Ottavia Giuffrè - Academia.edu (original) (raw)

Papers by Ottavia Giuffrè

Journal of the Chemical Society, Jan 9, 2002

ABSTRACT This work reports a potentiometric, calorimetric and spectropolarimetric ultraviolet cir... more ABSTRACT This work reports a potentiometric, calorimetric and spectropolarimetric ultraviolet circular dichroism (UV/CD) study of the interaction of l-malic acid with alkaline metals or (poly)ammonium (methylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, spermine, tetraethylenepentamine and pentaethylenehexamine) cations. Stability data (logK, DeltaG(0)) were obtained potentiometrically for the l-malic acid with (poly)ammonium cations systems; calorimetric measurements (25 degrees C) made it possible to obtain DeltaH(0) and TDeltaS(0) values for the complexes formed in the systems under examination. logK values calculated (for the reaction: H(i)A(i+)+H(j)L((j-z))=ALH(r)((i+j-z)), with r=i+j) range between 0.8 and 4.6, i.e., the interactions are from weak to fairly strong while maximum stability for each system is given by the species with the highest z(anion)xz(cation) (z=charge) value. Enthalpy changes associated with reactions H(n)A(n+)+L(2-)=ALH(n)((n-2)) and H(n)A(n+)+HL(-)=ALH(n+1)((n-1)) are always positive and increase progressively with n. The same is valid for T DeltaS(0) values, which indicate that these species are entropically stabilized, as expected for electrostatic interactions. It was verified that the UV/CD signal depends on both ionic medium and ionic strength value; for comparison, we used the l-malic acid signal recorded in tetramethylammonium chloride as baseline background salt (as in potentiometry). UV/CD spectra were recorded for solutions containing both cationic and anionic species. When the cation was a protonated polyamine, CD spectra calculations were performed for most stable ion pairs: the results show remarkable differences in Deltaepsilon (dm(3) mol(-1) cm(-1)) values at 205 nm (which is the l-malate UV/CD lambda(max)) between the chiral ligand and its complex with a polyamine.

Chemosphere, 2018

h i g h l i g h t s Thermodynamic parameters for AsO 4 3-H þ , Mg 2þ , Ca 2þ , Sr 2þ interactions... more h i g h l i g h t s Thermodynamic parameters for AsO 4 3-H þ , Mg 2þ , Ca 2þ , Sr 2þ interactions are reported. For the first time, both ionic strength and temperature are taken into account. Speciation profiles of arsenate in some natural waters are simulated.

Journal of Molecular Liquids, Dec 1, 2022

New Journal of Chemistry, 2016

Replacing carboxylic with phosphonic groups in NTA significantly affects the sequestering ability... more Replacing carboxylic with phosphonic groups in NTA significantly affects the sequestering ability toward Hg2+, CH3Hg+, Sn2+ and (CH3)2Sn2+.

Social Science Research Network, 2023

Biophysical Chemistry, Mar 1, 2018

• Study of Al 3+-nucleotide interaction in NaCl at different ionic strengths • ΔH values of Al 3+... more • Study of Al 3+-nucleotide interaction in NaCl at different ionic strengths • ΔH values of Al 3+-ATP species determined by titration calorimetry • Stability and speciation model of Al 3+-ATP system confirmed by 1 H NMR titrations • Sequestering ability of different nucleotides towards Al 3+ at different pH values

