Synthesis and spectral properties of 4-amino- and 4-acetylamino-N-arylnaphthalimides containing electron-donating groups in the N-aryl substituent

A method for the synthesis of N-aryl-substituted 4-amino- and 4-acetylaminonaphthalimide derivatives with mono- and dialkoxy groups or a 15-crown-5 moiety in the N-aryl substituent is described. The introduction of electron-donating alkoxy groups into the benzene ring of the N-aryl fragment results in fluorescence quenching of the naphthalimide chromophore, which is most pronounced in the spectra of N-acetyl derivatives. The photophysical properties of the synthesized 4-amino- and 4-acetylaminonaphthalimides depend on the solvent polarity and its specific solvating ability due to H-bonding. The crown-containing compounds are promising fluorescent chemosensors for metal cations.     

Polyglucane derivatives with regular substituent distribution

6-O-trialkylsilyl celluloses, 2,3-O-carboxymethylcelluloses, cellulose-3-O-sulfate, and carboxymethylcellulose block copolymers were synthesized by regioselective functionalization of cellulose and of soluble cellulose intermediates like silyl and methoxy-substituted trityl ethers as well as formates and trifluoroacetates. The preparation and structure characterization (NMR, FTIR, HPLC after chain degradation) of those polyglucane derivatives with regular substituent distribution is of importance to design self-assembly systems and supramolecular structures (liquid-crystalline media, ultrathin films, recognition and bioactive materials).     

Syntheses and crystal structures of two new cationic 3,5-dimethylpyrazole derivatives containing organoiron mixed-sandwiches as substituent groups

Organometallic hydrazines formulated as , react with 2,4-pentanedione in acetonitrile to afford 3,5-dimethylpyrazole derivatives , respectively, that contain the organoiron mixed-sandwich moieties. The new complexes have been fully characterized by elemental analysis and IR, UV-vis and ¹H and ¹³C NMR spectroscopies and authenticated by single crystal X-ray diffraction analysis. Complexes crystallize in the space group P2₁/n.     

Thermal oxidative stability of yttrium containing oligomeric silazanes with organoelement substituents and multiceramics on their basis

Russian Chemical Bulletin - Characteristics of thermal transformations of oligomeric silazanes with organoelement substituents at the N atoms (M-OESs) containing one element M = Y, Zr, or Hf or a...     

Chemistry of organosilicon compounds: CIV. Syntheses of novel organoelement heterocycles containing titanium and silicon

Four new dicyclopentadienyltitanium(IV) metallocycles, Cp₂TiCH₂XCH₂ (X = SiMe₂OSiMe₂, SiMe₂CH₂SiMe₂, SiMe₂SiMe₂, and SiMe₂SiMe₂SiMe₂) are prepared and characterized.     

Hypericin derivatives: substituent effects on radical-anion formation

The electron-transfer properties of the hypericin derivatives, dibromo-, hexaacetyl-, hexamethyl- and desmethylhypericin, were studied. Cyclovoltammetric measurements revealed that dibromo- and desmethylhypericin have almost the same redox potentials as the parent hypericin. Substitution of the hydroxyl groups by acetoxy leads to less negative E1/2 values, whereas methoxy substitution induces more negative values. Electron paramagnetic resonance (EPR)/electron nuclear double resonance/general TRIPLE spectroscopy and quantum mechanical calculations were used to establish the structure of the one-electron reduced stages of hypericin derivatives. Proton loss in the bay region, already demonstrated for hypericin, was also found for dibromo- and desmethylhypericin. The spin and charge of the radical ions are predominately confined to the central biphenoquinone moiety of the hypericin skeleton. Generation of the radical ions by in situ electrolysis indicates that the redox potentials of hypericin, dibromo- and desmethylhypericin, containing hydroxyls at the 1, 3, 4, 6, 8 and 13 positions, largely depend on the solvent. With phosphate-buffered saline (pH 7.4)/dimethylsulfoxide (DMSO) as the solvent the EPR spectra of the corresponding radical ions appear at markedly lower potentials than in pure DMSO and N,N'-dimethylformamide. However, this effect is not observable for hexaacetyl- and hexamethyl-hypericin-lacking hydroxyl groups. In all cases the EPR data and calculations revealed the presence of 7,14 tautomers.     

Synthesis of quaternary ammonium salts containing a polyprenyl substituent

Quaternization of triethylamine, 4-dimethylaminopyridine, and N-methylimidazole with moraprenyl bromide gives the corresponding quaternary ammonium salts.     

Synthesis and peripheral substituent effects of bay-annulated indigo derivatives

In this study, indolo-naphthyridine-6,13-diones (5a–d) with four different peripheral substituents were prepared via bay-annulation reactions of indigo. The resulting compounds (5a–d) exhibited fluorescence in the red to near-IR region, while the parent indigo molecule showed no fluorescence. Although the peripheral substituents were oriented to the exterior of the π-conjugated system, the electronic structure affected the absorption and fluorescence spectra. Moreover, calculated molecular orbitals and absorption spectra successfully reproduced the experimental absorption spectra and cyclic voltammograms.     

