Self-Assembly of a Hierarchical Metal-Organic Framework at the Liquid/Liquid Interface via π-π Stacking Manipulations in Organoplatinum(IV) Complexes for Methanol Fuel Cells.

This study focuses on the facile synthesis of the hierarchical architecture of zeolitic imidazolate framework-8 (ZIF-8) films containing an ultrasmall amount of Pt(0) by investigating the synthesis of different organoplatinum complexes and manipulating the π-π stacking effect in these complexes at the liquid/liquid interface. The organometallic Pt(IV) precursors were complexes with a formula of [PtXMe2(R)(bpy)] (bpy = 2,2'-bipyridine; for complex 2, R = CH2CH═CHC6H5 and X = Br; for complex 3, R = CH2CH═CH2 and X = Br; for complex 4, R = Me and X = I) prepared by oxidative addition of cinnamyl bromide, allyl bromide, or methyl iodide to [PtMe2(bpy)] (complex 1). Different thin films were synthesized starting from three organometallic Pt(IV) precursors (i) by reduction of the Pt complexes at the toluene/water interface (TF2-TF4), (ii) by encapsulation of the Pt precursors in a ZIF-8 (TF5-TF7), and (iii) by reduction of the Pt precursors onto a ZIF-8 (TF8-TF10). The self-assembly of ZIF-8 and different organoplatinum precursors at the interface of two immiscible liquids leads to the preparation of films with well-engineered structures such as rhombic dodecahedra, nanorods, hierarchical architectures, and nanowires, which are very difficult and complicated to synthesize under normal conditions. The ultralow loading of platinum complexes with different degrees of π-π stacking of dangling moieties has a great impact on the structure and morphology (directing agent), which in turn drastically changes the catalytic properties. The obtained films were applied as electrocatalysts for methanol oxidation in fuel cells. The electrocatalytic performance of organoplatinum containing a cinnamyl group in hierarchical architecture TF8 was found to be superior to those of nonhierarchical structures.

Description of a Non-Canonical AsPt Blue Species Originating from the Aerobic Oxidation of AP-1 in Aqueous Solution.

The peculiar behavior of arsenoplatin-1, ([Pt(µ-NHC(CH3)O)2ClAs(OH)2], AP-1), in aqueous solution and the progressive appearance of a characteristic and intense blue color led us to carry out a more extensive investigation to determine the nature of this elusive chemical species, which we named "AsPt blue". A multi-technique approach was therefore implemented to describe the processes involved in the formation of AsPt blue, and some characteristic features of this intriguing species were revealed.

Dynamic Motions of Ligands around the Metal Centers Afford a Fidget Spinner-Type AIE Luminogen.

A new type of aggregation-induced emission (AIE) luminogen containing a dimeric metal fragment and two or three phthalazine ligands is described, which shows dynamic motions of ligands around the metal centers in solution. Based on the variable-temperature and EXSY NMR spectroscopy data, X-ray crystallography structures, and computational results, three different pathways (i.e., reversible exchange with haptotropic shifts, circulation of ligands around the dimeric metal fragment, and walking on the spot of ligands on the metal centers) were considered for this dynamic behavior. Restriction of these dynamic processes in the aggregate forms of the compounds (in H2O/CH3CN solvent mixtures) contributes to their AIE. DFT calculations and NMR analysis showed that bright excited states for these molecules are not localized on isolated molecules, and the emission of them stemmed from π-dimers or π-oligomers. The morphologies and the mode of associations in the solvent mixtures were determined by using transmission electron microscopy (TEM) and concentration-dependent NMR spectroscopy. The computational results showed the presence of a conical intersection (CI) between the S0 and S1 excited state, which provides an accessible pathway for nonradiative decay in these systems.

Non-Targeted Spectranomics for the Early Detection of Xylella fastidiosa Infection in Asymptomatic Olive Trees, cv. Cellina di Nardò.