Applied Organometallic Chemistry, 2006

Thermodynamic (potentiometric and calorimetric) and spectroscopic (1 H NMR, 119 Sn Mössbauer) stu... more Thermodynamic (potentiometric and calorimetric) and spectroscopic (1 H NMR, 119 Sn Mössbauer) studies were performed in aqueous solution in order to characterize the interaction of dimethyltin(IV) cation with citrate ligand. Six species {(CH 3) 2 Sn(cit) − ; [(CH 3) 2 Sn] 2 (cit) 2 2− ; (CH 3) 2 Sn(cit)H 0 ; (CH 3) 2 Sn(cit)OH 2− ; [(CH 3) 2 Sn] 2 (cit)OH 0 ; [(CH 3) 2 Sn] 2 (cit)(OH) 2 − } were found. All the species formed in this system are quite stable and formation percentages are fairly high. For example, at pH = 7.5 and C (CH 3) 2 Sn = C cit = 10 mmol l −1 , % for [(CH 3) 2 Sn] 2 (cit)(OH) 2 − and (CH 3) 2 Sn(cit)OH 2− species reaches 65%. Overall thermodynamic parameters obtained show that the main contribution to stability is entropic in nature. Thermodynamic parameters were discussed in comparison with a simple tricarboxylate ligand (1,2,3-propanetricarboxylate). Two empirical relationships were derived from thermodynamic formation parameters. Spectroscopic results fully confirm the speciation model defined potentiometrically and show the mononuclear species to have an eq-(CH 3) 2 Tbp structure with different arrangements around the metal, while for [(CH 3) 2 Sn] 2 (cit)(OH) 2 − there are two different Sn(IV) environments, namely trans-(CH 3) 2 octahedral and cis-(CH 3) 2 Tbp.

Journal of Molecular Liquids, Mar 1, 2011

The UV–VIS and the acid–base behaviour of three aminophenol ligands (m-aminophenol, 4-amino-2-hyd... more The UV–VIS and the acid–base behaviour of three aminophenol ligands (m-aminophenol, 4-amino-2-hydroxytoluene, 2-amino-5-ethylphenol) was studied by spectrophotometry at t=25°C and I=0.004mol L−1 in aqueous solution. The stability constants for their Zn2+ complexes were determined and compared by potentiometry at I=0.1mol L−1 in NaCl and UV–VIS spectrophotometry at I=0.004mol L−1. The results showed, in the pH range between 2 and 7,

Biophysical Chemistry, Apr 1, 2017

The interaction of Zn(II) with ampicillin [(2S,5R,6R)-6-([(2R)-2-amino-2-phenylacetyl]amino)-3,3-... more The interaction of Zn(II) with ampicillin [(2S,5R,6R)-6-([(2R)-2-amino-2-phenylacetyl]amino)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid] and amoxicillin [(2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid] in NaCl aqueous solution at different ionic strengths and at t = 25 °C was investigated by potentiometric, UV and 1 H NMR techniques. Fairly similar speciation models were obtained for the two systems. At I = 0.15 mol L-1 , two different sets of measurements, at low and high concentrations, were carried out. For the Zn 2+amoxicillin system, the Zn 2 L 2 (OH) 2 species was obtained in the set of measurements at high concentration. The spectrophotometric and 1 H NMR results thus obtained are fully consistent with the speciation models found from potentiometric investigations, confirming the formation as well as the relative stability of the complex species. In particular, NMR investigations allowed to ascertain the formation of the dimeric species, namely Zn 2 L 2 (OH) 2 obtained in the speciation model of the Zn 2+-Amox system at I = 0.15 mol L-1. The dependence of the stability constants on the ionic strength was modeled by means of the Debye-Hückel and SIT (Specific ion Interaction Theory) approaches, and the parameter that accounts for the variation of the stability constants with the ionic strength and the specific ion interaction parameters were determined for all the ionic species. The sequestering ability of the ligands toward Zn 2+ was evaluated by determining the pL 0.5 parameter, i.e. the-log of the total concentration of the ligand able to complex half of the metal ion fraction. The pL 0.5 parameter was determined at different ionic strengths. It resulted that

