- Crystal structures and DFT analysis of Palladium(II) complexes with Schiff bases derived from N,N-dialkyl-p-phenylenediamines
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Herein, new palladium(II) complexes with Schiff bases derived from salicylaldehyde and N,N-dialkyl-p-phenylenediamines were obtained. The ligands 2-((4-(N,N-dimethylamino)aniline)formimidoyl)phenol (N,N-metph-sOH - L1) and 2-((4-(N,N-diethylamino)aniline)formimidoyl)phenol (N,N-etph-sOH - L2) and complexes [Pd(N,N-metph-sO)2] (C1) and [Pd(N,N-etph-sO)2] (C2) were characterized by elemental analysis, infrared (IR) and UV–Vis spectroscopy, 1H and 13C nuclear magnetic resonance (NMR), thermogravimetry (TG) and differential thermal analysis (DTA), and the results agree with the proposed structures. The crystal structures data showed the formation of N,O-chelate with the pairs of phenolate O and imine N occupying the trans positions. Hirshfeld surface analysis was employed to elucidate the intermolecular contacts which drive the different supramolecular assemblies of C1 and C2. In addition, Density Functional Theory (DFT) calculations were also performed to better understand the electronic properties. Additional DFT calculations were also devoted to elucidate the stereochemistry of these palladium complexes toward the cis-trans isomerism among these square-planar Pd(II) N,O-Schiff base complexes. Time-dependent DFT (TD-DFT) analysis was applied to shed light on the nature of the electronic transitions determined in the UV–Vis spectra.
- Sarto, Luís Eduardo,Badaró, Wladimir Pereira Duarte,de Gois, Elba Pereira,Barbosa, Marília Imaculada Fraz?o,Torres, Claudia,Viana, Rommel Bezerra,Honorato, Jo?o,Castellano, Eduardo Ernesto,de Almeida, Eduardo Tonon
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- Understanding difficulties of irregular number-membered ring transition states for intramolecular proton transfer in excited state
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This study presents a variety of organic dyes with similar molecular structures that could undergo intramolecular proton transfer in excited states via five-, six- and seven-number-membered ring transition states, respectively. In addition, the dyes without proton transfer segments are also synthesized to use as references. X-ray single crystal diffraction, NMR spectra as well as UV/visible spectra suggests the presence of internal hydrogen bond with different strength in the target dyes. The steady and transient fluorescence measurements demonstrate occurrence of excited state intramolecular proton transfer via a six number-membered ring transition state. In contrast, it cannot be processed through five- and seven-number-membered ring transition states of the studied dyes. The molecular geometry optimization of the studied dyes reveals fundamental factors for the difficulties of intramolecular proton transfer in excited states via five- and seven-number-membered ring transition states.
- Qin, Xiaozhuan,Ding, Ge,Wang, Zhenqiang,Gong, Yulong,Gao, Fang,Zhang, Shengtao,Luo, Ziping,Li, Hongru
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supporting information
p. 403 - 410
(2017/01/03)
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- Abnormal effect of hydroxyl on the longest wavelength maximum in ultraviolet absorption spectra for bis-aryl Schiff bases
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Two sets of bis-aryl Schiff bases that contain 4(or 4′)-OH and 2(or 2′)-OH were synthesized. The first set consists of 4-HOArCH=NArY and XArCH=NArOH-4′, and the second set consists of 2-HOArCH=NArY and XArCH=NArOH-2′. Their ultraviolet absorption spectra were measured and investigated. A very interesting phenomenon was observed by analyzing their wave number νmax (cm?1) of longest wavelength maximum λmax (nm) of ultraviolet. Compared with the change regularity of the νmax of XArCH=NArY (where the X and Y excluded OH), the 4′-position hydroxyl (4′-OH) and 2′-position hydroxyl (2′-OH) have abnormal performance. The details are the following: the 4′-OH contributes an additional red shift to the νmax of XArCH=NArOH-4′ (λmax increase), whereas the 2′-OH contributes an additional blue shift to the νmax of XArCH=NArOH-2′ (λmax decrease). In addition, there are ortho steric effects of all 2-OH and 2′-OH on the νmax for 2-HOArCH=NArY and XArCH=NArOH-2′, and the ortho steric effect contributes a red shift to their νmax. These experimental facts can provide an important theoretical reference for us using aryl Schiff base compounds as optical materials and performing the molecular design.
