[Show abstract][Hide abstract] ABSTRACT: Bilayers of Prussian blue analogues (PBA) constituted of hard and soft magnets have been fabricated by means of electrochemical deposition. This method affords a good contact between two PBA thin films of nanometer thickness. Complete characterization of the resulting system has been performed, which has allowed the determination of the preservation of the chemical identity of both materials during the electrodeposition and the establishment of a clear interface between them. The magnetic behavior of the bilayer can be explained in terms of an exchange-spring magnet.
Full-text · Article · Oct 2015 · Journal of Materials Chemistry C
[Show abstract][Hide abstract] ABSTRACT: Segmented homopolytopic ligands that consist of a rigid central arylene platform, ethynylene spacers, and terminal chelating picolinate subunits have been synthesized in good yields in a two-step procedure involving a Sonogashira-type cross coupling reaction between the ester methyl 5-bromopyridine-2-carboxylate and several arylacetylenes, followed by hydrolysis of the resulting methyl picolinates. A similar strategy has been employed for the preparation of heteroditopic ligands containing picolinate and a second non-chelating pyridine or benzoate unit. The compounds are potential candidates for organic linkers in metal-organic frameworks (MOFs).
No preview · Article · Sep 2015 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: A magneto-optical Kerr effect (MOKE) study has been performed on electrodeposited thin films of the Prussian blue analogue Fe 3 [Cr(CN) 6 ] 2 $15H 2 O (1). This study reveals the onset of hysteretic magnetic signals at temperatures above 60 K, in contrast with magnetic susceptibility measurements which indicate a Curie temperature of 23 K for this ferromagnetic film. The origin of this discrepancy is due to the presence of amorphous iron oxide particles that accumulate in the surface of the material. This report illustrates the potential of MOKE magnetometry for the detection of surface chemical impurities that remain elusive using bulk magnetic techniques.
Full-text · Article · Sep 2013 · The Journal of Physical Chemistry C
[Show abstract][Hide abstract] ABSTRACT: Nanoparticles (NPs) have emerged as a potential tool to improve cancer treatment. Among the proposed uses in imaging and therapy, their use as a drug delivery scaffold has been extensively highlighted. However, there are still some controversial points which need a deeper understanding before clinical application can occur. Here the use of gold nanoparticles (AuNPs) to detoxify the antitumoral agent cisplatin, linked to a nanoparticle via a pH-sensitive coordination bond for endosomal release, is presented. The NP conjugate design has important effects on pharmacokinetics, conjugate evolution and biodistribution and results in an absence of observed toxicity. Besides, AuNPs present unique opportunities as drug delivery scaffolds due to their size and surface tunability. Here we show that cisplatin-induced toxicity is clearly reduced without affecting the therapeutic benefits in mice models. The NPs not only act as carriers, but also protect the drug from deactivation by plasma proteins until conjugates are internalized in cells and cisplatin is released. Additionally, the possibility to track the drug (Pt) and vehicle (Au) separately as a function of organ and time enables a better understanding of how nanocarriers are processed by the organism.
[Show abstract][Hide abstract] ABSTRACT: Therapeutic efficiency and body weight change of short treatment. (a) Differences in tumor volumes measured by caliper after two consecutive injections (day 0 and 3) of 3 and 1.5 mg cisplatin (kg mouse)–1 each of free cisplatin and AuNP–cisplatin, respectively. The antitumor activity of cisplatin was maintained after the drug was conjugated to the AuNPs. Tumor catch-up was also observed. (b) A large body-weight loss was caused by the high dose of free cisplatin (6 mg kg−1). This loss was not observed in the case of AuNPs-cisplatin. However the primary effect was not significantly different in both treatments.
[Show abstract][Hide abstract] ABSTRACT: Confocal microscopy of A549 treated with AuNP-cisplatin. Cells were incubated with AuNP-cisplatin for (a) 30 min, (b) 1 h, (c) 3 h, and (d) 24 h. Afterwards, they were processed by staining nuclear DNA with DAPI, and α-tubulin microtubules with monoclonal mouse anti α-tubulin antibody and goat anti mouse antibody conjugated with Alexa 488. Nanoparticles appear as red dots because of their ability to scatter light . A LEICA TCS SP2 AOBS Spectral Confocal system was used for image processing. There is evidence of internalization with time, and no nanoparticles were observed in the nucleus. Also, as time passes and nanoparticles are processed, deposits of NPs are observed. Some of those extracellular deposits may also occur due to the cell processing for microscopy.
