Electronic structure and nonlinear optical properties of model push-pull polyenes with modified indanone groups: a theoretical investigation

Several model polyenes with modified indanone groups were studied by means of density functional theory (DFT) B3LYP/6-31G*, ab initio HF/3-21G* and semiempirical AM1 methods. We investigated the effect of several substituents upon the relationship between the structure, spatial distribution of the highest occupied and the lowest unoccupied pi-MOs, a concept of the global softness and the global hardness as well as both linear and nonlinear polarizabilities for the set of pi-electron chromophores represented by the short-chain model polyene (butadiene) carrying out p-methoxyphenyl group on the one end and several modified indanone groups on the opposite end of the molecule. As probing endocyclic groups used to modify the structure of indanone the following substituents: > CH2; > C=O; > SO2, > C=CH(NO2) and > C=C(CN)2 were selected. The cubic relationship between the polarizability and the global softness was found. The highest polarizabilities (alpha, beta, gamma) are predicted for the derivatives with > C=C(CN)2 group. It was found that the value of beta depends mainly on the difference between dipole moments in the excited and ground states of the molecules. In the case of > SO2 group the results of AMI calculations significantly deviate from relationships found for other derivatives. Experimental IR and Raman spectra of newly synthesized indandione derivative of cinnamaldehyde were compared with computed ones.     

2-azaallylic rearrangement in homogeneous systems

In this work we present mechanism of the base-catalyzed 2-azaallylic rearrangement in homogeneous media. Detailed 2-azaallylic rearrangement studies have shown that tautomerism of derivatives of benzylidenebenzhydrylamines and N-fluorenylidenebenzylamines is not adequately encomposed by the Hammet equation and the equilibrium constant in the case of studied derivatives depends on the electronic as well as steric factors of the azaallylic system substituents. The presence of steric interactions which influence the equilibrium state has been additionally confirmed by means of crystallographic and molecular mechanics data as well as NOE studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and surface properties of new dicephalic saccharide-derived surfactants

A new group of nonionic dicephalic saccharide amides, N-dodecyl-N,N-bis[(3-d-gluconylamido)propyl]-amine, N-dodecyl-N,N-bis[(3-d-glucoheptonylamido)propyl]-amine, and N-alkyl-N,N-bis[(3-lactobionylamido)propyl]amines (alkyl: n-C₁₂H_25′ n-C₁₆H_33′, n-C₁₈H₃₇) were synthesized and characterized. Their structure and purity were confirmed by means of ¹H and ¹³C nuclear magnetic resonance analysis and electrospray ionization mass spectrometry. Carbon spectra were verified using a DEPT experiment. The surface and interfacial properties such as critical micelle concentration (CMC), standard free energy of micellization, ΔG _CMC, surface excess concentration, Γ_CMC, and surface area demand per molecule, A _CMC, were determined. The tertiary nitrogen atom seems to have a surprising effect on surfactnat packing at the interface.     

Characteristics of Superconducting State in Vanadium: the Eliashberg Equations and Semi-analytical Formulas

The superconducting state in vanadium characterizes with the critical temperature (T _c ) equal to 5.3 K. The Coulomb pseudopotential, calculated with the help of the Eliashberg equations, possesses anomalously high value μ ^?(3Ω_max) = 0.259 or μ ^?(10Ω_max) = 0.368 (Ω_max denotes the maximum phonon frequency). Despite the relatively large electron-phonon coupling constant (λ = 0.91), the quantities such as the order parameter (Δ), the specific heat (C), and the thermodynamic critical field (H _c ) determine the values of the dimensionless ratios not deviating much from the predictions of the BCS theory: R _Δ = 2Δ(0)/k _B T _c = 3.68, R _C = ΔC(T _c ) /C ^N (T _c ) = 1.69, and \(R_{H}=T_{c}C^{N}\left (T_{c}\right )\slash {H^{2}_{c}}\left (0\right )=0.171\). This result is associated with the reduction of the strong-coupling and the retardation effects by the high value of the Coulomb pseudopotential. It has been shown that the results of the Eliashberg formalism can be relatively precisely reproduced with the help of the semi-analytical formulas, if the value of μ ^? is determined on the basis of the T _c -Allen-Dynes expression (μ A D? = 0.198). The attention should be paid to the fact that in the numerical and in the semi-analytical approach the comparable values of the thermodynamic parameters for the same μ ^? have been obtained only in the vicinity of the point μ ^? = 0.1.     

