The second is a broad band appears at about 650-780 nm in G2 and G4 but disappeared in G3, because it is related to Cu 2+ ions in the distorted octahedral coordination
according to El Batal, F.H.
For three pigments Fe-[Al.sub.(pec)] (Figure 5.c) bands in the region of 460 nm occurred and are related to the presence of [Fe.sup.3+] in octahedral coordination
, related to the transition [sup.6][T.sub.1] (G) [right arrow] [sup.4][T.sub.1] (G), [sup.4]E(G) .
When Fe + ions in [Fe.sup.3+]-O-[Fe.sup.2+] structure are in tetrahedral coordination, they act as the network formers, while when [Fe.sup.2+] ions are in octahedral coordination
they are the network modifiers.
These reasons led us to design the target molecule Rh-1 (Figure 4) with octahedral coordination
geometry and evaluate in vitro its inhibitory effect against PAF-induced platelet aggregation in washed rabbit platelets (WRPs).
These iron oxides show a spinel-like structure formed by a cell unit face-centered cubic (FCC) network of oxygen anions, with sites filled by cations, differing in tetrahedral and octahedral coordination
Upon Fe doping bands assigned to octahedral coordination
become more intense and are shifted to higher wavelengths (250 nm).
The central metal in each complex has octahedral coordination
with an enolized carbonyl O atom acting as a bridging group between two metal ions .
In the case of the smectite minerals the signal at g = 4.3 is assigned to the presence of isolated [Fe.sup.3+] in tetrahedral or octahedral coordination
, which corresponds to the iron located in the interior of the clay sheets (iron substituting aluminum in the octahedral layers).
They are assignable to [Fe.sup.3+/2+] (mixed valence) in octahedral coordination
sites and to [Fe.sup.3+] in tetrahedral sites of magnetite, respectively (Table 3).
The structure of most of these niobates, tantalates, and titanates consists of octahedral coordination
that would likely produce high dielectric constants.
In space group [P4.sub.2]/nnm such sites have mm, 2/m or 222 symmetry, all of which are compatible with octahedral coordination
about the Fe.