New Trends in Beverage Packaging Systems: A Review

New trends in beverage packaging are focusing on the structure modification of packaging materials and the development of new active and/or intelligent systems, which can interact with the product or its environment, improving the conservation of beverages, such as wine, juice or beer, customer acceptability, and food security. In this paper, the main nutritional and organoleptic degradation processes of beverages, such as oxidative degradation or changes in the aromatic profiles, which influence their color and volatile composition are summarized. Finally, the description of the current situation of beverage packaging materials and new possible, emerging strategies to overcome some of the pending issues are discussed

New complexes of chromium(III) containing organic π-radical ligands: An experimental and density functional theory study

The electronic structures of a series of chromium complexes 1–7 have been experimentally investigated using a combination of X-ray crystallography, magneto- and electrochemistry, and Cr K-edge X-ray absorption and UV–vis spectroscopies. Reaction of the dimer [CrII2(μ-CH3CO2)4]0 with 2,2′-bipyridine (bpy0) produced the complex [CrIII(bpy0)(bpy•)(CH3CO2)2]0 (S = 1) (1), but in the presence of isopropylamine (iPrNH2) [CrIII(bpy•)(iPrNH2)2(CH3CO2)2]0 (S = 1) (2) was obtained. Both 1 and 2 contain a CrIII ion and a single (bpy•)1– ligand, so are not low-spin CrII species. One-electron oxidation of 1 and 2 yielded [CrIII(bpy0)2(CH3CO2)2]PF6 (S = 3/2) (3) in both cases. In addition, the new neutral species [CrIII(DAD•)3]0 (S = 0) (4) and [CrIII(CF3AP•)3]0 (S = 0) (5) have been synthesized. Both complexes contain three π-radical anion ligands, which derive from one electron reduction of 1,4-bis(cyclohexyl)-1,4-diaza-1,3-butadiene and one electron oxidation of 2-(2-trifluoromethyl)-anilino-4,6-di-tert-butylphenolate, respectively. Intramolecular antiferromagnetic coupling to d3 CrIII gives the observed singlet ground states. Reaction of [CrII(CH3CN)6](PF6)2 with 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine (PDI0) under anaerobic conditions affords dark brown microcrystals of [CrIII(PDI0)(PDI•)](PF6)2 (S = 1) (6). This complex is shown to be a member of the electron transfer series [CrIII(PDI)2]3+/2+/1+/0, in which all one-electron transfer processes are ligand-based. By X-ray crystallography, it was shown that 6 possesses a localized electronic structure, such that one ligand is neutral (PDI0) and the other is a π-radical monoanion (PDI•)1–. Again, it should be highlighted that 6 is not a CrII species. Lastly, the structure of [CrIII(Mebpy•)3]0 (S = 0) (7, Mebpy = 4,4′-dimethyl-2,2′-bipyridine) has been established by high resolution X-ray crystallography and clearly shows that three (Mebpy•)1– radical anions are present. To further validate our electronic structure assignments, complexes 1–6 were investigated computationally using density functional theory (DFT) and found in all cases to contain a CrIII ion. This oxidation state assignment was experimentally confirmed for complexes 2, 4, 5, and 6 by Cr K-edge X-ray absorption spectroscopy

Molecular and Electronic Structure of Square-Planar Gold Complexes Containing Two 1,2-Di(4-tert-butylphenyl)ethylene-1,2-dithiolato Ligands: [Au(²L)₂]^1+/0/1-/2-. A Combined Experimental and Computational Study

