8 research outputs found
Quinolines by Three-Component Reaction: Synthesis and Photophysical Studies
<div><p>The synthesis of five quinolines 8-octyloxy-4-[4-(octyloxy)phenyl]quinoline and 6-alkoxy- 2-(4-alkoxyphenyl)-4-[(4-octyloxy)aryl]quinolines are described by three-component coupling reaction mediated by Lewis acid FeCl3 and Yb(OTf)3. 4-n-octyloxybenzaldehyde, anisaldehyde, 4-n-octyloxyaniline p-anisidine, and 1-ethynyl-4-heptyloxybenzene, 1-ethynyl-4-octyloxybenzene and 2-ethynyl-6-heptyloxynaphthalene are the reagents in this protocol. A Yb3+ catalyst resulted in higher yields of quinolines than Fe3+. Polarizing optical microscopy (POM) revealed that none of the quinolines were liquid crystals, even the more anisotropic. UV-Vis measurements of one of the quinolines in polar solvent show two absorption bands at 280 and 350 nm related to Ļ,Ļ* and n,Ļ* transitions. No changes were observed to lower-energy absorption band (Īµ < 104 mol L-1 cm-1) related to n,Ļ* transition. A laser flash photolysis study for one of the quinolines relates a main transient band at 450 nm with a lifetime of 2.6 Āµs in ethanol, which is completely quenched in the presence of oxygen. This transient band was assigned to triplet-triplet absorption of one of the quinolines, which is semi-oxidised in the presence of phenol. Radiative rate constants have been determined along singlet and triplet excited state energies (3.39 and 3.10 eV, respectively). The chemical structure of one of the quinolines was also unequivocally confirmed by single-crystal X-ray analysis.</p></div
New La(III) Complex Immobilized on 3āAminopropyl-Functionalized Silica as an Efficient and Reusable Catalyst for Hydrolysis of Phosphate Ester Bonds
Described
herein is the synthesis, structure, and monoesterase and diesterase
activities of a new mononuclear [La<sup>III</sup>(L<sup>1</sup>)Ā(NO<sub>3</sub>)<sub>2</sub>] (<b>1</b>) complex (H<sub>2</sub>L<sup>1</sup> = 2-bisĀ[{(2-pyridylmethyl)-aminomethyl}-6-[<i>N</i>-(2-pyridylmethyl) aminomethyl)])-4-methyl-6-formylphenol) in the
hydrolysis of 2,4-bisĀ(dinitrophenyl)Āphosphate (2,4-BDNPP). When covalently
linked to 3-aminopropyl-functionalized silica, <b>1</b> undergoes
disproportionation to form a dinuclear species (<b>APS-1</b>), whose catalytic efficiency is increased when compared to the homogeneous
reaction due to second coordination sphere effects which increase
the substrate to complex association constant. The anchored catalyst <b>APS-1</b> can be recovered and reused for subsequent hydrolysis
reactions (five times) with only a slight loss in activity. In the
presence of DNA, we suggest that <b>1</b> is also converted
into the dinuclear active species as observed with <b>APS-1</b>, and both were shown to be efficient in DNA cleavage
Second-Coordination-Sphere Effects Increase the Catalytic Efficiency of an Extended Model for Fe<sup>III</sup>M<sup>II</sup> Purple Acid Phosphatases
Herein we describe the synthesis
of a new heterodinuclear Fe<sup>III</sup>Cu<sup>II</sup> model complex
for the active site of purple acid phosphatases and its binding to
a polyamine chain, a model for the amino acid residues around the
active site. The properties of these systems and their catalytic activity
in the hydrolysis of bisĀ(2,4-dinitrophenyl)Āphosphate are compared,
and conclusions regarding the effects of the second coordination sphere
are drawn. The positive effect of the polymeric chain on DNA hydrolysis
is also described and discussed
