Aggregation Of Metal Complexes Research Articles

N, S co-doped carbon dots for fluorescent and colorimetric dual-mode detection of Co(II) in actual water

This study focuses on the synthesis of nitrogen and sulfur co-doped carbon dots (N, S-CDs) using a hydrothermal method, and its application as a fluorescence and colorimetric dual-mode probe for simple and rapid detection of Co(II). When Co(II) reacts with N, S-CDs, metallic bonds are formed, leading to a static quenching effect (SQE). The electrostatic interaction between positive-charged cobalt complexes and negative-charged N, S-CDs induces the aggregation of metal complexes, increasing the particle size from 5.44 nm to 258.72 nm and resulting in a noticeable visual color change ultimately. N, S-CDs exhibited excellent potential for application in actual water samples, with the low detection limit (LOD) of 2.64 µM and 1.57 µM via fluorescence and colorimetric methods, respectively, and the recovery rate ranged from 94 % to 103 %. As far as we consider, the cross-referenced dual-mode platform proposed here may be an attractive strategy for the construction of high-performance sensors available for metal ion detection in actual aquatic environments.

ХЕЛАТУВАННЯ ДВОВАЛЕНТНИХ КАТІОНІВ ТА АНТИРАКОВА АКТИВНІСТЬПОХІДНИХ 8-ГІДРОКСИСТИРИЛХІНОЛІНІВ IN VITRO

Background. The search for new methods of cancer treatment and diagnosis are important. The disadvantages of chemotherapy drugs are the rapid acquisition of resistance and high toxicity. 8-hydroxyquinoline derivatives have a wide spectrum of biological activity and have the necessary properties for fluorescent cancer diagnosis. The aim of the study was to determine the chelation of calcium, magnesium and zinc cations by hydrophobic derivatives of 8-hydroxystyrylquinolines (8HQ) 2-(4-chlorostyryl)quinolin-8-ol (STQ-Cl) and 2-(4-nitrostyryl)quinolin-8-ol (STQ-NO2) in physiological solution, the stability of the complexes and the cytotoxicity of the compounds to prostate and breast cancer cell lines in vitro. Methods. 8HQ derivatives STQ-Cl and STQ-NO2 were used. Solutions of Ca2+, Mg2+, Zn2+ cations were prepared by the method of two-fold dilutions in 0.5-0.0078125 mM concentration range based on 0.9 % NaCl. Both individual solutions of each cation and a mixture in an equivalent molar ratio were used. The concentration of 8HQ derivatives were 0.05 mM. Optical absorption was registered in 200-700 nm wavelength range. Cytotoxicity was investigated on breast (MDA-MB-231) and prostate (DU-145) cancer cell lines. STQ-Cl and STQ-NO2 derivatives in DMSO were added to the incubation solution by four-fold dilutions (0.125–0.00003 mM). For luminescence studies, MDA-MB-231 and DU-145 cells were grown on coverslips. The final concentration of 8HQ derivatives were 5 mM. Cells were kept for 5, 10, 20 and 30 min. Luminescence was recorded under the same conditions for all samples, with an exposure time of 10 ms. Results. Mg2+ and Ca2+ (0.03125 mM) were contributed to reduce the intensity of optical absorption maxima of STQ-Cl by 1.6 and 1.3 times, respectively. The effect was most pronounced at 0.015625 mM Zn2+. Weak differences in the optical absorption of solutions were detected when STQ-NO2 was incubated with different concentrations of Mg2+ and Ca2+. The optical absorption intensity of the STQ-NO2 aqueous solution was increased at 0.015625 and 0.03125 mM Zn2+. The maximum cytotoxicity against MDA-MB-231 cells for STQ-Cl was about 80 %, and STQ-NO2 was 60 % at 0.04 mM Zn2+. DU-145 cells were more sensitive to STQ-NO2 (EC50 = 0.011 mM), but weakly sensitive to STQ-Cl (50 % at 0.125 mM). The maximum luminescence intensity was after 20 min of incubation with STQ-Cl and STQ-NO2 (5 mM) for both cells lines and was not change over time. Conclusions. The decrease of optical absorption maxima of STQ-Cl aqueous solutions in the presence of magnesium, calcium, and zinc cations was a consequence of aggregation processes. This phenomenon was probably the reason for the different cytotoxicity of STQ-Cl and STQ-NO2, as well as the presence of other mechanisms of action to cancer cells. Results was a consequence of different affinity of 8-hydroxyquinoline derivatives to magnesium, calcium and zinc cations, solubility in water, stability, aggregation of metal complexes and free compounds.

