Transition metals photofragmentation

Photofragmentation of Transition Metal Cluster Complexes in the Gas Phase... 

The gas phase photofragmentation of transition metal cluster complexes is discussed. The information available for the gas phase dissociation of... 

Presently, the gas phase photofragmentation of several transition metal cluster complexes is reviewed. The techniques employed for these gas phase studies rely on sensitive ionization detection and the use of a broad range of excitation energies. 

The information available is discussed in light of the effects of excitation energy and the environment on the photofragmentation process of several transition metal cluster complexes. The photochemical information provides a data base directly relevant to electronic structure theories currently used to understand and predict properties of transition metal complexes (1,18,19). 

In this paper, the photofragmentation of transition metal cluster complexes is discussed. The experimental information presented concerning the gas phase photodissociation of transition metal cluster complexes comes from laser photolysis followed by detection of fragments by ionization (5.). Ion counting techniques are used for detection because they are extremely sensitive and therefore suitable for the study of molecules with very low vapor pressures (6.26.27). In addition, ionization techniques allow the use of mass spectrometry for unambiguous identification of signal carriers. 

In this review, we explain the SAC-CI applications to molecular spectroscopy with some examples. In Section 2, we briefly explain the theoretical and computational aspects of the SAC-CI method. Then, we show some SAC-CI applications to molecular spectroscopy the excitation and ionization spectra of tt-conjugated organic molecules (Section 3), collision-induced absorption spectra of van der Waals complex (Section 4), excitation spectra and NMR chemical shifts of transition metal complexes (Section 5), photofragmentation reaction of Ni(CO)4 (Section 6), absorption spectrum of free-base phthalocyanine (FBPc) and bacterial photosynthetic reaction center... 

Transition metal carbonyl is important in laser chemistry as sources of metal atoms or as precursors for chemical vapor deposition (CVD) [104]. Ni(CO)4 shows a typical photofragmentation reaction initiated by the XeCl laser (308 nm, 4.03 eV), and the knowledge on the mechanism is valuable for the design and control of the laser-induced CVD. The SAC-Cl method was applied to the excitation spectrum and the potential energy curves relevant to the photofragmentation reaction [105]. 

Various kinds of the theoretical spectroscopies for the transition metal complexes were also reviewed. For the excitation spectrum of Cr02Cl2, the SAC-Cl method simulated accurate spectrum. For tetraoxo metal complexes, the systematic studies explained the spectral differences when the central metal was substituted. In the analysis of the NMR chemical shift, not only the optically allowed states but also the magnetically allowed states are important. In the molybdenum complexes, the inverse of the d-d excitation energy is proportional to the experimental chemical shift. The photofragmentation reaction of Ni(CO)4 was also studied and the reaction mechanism was clarified. 

Laser-induced photofragmentation of transition-metal-coated fullerenes CeoM and CvoM f (M = Ti, V) was also shown to yield MgC clusters as the most abundant product as soon as the laser intensity is sufficiently high to break the fullerene cage and remove the carbon surplus. ... 

Nitzan and Brus" " have proposed that photochemical reactions on SERS-active substrates may be also enhanced. Goncher and Harris" reported photofragmentation of several molecules adsorbed on a silver surface, with an incident wavelength of 363.8 nm( ). They attribute the reaction to enhanced singlet-triplet transitions or to multiphoton processes. Chen and Osgood" reported enhanced photodeposition on several metals, but not on gold, at 257 nm. 

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