Second-Coordination-Sphere Effects Increase the Catalytic Efficiency of an Extended Model for Fe<sup>III</sup>M<sup>II</sup> Purple Acid Phosphatases
Herein we describe the synthesis
of a new heterodinuclear Fe<sup>III</sup>Cu<sup>II</sup> model complex
for the active site of purple acid phosphatases and its binding to
a polyamine chain, a model for the amino acid residues around the
active site. The properties of these systems and their catalytic activity
in the hydrolysis of bisĀ(2,4-dinitrophenyl)Āphosphate are compared,
and conclusions regarding the effects of the second coordination sphere
are drawn. The positive effect of the polymeric chain on DNA hydrolysis
is also described and discussed
Synthesis and Solvatochromism of Substituted 4ā(Nitrostyryl)phenolate Dyes
4-(Nitrostyryl)Āphenols <b>2a</b>ā<b>9a</b> were
synthesized, and by deprotonation in solution, the solvatochromic
phenolates <b>2b</b>ā<b>9b</b> were formed. Their
absorption bands in the vis region of the spectra are due to ĻāĻ*
electronic transitions, of an intramolecular charge-transfer nature,
from the electron-donor phenolate toward the electron-acceptor nitroarene
moiety. The frontier molecular orbitals and natural bond orbitals
were analyzed for the protonated and deprotonated forms. The calculated
geometries are in agreement with X-ray structures observed for <b>4a</b>, <b>6a</b>, and <b>8a</b>. The HOMOāLUMO
energy gaps suggest that, after their deprotonation, an increase in
the electron delocalization is observed. In the protonated compounds,
the HOMO is primarily localized over the phenol ring and the Cī»C
bridge. After deprotonation, it extends toward the entire molecule,
including the NO<sub>2</sub> groups. The solvatochromism of each dye
was studied in 28 organic solvents, and it was found that all compounds
exhibit a reversal in solvatochromism, which is interpreted in terms
of the ability of the media to stabilize their electronic ground and
excited states to different extents. The CatalaĢn multiparameter
equation is used in the interpretation of the solvatochromic data,
revealing that the most important contribution to the solute/solvent
interaction is the hydrogen-bond donor acidity of the solvent
Synthesis, Magnetostructural Correlation, and Catalytic Promiscuity of Unsymmetric Dinuclear Copper(II) Complexes: Models for Catechol Oxidases and Hydrolases
Herein, we report the synthesis and characterization,
through elemental
analysis, electronic spectroscopy, electrochemistry, potentiometric
titration, electron paramagnetic resonance, and magnetochemistry,
of two dinuclear copperĀ(II) complexes, using the unsymmetrical ligands <i>N</i>ā²,<i>N</i>ā²,<i>N</i>-trisĀ(2-pyridylmethyl)-<i>N</i>-(2-hydroxy-3,5-di-<i>tert</i>-butylbenzyl)-1,3-propanediamin-2-ol
(<b>L1</b>) and <i>N</i>ā²,<i>N</i>ā²-bisĀ(2-pyridylmethyl)-<i>N</i>,<i>N</i>-(2-hydroxybenzyl)Ā(2-hydroxy-3,5-di-<i>tert</i>-butylbenzyl)-1,3-propanediamin-2-ol
(<b>L2</b>). The structures of the complexes [Cu<sub>2</sub>(<b>L1</b>)Ā(Ī¼-OAc)]Ā(ClO<sub>4</sub>)<sub>2</sub>Ā·(CH<sub>3</sub>)<sub>2</sub>CHOH (<b>1</b>) and [Cu<sub>2</sub>(<b>L2</b>)Ā(Ī¼-OAc)]Ā(ClO<sub>4</sub>)Ā·H<sub>2</sub>OĀ·(CH<sub>3</sub>)<sub>2</sub>CHOH (<b>2</b>) were determined by X-ray
crystallography. The complex [Cu<sub>2</sub>(<b>L3</b>)Ā(Ī¼-OAc)]<sup>2+</sup> [<b>3</b>; <b>L3</b> = <i>N</i>-(2-hydroxybenzyl)-<i>N</i>ā²,<i>N</i>ā²,<i>N</i>-trisĀ(2-pyridylmethyl)-1,3-propanediamin-2-ol]
was included in this study for comparison purposes only (Neves et