New conjugated polyenes with 1,3-dialkyl-2-thiobarbituric acid moiety as materials for nonlinear optics: theoretical calculations, synthesis and spectral properties

In this work we report the results of our study on electronic and spectral properties of conjugated polyenes with electron-accepting 1,3-dialkyl-2-thiobarbituric acid moiety. In model calculations, we examine the effect of the conjugated polyene length on infrared (IR) and Raman spectra of the polyenes by means of ab initio HF/3-21G*. Nonlinear properties were also studied by AM1 method in frames of the sum-over-states (SOS) and finite-field formalism. It was concluded that in well-resolved IR and Raman spectra the frequencies and band intensities can provide valuable information relating to C=C bond lengths in polyene chain and relative polarizabilities. Near-linear correlation between polarizability and integral IR band intensity, corresponding to all C=C stretching modes, and the rather nonlinear relationship of polarizability with integral Raman activity, was found. In our calculation we predict that polarizability and the first hyperpolarizability increases with elongation of polyene chain while the second hyperpolarizability increases smoothly in a quadratic way. In contrast to the linear relationship between polarizability and polyene chain length the dipole moment versus chain length is predicted to be nonlinear. A good agreement was found between experimental and calculated Raman spectra of one newly synthesized compound studied.     

Preparation and properties of new lactose-based surfactants

A new group of nonionic saccharide-based surfactants, N-alkanoyl-N-methyllactitolamines (alkanoyl: decanoyl, lauroyl, myristoyl, palmitoyl, stearoyl), were synthesized and characterized. Surface properties such as critical micelle concentration, standard free energy of adsorption, standard free energy of micellization, surface tension reduction efficiency, effectiveness of surface tension reduction, surface excess concentration, and surface area demand per molecule as well as foaming properties (i.e., foam volume and foam stability), contact angle, antiraicrobial activity, and biodegradability were determined. The selected performance properties were evaluated in relation to commercially available alkyl polyglucosides (Glukopon 600 EC(HH)-a Henkel product), and oligooxyethylenated decyl (C₁₀E₄) and dodecyl (E₁₂E₅) alcohols. The foaming-stabilizing effect and contact angle suggest that the lactose-derived surfactants that were studied share some common properties with alkyl polyglucosides that are different from those with an oligooxyethylene grouping. All tested N-alkanoyl-N-methyllactitolamines were practically nontoxic to bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle test inoculated with activated sludge. N-Alkanoyl-N-methyllactitolamines with lower chain lengths (C₁₀–C₁₄) biodegraded at a slightly faster rate. Biological properties showed that this class of compounds fulfills all requirements needed for environmental acceptance.     

Aldonamide-type gemini surfactants: Synthesis, structural analysis, and biological properties

A new group of nonionics, so-called sugar surfactants having a gemini structure, N,N′-bisalkyl-N,N′-bis[(3-gluconylamido)propyl]ethylenediamines [bis(C _n GA): C _n =n-C₈H₁₇, n-C₁₂H₂₅], N,N′-bisdodecyl-N,N′-bis[(3-glucoheptonylamido)propyl]ethylenediamine [bis(C₁₂GH)], and N,N′-bisalkyl-N,N′-bis[(3-lactobionylamido)propyl]ethylenediamines [bis(C _n LA): C _n =n-C₈H₁₇, n-C₁₂H₂₅], were prepared in a convenient four-step procedure from easily accessible reagents. Their structure and purity were confirmed by means of elemental analysis, electrospray ionization MS (ESI-MS), and NMR spectra—¹H, ¹³C, ¹H−¹³C COSY, and distortionless enhancement by polarization transfer. All tested surfactants were practically nontoxic to gram-negative bacteria and fungi, but they inhibited the growth of some gram-positive bacteria. From the results of the Closed Bottle test (OECD Guideline 301D) for biodegradability measurements, it was concluded that the tested aldonamide gemini structures are biodegraded by environmental microorganisms to 16–55% of the initial levels by day 28, the extent depending on both the aldonamide type and the alkyl chain length. Consequently, N,N′-bisalkyl-N,N′-bis[(3-aldonylamido)propyl]ethylenediamines are a surfactant class having low ecotoxicity and fulfilling requirements desired from an ecological standpoint.