Ligand Size Research Articles

Tuning the void volume in a series of isomorphic porous metal–organic frameworks by varying the solvent size and length of organic ligands

A series of isomorphic metal–organic frameworks, namely, [Cd3(IN)4(N3)2(DMA)2]·2DMA (1), [Cd3(IN)4(N3)2(NMP)2]·2NMP (2), [Cd3(IN)4(N3)2(DMI)2]·2DMI (3), [Cd3(TP)4(N3)2(DMA)2]·4DMA·H2O (4), [Cd3(TP)4(N3)2(NMP)2]·4NMP·H2O (5), and [Cd3(TP)4(N3)2(DMI)2]·4DMI (6), where HIN = isonicotinic acid and HTP = 4-tetrazole pyridine, have been synthesized via solvothermal reaction with Cd(NO3)2·4H2O in three different solvents [N,N-dimethylacetamide (DMA), N-methylpyrrolidinone (NMP), and 1,3-dimethyl-2-imidazolidinone (DMI)]. Single-crystal X-ray structure analysis reveals that compounds 1–6 show three-dimensional (3D) 6-connected nets with channels based on trinuclear cadmium clusters. The coordinated and lattice solvent molecules occupy the free void spaces of the channels. Induced by different solvent molecules, the solvent-accessible volumes of these MOFs are 3 > 2 > 1 and 6 > 5 > 4, which is consistent with the sizes of solvents (DMI > NMP > DMA). By comparing 1–3 with 4–6, the longer organic anion is beneficial to construct MOFs with larger porous sizes and higher solvent-accessible volumes.

Interaction of classical platinum agents with the monomeric and dimeric Atox1 proteins: a molecular dynamics simulation study.

We carried out molecular dynamics simulations and free energy calculations for a series of binary and ternary models of the cisplatin, transplatin and oxaliplatin agents binding to a monomeric Atox1 protein and a dimeric Atox1 protein to investigate their interaction mechanisms. All three platinum agents could respectively combine with the monomeric Atox1 protein and the dimeric Atox1 protein to form a stable binary and ternary complex due to the covalent interaction of the platinum center with the Atox1 protein. The results suggested that the extra interaction from the oxaliplatin ligand–Atox1 protein interface increases its affinity only for the OxaliPt + Atox1 model. The binding of the oxaliplatin agent to the Atox1 protein might cause larger deformation of the protein than those of the cisplatin and transplatin agents due to the larger size of the oxaliplatin ligand. However, the extra interactions to facilitate the stabilities of the ternary CisPt + 2Atox1 and OxaliPt + 2Atox1 models come from the α1 helices and α2-β4 loops of the Atox1 protein–Atox1 protein interface due to the cis conformation of the platinum agents. The combinations of two Atox1 proteins in an asymmetric way in the three ternary models were analyzed. These investigations might provide detailed information for understanding the interaction mechanism of the platinum agents binding to the Atox1 protein in the cytoplasm.

H/D exchange at sp3 carbons in the coordination sphere of platinum(ii)

The [PtCl(η(1)-CH2CH2OR)(Me2phen)], Me2phen = 2,9-dimethyl-1,10-phenanthroline, complex is indefinitely stable in the solid state; however, when dissolved in protic deuterated solvents at basic pH, it undergoes H-D exchange at the Me2phen Me's. An analogous H-D exchange process takes place in the related [PtCl2(Me2phen)] complex which is sterically strained and very easily can detach one nitrogen of Me2phen yielding a T-shaped species. In contrast, the H-D exchange is considerably slower in the [Pt(OR)2(Me2phen)] complex characterized by smaller size and lower trans-labilizing effect of the oxygen donor ligands. It is suggested that the formation of a T-shaped intermediate could foster the C-H activation via oxidative addition to the metal centre. In accord with this hypothesis, the H/D exchange was found to be considerably slower in analogous complexes with 6,6'-dimethyl-2,2'-bipyridyl (Me2bpy), where the greater flexibility of Me2bpy, as compared to Me2phen, reduces the strain in the four coordinate substrate and hence the propensity to dissociate one end of the bidentate ligand.

