Ferronematic Co(II) Complex: An Active Filler for Magnetically Actuated Soft Materials.

Ferronematics that are generally based on nematic liquid crystals (LCs) doped with magnetic nanoparticles, synergistically taking advantage of the anisotropic and flow characteristics of the nematic host and the magnetic susceptibility of the dopant, have powerful applications as magnetically actuated soft materials. In this work, a Co(II) complex, which alone presents both characteristics, is built with a salen-type ligand 3,5-dichlorosubstituted at the aromatic nuclei and has a tetramethyldisiloxane spacer, which makes it one of the few metallomesogens containing this structural motif. Paramagnetic crystals, through heat treatment above 110 °C, change into magnetic nematic LCs. Applying a perpendicular magnetic field of 50 mT, the nematic droplets align two by two through dipole-dipole interactions. By incorporating it into a silicone matrix consisting mainly of polydimethylsiloxane, a 3D printable ink is formulated and crosslinked under various shapes. In this environment, the cobalt complex is stabilized in an LC state at room temperature and, due to its anisotropy, facilitates the mechanical response to magnetic stimuli. The resulting objects can be easily manipulated on fluid or rough surfaces using external magnetic fields, behave like magnets by themselves, and show reversible locomotion.

Some Theoretical and Experimental Evidence for Particularities of the Siloxane Bond.

The specific features of the siloxane bond unify the compounds based on it into a class with its own chemistry and unique combinations of chemical and physical properties. An illustration of their chemical peculiarity is the behavior of 1,3-bis(2-aminoethylaminomethyl)tetramethyldisiloxane (AEAMDS) in the reaction with carbonyl compounds and metal salts, by which we obtain the metal complexes of the corresponding Schiff bases formed in situ. Depending on the reaction conditions, the fragmentation of this compound takes place at the siloxane bond, but, in most cases, it is in the organic moieties in the ß position with respect to the silicon atom. The main compounds that were formed based on the moieties resulting from the splitting of this diamine were isolated and characterized from a structural point of view. Depending on the presence or not of the metal salt in the reaction mixture, these are metal complexes with organic ligands (either dangling or not dangling silanol tails), or organic compounds. Through theoretical calculations, electrons that appear in the structure of the siloxane bond in different contexts and that lead to such fragmentations have been assessed.

Color Modifications of a Maxillofacial Silicone Elastomer under the Effect of Cigarette Smoke.

Although it is known (from the observations of medical professionals) that cigarette smoke negatively affects maxillofacial prostheses, especially through staining/discoloration, systematic research in this regard is limited. Herein, the color modifications of M511 maxillofacial silicone, unpigmented and pigmented with red or skin tone pigments, covered with mattifiers, or with makeup and mattifiers, and directly exposed to cigarette smoke, were investigated by spectrophotometric measurements in the CIELab and RGB color systems. The changes in color parameters are comparatively discussed, showing that the base silicone material without pigmentation and coating undergoes the most significant modifications. Visible and clinically unacceptable changes occurred after direct exposure to only 20 cigarettes. By coating and application of makeup, the material is more resistant to color changes, which suggests that surface treatments provide increased protection to adsorption of the smoke components. The dynamic water vapor sorption (DVS) measurements indicate a decrease of the sorption capacity in pigmented versus unpigmented elastomers, in line with the changes in color parameters.

Crystal structure of catena-poly[[methanoldioxidouranium(VI)]-µ-2-[5-(2-oxidophen-yl)-1H-1,2,4-triazol-3-yl]acetato-κ2 O:O'].

In the title complex, [U(C10H7N3O3)O2(CH3OH)] n , the UVI cation has a typical penta-gonal-bipyramidal environment with the equatorial plane defined by one N and two O atoms of one doubly deprotonated 2-[5-(2-hy-droxy-phen-yl)-1H-1,2,4-triazol-3-yl]acetic acid ligand, a carboxyl-ate O atom of the symmetry-related ligand and the O atom of the methanol mol-ecule [U-N/Oeq 2.256 (4)-2.504 (5) Å]. The axial positions are occupied by two oxide O atoms. The equatorial atoms are almost coplanar, with the largest deviation from the mean plane being 0.121 Šfor one of the O atoms. The benzene and triazole rings of the tetra-dentate chelating-bridging ligand are twisted by approximately 21.6 (2)° with respect to each other. The carboxyl-ate group of the ligand bridges two uranyl cations, forming a neutral zigzag chain reinforced by a strong O-H⋯O hydrogen bond. In the crystal, adjacent chains are linked into two-dimensional sheets parallel to the ac plane by C/N-H⋯N/O hydrogen bonding and π-π inter-actions. Further weak C-H⋯O contacts consolidate the three-dimensional supra-molecular architecture. In the solid state, the compound shows a broad medium intensity LMCT transition centred around 463 nm, which is responsible for its red colour.

