Search

New octahedral rhenium cluster complexes [{Re6Q8}(SO3)6]10- (Q = S or Se) were synthesized starting from [{Re6Q8}(H2O)4(OH)2]·12H2O. The complexes were crystallized as sodium salts and characterized by X-ray single-crystal diffraction and elemental analyses, IR, UV/vis and luminescence spectroscopies. Magnetic relaxation data demonstrate the complex formation of the cluster units with gadolinium ions. The analysis of the magnetic relaxation rates measured at various Gd:cluster ratios and different concentrations revealed the conversion of the aggregates (Gdx[{Re6Se8}(SO3)6]y)n- into a nanoparticulate form even at x = 1 and y ≥ 1. Thus, the self-assembly of the cluster units into the nanoparticles is greatly facilitated by counterion binding with sodium cations. The concentration conditions were optimized for the formation and hydrophilization of NaxGdy[{Re6Q8}(SO3)6]-based colloids with the magnetic relaxivity values of r1(2) = 21.0(24.1) and r1(2) = 25.9(29.8) mM-1 s-1 for the {Re6S8}2+ and {Re6Se8}2+ derivatives, respectively.

The present work introduces a facile synthetic route to embed phosphorescent K2[{Mo6I8}I6] and (nBu4N)2[{Mo6I8}(CH3COO)6] clusters (C) onto silica-water interface of amino-decorated silica nanoparticles (SNs, 60 ± 6 nm). The assembled C-SNs gain in the luminescence intensity, which remains stable within three months after their assembly. High uptake capacity of the clusters (8700 of K2[{Mo6I8}I6] and 6500 of (nBu4N)2[{Mo6I8}(CH3COO)6] per the each nanoparticle) derives from ionic self-assembly and coordination bonds between the cluster complexes and ionic (amino- and siloxy-) groups at the silica surface. The coordination via amino- or siloxy-groups restricts aquation and hydrolysis of the embedded clusters, in comparison with the parent K2[{Mo6I8}I6] and (nBu4N)2[{Mo6I8}(CH3COO)6. High potential of the assembled nanoparticles in the ROS generation was revealed by EPR measurements facilitated by spin trapping. The high positive charge and convenient colloid stability of the assembled C-SNs hybrids are the prerequisite for their efficient cellular uptake, which is exemplified in the work by MCF-7 cell line. The measured dark and photoinduced cytotoxicity of the C-SNs hybrids reveals significant photodynamic therapy effect on the MCF-7 cancer cell line versus the normal cells. This effect is entirely due to the embedded clusters and is dependent on the chemical composition of the cluster.

Cyclic aminomethylphosphines in general and 1,5-diaza-3,7-dihposphacyclooctanes in particular are widely used for the design of d10-metal complexes with catalytic or luminescent properties. 1,5-Dia...

A variety of gold(I) and copper(I) complexes based on heterocyclic phosphine platform has been obtained. Due to the presence of exocyclic chromophoric pyridyl groups in the ligands complexes demonstrate noticeable phosphorescence. Cyclic nature of the phosphine ligands is responsible for supramolecular host-behavior of the complexes. Unique structure of complexes on a scaffold of the cyclic PNNP ligands favors the stimuli-induced structural reorganizations followed by stimuli-responsive luminescence. This, in turn, makes the complexes versatile building blocks for bottom-up design of smart nanomaterials for analytical and biomedical applications.

The present work represents new facile route for synthesis of luminescent hydrophilic core-shell colloids, where the luminescence results from Au(I) complex (AuCl)2L with cyclic PNNP ligand (L). The synthesis is based on solvent mediated aggregation of (AuCl)2L in aqueous organic solutions. Instability of (AuCl)2L in aqueous organic solutions was minimized by specific hydrophilic shell deposition arisen from electrostatically driven adsorption of polyethylenimine onto (AuCl)2L-based cores. Luminescence of the colloids is stable for week at least due to restricted degradation of the luminescent complex at the interface and high positive exterior charge of the colloids. The sensing properties of the colloids towards thiols results from their complex formation with Au+ ions. The thiol-induced stripping of Au+ ions from the colloids quenches the luminescence. The optimal conditions for fluorescent recognition of cysteine, homocysteine and glutathione with lower detection limits about 1 μM are highlighted in the work.