Formation of charge-transfer complexes in systems containing substituted aromatic hydrocarbons and electron-donating organic compounds

Binary systems of monosubstituted benzene derivatives of type C₆H₅X (X=CN, NO₂, COMe, F, Cl, Br, I) and furan, pyrrole, thiophene, pyridine, tetrahydrofuran, and piperidine are analyzed physicochemically by a refractometric method.From deviations from additivity of n (V) isotherms for systems containing furan plus C₆H₅CN, C₆H₅NO₂, or C₆H₅COMe, conclusions can be drawn about interactions of components leading to formation of charge-transfer complexes (CTC) of 21 composition.With pyrrole possible intermolecular interaction must be confirmed by other methods of physicochemical analysis.Almost all of the systems containing tetrahydrofuran investigated, differ by showing more marked interaction between the components, giving CTC of 11 composition.n (V) isotherms for systems containing pyridine and C₆H₅NO₂ are slightly concave to the composition axis. At the same time piperidine clearly reacts with C₆H₅CN and C₆H₅NO₂, giving a 21 complex with the former, and a colored mixture with the latter, (formation of a complex in this case requires confirmation by other methods).All the thiophene binary systems investigated are characterized by linear refractive index isotherms, i.e., they are refractometrically ideal.The electron-donor properties of the heterocyclic compounds investigated vis a vis the aromatic ring with a lowered-electron density lie in the order tetrahydrofuran > furan > piperidine > pyrrole > thiophene.For Part III see [6].     

Pulse mechanochemistry of organoelement compounds

The results of studies of fast mechanochemical reactions initiated by elastic wave pulses (EWP) of 100 μs duration on polycrystalline mixtures under high pressures (4–25 kbar) are summarized. A possible mechanism of the EWP-initiated processes was proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 9, pp. 1621–1635, September, 1999.     

Charge control of the complex formation of phenol with unsaturated compounds containing organoelement substituents from group IV

The frequency shifts (v (OH)) of phenol and the resonance components (v_r) of these shifts in the IR spectra of forty H-complexes of phenol with furan derivatives containing organic, organosilicon, organogermanium, and organotin substituents are studied. The values of v and v_R are linearly related to quantum chemical parameters of the variation of the effective charges of the furan ring atoms affected by - and -interactions with organic substituents. The effect of the conjugation between an organoelement substituent and the furan ring on the effective charges is estimated. The resonance parameters (_R) of organoelement substituents in derivatives of benzene, thiophene, and furan and the reasons for the non-versatility of _R are considered.For report 7, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 289–295, February, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-18372).     

UV photoelectron spectroscopic study of substituent effects in quinoline derivatives

The molecular and electronic structure of eight substituted quinolines has been investigated by HeI/HeII photoelectron spectroscopy, Green's function calculations, and comparison with the spectra of related compounds. The correlation between nitrogen lone pair ionization energies and basicity in 18 substituted quinolines is discussed. The influence of different substituents has been quantified via the scheme that is based on experimental energy shifts. The relationships between nitrogen ionization energies, pK(a) values, and medicinal activity are also discussed.     

Electronegativity and chemical hardness of organoelement groups

The experimental approaches to estimation of comparative electronegativity and chemical hardness of organometallic groups have been proposed. Qualitative data on the electronegativity of L _nM groups were obtained from ¹⁹F NMR study of model systems 4‐FC₆H₄QML_n (Q = CC, N(R), O, C(O)O, S), (4‐FC₆H₄)₃ SnML _n and (4‐FC₆H₄)₃SnQML _n (Q = O, S), containing a great variety of different organometallic groups containing transition or heavy main‐group metals. The data on chemical hardness of L _nM groups were obtained from NMR study of distribution of different L _nM groups between hard and soft anions. The following basic results have been obtained. (1) The relative electronegativity and chemical hardness of L _nM groups can change in parallel or not with the electronegativity and hardness of the central metal atom. (2) The substituents in Ar can substantially modify electronegativity and hardness of Ar _nM groups; the influence of Ar groups has an inductive nature; the increase in electron‐donating ability of aryl ligands enhances the hardness of Ar _nM cations. (3) The relative electronegativity and hardness of L _nM groups in L _nMX are invariant and do not depend on X.     

Excited-state intramolecular proton transfer reaction modulated by low-frequency vibrations: an effect of an electron-donating substituent on the dually fluorescent bis-benzoxazole

Excited-state intramolecular proton transfer (ESIPT) reaction has been studied in a molecule showing dual fluorescence, the 2,5-bis(2-benzoxazolyl)-4-methoxyphenol (BBMP), and its isotopomers, where the methoxy, and alternatively, the OH group has been deuterated. Attention is focused on the influence of electron donating OCH(3) substituent on fast excited state reaction. Comparison between the resonance-enhanced multiphoton ionization spectrum and the laser-induced excitation of the primary and phototautomeric emissions has been done. The geometry, electron density distribution, vibrational structure as well as the potential energy profiles in the S(0) and S(1) states of four possible rotameric forms of BBMP were calculated with application of the density functional theory (DFT). It allowed identifying the most probable conformer and assessing the role of low-frequency motions for the ESIPT efficiency.     

Influence of substituent effects on the coordination ability of salicylaldehyde Schiff bases

Abstract

The logK₁ was quantified by four parameters, metal ion radii R, metal ion charge Q, metal atom polarizability P, and Hammett constants σ of substituent, where logK₁ was the stability constant of complexes (179) involving 10 Schiff bases Sal-A-X (N-(5-chloro-4-6-dimethyl-benzylidene)-anilines) reacting with 18 metal ions. The effect of substituents on the coordination ability of Sal-A-X was systematically investigated, and an expression with good correlation was obtained. The result shows that the electronic effect of substituent X on the aniline ring has an important influence on the stability of the complex; its electron-donating effect enhances the stability of the complex, whereas its electron-withdrawing effect lowers the stability of the complex. The theoretical results provide a potential value for the design of coordination compounds with unique function and reactivity. Moreover, their coordination selectivity to specific metal-ions can also be evaluated according to Equation (2).