Simultaneous determination of zinc and copper(II) with 1-(2-pyridylazo)2-naphthol in micellar media by spectrophotometric H-point standard addition method

The H-point standard addition method (HPSAM) was applied to handling spectrophotometric data for simultaneous determination of Zn²⁺ and Cu²⁺ or selective determination of Zn²⁺ in the presence of Cu²⁺. The ligand 1-(2-pyridylazo)2-naphthol (PAN) and its metal complexes (Zn-PAN and Cu(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. The method is based on the difference in absorbance of formed complexes between Zn²⁺ and PAN, at two different wavelengths at pH = 9.2. The formation of both the complexes was complete within five minutes. Zn²⁺ can be determined in the range of 0.2–25 μg/mL with satisfactory accuracy and precision in the presence of excess of Cu²⁺ and most other metal ions. Interference effects of common anions and cations were studied. Under working conditions, the proposed method was successfully applied to the simultaneous determination of Zn²⁺ and Cu²⁺ in several real and synthetic mixtures with different concentration ratio of Zn²⁺ and Cu²⁺. The text was submitted by the authors in English.     

Study of Host-Guest Complexation of Alkaline Earth Metal Ion,Aluminum Ion and Transition Metal Ions with Crown Ethers by Fast Atom Bombardment Mass Spectrometry

Complexations of crown ethers with alkali metal ions have been investigated extensively by FAB mass spectrometry over the past decade, but very little attention has been paid to reactions of crown ethers with other classes of metal ions such as alkaline earth metal ions, transition metal ions and aluminum ions. Although fast atom bombardment ionization mass spectrometry has proven to be a rapid and convenient method to determine the binding interactions of crown ethers with metal ions, problems in reliabilities for quantitative measurements of” binding strength for the host-guest complexes have been described in the literature. Thus, in this paper, applications of FAB/MS for investigating the complexation of crown ethers with various classes of metal ions is discussed. Extensive fragmentations for neutral losses such as C₂H₄O or C₂H₄ molecules from the host-guest complexes could be observed. The reason is attributed to the energetic bombardment processes of FAB occuring in the formation of these complexes. Complexes of cyclen with metal ions also show neutral losses of C₂H₄NH molecules leading to fragment ions. Transition metal ions usually form (Crown + MCl)⁺ type of ions, alkaline earth metal ions can form both (Crown + MCl)⁺ and (Crown + MOH)⁺ type of ions. But for aluminum ions, only (Crown + Al(OH)₂)⁺ type of ions could he observed.     

Determination of the complex formation constants for some water-soluble polymers with trivalent metal ions by differential pulse polarography

The formation of metal complexes between water-soluble polymers, poly(vinyl alcohol) [PVA], poly(N-vinylpyrrolidone) [PVP], poly(acrylamide) [PAAm] and poly(ethylene oxide) [PEO] with trivalent metal ions, Fe³⁺, Cr³⁺, and V³⁺ were studied by using differential pulse polarography (DPP). The general experimental observation is the shift of totally reversible reduction peaks (M³⁺+Hg+e^–M²⁺+Hg) towards more negative potentials when the complexing water-soluble polymers are added to the solution of trivalent metal ions. The negative shift in potential permitted the determination of complex formation constants (K_f) between trivalent metal ions and water soluble polymers. The complex formation constants for Fe³⁺, Cr³⁺, and V³⁺ ions with these polymers increased in the order of V³⁺>Cr³⁺>Fe³⁺.     