Applied Organometallic Chemistry, 2008

Quantitative data on the stability of mono-, di-and trimethyltin(IV)-carboxylate complexes (aceta... more Quantitative data on the stability of mono-, di-and trimethyltin(IV)-carboxylate complexes (acetate, malonate, succinate, malate, oxydiacetate, diethylenetrioxydiacetate, tricarballylate, citrate, butanetetracarboxylate and mellitate) are reported at t = 25 • C and I → 0 mol l −1. Several mononuclear, mixed proton, mixed hydroxo and polynuclear species are formed in these systems. As expected, the stability trend is mono-> di-> trimethyltin(IV) and mono < di < tri < tetra < hexa for the organotin moieties and carboxylate ligands investigated, respectively. Moreover, ligands containing, in addition to carboxylic,-O-and-OH groups show a significantly higher stability with respect to analogous ligands with the same number of carboxylic binding sites. The results obtained from all the systems investigated allowed us to formulate the following empirical predictive equation for correlation between complex stability and some simple structural parameters, log β = −6.0 + 1.63n carb + 1.4n OH + 4.58r + 3.9z cat where n carb and n OH are the number of carboxylic and alcoholic groups in the ligand, respectively, r is the stoichiometric coefficient of H + (positive) or OH − (negative) and z cat is the methyltin cation charge (CH 3) x Sn z+ (z + = 4 − x). Distribution diagrams for some representative systems are also reported and are discussed in the light of speciation studies in natural waters. A literature data comparison is made with carboxylate complexes of other metal ions with the same charge as the organotin cations investigated here.

Applied Organometallic Chemistry, 2005

Journal of Chemical & Engineering Data, Feb 25, 2004

ABSTRACT The acid−base properties of poly(allylamine) (MW = 15 kDa) were determined by potentiome... more ABSTRACT The acid−base properties of poly(allylamine) (MW = 15 kDa) were determined by potentiometry and calorimetry in aqueous solutions at t = 25 °C. Potentiometric measurements were carried out in a wide range of ionic strengths (0.1 ≤ I/mol·L-1 ≤ 5.0) in NaCl(aq) and LiCl(aq), while enthalpy changes for the protonation of poly(allylamine) were determined by calorimetry in the same ionic strength range but only in NaCl(aq). Analysis of the experimental data was carried out using two different models: the first based on a modified Henderson−Hasselbalch two parameter equation and the second on the three parameter equation proposed by Högfeldt. Protonation constants are given for both models and ionic media at t = 25 °C, while ΔG, ΔH, and TΔS values were determined using the three parameter model alone. The dependence on ionic strength of protonation constants was determined by the SIT model (Specific ion Interaction Theory), while the parameters for the dependence on ionic strength of ΔH and TΔS were determined by a simple empirical equation. Comparison is also made of the protonation constants of poly(allylamine) and some low molecular weight polyamines. Thermodynamic parameters for the protonation of poly(allylamine) are very close to those of low molecular weight polyamines, which are included for purposes of comparison.

Biophysical Chemistry, Mar 1, 2008

Thermodynamic and spectroscopic properties of the species formed by dimethyltin(IV) cation with L... more Thermodynamic and spectroscopic properties of the species formed by dimethyltin(IV) cation with L-cysteine (cys) were studied by potentiometric, calorimetric, UV and NMR investigations in aqueous solution. The resulting speciation model showed the formation of five complex species: (CH 3) 2 Sn(cys)H + , (CH 3) 2 Sn(cys) 0 , (CH 3) 2 Sn(cys)OH-, (CH 3) 2 Sn(cys) 2 H-, (CH 3) 2 Sn(cys) 2 2-. The stability and the formation percentages, for the mononuclear mixed species in particular, are very high, in a wide pH range. Thermodynamic parameters indicate that the enthalpy values are exothermic and the enthalpic contribution to the stability is higher than entropic one. Individual UV spectra of cys and dimethyltin(IV)-cys species were calculated. Spectroscopic results of UV and 1 H NMR investigations fully confirm the speciation model. The structures calculated from NMR investigations show that all the species have an eq-(CH 3) 2-tbp structure.

