Platinum Raman spectra

The macrocyclic phthalocyanine ligand will form a complex Pt(phthalocyanine).1106 The crystal structure shows two polymorphs present because of molecular packing.1107 The platinum is in a square planar coordination geometry with a mean Pt—N distance of 1.98 A. The complex can be partially oxidized with iodine to give conducting mixed valence solids.1108 Eighteen fundamental and overtone combination bands are observed in the resonance Raman spectrum of platinum phthalocyanine, and from this data the symmetry of the excited singlets are found to be Dy.. Qlv or D2.1109... 

Pressed pellets of BaTiC>3 were sintered in a platinum dish for six hours at 900°C in a controlled partial pressure of oxygen. The samples were quenched to room temperature, and the spectra recorded on a four-slit double-monochromator Raman spectrophotometer. An Ar+ laser with excitation at 514.5 nm was the source. The spectra were recorded at room temperature. Figure 4-30 shows the spectrum of BaTiC>3 whose Ba/Ti ratio is equal to 0.9999. The Raman spectrum is sensitive to the Ba/Ti ratio and theoxygen non-stoichiometry. The half-band width is variable as well as the intensity ratio of the 525 and 713 cm-1 bands. The ratio (I525/713) is at a minimum at the composition of 0.9999, and this can be observed in Fig. 4-31, which shows a plot of the intensity ratio (I525//713) vs. the Ba/Ti composition. 

Also linear chain complexes such as Pt(etn)4Cl3 which is known colloquially as Wolf-fram s red (etn being an abbreviation for ethylamine) have been studied successfully by resonance Raman spectroscopy (Clark, 1984). As example, we show in Fig. 6.1-12 the resonance Raman spectrum of a related halogen-bridged linear-chain species, [Pt(pn)2] [Pt(pn)2Br2] [Cu3Br5]2 (Clark et al., 1980). Although this species contains a complicated copper bromine chain, the resonance Raman spectrum (Fig. 6.1-12) is completely dominated by bands attributed to the v fundamental and its overtones n U[ of the platinum-bromine chain. 

Platinum tetrafluorlde was either prepared after the method given by Sharpe [17] or by pyrolysis of XePt2Pio 30 . The PtP4 was characterized by its X-ray powder pattern which is described in ref. [18], and by its Raman spectrum given in Fig. 5. 

Adsorbed molecules or ions formed during the various syntheses of colloidal metals have been observed by SERS. A silver hydrosol prepared by ferrous reduction of Ag in the presence of citrate showed enhanced Raman intensity corresponding to adsorbed citrate, [213] and gold colloids prepared from [Au(CN)2]" by reduction with borohydride showed SER bands due to adsorbed CN". [214] The Raman spectrum of [Pt(CN)4] adsorbed on a 1.6 nm platinum colloid has been measured, [215] but it was concluded that the slight intensity increase observed (a factor of 7) for the CN mode at 2215 cm might be due to other enhancement mechanisms. It has also been shown that ligands such as (N-4-dimethylaminoazobenzene-4 -sulfonyl)aspartate [216] adsorbed on colloidal silver are highly Raman active as a result of this phenomenon. Polymer films con-... 

A vibrational spectrum of surface species is obtained by monitoring the sum frequency signal as a function of the incident infrared photon energy, but it should be noted that for a vitautional mode to be observable by SFG, it must be both infrared and Raman active. Only those modes which lack centrosymmetry can in the dipole approximation simultaneously obey both rules. Therefore, in the experiments described in this paper the (isotropic) gas phase and the fee lattice of the bulk platinum sample possess inversion symmetry and give nearly zero contribution to the signal. Henceforth, the dominant coniribution is generated by the modes of the adsorbed monolayer at the platinum surface, where inversion symmetry is always broken [14]. 

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