ADAM-2 and ADAM-9, the two inhibitors seem to form a small group of disintegrins that can bind to laminin-binding beta1 integrins. Because of their inhibitory capability both in vitro and in vivo, lebein-1 and lebein-2 may be valuable tools in influencing laminin-induced, integrin-mediated cell functions such as cell anchorage, migration, and mechanical force transduction on laminin-rich basement membranes.

Synthesis and Properties of 1,3,5-Tris(phenoxymethyl)-2,4,6-triethylbenzenes as NH 4 + Ionophores

The synthesis, spectroscopic characterization, and potentiometricmeasurements of new 1,3,5-trisphenoxy-2,4,6-triethylbenzenesare described. The cation binding abilities oftrisphenoxy-2,4,6-triethylbenzenes were strongly dependenton the substituents introduced on the phenoxy units: thereceptors with electron-donating alkoxy groups (–OCH3and –OCH2C6H5) provided similar potentiometricperformance to that of nonactin in PVC-based, ion-selectivemembrane electrodes. The trisphenoxy-2,4,6-triethylbenzenereceptors with ether groups on ortho and meta positions ofphenoxy units exhibit almost identical cation recognitionproperties in the PVC membranes. It is postulated that theelectron-donating nature of the alkoxy substituents increases theelectron density in the phenoxy units, resulting in increasedcation-π interactions.

Site Identification of Mixed Arrays of Keggin-type Heteropolyacids by Scanning Tunneling Microscopy and Tunneling Spectroscopy

Scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) studies on the mixed arrays of Keggin-type heteropolyacids (HPAs) deposited on a highly oriented pyrolytic graphite (HOPG) surface were carried out to test the ability of these techniques to distinguish structurally similar molecules. An equimolar aqueous mixture of HPAs was deposited on a graphite surface for STM measurements. The mixture of Keggin-type HPAs, H3PW12O40 and H3PMo12O40, with identical net anionic charges and identical charge-compensating cations (protons), formed ordered two-dimensional arrays on a graphite surface similar to those formed by their pure components. The periodicities of the arrays were in good agreement with the shape and dimension of the pure Keggin HPAs. It was evident from the STM image of the mixed array that some features appeared brighter than others; the ratio of bright to dim features was almost unity as designed, and their distribution within the ordered array on the surface appeared to be random. TS measurements revealed that the bright corrugations were [PW12O40]3- anions and that the less bright ones were [PMo12O40]3- anions. It is successfully demonstrated that HPAs with indistinguishable geometric structures and sizes can be distinguished based on differences in their electronic properties using STM operated in air.

Exact symmetries of electron Bloch states and optical selection rules in [001] GaAs/AlAs quantum wells and superlattices

We determined the exact symmetries of conduction and valence Bloch states in type-I and type-II [001] $(\mathrm{GaAs}{)}_{m}(\mathrm{AlAs}{)}_{n}$ superlattices at the \ensuremath{\Gamma} point and at some other symmetry points of the Brillouin zone of the superlattices and derived optical selection rules. Contrary to a result widely accepted in the envelope-function approximation (EFA), ${p}_{z}$ atomic orbitals cannot mix with ${p}_{x}$ and ${p}_{y}$ orbitals to build Bloch states. The phonon-assisted transitions involving the \ensuremath{\Gamma} point as an initial or final state are allowed both without and with taking into account the spin-orbit interaction whatever are the symmetries of the initial and final states. The electron band structure of the superlattices is discussed. Within the domain of validity of EFA (i.e., for not too small values of m and n), a detailed analysis of the Bloch-state symmetry and selection rules is provided on imposing invariance of the superlattice structure under the change of z to -z (the ${\ensuremath{\sigma}}_{z}$ symmetry operation). It is shown that optical transitions between the conduction states arising from the \ensuremath{\Gamma} states of GaAs on one hand and the conduction states arising from the X states of AlAs on the other hand can be allowed from spin-orbit coupling only. The correspondence is provided between the symmetry of a Bloch state and the parity with respect to ${\ensuremath{\sigma}}_{z}$ of its associated envelope function. The effect of an electric field parallel to the growth axis is discussed. Quantum wells do not differ from superlattices with regard to Bloch-state and envelope-function symmetries or optical selection rules. All the above results are still valid for any pseudomorphic superlattice or quantum well made of two binary compounds with zinc-blend structure and identical cations or anions, such as, for example, in the GaN/AlN system.

