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Schiff Base Derivatives (schiff + base_derivative)

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Chemistry100%

Selected Abstracts

Copper Ion Selective Membrane Electrodes Based on Some Schiff Base Derivatives

ELECTROANALYSIS, Issue 15-16 2003
S. Sadeghi
Abstract A series of Schiff base derivatives were studied to characterize their abilities as a copper ion carrier in PVC membrane electrodes. The electrode based on 2,2,-[4,4,diphenyl-methanebis(nitrilomethylidyne)]-bisphenol exhibits a Nernstian response for copper ions over the activity range 8.0×10,6,1.0×10,1 mol L,1 with detection limit of about , mol L,1 of copper ion in comparison with two other Schiff bases. The response time, pH effect and other characteristics of the electrodes were studied in a static mode. The effect of the methyl group substitute on Schiff base structure with SO2 bridging group in different positions with respect to OH group was studied. The results show that behavior of the electrodes is not considerably influenced by the position of methyl substitute. The selectivity coefficients were determined with modified fixed interference method (FIM) and matched potential method (MPM). The proposed electrodes comparatively show good selectivity with respect to alkali, alkaline earth and some transition metal ions. The electrodes were used for the determination of copper in black tea, multivitamin and mineral capsule and as an indicator electrode in potentiometric titration of copper ion. [source]

Photoinduced Excited State Intramolecular Proton Transfer of New Schiff Base Derivatives with Extended Conjugated Chromophores: A Comprehensive Theoretical Survey

CHINESE JOURNAL OF CHEMISTRY, Issue 6 2010
Qi Wang
Abstract This paper presented comprehensive theoretical investigation of excited state intramolecular proton transfer (ESIPT) of four new large Schiff base derivatives with extended conjugated chromophores. The properties of the ground state and the excited state of phototautomers of C1 to C4 [C1: 2-(4,-nitro-stilbene-4-ylimino)methylphenol; C2: 2-(4,-cyano-stilbene-4-ylimino)methylphenol; C3: 2-(4,-methoxyl-stilbene-4-ylimino)methylphenol; C4: 2-(4,- N,N -diethylamino-stilbene-4-ylimino)methylphenol], which included geometrical parameter, energy, rate constant, frontier orbit, Mulliken charge, dipole moment change, were studied by DFT (density functional theory), CIS (configuration interaction singles-excitation), TDDFT (time-dependent DFT) methods to analyze the effects of chromophore part on the occurrence of ESIPT and the role of substituent groups. The structural parameter calculation showed that the shorter RHN and larger ROH from enol to enol* form, and less twisted configuration in the excited state implied that these molecules could undergo ESIPT as excitation. Stable transition states and a low energy barrier were observed for C1 to C4. This suggested that chromophore part increased some difficulty to undergo ESIPT for these molecules, while the possibility of occurrence of ESIPT was quite high. The negative ,E* (,9.808 and ,9.163 kJ/mol) of C1 and C2 and positive ,E* (0.599 and 1.029 kJ/mol) of C3 and C4 indicated that withdrawing substituent groups were favorable for the occurrence of ESIPT. The reaction rate constants of proton transfer of these compounds were calculated in the S0 and S1 states respectively, and the high rate constants of these compounds were observed at S1 state. C1 even reached at 1.45×1015 s,1 in the excited state, which is much closed to 2.05×1015 s,1 of the parent moiety (salicylidene methylamine). Electron-donating and electron-withdrawing substituent groups had different effects on the electron density distribution of frontier orbits and Mulliken charges of the atoms, resulting in different dipole moment changes in enol*,keto* process. These differences in turn suggested that C1 and C2 had more ability to undergo ESIPT than C3 and C4. The ultraviolet/visible absorption spectra, normal fluorescence emission spectra and ESIPT fluorescence emission spectra of these compounds were predicted in theory. [source]

Copper Ion Selective Membrane Electrodes Based on Some Schiff Base Derivatives

ELECTROANALYSIS, Issue 15-16 2003
S. Sadeghi
Abstract A series of Schiff base derivatives were studied to characterize their abilities as a copper ion carrier in PVC membrane electrodes. The electrode based on 2,2,-[4,4,diphenyl-methanebis(nitrilomethylidyne)]-bisphenol exhibits a Nernstian response for copper ions over the activity range 8.0×10,6,1.0×10,1 mol L,1 with detection limit of about , mol L,1 of copper ion in comparison with two other Schiff bases. The response time, pH effect and other characteristics of the electrodes were studied in a static mode. The effect of the methyl group substitute on Schiff base structure with SO2 bridging group in different positions with respect to OH group was studied. The results show that behavior of the electrodes is not considerably influenced by the position of methyl substitute. The selectivity coefficients were determined with modified fixed interference method (FIM) and matched potential method (MPM). The proposed electrodes comparatively show good selectivity with respect to alkali, alkaline earth and some transition metal ions. The electrodes were used for the determination of copper in black tea, multivitamin and mineral capsule and as an indicator electrode in potentiometric titration of copper ion. [source]

