Inorganics, Volume 8, Issue 5 (May 2020) – 8 articles

Three catecholato copper(II) complexes, [Cu(catCl₄)(L1′)], [Cu(catBr₄)(L1′)], and [Cu(catCl₄)(L1H)], supported by sterically hindered neutral and anionic N3 type ligands: tris(3,5-diisopropyl-1-pyrazolyl)methane (referred to as L1′) and hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (referred to as L1⁻), are synthesized and characterized in detail. Their X-ray structures reveal that both [Cu(catCl₄)(L1′)] and [Cu(catBr₄)(L1′)] complexes have a five-coordinate square-pyramidal geometry and [Cu(catCl₄)(L1H)] complex has a four-coordinate square-planar geometry. The L1H is unusual protonated ligand that controls its overall charge. For the three catecholato copper(II) complexes, the oxidation state of copper is divalent, and catechol exists in catecholate as two minus anion. This difference in coordination geometry affects their d-d and CT transitions energy and ESR parameters. Full article

The second-order nonlinear optical (NLO) properties of iridium(III) complexes having two cyclometalated 2-phenylpyridines and curcumin or tetrahydrocurcumin as ancillary ligand have been investigated both in solution and as guest in a polymeric organic matrix. In solution, these complexes are characterized by a significant second-order NLO response, as determined by the Electric Field Induced Second Harmonic (EFISH) technique, like the related complex with acetylacetonate. Whereas the low second-harmonic generation response of a composite film of [Ir(2-phenylpyridine)₂(acetylacetonate)] in polymethyl methacrylate was not stable and fell down to zero upon turning off the electric field. A good and stable response was obtained with a film based on the iridium(III) complex bearing two cyclometalated 2-phenylpyridines and curcumin. Full article

Tetraorganotin tin(IV) compounds containing a flexible or rigid (4: Ph₃Sn-CH₂-C₆H₄-R; 7: Ph₃SnC₆H₄-R, R = 2-oxazolinyl) chelating oxazoline functionality were prepared in good yields by the reaction of lithiated oxazolines and Ph₃SnCl. Reaction of 7 with excess HCl resulted in the isolation of the tin monochlorido compound, 9 (ClSn[Ph₂]C₆H₄-R). Conversion of the triphenylstannanes 7 and 4 into their corresponding dibromido species was successfully achieved from the reaction with Br₂ to yield 10 (Br₂Sn[Ph]C₆H₄-R) and 11 (Br₂Sn[Ph]-CH₂-C₆H₄-R), respectively. X-ray crystallography of 4, 7, 9, 10, and 11 reveal that all structures adopt a distorted trigonal bipyramidal geometry around Sn in the solid state. Compound 4, with an additional methylene spacer group, displays a comparatively long Sn–N bond distance compared to the dibromido tin species, 11. Several DFT methods were compared for accuracy in predicting the solid-state geometries of compounds 4, 7, 9–11. Compounds 10 and 11 were further converted into the corresponding dihydrides (12: H₂Sn[Ph]C₆H₄-R, 13: H₂Sn[Ph]-CH₂-C₆H₄-R), via Br–H exchange, in high yield by reaction with NaBH₄. Polymerization of 12 or 13 with a late transition metal catalyst produced a low molecular weight polystannane (14: –[Sn[Ph]C₆H₄-R]_n–, M_w = 10,100 Da) and oligostannane (15: –[Sn[Ph]-CH₂-C₆H₄-R]_n–, M_w = 3200 Da), respectively. Full article

Ceria-based materials, and particularly CeO₂–ZrO₂ (CZ) solid solutions are key ingredient in catalyst formulations for several applications due to the ability of ceria to easily cycling its oxidation state between Ce⁴⁺ and Ce³⁺. Ceria-based catalysts have a great soot oxidation potential and the mechanism deeply relies on the degree of contact between CeO₂ and carbon. In this study, carbon soot has been used as solid reductant to better understand the oxygen transfer ability of ceria–zirconia at low temperatures; the effect of different atmosphere and contact conditions has been investigated. The difference in the contact morphology between carbon soot and CZ particles is shown to strongly affect the oxygen transfer ability of ceria; in particular, increasing the carbon–ceria interfacial area, the reactivity of CZ lattice oxygen is significantly improved. In addition, with a higher degree of contact, the soot oxidation is less affected by the presence of NO_x. The NO oxidation over CZ in the presence of soot has also been analyzed. The existence of a core/shell structure strongly enhances reactivity of interfacial oxygen species while affecting negatively NO oxidation characteristics. These findings are significant in the understanding of the redox chemistry of substituted ceria and help determining the role of active species in soot oxidation reaction as a function of the degree of contact between ceria and carbon. Full article