Bound-state symmetries and optical transitions in GaAs/AlAs quantum wells and superlattices with impurities and defects

We consider $(\mathrm{GaAs}{)}_{m}(\mathrm{AlAs}{)}_{n}$ superlattices as single crystals whose structure depends on the growth direction and numbers of monolayers within the slabs of constituent materials. We study point defects such as impurities (substitutional and interstitial) or single vacancies and molecular defects such as paired impurities, double vacancies, or vacancy-impurity complexes in $(\mathrm{GaAs}{)}_{m}(\mathrm{AlAs}{)}_{n}$ superlattices grown along the [001], [110], and [111] directions. The possible site symmetries of the defects as well as the state symmetries for carriers bound to them have been determined. In contrast to bulk GaAs or AlAs, no defect can present ${T}_{d}$ symmetry. The atoms located in the center of the slabs occupy, in most of the [001]- and [110]-grown superlattices, sites with higher symmetries ${(D}_{2d}$ and ${C}_{2v},$ respectively). This results in different selection rules for optical transitions involving the same impurity atom which substitutes the same host atom (Ga, Al, or As) at sites with different symmetries. The effect can be important in optical spectra of superlattices with very thin slabs. The modifications of the selection rules when including the spin-orbit interaction have been derived. Quantum wells can be treated as a particular case of superlattices when barriers become very thick. We present their three-dimensional diperiodic space groups. Quantum wells do not differ from superlattices from the points of view of possible site symmetries and selection rules for optical transitions involving defects. All the above results are also valid for any pseudomorphic superlattice or quantum well made of two binary compounds with zinc-blende structures and identical cations or anions, such as in the GaN/AlN system.

Solvent Effect upon Ion-pair Extraction of Different Sodium Dyes Using Some Crown Ethers

Liquid-liquid extractive-spectrophotometric studies of sodium ion complexes of 18-crown-6(18C6), dibenzo-18-crown-6(DB18C6), 15-crown-5(15C5), and 12-crown-4(12C4) and anionic dyes [4-(2-pyridylazo)-resorcinol monosodium salt monohydrate (PAR), Eriochrom Black T (EBT), and methyl orange (MOR)] and sodium picrate (PICRAT) as the counter ion are described. The overall extraction equilibrium constants for the 1 : 1 complexes of the above crown ethers with sodium dyes between different organic solvents and water have been determined at 25deg;C. They were conducted in various solvent-water systems maintaining an identical initial cation concentration in water, [M0+]w, and macrocyclic ligand concentration in the organic phase, [L0]org}, so that in all extractions [M0+]w : [L0]org ratios were 1 : 1, 1 : 10, 1 : 20, 1 : 50, and 1 : 62.5. An ion association complex formed between the sodium-crown ether complex ion and a dye anion was extracted into the organic solvent, and then the dye concentration of the separated aqueous phase was measured with an ultraviolet-visible spectrophotometer. PAR was the best associated dye with all crown ethers sodium-dyes and the extracted dye occurs as the ion-pair complex. Methylene chloride was found to be better than other extractive solvents used in this study.

{Tris[N-(salicylidene)-2-aminoethyl]amine}tin(IV) Iodide Acetonitrile Solvate

The crystal structure of the title compound, [Sn(C27H27N4O3)]I.0.5CH3CN, involves two almost identical complex cations in the asymmetric unit. These cations contain Sn atoms in a pseudo-octahedral environment with facial coordination of the azomethine N and the phenolate O atoms. The average Sn—O and Sn—N bond lengths are 2.048 (4) and 2.192 (5) A, respectively, while the apical N atom in the ligand is considered to be non-bonded at an average distance of 2.687 (5) A from the Sn atom.

Acid‐catalyzed degradation mechanism of poly(phthalaldehyde): Unzipping reaction of chemical amplification resist

The acid-catalyzed degradation mechanism of chemical amplification resists based on end-capped poly(phthalaldehyde) has been elucidated by semi-empirical molecular orbital calculations. It is concluded that: (i) two different starting points exist in the degradation of end-capped poly(phthalaldehyde), the central part of the polymer as well as the polymer end; (ii) in both cases, after the first protonation, cationic hydroxyl compounds generated decompose to the identical cation intermediate, which can unzip itself to phthalaldehyde monomers successively (unzipping reaction); (iii) the hemiacetal type intermediates hardly degrade to the same intermediate without acid catalyst; (iv) the overall activation energy for the degradation reaction is less than 14 kcal/mol in all the cases. Thus, the poly(phthalaldehyde) resist can easily self-develop below 100°C, as reported in the literature.

