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Six Fe(II) complexes with substituted 6‐((quinoline‐8‐ylimino)methyl)phenolates (R2qsal) were synthesized. X‐ray crystal structure determination for [Fe(R2qsal)2], where R=F (1), Cl (2), Br (3), I (4), CF3/H (5), or CN/H (6), revealed mononuclear complexes that crystallize either solvent‐free in case of 1, 5, and 6 or as CH2Cl2 solvates in the case of 2, 3, and 4. Complexes 1–4, which contain π‐donating substituents, exhibit only high‐spin (HS) state, as shown by crystal structure analysis and magnetic measurements. In contrast, complexes 5 and 6, which contain electron‐withdrawing substituents, exist in the low‐spin (LS) state at lower temperatures but exhibit crossover to the HS state above 300 K. Electronic structure calculations show a good correlation between the relative energies of the LS and HS states and the experimentally observed behavior. [ABSTRACT FROM AUTHOR]

Strategies to design novel antibacterial materials may rely on the combination of materials to achieve synergistic effects. The coupling of antibacterial peptides to nanoparticles, however, needs to be directed conveniently to avoid structural changes within the peptide and/or degradation of the nanoparticle. Here, we present the results of the attachment of a synthetic peptide (VIHGW-alkyne-G-NH2) containing the amino terminal copper and nickel (ATCUN) motif to silver nanoparticles. In order to direct the peptide-nanoparticle coupling, the peptide was functionalized with an alkyne, whereas the nanoparticles were functionalized with azide groups using thiol-polyethylene glycol-azide (HS-PEG-N3) chains, so that the acetylide and the azide can undergo a click reaction. The reaction was conducted at room temperature and the steps in the construction of the nanoparticle-PEG-ATCUN array were followed by a combination of UV-Vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy. Evidence of the attachment of the PEG molecules through the thiol termination indicates that the nanoparticle is functionalized with azide groups, although only partially. The click reaction with the synthetic peptide is evidenced by the loss of the N3-vibrational signal with infrared spectroscopy. Throughout the steps of the synthesis, the behavior of the nanoparticles was followed by UV-Vis spectroscopy, dynamic light scattering, and zeta potential measurements, observing that during the process there are no significant changes in the size of the nanoparticle and that the stability of the nanoparticles increases. Antibacterial tests, conducted using E. coli, showed that the activity of the Ag-PEG-ATCUN nanocomposites is higher than that of nanoparticles and ATCUN peptides separately. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) are known and widely used for their antibacterial properties. However, the ever-increasing resistance of microorganisms compels the design of novel nanomaterials which are able to surpass their capabilities. Herein, we synthesized silver nanoparticles using, for the first time, polyhydroxy fullerene (PHF) as a reducing and capping agent, through a one-pot synthesis method. The resulting nanoparticles (PHF-AgNPs) were compared to AgNPs that were synthesized using sodium citrate (citrate-AgNPs). They were characterized using high-resolution transmission electron microscopy (HR-TEM), dynamic light scattering, and UV-visible spectroscopy. Our results showed that PHF-AgNPs have a smaller size and a narrower size distribution than citrate-AgNPs, which suggests that PHF may be a better capping agent than citrate. Antibacterial assays using E. coli showed enhanced antimicrobial activity for PHF-AgNPs compared to citrate-AgNPs. The electrocatalytic activity of nanoparticles towards oxygen evolution and reduction reaction (OER and ORR, respectively) was tested through cyclic voltammetry. Both nanoparticles are found to promote OER and ORR, but PHF-AgNPs showed a significant increase in activity with respect to citrate-AgNPs. Thus, our results demonstrate that the properties of forming nanoparticles can be tuned by choosing the appropriate reducing/capping agent. Specifically, this suggests that PHF-AgNPs can find potential applications for both catalytic and biomedical applications. [ABSTRACT FROM AUTHOR]

Nanotechnology and its applications to medicine, known as nanomedicine, involve a wide use of nanomaterials to stimulate and guide the regenerative properties of cells. In particular, tissue regeneration can be promoted by enabling a controlled release of therapeutic agents, which can be done using nanoparticles. In this review article, the fundamentals of tissue regeneration are discussed, focusing on epithelial tissue, to demonstrate the importance of delivering therapeutic agents in an efficient, sustained and localized manner. Then, the methods for synthesizing metallic and polymeric nanoparticles are described. While polymeric nanoparticles can be loaded with an agent during synthesis, metallic nanoparticles must first be synthesized to later interact with therapeutic agents. This interaction can be fine-tuned by functionalizing metallic nanoparticles with organic molecules, which results in a more controlled attachment.This review highlights the importance of choosing the appropriate method of synthesis and functionalization, which must be designed considering both the type of tissue to regenerate and the nature of the agent to be transported. [ABSTRACT FROM AUTHOR]

Homoleptic complexes [Fe(4bt)3](ClO4)2 (1), [Fe(2bt)3](ClO4)2 (2), and [Fe(3tpH)3](ClO4)2 (3) were obtained by a reaction between the Fe(II) precursor salt and the corresponding thiazole-based bidentate ligand (L = 4bt = 4,4′-bithiazole, 2bt = 2,2′-bithiazole, 3tpH = 3-(thiazol-2-yl)pyrazole). X-ray crystal structure determination revealed crystallization of solvent-free complex 1, a solvate 2·MeOH, and a co-crystal 3·2(3tpH). The crystal packing of all these complexes is dominated by one-dimensional interactions between the [Fe(L)3]2+ cations. These interactions are stronger in 2·MeOH and 3·2(3tpH), leading to cooperative and slightly hysteretic transitions between the high-spin and low-spin electronic configurations at ∼235 K and 159 K, respectively. In contrast, weaker intermolecular interactions in 1 result in a gradual spin crossover above 300 K, with the maximum fraction of the HS state ∼25% achieved at 400 K. Complexes 2 and 3·2(3tpH) exhibit light-induced excited spin state trapping (LIESST) under irradiation with white light or a 532 nm laser at 5 K. After the photoexcitation, the trapped metastable HS state relaxes to the ground LS state with the average relaxation temperature of 81 K and 68 K, respectively. Examination of the relaxation dynamics by optical absorption spectroscopy on a single crystal of 3·2(3tpH) revealed the sigmoidal shape of the relaxation curves at lower temperatures, attributed to cooperative effects, as well as a plateau at ∼10% of the HS fraction at intermediate temperatures, hinting at a more complex mechanism for the relaxation of the LIESST phase in this material. [ABSTRACT FROM AUTHOR]