Olive quick decline syndrome (OQDS) is a disease that has been seriously affecting olive trees in southern Italy since around 2009. During the disease, caused by Xylella fastidiosa subsp. pauca sequence type ST53 (Xf), the flow of water and nutrients within the trees is significantly compromised. Initially, infected trees may not show any symptoms, making early detection challenging. In this study, young artificially infected plants of the susceptible cultivar Cellina di Nardò were grown in a controlled environment and co-inoculated with additional xylem-inhabiting fungi. Asymptomatic leaves of olive plants at an early stage of infection were collected and analyzed using nuclear magnetic resonance (NMR), hyperspectral reflectance (HSR), and chemometrics. The application of a spectranomic approach contributed to shedding light on the relationship between the presence of specific hydrosoluble metabolites and the optical properties of both asymptomatic Xf-infected and non-infected olive leaves. Significant correlations between wavebands located in the range of 530-560 nm and 1380-1470 nm, and the following metabolites were found to be indicative of Xf infection: malic acid, fructose, sucrose, oleuropein derivatives, and formic acid. This information is the key to the development of HSR-based sensors capable of early detection of Xf infections in olive trees.

Synthesis of a light-responsive platinum curcumin complex, chemical and biological investigations and delivery to tumor cells by means of polymeric nanoparticles.

Platinum-based anticancer drugs are common in chemotherapy, but problems such as systemic toxicity and acquired resistance of some tumors hamper their clinical applications and therapeutic efficacy. It is necessary to synthesize Pt-based drugs and explore strategies to reduce side effects and improve pharmacokinetic profiles. Photo-responsive chemotherapeutics have emerged as an alternative strategy against several cancers, as photoactivation offers spatial selectivity and fewer side effects. Here, we combine chemical synthesis and nanotechnology to create a multifunctional platinum drug delivery system based on the novel metal complex [Pt(ppy)(curc)] (ppy = deprotonated 2-phenylpyridine, curc = deprotonated curcumin)] embodying the naturally occurring bioactive molecule, curcumin. The ultrasonication method coupled with the layer-by-layer technology was employed to produce nanocolloids, which demonstrated a good biocompatibility, higher solubility in aqueous solution, stability, large drug loading, and good biological activity in comparison with the free drug. In vitro release experiments revealed that the polymeric nanoformulation is relatively stable under physiological conditions (pH = 7.4 and 37 °C) but sensitive to acidic environments (pH = 5.6 and 37 °C) which would trigger the release of the loaded drug. Our approach modifies the bioavailability of this Pt-based drug increasing its therapeutic action in terms of both cytotoxic and anti-metastasis effects.

Acetate ion addition to and exchange in (1,5-cyclooctadiene)rhodium(I) acetate: relevance for the coagulation of carboxylic acid-functionalized shells of core-crosslinked micelle latexes.

The solution behavior of complex [Rh(COD)(µ-OAc)]2 in the absence and presence of PPN+OAc- in dichloromethane has been investigated in detail by multinuclear NMR spectroscopy. Without additional acetate ions, the compound shows dynamic behavior at room temperature, consistent with an inversion of its C2v structure. Addition of PPN+OAc- reveals an equilibrated generation of [Rh(COD)(OAc)2]-. Rapid exchange is observed at room temperature between the neutral dimer and the anionic mononuclear complex, as well as between the anionic complex and free acetate. Lowering the temperature to 213 K freezes the exchange between the two Rh complexes, but fast exchange between the anionic Rh complex and free acetate maintains coalesced Me (1H and 13C) and COO (13C) NMR resonances. DFT calculations support the experimental data and lean in favour of a dissociative mechanism for the acetate exchange in [Rh(COD)(OAc)2]-. The acetate ligands in complex [Rh(COD)(µ-OAc)]2 are also exchanged in a biphasic (water/organic) system with the methacrylic acid (MAA) functions of hydrosoluble [MMA0.5-co-PEOMA0.5]30 copolymer chains (PEOMA = poly(ethylene oxide) methyl ether methacrylate), resulting in transfer of the Rh complex to the aqueous phase. Exchange with the MAA functions in the same polymer equally takes place for the chloride ligands of [Rh(COD)(µ-Cl)]2. The latter phenomenon rationalizes the coagulation of a core-crosslinked micelle (CCM) latex, where MMA functions are present on the hydrophilic CCM shell, when a dichloromethane solution of [Rh(COD)(µ-Cl)]2 is added.