Ligand Effects on the Hydrogenation of Biomass‐Inspired Substrates with Bifunctional Ru, Ir, and Rh Complexes

We herein report on the application and structural investigation of a new set of complexes that contain bidentate N-heterocyclic carbenes (NHCs) and primary amine moieties of the type [M(arene)Cl(L)] [M=Ru, Ir, or Rh; arene=p-cymene or pentamethylcyclopentadienyl; L=1-(2-aminophenyl)-3-(n-alkyl)imidazol-2-ylidine]. These complexes were tested and compared in the hydrogenation of acetophenone with hydrogen. Structural variations in the chelate ring size of the heteroditopic ligand revealed that smaller chelate ring sizes in combination with ring conjugation in the ligand are beneficial for the activity of this type of catalyst, favoring an inner-sphere coordination pathway. Additionally, increasing the steric bulk of the alkyl substituent on the NHC aided the reaction, showing almost no induction period and formation of a more active catalyst for the n-butyl complex relative to complexes with smaller Me and Et substituents. As is common in hydrogenation reactions, the activity of the complexes decreases in the order Ru>Ir>Rh. The application of [Ru(p-cym)Cl(L)]PF6 , which outperforms its reported analogues, has been successfully extended to the hydrogenation of more challenging biomass-inspired substrates.

Temperature-Programmed Electrospray–Differential Mobility Analysis for Characterization of Ligated Nanoparticles in Complex Media

An electrospray-differential mobility analyzer (ES-DMA) was operated with an aerosol flow-mode, temperature-programmed approach to enhance its ability to characterize the particle size distributions (PSDs) of nanoscale particles (NPs) in the presence of adsorbed and free ligands. Titanium dioxide NPs (TiO2-NPs) stabilized by citric acid (CA) or bovine serum albumin (BSA) were utilized as representative systems. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry were used to provide visual information and elemental-based PSDs, respectively. Results show that the interference resulting from electrospray-dried nonvolatile salt residual nanoscale particles (S-NPs) could be effectively reduced using the thermal treatment process: PSDs were accurately measured at temperatures above 200 °C for CA-stabilized TiO2-NPs and above 400 °C for BSA-stabilized TiO2-NPs. Moreover, TEM confirmed the volumetric shrinkage of S-NPs due to thermal treatment and also showed that the primary structure of TiO2-NPs was relatively stable over the temperature range studied (i.e., below 700 °C). Conversely, the shape factor for TiO2-NPs decreased after treatment above 500 °C, possibly due to a change in the secondary (aggregate) structure. S-NPs from BSA-stabilized TiO2-NPs exhibited higher global activation energies toward induced volumetric shrinkage than those of CA-stabilized TiO2-NPs, suggesting that activation energy is dependent on ligand size. This prototype study demonstrates the efficacy of using ES-DMA coupled with thermal treatment for characterizing the physical state of NPs, even in a complex medium (e.g., containing plasma proteins) and in the presence of particle agglomerates induced by interaction with binding ligands.

Probing Dense Packed Limits of a Hyperbranched Polymer through Ligand Binding and Size Selective Catalysis

In the area of dendritic chemistry (hyperbranched polymers and dendrimers) it is often generalized that dendrimers are the molecule of choice for smart, selective, or technical applications involving encapsulation or controlled/selective environments. This is despite the fact that hyperbranched polymers (HBP)s are generally easier and cheaper to synthesize, making them more amenable to large-scale applications. Dendrimers have been successful in these applications by virtue of a dense packed or dense shell limit. This paper describes the synthesis of a series of narrowly dispersed HBPs possessing binding and catalytic cores with a high and uniform loading. Subsequent binding experiments clearly demonstrated the existence of a dense packed limit with respect to polymer molecular weight and ligand size. A series of catalytic experiments were also performed in an attempt to exploit these molecules and their dense packed limit to the area of shape/size selective catalysis—an area where dendrimers have previou...

