Sofia Nikolaou - Academia.edu (original) (raw)
Papers by Sofia Nikolaou
Magnetic Resonance in Chemistry, 1999
The previous assignment of the 13C NMR spectra of triangular clusters
Coordination Chemistry Reviews, 2001
Journal of Inorganic Biochemistry, 2015
This work presents the synthesis and characterization of two novel binuclear ruthenium compounds ... more This work presents the synthesis and characterization of two novel binuclear ruthenium compounds of general formula [Ru 2 O(carb) 2 (py) 6 ](PF 6 ) 2 , where py = pyridine and carb are the non-steroidal anti-inflammatory drugs ibuprofen (1) and ketoprofen (2). Both complexes were characterized by ESI-MS/MS spectrometry. The fragmentation patterns, which confirm the proposed structures, are presented. Besides that, compounds 1 and 2 present the charge transfer transitions within 325-330 nm; and the intra-core transitions around 585 nm, which is the typical spectra profile for [Ru 2 O] analogues. This suggests the carboxylate bridge has little influence in their electronic structure. The effects of the diruthenium complexes on Ig-E mediated mast cell activation were evaluated by measuring the enzyme β-hexosaminidase released by mast cells stimulated by antigen. The inhibitory potential of the ketoprofen complex against mast cell stimulation suggests its promising application as a therapeutic agent for treating or preventing IgE-mediated allergic diseases. In addition, in vitro metabolism assays had shown that the ibuprofen complex is metabolized by the cytochrome P450 enzymes.
Coordination Chemistry Reviews, 2001
![Research paper thumbnail of Synthesis, spectroscopy, tandem mass spectrometry, and electrochemistry of the linearly bridged μ-{ trans-1,4-bis[2-(4-pyridyl)ethenyl]-benzene}-{Ru 3O(CH 3COO) 6(py) 2} 2 cluster](https://attachments.academia-assets.com/43239598/thumbnails/1.jpg)
](Inorganica Chimica Acta - INORG CHIM ACTA, 2004
The novel polynuclear [{Ru3O(CH3COO)6(py)2}2(BPEB)](PF6)2 species containing the linear bridging ... more The novel polynuclear [{Ru3O(CH3COO)6(py)2}2(BPEB)](PF6)2 species containing the linear bridging trans-1,4-bis[2-(4-pyridyl)ethenyl]-benzene ligand (BPEB) was synthesized and its structural characterization carried out by means of positive ion electrospray (ESI-MS) and tandem mass (ESI-MS/MS) spectrometry, as well as by 1H NMR spectroscopy. The doubly charged cation [{Ru3O(CH3COO)6(py)2}2(BPEB)]2+ was detected in the ESI-MS mass spectrum as a multiple-component isotopomeric ionic cluster centered at m/z 974, which ion abundance and m/z distribution matched perfectly the isotopic pattern calculated for this multiple isotope Ru3-containing ion. The tandem mass spectrum of [{Ru3O(CH3COO)6(py)2}2(BPEB)]2+ provided a structural diagnostic dissociation behavior, on the basis of the characteristic charge splitting and sequential ligand loss steps. The cyclic voltammograms of the complex exhibited a quasi-reversible multistep redox behavior, displaying three waves at 1.14, 0.08, and −1.21 V...
Spectroscopy Letters, 2001
The bridged ruthenium cluster-polypyridine dimer [Ru 3 O (CH 3 COO) 6 (py) 2 (tmbpy)Ru(bpy) 2 (Cl... more The bridged ruthenium cluster-polypyridine dimer [Ru 3 O (CH 3 COO) 6 (py) 2 (tmbpy)Ru(bpy) 2 (Cl)](PF 6 ) 2 (py = pyridine, bpy = 2,2 -bipyridine and tmbpy = 4,4 -trimethylenedipyridine) has been synthesized and structurally characterized based on 1 H and 13 C NMR spectroscopy. This species exhibits a complex pattern of NMR signals due to the presence of a paramagnetic [Ru 3 O] core and seven non-equivalent aromatic rings. 2D NMR (COSY, HMQC and HMBC) correlation techniques have been required for the total assignment of the 1 H and 13 C NMR spectra.