[Show abstract][Hide abstract] ABSTRACT: Different cellular internalization of conjugate and free drug (not drawn to scale). AuNPs-cisplatin are internalized via an endocytic pathway, hence cisplatin is only released at the acidic pH of the endosomes. Moreover AuNPs protect the drug from being deactivated by plasma proteins. Free cisplatin mainly enters via diffusion through the cell membrane. Inside the cytoplasm the interchange of Cl− for H2O molecules takes place and the active drug is then formed.
[Show abstract][Hide abstract] ABSTRACT: Analysis of relevant biochemical markers. Aspartate transaminase (AST) and Alanine transaminase (ALT) levels indicate that there is no evidence of liver dysfunction. The renal function is usually determined by the levels of Blood Urea Nitrogen (BUN) and creatinine. Although the BUN seems to be higher than levels reported in other works , it should be noted that there is no difference between the control and treatment with AuNPs-cisplatin. Total protein and albumin are also indicators of hepatic function.
[Show abstract][Hide abstract] ABSTRACT: Halogen bonds have been applied for the supramolecular
organization of organic free radicals in the solid state and their
role in the propagation of the magnetic exchange has been
[Show abstract][Hide abstract] ABSTRACT: Structural, electronic, and magnetic properties of [Mn12O12(bet)16(EtOH)4](PF6)14·4CH3CN·H2O (in short Mn12bet, bet = betaine = +N(CH3)3-CH2–COO–) single-molecule magnets (SMMs) deposited on previously functionalized gold surfaces have been investigated. Self-assembled monolayers (SAMs) either of sodium mercaptoethanesulfonate (MES) or mercaptopropionic acid (MPA) are used as functionalization to avoid the direct interaction between the Mn12bet molecules and the Au surface with the aim of preserving the main functional properties of the molecules. Scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) analysis show deposited Mn12bet SMMs well-isolated from each other and uniformly distributed on both MES and MPA SAMs. X-ray absorption spectroscopy (XAS) studies show that the oxidation state of the mixed-valence Mn12bet core is largely reduced to Mn2+ when molecules are deposited on MES-SAM, whereas in the case of MPA-SAM the relative weights of Mn2+, Mn3+, and Mn4+ in the Mn12bet core are preserved. Despite the substantial retaining of their electronic properties, the magnetization of Mn12bet molecules deposited on MPA-SAM measured by X-ray magnetic circular dichroism (XMCD) is perturbed with respect to the pristine molecules.
No preview · Article · Jul 2012 · The Journal of Physical Chemistry C
[Show abstract][Hide abstract] ABSTRACT: This paper reports on molecular-based magnetic thin films of Prussian blue analogues (PBA) with high critical temperatures composed of mixed-valence chromium cyanides. The thin films of PBA were synthesized by means of electrodeposition technique. Morphology and magnetic study are presented in a function of electrochemical deposition conditions. We present the electrochemical methods as a promising and effective tool for preparing molecular-based magnetic thin films of Prussian blue analogue.
Full-text · Article · Apr 2012 · Nanoscale Research Letters
[Show abstract][Hide abstract] ABSTRACT: Electrodeposited thin films of the molecule-based magnet Cr 5.5(CN) 12·11.5H 2O exhibit a magneto-optical Kerr effect (MOKE) with large coercive fields at 200 K. As the thickness of the films is reduced to the nanometer scale, the particle size decreases and the magneto-optical hysteresis becomes relatively large.
Full-text · Article · Oct 2011 · Advanced Materials
[Show abstract][Hide abstract] ABSTRACT: The single-molecule magnet Tb(picNN)3·6H2O is a neutral thermodynamically stable homoleptic Tb3+ complex that can be formed upon complexation of the terdentate picolinate-based nitronyl nitroxide free radical picNN. The environment of the tris(chelated) lanthanoid ion is a distorted tricapped trigonal prism, with the O(carboxylate) and O(nitroxide) atoms occupying the trigonal faces and the N(pyridine) atoms sitting in the capping positions. It shows magnetic hysteresis at very low temperatures.
No preview · Article · Aug 2011 · Inorganic Chemistry
[Show abstract][Hide abstract] ABSTRACT: This tutorial review illustrates the design of multifunctional oxalate-based magnetic materials through the combination of the intrinsic magnetism of the metal-organic framework and the additional properties introduced by several organic/inorganic functional cations.