Theoretical Analysis of the Influence of Chelate-Ring Size and Vicinal Effects on Electronic Circular Dichroism Spectra of Cobalt(III) EDDA-Type Complexes

To assess the contributions of configurational and vicinal effects as well as chelate-ring size to rotational strengths, the geometries of a series of cobalt(III) complexes [Co(EDDA-type)(L)](±) with the tetradentate EDDA-type ligands, EDDA (ethylenediamine-N,N'-diacetate), DMEDDA (N,N'-dimethylethylenediamine-N,N'-diacetate), DEEDDA (N,N'-diethylethylenediamine-N,N'-diacetate), and a bidentate ancillary ligand L (L = ethylenediamine, oxalate, carbonate, (S)-alanine, and malonate) in aqueous solution have been optimized at the DFT/B3LYP/6-311++G(2d,p) level of theory. Based on the optimized geometries, the excitation energies and oscillator and rotational strengths have been calculated using the time-dependent density functional theory (TDDFT) method with the same functional and basis set. The calculated circular dichroism (CD) curves are in excellent agreement with the observed ones except for some small red or blue shifts in peak wavelengths. For the influence of chelate-ring size of the bidentate ligands on the CD intensities, a qualitative analysis together with the quantitative TDDFT calculation reveal that it depends on the symmetry of the cobalt-EDDA backbone. For the s-cis-isomers, the influence is negligible due to the perturbation is symmetric. For the uns-cis-isomers, the perturbation is unsymmetric. Since a small ring size means a large perturbation, this leads to the integral CD intensities decreasing with increasing the chelate ring size. The vicinal effects of asymmetric nitrogens incorporate both the substitutent effects and conformational relaxation effects, with the former being dominant. By analyzing the contributions of chiral arrays to rotational strengths, we found that the part of contributions dominated by the S-type chiral nitrogens could be considered as a good measure for the vicinal effects of chiral nitrogens. In addition, we found that the twist form (δ/λ) of the backbone ethylenediamine ring (E-ring) of the coordinated EDDA-type ligands is a key factor to understand the properties of these chelates, because it not only dominates the relative stabilities of the s-cis-Λ(SS)-diastereoisomers with the result that λ > δ but also affects the major CD band by changing the order of the first two transitions. Moreover, the twist angle of E-ring is inversely related to the vicinal effect of chiral nitrogens. These findings may help us to understand the chelate ring size as well as vicinal effect related chiroptical phenomenon of the cobalt EDDA-type chelates.

Formation of conglomerate crystals: A closer look at helical pitches and unit cell volumes of P- and M-helical copper(II) coordination polymers

Conglomerate crystals of tubular helical coordination polymers, P- and M-[CuCl2(L)(S)]·S′ (L=dimethylbis(4-pyridyl)silane; S=Me2SO, HCONMe2; S′=Me2SO, 1/2Et2O), have been obtained in high yields. Their helical pitches and unit cell volumes are sensitive to the molecular size of ligand, co-ligand, and solvate molecules. Both crystals evaporate solvate molecules at around 100°C, and then calcination at 600°C finally produces micro-sized chaotic surface materials consisting of copper(II) oxide/silicon(IV) oxide composite with evolving burned organics.

Atomic-layer deposition of thin titanium dioxide films from tetramethoxytitanium and water

Comparative analysis of atomic-layer deposition of titanium dioxide in precursor systems Ti(OCH3)4-H2O and Ti(OC2H5)4-H2O demonstrated that the growth rate of titanium dioxide produced by atomic-layer deposition in the Ti(OCH3)4-H2O system can be adequately estimated using a model taking into account the number and size of ligands in the metal-containing precursor. Studies in simulated body fluids demonstrated that polycrystalline anatase TiO2 coatings are capable of accelerated osteointegration, which makes this precursor promising for development of new biomedical articles.

