Spectroscopic studies of the excited state: Single crystal potassium-tetrachloroplatinate, gas phase nickel-carbonyl, and nitrospiropyrans in sol gel.

摘要

A regularly spaced vibronic progression of 315 cm{dollar}sp{lcub}-1{rcub}{dollar} is observed in the luminescence spectrum of K{dollar}sb2{dollar}(PtCl{dollar}sb4{dollar}) which does not correspond to any normal vibrational modes of the molecule. The spectrum is interpreted in terms of the Missing Mode Effect (MIME). Calculations of the contributing vibrations and excited state distortions are presented. In addition, a 1800 cm{dollar}sp{lcub}-1{rcub}{dollar} gap between the emission and absorption spectrum is found in which no measurable emission intensity or absorption intensity are observed. This energy gap is explained in terms of the intra-molecular distortion along the non-totally symmetric mode which is required by the MIME. The unmeasurable low vibronic intensities in the gap are explained by using the time dependent theory of electronic spectroscopy.; The photofragmentation products of gas phase nickel tetracarbonyl luminesce under CW excitation. One emission has a broad spectrum from 18600 cm{dollar}sp{lcub}-1{rcub}{dollar} to 11500 cm{dollar}sp{lcub}-1{rcub}{dollar}. The emitting species is probably Ni(CO){dollar}sb3{dollar}*. The fragment is produced via two pathways: one, the excitation of Ni(CO){dollar}sb4{dollar} followed by loss of CO to leave the Ni(CO){dollar}sb3{dollar}* fragment, and two, the direct excitation of Ni(CO){dollar}sb3{dollar} (this path becomes evident at higher pressures of Ni(CO){dollar}sb4{dollar} and laser powers). The Ni(CO){dollar}sb3{dollar} fragment is produced by emission from Ni(CO){dollar}sb3{dollar}*, from collisional deactivation of Ni(CO){dollar}sb3{dollar}* by Ni(CO){dollar}sb4{dollar}, and by heating from the laser. The other two emissions are associated with the formation of nickel powder in the cell; the emissions may arise from excited intermediates in the photoinduced production of elemental nickel from the tetracarbonyl.; Photochromic sol-gels can be prepared by doping nitrospiropyrans into aluminosilicate sol-gels. At least two colored species are formed in the doped gel upon irradiation with UV light. One of these compounds is formed in the gel at all stages except completely dried gels; the other is found only in gels from which most of the solvent has evaporated. The decolorization is first order. A few of the nearly-dried gels show a second, slower decay which may be from some of the tautomer adsorbed onto the aluminosilicate. Both decay constants increase during the final stages of drying until the gel is no longer photochromic.