Magnetic Resonance in Chemistry, 1999
The previous assignment of the 13C NMR spectra of triangular clusters
Journal of Inorganic Biochemistry, 2014
In vitro cytotoxicity study of the [Ru 3 O(CH 3 COO) 6 (4-pic) 2 (NO)]PF 6 triruthenium nitrosyl ... more In vitro cytotoxicity study of the [Ru 3 O(CH 3 COO) 6 (4-pic) 2 (NO)]PF 6 triruthenium nitrosyl cluster (compound 1, 4-pic = 4-methylpyridine) against B16F10 melanoma cell line was evaluated in the presence and absence of visible light irradiation. The nitrosyl cluster 1 showed a significant tumoricidal activity when irradiated at λ = 532 nm, reducing cell viability up to 90% at a concentration of 62.5 μM. However, cell death of 60% is also observed in the dark which can be assigned to the NO release mediated by a redox reaction of the cluster in cell medium. This possibility was confirmed by amperometric detection of NO after the addition of ascorbic acid to compound 1 in phosphate buffer. A control experiment was performed with the solvated cluster [Ru 3 O(CH 3 COO) 6 (4-pic) 2 (CH 3 OH)]PF 6 (compound 2) and no significant lowering of cell viability was observed. These results suggest that the nitrosyl cluster acts as a pro-drug, delivering NO, which is the actual active species.
Journal of Coordination Chemistry, 2012
This work presents two potential metallo-drugs, the ionic (C 17 H 19 FN 3 O 3 ) 3 [RuCl 6 ] Á 3H ... more This work presents two potential metallo-drugs, the ionic (C 17 H 19 FN 3 O 3 ) 3 [RuCl 6 ] Á 3H 2 O (1) and the coordination [Ru(C 17 H 17 FN 3 O 3 ) 3 ] Á 4H 2 O (2) compounds, obtained by the combination of ruthenium(III) and ciprofloxacin in different synthetic conditions. The ESI MS spectrum of 1 displayed a main peak at m/z ¼ 994.6, assigned to the gaseous phase adduct (ciprofloxacin) 3 Á H þ , while 2 featured peaks at m/z 1093.3 and 547.1 ascribed to [Ru(C 17 2þ . Thermal analysis corroborated the proposed water content for both complexes. Absorption spectra of the compounds in aqueous medium are dominated by ciprofloxacin transitions in the UV region but displayed weak bands in the visible region, assigned to ligand field transitions. The cyclic voltammograms of 2 exhibited a quasi-reversible process ascribed to the Ru(II)/(III) redox pair at À0.25 V (vs. SHE) while 1 displayed this process at À0.11 V, showing that the central ruthenium ion is stabilized in the (III) oxidation state by the coordination to the hard oxygen atoms of ciprofloxacin. The solubility of 1 is pH dependent (as well as free ciprofloxacin) while 2 is fully water soluble and stable under physiological pH for at least 48 h. The compounds are also stable under incubation conditions (stomach pH and 37 C) without significant pH lowering. An interaction study of 2 with ct-DNA showed a value of K b ¼ 2.47 (AE0.89) Â 10 4 mol À1 L for the intrinsic binding constant.