Aminodiacetic water-soluble polymer-metal ion interactions

The retention properties for metal ions, the maximum retention capacity, the antibacterial and mutagenic activity of water-soluble metal ion complexes from water-soluble poly[2-hydroxy-(3-methacryloyloxypropyl)aminodiacetic acid] P(HMPADA) were studied. HMPADA was synthesized by radical polymerization in aqueous solution. The water-soluble polymer (WSP) P(HMPADA), containing ester, hydroxy, tertiary amine, and two carboxylic acid groups in every monomeric unit was investigated as polychelatogen in view of its potential metal ion binding properties using the liquid-phase polymer based retention (LPR) technique under different experimental conditions. The water-soluble complexes were investigated as biocides. Metal ions investigated at pH 3, 5, and 7 were: Ag⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Al³⁺, Cr³⁺, and Fe³⁺. Depending on pH, P(HMPADA) showed a different interaction affinity, where the highest interaction occurred at pH 7. Polymer-metal ion interaction showed the following affinity order: tri-valent >di-valent >mono-valent ion. Maximum retention capacity (MRC) ranged between 17.2 and 342.2 mg metal ion/g polymer for Cu²⁺ and Ag⁺, respectively. FT-IR showed a variation in νCO, νΟ−CO, νOH absorption signals, and Far-IR showed new signals corresponding to metal-O and metal-N interaction, indicating a participation of carboxylic acid, amine, and hydroxy groups of polymer-metal ion complexes. Antibacterial activity of Ag⁺, Cu²⁺, Zn²⁺, and Cd²⁺ complexes were studied. These complexes presented a higher biocide activity against Staphylococcus aureus (Gram-positive) than for Escherichia coli (Gram-negative) with a lowest minimum inhibitory concentration (MIC) of 4 mg/mL for polymer-Cd²⁺ complex. Scanning electron microscopy (SEM) showed the interaction between polymer-metal ion complexes and bacteria surface. All samples showed low genotoxic activity.     

Synthesis and properties of potassium salts of per-<Emphasis Type="Italic">O</Emphasis>-carboxymethyl-calix[4]pyrogallols and their complexes with Cu<Superscript>2+</Superscript>, Fe<Superscript>3+</Superscript>, and La<Superscript>3+</Superscript>

Synthesis of water-soluble potassium salts of carboxymethyl derivatives of calix[4]pyrogallols and dodeca(carboxylatomethyl)tetramethylcalix[4]pyrogallol (L) complexes with transition metal ions (Cu²⁺, Fe³⁺, La³⁺) is described. Their structures in the solid state and in solution were characterized by NMR spectroscopy, ESR, and IR spectroscopy. Calix[4]pyrogallol dodecacarboxylates exist in the rccc-configuration. Calix[4]pyrogallol with methyl substituents at the lower rim in a wide range concentrations exists in water predominantly in the dimeric form. The obtained polynuclear transition metal complexes possess less symmetric structure than potassium salt of calix[4]pyrogallol (K₁₂L). All studied complexes contain water molecules bound by rather strong hydrogen bonds. At room temperature the Fe₄L complex is characterized by the environment of the Fe³⁺ ions close to octahedral. The absence of signals in the ESR spectrum of the Cu₆L complex indicates the strong antiferromagnetic interaction Cu²⁺-Cu²⁺.     

Interaction energy‐based drug–receptor interaction study of metal–bicyclam complexes

Bicyclams inhibit HIV replication by binding to the CXCR4 chemokine receptor, which is the main coreceptor for gp120 used by X4, T‐tropic strains of HIV for membrane fusion and cell entry. Bicyclam AMD3100 mainly interacts with the aspartic acid residues namely Asp171 and Asp262, which are located at the extracellular ends in the CXCR4 coreceptor. Incorporation of some metal ions by the macrocyclic rings of bicyclam enhances its binding affinity to the CXCR4 receptor and enhances their anti‐HIV activity because the acetate can make a strong coordination bond to the metal and one weaker hydrogen bond to nitrogen in the cyclam ring. The interaction energy (E_int) between 150 metal–bicyclam complexes and aspartic acid has been evaluated. The metal–bicyclam complexes are obtained by the incorporation of six metal ions namely Fe³⁺, Co³⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Pd²⁺ in 25 well‐known bicyclams including AMD3100. In most of the cases, Fe and Co–bicyclam complexes interact best with aspartic acid. The anti‐HIV activity of metal–bicyclam complexes can be predicted on the basis of interaction energy before the synthesis of the metal–bicyclam complex. On the basis of interaction energy, the anti‐HIV activity of bicyclam complexes can be predicted in advance to their synthesis. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Spectrophotometric study of complexation of dibenzopyridino-18-crown-6 with some transition and post-transition metal ions in DMSO solution using murexide as a metallochromic ligand