The present work represents interactions between the core-shell nanoparticles and different proteins, exemplified by lysozyme (LSZ), pepsin, bovine serum albumin (BSA), thioredoxin (TRX) and yellow fluorescent protein (YFP). The core-shell morphology derives from the non-covalent deposition of polyethyleneimine (PEI) onto nanoprecipitated luminescent complex (AuCl)2L (L is cyclic PNNP ligand). Analysis of the data obtained by DLS, CD spectroscopy, luminescence derived from both (AuCl)2L and YFP reveal the electrostatically driven interaction of negatively charged proteins with the shell of PEI-(AuCl)2L. The fluorescence of YFP enables to reveal the inclusion of the protein molecules into the shell. The lack of any luminescent response of PEI-(AuCl)2L on TRX conforms its electrostatically driven interactions with the shell which, in turn, excludes a binding of the exposed thiol moieties with (AuCl)2L. The negatively charged surface of pepsin provides the greatest recharging of the PEI-based shell versus the other proteins, which is followed by the enhanced luminescence of (AuCl)2L. The significant effect of PEI-(AuCl)2L on the CD spectra of LSZ followed by the decreased intensity of (AuCl)2L-based luminescence points to specific interaction mode of PEI-(AuCl)2L with LSZ. The flow cytometry and fluorescent microscopy measurements revealed efficient internalization of PEI-(AuCl)2L into the Wi-38 cell samples resulting in the efficient staining of all cell organelles. The concentration dependent cytotoxicity of PEI-(AuCl)2L is detectably enhanced by LSZ, which is correlated with its interaction mode with the nanoparticles.

The present work for the first time introduces PDA-based vesicles as convenient supporters of luminescent water insoluble Tb3+ complexes. The specific cyclophanic structure of the ligands, where upper and lower calix[4]arene rims are decorated by nonyl- and chelating groups correspondingly provides both complex formation with Tb3+ ions with the coordination of the latter via two 1,3-diketonate groups and self- or mixed aggregation of the complexes. The conditions of the self-aggregation of the Tb3+ complexes are revealed, although the self-aggregates are unstable being converted into the nanosized precipitates which tend to further aggregation and phase separation. The complexes exhibit Tb(III)-centered luminescence which tends to change in time following the phase separation processes. The embedding of the Tb3+ complexes into the PDA-based vesicles results in the mixed aggregates with significant Tb(III)-centered luminescence and significant colloidal stability. The latter arises from high negative electrokinetic potential values due to exterior carboxylic/carboxylate groups of the PDA vesicles.

The work introduces facile synthetic route of conversion of Gd(III) complexes with hexanuclear cluster anions [{Re6Q8}(CN)6]4− (Q = S2−, Se2− or Te2−) into colloidal core-shell nanoparticles, where hard cores are the water insoluble Gdx[{Re6Q8}(CN)6]y complexes, hydrophilic shells are built from (PEO)100-(PPO)65-(PEO)100 (F-127). The comparative analysis of TEM and PXRD data for the dried colloids in correlation with the colloidal, luminescence and magnetic relaxation properties of the aqueous colloids indicates that the nature of the cluster anions [{Re6Q8}(CN)6]4− greatly affects the size and crystallinity of the hard cores, which in turn influences both magnetic relaxivity and luminescence of the corresponding aqueous colloids. The analysis of the results revealed hydrophilic colloids based on Gdx[{Re6S8}(CN)6]y as the best ones from the viewpoint of the functional properties, which along with the low cytotoxicity makes them very promising basis for further application as contrast agents in both MRI and luminescent imaging. Keywords: Cluster complex, Gadolinium complex, nanoparticles, Relaxivity, Cytotoxicity, luminescence