Raman, WAXS, and Solid-State NMR Characterizations of Regenerated Silk Fibroin Using Lanthanide Ions as Chaotropic Agents.

Bombyx mori silk fibroin (SF) has been reported as a convenient natural material for regenerative medicine, optoelectronics, and many other technological applications. SF owes its unique features to the hierarchical organization of the fibers. Many efforts have been made to set up protocols for dissolution since many applications of SF are based on regenerated solutions and fibers, but chaotropic conditions required to disassemble the packing of the polymer afford solutions with poor crystalline behavior. Our previous research has disclosed a dissolution and regeneration process of highly crystalline fibers involving lanthanide ions as chaotropic agents, demonstrating that each lanthanide has its own unique interaction with SF. Herein, we report elucidation of the structure of Ln-SF fibers by the combined use of Raman spectroscopy, wide-angle X-ray scattering (WAXS), and solid-state NMR techniques. Raman spectra confirmed the coordination of metal ions to SF, WAXS results highlighted the crystalline content of fibers, and solid-state NMR enabled the assessment of different ratios of secondary structures in the protein.

Direct Observations of Ordered Nanoporosity in Deprotonated 2-(Acetoacetoxy)ethyl Methacrylate (AAEMA-) Polymer: Preliminary Results.

Polymers based on 2-(acetoacetoxy)ethyl methacrylate, charged with iron or sodium, were thermally heated at 150 °C. Both polymers were studied and characterized by SEM, TEM, STEM microscopy and SAEDF techniques. The morphological investigation revealed that, upon heating, both polymers were endowed with microholes, sometimes perfectly ordered, whose dimensions varied from 4-5 nm to approximately 500 nm. In the case of an Fe-containing copolymer, unexpectedly, iron did not fill in the cavities, thus implying that it was "dispersed" in the polymeric matrix. Electronic microdiffraction documented that both polymers exhibited a proto-crystallinity, likely induced by thermal heating.

Exploring the xylem-sap to unravel biological features of Xylella fastidiosa subspecies pauca ST53 in immune, resistant and susceptible crop species through metabolomics and in vitro studies.

Xylella fastidiosa subsp. pauca ST53 (Xfp) is a pathogenic bacterium causing one of the most severe plant diseases currently threatening the olive-growing areas of the Mediterranean, the Olive Quick Decline Syndrome (OQDS). The majority of the olive cultivars upon infections more or less rapidly develop severe desiccation phenomena, while few are resistant (e.g. Leccino and FS17), being less impacted by the infections. The present study contributes to elucidating the basis of the resistance phenomenon by investigating the influence of the composition of the xylem sap of plant species on the rate of bacterial multiplication. Xylem saps from Xfp host and non-host species were used for growing the bacterium in vitro, monitoring bacterial growth, biofilm formation, and the expression of specific genes. Moreover, species-specific metabolites, such as mannitol, quinic acid, tartaric acid, and choline were identified by non-targeted NMR-based metabolomic analysis in olive, grapevine, and citrus. In general, the xylem saps of immune species, including grapevine and citrus, were richer in amino acids, organic acids, and glucose. The results showed greater bacterial growth in the olive cultivar notoriously susceptible to Xfp (Cellina di Nardò), compared to that recorded in the resistant cultivar Leccino. Conversely, higher biofilm formation occurred in Leccino compared to Cellina di Nardò. Using the xylem saps of two Xfp-immune species (citrus and grapevine), a divergent bacterial behavior was recorded: low planktonic growth and biofilm production were detected in citrus compared to the grapevine. A parallel evaluation of the expression of 15 genes showed that Xfp directs its molecular functions mainly to virulence. Overall, the results gained through this multidisciplinary study contribute to extending the knowledge on the host-pathogen interaction, while confirming that the host response and resistance mechanism have a multifactorial basis, most likely with a cumulative effect on the phenotype.

Improved identification of pollution source attribution by using PAH ratios combined with multivariate statistics.

