Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last... more Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last decades, significant attention for its cultivation has risen because it is the raw material for the production of hypoallergenic natural rubber. Guayule biomass contains also high amounts of resin, which is not normally exploited in any way. Among other sesquiterpenic esters, guayulins (i.e. the parteniol esters of cinnamic acid, guayulin A, or of anisic acid, guayulin B) are contained in resin. In addition, minor amounts of guayulin C and guayulin D are formed by degradation/oxidation of guayulins A and B, respectively. Guayulins likely act as cinnamate and p-anisate reservoirs for Guayule shrub, in addition, it has been postulated that they might have a key role in the chemical defense system of Guayule. Furthermore, it seems reasonable that guayulins can possess significant biological properties (e.g, antibacterial and anticancer activities), in close analogy with those shown by sesq...
Applications of Medicinal Bioinorganic Chemistry A Summer School on Medicinal Bioinorganic Chemis... more Applications of Medicinal Bioinorganic Chemistry A Summer School on Medicinal Bioinorganic Chemistry for Ph.D. students sponsored by University of Cagliari took place in September 2015. We are particularly obliged to a number of colleagues who responded enthusiastically to our invite to deliver their lectures, and mainly to be present for the entire duration of the school and fully available to assist the students, sharing their knowledge and experience. Twenty-five Ph.D. students from all over the world attended the School with extreme interest and profit. We are grateful to Prof. Atta-ur-Rahman, Editor of Current Medicinal Chemistry, who devoted this special issue to our School, and to all the authors for their contribution. Height reviews on topics of high novelty constitute this issue. They deal with different applications of Bioinorganic Chemistry that span from the effects of protein structure and function on different diseases, to the role of chelating agents for removing metal ions and toxic anions from the body. All these reviews, which take into account the medical implications of the treated topics, will be summarized in the following.
Tungsten or wolfram was regarded for many years as an enemy within the tin smelting and mining in... more Tungsten or wolfram was regarded for many years as an enemy within the tin smelting and mining industry, because it conferred impurity or dirtiness in tin mining. However, later it was considered an amazing metal for its strength and flexibility, together with its diamond like hardness and its melting point which is the highest of any metal. It was first believed to be relatively inert and an only slightly toxic metal, beginning in the year 2000, the risk exerted by tungsten alloys, its dusts and particulates to induce cancer and several other adverse effects in animals as well as humans has been highlighted from in vitro and in vivo experiments. Thus, it becomes necessary to take a careful look at all the most recent data reported in the scientific literature, covering the years 2001-2016. In fact, the findings indicate that much more attention should be devoted to thoroughly investigate the toxic effects of tungsten and the involved mechanisms of tungsten metal or tungsten metal i...
Depleted uranium (DU) is generally considered an emerging pollutant, first extensively introduced... more Depleted uranium (DU) is generally considered an emerging pollutant, first extensively introduced into environment in the early nineties in Iraq, during the military operation called “Desert Storm”. DU has been hypothesized to represent a hazardous element both for soldiers exposed as well as for the inhabitants of the polluted areas in the war zones. In this review, the possible consequences on human health of DU released in the environment are critically analyzed. In the first part, the chemical properties of DU and the principal civil and military uses are summarized. A concise analysis of the mechanisms underlying absorption, blood transport, tissue distribution and excretion of DU in the human body is the subject of the second part of this article. The following sections deal with pathological condition putatively associated with overexposure to DU. Developmental and birth defects, the Persian Gulf syndrome, and kidney diseases that have been associated to DU are the arguments ...
Background: Research into gold-based drugs for a range of human diseases has seen a revival in re... more Background: Research into gold-based drugs for a range of human diseases has seen a revival in recent years. This article reviews the most important applications of gold products in different fields of human pathology. Au(I) and Au(III) compounds have been re-introduced in clinical practice for targeting the cellular components involved in the onset and progression of viral and parasitic diseases, rheumatoid arthritis and cancer. Results: After some brief historical notes, this article takes into account the applications of gold compounds against Mycobacterium tuberculosis, and also in tuberculosis and in rheumatoid arthritis treatment. The use of gold containing drugs in the cure of cancer are then considered, with special emphasis to the use of nanoparticles and to the photo-thermal cancer therapy. The use of colloidal gold in diagnostics, introduced in the last decade is widely discussed. As a last point a survey on the adverse effects and on the toxicity of the various gold deri...