The complexation reaction of dibenzopyridino-18-crown-6 (DBPY 18C6) with Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Hg²⁺, and Ag⁺ have been studied in DMSO at 25°C by the spectrophotometric method. Murexide was used as a competitive colored ligand. The stoichiometry of metal ion-murexide and metal ions with DBPY18C6 complexes were estimated by mole ratio and continuous variation methods and emphasized by the KINFIT program. The stoichiometry of all the complexes was found to be 1: 1 (metal ion/ligand). The order of stability constants for the obtained metal ion-murexide complexes (1: 1) varies in the order Cu²⁺ > Cd²⁺ > Co²⁺ ∼ Pb²⁺ > Zn²⁺ > Ag⁺ > Hg²⁺. This trend shows that the transition metal ions clearly obey the Irving-Williams role. For the post-transition metal ions, the ionic radius and soft-hard behavior was the major affects in varying of this order. The dibenzopyridino-18-crown-6 complexes with the used metal ions vary as Ag⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺ > Hg²⁺ > Zn²⁺ > Co²⁺. The article is published in the original.     

Metal complexes with macrocyclic ligands. Part XXII. Synthesis two of bis-tetraaza-macrocycles and study of the structures,electrochemistry, VIS and EPR spectra of their binuclear Cu2+ and Ni2+ complexes

The two bis-macrocycles 4 and 5 in which the tetraaza units are separated by a chain of different length, have been synthesized using 1,4,7-tritosyl-1,4,7,11-tetraazacyclotetradecane as starting compound and bifunctional alkylating agents. The bis-macrocycles give binuclear complexes with Ni²⁺ and Cu²⁺, the properties of which have been studied to obtain information about the interaction of the two subunits as a function of the distance. The VIS spectra of the Ni²⁺ and Cu²⁺ complexes indicate that both metal ions are in a square-planar geometry as expected from the results of the analogous complexes with 1,4,7,11-tetraazacyclotetradecane 7 . Cyclic voltammetry and differential pulse polarography of the binuclear Ni²⁺complexes in CH₃CN show a single two-electron step for ligand 5 , whereas two distinct one-electron redox processes can be observed for ligand 4 , indicating that the two metal ions interact with each other when the chain length is shorter. Similarly, the EPR studies of frozen solutions of the binuclear Cu²⁺ complexes clearly show that a magnetic dipolar interaction between the two paramagnetic centers exists, and that the strength of it depends upon the length of the bridge. Finally, from the X-ray structures of the binuclear Ni²⁺ complexes with 4 and 5 , it is seen that the two rings are kept apart as far as possible, the distances between the two metal ions determined in the solid correlate well with the observations in solution.     

Control of a photoswitching chelator by metal ions: DFT,NBO, and QTAIM analysis

Ability of aroylhydrazones to change conformation upon interaction with light makes them promising candidates for molecular switches. Isomerization can be controlled through complexation with selected metal ions which bind with different affinity. N′‐[1‐(2‐hydroxyphenyl)ethyliden]iso‐nicotinoylhydrazide (HAPI) is an example of a dual‐wavelenght photoswitching molecule, whose complexation with metal ions was recently experimentally investigated (Franks et al. J. Inorg. Chem. 2014, 53, 1397). In this contribution, complexes between HAPI and K⁺, Ca²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Cu⁺, Cu²⁺, and Zn²⁺ ions were investigated using Density Functional Theory, Natural Bond Order analysis, and Quantum Theory of Atoms in Molecules. The most important parameters that determine complex stability are found to be ion radius and charge transferred from ligands to the ion: smaller ion radii and larger CT values characterize formation of more stable complexes. Our results explain experimentally observed effect of different metal ions on photoisomerization through determination of metal ion affinity (MIA): photoisomerization is inhibited if MIA exceeds 100 kcal/mol; for MIA between 50 and 100 kcal/mol excess of metal ions prevents isomerization, whereas in case of MIA below 50 kcal/mol metal ions have no influence on light–HAPI interaction. © 2015 Wiley Periodicals, Inc.     

