Understanding Refractive Index Changes in Homologous Series of Unbranched Organic Compounds Based on Beer's Law

Changes of the refractive index for homologous series of hydrocarbons are usually plotted versus the density. While there is a clear linear dependence for alkanes and alkenes, the linearity deteriorates for homologous series with functional groups involving heteroatoms. The slope can even become negative, e. g., for carboxylic acids. For gaining a deeper understanding and to establish a more general correlation, we reinvestigate the corresponding theories starting with the Newton-Laplace, Gladstone-Dale and the Lorentz-Lorenz rules. We revisit the concept of molar refractivity pioneered by Landolt and Brühl and show that it is closely connected with a twin of Beer's law. We conclude that the refractive index of homologues series should better be plotted versus the molar concentration of the main UV-chromophore, the C−H bond, which actually causes the refractive index changes. This new approach is not limited to alkanes and alkenes but holds for homologous series with functional groups including heteroatoms.     

Crystal and molecular structure of rubidium azidotrimethylaluminate,Rb[Al(CH3)3N3]

The crystal structure of rubidium azidotrimethylaluminate has been determined from three-dimensional counter data, and refined by full-matrix least-squares techniques. The crystals belong to the monoclinic space groupP2₁/n, witha= 10.003(5),b=7.497(4),c= 11.806(5) Å, = 108.70(3) °, andD _c= 1.58 g cm⁼³ forZ=4. The finalR factor for 922 observed reflections is 0.049. The compound is not isostructural with its cesium analog. The aluminum atom is coordinated in a tetrahedral fashion, and the Al-N bond length is 1.944(8) Å.     

Structures of CsMgBr3, CsCdBr3 and CsMgI3— diamagnetic linear chain lattices

The diamagnetic salts, CsMgBr₃, CsCdBr₃ and CsMgI₃, are shown by X-ray diffraction studies to adopt the CsNiCl₃ structure. This hexagonal lattice possesses a distinct one-dimensional character. The divalent metal ions in these salts are surrounded by octahedral arrays of halide ions ; however, there is a noticeable trigonal distortion. The structures are compared with those of other one-dimensional AMX₃ salts.     

Mixed metal-organic nanocapsules

The formation of hydrogen-bonded nanometer scale capsules from C-methylresorcin[4]arene represented a new area of research within the broad field of supramolecular chemistry. The related pyrogallol[4]arenes form nanocapsules of similar dimensions and this research now extends into the formation of novel metal-organic nanocapsules (MONCs). These relatively new systems are described here, with particular focus on recent advances in the formation of MONCs that are seamed together by more than one type of metal ion. This chemistry holds great potential for the isolation of designer materials that allow for enhanced control over the ratios of metal ions within these supramolecular assemblies.     

Chemistry of 2,4,6-trimercapto-1,3,5-triazine (TMT): acid dissociation constants and group 2 complexes

The acid dissociation constants of 2,4,6-trimercaptotriazine (H(3)TMT, 1) were determined and now can be employed in the preparation of complexes having specific M-TMT (M = divalent metal; TMT = 2,4,6-trimercapto-1,3,5-triazinide, C(3)N(3)S(3)(3-)) ratios. For example, the combination of H(3)TMT (1) with Mg(OH)(2) at pH 7.1 leads to the crystallization of Mg(H(2)TMT)(2).6H(2)O (4). With the appropriate pH adjustment, the contiguous series of compounds Ba(3)(TMT)(2).8H(2)O (3), Ba(H(2)TMT)(2).7H(2)O (5), and BaHTMT.3H(2)O (6) can be isolated. The compounds were characterized by mp, IR, TGA, elemental analysis, and, in the cases of 4, 5, and 6, crystallography. The comparison of 4 with 5 and 6 offers an interesting view of the difference in hard and soft bonding with TMT. In the saltlike Mg structure of 4, there is extensive hydrogen bonding, but in the Ba structures, 5 and 6, covalent Ba-S bonding dominates.     

An Indium-Seamed Hexameric Metal–Organic Cage as an Example of a Hexameric Pyrogallol[4]arene Capsule Conjoined Exclusively by Trivalent Metal Ions

A hexameric metal–organic nanocapsule is assembled from pyrogallol[4]arene units, which are stitched together with indium ions. This indium-seamed capsule is the first instance of a M₂₄L₆ type hexameric coordination cage held together exclusively by trivalent metal ions. Explicitly, unlike previously reported pyrogallol[4]arene-based metal-seamed capsules, the current In³⁺ seamed capsule is entirely supported by O→In coordinate bonds. This work demonstrates the important proof of concept of the ability of pyrogallol[4]arene to react with metals in higher oxidation states to assemble into atomically-precise hexameric coordination cages. As such, these results open up exciting avenues toward the assembly of previously unanticipated metal–organic capsules, for example offering inspiration for tackling metals exhibiting high valence states such as in the lanthanide and actinide series.     

Structure of p-tert-butylcalix[5]arene·ethyl acetate. A polymeric array of neighbor-included calixarenes

p-tert-Butylcalix[5]arene crystallizes from ethyl acetate in the monoclinic space groupC2/c witha=34.793(9),b=13.637(3),c=25.577(7), =114.28(2)°, andD _c =1.08 g cm^–3 forZ=8 (C₅₉H₇₈O₇). Refinement based on 2789 observed reflections led toR=0.071. The complex crystallizes with one molecule of ethyl acetate per calixarene molecule, with the solvent residing between calixarene units instead of within the cavity. The calixarene units neighbor-include to form a polymeric array: a t-butyl group of one calixarene is housed in the cavity of an adjacent calixarene. The packing arrangement of the calixarene molecules bears a remarkable resemblance to a zeolitic array.     

Mercury pollution and remediation: the chemist's response to a global crisis

Environmental mercury pollution is a growing global problem. Due to its unique properties, mercury has in the past been widely used by a variety of industries. This has led to the deposition of large amounts of mercury into the environment, where it is naturally redistributed but not naturally removed. In its methylated form, this mercury tends to accumulate in marine life, eventually reaching levels that can be toxic to humans. Fortunately a variety of remediation methods, including phytoremediation, filtration, and chemical precipitation, are currently in development. One precipitation leagent called MetX appears extremely promising. It binds mercury and other soft heavy metals irreversibly and produces precipitates that do not leach. This technology and many others holds the promise of a future victory over mercury pollution.