Structural Tailoring Effects on the Magnetic Behavior of Symmetric and Asymmetric Cubane‐Type Ni complexes

Using two kinds of carboxylate ligands with small but significant differences in steric size, symmetric and asymmetric Fe(II) and Ni(II) cubanes have been synthesized in a controlled fashion. Fast sweeping pulsed field measurements showed magnetization hysteresis loops for two cubane-type molecular complexes, [Ni4(μ-OMe)4(O2CAr(4F-Ph))4(HOMe)8] and [Ni4(μ-OMe)4(O2CAr(Tol))4(HOMe)6], thus suggesting single-molecule magnet behavior. To differentiate the magnetic properties between the symmetric and asymmetric cubanes, detailed electron paramagnetic resonance (EPR) measurements were performed. From the EPR data, taken at various frequencies and temperatures, zero-field splitting parameters D, E, and other higher-order parameters for both cubane samples were extracted. Compared to the symmetric Ni-cubane, the asymmetric one shows an increase in the D and E values by about 20%, thereby suggesting structural engineering effects on the magnetic properties. By using the magnetic parameters determined by EPR, a static magnetization curve at 2 K and a temperature dependence of the magnetic susceptibility were simulated. A good agreement between theoretical and experimental data confirms the validity of the values obtained from EPR measurements.

Heavy metal adsorbents mercapto and amino functionalized palygorskite: Preparation and characterization

Palygorskite was functionalized by mercapto and amino groups respectively in the high-speed shear process based on the rheological properties to enhance its sorption amounts and selectivity for heavy metals. The mercapto and amino functionalized samples were characterized through solid-state 29Si CP/MAS NMR, TEM, SEM, TG, XRD, surface area analysis and zeta potentials. The surface modification took place in the high-speed shear process between the silanol groups of palygorskite and organosilanes. The reaction produced a continuous coating of individual fibers of palygorskite. The crystal structure of palygorskite did not change significantly after surface modification. The isoelectric points shifted to lower pH values and the surface areas decreased due to the bulk size of the functional ligands. The sorption of Pb2+, Cd2+ and Cu2+ on the samples was studied in batch experiments and it was found that the surface modification could obviously increase the sorption capacities for Pb2+, Cd2+ and Cu2+. The mercapto and amino functionalized palygorskite could provide a potential remedy for heavy metal contamination in aqueous environment.

Atomic layer deposition of thin films of titanium dioxide from titanium tetramethoxide and water

The atomic layer deposition of titanium oxide in the precursor systems Ti(OCH3)4-H2O and Ti(OC2H5)4-H2O was compared. The growth rate of titanium oxide formed by the atomic layer deposition in the Ti(OCH3)4-H2O system can be adequately estimated with due to regard for the number and size of ligands of a metal-containing precursor. The study in simulated body fluid solutions showed that polycrystallin TiO2 coatings with anatase structure are prone to accelerated osseointegration and, consequently, promising for the development of new biomedical products.

Control formation of rigid linear and flexible zig-zig complexes based on Zn(II) and hydroxyquinoline carboxylate ligand system

Abstract Two novel zinc complexes, [Zn(H-hqc)2(bpy)(H2O)2] (1) and [Zn(H-hqc)2(bpe)]∙H2O (2), where H2-hqc = 2-hydroxyquinoline-4-carboxylic acid, bpy = 4,4′-bipyridine and bpe = 1,2-bi(4-pyridyl)ethylene, have been prepared under hydrothermal condition. Complex 1 displays a 1D rigid linear chain structure while complex 2 displays 1D flexible zig-zag chain structure. Coordination number of the central Zn ion in complex 1 is six and in complex 2 is four. The structural differences of these complexes suggest the effect of size of the bridging ligands on the construction of metal organic frameworks with the same metal ion under solvothermal conditions.