Gas chromatography analysis of major free mono-and disaccharides in milk: Method assessment, vali... more Gas chromatography analysis of major free mono-and disaccharides in milk: Method assessment, validation and application to real samples.
Chelation therapy plays a prominent role in the clinical treatment of metal intoxication. In this... more Chelation therapy plays a prominent role in the clinical treatment of metal intoxication. In this paper the principal causes of metal toxicity are exposed, and the chemical and biomedical requisites of a chelating agent are sketched. The chelating agents currently in use for scavenging toxic metal ions from humans belong to few categories: those characterized by coordinating mercapto groups, by oxygen groups, poliaminocarboxylic acids, and dithiocarbamates. Considering that the complex formation equilibria have been studied for less than 50% of chelators in use, some reflections on the utility of stability constants are presented, together with an evaluation of ligands under the stability profile. The competition between endogenous and toxic target metal ions for the same chelating agent is furthermore examined. A thorough examination of stability constant databases has allowed to select, for each toxic metal, the ligands distinguished by the best pMe values. Even though this selection does not consider the biomedical requisites of a chelating agent, it gives a clear picture both of the pMe values that can be attained, and of the most appropriate chelators for each metal ion.
Journal of agricultural and food chemistry, Jan 10, 2015
In this article we present a study of the variability of the concentration of 5-hydroxymethyl-2-f... more In this article we present a study of the variability of the concentration of 5-hydroxymethyl-2-furaldehyde (HMF) in natural RJ as a function of its storage temperature (-18 °C, 4 °C and 25 °C) and time (up to nine months after harvesting). For this work HMF is evaluated using an RP-HPLC method we previously assessed. While all RJ samples stored at 4 °C and -18 °C always showed levels of HMF under the limit of detection (0.13 mg Kg-1), samples kept at 25 °C showed an exponential increase in the concentration of HMF as a function of the storage time. This behavior and a number of desirable features of the analytical method used (easy to use in routine laboratories, availability of a complete validation protocol specifically developed for RJ, based on consolidated chemical knowledge) allow us to hypothetize the use of HMF as a possible, reliable freshness marker for RJ.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1985
ABSTRACT Carbon-13 chemical shifts of six 3-(para substituted benzoyl)-5-amino-1,2,4-oxadiazoles ... more ABSTRACT Carbon-13 chemical shifts of six 3-(para substituted benzoyl)-5-amino-1,2,4-oxadiazoles have been determined. Their relative SCS (substituent chemical shifts) are analysed by dual substituent parameter methods and the transmission of substituent effects is briefly discussed.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1991
A 'H and 13C NMR study of (phenylethynyl) (triphenylphosphine) gold(I) is presented. Contrary to ... more A 'H and 13C NMR study of (phenylethynyl) (triphenylphosphine) gold(I) is presented. Contrary to the solid state findings, the existence of Au.. . Au contacts in solution can be excluded on the basis of experimental results. The "C chemical shifts of various Au, Ag and Cu triphenylphosphine complexes and the corresponding SCS values are considered to rationalize the electronic behaviour of the ligand on complexation.
