Ion pair charge-transfer complexes between anionic and cationic metal-dithiolenes [M(II) = Pd,Pt

New [M(R(2)pipdt)(2)](BF(4))(2) salts [R(2)pipdt = N,N'-dialkyl-piperazine-2,3-dithione; M = Pd(II), R = Me and M = Pt(II), R = Me, Et, Pr(i)] bearing redox-active cationic dithiolene complexes have been prepared and characterized. These cations react with the redox-active [M(mnt)(2)](2-) [M = Pd(II), Pt(II); mnt = maleonitrile-2,3-dithiolate] anionic dithiolenes to form salts describable as ion pair charge-transfer complexes. X-ray crystallographic studies have shown that [M(Me(2)pipdt)(2)][M(mnt)(2)] complexes, with M = Pd(II) and Pt(II), are isomorphous. Crystal data of the Pt salt (3a): triclinic, Ponemacr; (No. 2); Z = 1; T = 293(2) K; a = 6.784(7) A, b = 8.460(6) A, c = 13.510(5) A, alpha = 100.63(2) degrees, beta = 104.04(2) degrees, gamma = 96.90(2) degrees; R1 = 0.0691 [wR2 = 0.2187 (all data)]. Structural data show that approximately square-planar [Pt(Me(2)pipdt)(2)] dications and regular square-planar [Pt(mnt)(2)] dianions form an infinite anion-cation one-dimensional stack along axis a with a Pt...Pt a/2 distance of 3.392 A and a Pt...Pt...Pt angle of 180 degrees. Anions and cations arrange themselves face-to-face so as to take on a staggered arrangement. These salts exhibit strong absorptions in the visible-near-infrared region assigned to ion pair charge-transfer transitions. A relation between the optical and thermal electron transfer in the solid state is obtained using a "Marcus-Hush model", and a solid-state electrical conductivity in agreement with expectations is observed. Vibrational spectroscopy is in agreement with the existence of charge-transfer interactions between the cationic and anionic components of the salts.     

DFT investigation of structural, electronic, and catalytic properties of diiron complexes related to the [2Fe](H) subcluster of Fe-only hydrogenases

Hydrogenases catalyze the reversible oxidation of dihydrogen to protons and electrons. The structures of two Fe-only hydrogenases have been recently reported [Peters, J. W.; Lanzilotta, W. N.; Lemon, B. J.; Seefeldt, L. C. Science 1998, 282, 1853-1858. Nicolet, Y.; Piras, C.; Legrand, P.; Hatchikian, E. C.; Fontecilla-Camps, J. C. Structure 1999, 7, 13-23], showing that the likely site of dihydrogen activation is the so-called [2Fe](H) cluster, where each Fe ion is coordinated by CO and CN(-) ligands and the two metals are bridged by a chelating S-X(3)-S ligand. Moreover, the presence of a water molecule coordinated to the distal Fe2 center suggested that the Fe2 atom could be a suitable site for binding and activation of H(2). In this contribution, we report a density functional theory investigation of the structural and electronic properties of complexes derived from the [(CO)(CH(3)S)(CN)Fe(II)(mu-PDT)Fe(II)(CO)(2)(CN)](-1) species, which is related to the [2Fe](H) cluster observed in Fe-only hydrogenases. Our results show that the structure of the [2Fe](H) cluster observed in the enzyme does not correspond to a stable form of the isolated cluster, in the absence of the protein. As a consequence, the reactivity of [(CO)(CH(3)S)(CN)Fe(II)(mu-PDT)Fe(II)(CO)(2)(CN)](-1) derivatives in solution may be expected to be quite different from that of the active site of Fe-only hydrogenases. In fact, the most favorable path for H(2) activation involves the two metal atoms and one of the bridging S atoms and is associated with a very low activation energy (5.3 kcal mol(-1)). The relevance of these observations for the catalytic properties of Fe-only hydrogenases is discussed in light of available experimental and theoretical data.     