The present work introduces synthesis, structure and spectroscopic properties of novel water soluble dicationic binuclear Au(I) complex [Au2L2]2+ with bridge P,P-coordination, where L is cyclic PNNP ligand 1,5-bis(p-tolyl)−3,7-bis(pyridine-2-yl)−1,5-diaza-3,7-diphosphacyclooctane. Its ion-pairing with anionic hexarhenium cluster complexes ([{Re6S8}(OH)6]4– and [{Re6S8}(CN)6]4–) is represented herein as a reason for bottom-up design of supramolecular heterometallic assemblies with the enhanced cluster-centered luminescence and heterometallic colloids with high luminescence response to acidification in the range of pH 6.0-5.5.

The present work introduces Gd3+ complexes with giant keplerate polyanions as a promising basis for MRI contrast agents. The impact of Gd3+ binding with different building blocks of keplerates on the magnetic relaxivity of the complexes is revealed by comparative study of the keplerates [{Mo6O21}12{Mo2O4(OAc)}30]42−, [{Mo6O21}12{Mo2O4(HPO4)}30]72−, and [{Mo6O21}12{Mo2O2S2(OAc)}30]42−. Unprecedentedly high longitudinal and transverse relaxivity values (up to 250 and 300 mM−1 s−1 correspondingly) are achieved for the keplerates possessing edl{Mo2O4(OAc)} and {Mo2O4(HPO42−)} moieties under their 1 : 1 complex formation with Gd3+. The transformation of the external pores from Mo9O9 to Mo9O6S3 in the {Mo2O2S2(OAc)}-keplerate and an increase in the Gd3+-to-keplerate ratio are the factors that decrease the relaxivity. The rapid degradation of the free keplerates in aqueous solutions restricts the use of the Gd3+-bound keplerates with 1 : 1 stoichiometry as MRI contrast agents. In this work, the optimized stoichiometry of the complexes, their self-assembly into ultra-small nanoparticles and their hydrophilic coating by a triblock copolymer are highlighted as tools for increasing both the colloid and chemical stability of the keplerate complexes. Optimal keplerate compositions have been identified to achieve a compromise of low cytotoxicity and high stability; these Gd3+-bound keplerates exhibit longitudinal and transverse relaxivity values (95 and 114 mM−1 s−1, respectively), well within the region of interest for MRI techniques.

The work for the first time highlights the specific nanoparticulate form of hexamolybdenum cluster complexes [{Mo6I8}(L)6]2− with L = CF3COO− and C6F5COO− (Mo6) exhibiting high anticancer potential in the irradiation-free conditions. The diverse nanoparticulate forms developed from the Mo6-units include self-aggregated (Bu4N)2[{Mo6I8}(L)6 (Mo6-aggregates) and those deposited onto the specifically decorated silica nanoparticles (SNs). The chemical and colloid stabilities of the as prepared nanoparticles reveal both Mo6-aggregates and those deposited onto the preliminary hydrophilized by polyethyleneimine (PEI) SNs (Mo6-PEI-SNs) as optimal candidates for biomedical applications. High photodynamic activities of Mo6-aggregates and Mo6-PEI-SNs revealed by the spin trap facilitated ESR technique along with the efficient irradiation-induced cytotoxic effects of both nanoparticulate forms indicate their great potential in photodynamic therapy. However, “dark” cytotoxicity measurements for M−HeLa cancer and Chang Liver normal cell lines revealed significant specific anticancer effect of Mo6-aggregates, but the insignificant one of Mo6-PEI-SNs. Quantitative LysoTracker-facilitated colocalization analysis in lysosomal compartments highlighted the highest lysosomal localization of Mo6-aggregates for L = CF3COO−, to a lesser degree for L = C6F5COO−, for Mo6-PEI-SNs being the lowest. The great anticancer effect of the Mo6-aggregates correlates with their highest localization in lysosomal compartment followed by the enhanced aggregation, in turn, derived from the hydrophobic apical ligands.