Azo-dyes, molecules characterised by the presence of the azo-group (-N‚N-), are widely used in te... more Azo-dyes, molecules characterised by the presence of the azo-group (-N‚N-), are widely used in textile, leather, rubber, plastic, and food industries. Water-soluble azo-dyes are greatly resistant to biodegradation, and are characterised by a high thermal and photo stability due to their complex structures. The release of these molecules into the environment is of crucial concern due to their toxic, mutagenic and carcinogenic characteristics. Biosorption has been demonstrated an effective method to remove pollutants from wastewaters thus solving ecological tasks, being a low cost process and the sorbent biodegradable. The main requirements of an efficient sorbent are thermal, chemical and mechanical stability, and rapid sorption. In this work, the ability of both row cork and the same sorbent entrapped in a biopolymeric gel of calcium alginate, on the removal of chrysoidine from aqueous solutions was examined. The influence on the sorption of pH, initial dye concentration, and particle size, as well as the efficiency of the entrapment, have been investigated. The maximum sorption was found for cork samples of fine particle size (FC), in both row and entrapped forms, at pH 7; conversely, at pH 4 the difference is significant (0.12 mmol/g for row cork and 0.20 mmol/g for entrapped cork), evoking a cooperation of alginate in binding the positively charged chrysoidine molecule.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1993
Ah&act-A 'H, "C and "P NMR study of adenosine-S&phosphate has been performed as a function of pH.... more Ah&act-A 'H, "C and "P NMR study of adenosine-S&phosphate has been performed as a function of pH. The examination of the chemical shifts allowed the proposal of an ionization scheme in which the third deprotonation takes place both on the adenine ring and on the phosphate group in a ratio of about 2: 1. Furthermore, an analysis of carbon relaxation times supports this mechanism of ionization and confirms that the adenine ring binds the proton both on the NH, group and the N, nitrogen atom.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1994
Potentiometric and spectrophotometric results obtained for the Cu(II)-Aztreonam system give a cle... more Potentiometric and spectrophotometric results obtained for the Cu(II)-Aztreonam system give a clear indication of the chelating properties of this antibiotic toward the Cu 2+ ion, coordinated already at pHi2. Only one single complex of 1 : 1 stoichiometry is formed. Measurements of m3C relaxation rates allow us to attribute a coordination scheme via the carboxylic and aminic groups.
The obvious advantages of MRI-based cell imaging are the high resolution and anatomic details for... more The obvious advantages of MRI-based cell imaging are the high resolution and anatomic details for soft tissue as well as the ability to generate contrast based on a variety of physiological parameters (1, 2). Bio-functionalization of nanoparticles allows visualization of specific cell types by receptor specific uptake or binding, making MRI a powerful tool for molecular imaging (1, 3, 4). However, a number of issues must be carefully considered for non-invasive in vivo cell imaging in general and for MRI-based cell tracking in particular. Apart from issues related to the relatively low sensitivity of MRI, specificity issues, the stability of MRI contrast agents or the generation of unambiguous contrast, the prevention of toxicity and alterations of cellular processes by the contrast agent and no or minimal influence on the physiological behavior of the cells are of highest importance.
The ionization constants in aqueous solutions of meso-and DL-dimercaptosuccinic acid and of monom... more The ionization constants in aqueous solutions of meso-and DL-dimercaptosuccinic acid and of monomethyl and dimethyl meso-succinates were carefully determined by potentiometric and spectrophotometric methods as a result of the increasing interest in these molecules as heavy metal chelators. In order to explain the influence of various substituents on ionization and 13C NMR properties, the study was extended to the related oxygen derivatives of succinic acid and to simpler ethanoic derivatives, With the Swain-Lupton dual substituent treatment it was possible to clarify the influence of substituents on both spectral and equilibrium parameters. The differences in pK due to conformation are also discussed.
The boric acid-pyrogallol system has been studied in aqueous solution by means of potentiometric ... more The boric acid-pyrogallol system has been studied in aqueous solution by means of potentiometric methods. Evidence is given for two adducts of 1: 1 and 1: 2 stoichiometry. An analysis of 13C NMR spectra of the 1: 2 adduct is presented.
