Photochromic crown ethers

An amphiphilic crown-containing styryl dye (1) was synthesized, and the effects of irradiation, temperature, and alkali and alkali-earth metal ions on the conductivity and optical spectra of its solutions in dioctyl phthalate were studied. Compound1 in thetrans-form almost completely exists as ion pairs (IP). Irradiation at a long-wavelength absorption maximum (λ_max) results in a reversible increase in the conductivity and, hence, a degree of dissociation of IP (α); these parameters decrease when complexes with metal ions are formed. The relaxation times for the photoinduced conductivity coincide with a decrease in the extinction within experimental error in the 20–60°C temperature range. The photoinduced increase in α is caused bytrans—cis-isomerization and an increase in steric hindrances for the interaction of the ClO₄ ⁻ anion with the N⁺ atom of benzothiazolium in thecis-form of1. The activation energies for the darkcis—trans-relaxation, absolute α values, and thermodynamic parameters of dissociation of IP in thetrans-form, as well as the α values in a photostationary mixture ofcis—trans-isomers, were estimated. The decrease in α after binding with metal ions is likely caused by the redistribution of the positive charge to benzothiazolium through the conjugated system of1. Correlations between the decrease in conductivity (decrease in α) and the hypsochromic shift Δλ_max after the formation of complexes between1 and metal ions were observed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1301, July, 1997.     

Structure of atoms and fields

In a previous paper the theory of the toroidal spiral field was employed to derive equations for the stationary orbits of particles that belong to both the atomic nucleus and electrons orbiting the nucleus. This theory offered new relativistic relationships for both the mass and electrical charges, leading to the existence inside the nucleus of particles with not only opposite electrical charges in comparison with the electrons, but also with the masses of opposite sign. In this paper, this theory was applied to create a model of the atom that consists of positive and negative muons, positrons and electrons. The two methods that are used to determine the stationary orbits of particles are: (1) quantizing the particle angular momentum, and (2) quantizing the particle relative electrical charge. The existence of particles with the charges 1/3 and 2/3 is explained by the relativistic dependence of the electrical charges on the particle velocity and also by the quantum character of these charges. Creation of the particles and their distribution in the orbits follows the proposed rule of duality and the rule of stability. The theory describes the processes of creation, excitation and annihilation of the positron-electron pairs inside the atoms. In addition, it explains the nature of the self-sustaining movement of particles inside the atom and illustrates the similarity between the propagation of the positron--electron pair inside the atom and the propagation of electromagnetic waves in a free space. It gives a novel interpretation of the physical meaning of Maxwell's displacement current and demonstrates that electromagnetic fields are intimately associated with electrical charges.     

Lithium bromide in acetonitrile: Thermodynamics,theory, and simulation

A variety of methods has been used for the study of lithium bromide solutions in acetonitrile yielding by their combination reliable information on different levels of approximation. Osmotic coefficients based on precise vapor pressure measurements are reproduced by CM (chemical model) and HNC (hypernetted chain) calculations and by BD (brownian dynamics) simulations. The results of neutron scattering experiments are treated with the help of HNC and BD methods. Hartree-Fock calculations on isolated LiBr pairs and solvated lithium ions yield reliable particle distances and reveal the geometry of the lithium solvation sphere.     

Infrared spectra of M+NO 3 − contact ion pairs in aprotic solvents and matrix isolated in the corresponding glasses

Studies of the vibrational spectra of matrix-isolated M⁺NO ₃ ^– ion pairs have been extended to glassy aprotic solvents. The deuterated form of the solvents DMSO, THF, and ACN have windows through the 7- nitrate ionv ₃(e) mode infrared region, so it was possible to clearly observe the splitting of the degeneracy of this mode,v ₃, produced by the contacting, but solvated, alkali metal cation. Primary attention has been directed to the extent to which this splitting is reduced relative to the argon matrix values. This reduction, which reflects electron-density transfer from the solvating molecules to the ion pairs, is comparable to that observed for H₂O and NH₃ matrices as the splitting is reduced to 20–35% of the argon-matrix values. The extent of reduction ofv ₃ for the different solvents has been related to Gutmann's donicity number scale with the correlation holding well for solvent molecules of comparable size, DMSO, THF and DMF, but breaking down for the smaller linear ACN, apparently because of more molecules in the cation solvation sphere. The matrix data have also been used, through comparison with spectra for saturated liquid solutions of Li⁺NO ₃ ^– , to show that the contact ion pair is the dominant species in liquid THF and ACN, whereas the ions are largely solvent separated in DMSO.     