The present work introduces an insight into pH- and concentration-dependent binding of branched polyethylenimine (PEI) with hexarhenium hydroxo cluster complex [{Re 6 S 8 }(OH) 6 ] 4− aimed at enhancing the stability, luminescence intensity and cellular uptake of the cluster complex in aqueous solutions at pH 7.4. Luminescence and conductivity measurements revealed pH 7.4 and 1:1 of PEI:cluster molar ratio as specific conditions ensuring multiple electrostatic interactions of protonated amino groups of PEI with the tetra-anionic cluster units. These interactions resulted in a significant supporting effect of PEI on stability and luminescence of the cluster complex, while no effect of the cluster complex on the acid-base and aggregation properties of PEI was detected from dynamic light scattering and 1 H NMR spectroscopy measurements. The cluster luminescence remained without degradation for at least two weeks due to the supporting effect of PEI, which can facilitate the application of the cluster complex in bioimaging. The cellular uptake of [{Re 6 S 8 }(OH) 6 ] 4− and [{Re 6 S 8 }(OH) 6 ] 4− @PEI was investigated. Confocal microscopic studies showed that the pristine cluster complex [{Re 6 S 8 }(OH) 6 ] 4− did not enter cells (the human larynx carcinoma cell line (Hep-2)), whereas the supramolecular assembly [{Re 6 S 8 }(OH) 6 ] 4− @PEI internalized into the cells.

The work introduces for the first time Mo-132-type Keplerates (Kp) and Gd3+ ions as a basis for the one-pot synthesis of aqueous colloids with high longitudinal relaxivity (r1 = 96.4 mM−1 s−1 at 20 MHz). The hydrophilic coating of small (3–5 nm) Gdx(Kp)y-based cores provides their colloid stabilization, protection from degradation and low cytotoxicity.

The present work describes a new method to sense cholinesterase-catalyzed hydrolysis of acetylcholine (ACh) through a luminescence response of the hexarhenium cluster complex [{Re6S8}(OH)6](4-). A proton released from acetylcholinesterase (AChE)- or butyrylcholinesterase (BuChE)-catalyzed hydrolysis of ACh results in time-resolved sensitization of cluster-centered luminescence. The sensitization results from protonation of apical hydroxo-groups of the cluster complex. The protonation is affected by a counter ion effect. Thus, optimal conditions for adequate sensing of acetic acid produced by ACh hydrolysis are highlighted. Time-resolved luminescence and pH measurements under conditions of AChE-catalyzed hydrolysis of ACh show a good correlation between the cluster-centered luminescence and pH-induced inhibition of AChE. The inhibition is not significant within the first two minutes of ACh hydrolysis. Thus, the luminescence response measured within two minutes is dependent on both substrate and enzyme concentrations, which fits with AChE and BuChE kinetics. The usability of cluster-centered luminescence for monitoring the concentration-dependent inhibition of AChE with irreversible inhibitors is demonstrated, using a carbamylating agent, pyridostigmine bromide, as a model.

The work introduces regularities and driving forces of self-assembly of hexarhenium clusters [{Re6S8}L6]n− (L = SO32−, CN−, OH−) with [AgL′]+ (L′ = pyridine-2-ylphospholane) produced by dissociation of [Ag2L′2]2+ in aqueous solutions. The formation of nano-sized Re6 Ag assemblies is detected by the spectral measurements in the solutions and by the solid-state analysis of the separated colloids. The nature of L is highlighted as the main factor affecting the assembly. The poor affinity of the SO32− ligands to Ag+ restricts the assembly of [{Re6S8}(SO3)6]10− with the silver(I) complexes. [{Re6S8}(OH)6]4− is more promising candidate for the heterometallic assembly contributed by both counter-ion binding and coordination bonds, while the efficient coordination of Ag+ via the nitrogen of the cyanide ligands of [{Re6S8}(CN)6]4− is the main driving force for the Re6 Ag assembly. The stronger impact of [Ag2L′2]2+ relative to Ag+ cations on the formation of Re6 Ag assemblies in aqueous solutions, as well as the presence of L′ in the separated colloidal phase, indicate the important role of the L′ ligand in the studied supramolecular systems. The cluster-centered luminescence serves as signaling system at the binding of glutathione, cysteine and dithiothreitol with Ag+ ions of the heterometallic assemblies. The assemblies based on [{Re6S8}(CN)6]4− are able to discriminate glutathione versus cysteine, while the assemblies formed by [{Re6S8}(OH)6]4− give the unselective luminescence response on the both biothiols at the concentration level of 2 μM.

