Palladium isotropic

Refractive index studies allow measurements of the birefringence, but also of the polarisability. The mean polarisability (a) can be determined using an isotropic liquid solution, whereas the polarisability anisotropy (Aa) is measured in the mesophase. Polarisability studies have been made on palladium, platinum, iridium and silver metallomesogens, and show a higher polarisability for the metal complexes than for their parent ligands. ... 

In the series of complexes with twelve chains ((55) M = Cu, Pd, VO R = OC H2 +i, = 6, 8, 10, 12, 14), an unusual phase sequence was observed (Table 34). The copper and palladium complexes displayed enantiotropic, disordered Coh and Coin phases, identified by their optical texture, and by X-ray diffraction. Quite uniquely, the Coin phase was systematically the lower-temperature mesophase, observed below the Coh phase. For the copper complexes, a Coir phase was seen for short-chain compounds with a transition to a Colh phase for n > 10. The intermediate octyloxy derivative displayed an unusual, but reproducible, I-Coh-Colh-Colr-Colh-Colh phase sequence on cooling from the isotropic liquid, several of these transitions being weakly first order. The decyloxy analog displayed a Colh-Colh-Colh-Colh phase sequence, and the two next homologous compounds showed a single Coin phase. To have, supposedly, so many phases of apparently the same symmetry in a single material is most unusual and no explanation was offered to help understand the phenomenon. It is to be hoped that at some stage they may be subject to re-examination so that this exotic behavior may be properly understood. 

Palladium [Named after the discovery of the asteroid, Pallas] (ICSD 64922 and PDF 46-1043) Pd or (Pd,Hg) Ms 106.42 (Native elements) Cubic a = 389.03 pm Al,cF4 (2 4) S.G. Fm3m Copper type Isotropic H 1 4.5-5 Habit granular. Color gray. Diaphaneity opaque. Luster metallic. L... 

It has been shown that a j8-diketonate liquid crystal containing palladium(II) and oxo-vanadium(IV), analogous to known copper complexes (which display discotic lamellar and columnar mesophases), has been prepared and characterized palladium complexes are mesomorphic but their identification is difficult due to their decomposition in the isotropic phase the complex n = 10 seems to present a Nj phase on the basis of optical microscopy. The vanadium complexes are enantiotropic discotic [75], while the vanadium complex, 30, presented by Styring et al. [76] (n= 10), exhibited a short monotropic columnar discotic phase. 

Figure 7. Schematic phase diagrams of the di-nuclear palladium organyls 5 a, c, and d with TNF as the electron acceptor [64] Cr crystalline, Np nematic discotic, Coli, columnar hexagonal mesophase (o intramolecular ordered), Iso isotropic liquid (see footnote I in Sec. 3 commenting on the nomenclature of columnar mesophases). Shaded areas mark bi-phasic regions.

Although several reports exist describing a variety of synthetic approaches for isotropic palladium nanoparticles, a major challenge exists in the ability to produce well-defined and monodisperse Pd nanoparticles. For wet-chemical methods used in the preparation of palladium nanoparticles, both organic and inorganic Pd compounds have been used as precursors. The oxidation state of the Pd compounds largely dictates the reaction conditions under which the synthetic procedure will ensue. For example, the decomposition of zerovalent organometallic Pd complexes is usually performed in an air-free environment with well-controlled... 

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