Inorganica Chimica Acta, 2011
This work reports on the bimolecular sensitization of nitric oxide release from cis-[Ru(bpy) 2 (i... more This work reports on the bimolecular sensitization of nitric oxide release from cis-[Ru(bpy) 2 (iso)-NO](PF 6 ) 3 (1) (iso = isoquinoline and bpy = 2,2 0 -bipyridine) by irradiating the MLCT transition of the chloro analog cis-[Ru(bpy) 2 (iso)Cl]PF 6 (2) . The compounds displayed peaks in the ESI-MS spectra at m/z 749.1 and m/z 578.1 ascribed, respectively, to ([1(NO 0 )À2PF 6 ÁCH 3 OH] 2+ ) and ([2ÀPF 6 ] + ). In the cyclic voltammograms, the nitrosyl complex presented two redox waves related to the NO ligand at 0.48 and À0.37 V (versus Ag/AgCl, NO +/0/À1 processes), while the sensitizer showed two reversible waves at 0.79 and À1.46 V (versus Ag/AgCl, Ru 2+/3+ and bpy 0/À1 , respectively). The most important feature of this system is that the nitrosyl compound does not have significant absorption in the visible region, while the sensitizer has an intense band centered at 496 nm. The irradiation of an equimolar mixture of the two compounds in an ethanol:water solution (v:v) with light of k > 500 nm leads to NO release, as probed by amperometric measurements. The variational method was applied, showing that the two compounds self-assembly in solution with a 1:1 stoichiometry. Fluorescence spectra acquired at 77 K provided the E 0-0 for the system and, from the thermodynamic cycle it was estimated that the photoinduced electron transfer between the species has a DG value of À1.59 eV.
Inorganica Chimica Acta, 2012
A general strategy for the assembly of dendrimeric metallo-cluster species based on tritopic trin... more A general strategy for the assembly of dendrimeric metallo-cluster species based on tritopic trinuclear ruthenium acetate complexes is demonstrated. First, a central core consisting of a [Ru 3 O(CH 3 COO) 6 (TPEB) 3 ]PF 6 complex (G0), where TPEB is the tripodal 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene ligand, was synthesized and then reacted with the end-capping complex [Ru 3 O(CH 3 COO) 6 (py) 2 (MeOH)]PF 6 , thus composing the first generation shell of a dendrimer encompassing twenty-one ruthenium ions (G1). The core and dendrimeric complexes were characterized by elemental analysis, UV-Vis, 1 H NMR, ESI-MS spectrometry and Differential pulse voltammetry. All results were consistent with the structure of that multinuclear cationic dendrimeric species. The isotopologic profile of daughter fragments and the strength of the metal-ligand bonds were carefully investigated providing the fragmentation pathway for the metallo-dendrimer upon ESI-MS dissociation conditions.
Inorganic Chemistry, 2005
The synthesis of cis-[Ru II (cyclen)(L) x ] n+ (cyclen ) 1,4,7,10tetraazacyclododecane and L ) 2,... more The synthesis of cis-[Ru II (cyclen)(L) x ] n+ (cyclen ) 1,4,7,10tetraazacyclododecane and L ) 2,2′-bipyridine (bpy), phenanthroline (phen) or 4-cyanopyridinium (4-NCpyH + )) is reported. The freshly prepared complexes are stable in aprotic solvents and cyclen undergoes oxidative dehydrogenation reaction at high pH. These compounds also present solvent dependent conformational isomerization.
Inorganic Chemistry Communications, 2012
The cis to trans isomerizations during the syntheses of trans-[Ru(NO)(OH)(cyclam)](PF 6 ) 2 , fro... more The cis to trans isomerizations during the syntheses of trans-[Ru(NO)(OH)(cyclam)](PF 6 ) 2 , from cis-[RuCl 2 (cyclam)]Cl, and [Ru(NO)Cl(cyclam)] (PF 6 ) 2 , from cis-[RuCl 2 (dmso) 4 ], are reported. The novel trans-[Ru(NO) (OH)(cyclam)](PF 6 ) 2 complex was characterized by X-ray crystallography and vibrational infrared and nuclear magnetic resonance spectroscopies. The Ru-N-O bond angle (176.75º) and ν(NO) (1835 cm − 1 ) suggest a nitrosonium character for this hydroxo complex. The crystal and molecular structure of trans-[Ru(NO)Cl(cyclam)] (ClO 4 ) 2 ·2 H 2 O is also reported. Results presented here support the cis-trans isomerization observed for the first time with ruthenium cyclam complexes.