ABSTRACT Spectrophotometric studies of dichloromethane solutions containing iodine and some Cr(S2... more ABSTRACT Spectrophotometric studies of dichloromethane solutions containing iodine and some Cr(S2CNR2)3 complexes (where R2NCS−2 are: OC4H8NCS−2 = modtc; (C2H5)2NCS−2 = Et2dtc; (C6H5CH2)2NCS−2 = Bz2dtc) have shown the formation of 1:1 adducts whose spectral features were studied and which suggested that charge-transfer interaction involving iodine and a sulphur atom of a coordinated dithiocarbamato ligand occurred.A new BASIC non-linear least-squares program which performs an optimization of the absorbance data taken at several wavelengths was devised to evaluate reliable formation constants.The thermodynamic parameters have been calculated and compared with those obtained in the same conditions as above by a reinvestigation of the known 1:1 complex formation of iodine with the corresponding tetraalkylthiuram-disulphides, where the donor site is also the sulphur atom of the thiocarbonyl group. The −ΔH° values related to the Cr(dtc)3 · I2 complexes are about 2 kcal lower than those of thiuram disulphides, showing a lowering of the donor strength of the thiocarbonyl sulphur as a consequence of the coordination to the metal.
The complex formation equilibria of aspergillic acid with iron(III) were studied by potentiometri... more The complex formation equilibria of aspergillic acid with iron(III) were studied by potentiometric and spectrophotometric methods. The ligand was prepared by a biosynthetic route and its purity checked by MS and 1 H NMR spectroscopies. Some structural features of the ligand are discussed on the basis of NMR results. The iron(III) coordination model is compared with those of two other cyclic hydroxamates, 1-hydroxy-2-pyridinone and 1,4-dihydroxy-2-pyridinone, and its features are discussed on the basis of quantum chemical calculations.
... AN H NMR AND POTENTIOMETRIC STUDY OF THE INTERACTION BETWEEN PLATINUM(ll) AND CIMETLD1NE VALE... more ... AN H NMR AND POTENTIOMETRIC STUDY OF THE INTERACTION BETWEEN PLATINUM(ll) AND CIMETLD1NE VALERIA NURCHI, FRANCO CRISTIANI and ... 9. A. Sancho, J. Borras, L. Soto Tuero, C. Esteban Calderon, C. Martinez Ripol and M. Garcia Blanco, ...
Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last... more Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last decades, significant attention for its cultivation has risen because it is the raw material for the production of hypoallergenic natural rubber. Guayule biomass contains also high amounts of resin, which is not normally exploited in any way. Among other sesquiterpenic esters, guayulins (i.e. the parteniol esters of cinnamic acid, guayulin A, or of anisic acid, guayulin B) are contained in resin. In addition, minor amounts of guayulin C and guayulin D are formed by degradation/oxidation of guayulins A and B, respectively. Guayulins likely act as cinnamate and p-anisate reservoirs for Guayule shrub, in addition, it has been postulated that they might have a key role in the chemical defense system of Guayule. Furthermore, it seems reasonable that guayulins can possess significant biological properties (e.g, antibacterial and anticancer activities), in close analogy with those shown by sesq...
Applications of Medicinal Bioinorganic Chemistry A Summer School on Medicinal Bioinorganic Chemis... more Applications of Medicinal Bioinorganic Chemistry A Summer School on Medicinal Bioinorganic Chemistry for Ph.D. students sponsored by University of Cagliari took place in September 2015. We are particularly obliged to a number of colleagues who responded enthusiastically to our invite to deliver their lectures, and mainly to be present for the entire duration of the school and fully available to assist the students, sharing their knowledge and experience. Twenty-five Ph.D. students from all over the world attended the School with extreme interest and profit. We are grateful to Prof. Atta-ur-Rahman, Editor of Current Medicinal Chemistry, who devoted this special issue to our School, and to all the authors for their contribution. Height reviews on topics of high novelty constitute this issue. They deal with different applications of Bioinorganic Chemistry that span from the effects of protein structure and function on different diseases, to the role of chelating agents for removing metal ions and toxic anions from the body. All these reviews, which take into account the medical implications of the treated topics, will be summarized in the following.
