Thermodynamic Properties of Aqueous Solution of 2-Isopropoxyethanol at 25°C

Excess enthalpy, excess isobaric heat capacity, density, and speed of sound for aqueous 2-isopropoxyethanol solutions were measured at 25°C. The density was also measured at 20°C. The excess enthalpy was –800 J-mol^–1 at the minimum (mole fraction alcohol, x = 0.2), showing that the hydrogen bonds formed between unlike molecules are stronger than those in both pure liquid states. The excess volume also was large and negative, more than –1.2 cm³-mol^–1 at the minimum (x = 0.35). Excess isentropic and isothermal compressibilities are extremely negative. These results suggest that breaking the hydrogen bond network in water and forming the stronger hydrogen bonds between unlike molecules reduces the volume of the solution and makes the solution less compressible. The excess isobaric heat capacity is positive and large, up to 10 J-K^–1-mol^–1 and shows anomalous behavior in the neighborhood of x = 0.15.     

Novel reducing properties of a series of lanthanoid metals in the presence of SmI2

The reduction of dodecyl iodide, as model compound, with a series of lanthanoid (Ln) metals in the presence of catalytic amounts of samarium diiodide (SmI₂) has been investigated in detail. The reducing activity of SmI₂/Ln and the kinds of reduced products were found to be dependent on the individual Ln, but not on SmI₂.     

Molecular geometry directed Kagomé and honeycomb networks: toward two-dimensional crystal engineering

We present here the formation of a molecular Kagomé network within a two-dimensional (2D) crystal on a surface. This system provides a clear example of how, by design, molecular geometry can be expressed at the level of the 2D crystal lattice, leading to the formation of open networks. Key elements to control molecular network formation are core symmetry, location and orientation of interacting and connecting substituents, as well as symmetry matching between the networks and the surface.     

Phosphate adsorption on synthetic goethite and akaganeite

Low crystalline iron hydroxides such as goethite (alpha-FeOOH) and akaganeite (beta-FeOOH) were synthesized, and the selective adsorption of phosphate ions from phosphate-enriched seawater was examined. The results of the distribution coefficients (K(d)) of oxoanions in mixed anion solutions at pH 8 follow the selectivity order Cl-, NO3-, SO4(2-) < CO3(2-), HPO4(2-) for goethite, and Cl-, CO3(2-) < NO3- < SO4(2) < HPO4(2-) for akaganeite. In seawater, both adsorbents show high selectivity for phosphate ions despite the presence of large amounts of major cations and anions in seawater. The adsorption isotherms fitted better with the Freundlich equation and the maximum uptake of phosphate from phosphate-enriched seawater was 10 mg P/g at an equilibrium phosphate concentration of 0.3 mg P/L on both adsorbents. The phosphate adsorption/desorption cycles show that akaganeite is an excellent adsorbent even after 10 cycles and its chemical stability is good.     

Two-dimensional porous molecular networks of dehydrobenzo[12]annulene derivatives via alkyl chain interdigitation

The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid-solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagomé network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains: they connect the pi-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl chains (DBAs 3c-e) a transition from honeycomb networks to linear networks was observed in TCB, an observation attributed to stronger molecule-substrate interactions. Third, the effect of solvent on the structure of the nonpolar DBA networks was investigated in four different solvents: TCB as a polar aromatic solvent, 1-phenyloctane as a solvent having both aromatic and aliphatic moieties, n-tetradecane as an aliphatic solvent, and octanoic acid as a polar alkylated solvent. The solvent dramatically changes the structure of the DBA networks. The solvent effects are discussed in terms of factors that influence the mobility of molecules at the liquid-solid interface such as solvation.