Optimizing Protein Coordination to Quantum Dots with Designer Peptidyl Linkers

Semiconductor quantum dots (QDs) demonstrate select optical properties that make them of particular use in biological imaging and biosensing. Controlled attachment of biomolecules such as proteins to the QD surface is thus critically necessary for development of these functional nanobiomaterials. QD surface coatings such as poly(ethylene glycol) impart colloidal stability to the QDs, making them usable in physiological environments, but can impede attachment of proteins due to steric interactions. While this problem is being partially addressed through the development of more compact QD ligands, here we present an alternative and complementary approach to this issue by engineering rigid peptidyl linkers that can be appended onto almost all expressed proteins. The linkers are specifically designed to extend a terminal polyhistidine sequence out from the globular protein structure and penetrate the QD ligand coating to enhance binding by metal-affinity driven coordination. α-Helical linkers of two lengths terminating in either a single or triple hexahistidine motif were fused onto a single-domain antibody; these were then self-assembled onto QDs to create a model immunosensor system targeted against the biothreat agent ricin. We utilized this system to systematically evaluate the peptidyl linker design in functional assays using QDs stabilized with four different types of coating ligands including poly(ethylene glycol). We show that increased linker length, but surprisingly not added histidines, can improve protein to QD attachment and sensor performance despite the surface ligand size with both custom and commercial QD preparations. Implications for these findings on the development of QD-based biosensors are discussed.

Super-Resolution Imaging of IgE Receptor Clustering Initiated by Structurally-Defined Ligands in Rbl Mast Cells

Cross-linking of IgE bound to its receptor, FceRI, by multivalent ligands initiates a transmembrane signaling cascade that activates allergic and inflammatory responses in mast cells. Super-resolution fluorescence localization microscopy is an effective tool for quantitative nanoscale imaging of the distribution and ligand-induced redistribution of FceRI. We use structurally-defined trivalent ligands specific for anti-dinitrophenyl (DNP) IgE, for which the ligand size and valency is precisely controlled, to cross-link IgE-FceRI. These ligands are based on a Y-shaped double-stranded DNA scaffold with DNP groups conjugated to each of the three 5’ ends. The distance between DNP groups is fixed by the length of single-stranded oligonucleotides annealed to form the Y-shaped structure. As described previously for these Yn-DNP3 ligands, (Sil et al., 2007, ACS Chem Biol) some (but not other) cell signaling pathways depend on inter-DNP distances, ranging from 5 – 15 nm, which constrain the proximity of ligand-bound IgE-receptors. We are investigating the organization and dynamics of ligand-induced IgE-receptor clustering to gain new information about interactions of cross-linked IgE-receptors within the membrane that accompany or limit transmembrane signaling. We image fixed and live cells and compare Yn-DNP3 ligands with the heterogeneous ligand, DNP20-BSA. IgE is labeled with a photo-switchable probe and IgE-receptor clustering is quantified in super-resolution images with spatial correlation functions. In living cells, we record single-receptor trajectories, and receptor mobility is monitored in real time through analysis of populations of tracks. Both DNP20-BSA and Y16-DNP3 cause a sharp decrease in mobility upon ligand addition, but produce IgE-receptor clusters that appear distinctive in size and density. Y16-DNP3–stimulated changes occur on a shorter time scale when matched for DNP concentration with DNP20-BSA. Continuing work with Yn-DNP3 ligands will probe clustering-dependent IgE-receptor association with membrane structures and downstream signaling partners.

