Thermal investigations of nitrate-hydrates and deuterates of Ca2+, Cd2+ and Mg2+

DTA and DSC were used to study the thermal behaviour of Ca(NO₃)₂·4H₂O, Cd(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O and their deuterated analogues. Evidence was found concerning the process of melting of the initial hydrates and deuterates, followed by a one-stage dehydration of the melt to vield the respective anhydrous salt. T _m, ΔH _m ^o , ΔS _m ^o and ΔH _deh ^o were determined and the ΔH _f ^o values for the investigated hydrates were calculated from the ΔH _deh ^o data.

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Zusammenfassung DTA und DSC wurden zur Untersuchung des thermischen Verhaltens von Ca(NO₃)₂·4H₂O, Cd(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O und ihrer deuterierten Analoge eingesetzt. Man fand Aussagen bezüglich des Schmelzvorganges der Ausgangshydrate und Deuterate, gefolgt von einer Einschritt-Dehydratation der Schmelze unter Bildung der entsprechenden wasserfreien Salze. T _m, ΔH _m ^o , ΔS _m ^o und ΔH _deh ^o wurden ermittelt und die ΔH _f ^o Werte für die untersuchten Hydrate wurden anhand der ΔH _deh ^o berechnet.

     

Cd2+ and Zn2+ Complexes with 2,4,6‐Tri(2‐pyridyl)‐s‐Triazine and Terephthalate for Rapid,High‐Capacity Adsorption of Congo Red

Three crystal complexes were designed and synthesised through the solvothermal method, with Cu²⁺, Zn²⁺, and Cd²⁺ ions as the metal centres and 2,4,6‐tri(2‐pyridyl)‐s‐triazine (TPTZ) and terephthalate (BDC²⁻) as the ligands. Their compositions were determined to be Cd(TPTZ)Cl₂ (Cd‐MOF), {[Zn(TPTZ)(BDC)] ⋅ 3H₂O}_n (Zn‐MOF), and Cu₂(PCA)₂(BDC)(H₂O)₂ (Cu‐MOF) (PCA⁻=2‐pyridinium amide), respectively. Cd‐MOF can adsorb 90 % of Congo red (CR) in 10 s at room temperature and atmospheric pressure, and CR removal was complete at 20 s over a wide pH range. The adsorption capacity for CR reached 1440 mg g⁻¹ in 5 min. Selective adsorption was demonstrated in mixed dyes. The adsorption kinetic data agree well with the pseudo‐second‐order kinetic model. The Temkin model was successfully used to evaluate the adsorption isotherms of CR on Cd‐MOF at room temperature, suggesting that adsorption occurs through a hybrid of monolayer and multilayer mechanisms.     

邻二氮菲-Cd2+与DNA的相互作用研究

本文以邻二氮菲作为分子探针,在磷酸盐-氯化钠中性介质中(pH=7.2),用荧光光谱和吸收光谱法研究了邻二氮菲-Cd²⁺与DNA之间的相互作用。结果表明,Cd²⁺离子与邻二氮菲形成1∶2型的配合物,该配合物与DNA有较强的相互作用,这是位于配合物中心的Cd²⁺离子与DNA发生键合。实验发现,在邻二氮菲-Cd²⁺-DNA体系中加入EDTA或柠檬酸,邻二氮菲-Cd²⁺与DNA的相互作用减弱,这表明EDTA或柠檬酸对Cd²⁺的毒性有一定的缓解作用。     

A Polarographic Study of Tl + , Pb 2 and Cd 2+ Complexes with Dicyclohexano-18-Crown-6 in Some Binary Mixed Solvents