Sodium congener of the classical lithium methylchromate dimer: synthetic, X-ray crystallographic, and magnetic studies of Me8Cr2[Na(OEt2)]4

One of the milestone structures in the development of transition-metal complexes with metal-metal bonds of multiple bond order was the lithium methylchromate dimer Me(8)Cr(2)[Li(donor)](4) (donor = THF or Et(2)O). Using a simple salt metathesis reaction mixing this compound with sodium tert-butoxide, the sodium congener Me(8)Cr(2)[Na(OEt(2))](4) has been synthesized as a green crystalline compound and isolated in 51% yield. Its solid-state structure was determined by single-crystal X-ray diffraction. Exhibiting exact crystallographic C(4h) symmetry, this heavier alkali-metal chromate structure is also dimeric, formally comprising a (Me(8)Cr(4))(4-) tetranionic core with four peripheral Na(+) cations carrying supporting ether ligands. Its salient feature is the long Cr···Cr distance of 3.263(2) ?, which is remarkably elongated compared to that in the lithium THF-solvated congener [1.968(2) ?]. With respect to the methyl C atoms, the Cr coordination is distorted-square-planar. Each Na(+) interacts with four methyl C atoms, and there are also some short Na···H(C) contacts. Unlike for lithium chromate, no NMR spectroscopic data could be obtained for sodium chromate. The paramagnetic character of sodium chromate was confirmed by variable-temperature magnetization measurements, which indicated antiferromagnetic behavior.     

Hybrid organo-inorganic clay with nonionic interlayers. mid- and near-IR spectroscopic studies

The intercalation of organic polymers molecules (i.e., PEGs and BRIJ) into a standard Ca-montmorillonite has been studied by XRD, TG, and IR spectroscopy. The polymer intercalation is confirmed by the increasing of the d(001) in XRD spectra as well as by the complex multisteps thermal decomposition behavior of the organo-clay materials. Mid-IR and diffuse reflectance near-IR spectra of the intercalated materials show the polymer diagnostic bands (CH stretching and deformation mode), shifted or changed in shape by the interaction with the clay matrix. Both PEG 1500 and PEG 4000 based materials are likely intercalated in an extended configuration, similar to the amorphous polymer form. BRIJ intercalated polymer spectra suggest the disordered conformation of the alkilic chain in a prevailing "gauche", poorly packed, conformation. Host montmorillonite IR bands, mainly OH and water stretching and deformation fundamentals, combination, and overtone bands, are reduced in intensity by polymer intercalation, pointing out an interaction, likely through H-bonding and/or a possible substitution of cations hydration water molecules.     

A molecular clip throws new light on the complexes formed by a family of cyclam-cored dendrimers with Zn(II) ions. Efficient energy transfer in the heteroleptic complexes

Complexation of Zn(II) ions by cyclam cored dendrimers appended with four (G0), eight (G1) and 16 naphthyl chromophores (G2) at the periphery have been investigated in CH?CN-CH?Cl? 1?:?1 (v/v) solution by absorption and emission, ESI-mass and 1H NMR spectroscopy. The results obtained can be interpreted by the formation of complexes of 2?:?1 dendrimer to metal stoichiometry, at low metal ion concentration, and 1?:?1 complexes upon further addition of Zn(II) ions, for all the dendrimer generations. Upon addition of a molecular clip C2? consisting of two anthracene sidewalls bridged by a benzene group with two sulfate substituents in the para positions, heteroleptic complexes of general formula [GnZnC] are formed. Interestingly, in these complexes, a very efficient quenching (practically 100%) of the dendrimer naphthyl luminescence and sensitization (ca. 90%) of the clip anthracene emission take place. The complex [G2ZnC] exhibits a very high molar absorption coefficient in the UV spectral region owing to the 16 naphthyl chromophores of the dendrimer and the two anthracene units of the clip (ε = 1.7 × 10? M?1 cm?1 at 263 nm). Furthermore, the excitation energy absorbed by the naphthyl chromophores is efficiently funneled to the two anthracene units of the clip, which emits in the blue spectral region.     