al. <i>Inorg. Chim. Acta</i> <b>2005</b>, <i>358</i>, 1807ā1822). Magnetic data show that the Cu<sup>II</sup> centers in <b>1</b> and <b>2</b> are antiferromagnetically
coupled and that the difference in the exchange coupling <i>J</i> found for these complexes (<i>J</i> = ā4.3 cm<sup>ā1</sup> for <b>1</b> and <i>J</i> = ā40.0
cm<sup>ā1</sup> for <b>2</b>) is a function of the CuāOāCu
bridging angle. In addition, <b>1</b> and <b>2</b> were
tested as catalysts in the oxidation of the model substrate 3,5-di-<i>tert</i>-butylcatechol and can be considered as functional models
for catechol oxidase. Because these complexes possess labile sites
in their structures and in solution they have a potential nucleophile
constituted by a terminal Cu<sup>II</sup>-bound hydroxo group, their
activity toward hydrolysis of the model substrate 2,4-bisĀ(dinitrophenyl)Āphosphate
and DNA was also investigated. Double electrophilic activation of
the phosphodiester by monodentate coordination to the Cu<sup>II</sup> center that contains the phenol group with <i>tert</i>-butyl substituents and hydrogen bonding of the protonated phenol
with the phosphate O atom are proposed to increase the hydrolase activity
(<i>K</i><sub>ass.</sub> and <i>k</i><sub>cat.</sub>) of <b>1</b> and <b>2</b> in comparison with that found
for complex <b>3</b>. In fact, complexes <b>1</b> and <b>2</b> show both oxidoreductase and hydrolase/nuclease activities
and can thus be regarded as man-made models for studying catalytic
promiscuity
Synthesis, Magnetostructural Correlation, and Catalytic Promiscuity of Unsymmetric Dinuclear Copper(II) Complexes: Models for Catechol Oxidases and Hydrolases
Herein, we report the synthesis and characterization,
through elemental
analysis, electronic spectroscopy, electrochemistry, potentiometric
titration, electron paramagnetic resonance, and magnetochemistry,
of two dinuclear copperĀ(II) complexes, using the unsymmetrical ligands <i>N</i>ā²,<i>N</i>ā²,<i>N</i>-trisĀ(2-pyridylmethyl)-<i>N</i>-(2-hydroxy-3,5-di-<i>tert</i>-butylbenzyl)-1,3-propanediamin-2-ol
(<b>L1</b>) and <i>N</i>ā²,<i>N</i>ā²-bisĀ(2-pyridylmethyl)-<i>N</i>,<i>N</i>-(2-hydroxybenzyl)Ā(2-hydroxy-3,5-di-<i>tert</i>-butylbenzyl)-1,3-propanediamin-2-ol
(<b>L2</b>). The structures of the complexes [Cu<sub>2</sub>(<b>L1</b>)Ā(Ī¼-OAc)]Ā(ClO<sub>4</sub>)<sub>2</sub>Ā·(CH<sub>3</sub>)<sub>2</sub>CHOH (<b>1</b>) and [Cu<sub>2</sub>(<b>L2</b>)Ā(Ī¼-OAc)]Ā(ClO<sub>4</sub>)Ā·H<sub>2</sub>OĀ·(CH<sub>3</sub>)<sub>2</sub>CHOH (<b>2</b>) were determined by X-ray
crystallography. The complex [Cu<sub>2</sub>(<b>L3</b>)Ā(Ī¼-OAc)]<sup>2+</sup> [<b>3</b>; <b>L3</b> = <i>N</i>-(2-hydroxybenzyl)-<i>N</i>ā²,<i>N</i>ā²,<i>N</i>-trisĀ(2-pyridylmethyl)-1,3-propanediamin-2-ol]
was included in this study for comparison purposes only (Neves et
al. <i>Inorg. Chim. Acta</i> <b>2005</b>, <i>358</i>, 1807ā1822). Magnetic data show that the Cu<sup>II</sup> centers in <b>1</b> and <b>2</b> are antiferromagnetically
coupled and that the difference in the exchange coupling <i>J</i> found for these complexes (<i>J</i> = ā4.3 cm<sup>ā1</sup> for <b>1</b> and <i>J</i> = ā40.0
cm<sup>ā1</sup> for <b>2</b>) is a function of the CuāOāCu
bridging angle. In addition, <b>1</b> and <b>2</b> were
tested as catalysts in the oxidation of the model substrate 3,5-di-<i>tert</i>-butylcatechol and can be considered as functional models
for catechol oxidase. Because these complexes possess labile sites
in their structures and in solution they have a potential nucleophile
constituted by a terminal Cu<sup>II</sup>-bound hydroxo group, their