Dielectric dispersion of a membrane consisting of a large number of solid bilayers containing mobile ions

The complex permittivity and the impedance of a lamellar membrane consisting of a repetition unit of two conducting dielectrics is calculated using the linearized Nernst–Planck–Maxwell electrodynamics previously developed for isolated interfaces, lamellar films with identical cation and anion mobility inside each type of lamella and with identical Nernst distribution coefficients and for homogeneous polymer films with ionic impurities. Any intrinsic dielectric dispersion of the two (ion-free) dielectrics is neglected and periodic boundary conditions are assumed in a infinite array of identical bilayers. The anion and the cation may be of any charge type and their diffusion coefficients may have any values in the two dielectrics. The Nernst distribution coefficient may be different for the cation and the anion within limits determined by the validity of the linearisation procedure. The calculated complex permittivities of the composite material may differ substantially from the permittivities calculated by a simple Maxwell–Wagner–Sillars (MWS) procedure because of the dynamical electrical double layers formed at 1–2 Debye lengths from the interfaces. These polarisation layers give rise to the so-called excess impedance. The MWS results are, however, always exact in the high-frequency limit. Furthermore, the MWS approach is correct for the dielectric loss at low frequencies. A frequency weighted ‘Cole–Cole plot’ of the real and imaginary components of the excess impedance has a characteristic ‘apple shape’ starting in the origin at very low frequencies and moving clockwise around the origin with increasing frequency. In the high-frequency limit, the origin is always approached in the fourth quadrant along a line with slope-1. The low-frequency asymptote of the frequency weighted Cole–Cole plot for the excess impedance is sensitive to the special conditions, however. The Cole–Cole plots of the total membrane impedance (MWS+excess) exhibit sometimes two partially overlapping semi-circular arcs, one for each type of lamella. When the thickness of the lamellae becomes of the same order of magnitude as the Debye length, the distinction between the two relaxations is wiped out and only a single, flattened arc is seen. A model lamellar ‘cellulose acetate’ (CA) membrane, consisting of alternating layers of ‘wet CA phase’ and ‘aqueous microphase’ with NaCl dissolved, is investigated. The parameters of the membrane are chosen quite realistically (except the one-dimensional geometry) as those pertaining to dense CA membranes, in accordance with previous emf and impedance spectroscopical studies of dense and asymmetric cellulose acetate membranes. The usual electrochemical ‘equivalent circuit’ approach, connecting in parallel the membrane resistance and the membrane capacitance, is put to a test. From the time constant related to the maximum negative reactance the so-called ‘geometric capacitance’ is calculated. From this, the ‘geometric’ membrane permittivity of the membrane is found. At low salt concentrations, the geometric permittivity coincides with the low-frequency limit of the membrane permittivity, but with increasing salt concentrations the geometric permittivity increases less rapidly with concentration than does the low-frequency membrane permittivity. The geometric membrane permittivity seems to be a complicated mean value between the low-frequency membrane permittivity and the high-frequency membrane permittivity (independent of concentration), since the characteristic frequency for the impedance relaxation is many orders of magnitude higher than the characteristic frequency of the dielectric relaxation. The former is related to the diffusional relaxation time of the CA layer, the second to the relaxation time in the aqueous microphase.

Ion-dipole interactions of macrocyclic ethers using13C dipole-dipole relaxation time measurements. Part XI: The complexation of 1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane with Ca2+ in CD3OH

The association constants,K a, of Ca2+ complexes with the nonequivalent binding site macrocycle,1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane, were determined in CD3OH solution using13C dipole-dipole relaxation time,T 1 DD , studies. The measurements ofT 1 DD of the macrocyclic backbone for different stoichiometries (n:m) of complex formation were conducted under extreme narrowing experimental NMR conditions. The general equilibria given with 1/K a[L 0] n+m−1 = (1-nP′) n (1-mP′) m /P′ was used for identical cation and macrocyclic ether-ester concentrations in CD3OH and the association constants found were comparatively small depending on the cyclic ether-ester segments. The logK a values varied from 1.09 to 0.231 for 1 :1 and from 2.43 to 3.61 for 1 : 2 and from 2.29 to 4.24 for 2 : 1 ligand to cation complex stoichiometries.

Fluorescent aggregates of cation-anionic polymethine dyes with simple structures

The absorption, fluorescence, and excitation spectra of two cation-anionic dyes with simple structures, which have the identical anions and variable cations, were studied in weakly polar and nonpolar solvents as well as in binary mixtures of solvents with different polarity. Under these conditions heterogeneous fluorescent aggregates were found at 20 °C. The structure of the cation has a significant influence on the formation and properties of the aggregates of cation-anionic polymethine dyes.