Polycyclic aromatic hydrocarbons (PAHs) are contaminants introduced by different pathways in the marine ecosystem, affecting both aquatic and sediment bodies. Identification of their sources is of vital importance for protecting the marine ecosystem. The attribution of the pollution sources is usually made by using diagnostic molecular ratios of PAHs isomers. The reliability of this approach diminishes when PAHs contents are measured far from their original source, for example in water bodies or in bottom sediments. Conventionally the source attribution is based on time consuming univariate methods. In the present work coupling of molecular ratios with advanced supervised statistical techniques was used to increase the accuracy of the PAH source attribution in bottom sediments. Data on PAHs distribution within 5 port areas, with known pattern port activity, were collected. Evaluation of multiple PAHs ratios at once by means of supervised OPLS-DA technique was performed. A robust descriptive and predictive model was set up and successfully validated. The proposed methodology helps identify PAH transport pathways, highlighting interactions between pollution patterns, port activities and coastal land-use supporting decision makers in defining monitoring and mitigation procedures.

A bioprintable gellan gum/lignin hydrogel: a smart and sustainable route for cartilage regeneration.

In this work a hydrogel, based on a blend of two gellan gums with different acyl content embedding lignin (up to 0.4%w/v) and crosslinked with magnesium ions, was developed for cartilage regeneration. The physico-chemical characterizations established that no chemical interaction between lignin and polysaccharides was detected. Lignin achieved up to 80 % of ascorbic acid's radical scavenging activity in vitro on DPPH and ABTS radicals. Viability of hMSC onto hydrogel containing lignin resulted comparable to the lignin-free one (>70 % viable cells, p > 0.05). The presence of lignin improved the hMSC 3D-constructs chondrogenesis, bringing to a significant (p < 0.05) up-regulation of the collagen type II, aggrecan and SOX 9 chondrogenic genes, and conferred bacteriostatic properties to the hydrogel, reducing the proliferation of S. aureus and S. epidermidis. Finally, cellularized 3D-constructs were manufactured via 3D-bioprinting confirming the processability of the formulation as a bioink and its unique biological features for creating a physiological milieu for cell growth.

Low-Intensity Light-Responsive Anticancer Activity of Platinum(II) Complex Nanocolloids on 2D and 3D In Vitro Cancer Cell Model.

This study aimed to evaluate the therapeutic efficacy of low-intensity visible light responsive nanocolloids of a Pt-based drug using a 2D and three-dimensional (3D) in vitro cancer cell model. Biocompatible and biodegradable polymeric nanocolloids, obtained using the ultrasonication method coupled with Layer by Layer technology, were characterized in terms of size (100 ± 20 nm), physical stability, drug loading (78%), and photoactivation through spectroscopy studies. The in vitro biological effects were assessed in terms of efficacy, apoptosis induction, and DNA-Pt adducts formation. Biological experiments were performed both in dark and under visible light irradiation conditions, exploiting the complex photochemical properties. The light-stimuli responsive nanoformulation gave a significant enhancement in drug bioactivity. This allowed us to achieve satisfying results by using nanomolar drug concentration (50 nM), which was ineffective in darkness condition. Furthermore, our nanocolloids were validated in 3D in vitro spheroids using confocal microscopy and cytofluorimetric assay to compare their behavior on culture in 2D monolayers. The obtained results confirmed that these nanocolloids are promising tools for delivering Pt-based drugs.

Reactivity of Cu(I) Nacnac Complexes Toward Polypnictogen Compounds.

The nacnac Cu(I) compound [LCu(MeCN)] (2) (L = [{N(C6H3Me2-2,6)C(Me)}2CH]-) was reacted with complexes containing aromatic cyclo-E5 ([Cp*Fe(η5-E5)], E = P (1a), As (1b), Cp* = η5-C5Me5), cyclo-P4 ([Cp‴Co(η4-P4)] (3), Cp‴ = η5-C5H2tBu3) and cyclo-E3 ligands ([Cp‴Ni(η3-E3)], E = P (4a), As (4b)) yielding the heterometallic complexes [(Cp*Fe)(µ,η5:2-E5)(LCu)] (E = P (5a), As (5b)), [(Cp*Fe)(µ3,η5:2:1-E5)(LCu)2] (E = P (6a), As (6b)), [(Cp‴Co)(µ,η4:2-P4)(LCu)] (7), [(Cp‴Co)(µ3,η4:2:1-P4)(LCu)2] (8), and [(Cp‴Ni)(µ,η3:2-E3)(LCu)] (E = P (9a), As (9b)). These complexes are rare examples of the coordination of a group 11 metal to aromatic cyclo-En (E = P, As; n = 3-5) ligands. All products were comprehensively characterized by crystallographic and spectroscopic methods. Their dynamic behavior in solution was studied by VT (variable-temperature) NMR spectroscopy, and their electronic structures were elucidated by DFT calculations.

