Molecular Rods Based on Oligo-spiro-thioketals.

We report on an extension of the previously established concept of oligospiroketal (OSK) rods by replacing a part or all ketal moieties by thioketals leading to oligospirothioketal (OSTK) rods. In this way, some crucial problems arising from the reversible formation of ketals are circumvented. Furthermore, the stability of the rods toward hydrolysis is considerably improved. To successfully implement this concept, we first developed a number of new oligothiol building blocks and improved the synthetic accessibility of known oligothiols, respectively. Another advantage of thioacetals is that terephthalaldehyde (TAA) sleeves, which are too flexible in the case of acetals can be used in OSTK rods. The viability of the OSTK approach was demonstrated by the successful preparation of some OSTK rods with a length of some nanometers.

rac-1-[(2-Methoxyethyl)sulfanyl]-2-[(2-methoxyethyl)sulfinyl]benzene and its PdCl2 complex.

As an extension of recent findings on the recovery of palladium with dithioether extractants, single crystals of the chelating vicinal thioether sulfoxide ligand rac-1-[(2-methoxyethyl)sulfanyl]-2-[(2-methoxyethyl)sulfinyl]benzene, C(12)H(18)O(3)S(2), (I), and its square-planar dichloridopalladium complex, rac-dichlorido{1-[(2-methoxyethyl)sulfanyl]-2-[(2-methoxyethyl)sulfinyl]benzene-κ(2)S,S'}palladium(II), [PdCl(2)(C(12)H(18)O(3)S(2))], (II), have been synthesized and their structures analysed. The molecular structure of (II) is the first ever characterized involving a dihalogenide-Pd(II) complex in which the palladium is bonded to both a thioether and a sulfoxide functional group. The structural and stereochemical characteristics of the ligand are compared with those of the analogous dithioether compound [Traeger et al. (2012). Eur. J. Inorg. Chem. pp. 2341-2352]. The sulfinyl O atom suppresses the electron-pushing and mesomeric effect of the S-C-C-S unit in ligand (I), resulting in bond lengths significantly different than in the dithioether reference compound. In contrast, in complex (II), those bond lengths are nearly the same as in the analogous dithioether complex. As observed previously, there is an interaction between the central Pd(II) atom and the O atom that is situated above the plane.

Intramolecular deactivation processes in complexes of salicylic acid or glycolic acid with Eu(III).

The complexation of Eu(III) by 2-hydroxy benzoic acid (2HB) or glycolic acid (GL) was investigated using steady-state and time-resolved laser spectroscopy. Experiments were carried out in H(2)O as well as in D(2)O in the temperature range of 80KF7(0) transition, (iii) the width of the D5(0)-->F7(0) transition, and (iv) the asymmetry ratio calculated from the luminescence intensities of the D5(0)-->F7(2) and D5(0)-->F7(1) transition, respectively. The differences in ligand-related luminescence quenching are discussed. Based on the temperature dependence of the luminescence decay times an activation energy for the ligand-specific non-radiative deactivation in Eu(III)-2HB or Eu(III)-GL complexes was determined. It is stressed that ligand-specific quenching processes (other than OH quenching induced by water molecules) need to be determined and considered in detail, in order to extract speciation-relevant information from luminescence data (e.g., estimation of the number of water molecules n(H(2)0) in the first coordination sphere of Eu(III)). In case of 2HB, conclusions drawn from the evaluation of the Eu(III) luminescence are compared with results of a X-ray structure analysis.