Synthesis, crystal structure and Hirshfeld surface analysis of a new copper(II) complex based on diethyl 2,2'-(4H-1,2,4-triazole-3,5-di-yl)di-acetate.

The title compound, bis-[µ-2,2'-(4H-1,2,4-triazole-3,5-di-yl)di-acetato]-bis-[di-aqua-copper(II)] dihydrate, [Cu2(C6H5N3O4)2(H2O)4]·2H2O, is a dinuclear octa-hedral CuII triazole-based complex. The central copper atoms are hexa-coordinated by two nitro-gen atoms in the equatorial positions, two equatorial oxygen atoms of two carboxyl-ate substituents in position 3 and 5 of the 1,2,4-triazole ring, and two axial oxygen atoms of two water mol-ecules. Two additional solvent water mol-ecules are linked to the title mol-ecule by O-H⋯N and O⋯H-O hydrogen bonds. The crystal structure is built up from the parallel packing of discrete supra-molecular chains running along the a-axis direction. Hirshfeld surface analysis suggests that the most important contributions to the surface contacts are from H⋯O/O⋯H (53.5%), H⋯H (28.1%), O⋯O (6.3%) and H⋯C/C⋯H (6.2%) inter-actions. The crystal studied was twinned by a twofold rotation around [100].

Are the metal identity and stoichiometry of metal complexes important for colchicine site binding and inhibition of tubulin polymerization?

Quite recently we discovered that copper(II) complexes with isomeric morpholine-thiosemicarbazone hybrid ligands show good cytotoxicity in cancer cells and that the molecular target responsible for this activity might be tubulin. In order to obtain better lead drug candidates, we opted to exploit the power of coordination chemistry to (i) assemble structures with globular shape to better fit the colchicine pocket and (ii) vary the metal ion. We report the synthesis and full characterization of bis-ligand cobalt(III) and iron(III) complexes with 6-morpholinomethyl-2-formylpyridine 4N-(4-hydroxy-3,5-dimethylphenyl)-3-thiosemicarbazone (HL1), 6-morpholinomethyl-2-acetylpyridine 4N-(4-hydroxy-3,5-dimethylphenyl)-3-thiosemicarbazone (HL2), and 6-morpholinomethyl-2-formylpyridine 4N-phenyl-3-thiosemicarbazone (HL3), and mono-ligand nickel(II), zinc(II) and palladium(II) complexes with HL1, namely [CoIII(HL1)(L1)](NO3)2 (1), [CoIII(HL2)(L2)](NO3)2 (2), [CoIII(HL3)(L3)](NO3)2 (3), [FeIII(L2)2]NO3 (4), [FeIII(HL3)(L3)](NO3)2 (5), [NiII(L1)]Cl (6), [Zn(L1)Cl] (7) and [PdII(HL1)Cl]Cl (8). We discuss the effect of the metal identity and metal complex stoichiometry on in vitro cytotoxicity and antitubulin activity. The high antiproliferative activity of complex 4 correlated well with inhibition of tubulin polymerization. Insights into the mechanism of antiproliferative activity were supported by experimental results and molecular docking calculations.

Dual crystalline-amorphous salen-metal complexes behave like nematic droplets with AIEgens vistas.

A series of metal salen complexes, original in view of the presence in their structure of a highly flexible and hydrophobic spacer, were prepared on the basis of the reaction of 1,3-bis(3-aminopropyl)tetramethyldisiloxane with 3,5-dichloro-, 3,5-dibromo- and 3-hydroxy-salicylaldehyde and various metal ions (Co2+, Ni2+, Cu2+ and Zn2+). The isolated products were completely characterized from the structural point of view by FTIR, NMR, elemental analysis and single crystal X-ray diffraction, and further investigated from the perspective of the behavior induced mainly by the structural peculiarities. Emphasis is placed on self-assembly properties, both in bulk and in solution, depending on temperature, solvent nature and concentration, including thermotropic and lyotropic liquid crystals (LC). LCs that appear in the form of nematic toroidal droplets have been fully demonstrated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and fluorescence anisotropy studies. The fluorescence analysis results revealed the aggregation-induced emission (AIE) phenomenon, where the emission occurs only for liquid crystals, with a few exceptions. Because these complexes can exist in both amorphous and crystalline states, it raised the question of how properties, such as electrical, change when switching from one state to another. These were well highlighted by DSC, BDS, PXRD, FTIR and fluorescence anisotropy.