Metal-based Heterogeneous Catalysts for One-Pot Synthesis of Secondary Anilines from Nitroarenes and Aldehydes.

Recently, N-substituted anilines have been the object of increasing research interest in the field of organic chemistry due to their role as key intermediates for the synthesis of important compounds such as polymers, dyes, drugs, agrochemicals and pharmaceutical products. Among the various methods reported in literature for the formation of C-N bonds to access secondary anilines, the one-pot reductive amination of aldehydes with nitroarenes is the most interesting procedure, because it allows to obtain diverse N-substituted aryl amines by simple reduction of nitro compounds followed by condensation with aldehydes and subsequent reduction of the imine intermediates. These kinds of tandem reactions are generally catalyzed by transition metal-based catalysts, mainly potentially reusable metal nanoparticles. The rapid growth in the last years in the field of metal-based heterogeneous catalysts for the one-pot reductive amination of aldehydes with nitroarenes demands for a review on the state of the art with a special emphasis on the different kinds of metals used as catalysts and their recyclability features.

Pt(II)-Decorated Covalent Organic Framework for Photocatalytic Difluoroalkylation and Oxidative Cyclization Reactions.

A new covalent organic framework (COF) based on imine bonds was assembled from 2-(4-formylphenyl)-5-formylpyridine and 1,3,6,8-tetrakis(4-aminophenyl)pyrene, which showed an interesting dual-pore structure with high crystallinity. Postmetallation of the COF with Pt occurred selectively at the N donor (imine and pyridyl) in the larger pores. The metallated COF served as an excellent recyclable heterogeneous photocatalyst for decarboxylative difluoroalkylation and oxidative cyclization reactions.

A non-targeted metabolomics study on Xylella fastidiosa infected olive plants grown under controlled conditions.

In the last decade, the bacterial pathogen Xylella fastidiosa has devastated olive trees throughout Apulia region (Southern Italy) in the form of the disease called "Olive Quick Decline Syndrome" (OQDS). This study describes changes in the metabolic profile due to the infection by X. fastidiosa subsp. pauca ST53 in artificially inoculated young olive plants of the susceptible variety Cellina di Nardò. The test plants, grown in a thermo-conditioned greenhouse, were also co-inoculated with some xylem-inhabiting fungi known to largely occur in OQDS-affected trees, in order to partially reproduce field conditions in terms of biotic stress. The investigations were performed by combining NMR spectroscopy and MS spectrometry with a non-targeted approach for the analysis of leaf extracts. Statistical analysis revealed that Xylella-infected plants were characterized by higher amounts of malic acid, formic acid, mannitol, and sucrose than in Xylella-non-infected ones, whereas it revealed slightly lower amounts of oleuropein. Attention was paid to mannitol which may play a central role in sustaining the survival of the olive tree against bacterial infection. This study contributes to describe a set of metabolites playing a possible role as markers in the infections by X. fastidiosa in olive.

Rhodium nanoparticles inside well-defined unimolecular amphiphilic polymeric nanoreactors: synthesis and biphasic hydrogenation catalysis.

