4,2-Ribbon like ferromagnetic cyano-bridged Fe(III)2Ni(II) chains: a magneto-structural study

The low-spin iron(III) complex AsPh(4)[Fe(III)(bpy)(CN)(4)].CH(3)CN (1) [AsPh(4) = tetraphenylarsonium cation] and the heterobimetallic chains [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)].4H(2)O with L = bpy (2) and phen (3) [bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline] have been prepared and their structures determined by X-ray diffraction methods. The structure of 1 consists of mononuclear [Fe(bpy)(CN)(4)](-) anions, tetraphenylarsonium cations and acetonitrile molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of the bidentate bpy and four carbon atoms of four terminal cyanide groups building a distorted octahedral surrounding around the metal atom. 2 and 3 are isomorphous compounds whose structure is made up of neutral 4,2-ribbon like bimetallic chains of formula [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)] where the [Fe(III)(L)(CN)(4)](-) unit acts as a bis-monodentate bridging ligand toward the trans-diaquanickel(II) units through two of its four cyanide groups in cis positions. The chains exhibit two orientations in the unit cell and they interact with each other through hydrogen bonds involving the coordination and crystallization water molecules together with the uncoordinated cyanide nitrogen atoms of the [Fe(L)(CN)(4)](-) units. Compounds 2 and 3 behave as ferromagnetic Fe(III)(2)Ni(II) chains which interact ferromagnetically at very low temperatures in the case of 2, whereas metamagnetic-like behaviour is observed for with a critical field (H(c)) around 200 G. For H > H(c) the ferromagnetic Fe(III)(2)Ni(II) chains of 3 exhibit a frequency dependence of the out-of-phase ac susceptibility signal at T < 3.5 K.     

Development of Analytical Strategies for the Determination of Olive Fruit Bioactive Compounds Using UPLC-HRMS and HPLC-DAD. Chemical Characterization of Kolovi Lesvos Variety as a Case Study

In this study, an overall survey regarding the determination of several bioactive compounds in olive fruit is presented. Two methodologies were developed, one UPLC-Q-TOF-MS method for the determination of olive fruit phenolic compounds and one HPLC-DAD methodology targeting the determination of pigments (chlorophylls and carotenoids), tocopherols (α-, β, -γ, δ-) and squalene. Target and suspect screening workflows were developed for the thorough fingerprinting of the phenolic fraction of olives. Both methods were validated, presenting excellent performance characteristics, and can be used as reliable tools for the monitoring of bioactive compounds in olive fruit samples. The developed methodologies were utilized to chemical characterize the fruits of the Kolovi olive variety, originating from the island of Lesvos, North Aegean Region, Greece. Twenty-five phenolic compounds were identified and quantified in Kolovi olives with verbascoside, hydroxytyrosol, oleacein and oleomissional found in significantly high concentrations. Moreover, 12 new bioactive compounds were identified in the samples using an in-house suspect database. The results of pigments analysis suggested that Kolovi variety should be characterized as low pigmentation, while the tocopherol and squalene content was relatively high compared to other olive varieties. The characterization of Kolovi olive bioactive content highlighted the high nutritional and possible economic value of the Kolovi olive fruit.     

Spectrophotometric Characteristics of New Pyridylindolizine Derivatives Solutions

Three new pyridylindolizine derivatives, 1, 2, 3-tricarbometoxi-7-(4-pyridyl)-pyrrolo[1, 2-a]pyridine (I), 1,2-dicarboethoxy-3-(4-bromobenzoyl)-7-(4-pyridyl)-pyrrolo[1,2-a]pyridine (II) and its isomer 1,2-dicarboethoxy-3- (4-bromobenzoyl) -5- (2-pyridyl) -pyrrolo[1, 2-a]pyridine (III) have been investigated in different solutions by UV-VIS absorption, steady-state, and time-resolved fluorescence methods. The effects of the substituent and solvent on the spectroscopic properties have been demonstrated. The fluorescence decay data could be fitted to a single-exponential function. The lifetime values are higher in protic polar than in aprotic apolar solvents for compound I. In the case of compounds II and III the fluorescence intensities and lifetimes are very low, with the exception of III in aprotic solvents. The absorption and fluorescence properties of the compounds showed a solvent dependence.     

Prediction of properties of biodiesel-diesel blends using spectrofluorimetry and multivariate calibration

Regressions based on fluorescence spectroscopy were developed to provide relatively inexpensive and rapid measurements of the concentration, viscosity, and specific gravity of biodiesel-diesel blends. The methods involved obtaining a mathematical model from spectrofluorimetric data and data from a given property (concentration, dynamic viscosity, or specific gravity) using partial least squares (PLS) regression, which was then applied as a model for predicting properties of interest. The predicted concentrations, dynamic viscosities, and specific gravities of the biodiesel-diesel blends were compared with actual values and agreed reasonably well with the obtained results. The models showed high correlation between real and predicted values. The R-square values near 1 indicated excellent model accuracy for predicting concentrations, specific gravities, and dynamic viscosities of biodiesel-diesel blends. The residual distribution did not follow a trend with respect to the predicted variables, indicating an excellent fit to the data.      

Charge transfer in model bioinspired carotene-porphyrin dyads

We present a computational study based on accurate DFT and TD-DFT methods on model bioinspired donor-acceptor dyads, formed by a carotenoid covalently linked to a tetraphenylporphyrin (TPP) at the ortho position of one of the TPP phenyl rings. Dyadic systems can be used in the construction of organic solar cells and development of efficient photocatalytic systems for the solar energy conversion, due to the unique advantages they offer in terms of synthetic feasibility. This study aims to describe the influence of chemical modifications on the absorption spectra, in particular on the lowest energy charge transfer bands. Effects of different metals of biological interest, i.e., Mg, Fe, Ni, and Zn, and of H(2)O and histidine molecules coordinated to the metals in different axial positions are rationalized.     

Entropy and Enthalpy Effects on Metal Complex Formation in Non-Aqueous Solvents: The Case of Silver(I) and Monoamines

Access to the enthalpy and entropy of the formation of metal complexes in solution is essential for understanding the factors determining their thermodynamic stability and speciation. As a case study, in this report we systematically examine the complexation of silver(I) in acetonitrile (AN) with the following monoamines: n-propylamine (n-pr), n-butylamine (n-but), hexylamine (hexyl), diethylamine (di-et), dipropylamine (di-pr), dibutylamine (di-but), triethylamine (tri-et) and tripropylamine (tri-pr). The study shows that the complex stabilities are quite independent of the length of the substitution chain on the N atom and demonstrates that, in general, the overall enthalpy terms associated with the complex formation are strongly exothermic, whereas the entropy values oppose the complex formations. In addition, we examined the similarity of the formation constants of AgL complexes of the primary monoamines in AN, dimethylsulfoxide (DMSO) and water, which were unexpected on the basis of the difference between the donor properties of solvents.     

cEST: a flexible tool for calorimetric data analysis

Journal of Thermal Analysis and Calorimetry - The pyrolysis characteristics and kinetics of lignocellulosic biomass (cotton stalk) and seaweed (Gracilaria lemaneiformis) were studied comparatively....     

Thermodynamics of sorption of platinum on superparamagnetic nanoparticles functionalized with mercapto groups

Journal of Thermal Analysis and Calorimetry - The adsorption of Pt(IV) by iron oxide (Fe3O4) superparamagnetic nanoparticles (SPION) functionalized with 3-mercaptopropionic acid (3-MPA) is...