Stereo- and regioselective cyclopolymerization of chiral 1,7-octadiynes

A series of diastereomeric 4,5-diethoxycarbonyl-1,7-octadiynes were synthesized from which the pure diastereomers were obtained by selective Soxhlet extraction in CHCl3. The concept of “small alkoxides” was used with varying size of the alkoxide ligands and all the monomers were cyclopolymerized with two different Schrock-type initiators. As a result, poly(1,7-octadiyne)s consisting virtually solely of six membered repeat units were obtained via regioselective α-insertion. The structure of the polymers and the regioselectivity of insertion were further confirmed by comparing the 13C NMR shifts of model compounds with those of the corresponding polymers. The living character of the polymerization was demonstrated by kinetic studies and end group analysis via MALDI-ToF MS; diblock copolymers were successfully prepared from 1,7-octadiynes and 1,6-heptadiynes. Finally, the tacticity of the cyclopolymers was elucidated from NMR of poly(1,7-octadiyne) synthesized from 1,7-octadiyne-4,4-dicarboxylic esters containing enantiomerically pure menthyl ester groups. These investigations revealed the formation of highly tactic polymers (>86%) with at least predominantly trans-configured exocyclic double bonds.

POLAROGRAPHIC CHARACTERISTICS AND THERMODYNAMICS APPLIED IN [Cd - L-AMINO ACIDATES - VITAMIN-B7] TERNARY SYSTEM

The present work describes the complexe formation of the Cd (II) with amino acids (L-glutamine, L-asparagine, L-valine, L-leucine, α-alanine and glycine) as primary ligands and vitamin-B7 (β-biotin) as secondary ligand by polarographic technique. The Cd (II) formed 1: 1: 1, 1: 1: 2 and 1: 2: 1 complexes at pH = 7.30 ± 0.01, µ = 1.0 M KNO 3 . The Cd (II) showed the two electrons reversible reduction wave with diffusion controlled nature. The trend of the stability constants of the complexes with respect to primary ligand was L-glutamine < L-asparagine < L-valine < L-leucine < α-alanine < L-glycine. The thermodynamic parameters like enthalpy, free energy, and entropy change is also determined. The results showed that the complexes were lesser stable at high temperature and formed with the evolution of heat. 1-3 . The minerals mis-regulation leads to many serious diseases such as oxidative stress diabetes, amyotrophic lateral sclerosis, cancer, inflammatory, neurodegenerative, and potential to various toxic effects etc. 4-10 . In addition to these, toxic effects are reduced with the ligands therapy. The bioactive amino acids and vitamin-B7 complexes with the Cd (II) are also used to prevent excess metal accumulation and toxicity 11 . Amino acid side chain groups are involved in various biological functions such as the molecular recognition and catalytic activity of the enzyme active center and formation of an environment with the metal ions used to in medicinal fields 12 . Weak interactions involving functional groups of coordinated amino acids in metal complexes may mimic the modes and effects of the interactions in metalloproteins. Complexes of amino acids and vitamins with metal ions have great importance because of their physiological and pharmacological activities. Some of the research work reported antitumor activities 13-14 . Biotin is act as cofactor and coenzyme involved in vital biological process such as fatty acid synthesis, gluconeogenesis, amino acids metabolism, and carbon dioxide fixation reaction 15 . Therefore the combination of the amino acids and vitamin-B7 with Cd (II) are used to reduce the metal toxicity. The coordination chemistry of the Cd (II) metal ion has shown too significant for the organisms on complexation with the bioactive ligands by chelating nitrogen and oxygen donor ligands 16 . In the present work, we report the complex formation between Cd 2+ and some L-amino acids and β-biotin with the aim to ascertain the effects of size and basicity of ligand on the stability of complexes.

Error estimates for (semi-)empirical dispersion terms and large biomacromolecules