The complexes of Tl⁺, Pb²⁺ and Cd²⁺ cations with the macrocyclic ligand, dicyclohexano-18-crown-6\linebreak(DC18C6) were studied in water/methanol (H₂₊O/MeOH), water/1-propanol (H₂₊O/1-PrOH), water/acetonitrile (H₂₊O/AN), water/dimethylformamide (H₂₊O/DMF), dimethylformamide/acetonitrile (DMF/AN), dimethylformamide/methanol (DMF/MeOH), dimethylformamide/1-propanol (DMF/1-PrOH) and dimethylformamide/nitromethane (DMF/NM) mixed solvents at 22 °C using differential pulse polarography (DPP), square wave polarography and conductometry. In general, the stability of the complexes was found to decrease with increasing concentration of water in aqueous/non-aqueous mixed solvents with an inverse relationship between the stability constants of the complexes and the concentration of DMF in non-aqueous mixed solvents. The results show that the change in stability of DC18C6.Tl⁺, vs the composition of solvent in DMF/AN and DMF/NM mixed solvents is apparently different from that in DMF/MeOH and DMF/1-PrOH mixed solvents. While the variation of stability constants of the DC18C6.Tl⁺ and DC18C6.Pb²⁺ complexes vs the composition of H₂₊O/AN mixed solvents is monotonic, an anomalous behavior was observed for variations of log K_f vs the composition of H₂₊O/1-PrOH and H₂₊O/MeOH mixed solvents. The selectivity order of the DC18C6 ligand for the cations was found to be Pb²⁺ > Tl⁺ > Cd²⁺.     

13C, 15N and 113Cd NMR and Molecular Orbital Studies of Novel Bile Acid N-(2-aminoethyl)amides and Their Cd2+-complexes

Lithocholic acid N-(2-aminoethyl)amide (1) and deoxycholic acid N-(2-aminoethyl)amide(2) have been prepared and characterized by¹H, ¹³C and ¹⁵N NMR. The accurate molecular masses of 1 and 2 have been determined by ESI MS. The formation of the Cd²⁺-complexes (1+Cd and 2+Cd) in CD₃OD solution have been detected by ¹H,¹³C, ¹⁵N and ¹¹³Cd NMR. The ¹³C NMR chemical shift assignments of 1 and 2 and their Cd²⁺-complexes are based on DEPT-135 and z-GS ¹H,¹³C HMQC experiments as well as comparison with the assignments of the related structures. The ¹⁵N NMR chemical shiftassignments of the ligands and theirCd²⁺-complexes are based on z-GS¹H,¹⁵N HMBC experiments. ¹³C NMR chemical shift differences between 1and its 1:1 Cd²⁺-complex based on ab initiocalculations at Hartree-Fock SCI-PCM level using3-21G(d) basis set are in agreement with theexperimental shift changes observed onCd²⁺-complexation.     

A novel turn-on fluorescent probe for Hg2+ detection based on rhodamine B spirolactam derivative

ABSTRACT

In this work, a new turn-on fluorescent probe 1 for Hg²⁺ ions detection based on rhodamine B spirolactam was reported. Among tested metal ions, probe 1 shows high selectivity towards Hg²⁺ in the the mixture solution of methanol and 0.02 M HEPES buffer (V/V = 9:1, pH = 7.2). No absorption and emission band of probe 1 was observed in the range from 450 to 700 nm. While only addition of Hg²⁺ to probe 1 could lead to appearance of a new absorption band centered at 553 nm and a fluorescence emission band around 577 nm upon excitation at 520 nm. Moreover, it exhibits excellent linear relationship (R² = 0.9993) between fluorescence intensity at 577 nm and the concentration of Hg²⁺ from 1.6 to 32 μM. The sensing mechanism was proven to be spirolactam ring open induced by Hg²⁺ through ¹H NMR, MS, absorption and fluorescence spectra. In addition, probe 1 could detect Hg²⁺ in real water samples and on filter paper, which demonstrates its application in environment science.     

Complex Formation of 1,10-Dibenzyl-1,10-diaza-18-crown-6 with Ni2+, Cu2+, Ag+ and Cd2+ Metal Cations in Acetonitrile–dimethylformamide Binary Solutions

Conductance measurements are reported for nickel(II), cupper(II), silver(I) and cadmium(II), salts in acetonitrile (AN)–dimethylformamide (DMF) binary solvents containing macrocyclic ligand, 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBDA18C6) at different temperatures. The changes in molar conductance caused by addition of DBDA18C6 to solutions were analyzed by non-linear least squares to give stability constants of 1:1 metal cation–DBDA18C6 complexes. The results show that the stabilities of the complexes are sensitive to solvent composition and in some cases the sequence of stabilities is changed with changing the composition of the mixed solvents. The values of thermodynamic quantities (ΔH°c and ΔS°c) for formation of DBDA18C6-Ni²⁺, DBDA18C6-Cu²⁺, DBDA18C6-Ag⁺ and DBDA18C6-Cd²⁺ complexes were obtained from temperature dependence of the stability constants and the results show that the values of ΔH°c and ΔS°c for these complexes are sensitive to the nature and composition of AN–DMF binary solutions, but they do not vary monotonically with the solvent composition.     