Rhodium nanoparticles (Rh NPs) embedded in different amphiphilic core-crosslinked micelle (CCM) latexes (RhNP@CCM) have been synthesized by [RhCl(COD)(TPP@CCM)] reduction with H2 (TPP@CCM = core-anchored triphenylphosphine). The reduction rate depends on temperature, on the presence of base (NEt3) and on the P/Rh ratio. For CCMs with outer shells made of neutral P(MAA-co-PEOMA) copolymer chains (RhNP@CCM-N), the core-generated Rh NPs tend to migrate toward the hydrophilic shell and to agglomerate depending on the P/Rh ratio and core TPP density, whereas the MAA protonation state has a negligible effect. Conversely, CCMs with outer shells made of polycationic P(4VPMe+I-) chains (RhNP@CCM-C) maintain core-confined and well dispersed Rh NPs. All RhNP@CCMs were used as catalytic nanoreactors under aqueous biphasic conditions for acetophenone, styrene and 1-octene hydrogenation. Styrene was efficiently hydrogenated by all systems with high selectivity for vinyl reduction. For acetophenone, competition between benzene ring and carbonyl reduction was observed as well as a limited access to the catalytic sites when using CCM-C. Neat 1-octene was also converted, but the activity increased when the substrate was diluted in 1-nonanol, which is a better core-swelling solvent. Whereas the molecular RhI center was more active than the Rh0 NPs in 1-octene hydrogenation, the opposite trend was observed for styrene hydrogenation. Although Rh NP migration and agglomeration occurred for RhNP@CCM-N, even at high P/Rh, the NPs remained core-confined for RhNP@CCM-C, but only when toluene rather than diethyl ether was used for product extraction before recycling.

Recent Advances in Catalysis Involving Bidentate N-Heterocyclic Carbene Ligands.

Since the discovery of persistent carbenes by the isolation of 1,3-di-l-adamantylimidazol-2-ylidene by Arduengo and coworkers, we witnessed a fast growth in the design and applications of this class of ligands and their metal complexes. Modular synthesis and ease of electronic and steric adjustability made this class of sigma donors highly popular among chemists. While the nature of the metal-carbon bond in transition metal complexes bearing N-heterocyclic carbenes (NHCs) is predominantly considered to be neutral sigma or dative bonds, the strength of the bond is highly dependent on the energy match between the highest occupied molecular orbital (HOMO) of the NHC ligand and that of the metal ion. Because of their versatility, the coordination chemistry of NHC ligands with was explored with almost all transition metal ions. Other than the transition metals, NHCs are also capable of establishing a chemical bond with the main group elements. The advances in the catalytic applications of the NHC ligands linked with a second tether are discussed. For clarity, more frequently targeted catalytic reactions are considered first. Carbon-carbon coupling reactions, transfer hydrogenation of alkenes and carbonyl compounds, ketone hydrosilylation, and chiral catalysis are among highly popular reactions. Areas where the efficacy of the NHC based catalytic systems were explored to a lesser extent include CO2 reduction, C-H borylation, alkyl amination, and hydroamination reactions. Furthermore, the synthesis and applications of transition metal complexes are covered.

NHCs as Neutral Donors towards Polyphosphorus Complexes.

The first adducts of NHCs (=N-heterocyclic carbenes) with aromatic polyphosphorus complexes are reported. The reactions of [Cp*Fe(η5 -P5 )] (1) (Cp*=pentamethyl-cyclopentadienyl) with IMe (=1,3,4,5-tetramethylimidazolin-2-ylidene), IMes (=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene) and IDipp (=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) led to the corresponding neutral adducts which can be isolated in the solid state. However, in solution, they quickly undergo a dissociative equilibrium between the adduct and 1 including the corresponding NHC. The equilibrium is influenced by the bulkiness of the NHC. [Cp''Ta(CO)2 (η4 -P4 )] (Cp''=1,3-di-tert-butylcyclopentadienyl) reacts with IMe under P atom abstraction to give an unprecedented cyclo-P3 -containing anionic tantalum complex. DFT calculations shed light onto the energetics of the reaction pathways.

PtSn Nanoalloy Thin Films as Anode Catalysts in Methanol Fuel Cells.

Reactions of SnX2 (X = Cl, Br) with [PtMe2(bipy)], 1, (bipy = 2,2'-bipyridine), followed by NaBH4 reduction at the toluene/water interface in the presence or absence of graphene oxide support rendered PtSn nanoalloy thin films. They were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrocatalytical activity of the PtSn thin films was investigated in the methanol oxidation reaction. Our studies showed that the PtSn/reduced-graphene oxide (RGO) thin film gave better catalytic results for MOR in comparison to bare PtSn or Pt thin films. A maximum jf/jb ratio (jf and jb are the maximum current densities in the forward and backward scans, respectively) of 6.77 was obtained for the PtSn/RGO thin film deriving from the 1 + SnBr2 + NaBH4 sequence.