![Research paper thumbnail of A Convergent Approach for the Generation of Dendrimers Containing the [Ru3O(CH3COO)6] Electroactive Core](https://attachments.academia-assets.com/43239610/thumbnails/1.jpg)
](European Journal of Inorganic Chemistry, 2008
We report on a convergent approach for the generation of dendrimers containing the [Ru 3 O(ac) 6 ... more We report on a convergent approach for the generation of dendrimers containing the [Ru 3 O(ac) 6 ] electroactive core, of great interest as multielectron transfer catalysts. The proposed strategy is based on the generation of the trimeric complex [{Ru 3 O(ac) 6 (4-pic) 2 (pz)} 2 -µ 2 -Ru 3 O(ac) 6 (CH 3 OH)] 3+ (ac = acetate, 4-pic = 4-methylpyridine, pz = pyrazine). In this complex, the labile CH 3 OH ligand can be displaced by the
Journal of Physical Chemistry A, 2006
In this work, the interaction between fisetin (3,3′,4′,7-tetrahydroxyflavone) (Fis) and cyclodext... more In this work, the interaction between fisetin (3,3′,4′,7-tetrahydroxyflavone) (Fis) and cyclodextrins (CDs) (R and ) was studied through UV-vis absorption, steady-state fluorescence, induced circular dichroism, and 1 H NMR experiments with dependence on temperature and pH. Some experimental data were compared with quantum-mechanics studies based on the SAM1 (AMPAC) semiempirical model, as well as with the B3LYP and MPW1PW91 functional models from density functional theory using the 6-311G* and 3-21G* basis sets. The spectroscopic measurements show that Fis does not form stable complexes with R-CD. On the other hand, at pH 4.0 and 6.5, the complex Fis--CD is formed in a Fis: -CD 1:1 stoichiometry and an equilibrium constant (K) of 900 ( 100 M -1 . In basic medium (pH 11.5), K decreases to 240 ( 90 M -1 because Fis deprotonation leads to its better solubilization in water. Molecular modeling points out that Fis is not totally inserted into the inner cavity of -CD. The formation of the inclusion complex renders an environment that enhances intramolecular excited state proton transfer. The inclusion complex is formed preferentially via entry of the Fis phenyl group into -CD.
Magnetic Resonance in Chemistry, 1999
The previous assignment of the 13C NMR spectra of triangular clusters
Coordination Chemistry Reviews, 2001
Journal of Inorganic Biochemistry, 2015
This work presents the synthesis and characterization of two novel binuclear ruthenium compounds ... more This work presents the synthesis and characterization of two novel binuclear ruthenium compounds of general formula [Ru 2 O(carb) 2 (py) 6 ](PF 6 ) 2 , where py = pyridine and carb are the non-steroidal anti-inflammatory drugs ibuprofen (1) and ketoprofen (2). Both complexes were characterized by ESI-MS/MS spectrometry. The fragmentation patterns, which confirm the proposed structures, are presented. Besides that, compounds 1 and 2 present the charge transfer transitions within 325-330 nm; and the intra-core transitions around 585 nm, which is the typical spectra profile for [Ru 2 O] analogues. This suggests the carboxylate bridge has little influence in their electronic structure. The effects of the diruthenium complexes on Ig-E mediated mast cell activation were evaluated by measuring the enzyme β-hexosaminidase released by mast cells stimulated by antigen. The inhibitory potential of the ketoprofen complex against mast cell stimulation suggests its promising application as a therapeutic agent for treating or preventing IgE-mediated allergic diseases. In addition, in vitro metabolism assays had shown that the ibuprofen complex is metabolized by the cytochrome P450 enzymes.