Structural and spectroscopic investigation of ZnS nanoparticles grown in quaternary reverse micelles

ZnS nanoparticles were synthesized in four component "water in oil" microemulsions formed by a cationic surfactant (cetyltrimethylammonium bromide, CTAB), a cosurfactant (pentanol or butanol), n-hexane and water. The effect of various parameters (nature of cosurfactant, water/surfactant W(0), and alcohol/surfactant P(0)) on the formation and stability of ZnS nanoparticles was investigated thoroughly. UV-Vis spectroscopy was employed to directly follow the formation of ZnS systems in the microemulsions. Thus, particle size was estimated from the position of the first excitonic transition by employing an approximate finite-depth equation and an empirical correlation, giving average diameters in the ranges 2.3-2.5 and 3.0-3.5nm, respectively. Stable ZnS nanoparticles were obtained by employing low water and high cosurfactant amounts. This suggests that at high concentration the cosurfactant molecules act as capping agents on the surface of the inverse micelles, while low water amounts are needful to obtain water droplets with a radius close to that of the interfacial film spontaneous curvature. HRTEM analysis showed that the samples are formed by a few crystalline ZnS nanoparticles of spherical shape, embedded in and amorphous organic matrix, with a coherent scattering domain between 2 and 4nm.     

Mediterranean diet in a Sicilian student population. Second part: breakfast and its nutritional profile

Abstract

Breakfast habits affect the nutritional status and health of people, in particular children and adolescents. This is the second part a previous study about the adherence to the Mediterranean diet in a Sicilian (Italy) student population. The investigation analysed both normal weight and overweight subjects in order to understand how eating habits, number of meals and daily calorie intakes could affect their body mass indexes (BMI). The aim of this second part was to analyse the breakfast nutritional profiles of this student population. The results highlighted that breakfast was regularly consumed by a percentage ranging from a maximum of 84% (in normal subjects) to a minimum value of 57.4% (in overweight/obese students). Milk, yoghurt, sugar, bread/rusk and tea contributed as main foods to the breakfast composition. The results highlighted that subjects who consumed breakfast showed lower BMI values with significant differences between normal and overweight/obese students.     

From a Medicinal Mushroom Blend a Direct Anticancer Effect on Triple-Negative Breast Cancer: A Preclinical Study on Lung Metastases

Bioactive metabolites isolated from medicinal mushrooms (MM) used as supportive treatment in conventional oncology have recently gained interest. Acting as anticancer agents, they interfere with tumor cells and microenvironment (TME), disturbing cancer development/progression. Nonetheless, their action mechanisms still need to be elucidated. Recently, using a 4T1 triple-negative mouse BC model, we demonstrated that supplementation with Micotherapy U-Care, a MM blend, produced a striking reduction of lung metastases density/number, paralleled by decreased inflammation and oxidative stress both in TME and metastases, together with QoL amelioration. We hypothesized that these effects could be due to either a direct anticancer effect and/or to a secondary/indirect impact of Micotherapy U-Care on systemic inflammation/immunomodulation. To address this question, we presently focused on apoptosis/proliferation, investigating specific molecules, i.e., PARP1, p53, BAX, Bcl2, and PCNA, whose critical role in BC is well recognized. We revealed that Micotherapy U-Care is effective to influence balance between cell death and proliferation, which appeared strictly interconnected and inversely related (p53/Bax vs. Bcl2/PARP1/PCNA expression trends). MM blend displayed a direct effect, with different efficacy extent on cancer cells and TME, forcing tumor cells to apoptosis. Yet again, this study supports the potential of MM extracts, as adjuvant supplement in the TNBC management.     

Amino-carboxylic recognition on surfaces: from 2D to 2D + 1 nano-architectures

The control of the electronic properties of the interfaces between small organic molecules and the substrate is key for the development of efficient and reliable organic-based devices. A promising and widely covered route is to interpose a Self-Assembled Monolayer (SAM) to bridge the molecular film and the electrode. The morphology and the electronic level alignment of the triple substrate-SAM-organic layered system can be tuned by properly selecting the SAM composition. We have recently proposed a novel approach to the problem where, under ultra-high vacuum conditions, a molecular film is anchored to the SAM by exploiting the recognition between molecules functionalized, respectively, with -NH(2) and -COOH end-groups. Here we briefly review the role of the amino-carboxylic interaction in the formation of ordered organic 2-dimensional architectures on solid surfaces. We then describe the anchoring process of carboxylic molecules on amine based SAMs we have recently reported on. New results are presented showing how multiple anchoring sites per molecule may be exploited for tailoring the molecular orientation as well as the density of the anchored molecules.     

Influence of Cyclodextrins on the Kinetics of Oxidation of Amino Acids and BSA by Hydrazyl Radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin.