ABSTRACT
Contrast variation in small-angle neutron scattering (SANS) was successfully applied to localize the anionic azo dye Blue in co-assemblies with the cationic surfactant dodecyltrimethylammoniumbromide (DTAB). For this purpose, the scattering contrast between DTAB and the aqueous solvent was eliminated by SANS contrast matching, leaving only the scattering signal from Blue to be detected. Results obtained by contrast matching were confirmed by NOESY NMR-spectroscopy, showing that Blue interacts with the positively charged DTAB head groups and with up to the 4th neighbouring methylene group of the DTAB C12-alkyl chain. Its localization in the outer layer of the Blue-DTAB co-assembly explains the uniaxial growth of spheroidal DTAB micelles to wormlike micelles with increasing [Blue] : [DTAB] ratio from 0 : 1 to 1 : 3. This is in line with the concept of the packing parameter for amphiphilic substances.
ABSTRACT
The complexity of intermolecular interactions and the difficulty to predict assembly behaviour solely based on chemical constitution was demonstrated by studying the self-assembly of three one-fold negatively charged 3-chloro-4-hydroxy-phenylazo dyes (Yellow, Blue and Red). Dye self-assembly was investigated using UV/vis- and NMR-spectroscopy, light- and small-angle neutron scattering. Significant differences between the three dyes were observed. While Yellow does not self-assemble, Red assembles into higher-order aggregates and Blue forms well-defined H-aggregate dimers with a dimerization constant of KD = (728 ± 8) L mol-1. Differences between dyes were suggested to emerge from variations in the propensity to form π-π-interactions due to electrostatic repulsion, sterical constraints and hydrogen-bonding interactions.
ABSTRACT
Highly efficient, one-step synthesis of sulfur-containing heteroacenes was achieved through palladium-catalyzed C-S cross-coupling of bis-alkynes with thioacetate as hydrogen sulfide surrogate. Heteroacenes consisting of three, five, and seven fused aromatic rings were obtained in a single catalytic step by four-, six-, and eightfold C-S bond formation.
ABSTRACT
In the mol-ecular structure of the title compound, [NiCl2(C7H12N2S)2], the Ni(II) atom has a distorted tetra-hedral geometry, coordinated by two Cl atoms [Ni-Cl= 2.2336â (6)â Å] and two thione S atoms [Ni-S= 2.3024â (6)â Å]. The angles at the Ni(II) cation, which lies on a twofold rotation axis, are Cl-Ni-Cl = 115.58â (3)° and S-Ni-S = 94.55â (3)°. All other angles at the central Ni(II) atom range from 109.46â (2) to 112.96â (2)°. The C-S-Ni angle is 99.91â (6)°. The planes of two imidazolium rings make a dihedral angle of 70.56â (6)°.
ABSTRACT
The mol-ecular structure of the title compound, [ZnCl2(C11H20N2S)2], shows tetra-hedral Zn coordination from two Cl ligands and two thione groups. The Zn-Cl bond lengths differ sligthly at 2.2310â (10) and 2.2396â (11)â Å while the Zn-S bond lengths are equal at 2.3663â (9) and 2.3701â (10)â Å. The Cl-Zn-Cl angle is 116.04â (4) and S-Zn-S is 101.98â (3)°. All other angles at the central Zn atom range from 108.108â (3) to 110.21â (4)°. The C-S-Zn angles are 100.75â (10) and 103.68â (11)°, the difference most probably resulting from packing effects, as both the C-S and both the S-Zn bonds are equal in each case. The two imidazole ring planes make a dihedral angle of 67.9â (1)°. The CH3 groups of one isopropyl moiety are disordered over two sets of sites with occupation factors of 0.567â (15) and 0.433â (15). It may be noteworthy that the isomolecular Cu complex shows a different crystal packing (group-subgroup relation) with the Cu atom lying on a twofold rotation axis. In the crystal, the shortest non-bonding contact is a C-Hâ¯Cl inter-action. This leads to the formation of centrosymmetric dimers that are stacked along the c-axis.
ABSTRACT
The mol-ecular structure of the title compound, [CuCl(C7H12N2S)2], shows a slightly distorted trigonal-planar coordination geometry of the Cu atom. The Cu-Cl bond measures 2.2287â (9)â Å, and the two Cu-S bonds are significantly different from each other, with values of 2.2270â (10) and 2.2662â (10)â Å. Also, the S-Cu-Cl angles differ, with values of 113.80â (4) and 124.42â (4)°, while the S-Cu-S angle is 121.51â (4)°. The two imidazole rings are almost parallel, making a dihedral angle of 2.1â (2)°. In the crystal, the shortest C-Hâ¯Cl interactions stabilize a three-dimensional network with molecules linked into centrosymmetric dimers that are stacked along the b-axis direction.
ABSTRACT
The mol-ecular structure of the title compound, [CuCl2(C11H20N2S)2], shows the Cu(II) atom with a distorted tetra-hedral geometry from two Cl atoms [Cu-Cl = 2.2182â (6)â Å] and two thione S atoms [Cu-S = 2.3199â (6)â Å]. The angles at the copper cation, which lies on a twofold rotation axis, are Cl-Cu-Cl = 142.84â (4)°, Cl-Cu-S = 94.80â (2) and 99.97â (2)°, and S-Cu-S = 132.46â (4)°. The planes of the two imidazolium rings make a dihedral angle of 76.92â (8)°.
ABSTRACT
The mol-ecular structure of the title compound, [Ni(C(19)H(21)N(2)P)(2)]I(2)·2CH(3)CN, shows two six-membered N-heterocyclic carbene/phosphane chelate rings that form a nearly square-planar coordination geometry around the Ni(II) atom, which lies 0.190â (1)â Å above the C(2)P(2) plane. The sum of the bond angles at the Ni(II) atom is 358.68â (6)°, with C-Ni-P bite angles of 82.89â (5) and 84.08â (6)°. The two carbene rings make a dihedral angle of 52.65â (8)°.
ABSTRACT
In the structure of the title compound, [Pd(C(19)H(21)N(2)P)(2)](PF(6))(2)·2.85CH(3)CN, the two six-membered NHC-phosphane chelate rings form a distorted square-planar coordination geometry around the Pd(II) atom, which lies 0.212â (1)â Å above the coordination plane. The sum of the bond angles at Pd(II) is 358.3°, with C-Pd-P bite angles of 84.03â (10) and 83.54â (9)°. The structure includes three acetonitrile solvent mol-ecules, one with partial site occupation and one with severe disorder, which was eventually excluded from the refinement.