Transparent, highly thermostable and flame retardant polycarbonate enabled by rod-like phosphorous-containing metal complex aggregates

It has been desirable to create flame retardant, transparent polycarbonate (PC) materials while retaining high thermostability and mechanical strength to meet its practical applications in the electrical, optical lighting, automobile and mobile fields. Unfortunately, current flame retardants offer satisfactory flame retardancy at the expense of other properties because of improper designs. For this reason, it has remained a grand challenge to achieve an integrated performance portfolio. Herein, we report rod-like phosphorus-containing metal complex aggregates (CePn) by one-step solvothermal method. The results show that the peak heat release rate (PHRR) and total smoke release (TSR) of the bulk PC are respectively reduced by 46% and 26% in the addition of 4 wt% of CePn, in addition to a desired UL-94 V-0 rating and a limiting oxygen index (LOI) of 27.3% because of dual-phase flame retardant mechanisms of CePn. Moreover, the final PC maintains a high transparency of 90.1% and a comparable tensile strength to the bulk PC. Moreover, the final PC composite shows enhanced thermal stability noticeably which is superior to that of any other reported systems. This work offers an innovative methodology for the design of flame retardants with tunable aggregated morphologies, and the creation of high-performance PC composites combining exceptional flame retardancy, transparency, thermostability and mechanical strength.

Electrolytic formation of metal complex nanoaggregates from polymethine dyes on metallic electrodes

An electrolytic method for the synthesis of metal complex aggregates from polymethine dyes on the surface of anodes from metals capable of electrolytic oxidation has been developed. It has been concluded that the electrochemical method for the synthesis of aggregates from polymethine dyes has technological prospects for the creation of photosensitive elements in organic nanoelectronics and photonics.

Study of the Aggregation of Metal Complexes with Asphaltenes Using Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry

Gel permeation chromatography inductively coupled plasma high-resolution mass spectrometry (GPC ICP HR MS) was used for the understanding of the evolution of two crude oil cut samples after their dilution. We first studied different method parameters to compare two GPC procedures already published [flow rate, column set, and presence or not of the tetrahydrofuran (THF) stabilizer]. Thus, the principal parameters affecting the molecular size distribution and its evolution were demonstrated. The column set and flow rate can drastically affect the molecular size distribution of the sample. Moreover, an evolution of the size distribution of the complexes of vanadium, nickel, and sulfur into higher molecular weight compounds was observed over time. The study led to the recommendation of the sample preparation to the same day of the analysis to obtain reproducible data.

Interplay between the Supramolecular Motifs of Polypyridyl Metal Complexes and Halogen Bond Networks in Cocrystals

Combining [Ni(phen)3]I2 or [Ni(phen)3]Cl2 (phen = 1,10-phenanthroline) with the iodoperfluorobenzenes (IPFBs), 1,2-, 1,3-, 1,4-diiodotetrafluorobenzene (1,2-, 1,3-, and 1,4-DITFB, respectively), or 1,3,5-triiodotrifluorobenzene (1,3,5-TITFB) resulted in the formation of six different cocrystalline materials featuring halogen-bonded networks encapsulating [Ni(phen)3]2+ ions. The cocrystals have the general formula [Ni(phen)3][(IPFB)n(X2)(L)m]·solvate (n = 2 or 3; X = Cl– or I–; L = halogen-bonded H2O and/or MeOH; solvate = isolated H2O and/or MeOH). The halide ions balance the charge of the metal complexes and simultaneously act as halogen bond acceptors for the electronically polarized iodine atoms of the IPFB donors. The structures display a wide variety of supramolecular motifs in the context of both the aggregation of the metal complexes and the topology and connectivity of the halogen bond networks. The well-known supramolecular “aryl embrace” motifs of [Ni(phen)3] complexes are present but are structurally compromised to varying degrees in the crystals of [Ni(phen)3][(1,2-DITFB)2I2]·MeOH, [Ni(phen)3][(1,3-DITFB)2I2]·2MeOH, and [Ni(phen)3][(1,3-DITFB)2(H2O)2Cl2]·1.5MeOH. In [Ni(phen)3][(1,3-DITFB)3I2], the [Ni(phen3]2+ complexes are so thoroughly enclosed in halogen-bonded networks that the metal complexes have no significant supramolecular contact. In contrast, in [Ni(phen)3][(1,4-DITFB)3I2(MeOH)0.5] and [Ni(phen)3][(1,3,5-TITFB)2Cl2] the complexes are arranged in typical aryl embrace motifs (pairwise and 1D chains, respectively), but with adjacent complexes held in closer proximity to each other than they reside in crystals of the pure metal complex. The interplay between the supramolecular chemistry of the halogen-bonded networks and the metal complexes was examined in detail, and the results demonstrate that it is possible to significantly influence the aggregation of metal complexes by encapsulation in different halogen bond networks.