A Conductometric Study of Complexation Reactions Between Dibenzo-18-Crown-6 (DB18C6) with Cu2+, Zn2+, Tl+ and Cd2+ Metal Cations in Dimethylsulfoxide–Ethylacetate Binary Mixtures

The complex formation between Cu²⁺, Zn²⁺, Tl⁺ and Cd²⁺ metal cations with macrocyclic ligand, dibenzo- 18-crown-6 (DB18C6) was studied in dimethylsulfoxide (DMSO)–ethylacetate (EtOAc) binary systems at different temperatures using conductometric method. In all cases, DB18C6 forms 1:1 complexes with these metal cations. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, Genplot. The non-linear behaviour which was observed for variations of log K _f of the complexes versus the composition of the mixed solvent was discussed in terms of changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity order of DB18C6 for the metal cations in pure ethylacetate and pure dimethylsulfoxide is: Tl⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺ but the selectivity order is changed with the composition of the mixed solvents. The values of enthalpy changes (ΔH°_C) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard enthalpy (ΔS°_C) were calculated from the relationship: ΔG°_C,298.15=ΔH°_C − 298.15 ΔS°_C. The obtained results show that in most cases, the complexes are enthalpy stabilized, but entropy destabilized and the values of ΔH°_C and ΔS°_C depend strongly on the nature of the medium.     

Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions

Janus-type triskelion-shaped fluorophores comprising coumarins bearing various electron-donating substituents (1aad, 1add, 1ccd, and 1cdd) were successfully synthesized via an intramolecular Ullmann coupling. Density functional theory (DFT) calculations indicated that all the compounds presented two different molecular surfaces, similar to Janus-type molecules. The absorption and fluorescence spectra of asymmetrical derivatives 1aad, 1add, 1ccd, and 1cdd exhibited a bathochromic shift due to their narrow highest occupied molecular orbital (HOMO) –lowest unoccupied molecular orbital (LUMO) gap. Natural transition orbital (NTO) analysis indicated that the excited state orbital overlaps differ among the C₃ symmetrical and asymmetrical dyes. These triskelion-shaped fluorophores were found to form molecular nanoaggregates in THF/H₂O mixtures and demonstrated aggregation-induced emission (AIE) enhancement characteristics as a result of restricting their molecular inversion. These results indicate that Janus-type AIE fluorophores are potentially applicable as solid-state fluorescent chiral materials, which can be optimized by controlling their molecular rearrangement in the solid state.     

A Polarographic Study of Tl+, Pb2+ and Cd2+ Complexes with Aza-18-crown-6 and Dibenzopyridino-18-crown-6 in some Binary Mixed Non-aqueous Solvents

The complexation of Tl⁺, Pb²⁺and Cd²⁺ cations by macrocyclic ligands, aza-18-crown-6 (L1) and dibenzopyridino-18-crown-6 (L2) was studied in some binary mixtures of methanol (MeOH), n-propanol (n-PrOH), nitromethane (NM) and acetonitrile (AN) with dimethylformamide (DMF) at 22 °C using DC (direct current) and differential pulse polarographic techniques (DPP). The stoichiometry and stability constants of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the ligand concentration. In all of the solvent systems, the stability of the resulting 1:1 complexes was found to be L1 > L2. The selectivity order of the L2 ligand for the cations was found to be Pb²⁺ > Tl⁺ > Cd²⁺ and the selectivity of the L1 ligand for Pb²⁺ ion was greater than that of Tl⁺ ion. The results show that the stability of the complexes depends on the nature and composition of the mixed solvents. There is an inverse relationship between the stability constants of the complexes and the amount of dimethylformamide in the mixed solvent systems.     