Tungsten or wolfram was regarded for many years as an enemy within the tin smelting and mining in... more Tungsten or wolfram was regarded for many years as an enemy within the tin smelting and mining industry, because it conferred impurity or dirtiness in tin mining. However, later it was considered an amazing metal for its strength and flexibility, together with its diamond like hardness and its melting point which is the highest of any metal. It was first believed to be relatively inert and an only slightly toxic metal, beginning in the year 2000, the risk exerted by tungsten alloys, its dusts and particulates to induce cancer and several other adverse effects in animals as well as humans has been highlighted from in vitro and in vivo experiments. Thus, it becomes necessary to take a careful look at all the most recent data reported in the scientific literature, covering the years 2001-2016. In fact, the findings indicate that much more attention should be devoted to thoroughly investigate the toxic effects of tungsten and the involved mechanisms of tungsten metal or tungsten metal i...
Depleted uranium (DU) is generally considered an emerging pollutant, first extensively introduced... more Depleted uranium (DU) is generally considered an emerging pollutant, first extensively introduced into environment in the early nineties in Iraq, during the military operation called “Desert Storm”. DU has been hypothesized to represent a hazardous element both for soldiers exposed as well as for the inhabitants of the polluted areas in the war zones. In this review, the possible consequences on human health of DU released in the environment are critically analyzed. In the first part, the chemical properties of DU and the principal civil and military uses are summarized. A concise analysis of the mechanisms underlying absorption, blood transport, tissue distribution and excretion of DU in the human body is the subject of the second part of this article. The following sections deal with pathological condition putatively associated with overexposure to DU. Developmental and birth defects, the Persian Gulf syndrome, and kidney diseases that have been associated to DU are the arguments ...
Background: Research into gold-based drugs for a range of human diseases has seen a revival in re... more Background: Research into gold-based drugs for a range of human diseases has seen a revival in recent years. This article reviews the most important applications of gold products in different fields of human pathology. Au(I) and Au(III) compounds have been re-introduced in clinical practice for targeting the cellular components involved in the onset and progression of viral and parasitic diseases, rheumatoid arthritis and cancer. Results: After some brief historical notes, this article takes into account the applications of gold compounds against Mycobacterium tuberculosis, and also in tuberculosis and in rheumatoid arthritis treatment. The use of gold containing drugs in the cure of cancer are then considered, with special emphasis to the use of nanoparticles and to the photo-thermal cancer therapy. The use of colloidal gold in diagnostics, introduced in the last decade is widely discussed. As a last point a survey on the adverse effects and on the toxicity of the various gold deri...
Gas chromatography analysis of major free mono-and disaccharides in milk: Method assessment, vali... more Gas chromatography analysis of major free mono-and disaccharides in milk: Method assessment, validation and application to real samples.
Chelation therapy plays a prominent role in the clinical treatment of metal intoxication. In this... more Chelation therapy plays a prominent role in the clinical treatment of metal intoxication. In this paper the principal causes of metal toxicity are exposed, and the chemical and biomedical requisites of a chelating agent are sketched. The chelating agents currently in use for scavenging toxic metal ions from humans belong to few categories: those characterized by coordinating mercapto groups, by oxygen groups, poliaminocarboxylic acids, and dithiocarbamates. Considering that the complex formation equilibria have been studied for less than 50% of chelators in use, some reflections on the utility of stability constants are presented, together with an evaluation of ligands under the stability profile. The competition between endogenous and toxic target metal ions for the same chelating agent is furthermore examined. A thorough examination of stability constant databases has allowed to select, for each toxic metal, the ligands distinguished by the best pMe values. Even though this selection does not consider the biomedical requisites of a chelating agent, it gives a clear picture both of the pMe values that can be attained, and of the most appropriate chelators for each metal ion.