Metal Complexes of Pentadentate Macrocyclic Ligands Containing Oxygen and Nitrogen as Donor Atoms

Four macrocyclic ligands have been synthesized: 1-oxa-4,7,10,13-tetraazacyclopentadecane ( 1 ), 1,4-dioxa-7,10,13-triazacyclopentadecane ( 2 ), 1,4-dioxa-7,11,14-triazacyclohexadecane ( 3 ), 1,4-dioxa-7,11,15-triazacycloheptadecane ( 4 ), one of them 3 , for the first time. The protonation constants of the ligands and the stability constants of the complexes formed by the four ligands with some divalent first-series transition-metal ions, Cd²⁺ and Pb²⁺, were determined by potentiometric methods, in aqueous solution, at 25° and I = 0.10M (KNO₃). The sequence of protonation of ligand 1 was studied by ¹H-NMR spectroscopy. The Irving-Williams' order of stability is obeyed for the complexes of all the ligands, and the metal complexes of 1 present the higher values of stability. A drop in the stability of all the metal complexes studied is observed when the metal complexes of 1 are compared with the corresponding complexes of 2 . The effect of the increase of the ring size of the macrocycle can be observed for metal complexes of the series of ligands 2 4 , where, in spite of the slight increase of the overall basicity of the ligands (20.28, 22.25, and 24.96 for 2, 3 , and 4 respectively), small differences in stability are found for the corresponding complexes of 2 and 3 , but a significant drop occurs for all the metal complexes formed with the 17-membered ligand, specially for the larger metal ions like Mn²⁺ and Pb²⁺.     

Electron capture dissociation and collision-induced dissociation of metal ion (Ag+, Cu2+, Zn2+, Fe2+, and Fe3+) complexes of polyamidoamine (PAMAM) dendrimers

The electron capture dissociation (ECD) and collision-induced dissociation (CID) of complexes of polyamidoamine (PAMAM) dendrimers with metal ions Ag⁺, Cu²⁺, Zn²⁺, Fe²⁺, and Fe³⁺ were determined by Fourier transform ion cyclotron resonance mass spectrometry. Complexes were of the form [PD + M + mH]⁵⁺ where PD = generation two PAMAM dendrimer with amidoethanol surface groups, M = metal ion, m = 2−4. Complementary information regarding the site and coordination chemistry of the metal ions can be obtained from the two techniques. The results suggest that complexes of Fe³⁺ and Cu²⁺ are coordinated via both core tertiary amines, whereas coordination of Ag⁺ involves a single core tertiary amine. The Zn²⁺ and Fe²⁺ complexes do not appear to involve coordination by the dendrimer core.     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Synthesis,spectroscopic characterization and biological evaluation of a novel chemosensor with different metal ions

A novel chemosensor, namely 3‐(4‐chlorophenyl)‐1‐(pyridin‐2‐yl)prop‐2‐en‐1‐one, CPPEO, and its metal complexes have been synthesized and characterized by using sets of chemical and spectroscopic techniques, such as elemental analysis, mass, Fourier transform‐infrared and UV–Vis spectral analysis. The thermal properties of the metal complexes have been investigated by thermogravimetric techniques. The decomposition mechanism of the titled complexes was suggested. The results showed that the Co²⁺ and Mn²⁺ complexes have an octahedral geometry, while Zn²⁺ and Cd²⁺ complexes have tetrahedral geometry. The kinetic and thermodynamic parameters of the thermal decomposition stages have been evaluated using the Coats–Redfern method. The optical sensing response of the investigated chemosensor to the different metal ions was investigated. It responds well to the tested metal ions as reflected from the significant change in both absorption and emission spectra upon adding different concentrations of the metal salts, confirming the intramolecular charge transfer of the chemosensor upon effective coordination with the used metal ions. This leads to enhancing ICT interaction, causing a significant shift in the presence of strongly complexing metal ions. This was fully reversible, where the solution of dye‐metal ion complex was decomplexed by adding an EDTA solution to revert the original spectrum of the dye. The stability constants, K, for the complexes of the investigated chemosensor with the mentioned metal ions were calculated, indicating that Co²⁺ is the most effectively detected, and the potential of the novel dye was highly efficient switchers for Co²⁺ ions. Additionally, the molecular modeling was carried out for the chemosensor and its metal complexes. Finally, the solid complexes have been tested for their in vitro antimicrobial activities against some bacterial strains (Gram +ve and Gram ?ve bacteria), as well as antifungal strains.     