Detection of toxic effects of Cd2+ on different fish species via liver cytochrome P450-dependent monooxygenase activities and FTIR spectroscopy

The in vivo and in vitro effects of Cd²⁺ and the CYP1A inductor β-naphthoflavone(β-NF) on the hepatic cytochrome P450 (Cyt 450) monooxygenases were studied in silver carp (Hypophthalmichtys molitrix V.), wels (Silurus glanis L.), and carp (Cyprinus carpio). In vivo treatment of carp with a high dose of Cd²⁺ (10 mg kg⁻¹, for 3 days) caused a strong inhibition of 7-ethoxyresorufin-O-deethylase (EROD) and a lower inhibition of 7-ethoxycoumarin-O-deethylase (ECOD) activity. The low-dose cadmium treatment (2 mg kg⁻¹ Cd²⁺, for 6+3 days) resulted in 4-fold increase in EROD and a 3-fold increase in ECOD activity. The combined treatment with Cd²⁺ and β-NF in both cases led to a loss of EROD inducibility. The silver carp and wels were treated with 10 mg L⁻¹ Cd²⁺ for 72 h in water. The Cyt P450 content in the wels liver microsomes was increased significantly after treatment for 48 h, whereas there was only a slight, not significant increase in Cyt P450 content in the silver carp microsomes. While the Cd²⁺ treatment resulted in inhibition of the CYP1A isoenzymes (EROD and ECOD), the APND (aminopyrene-N-demethylase, CYP2B or CYP3A isoenzyme) activity was increased 3- to 4-fold in both fish species. In vitro experiments of the effect of Cd²⁺ led to a concentration-dependent inhibition in all three investigated fish species. The ECOD isoenzyme of silver carp was the most sensitive to Cd²⁺. The lowest concentration of Cd²⁺ resulted in 50% inhibition. The APND isoenzyme was similarly sensitive to Cd²⁺ in all three investigated fish species. The most sensitive species was the wels, and the least sensitive were the carp isoenzyme. FTIR spectroscopy confirmed that cadmium caused damage to the protein structure. These results support the enzyme activity measurements measured in vivo and in vitro.     

Conformationally regulated fluorescent sensors. Study of the selectivity in Zn versus Cd sensing

The Zn²⁺ and Cd²⁺ complexing properties of four ligands containing a 4,4′-substituted biphenyl moiety are described. Ligands 1 and 3, containing only one 1-aza-18-crown-6 cavity, lead to selective complexation of Cd²⁺ versus Zn²⁺. Ligand 4, with two crown cavities linked to a tetramethylbenzidine unit, is able to form 1:1 complexes with Zn²⁺ and Cd²⁺, showing a higher complexing constant with Zn²⁺ than with Cd²⁺, probably due to enthalpic factors. Several complementary experiments suggest that the 1:1 complexes formed by ligand 4 involve both crown cavities acting together to give rise to clamp structures. The formation of this type of zinc complex gives rise to red shifted emission bands and distinct quenching of the fluorescence. A similar situation is observed with cadmium but the change is then less pronounced. When mixtures of both salts are used, ligand 4 selectively responds to zinc. Finally, ligand 2, which also has two crown cavities but contains nitro rather than amino groups in the biphenyl moiety, shows no propensity to form clamp complexes and, for this reason, it complexes cadmium much more strongly than zinc and binds the former selectively when mixtures of both salts are used in complexing experiments.     

基于多肽与金属离子作用的一种高选择性Cd2+荧光比率传感器

利用固相多肽合成法合成了一种新的多肽,将该多肽与荧光基团Dansyl偶联制备了一种新的荧光化学比率传感器:Dansyl-Cys-Pro-Pro-Cys-Trp-NH₂。利用荧光光谱研究了它与金属离子的相互作用。结果表明,与其它13种金属离子相比该多肽对金属Cd²⁺有很好的选择性。它能特异性识别Cd²⁺,具有水溶性好,响应时间快等优点。该肽对Cd²⁺具有很强的键合作用,其结合常数为3.0×10¹¹ L²·mol^-2,检出限为11.5 nmol·L^-1。     

Synthesis of 1,8-naphthyridine and BF2-based isomers and their application in fluorogenic sensing Cd

A series of isomers were synthesized and identified, two isomers of which were developed as the dual-channel fluorescent probe toward Cd²⁺. BF₂ dissociates from the probe upon reaction with CdCl₂, demonstrating a new approach for sensing Cd²⁺.     