The present work introduces Gd3+ complexes with giant keplerate polyanions as a promising basis for MRI contrast agents. The impact of Gd3+ binding with different building blocks of keplerates on the magnetic relaxivity of the complexes is revealed by comparative study of the keplerates [{Mo6O21}12{Mo2O4(OAc)}30]42-, [{Mo6O21}12{Mo2O4(HPO4)}30]72-, and [{Mo6O21}12{Mo2O2S2(OAc)}30]42-. Unprecedentedly high longitudinal and transverse relaxivity values (up to 250 and 300 mM-1 s-1 correspondingly) are achieved for the keplerates possessing edl{Mo2O4(OAc)} and {Mo2O4(HPO42-)} moieties under their 1 : 1 complex formation with Gd3+. The transformation of the external pores from Mo9O9 to Mo9O6S3 in the {Mo2O2S2(OAc)}-keplerate and an increase in the Gd3+-to-keplerate ratio are the factors that decrease the relaxivity. The rapid degradation of the free keplerates in aqueous solutions restricts the use of the Gd3+-bound keplerates with 1 : 1 stoichiometry as MRI contrast agents. In this work, the optimized stoichiometry of the complexes, their self-assembly into ultra-small nanoparticles and their hydrophilic coating by a triblock copolymer are highlighted as tools for increasing both the colloid and chemical stability of the keplerate complexes. Optimal keplerate compositions have been identified to achieve a compromise of low cytotoxicity and high stability; these Gd3+-bound keplerates exhibit longitudinal and transverse relaxivity values (95 and 114 mM-1 s-1, respectively), well within the region of interest for MRI techniques.

The work introduces a synthesis of novel amphiphilic p-tert-butylphenol derivatives with the polyethyleneoxide and biodegradable ionogenic polyethylenecarbonate moieties. The dependence of their aggregation behaviour on the lengths of polyethyleneoxide and polyethylenecarbonate chains indicates the impact of the hydrophilic moieties and ionogenic end-groups in the aggregation behaviour of the amphiphiles. The micelles of the amphiphiles are negatively charged, although neither pH nor counter ions (exemplified by Gd(III) ions) affects the values of their critical micelle concentrations. The presence of the ionogenic end-groups is the main reason of the pH and concentration dependent extraction of Gd(III) ions from the neutral (pH 6.2-7.2) aqueous solutions of the amphiphiles through their phase separation at room temperatures. The extraction regularities point on the stoichiometric binding of the amphiphilic molecules with Gd(III) ions as the main reason of the phase separation in their aqueous solutions. Nevertheless the micellization of the amphiphiles is responsible for the peculiar concentration effect on the extraction of Gd(III) ions from the aqueous solutions.

The work introduces smart organic-inorganic hybrids with temperature- and substrate-induced quenching and sensitization of hexamolybdenum iodine cluster-centered luminescence based on iodine cluster salt [K(diglyme) (CH3CN)]2[Mo6I14] (1) and triblock copolymer (PEO)13(PPO)30(PEO)13 (L64). Formation of supramolecular assembly of [Mo6I14]2−, K+, and L64 molecules at fixed concentration conditions is manifested by specific cluster-centered luminescence. These supramolecular assemblies exhibit reversible luminescence quenching when temperature or concentration of L64 increases. The temperature-induced reversible aggregation of the L64-based organic-inorganic hybrids is followed by the reversible quenching of the cluster-centered luminescence. The ion-pairing equilibrium between the cluster anions and fluoroquinolones is shifted by the aggregation of the L64-based hybrids, which results in more enhanced quenching of the luminescence. These tendencies provide the route to sense the triblock copolymer-based phase transitions through the response of the cluster-centered luminescence.

