Tautomerism in Chlorinated O-Hydroxyschiff Bases: Effect of Chlorine Atom Substitution

Salman, Salman R.; Shawkat, Sawsan H.; Al-Obaidi, G. M.

doi:10.1080/00387018908054023

Cited by 26 publications

(14 citation statements)

References 14 publications

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“…H-N forms) to be present in featuring salicyclic Schiff base derivatives depending on the formation intramolecular hydrogen bonding by UV-Vis spectra. In solution, the tautomerism depends on solvent polarity [12,13,20,[21][22][23][24][25]. For instance, in polar solvents, a new band at >400 nm arises, whereas this can not be observed in nonpolar solvents.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Spectroscopic Characterization of New Schiff Bases Containing the Benzo-15-Crown-5 Moiety

Hayvalı

Dal

2004

Molecules

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Section: Methodsmentioning

confidence: 99%

Synthesis and Spectroscopic Characterization of New Schiff Bases Containing the Benzo-15-Crown-5 Moiety

Hayvalı

Dal

2004

Molecules

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“…First, it has large solvent effects in liquids in terms of equilibrium and solvatochromic shifts of the keto tautomer (Dudek and Dudek, 1966;Salman et al, 1994). Tautomerization of the Schiff base and its ability to hydrogen bond, as well as the effect of solvents on these phenomena, has been the focus of much study and debate (Dudek and Dudek, 1971;Herscovitch et al, 1973;Issaf et al, 1974;Ledbetter, 1977;Lewis and Sandorfy, 1982;Mills and Beak, 1985;Ranganathan et al, 1986;Nagy and Herzfeld, 1987;Salman et al, 1989). Schiff bases are also an important group of chemicals with applications in areas ranging from luminescent dyes for solar collectors (Sharma et al, 1990) to medicinal compounds (Ledbetter, 1977).…”

Section: Focus Of This Studymentioning

confidence: 98%

Cosolvent tuning of tautomeric equilibrium in supercritical fluids

et al. 1997

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“…In the solid state, the ketoamine form has been found for naphthaldimine, while in salicylaldimine ligands the phenol-imine form is present [30,31]. In solution, the tautomerism depends on solvent polarity [26,27]. For instance, in polar solvents, a new band at > 400 nm arises that is not observed in non-polar solvents.…”

Section: Uv-vis Spectramentioning

confidence: 98%

Synthesis and characterization of new bis(crown ether)s of Schiff base type containing recognition sites for sodium and nickel guest cations

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et al. 1999

J. prakt. Chem.

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The study of bis(crown ether)s has attracted great interest in the last two decades, not only from the synthetic and selective alkali and alkaline earth cation complexation properties point of view, but also with respect to their unusual structural characteristics [1,2]. For the linkage of two crown ether units by means of aliphatic or aromatic chains, ester [3,4,5], amide [6,7] and Schiff base type [8,9] precursors are commonly used. It is a well-known fact that monocyclic crown and also bis-(crown ether)s yield complexes with alkali [10,11] and alkaline earth metal ions [11,12]. If the diameter of the metal ion is larger than the hole size of the crown ether ring, sandwich type complexes (clams) are formed, giving rise to a stabilizing "bis(crown ether) effect" [12,13,14] in case of the intramolecular bis(crown) sandwich complexes. And, derived from this, bis(crown ether)s are more selective than the corresponding crown ether components (coronands) with reference to particular cations, e.g. K + against Na + [8]. In addition to the homonuclear mono-and ditopic complexes of bis(crown ether)s with alkali and alkaline earth metal ions, heteroatoms of the linkage unit between the two crown ether rings can form complexes with some transition metal cations [15] Abstract. New bis(crown ether) ligands of Schiff base type (2 -4) containing recognition sites for sodium and nickel guest cations have been synthesized by the condensations of two equivalents of 4'-formyl-5'-hydroxy(benzo-15-crown-5) (1) with diamines, H 2 N-(CH 2 ) n -NH 2 (n = 2 -4). Homonuclear ditopic crystalline 2 : 1 (Na + : ligand) complexes (2a -4a, 2b -4b) of the ligands with NaSCN and NaClO 4 have been prepared. The NaClO 4 complexes of 3 and 4 (3b and 4b) form heteronuclear tritopic crystalline complexes withIn this paper, we describe the synthesis of new tritopic bis(crown ether)s 3 and 4 (Scheme 1) characteristic of a double Schiff base structure connecting two salicylidene modified benzo-15-crown-5 rings via alkyl chains of different length that are homologues of 2. Homobinuclear sodium thiocyanate (2a -4a) and sodium perchlorate complexes (2b -4b), heterotrinuclear sodiumnickel(II) complexes (3c and 4c) as well as a mononuclear nickel(II) complex (3d) including the salient features of their IR, 1 H-, 13 C-NMR, UV-VIS and MS spectra are reported. SynthesisThe starting compounds, benzo-15-crown-5 (B15C5) [17], 4'-formyl -B15C5 [18], 4'-hydroxy-B15C5 [19] and 4'-formyl-5'-hydroxy-B15C5 (1) [20] were prepared according to literature methods. The bis(crown ether) Schiff base ligand 2 has been obtained previously [20], unlike the corresponding binuclear sodium complexes 2a and 2b of 2 which are new. These complexes (2a and 2b) were prepared to draw a comparison with the binuclear sodium complexes of the ligand homologues 3 and 4 (3a, 3b, 4a and 4b) in order to see the effect of the linking aliphatic chain length [-(CH 2 ) n -; n = 2, 3, 4]. The ligands 3 and 4 as well as their complexes are new compounds. Yields, elemental analyses and physical data ...

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Tautomerism in Chlorinated O-Hydroxyschiff Bases: Effect of Chlorine Atom Substitution

Cited by 26 publications

References 14 publications

Synthesis and Spectroscopic Characterization of New Schiff Bases Containing the Benzo-15-Crown-5 Moiety

Synthesis and Spectroscopic Characterization of New Schiff Bases Containing the Benzo-15-Crown-5 Moiety

Cosolvent tuning of tautomeric equilibrium in supercritical fluids

Synthesis and characterization of new bis(crown ether)s of Schiff base type containing recognition sites for sodium and nickel guest cations

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