Luminescence Method for Studying the Formation and Stability of Macromolecular Complexes of Transition Metals with Carboxyl-Containing Polymers in Organic Solvents

Quenching of the luminescence of carboxyl-containing polymer molecules containing a luminescent marker by transition metal ions (Cu²⁺, Ni²⁺) is observed not only in aqueous and aqueous-salt solutions, but also in polar organic solvents (methanol, ethanol, dimethylformamide). In dilute solutions, quenching refl ects binding of metal ions with the polymer and changes in the degree of filling of the polymer carboxyl groups with transition metal ions quenching the luminescence. The equilibrium stability constant of the formed macromolecular metal complex in organic media can be quantitatively estimated from the quenching effect using the relationships that follow from the law of mass action. The formation and stability of Cu²⁺ and Ni²⁺ complexes with polymethacrylic acid in protic (methanol, ethanol) and aprotic (dimethylformamide) solvents at low polymer concentrations (0.4–0.02 mg mL^–1) were studied using the quenching effect. In methanol, in contrast to ethanol and dimethylformamide, two mechanisms of binding of transition metal ions with different equilibrium stability constants of the complexes (\({K_{{1^{st}}}}\) > 3 × 10⁹ and \({K_{{2^{st}}}}\) ≈ 10⁶–10⁴) were revealed. The infl uence exerted on the stability of the complexes and on the complexation mechanism by the nature and acidity of the organic solvent, polymer concentration, kind of the transition metal ion quenching the luminescence, and NaOH and HCl additions was studied. The results obtained demonstrate the efficiency of the luminescence method used and prospects for its further use for studying polymer systems containing transition metal ions in organic solvents.     

Thermal degradation and smoke suspension of cotton cellulose modified with THPC and its lanthanide metal complexes

Complexes of cell–THPC–urea–ADP with transition metal ion Co²⁺ and lanthanide metal ions such as La³⁺, Ce⁴⁺, Nd³⁺ and Sm³⁺ have been prepared. The thermal behavior and smoke suspension of the samples are determined by TG, DTA, DTG and cone calorimetry. The activation energies for the second stage of thermal degradation have been obtained by following Broido equation. Experimental data show that for the complexes of cell–THPC–urea–ADP with the metal ions, the activation energies and thermal decomposition temperatures are higher than those of cell–THPC–urea–ADP, which shows these metal ions can increase the thermal stability of cell–THPC–urea–ADP. Moreover, these lanthanide metal ions can more increase thermal stability of samples than do the transition metal ion Co²⁺. The cone calorimetry data indicate that the lanthanide metal ions, similar to transition metal Co²⁺, greatly decrease the smoke, CO and CO₂ generation of cell–THPC–urea–ADP, which can be used as smoke suppressants.     

Solid phase extraction studies on cellulose based chelating resin for separation,pre-concentration and estimation of Cu2+and Ni2+

Chelating resins based on biopolymers, specifically cellulose, offers a green analytical method for determination of metal ions at trace levels present in various samples. It offers a fast, accurate and simple method for separation and pre-concentration of metal ions at low concentrations, prior to their determination by instrumental method. Cellulose based chelating resin (CELL-GLY) has been synthesised by immobilising glycine on it. CELL-GLY was used for the determination of trace amounts of Cu²⁺ and Ni²⁺ from aqueous solutions before their determination by FAAS. The preparation of CELL-GLY involves simple steps, based on natural and easily available biopolymer cellulose, which makes its use as chelating resin is a green method. The Cu²⁺ and Ni²⁺ can be quantitatively recovered from the CELL-GLY in the pH range 4.8–6.9 and 6.9-7.8 respectively with a recovery of more than 95% for each of these metal ions. Recovery of these metal ions using CELL-GLY was quantitative up to 35 °C. The detection limits for copper and nickel by FAAS were 1.20 ppb and 1.40 ppb, respectively. The method was successfully employed for the determination of trace amounts of Cu²⁺ and Ni²⁺ in various samples.     

Synthesis, coordination properties, and analytical applications of mixed donor macrocycles containing the 1,10-phenanthroline sub-unit