Epoxy-based oligomer containing dithia-aza-based naphthylazobenzene pendant: a chemosensor for Hg2+ and Cu2+ ions

A simple epoxy-based oligomer 1 containing naphthylazobenzene-appended dithia-aza moieties was prepared. In UV–vis measurements, the proposed oligomer showed the ion-sensing ability to Hg²⁺ and Cu²⁺ ions. The discrimination between two differently responding Hg²⁺ and Cu²⁺ ions was also realised from ‘ON–OFF’ type fluorescence responses of 1.     

Heavy metal removal using SiO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> binary oxide: experimental design approach

Sorption of Ni²⁺ and Cd²⁺ as heavy metals ions at the interface of the binary oxide TiO₂-SiO₂ was investigated. In addition, physical properties of TiO₂-SiO₂ matrices such as BET surface area, X-ray diffraction, and point of zero charge (pH_PZC) were measured. Statistical design of experiments was applied to find the conditions of sorption at which the maximum heavy metal removal was achieved. A second order polynomial function was used to correlate the independent variables (pH, metal ion concentration, and shaking time) and response (heavy metal removal). Values of regression parameters were determined by the computer program, Design expert^® (Stat-Ease Inc.). The quality of fit of the polynomial model equation was expressed by the regression coefficient R ². The sorption results showed that the pH is the most significant factor. In turn, the sorbed percentage reached 100% at high initial concentration and long shaking times due to formation of hydroxyl compounds between the ions and TiO₂-SiO₂ matrices. The results show that there is a Gaussian (normal) distribution of residuals (squared differences between experimentally observed and predicted values from the model), and also that the differences between observed and predicted values are in the range of ±5%. These indicate that experiments were well-conducted and the results have no significant error.     

A highly selective visual and fluorescent sensor for Pb2+ and Zn2+ and crystal structure of Cu2+ complex based-on a novel single-armed Salamo-type bisoxime

A novel single-armed Salamo-type bisoximes (H₄L) has been designed and synthesised. An obvious colour change from yellow (H₄L) to pale pink (HL-Pb²⁺) which can be visually observed by the naked eye in visible light. H₄L can act as a fluorescent sensor for ratiometric recognition of Zn²⁺ with high selectivity and sensitivity. Crystallographic data of the [Cu(HL)(μ-OAc)Cu] reveals that the two Cu²⁺ ions are both penta-coordinated with square pyramidal geometries, and forms a 2D supramolecular plane structure by hydrogen bonding interactions.     

Study of Complex Formation between N-Phenylaza-15-Crown-5 with Mg2+, Ca2+, Ag+ and Cd2+ Metal Cations in Some Binary Mixed Aqueous and Non-aqueous Solvents using the Conductometric Method

The complexation reactions between Mg²⁺, Ca²⁺, Ag⁺ and Cd²⁺ metal cations with N-phenylaza-15-crown-5 (Ph-N15C5) were studied in acetonitrile (AN)–methanol (MeOH), methanol (MeOH)–water (H₂O) and propanol (PrOH)–water (H₂O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stochiometry of all of the complexes with Mg²⁺, Ca²⁺, Ag⁺ and Cd²⁺ cations is 1:1 (L:M). The stability of the complexes is sensitive to the solvent composition and a non-linear behaviour was observed for variation of log K _f of the complexes versus the composition of the binary mixed solvents. The selectivity order of Ph-N15C5 for the metal cations in neat MeOH is Ag⁺>Cd²⁺>Ca²⁺>Mg²⁺, but in the case of neat AN is Ca²⁺>Cd²⁺>Mg²⁺>Ag⁺. The values of thermodynamic parameters (ΔH _c ^o , ΔS _c ^o ) for formation of Ph-N15C5–Mg²⁺, Ph-N15C5–Ca²⁺, Ph-N15C5–Ag⁺ and Ph-N15C5–Cd²⁺ complexes were obtained from temperature dependence of stability constants and the results show that the thermodynamics of complexation reactions is affected by the nature and composition of the mixed solvents.     