The work introduces the temperature induced quenching of Tb(III) and Eu(III) centered luminescence sensitized by ligands 2,2′:6′,2″-terpyridine and difloxacin in aqueous solutions of triblock copolymers, namely (PEO)13(PPO)30(PEO)13 (L64), (PPO)14(PEO)24(PPO)14 (17R4) and (PPO)8(PEO)22(PPO)8 (10R5). The results reveal the temperature induced shifting of the complex formation equilibriums in solutions of the triblock copolymers as the reason of the quenching of Eu(III) and Tb(III) centered luminescence. The correlation between the temperature induced quenching and the aggregation behavior of the triblock copolymers is revealed. Both the nature of the ligand and the architecture of the triblock copolymer affect the Tb(III) and Eu(III) centered luminescence response to the temperature induced phase transitions.

The article introduces transverse relaxation rates of water protons in the aqueous hydrophilic colloids synthesized on the basis of the oleate-coated iron oxide nanoparticles (17 nm) with non-ionic and cationic surfactants, triblock copolymers, polyethyleneimine (PEI) and 4,5-dihydroxybenzene-1,3-disulfoacid disodium salt (Tiron) as hydrophilic components. The IR spectroscopy, atomic force and transmission electron microscopy, along with dynamic light scattering data were obtained to evaluate the content of the hydrophilic coating, the clustering of iron oxide nanoparticles within the hydrophilic covering and the aggregation of hydrophilic nanoclusters. The analysis of the obtained results together with transverse relaxation rates under various concentration, counter-ion and temperature conditions reveals the particular importance of the water molecules diffusion in the outer hydrophilic layer versus the nearest to the iron oxide core layer. The obtained results reveal the counter ion binding with the charged hydrophilic iron oxide colloids as a route to affect the water transverse relaxation rates by biorelevant anionic substrates such as adenosine triphosphates.

The work introduces the supramolecular assembly of triblock copolymers, namely (PEO)13(PPO)30(PEO)13 (L64), (PPO)14(PEO)24(PPO)14 (17R4), (PPO)8(PEO)22(PPO)8 (10R5) and (PEO)21(PPO)67(PEO)21 (P123) with novel cluster complexes [K(diglyme)(CH3CN)]2[Mo6I14] (1) and [K2(diglyme)(CH3CN)5][Mo6I14] (2) as a route to increase their water solubility. Dynamic light scattering and photophysical measurements reveal the decisive influence of the arrangement of PEO and PPO blocks and of their length on both colloidal and photophysical properties of these solutions. ES-MS data reveal [Mo6I14]2− clusters as the predominant form in aqueous solutions of L64 and P123. The steady state and time resolved luminescence data indicate concentration dependent sensitizing of the Mo-centered luminescence through the energy transfer from difloxacin to [Mo6I14]2− mediated by the ion-pairing. The impact of both arrangement and length of PEO and PPO blocks in the luminescent response of [Mo6I14]2− to difloxacin is discussed. The aqueous solutions of L64 at pH 4 provide the optimal conditions for the sensing of difloxacin through the cluster luminescence.

A series of multinuclear Cu(I) complexes (CuI)xLy, namely the previously reported (CuI)6L2 and (CuI)2L′ and novel (CuI)2L2, where L and L′ are 1,5-di(R)-3,7-bis(2-pyridine-2′-yl)ethyl-1,5-diaza-3,7-diphosphacyclooctanes are introduced. Both dissociative and oxidative behavior of the complexes in DMSO and DMF solutions are correlated with the time-dependent changes in their phosphorescence originated from 3(X + M)LCT transitions. The instability of butterfly-like (CuI)2L′ resulting in its oxidative degradation in DMSO and transformation into (CuI)L′2 in DMF solutions differentiates it from more stable linear complexes (CuI)6L2 and (CuI)2L2. The complexes (CuI)2L2 and (CuI)L2 produced by the dissociation of (CuI)6L2.in DMSO and DMF solutions are regarded as structural motifs responsible for both reversible blue-shifting by 10 nm of the emission band and the decrease in the excited states lifetime values upon the heating of the solutions within 293–333 K. This temperature-induced behavior along with the phosphorescence character of the emission of both complexes points to thermally activated delayed fluorescence as the reason for the reversible temperature-induced spectral changes of hexanuclear (CuI)6L2. Smaller nuclearity of (CuI)2L2 is the reason for partial reversibility of the spectral changes.