The first-principles modeling of biomaterials has made tremendous advances over the last few years with the ongoing growth of computing power and impressive developments in the application of density functional theory (DFT) codes to large systems. One important step forward was the development of dispersion corrections for DFT methods, which account for the otherwise neglected dispersive van der Waals (vdW) interactions. Approaches at different levels of theory exist, with the most often used (semi-)empirical ones based on pair-wise interatomic C6R(-6) terms. Similar terms are now also used in connection with semiempirical QM (SQM) methods and density functional tight binding methods (SCC-DFTB). Their basic structure equals the attractive term in Lennard-Jones potentials, common to most force field approaches, but they usually use some type of cutoff function to make the mixing of the (long-range) dispersion term with the already existing (short-range) dispersion and exchange-repulsion effects from the electronic structure theory methods possible. All these dispersion approximations were found to perform accurately for smaller systems, but error estimates for larger systems are very rare and completely missing for really large biomolecules. We derive such estimates for the dispersion terms of DFT, SQM and MM methods using error statistics for smaller systems and dispersion contribution estimates for the PDBbind database of protein-ligand interactions. We find that dispersion terms will usually not be a limiting factor for reaching chemical accuracy, though some force fields and large ligand sizes are problematic.

Water exchange on beryllium complexes: part VIII – influence of neutral electron pair donors

In this article, water exchange reactions on [Be(L)(H2O)3]2+ (L = NH3− x (CH3) x , PH3− x (CH3) x , AsH3− x (CH3) x , OH2− x (CH3) x , SH2− x (CH3) x , SeH2− x (CH3) x , pyridine, 4-fluoropyridine, 4-bromopyridine, 4-chloropyridine, 4-hydroxypyridine, 4-thiolopyridine, 4-selenidopyridine, 4-nitrilopyridine, 1,4-diazine, 1,3,5-triazine, HCN, acetonitrile, and benzonitrile) are examined, utilizing the B3LYP//6-311 + G** density functional for geometry optimizations, and B3LYP//6-311 + G** both with and without the CPCM solvent model as well as MP2(full)//6-311 + G** for subsequent single-point energy calculations. In all examined cases, the results prove that these complexes show associative interchange mechanisms for water exchange. With the exception of the NH x (CH3)3− x series of ligands, activation energy barriers vary little, making these ligands mostly spectator ligands. Geometrical parameters vary mainly with the ligand size.

PEG-Stabilized Core–Shell Nanoparticles: Impact of Linear versus Dendritic Polymer Shell Architecture on Colloidal Properties and the Reversibility of Temperature-Induced Aggregation

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely used experimentally and also clinically tested in diverse areas of biology and medicine. Applications include magnetic resonance imaging, cell sorting, drug delivery, and hyperthermia. Physicochemical surface properties are particularly relevant in the context of achieving high colloidal nanoparticle (NP) stability and preventing agglomeration (particularly challenging in biological fluids), increasing blood circulation time, and possibly targeting specific cells or tissues through the presentation of bioligands. Traditionally, NP surfaces are sterically stabilized with hydrophilic polymeric matrices, such as dextran or linear poly(ethylene glycol) brushes. While dendrimers have found applications as drug carriers, dispersants with dendritic ("dendrons") or hyperbranched structures have been comparatively neglected despite their unique properties, such as a precisely defined molecular structure and the ability to present biofunctionalities at high density at the NP periphery. This work covers the synthesis of SPIONs and their stabilization based on poly(ethylene glycol) (PEG) and oligo(ethylene glycol) (OEG) chemistry and compares the physicochemical properties of NPs stabilized with linear and dendritic macromolecules of comparable molecular weight. The results highlight the impact of the polymeric interface architecture on solubility, colloidal stability, hydrodynamic radius, and thermoresponsive behavior. Dendron-stabilized NPs were found to provide excellent colloidal stability, despite a smaller hydrodynamic radius and lower degree of soft shell hydration compared to linear PEG analogues. Moreover, for the same grafting density and molecular weight of the stabilizers, OEG dendron-stabilized NPs show a reversible temperature-induced aggregation behavior, in contrast to the essentially irreversible aggregation and sedimentation observed for the linear PEG analogues. This new class of dendritically stabilized NPs is believed to have a potential for future biomedical and other applications, in which stability, resistance to (or reversible) aggregation, ultrasmall size (for crossing biological barriers or inclusion in responsive artificial membranes), and/or high corona density of (bio)active ligands are key.