Journal of agricultural and food chemistry, Jan 10, 2015
In this article we present a study of the variability of the concentration of 5-hydroxymethyl-2-f... more In this article we present a study of the variability of the concentration of 5-hydroxymethyl-2-furaldehyde (HMF) in natural RJ as a function of its storage temperature (-18 °C, 4 °C and 25 °C) and time (up to nine months after harvesting). For this work HMF is evaluated using an RP-HPLC method we previously assessed. While all RJ samples stored at 4 °C and -18 °C always showed levels of HMF under the limit of detection (0.13 mg Kg-1), samples kept at 25 °C showed an exponential increase in the concentration of HMF as a function of the storage time. This behavior and a number of desirable features of the analytical method used (easy to use in routine laboratories, availability of a complete validation protocol specifically developed for RJ, based on consolidated chemical knowledge) allow us to hypothetize the use of HMF as a possible, reliable freshness marker for RJ.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1985
ABSTRACT Carbon-13 chemical shifts of six 3-(para substituted benzoyl)-5-amino-1,2,4-oxadiazoles ... more ABSTRACT Carbon-13 chemical shifts of six 3-(para substituted benzoyl)-5-amino-1,2,4-oxadiazoles have been determined. Their relative SCS (substituent chemical shifts) are analysed by dual substituent parameter methods and the transmission of substituent effects is briefly discussed.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1991
A 'H and 13C NMR study of (phenylethynyl) (triphenylphosphine) gold(I) is presented. Contrary to ... more A 'H and 13C NMR study of (phenylethynyl) (triphenylphosphine) gold(I) is presented. Contrary to the solid state findings, the existence of Au.. . Au contacts in solution can be excluded on the basis of experimental results. The "C chemical shifts of various Au, Ag and Cu triphenylphosphine complexes and the corresponding SCS values are considered to rationalize the electronic behaviour of the ligand on complexation.
Azo-dyes, molecules characterised by the presence of the azo-group (-N‚N-), are widely used in te... more Azo-dyes, molecules characterised by the presence of the azo-group (-N‚N-), are widely used in textile, leather, rubber, plastic, and food industries. Water-soluble azo-dyes are greatly resistant to biodegradation, and are characterised by a high thermal and photo stability due to their complex structures. The release of these molecules into the environment is of crucial concern due to their toxic, mutagenic and carcinogenic characteristics. Biosorption has been demonstrated an effective method to remove pollutants from wastewaters thus solving ecological tasks, being a low cost process and the sorbent biodegradable. The main requirements of an efficient sorbent are thermal, chemical and mechanical stability, and rapid sorption. In this work, the ability of both row cork and the same sorbent entrapped in a biopolymeric gel of calcium alginate, on the removal of chrysoidine from aqueous solutions was examined. The influence on the sorption of pH, initial dye concentration, and particle size, as well as the efficiency of the entrapment, have been investigated. The maximum sorption was found for cork samples of fine particle size (FC), in both row and entrapped forms, at pH 7; conversely, at pH 4 the difference is significant (0.12 mmol/g for row cork and 0.20 mmol/g for entrapped cork), evoking a cooperation of alginate in binding the positively charged chrysoidine molecule.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1993
Ah&act-A 'H, "C and "P NMR study of adenosine-S&phosphate has been performed as a function of pH.... more Ah&act-A 'H, "C and "P NMR study of adenosine-S&phosphate has been performed as a function of pH. The examination of the chemical shifts allowed the proposal of an ionization scheme in which the third deprotonation takes place both on the adenine ring and on the phosphate group in a ratio of about 2: 1. Furthermore, an analysis of carbon relaxation times supports this mechanism of ionization and confirms that the adenine ring binds the proton both on the NH, group and the N, nitrogen atom.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1994
Potentiometric and spectrophotometric results obtained for the Cu(II)-Aztreonam system give a cle... more Potentiometric and spectrophotometric results obtained for the Cu(II)-Aztreonam system give a clear indication of the chelating properties of this antibiotic toward the Cu 2+ ion, coordinated already at pHi2. Only one single complex of 1 : 1 stoichiometry is formed. Measurements of m3C relaxation rates allow us to attribute a coordination scheme via the carboxylic and aminic groups.
