Chlorite luminescence

The adsorption of transition metal complexes by minerals is often followed by reactions which change the coordination environment around the metal ion. Thus in the adsorption of hexaamminechromium(III) and tris(ethylenediamine) chromium(III) by chlorite, illite and kaolinite, XPS showed that hydrolysis reactions occurred, leading to the formation of aqua complexes (67). In a similar manner, dehydration of hexaaraminecobalt(III) and chloropentaamminecobalt(III) adsorbed on montmorillonite led to the formation of cobalt(II) hydroxide and ammonium ions (68), the reaction being conveniently followed by the IR absorbance of the ammonium ions. Demetallation of complexes can also occur, as in the case of dehydration of tin tetra(4-pyridyl) porphyrin adsorbed on Na hectorite (69). The reaction, which was observed using UV-visible and luminescence spectroscopy, was reversible indicating that the Sn(IV) cation and porphyrin anion remained close to one another after destruction of the complex. 

Fig. 4.64. Laser-induced luminescence of chlorite with Cr emission (Czaja 1999)...

For chromium containing lilac chlorite two types of luminescence were observed at 15 K phosphorescence at 14,518 and 1,547 cm with a decay time of 60 ps and a fluorescence band at about 13,850-13,500 cm with a decay time of several microseconds. For green chlorite weak fluorescence at 13,900 cm and phosphorescence at 14,320 and 14,665 cm were observed at room tern-... 

The luminescence spectra of Cr " centers in two chlorite crystals (Fig. 4.176) have been presented (Czaja et al. 2014). Chromium ions occupy the strong crystal-field site M4 in the brucite sheet and the intermediate crystal-field site in the inner... 

---