205Tl NMR studies: Ion pairing of Tl+ and (CH3)2Tl+ with NO 3 − and ClO 4 − in various solvents

The concentration dependence of the²⁰⁵Tl chemical shifts of Tl⁺ and of (CH₃)₂Tl⁺ ions was determined in several solvents with NO ₃ ^– and ClO ₄ ^– counterions. In general, increased ion pairing caused a low-frequency shift of the²⁰⁵Tl resonance, with the exceptions of (CH₃)₂TlNO₃ inn-butylamine and TlNO₃ in N,N-dimethylformamide (DMF) and in hexamethylphosphorotriamide (HMPA). In HMPA,²⁰⁵Tl linewidths of both Tl⁺ and (CH₃)₂Tl⁺ increased dramatically with dilution below 0.1M. Analysis of the data allowed ion-pair formation constants and²⁰⁵Tl chemical shifts for the ion-paired cation and for the free (solvated) cation to be estimated for some of the solvents.     

Reactivity of a Frustrated Lewis Pair and Small‐Molecule Activation by an Isolable Arduengo Carbene?B{3,5‐(CF3)2C6H3}3 Complex

Tris[3,5‐bis(trifluoromethyl)phenyl]borane reacts with the sterically demanding Arduengo carbenes 1,3‐di‐tert‐butylimidazolin‐2‐ylidene and 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene to form isolable normal adducts. In the case of 1,3‐di‐tert‐butylimidazolin‐2‐ylidene, the adduct exhibits dynamic behaviour in solution and frustrated‐Lewis‐pair (FLP) reactivity. Fast cleavage of dihydrogen and THF, the C? H activation of phenylacetylene, and carbon dioxide fixation were achieved by using solutions of this adduct in benzene. This adduct is stable at room temperature in the absence of suitable substrates; however, thermal rearrangement into an abnormal carbene–borane adduct can be observed. In contrast, the 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene adduct exhibits no evidence of FLP reactivity or of dissociation in solution. DFT calculations confirmed the experimental behaviour and stability of these carbene–borane adducts.     

Asymmetric Schiff Base (N 2 O 3 ) Complexes as Ligands Towards Mn(II), Fe(III) and Co(II), Synthesis and Characterization

Heterobi- and tri-nuclear complexes [LMM'Cl] and [(LM) 2 M'](M=Ni or Cu and M'=Mn, Fe or Co) have been synthesised. The heteronuclear complexes were prepared by stepwise reactions using two mononuclear Ni(II) and Cu(II) complexes of the general formula [HLM]·1/2H 2 O, as ligands towards the metal ions, Mn(II), Fe(III) and Co(II). The asymmetrical pentadentate (N 2 O 3 ) Schiff-base ligands used were prepared by condensing acetoacetylphenol and ethylenediamine, molar ratio 1 1, to yield a half-unit compound which was further condensed with either salicylaldehyde or naphthaldehyde to yield the ligands H 3 L 1 and H 3 L 2 which possess two dissimilar coordination sites, an inner four-coordinate N 2 O 2 donor set and an outer three-coordinated O 2 O set. 1 H NMR and IR spectra indicate that the Ni(II) and Cu(II) ions are bonded to the inner N 2 O 2 sites of the ligands leaving their outer O 2 O sites vacant for further coordination. Different types of products were obtained according to the type of metal ion. These products differ in stoichiometry according to the type of ligand in the parent compound. Electronic spectra and magnetic moments indicate that the structures of the parent Ni(II) and Cu(II) complexes are square-planar while the geometry around Fe(III), Mn(II) and Co(II) in their products are octahedral as elucidated from IR, UV-visible, ESR, 1 H NMR, mass spectrometry and magnetic moments.     

Complex Salts Derived from the Reactions of Organotin(IV) with 6-Methylpyridine-2-Carboxaldehyde Phenylhydrazone: X-Ray Crystal Structure of BIS[6-Methylpyridine- 2-Carboxaldehydehydrazodium]- Tetrachlorodimethylstannate(IV)

Reactions of organotin(IV) chloride (Me 2 SnCl 2 , PhSnCl 3 and n -BuSnCl 3 ) with the Schiff base 6-methylpyridine-2-carboxaldehyde phenylhydrazone ( L ) result in the formation of organotin(IV) anionic complexes. Me 2 SnCl 2 reacts with L in dichloromethane to form [ L H + ] 2 [Me 2 SnCl 4 ] 2 m . X-ray structural analysis has been carried out on the complex salt bis[6-methylpyridine-2-carboxaldehydehydrazodium]tetra-chlorodimethylstannate(IV), [ L H + ] 2 [Me 2 SnCl 4 ] 2 m wherein the tin moieties exist as monomers. Reactions of PhSnC1 3 and n -BuSnCl 3 with L form the complexes [ L H + ] 2 [PhSnCl 5 ] 2 m and [ L H + ] 2 [ n- BuSnCl 5 ] 2 m . Compounds were also characterized by FTIR, 1 H and 13 C NMR spectroscopy.