Photoinduced Excited State Intramolecular Proton Transfer of New Schiff Base Derivatives with Extended Conjugated Chromophores: A Comprehensive Theoretical Survey

CHINESE JOURNAL OF CHEMISTRY, Issue 6 2010
Qi Wang
Abstract This paper presented comprehensive theoretical investigation of excited state intramolecular proton transfer (ESIPT) of four new large Schiff base derivatives with extended conjugated chromophores. The properties of the ground state and the excited state of phototautomers of C1 to C4 [C1: 2-(4,-nitro-stilbene-4-ylimino)methylphenol; C2: 2-(4,-cyano-stilbene-4-ylimino)methylphenol; C3: 2-(4,-methoxyl-stilbene-4-ylimino)methylphenol; C4: 2-(4,- N,N -diethylamino-stilbene-4-ylimino)methylphenol], which included geometrical parameter, energy, rate constant, frontier orbit, Mulliken charge, dipole moment change, were studied by DFT (density functional theory), CIS (configuration interaction singles-excitation), TDDFT (time-dependent DFT) methods to analyze the effects of chromophore part on the occurrence of ESIPT and the role of substituent groups. The structural parameter calculation showed that the shorter RHN and larger ROH from enol to enol* form, and less twisted configuration in the excited state implied that these molecules could undergo ESIPT as excitation. Stable transition states and a low energy barrier were observed for C1 to C4. This suggested that chromophore part increased some difficulty to undergo ESIPT for these molecules, while the possibility of occurrence of ESIPT was quite high. The negative ,E* (,9.808 and ,9.163 kJ/mol) of C1 and C2 and positive ,E* (0.599 and 1.029 kJ/mol) of C3 and C4 indicated that withdrawing substituent groups were favorable for the occurrence of ESIPT. The reaction rate constants of proton transfer of these compounds were calculated in the S0 and S1 states respectively, and the high rate constants of these compounds were observed at S1 state. C1 even reached at 1.45×1015 s,1 in the excited state, which is much closed to 2.05×1015 s,1 of the parent moiety (salicylidene methylamine). Electron-donating and electron-withdrawing substituent groups had different effects on the electron density distribution of frontier orbits and Mulliken charges of the atoms, resulting in different dipole moment changes in enol*,keto* process. These differences in turn suggested that C1 and C2 had more ability to undergo ESIPT than C3 and C4. The ultraviolet/visible absorption spectra, normal fluorescence emission spectra and ESIPT fluorescence emission spectra of these compounds were predicted in theory. [source]

Synthesis, characterization and catalytic applications of tridentate Schiff base derivatives of bis and mono(cyclopentadienyl)-lanthanocene complexes

CHINESE JOURNAL OF CHEMISTRY, Issue 5 2000
Muhammad Yousaf
Abstract Seven kinds of lanthanocene complexes were prepared by the reaction of tridentate Schiff base | N -(2-methoxyphenyl)salicylideneamine with tris(cyclopentadienyl) lanthanide tetrahydrofuranate or bis (cyclopentadienyl) lanthanide chloride tetrahydrofuranate in THF. All the complexes were characterized by MS, EA and IR respectively. The structure of |Cp2LnC14U13NO2) Ln = Sm, Dy, Y, Er| (1,4) was further confirmed by X-ray determination of Cp2Sm(C14H13NO2) (1) which indicates that the complex is monomeric in which central metal is coordinatively saturated by two cyclopentadienyl rings, two oxygens and one nitrogen of the ligand. The isomerization of 1,5-hexadiene explains that complexes (1,4) isomerize this monomer into a mixture of 1,4-hexadiene, 2,4-hexadiene, 1,3-hexadiene, methylenecyclopentane and methyl,cyclopentene. Similarity complexes |CpLn(a) C14 H13NO2) (THF) (Ln=Sm, Dy, Y, Er)| (5,7) polymerize methyl-methacrylate (MMA) to give polyMMA (PMMA) in 51.8% yield and high molecular weight (274 × 103), which shows narrow molecular weight distributions and partially syndiotactic. [source]