Selective label-free detection of G-quadruplex structure of human telomere by emission spectral changes in visible-and-NIR region under physiological condition through the FRET of a two-component PPE-SO3−–Pt(ii) complex ensemble with Pt⋯Pt, electrostatic and π–π interactions

The formation of polymer–metal complex aggregates and the FRET between PPE-SO3− and several water-soluble cationic alkynylplatinum(II) complexes are revealed from UV-vis, steady-state emission and time-resolved emission decay studies. From the Stern–Volmer plots, [Pt{tpy(C6H4CH2NMe3-4)-4′}(CCC6H5)](OTf)2 (2) is found to be the most efficient quencher of PPE-SO3− at both low and high concentrations. This has been ascribed to its low steric bulkiness and the stronger interactions with PPE-SO3−, and hence the largest association constant with PPE-SO3−, as well as the largest Forster radius, R0, among the complexes studied. The PPE-SO3−–2 ensemble has been employed in the detection of human telomere in aqueous buffer solution (50 mM KH2PO4, pH 6.8) and found to have better selectivity than the ensemble containing [Pt(tpy)(CCC6H4CH2NMe3-4)](OTf)2 (1), which has a smaller association constant with PPE-SO3− and R0 value than 2. By modulation of the aggregation/deaggregation of the polymer–metal complex aggregates and hence the FRET from the PPE-SO3− donor to the aggregated forms of 2 as acceptor, the PPE-SO3−–2 ensemble has been demonstrated for the sensitive and selective label-free detection of human telomere via the monitoring of emission spectral changes over the visible-NIR region. Ratiometric emission of PPE-SO3−–2 ensemble at 620 and 795 nm has been shown to distinguish the G-quadruplex structure formed by human telomeric DNA from those of other G-quadruplex-forming sequences.

Induced Self-Assembly and Förster Resonance Energy Transfer Studies of Alkynylplatinum(II) Terpyridine Complex Through Interaction With Water-Soluble Poly(phenylene ethynylene sulfonate) and the Proof-of-Principle Demonstration of this Two-Component Ensemble for Selective Label-Free Detection of Human Serum Albumin

The interaction of conjugated polyelectrolyte, PPE-SO(3)(-), with platinum(II) complexes, [Pt(tpy)(C≡CC(6)H(4)-CH(2)NMe(3)-4)](OTf)(2) (1) and [Pt(tpy)(C≡C-CH(2)NMe(3))](OTf)(2) (2), has been studied by UV-vis, and steady-state and time-resolved emission spectroscopy. A unique FRET from PPE-SO(3)(-) to the aggregated complex 1 on the polymer chain with Pt···Pt interaction has been demonstrated, resulting in the growth of triplet metal-metal-to-ligand charge transfer ((3)MMLCT) emission in the near-infrared (NIR) region. This two-component ensemble has been employed in a "proof-of-principle" concept for the sensitive and selective label-free detection of human serum albumin (HSA) by the emission spectral changes in the visible and in the NIR region. The spectral changes have been ascribed to the disassembly of the polymer-metal complex aggregates upon the binding of PPE-SO(3)(-) to HSA, which is rich in arginine residues and hydrophobic patches, leading to the decrease in FRET from PPE-SO(3)(-) to the aggregated platinum(II) complex. The ensemble is found to have high selectivity toward HSA over a number of polyelectrolytes, proteins and small amino acids. This has been suggested to be a result of the extra stabilization gained from the Pt···Pt and π-π interactions in addition to the electrostatic and hydrophobic interactions found in the polymer-metal complex aggregates.