The syntheses and characterizations of the chelating ligand 6-chloro-6′-methyl-2,2′-bipyridine (6-Cl-6′-Mebpy) and of the copper(I) compounds [Cu(POP)(6-Cl-6′-Mebpy)][PF₆] and [Cu(xantphos)(6-Cl-6′-Mebpy)][PF₆] (POP = bis(2-(diphenylphosphanyl)phenyl)ether and xantphos = 4,5-bis(diphenylphosphanyl)-9,9-dimethyl-9H-xanthene) are described. The single crystal structures of both complexes were determined; the copper(I) ion is in a distorted tetrahedral environment and in [Cu(xantphos)(6-Cl-6′-Mebpy)][PF₆], the disorder of the 6-Cl-6′-Mebpy ligand indicates there is no preference of the ‘bowl’-like cavity of the xanthene unit to host either the methyl or chloro-substituent, consistent with comparable steric effects of the two groups. The electrochemical and photophysical properties of [Cu(POP)(6-Cl-6′-Mebpy)][PF₆] and [Cu(xantphos)(6-Cl-6′-Mebpy)][PF₆] were investigated and are compared with those of the related compounds containing 6,6′-dichloro-2,2′-bipyridine or 6,6′-dimethyl-2,2′-bipyridine ligands. Trends in properties of the [Cu(P^P)(N^N)]⁺ complexes were consistent with 6-Cl-6′-Mebpy behaving as a combination of the two parent ligands. Full article

The self-assembly reaction between NiI₂, benzoic acid (PhCO₂H) and the Schiff base chelate, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH₂), in the presence of the organic base triethylamine (NEt₃), has resulted in the isolation and the structural, spectroscopic, and physicochemical characterization of the dodecanuclear [Ni₁₂I₂(OH)₆(O₂CPh)₅(nacb)₅(H₂O)₄(MeCN)₄]I (1) cluster compound in ~30% yield. Complex 1 has a cage-like conformation, comprising twelve distorted, octahedral Ni^II ions that are bridged by five μ₃-OH⁻, one μ-OH⁻, an I⁻ in 55% occupancy, five PhCO₂⁻ groups (under the η¹:η¹:μ, η¹:η²:μ₃ and η²:η²:μ₄ modes), and the naphthoxido and carboxylato O-atoms of five doubly deprotonated nacb²⁻ groups. The overall {Ni₁₂} cluster exhibits a nanosized structure with a diameter of ~2.5 nm and its metallic core can be conveniently described as a series of nine edge- or vertex-sharing {Ni₃} triangular subunits. Complex 1 is the highest nuclearity coordination compound bearing the nacbH₂ chelate, and a rare example of polynuclear Ni^II complex containing coordinating I⁻ ions. Direct current (DC) magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Ni^II ions, while photophysical studies of 1 in the solid-state showed a cyan-to-green centered emission at 520 nm, upon maximum excitation at 380 nm. The reported results demonstrate the rich coordination chemistry of the deprotonated nacb²⁻ chelate in the presence of Ni^II metal ions, and the ability of this ligand to adopt a variety of different bridging modes, thus fostering the formation of high-nuclearity molecules with rare, nanosized dimensions and interesting physical (i.e., magnetic and optical) properties. Full article

This review focuses on organotin compounds bearing hemicarbonate and carbonate ligands, and whose molecular structures have been previously resolved by single-crystal X-ray diffraction analysis. Most of them were isolated within the framework of studies devoted to the reactivity of tin precursors with carbon dioxide at atmospheric or elevated pressure. Alternatively, and essentially for the preparation of some carbonato derivatives, inorganic carbonate salts such as K₂CO_3, Cs₂CO₃, Na₂CO₃ and NaHCO₃ were also used as coreagents. In terms of the number of X-ray structures, carbonate compounds are the most widely represented (to date, there are 23 depositions in the Cambridge Structural Database), while hemicarbonate derivatives are rarer; only three have so far been characterized in the solid-state, and exclusively for diorganotin complexes. For each compound, the synthesis conditions are first specified. Structural aspects involving, in particular, the modes of coordination of the hemicarbonato and carbonato moieties and the coordination geometry around tin are then described and illustrated (for most cases) by showing molecular representations. Moreover, when they were available in the original reports, some characteristic spectroscopic data are also given for comparison (in table form). Carbonato complexes are arbitrarily listed according to their decreasing number of hydrocarbon substituents linked to tin atoms, namely tri-, di-, and mono-organotins. Four additional examples, involving three CO₂ derivatives of C,N-chelated stannoxanes and one of a trinuclear nickel cluster Sn-capped, are also included in the last part of the chapter. Full article

A comprehensive techno-economic analysis of destabilized Li hydrides, used as thermal energy storage systems in concentrating solar power plants, is presented and discussed. Two systems, operating at temperatures on the order of 550–650 °C, are selected as thermal energy storage units for steam power plants, namely the Si-destabilized Li hydride (LiSi) and the Al-destabilized Li hydride (LiAl). Two thermal energy storage systems, operating at temperatures on the order of 700–750 °C, are selected for integration in supercritical CO₂ power plants, namely the Si-destabilized Li hydride (LiSi) and the Sn-destabilized Li hydride (LiSn). Each storage system demonstrates excellent volumetric capacity, achieving values between 100 and 250 kWhth/m³. The LiSi-based thermal energy storage systems can be integrated with steam and supercritical CO₂ plants at a specific cost between 107 US$/kWhth and 109 US$/kWhth, with potential to achieve costs on the order of 74 US$/kWhth under enhanced configurations and scenarios. The LiAl-based storage system has the highest potential for large scale applications. The specific cost of the LiAl system, integrated in solar steam power plants, is equal to approximately 74 US$/kWhth, with potential to reach values on the order of 51 US$/kWhth under enhanced performance configurations and scenarios. Full article