activity toward hydrolysis of the model substrate 2,4-bisĀ(dinitrophenyl)Āphosphate
and DNA was also investigated. Double electrophilic activation of
the phosphodiester by monodentate coordination to the Cu<sup>II</sup> center that contains the phenol group with <i>tert</i>-butyl substituents and hydrogen bonding of the protonated phenol
with the phosphate O atom are proposed to increase the hydrolase activity
(<i>K</i><sub>ass.</sub> and <i>k</i><sub>cat.</sub>) of <b>1</b> and <b>2</b> in comparison with that found
for complex <b>3</b>. In fact, complexes <b>1</b> and <b>2</b> show both oxidoreductase and hydrolase/nuclease activities
and can thus be regarded as man-made models for studying catalytic
promiscuity
Synthesis, Magnetostructural Correlation, and Catalytic Promiscuity of Unsymmetric Dinuclear Copper(II) Complexes: Models for Catechol Oxidases and Hydrolases
Herein, we report the synthesis and characterization,
through elemental
analysis, electronic spectroscopy, electrochemistry, potentiometric
titration, electron paramagnetic resonance, and magnetochemistry,
of two dinuclear copperĀ(II) complexes, using the unsymmetrical ligands <i>N</i>ā²,<i>N</i>ā²,<i>N</i>-trisĀ(2-pyridylmethyl)-<i>N</i>-(2-hydroxy-3,5-di-<i>tert</i>-butylbenzyl)-1,3-propanediamin-2-ol
(<b>L1</b>) and <i>N</i>ā²,<i>N</i>ā²-bisĀ(2-pyridylmethyl)-<i>N</i>,<i>N</i>-(2-hydroxybenzyl)Ā(2-hydroxy-3,5-di-<i>tert</i>-butylbenzyl)-1,3-propanediamin-2-ol
(<b>L2</b>). The structures of the complexes [Cu<sub>2</sub>(<b>L1</b>)Ā(Ī¼-OAc)]Ā(ClO<sub>4</sub>)<sub>2</sub>Ā·(CH<sub>3</sub>)<sub>2</sub>CHOH (<b>1</b>) and [Cu<sub>2</sub>(<b>L2</b>)Ā(Ī¼-OAc)]Ā(ClO<sub>4</sub>)Ā·H<sub>2</sub>OĀ·(CH<sub>3</sub>)<sub>2</sub>CHOH (<b>2</b>) were determined by X-ray
crystallography. The complex [Cu<sub>2</sub>(<b>L3</b>)Ā(Ī¼-OAc)]<sup>2+</sup> [<b>3</b>; <b>L3</b> = <i>N</i>-(2-hydroxybenzyl)-<i>N</i>ā²,<i>N</i>ā²,<i>N</i>-trisĀ(2-pyridylmethyl)-1,3-propanediamin-2-ol]
was included in this study for comparison purposes only (Neves et
al. <i>Inorg. Chim. Acta</i> <b>2005</b>, <i>358</i>, 1807ā1822). Magnetic data show that the Cu<sup>II</sup> centers in <b>1</b> and <b>2</b> are antiferromagnetically
coupled and that the difference in the exchange coupling <i>J</i> found for these complexes (<i>J</i> = ā4.3 cm<sup>ā1</sup> for <b>1</b> and <i>J</i> = ā40.0
cm<sup>ā1</sup> for <b>2</b>) is a function of the CuāOāCu
bridging angle. In addition, <b>1</b> and <b>2</b> were
tested as catalysts in the oxidation of the model substrate 3,5-di-<i>tert</i>-butylcatechol and can be considered as functional models
for catechol oxidase. Because these complexes possess labile sites
in their structures and in solution they have a potential nucleophile
constituted by a terminal Cu<sup>II</sup>-bound hydroxo group, their
activity toward hydrolysis of the model substrate 2,4-bisĀ(dinitrophenyl)Āphosphate
and DNA was also investigated. Double electrophilic activation of
the phosphodiester by monodentate coordination to the Cu<sup>II</sup> center that contains the phenol group with <i>tert</i>-butyl substituents and hydrogen bonding of the protonated phenol
with the phosphate O atom are proposed to increase the hydrolase activity
(<i>K</i><sub>ass.</sub> and <i>k</i><sub>cat.</sub>) of <b>1</b> and <b>2</b> in comparison with that found
for complex <b>3</b>. In fact, complexes <b>1</b> and <b>2</b> show both oxidoreductase and hydrolase/nuclease activities
and can thus be regarded as man-made models for studying catalytic
promiscuity