Aggregation of bis(N-octanoylaminocarboxylato) magnesium(II) complexes in water/organic solvents

Abstracts The aggregation of magnesium(II) complex surfactants of bis( N -octanoylalaninato) (= Mg(oct-ala) 2 ) and bis( N -octanoylphenylalaninato) (= Mg(oct-phe) 2 ) in water/organic solvent (= chloroform, 1-hexanol, and cyclohexanol) mixtures and the effect of water on the aggregation behavior were studied using electric conductivity, NMR spectroscopy, and viscosity. Because of the moderate hydrophile–lipophile balance, Mg(oct-ala) 2 and Mg(oct-phe) 2 form aggregates in hydrophobic organic solvents by encapsulating water which assists the dissolution and aggregation of the metal complexes. A change in the structure from a reverse micelle to an onset of bicontinuous microemulsion in water/1-hexanol or water/cyclohexanol mixed solvent was detected with an increase in the water content. The strong ionic interaction between the magnesium ion and the ligand was reflected in the characteristic aggregation behavior of the magnesium surfactants. Correlation times of the hydration water bound to the metal-complex aggregates in wet chloroform system were determined by the measurements of 2 H 2 O longitudinal relaxation times.

Cationic assembly of metal complex aggregates: structural diversity, solution stability, and magnetic properties.

The tetradentate imino-carboxylate ligand [L](2)(-) chelates the equatorial sites of Ni(II) to give the complex [Ni(L)(MeOH)(2)] in which a Ni(II) center is bound in an octahedral coordination environment with MeOH ligands occupying the axial sites. Lanthanide (Ln) and Group II metal ions (M) template the aggregation of six [Ni(L)] fragments into the octahedral cage aggregates (M[Ni(L)](6))(x)(+) (1: M = Sr(II); x = 2,2: M = Ba(II); x = 2, 3: M = La(III); x = 3, 4: M = Ce(III); x = 3, 5: M = Pr(III); x = 3, and 6: M = Nd(III); x = 3). In the presence of Group I cations, however, aggregates composed of the alkali metal-oxide cations template various cage compounds. Thus, Na(+) forms the trigonal bipyramidal [Na(5)O](3+) core within a tricapped trigonal prismatic [Ni(L)](9) aggregate to give ((Na(5)O) subset [Ni(L)](9)(MeOH)(3))(BF(4))(2).OH.CH(3)OH, 7. Li(+) and Na(+) together form a mixed Li(+)/Na(+) core comprising distorted trigonal bipyramidal [Na(3)Li(2)O](3+) within an approximately anti-square prismatic [Ni(L)](8) cage in ((Na(3)Li(2)O) subset [Ni(L)](8)(CH(3)OH)(1.3)(BF(4))(0.7))(BF(4))(2.3).(CH(3)OH)(2.75).(C(4)H(10)O)(0.5), 8, while in the presence of Li(+), a tetrahedral [Li(4)O](2+) core within a hexanuclear open cage [Ni(L)](6) in ((Li(4)O) subset [Ni(L)](6)(CH(3)OH)(3))2ClO(4).1.85CH(3)OH, 9, is produced. In the presence of H(2)O, the Cs(+) cation induces the aggregation of the [Ni(L)(H(2)O)(2)] monomer to give the cluster Cs(2)[Ni(L)(H(2)O)(2)](6).2I.4CH(3)OH.5.25H(2)O, 10. Analysis by electronic spectroscopy and mass spectrometry indicates that in solution the trend in stability follows the order 1-6 > 7 > 8 approximately 9. Magnetic susceptibility data indicate that there is net antiferromagnetic exchange between magnetic centers within the cages.

SANS STUDY OF AGGREGATION OF THE COMPLEXES FORMED BY SELECTED METAL CATIONS AND P,P'-DI(2-ETHYLHEXYL) ETHANE- AND BUTANE-DIPHOSPHONIC ACIDS*

ABSTRACT The aggregation of several metal complexes formed during solvent extraction with P,P'-di(2-ethylhexyl) ethanediphosphonic acid, H2DEH[EDP], and by P,P'-di(2-ethylhexyl) butanediphosphorac acid, H2DEH[BuDP], in deuterated toluene, has been investigated by small angle neutron scattering (SANS). With H2DEH[EDP], the extraction of Ca(II), La(IH) and U(VT) does not disrupt the cyclic hexameric structure of the ligand in solution. Fe(III) and Th(IV) complexes of H2DEH[EDP], on the other hand, exhibit a very modest tendency to aggregate but only at very high metal loading in the organic phase. With H2DEH[BuDP], the extraction of Ca(H), La(III), U(VI) and Th(IV) is not accompanied by significant aggregation of the metal complexes The Fe(HI)-H2DEH[BuDP] complexes, however, form long cylindrical aggregates similar to those previously observed with P,P'di(2-ethylhexyl) methanediphosphonic acid, H2DEH[MDP]. The aggregation behavior of the various metal-extractant species is discussed in light of the information obtained from earlier solvent extraction, vapor pressure osmometry, and infrared spectroscopy studies.