Fluid Phase Equilibria, Mar 1, 2018

Background As well known, α-amino acids (αAA) are fundamental for any form of life (Amend and Hel... more Background As well known, α-amino acids (αAA) are fundamental for any form of life (Amend and Helgeson 1997), being the building block of proteins and nutrients. Many fundamental information about biochemistry and nutrition of AA may be found in a recent dedicated

Journal of Chemical & Engineering Data, Oct 31, 2017

The interactions between Al3+ and ortho-phosphate (PO43–), pyro-phosphate (P2O74–, PP), tripolyph... more The interactions between Al3+ and ortho-phosphate (PO43–), pyro-phosphate (P2O74–, PP), tripolyphosphate (P3O105–, TPP) and hexa-metaphosphate (P6O186–, HMP) in aqueous solution have been studied. Formation constants, speciation models, and possible structures for the complexes formed are discussed on the basis of potentiometric, calorimetric, 31P–{1H} NMR, laser desorption mass spectrometric (LD MS) and MS/MS results. 31P–{1H} NMR experiments for Al3+–TPP system are in agreement with the speciation model drawn from analysis of potentiometric titration data, suggesting that TPP binds to Al3+ with two adjacent phosphate oxygen atoms, forming a six-membered ring. LD MS has provided identification and structural information for Al3+–PP, −TPP, and −HMP complexes which supports the reliability of speciation models proposed on the basis of the potentiometric data. Moreover, MS/MS spectra obtained from [ML]+ precursor ion show that the ion species involve linear HMP isomers and that two adjacent terminal phospha...

Journal of Chemical & Engineering Data, Oct 4, 2001

The protonation enthalpies of some polycarboxylate anions (malonate, citrate, 1,2,3-propanetricar... more The protonation enthalpies of some polycarboxylate anions (malonate, citrate, 1,2,3-propanetricarboxylate, and 1,2,3,4-butanetetracarboxylate) were studied calorimetrically at different ionic strengths, 1 e I e 5 mol kg-1 , in NaCl aqueous solutions. Some potentiometric measurements were also made at 15 and 55°C. Both calorimetric and potentiometric data (including previously reported data) were used to obtain complete sets of ∆G, ∆H, and T∆S values for the protonation of carboxylate anions. The dependence of ∆H on ionic strength was modeled by simple linear equations and using the Pitzer equations. Both ∆H values and their dependence on ionic strength follow regular trends as a function of the protonation steps, and general empirical relationships are proposed.

Biophysical Chemistry, May 1, 2017

Journal of Chemical & Engineering Data, May 12, 2011

ABSTRACT

Journal of Chemical & Engineering Data, Oct 12, 2005

... Concetta De Stefano, Ottavia Giuffrè,* and Silvio Sammartano. Dipartimento di Chimica Inorgan... more ... Concetta De Stefano, Ottavia Giuffrè,* and Silvio Sammartano. Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, I-98166 Messina (Vill. S. Agata), Italy. J. Chem. Eng. ...

Journal of Chemical & Engineering Data, May 6, 2019

A thermodynamic and spectroscopic study is reported on the interactions between inosine 5′-monoph... more A thermodynamic and spectroscopic study is reported on the interactions between inosine 5′-monophosphate (IMP), a ribonucleotide of hypoxanthine, and Ca 2+ and Mg 2+ , metal cations naturally occurring in biological fluids. Thermodynamic parameters concerning protonation and complex formation equilibria were determined. For both systems, the speciation model involved the formation of the MLH + and ML 0 species (M = Ca 2+ or Mg 2+), whose stability constants were determined in NaCl at different ionic strengths (I = 0.1−1 mol•kg −1) and temperatures (T = 288.15−318.15 K). In order to gain more information about the reliability of the speciation model obtained from potentiometric investigations and to get deeper insight on the interactions between ligand and metals, 1 H NMR spectroscopy was employed. Finally, the binding ability of IMP toward Ca 2+ and Mg 2+ was evaluated in terms of pL 0.5 (the ligand total concentration required to "sequester" the 50% of the metal cation). Examples of calculation in the conditions of some biological fluids are reported.