Coordination Chemistry Reviews, 2001
Inorganica Chimica Acta - INORG CHIM ACTA, 2004
The novel polynuclear [{Ru3O(CH3COO)6(py)2}2(BPEB)](PF6)2 species containing the linear bridging ... more The novel polynuclear [{Ru3O(CH3COO)6(py)2}2(BPEB)](PF6)2 species containing the linear bridging trans-1,4-bis[2-(4-pyridyl)ethenyl]-benzene ligand (BPEB) was synthesized and its structural characterization carried out by means of positive ion electrospray (ESI-MS) and tandem mass (ESI-MS/MS) spectrometry, as well as by 1H NMR spectroscopy. The doubly charged cation [{Ru3O(CH3COO)6(py)2}2(BPEB)]2+ was detected in the ESI-MS mass spectrum as a multiple-component isotopomeric ionic cluster centered at m/z 974, which ion abundance and m/z distribution matched perfectly the isotopic pattern calculated for this multiple isotope Ru3-containing ion. The tandem mass spectrum of [{Ru3O(CH3COO)6(py)2}2(BPEB)]2+ provided a structural diagnostic dissociation behavior, on the basis of the characteristic charge splitting and sequential ligand loss steps. The cyclic voltammograms of the complex exhibited a quasi-reversible multistep redox behavior, displaying three waves at 1.14, 0.08, and −1.21 V...
Spectroscopy Letters, 2001
The bridged ruthenium cluster-polypyridine dimer [Ru 3 O (CH 3 COO) 6 (py) 2 (tmbpy)Ru(bpy) 2 (Cl... more The bridged ruthenium cluster-polypyridine dimer [Ru 3 O (CH 3 COO) 6 (py) 2 (tmbpy)Ru(bpy) 2 (Cl)](PF 6 ) 2 (py = pyridine, bpy = 2,2 -bipyridine and tmbpy = 4,4 -trimethylenedipyridine) has been synthesized and structurally characterized based on 1 H and 13 C NMR spectroscopy. This species exhibits a complex pattern of NMR signals due to the presence of a paramagnetic [Ru 3 O] core and seven non-equivalent aromatic rings. 2D NMR (COSY, HMQC and HMBC) correlation techniques have been required for the total assignment of the 1 H and 13 C NMR spectra.
Magnetic Resonance in Chemistry, 1999
The previous assignment of the 13C NMR spectra of triangular clusters
Journal of Inorganic Biochemistry, 2014
In vitro cytotoxicity study of the [Ru 3 O(CH 3 COO) 6 (4-pic) 2 (NO)]PF 6 triruthenium nitrosyl ... more In vitro cytotoxicity study of the [Ru 3 O(CH 3 COO) 6 (4-pic) 2 (NO)]PF 6 triruthenium nitrosyl cluster (compound 1, 4-pic = 4-methylpyridine) against B16F10 melanoma cell line was evaluated in the presence and absence of visible light irradiation. The nitrosyl cluster 1 showed a significant tumoricidal activity when irradiated at λ = 532 nm, reducing cell viability up to 90% at a concentration of 62.5 μM. However, cell death of 60% is also observed in the dark which can be assigned to the NO release mediated by a redox reaction of the cluster in cell medium. This possibility was confirmed by amperometric detection of NO after the addition of ascorbic acid to compound 1 in phosphate buffer. A control experiment was performed with the solvated cluster [Ru 3 O(CH 3 COO) 6 (4-pic) 2 (CH 3 OH)]PF 6 (compound 2) and no significant lowering of cell viability was observed. These results suggest that the nitrosyl cluster acts as a pro-drug, delivering NO, which is the actual active species.