The obvious advantages of MRI-based cell imaging are the high resolution and anatomic details for... more The obvious advantages of MRI-based cell imaging are the high resolution and anatomic details for soft tissue as well as the ability to generate contrast based on a variety of physiological parameters (1, 2). Bio-functionalization of nanoparticles allows visualization of specific cell types by receptor specific uptake or binding, making MRI a powerful tool for molecular imaging (1, 3, 4). However, a number of issues must be carefully considered for non-invasive in vivo cell imaging in general and for MRI-based cell tracking in particular. Apart from issues related to the relatively low sensitivity of MRI, specificity issues, the stability of MRI contrast agents or the generation of unambiguous contrast, the prevention of toxicity and alterations of cellular processes by the contrast agent and no or minimal influence on the physiological behavior of the cells are of highest importance.
The ionization constants in aqueous solutions of meso-and DL-dimercaptosuccinic acid and of monom... more The ionization constants in aqueous solutions of meso-and DL-dimercaptosuccinic acid and of monomethyl and dimethyl meso-succinates were carefully determined by potentiometric and spectrophotometric methods as a result of the increasing interest in these molecules as heavy metal chelators. In order to explain the influence of various substituents on ionization and 13C NMR properties, the study was extended to the related oxygen derivatives of succinic acid and to simpler ethanoic derivatives, With the Swain-Lupton dual substituent treatment it was possible to clarify the influence of substituents on both spectral and equilibrium parameters. The differences in pK due to conformation are also discussed.
The boric acid-pyrogallol system has been studied in aqueous solution by means of potentiometric ... more The boric acid-pyrogallol system has been studied in aqueous solution by means of potentiometric methods. Evidence is given for two adducts of 1: 1 and 1: 2 stoichiometry. An analysis of 13C NMR spectra of the 1: 2 adduct is presented.
ABSTRACT Spectrophotometric studies of dichloromethane solutions containing iodine and some Cr(S2... more ABSTRACT Spectrophotometric studies of dichloromethane solutions containing iodine and some Cr(S2CNR2)3 complexes (where R2NCS−2 are: OC4H8NCS−2 = modtc; (C2H5)2NCS−2 = Et2dtc; (C6H5CH2)2NCS−2 = Bz2dtc) have shown the formation of 1:1 adducts whose spectral features were studied and which suggested that charge-transfer interaction involving iodine and a sulphur atom of a coordinated dithiocarbamato ligand occurred.A new BASIC non-linear least-squares program which performs an optimization of the absorbance data taken at several wavelengths was devised to evaluate reliable formation constants.The thermodynamic parameters have been calculated and compared with those obtained in the same conditions as above by a reinvestigation of the known 1:1 complex formation of iodine with the corresponding tetraalkylthiuram-disulphides, where the donor site is also the sulphur atom of the thiocarbonyl group. The −ΔH° values related to the Cr(dtc)3 · I2 complexes are about 2 kcal lower than those of thiuram disulphides, showing a lowering of the donor strength of the thiocarbonyl sulphur as a consequence of the coordination to the metal.
The complex formation equilibria of aspergillic acid with iron(III) were studied by potentiometri... more The complex formation equilibria of aspergillic acid with iron(III) were studied by potentiometric and spectrophotometric methods. The ligand was prepared by a biosynthetic route and its purity checked by MS and 1 H NMR spectroscopies. Some structural features of the ligand are discussed on the basis of NMR results. The iron(III) coordination model is compared with those of two other cyclic hydroxamates, 1-hydroxy-2-pyridinone and 1,4-dihydroxy-2-pyridinone, and its features are discussed on the basis of quantum chemical calculations.
... AN H NMR AND POTENTIOMETRIC STUDY OF THE INTERACTION BETWEEN PLATINUM(ll) AND CIMETLD1NE VALE... more ... AN H NMR AND POTENTIOMETRIC STUDY OF THE INTERACTION BETWEEN PLATINUM(ll) AND CIMETLD1NE VALERIA NURCHI, FRANCO CRISTIANI and ... 9. A. Sancho, J. Borras, L. Soto Tuero, C. Esteban Calderon, C. Martinez Ripol and M. Garcia Blanco, ...
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