The present work introduces the optimization of the oxidative degradation, complex formation and aggregation of the water-soluble metal oxide nanostructures (the so-called keplerates) [{W6O21(H2O)5(OAc)0.5}12{Mo2O4(OAc)}30]48− (W72Mo60), [{Mo6O21(H2O)3(SO4)}12(VO)30(H2O)20]26− (Mo72V30), and [{Mo6O21}12Fe30(OAc)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91] (Mo72Fe30) in aqueous solutions containing Gd3+ ions and triblock copolymers, which can be used as a tool to enhance magnetic relaxivity of the gadolinium-bound nanostructures. The particularly significant enhancement in the magnetic relaxivity of the Gd3+ ions bound with W72Mo60 versus Mo72Fe30/V30 is due to the more convenient size of the external pores in the keplerate framework, which are the binding sites for Gd3+ aqua ions. The structure of the W72Mo60 keplerate is also responsible for the high stabilities of its gadolinium complexes against oxidative degradation in the solutions. The aggregation of the gadolinium-bound W72Mo60 keplerates controlled by the Gd:keplerate molar ratio is a factor in addition to the structure affecting the relaxivity. The assembly of the gadolinium-bound keplerates with the triblock copolymers enhances the relaxivity values by limiting the size of the aggregates, while the relaxivity of the molecular complexes is insignificantly affected by the assembly with the triblock copolymers. The gadolinium complexes exhibiting competitively high magnetic relaxivity values, coupled with their high chemical stability and low cytotoxicity, are introduced herein as the result of the structural optimization, both on molecular and supramolecular levels.

The present report is inspired by the idea to develop novel spectroscopy based techniques to detect the phase transitions in solutions of triblock copolymers with the use of Gd(III) and Eu(III) ions as probes. The choice of (PEO)13(PPO)30(PEO)13 (L64), (PPO)14(PEO)24(PPO)14 (17R4), (PPO)8(PEO)22(PPO)8 (10R5) and Triton X-100 is conditioned by their phase transitions occurring in mild conditions. The cloud point extraction (CPE) data reveal the conditions (pH and chelating agent) where the binding of lanthanides with surfactant rich phase of triblock copolymers and Triton X-100 occurs. The effect of phase transitions in solutions of triblock copolymers on the temperature resolved line widths in EPR spectra of Gd(III) aqua ions and transverse relaxation rates of Gd(III) inner-sphere water protons depends on the architecture of triblock copolymers and pH conditions. The steady state luminescence of Eu(III) complexes with phosphine oxide in aqueous solutions of triblock copolymers and TX-100 is influenced by the temperature induced aggregation and phase separation in solutions of reverse triblock copolymers 17R4 and 10R5, while the effect of the aggregation is insignificant for L64.

The present work introduces the interaction of hard and soft colloids in aqueous solutions at various temperatures and concentrations, as well as at critical conditions of temperature induced phase separation. Hard and soft colloids are represented by luminescent silica nanoparticles and aggregates of PEO–PPO–PEO and PPO–PEO–PPO triblock copolymers correspondingly. The formation of the mixed aggregates between hard and soft colloids in equilibrium conditions has been revealed by dynamic light scattering measurements. The distribution of silica nanoparticles between aqueous and surfactant rich phases after phase separation highlights the effect of pH, architecture and concentration of triblock copolymers on the mixed hard–soft colloids aggregation at cloud point conditions. The peculiar aggregation and phase behavior of PPO–PEO–PPO pluronics should be assumed as the main reason of the enhanced mixed aggregation with SNs at increased temperatures and concentrated conditions.