Journal of Coordination Chemistry, 2012
This work presents two potential metallo-drugs, the ionic (C 17 H 19 FN 3 O 3 ) 3 [RuCl 6 ] Á 3H ... more This work presents two potential metallo-drugs, the ionic (C 17 H 19 FN 3 O 3 ) 3 [RuCl 6 ] Á 3H 2 O (1) and the coordination [Ru(C 17 H 17 FN 3 O 3 ) 3 ] Á 4H 2 O (2) compounds, obtained by the combination of ruthenium(III) and ciprofloxacin in different synthetic conditions. The ESI MS spectrum of 1 displayed a main peak at m/z ¼ 994.6, assigned to the gaseous phase adduct (ciprofloxacin) 3 Á H þ , while 2 featured peaks at m/z 1093.3 and 547.1 ascribed to [Ru(C 17 2þ . Thermal analysis corroborated the proposed water content for both complexes. Absorption spectra of the compounds in aqueous medium are dominated by ciprofloxacin transitions in the UV region but displayed weak bands in the visible region, assigned to ligand field transitions. The cyclic voltammograms of 2 exhibited a quasi-reversible process ascribed to the Ru(II)/(III) redox pair at À0.25 V (vs. SHE) while 1 displayed this process at À0.11 V, showing that the central ruthenium ion is stabilized in the (III) oxidation state by the coordination to the hard oxygen atoms of ciprofloxacin. The solubility of 1 is pH dependent (as well as free ciprofloxacin) while 2 is fully water soluble and stable under physiological pH for at least 48 h. The compounds are also stable under incubation conditions (stomach pH and 37 C) without significant pH lowering. An interaction study of 2 with ct-DNA showed a value of K b ¼ 2.47 (AE0.89) Â 10 4 mol À1 L for the intrinsic binding constant.
Inorganica Chimica Acta, 2011
This work reports on the bimolecular sensitization of nitric oxide release from cis-[Ru(bpy) 2 (i... more This work reports on the bimolecular sensitization of nitric oxide release from cis-[Ru(bpy) 2 (iso)-NO](PF 6 ) 3 (1) (iso = isoquinoline and bpy = 2,2 0 -bipyridine) by irradiating the MLCT transition of the chloro analog cis-[Ru(bpy) 2 (iso)Cl]PF 6 (2) . The compounds displayed peaks in the ESI-MS spectra at m/z 749.1 and m/z 578.1 ascribed, respectively, to ([1(NO 0 )À2PF 6 ÁCH 3 OH] 2+ ) and ([2ÀPF 6 ] + ). In the cyclic voltammograms, the nitrosyl complex presented two redox waves related to the NO ligand at 0.48 and À0.37 V (versus Ag/AgCl, NO +/0/À1 processes), while the sensitizer showed two reversible waves at 0.79 and À1.46 V (versus Ag/AgCl, Ru 2+/3+ and bpy 0/À1 , respectively). The most important feature of this system is that the nitrosyl compound does not have significant absorption in the visible region, while the sensitizer has an intense band centered at 496 nm. The irradiation of an equimolar mixture of the two compounds in an ethanol:water solution (v:v) with light of k > 500 nm leads to NO release, as probed by amperometric measurements. The variational method was applied, showing that the two compounds self-assembly in solution with a 1:1 stoichiometry. Fluorescence spectra acquired at 77 K provided the E 0-0 for the system and, from the thermodynamic cycle it was estimated that the photoinduced electron transfer between the species has a DG value of À1.59 eV.
Inorganica Chimica Acta, 2012
A general strategy for the assembly of dendrimeric metallo-cluster species based on tritopic trin... more A general strategy for the assembly of dendrimeric metallo-cluster species based on tritopic trinuclear ruthenium acetate complexes is demonstrated. First, a central core consisting of a [Ru 3 O(CH 3 COO) 6 (TPEB) 3 ]PF 6 complex (G0), where TPEB is the tripodal 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene ligand, was synthesized and then reacted with the end-capping complex [Ru 3 O(CH 3 COO) 6 (py) 2 (MeOH)]PF 6 , thus composing the first generation shell of a dendrimer encompassing twenty-one ruthenium ions (G1). The core and dendrimeric complexes were characterized by elemental analysis, UV-Vis, 1 H NMR, ESI-MS spectrometry and Differential pulse voltammetry. All results were consistent with the structure of that multinuclear cationic dendrimeric species. The isotopologic profile of daughter fragments and the strength of the metal-ligand bonds were carefully investigated providing the fragmentation pathway for the metallo-dendrimer upon ESI-MS dissociation conditions.