From the reaction of in situ generated 1,2-di(4-tert-butylphenyl)ethylene-1,2-dithiol, 2LH2, and Na[AuCl4]·2H2O in 1,4-dioxane, green brown crystals of diamagnetic [N(n-Bu)4][AuIII(2L)2] (1) were obtained. As shown by cyclic voltammetry, 1 is a member of an electron-transfer series comprising the dianion [AuII(2L)2]2-, the monoanion [AuIII(2L)2]-, the neutral species [AuIII(2L•)(2L)]0 ↔ [AuIII(2L)(2L•)]0, and the monocation [AuIII(2L•)2]+. (2L•)1- represents the π radical anion (Srad = 1/2) of the one-electron oxidized closed-shell dianion (2L)2-. Oxidation of 1 in CH2Cl2 with ferrocenium hexafluorophosphate affords green, paramagnetic microcrystals of [AuIII(2L•)(2L)] ↔ [AuIII(2L)(2L•)] (2) (S = 1/2). Complexes 1 and 2 have been characterized by X-ray crystallography. Both species possess square-planar monoanions and neutral molecules, respectively. From the oxidation reaction of 1 or [N(n-Bu)4][AuIII(3L)2] with 2−3 equiv of [NO]BF4 in CH2Cl2, a green solution of [AuIII(2L•)2]+ and green microcrystals of [AuIII(3L•)2]BF4 (3) were obtained, respectively; (3L)2- represents the dianion 1,2-di(4-diphenyl)ethylene-1,2-dithiolate, and (3L•)1- is its π radical monoanion. The electronic structures of this series of gold species have been elucidated by UV−vis, EPR spectroscopies, and DFT calculations. It is shown computationally by density functional theoretical (DFT) methods that the electronic structure of [AuIII(1L•)2]+ is best described as a singlet diradical (St = 0); the ligand mixed valency in the neutral species 2 is of class (III) (delocalized); the monoanion in 1 contains a AuIII ion and two closed-shell dianionic ligands; and the corresponding dianions [Au(L)2]2- are best described as an intermediate AuII/AuIII species with a metal−ligand delocalized SOMO (25% Au 5d, 75% 3p of four S atoms). (1L)2- is the dianion 1,2-di(phenyl)ethylene-1,2-dithiolate, and (1L•)1- is the π radical monoanion. The neutral species [PdII(2L•)2] (4) has also been synthesized and characterized by X-ray crystallography. Its electronic structure is the same as described for [AuIII(1L•)2]+ (singlet diradical), whereas that of the monoanion [PdII(2L•)(2L)]- ↔ [Pd(2L)(2L•)]- corresponds to that of the neutral gold complex 2. Anodic oxidation of the analogous monoanion [AuIII(mnt)2]-, where mnt = maleonitriledithiolate, gave the neutral complex [Au(mnt)(mnt•)] (E1/2 = 0.91 V vs Fc+/Fc). The optical and EPR spectroscopies of [Au(mnt)(mnt•)] were consistent with those observed for the corresponding di(tert-butylphenyl)ethylenedithiolate complex 2

Molecular and Electronic Structure of Four‐ and Five‐Coordinate Cobalt Complexes Containing Two o‐Phenylenediamine‐ or Two o‐Aminophenol‐Type Ligands at Various Oxidation Levels: An Experimental, Density Functional, and Correlated ab initio Study

The bidentate ligands N‐phenyl‐o‐phenylenediamine, H2(2), or its analogue 2‐(2‐trifluoromethyl)anilino‐4,6‐di‐tert‐butylphenol, (4), react with [CoII(CH3CO2)2]⋅4H2O and triethylamine in acetonitrile in the presence of air yielding the square‐planar, four‐coordinate species [Co(2LN)2] (1) and [Co(4LO)2] (4) with an S=1/2 ground state. The corresponding nickel complexes [Ni(4LO)2] (8) and its cobaltocene reduced form [CoIII(Cp)2][Ni(4LO)2] (9) have also been synthesized. The five‐coordinate species [Co(2LN)2(tBu‐py)] (2) (S=1/2) and its one‐electron oxidized forms [Co(2LN)2(tBu‐py)](O2CCH3) (2 a) or [Co(2LN)2I] (3) with diamagnetic ground states (S=0) have been prepared, as has the species [Co(4LO)2(CH2CN)] (7). The one‐electron reduced form of 4, namely [Co(Cp)2][Co(4LO)2] (5) has been generated through the reduction of 4 with [Co(Cp)2]. Complexes 1, 2, 2 a, 3, 4, 5, 7, 8, and 9 have been characterized by X‐ray crystallography (100 K). The ligands are non‐innocent and may exist as catecholate‐like dianions (2)2−, (4)2− or π‐radical semiquinonate monoanions (2).−, (4).− or as neutral benzoquinones (2)0, (4)0; the spectroscopic oxidation states of the central metal ions vary accordingly. Electronic absorption, magnetic circular dichroism, and EPR spectroscopy, as well as variable temperature magnetic susceptibility measurements have been used to experimentally determine the electronic structures of these complexes. Density functional theoretical (DFT) and correlated ab initio calculation have been performed on the neutral and monoanionic species [Co(1LN)2]0,− in order to understand the structural and spectroscopic properties of complexes. It is shown that the corresponding nickel complexes 8 and 9 contain a low‐spin nickel(II) ion regardless of the oxidation level of the ligand, whereas for the corresponding cobalt complexes the situation is more complicated. Spectroscopic oxidation states describing a d6 (CoIII) or d7 (CoII) electron configuration cannot be unambiguously assigned

Intramolecular Redox-Active Ligand-to-Substrate Single-Electron Transfer: Radical Reactivity with a Palladium(II) Complex

Coordination of the redox-active tridentate NNO ligand L-H2 to Pd-II yields the paramagnetic iminobenzosemiquinonato complex 3. Single-electron reduction of 3 yields diamagnetic amidophenolato complex 4, capable of activating aliphatic azide 5. Experimental and computational studies suggest a redox-noninnocent pathway wherein the redox-active ligand facilitates intramolecular ligand-to-substrate single-electron transfer to generate an open-shell singlet "nitrene-substrate radical, ligand radical", enabling subsequent radical-type C-H amination reactivity with Pd-II