- Cao, Chao-Tun,Zhou, Wei,Cao, Chenzhong
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- The substituent effects on the 13C chemical shifts of the azomethine carbon atom of N-(substituted phenyl)salicylaldimines
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Hammett correlations between the 13C-NMR chemical shifts of the azomethine carbon atom and the corresponding substituent constants were established for thirteen Schiff bases. The successful correlation of the chemical shifts with the electrophilic substituent constants σ+ indicate a significant resonance interaction of the substituents on the aniline ring with the azomethine carbon atom in the examined series of imines. The demand for electrons in the investigated compounds was compared to that of the N-benzylideneanilines and N-(substituted phenyl)pyridinealdimines. The manner of transmission of the substituent effects is discussed and they were separated into resonance and inductive effects. The inductive effects prevail over the resonance effects.
- Drmanic, Sasa Z.,Marinkovic, Aleksandar D.,Nikolic, Jasmina B.,Jovanovic, Bratislav Z.
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p. 993 - 1001
(2012/10/29)
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- GREEN SYNTHESIS OF ARYL ALDIMINES USING ETHYL LACTATE
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The present invention relates to a method for preparing aryl aldimines. In particular, the present invention relates to methods of preparing aryl aldimines that uses environmentally friendly solvent systems.
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Page/Page column 5-6
(2011/08/22)
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- A study of the tautomers of N-salicylidene-p-X-aniline compounds in methanol
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We have studied the enol-imine→keto-amine tautomeric equilibrium of N-salicylidene-p-X-aniline compounds with X = Me, OMe, NMe2 as electron donor substituents and X = COMe, CN and NO2 as electron acceptor substituents. The equilibrium constants (Ktauo) and standard thermodynamic properties ΔGtauo, ΔHtauo and ΔStauo were measured and calculated in methanol solution at various temperatures, by means of excitation fluorescence spectroscopy. We have analyzed the p-phenylaniline substitution effect on Ktauo and the thermodynamic properties through the Hammett parameters σ. We have performed molecular orbital calculations at the semiempirical AM1 and ab initio HF/3-21G levels to interpret the experimental results, explicitly including the solute-solvent interaction through the formation of an intermolecular hydrogen bond between the salicylidene and methanol molecules. These computational results show a good correlation with the experimental values. An interpretation of the experimental values of TΔSo, based on changes in the molecular structure produced in the enol-imine→keto-amine tautomeric reaction, is proposed.
- Vargas,Amigo
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p. 1124 - 1129
(2007/10/03)
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- GROUND- AND EXCITED-STATE PROTOTROPIC TAUTOMERISM IN ANILS OF AROMATIC α-HYDROXYALDEHYDES STUDIED BY ELECTRONIC ABSORPTION, FLUORESCENCE AND 1H AND 13C NMR SPECTROSCOPIES AND SEMI-EMPIRICAL CALCULATIONS
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Proton transfer processes in both the ground and excited states in anils of aromatic α-hydroxyaldehydes (salicylaldehyde, 2-hydroxynaphthalene-1-carbaldehyde and the novel 10-hydroxyphenanthrene-9-carbaldehyde) have been studied by a combination of spectroscopic techniques.Solution 1H and 13C NMR is used to establish the position of the tautomeric equilibria.UV-visible absorption and fluorescence spectral data help to characterize the existence, in all cases, of excited-state intramolecular proton transfer (ESIPT) phenomena.Semi-empirical calculations involving full geometry optimization and calculation of heats of formation for the ground state (AM1) and vertical excitation energies and oscillator strengths (INDO/S) are in agreement with the experimental observations.
- Alarcon, Sergio H.,Olivieri, Alejandro C.,Cravero, Raquel M.,Labadie, Guillermo,Gonzalez-Sierra, Manuel
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p. 713 - 720
(2007/10/02)
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