Inorganic Chemistry, 2005
The synthesis of cis-[Ru II (cyclen)(L) x ] n+ (cyclen ) 1,4,7,10tetraazacyclododecane and L ) 2,... more The synthesis of cis-[Ru II (cyclen)(L) x ] n+ (cyclen ) 1,4,7,10tetraazacyclododecane and L ) 2,2′-bipyridine (bpy), phenanthroline (phen) or 4-cyanopyridinium (4-NCpyH + )) is reported. The freshly prepared complexes are stable in aprotic solvents and cyclen undergoes oxidative dehydrogenation reaction at high pH. These compounds also present solvent dependent conformational isomerization.
Inorganic Chemistry Communications, 2012
The cis to trans isomerizations during the syntheses of trans-[Ru(NO)(OH)(cyclam)](PF 6 ) 2 , fro... more The cis to trans isomerizations during the syntheses of trans-[Ru(NO)(OH)(cyclam)](PF 6 ) 2 , from cis-[RuCl 2 (cyclam)]Cl, and [Ru(NO)Cl(cyclam)] (PF 6 ) 2 , from cis-[RuCl 2 (dmso) 4 ], are reported. The novel trans-[Ru(NO) (OH)(cyclam)](PF 6 ) 2 complex was characterized by X-ray crystallography and vibrational infrared and nuclear magnetic resonance spectroscopies. The Ru-N-O bond angle (176.75º) and ν(NO) (1835 cm − 1 ) suggest a nitrosonium character for this hydroxo complex. The crystal and molecular structure of trans-[Ru(NO)Cl(cyclam)] (ClO 4 ) 2 ·2 H 2 O is also reported. Results presented here support the cis-trans isomerization observed for the first time with ruthenium cyclam complexes.
European Journal of Inorganic Chemistry, 2008
We report on a convergent approach for the generation of dendrimers containing the [Ru 3 O(ac) 6 ... more We report on a convergent approach for the generation of dendrimers containing the [Ru 3 O(ac) 6 ] electroactive core, of great interest as multielectron transfer catalysts. The proposed strategy is based on the generation of the trimeric complex [{Ru 3 O(ac) 6 (4-pic) 2 (pz)} 2 -µ 2 -Ru 3 O(ac) 6 (CH 3 OH)] 3+ (ac = acetate, 4-pic = 4-methylpyridine, pz = pyrazine). In this complex, the labile CH 3 OH ligand can be displaced by the
Journal of Physical Chemistry A, 2006
In this work, the interaction between fisetin (3,3′,4′,7-tetrahydroxyflavone) (Fis) and cyclodext... more In this work, the interaction between fisetin (3,3′,4′,7-tetrahydroxyflavone) (Fis) and cyclodextrins (CDs) (R and ) was studied through UV-vis absorption, steady-state fluorescence, induced circular dichroism, and 1 H NMR experiments with dependence on temperature and pH. Some experimental data were compared with quantum-mechanics studies based on the SAM1 (AMPAC) semiempirical model, as well as with the B3LYP and MPW1PW91 functional models from density functional theory using the 6-311G* and 3-21G* basis sets. The spectroscopic measurements show that Fis does not form stable complexes with R-CD. On the other hand, at pH 4.0 and 6.5, the complex Fis--CD is formed in a Fis: -CD 1:1 stoichiometry and an equilibrium constant (K) of 900 ( 100 M -1 . In basic medium (pH 11.5), K decreases to 240 ( 90 M -1 because Fis deprotonation leads to its better solubilization in water. Molecular modeling points out that Fis is not totally inserted into the inner cavity of -CD. The formation of the inclusion complex renders an environment that enhances intramolecular excited state proton transfer. The inclusion complex is formed preferentially via entry of the Fis phenyl group into -CD.