Aggregation and cloud point (CP) behavior, as well as CP extraction of lanthanide ions have been studied for novel non-ionic cyclophanic surfactants with the varied length of polyoxyethylene and hydrophobic moieties (CnEm) based on calix[4]arene platform in their mixtures with Triton X100 (TX100). The dynamic light scattering data reveal the contribution of the large size lamellar or stack like mixed aggregates in CnEm–TX100 solutions. Aggregation and CP behavior of TX100–CnEm mixed solutions are quite different from those of conventional non-ionic surfactants. The effect of the hydrophobic substituents and polyoxyethylene chains length of CnEm on the CP extraction of La(III), Gd(III) and Lu(III) in the mixed TX100–CnEm micellar solutions is discussed in the correlation with their aggregation and cloud point behavior. The obtained data elucidate the cyclophanic structure of CnEm as the key reason of the formation of large lamellar-like aggregates with TX100, exhibiting the unusual CP behavior and CPE efficiency.

Two amphiphilic water-soluble sulfonatomethylated calix[4]resorcinarene derivatives were studied by various 1H NMR techniques (1H NMR titration, 2D NOESY, NMR diffusion measurements). The derivative with methyl moieties at the lower rim (1) was found to be non-aggregated in the range 0–10 mM in aqueous solutions. Lengthening of the lower rim substituent to pentyl (2) results in self-aggregation of 2 in aqueous solutions with the aggregation number varying from 3 at 1 mM to 20 at 10 mM. The 2D NOESY 1H NMR spectroscopy data reveal an unusual head-to-tail packing mode in aqueous solutions, resulting from the cooperative effect of weak hydrophobic interactions. Binding of guests (tetramethylammonium and N-methylpyridinium) results in additional stabilization of the aggregates whilst the head-to-tail packing mode of the aggregate is retained.

The aggregation and cloud point behavior of Tb(III)-doped silica nanoparticles has been studied in Triton X-100 (TX-100) solutions at various concentration conditions by fluorimetry, dynamic light scattering, electrophoresis and transmission electron microscopy methods. The temperature responsive behavior of nanoparticles is observed at definite concentration of TX-100, where the aggregation of TX-100 at the silica/water interface is evident from the increased size of the silica nanoparticles. The reversible dehydration of TX-100 aggregates at the silica/water interface should be assumed as the main reason of the temperature induced phase separation of silica nanoparticles. The distribution of nanoparticles between aqueous and surfactant rich phases at the phase separation conditions can be modified by the effect of additives.

Here we report the clouding phenomenon, conductivity, (1)H NMR spectroscopy and dynamic light scattering data of mixed sodium dodecylsulfate-calix[4]resorcinarene micellar solutions in combination with tetrabutyl-, tetraethyl-, tetramethylammonium bromides and choline chloride. The NMR data reveal tight (the binding constant is about 10(4)) guest-host binding of calix[4]resorcinarene in alkaline conditions with tetraethyl-, tetramethylammonium and choline cations. This binding occurs at rather small concentrations of the external quaternary salts (0-0.0005 M) and leads to dramatic increase of the cloud point temperature. The obtained data are discussed in the correlation with the micellar size changes, caused by the ion exchange due to the variation of quaternary salt concentrations.

The use of water-soluble calixarenes: p-sulfonato thiacalixarene (ST), tetra-sulfonatomethylated calix[4]resorcinarene (SR), calix[4]resorcinarene phosphonic acid (PhR) as chelating agents in cloud point extraction (CPE) of La(III), Gd(III) and Yb(III) ions using Triton X-100 as non-ionic surfactant is introduced. The data obtained indicate that both complexation ability and structure of calixarenes govern the extraction efficiency of lanthanides. In particular ST and SR, forming 1:1 lanthanide complexes with similar stability in aqueous media, exhibit different extractability when used as chelating agents in CPE. First synthesized PhR was found to be the most efficient chelating agent exhibiting pH-dependent selectivity within La(III), Gd(III) and Yb(III) in CPE.