The coordination properties towards different metal ions of a new class of mixed N/S-, and N/S/O-donor macrocycles containing the 1,10-phenanthroline sub-unit in the cyclic framework are reviewed. The conformational constraints imposed by the heteroaromatic fragment onto the aliphatic portion of the ring determine the coordination mode of these ligands which can stabilise low-valent Ni⁺, Pd⁺, Pt⁺, and Rh⁺ metal complexes. Structural and thermodynamic aspects of the coordination chemistry of these ligands are considered together with possible applications as building blocks in the synthesis of multi-centred systems, and as template in the construction of extended polyiodide networks. However, solution studies demonstrate the inability of these ligands to work as selective and specific fluorescent chemosensors for heavy transition and post-transition metal ions and the formation constants evaluated for the formation of 1:1 complexes with Pb²⁺, Cd²⁺, Hg²⁺, Cu²⁺, and Ag⁺ in acetonitrile are of the same order of magnitude. Nevertheless, some of these macrocyles are extremely effective to recognise Cu²⁺ or Ag⁺ over the other metal ions in transport processes, and have been successfully used as neutral ionophore in the construction of PVC-based ionselective electrodes and supported liquid membranes for analytical detection and separation, respectively, of these metal ions.     

Influence of the central metal on the crystal structures and electronic structures of biferrocene trinuclear complexes

Five metal-bridged biferrocene complexes of the Schiff-base ligand (HL = S-benzyl-N-(ferrocenyl-1-methyl-methylidene)dithiocarbazate) have been studied by single crystal X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy. The crystal structures of the complexes show that the central metal ions are tetra-coordinated by two ligands in two modes: the central d⁸ transition metal ions (Ni²⁺, Pd²⁺, and Pt²⁺) are nearly square-planar coordinated and the d¹⁰ transition metal ions (Zn²⁺ and Cd²⁺) are tetrahedrally coordinated. Interestingly, the isomer shifts in ⁵⁷Fe Mössbauer spectroscopy are also of two kinds: d⁸ transition metal ions (0.097-0.247 mm/s) and d¹⁰ transition metal ions (0.416-0.435 mm/s).     

The stability of some metal EDTA, DTPA and DOTA complexes: Application as tracers in groundwater studies

Studies of the stability of various metal EDTA, DTPA and DOTA complexes in order to evaluate their applicability as non-sorbing tracers have been performed. In laboratory tests, the stability generally increases for the individual metal ions in the EDTA<DTPA<DOTA order. For most metal ions, the same trend can be observed for the thermodynamic stability constants. In the in situ experiment, various metal EDTA tracers were used in very low concentrations; YbEDTA⁻, for example had a breakthrough and recovery which were very similar to the non-sorbing tracers used. According to the extremely low tracers concentrations used, thermodynamic data indicate that all metal EDTA tracers should have been decomplexed as a result of the competition with the naturally occurring cations in the groundwater. This was not found, which indicates that the decomplexation rate and sorption mechanism are important in estimating the applicability of the metal complexes as tracers. The DOTA complexes of elements in the middle of the lanthanide series have indicated high stability in the laboratory tests and therefore appear to be good candidates as non-sorbing tracers. However, in contrary to the metal EDTA, tracers, the DOTA complexes of La³⁺ and Lu³⁺ seemed to be slightly delayed in the in situ experiment.     

The transformation from 2°‐amine to 3°‐amine of cyclam ring alters the fragmentation patterns of 1‐tosylcytosine‐cyclam conjugates

The novel N‐1‐sulfonylcytosine‐cyclam conjugates 1 and 2 conjugates are ionized by electrospray ionization mass spectrometry (ESI MS) in positive and negative modes (ES⁺ and ES⁻) as singly protonated/deprotonated species or as singly or doubly charged metal complexes. Their structure and fragmentation behavior is examined by collision induced experiments. It was observed that the structure of the conjugate dictated the mode of the ionization: 1 was analyzed in ES⁻ mode while 2 in positive mode. Complexation with metal ions did not have the influence on the ionization mode. Zn²⁺ and Cu²⁺ complexes with ligand 1 followed the similar fragmentation pattern in negative ionization mode. The transformation from 2°‐amine in 1 to 3°‐amine of cyclam ring in 2 leads to the different fragmentation patterns due to the modification of the protonation priority which changed the fragmentation channels within the conjugate itself. Cu²⁺ ions formed complexes practically immediately, and the priority had the cyclam portion of the ligand 2 . The structure of the formed Zn²⁺ complexes with ligand 2 depended on the number of 3° amines within the cyclam portion of the conjugate and the ratio of the metal:ligand used. The cleavage of the cyclam ring of metal complexes is driven by the formation of the fragment that suited the coordinating demand of the metal ions and the collision energy applied. Finally, it was shown that the structure of the cyclam conjugate dictates the fragmentation reactions and not the metal ions.