No preview · Article · Feb 2011 · Chemical Society Reviews
[Show abstract][Hide abstract] ABSTRACT: The effect of solvent isotopic replacement (H for D) on the size of gold nanoparticles (Au NPs) prepared by sodium citrate reduction has been investigated. With increasing replacement of water by deuterium oxide, smaller sizes of Au NPs are obtained, which is interpreted as a consequence of a faster reduction. A mechanism in which a substitution complex, [AuCl3(C6H5O7)−2]−, is formed from AuCl4 and citrate ions prior to its rate-limiting disproportionation into products is suggested. This novel procedure offers an attractive alternative to the existing ones and opens a full range of possibilities for biological studies.
Full-text · Article · Jan 2010 · The Journal of Physical Chemistry C
[Show abstract][Hide abstract] ABSTRACT: This paper is divided into two parts: in the first part, the influence of solvate molecules on the magnetic properties of spin crossover salts of [Fe(bpp)(2)][Cr(L)(ox)(2)]ClO(4) x nS (bpp = 2,6-bis(pyrazol-3yl)pyridine; L = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen); ox = oxalate dianion; S = solvent) is analyzed. The second part is devoted to the photomagnetic properties of the previously reported [Fe(bpp)(2)][Cr(L)(ox)(2)](2) family of compounds. The study describes the crystal structure, differential scanning calorimetry (DSC) and magnetic properties of [Fe(bpp)(2)][Cr(bpy)(ox)(2)]ClO(4) x EtOH x 4 H(2)O (1) and [Fe(bpp)(2)][Cr(phen)(ox)(2)]ClO(4) x 1.5 EtOH x 4 H(2)O (2). Both salts are high-spin (HS) compounds. Desolvation of 1 yields a material exhibiting a gradual spin crossover that involves 50% of the Fe(2+) cations. Rehydration of this desolvated salt induces a significant increase in the low-spin (LS) population. Desolvation of 2 affords a material showing a more abrupt spin crossover with thermal hysteresis (T(1/2)(increasing) = 286 K and T(1/2)(decreasing) = 273 K). This material is not very sensitive to rehydration. The anhydrous compounds [Fe(bpp)(2)][Cr(bpy)(ox)(2)](2) (3) and [Fe(bpp)(2)][Cr(phen)(ox)(2)](2) (4) display some quantitative photomagnetic conversion with T(LIESST) values of 41 and 51 K, respectively. Kinetic parameters governing the photo-induced HS-LS relaxation process have been determined and used to reproduce the T(LIESST) curves.
Full-text · Article · Oct 2009 · Dalton Transactions
[Show abstract][Hide abstract] ABSTRACT: The preparation, magnetic characterization, and X-ray structures of two polycationic Mn(12) single-molecule magnets [Mn(12)O(12)(bet)(16)(EtOH)(4)](PF(6))(14).4CH(3)CN.H(2)O (1) and [Mn(12)O(12)(bet)(16)(EtOH)(3)(H(2)O)](PF(6))(13)(OH).6CH(3)CN.EtOH.H(2)O (2) (bet = betaine = (CH(3))(3)N(+)-CH(2)-CO(2)(-)) are reported. 1 crystallizes in the centrosymmetric P2/c space group and presents a (0:2:0:2) arrangement of the EtOH molecules in its structure. 2 crystallizes in the noncentrosymmetric P4 space group with two distinct Mn(12) polycations, [Mn(12)O(12)(bet)(16)(EtOH)(2)(H(2)O)(2)](14+) (2A) and [Mn(12)O(12)(bet)(16)(EtOH)(4)](14+) (2B) per unit cell. 2A and 2B show a (1:1:1:1) distribution of the coordinated solvent molecules. Interestingly, bond valence sum calculations extracted from X-ray diffraction data indicate the presence of two Mn(2+) ions in the Mn(12) core for both 1 and 2. This finding is confirmed by X-ray absorption spectroscopy (XAS) measurements. A complete magnetic characterization, including subkelvin micro-SQUID magnetometry and inelastic neutron scattering (INS) measurements, permits to extract the parameters of the giant spin Hamiltonian of these polycations. Compared with the archetypal Mn(12) acetate, an increase in the value of the ground spin state from S = 10 to S = 11 together with a decrease in the effective energy barrier, is observed for 1 and 2. Such a result is consistent with the reduction of two Mn(3+) to the less anisotropic Mn(2+) ion in the structures.
Full-text · Article · Oct 2009 · Inorganic Chemistry