X-Ray crystallographic and spectroscopic properties of eight Schiff bases as evidence of the proton transfer reaction. Role of the intermolecular hydrogen bond

Dominguez, Oscar V.; Rodrı́guez-Molina, Braulio; Rodríguez, Mario; Ariza, A.; Farfán, Norberto; Santillán, Rosa

doi:10.1039/c0nj00179a

Cited by 23 publications

(25 citation statements)

References 86 publications

(7 reference statements)

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“…The observed fluorescence enhancement for receptor L2 was ca. 18 Spectrophotometric titrations of most metal salts produced almost no change in absorption spectra; however, when Zn 2+ was added to these solutions a new absorption band at 385 nm for L1 and 360 nm for L2 was observed. The fluorescence and UV-Vis spectra of L1 and L2 towards other metal ions are presented in Figure S1 †.…”

Section: Zn 2+ Fluorescent Responsementioning

confidence: 95%

Two fluorescent Schiff base sensors for Zn²⁺: the Zn²⁺/Cu²⁺ion interference

Jiménez‐Sánchez

Ortíz

Ortiz-Navarrete

et al. 2015

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Two simple and low cost 2,4-di-tert-butyl-6-[(1-hydroxycyclohexylmethylimino)methyl]phenol (L1) and 2-[{(1-hydroxycyclohexyl)methylimino}methyl]phenol (L2) Schiff base sensors exhibiting selectivity for Zn(2+) in water:methanol (95:5, v/v, 10 mM HEPES) are described. L1 and L2 display an "off-on" fluorescence effect forming the L1·Zn and L2·Zn complexes, respectively. In the case of L1·Zn, the emission response is quenched by the addition of Cu(2+) forming the respective L1·Cu complex; in spite of that, the fluorescence signal can be completely restored only by the addition of tartrate anions (C4H4O6(2-)) forming again L1·Znvia the "off-on" displacement approach. However, in the case of L2·Zn no Cu(2+) interference is observed, which is a typical problem for Zn(2+) sensors. Here we describe that a very subtle structural change in the ligand during transition from the enol-imine tautomer in L1 to the keto-enamine tautomer in L2 is enough to modulate the Zn(2+)/Cu(2+) selectivity. Also, the Zn(2+)vs. Cd(2+) discrimination for L1 and L2 is proved. Moreover, we found that the interaction between both L·Zn complexes and tartrate anions completely restored the free ligands by the ligand substitution mechanism even in a more efficient association than phosphate anions. Further, a second colorimetric response channel upon addition of Fe(2+) was observed for L1 and L2. Then, TD-DFT theoretical calculations were conducted in order to study the efficiency of the sensors to give different responses in the presence of such metal ions. Finally, the L2 sensor successfully detects Zn(2+) in Jurkat cells cultured with and without Zn(2+) enriched medium.

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Section: Zn 2+ Fluorescent Responsementioning

confidence: 95%

Two fluorescent Schiff base sensors for Zn²⁺: the Zn²⁺/Cu²⁺ion interference

Jiménez‐Sánchez

Ortíz

Ortiz-Navarrete

et al. 2015

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“…These compounds can display interesting properties, such as photochromism,t hermochromism, coordination ability,a nd molecular recognition, and continue to attract wide interest because of their applications. [193][194][195][196][197][198][199][200] The structures of keto and zwitterionic forms can be regarded as extreme canonical forms of ar eso-nance hybrid, although experimentally derived bond lengths reflect the predominance of one form. [189][190][191][192] The presence of an ortho-OH group is as tructuralr equirement for the photochromism of these compounds and the proposed H-transfer mechanism.Areversible tautomeric equilibrium, OÀH···NÐNÀH···O, assisted by electrostatic differences betweent he oxygen and nitrogen atoms of the salicylideneimine fragment, promotes the delocalization of the aromatic p-electron system leadingt oaq uinoid form, which is also related to its canonical zwitterionic form, supported by CAHB (Scheme 19).…”

Section: Synthesis Of Schiff Basesmentioning

confidence: 99%

“…[193][194][195][196][197][198][199][200] The structures of keto and zwitterionic forms can be regarded as extreme canonical forms of ar eso-nance hybrid, although experimentally derived bond lengths reflect the predominance of one form. [199][200][201][202] Electron delocalization in these systems, which are susceptible to proton transfer,r epresents au seful concept to rationalize the structure and reactivity of av ariety of Schiff bases. In fact, most Schiff bases derived from salicylaldehydes and alkyl/arylamines adopt imine structures (enol), [189-192, 199, 201] but some derivatives have been reported with enamine skeletons (keto and zwitterionic forms)i nt he solid state.…”

Section: Synthesis Of Schiff Basesmentioning

confidence: 99%

Resonance‐Assisted Hydrogen Bonding as a Driving Force in Synthesis and a Synthon in the Design of Materials

Mahmudov

Pombeiro

2016

Chemistry A European J

140

100

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Resonance-assisted hydrogen bonding (RAHB), a concept introduced by Gilli and co-workers in 1989, concerns a kind of intramolecular H-bonding strengthened by a conjugated π-system, usually in 6-, 8-, or 10-membered rings. This Review highlights the involvement of RAHB as a driving force in the synthesis of organic, coordination, and organometallic compounds, as a handy tool in the activation of covalent bonds, and in starting moieties for synthetic transformations. The unique roles of RAHB in molecular recognition and switches, E/Z isomeric resolution, racemization and epimerization of amino acids and chiral amino alcohols, solvatochromism, liquid-crystalline compounds, and in synthons for crystal engineering and polymer materials are also discussed. The Review can provide practical guidance for synthetic chemists that are interested in exploring and further developing RAHB-assisted synthesis and design of materials.

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“…For related structures, see: Tahir et al (2010a,b). For further synthetic details, see: Rodríguez et al (2007); Domínguez et al (2011…”

Section: Related Literaturementioning

confidence: 99%