Sodium polyacrylate as a binding agent in diffusive gradients in thin-films technique for the measurement of Cu and Cd in waters

An aqueous solution containing sodium polyacrylate (PA, 0.0030 M) was used in diffusive gradients in thin-films technique (DGT) to measure DGT-labile Cu²⁺ and Cd²⁺ concentrations. The DGT devices (PA DGT) were validated in four types of solutions, including synthetic river waters containing metal ions with or without complexing EDTA, natural river water (Hun River, Shenyang, China) spiked with Cu²⁺ and Cd²⁺, and an industrial wastewater (Shenyang, China). Results showed that only free metal ions were measured by PA DGT, recovery = 98.79% for Cu²⁺ and recovery = 97.80% for Cd²⁺ in solutions containing only free metal ions, recovery = 51.02% for Cu²⁺ and recovery = 51.92% for Cd²⁺ in solution with metal/EDTA molar ratio of 2:1 and recovery = 0 in solutions with metal/EDTA molar ratio of 1:1 and 1:2. These indicated that the complexes of Cu-EDTA and Cd-EDTA were DGT-inert or not DGT-labile. The DGT performance in spiked river water (recovery = 8.47% for Cu²⁺ and recovery = 27.48% for Cd²⁺) and in industrial wastewater (recovery = 14.16% for Cd²⁺) were also investigated. Conditional stability constants (log K) of PA-Cu and PA-Cd complexes were determined as 6.98 and 5.61, respectively, indicating strong interaction between PA and the metals.     

Density Functional Method Study on the Cooperativity of Intermolecular H-bonding and π-π+ Stacking Interactions in Thymine-[Cnmim]Br (n = 2, 4, 6, 8, 10) Microhydrates

The exploration of the ionic liquids’ mechanism of action on nucleobase’s structure and properties is still limited. In this work, the binding model of the 1-alkyl-3-methylimidazolium bromide ([C_nmim]Br, n = 2, 4, 6, 8, 10) ionic liquids to the thymine (T) was studied in a water environment (PCM) and a microhydrated surroundings (PCM + wH₂O). Geometries of the mono-, di-, tri-, and tetra-ionic thymine (T-wH₂O-y[C_nmim]⁺-xBr⁻, w = 5~1 and x + y = 0~4) complexes were optimized at the M06-2X/6-311++G(2d, p) level. The IR and UV-Vis spectra, QTAIM, and NBO analysis for the most stable T-4H₂O-Br⁻-1, T-3H₂O-[C_nmim]⁺-Br⁻-1, T-2H₂O-[C_nmim]⁺-2Br⁻-1, and T-1H₂O-2[C_nmim]⁺-2Br⁻-1 hydrates were presented in great detail. The results show that the order of the arrangement stability of thymine with the cations (T-[C_nmim]⁺) by PCM is stacking > perpendicular > coplanar, and with the anion (T-Br⁻) is front > top. The stability order for the different microhydrates is following T-5H₂O-1 < T-4H₂O-Br⁻-1 < T-3H₂O-[C_nmim]⁺-Br⁻-1 < T-2H₂O-[C_nmim]⁺-2Br⁻-1 < T-1H₂O-2[C_nmim]⁺-2Br⁻-1. A good linear relationship between binding E_B values and the increasing number (x + y) of ions has been found, which indicates that the cooperativity of interactions for the H-bonding and π-π⁺ stacking is varying incrementally in the growing ionic clusters. The stacking model between thymine and [C_nmim]⁺ cations is accompanied by weaker hydrogen bonds which are always much less favorable than those in T-xBr⁻ complexes; the same trend holds when the clusters in size grow and the length of alkyl chains in the imidazolium cations increase. QTAIM and NBO analytical methods support the existence of mutually reinforcing hydrogen bonds and π-π cooperativity in the systems.