Gas phase photodissociation spectroscopy has been employed to study photo-induced reactions of a series of mass-selected M^⋅+-L complexes (M^⋅+= Mg^⋅+, Ca^⋅+) and Mg^⋅+-L_n, clusters. Molecules with various functional groups are chosen for these studies, which include fluorinated benzene, toluene, and pyridine, nucleobases, bidentate ligands, amines, amides, and acetonitrile, etc. A rich variety of photo-induced reaction patterns have been found in the photodissociation of the Mg^⋅+-L systems mentioned above. _{3 y 6 4-x-y x}^{⋅+ ⋅+} _{6 4-x-y 2+x 3 y 2}...[ Read more ]

Gas phase photodissociation spectroscopy has been employed to study photo-induced reactions of a series of mass-selected M^⋅+-L complexes (M^⋅+= Mg^⋅+, Ca^⋅+) and Mg^⋅+-L_n, clusters. Molecules with various functional groups are chosen for these studies, which include fluorinated benzene, toluene, and pyridine, nucleobases, bidentate ligands, amines, amides, and acetonitrile, etc. A rich variety of photo-induced reaction patterns have been found in the photodissociation of the Mg^⋅+-L systems mentioned above.

Benzyne radical cations [(CH₃)_yC₆H_4-x-yF_x^⋅+] of highly chemical interest are readily generated in the photodissociation of the complexes Mg^⋅+[C₆H_4-x-yF_2+x(CH₃)_y] (when y=0, x=0-2; when y=1, x=0 or 1) by loss of very stable MgF₂. Given enough photon energies, the benzyne radical cations will undergo fragmentation in manner of C4 + C2 pattern. It's found that the fluorine and methyl substitution respectively increases and lowers the energy needed for the decomposition of the benzyne radical cations.

Comparative studies on photodissociation of the complexes Mg^⋅+-pyridine or fluoropyridine have been performed. While the photodissociation of Mg^⋅+-pyridine leads primarily to the evaporative dissociation, abundant photo-induced reaction patterns are found in the photodissociation of Mg^⋅+(2-fluoropyridine). Unusual photochemistry of Mg^⋅+(2-fluoropyridine) is resulted from a crucial fluorine shift from C to Mg^⋅+ in the initial step, forming a key intermediate FMg⁺-C₅H₄N, followed by the loss of CN-Mg-F, ^⋅MgF, C₅H₄N^⋅, HCN, and HF. Although similar intermediate [FMg⁺-C₅H_4-xF_xN (x=l or 4)] can also be formed in the photodissociation of Mg^⋅+(2,6-and penta-fluoropyridine), subsequent photochemistry is very different, characterized by the formation of pyridyne radical cations C₅H_3-xF_xN^⋅+ (x=0 or 3) as the dominant reaction channel.

Photo-induced reaction patterns of the complexes Mg^⋅+- or Ca^⋅+-nucleobases (uracil, thymine, cytosine, guanine, and adenine) have been studied and compared. Abundant photofragments with low yield are found in the photodissociation of Mg^⋅+- pyrimidine bases (uracil, thymine, and cytosine). In comparison, fewer and even no photoreaction channels are observed in the photodissociation of Mg^⋅+-guanine and Mg^⋅+-adenine, respectively, which are purine bases. Association of different metal cation (Ca^⋅+) toward nucleobases has some influence on both dissociation manner of the complexes and yield of the photofragments.

In the photodissociation of Mg^⋅+-bidentate molecules (CH₃OCH₂CH₂OH, CH₃OCH₂CH₂OCH₃, and H₂NCH₂CH₂NH₂), an initial hydrogen-shift at end C or N is found to play a crucial role for the subsequent photoreactions involving C-O, C-N, or C-C bond activations. In another case, the photoproducts of Mg^⋅+[HCON(CH₃)₂] are generated through (1) H-abstraction next to the carbonyl group by the photoexcited Mg^⋅+* (to form (CH₃)₂NCO⁺) and/or (2) the subsequent CO loss (to form CH₃NH⁺=CH₂).

Microsolvation of Mg^⋅+(NCCH₃)_n (n=1-4) clusters has been investigated in the spectral region of 230-560 nm. The photodissociation action spectra of Mg^⋅+(NCCH₃)_n(n=1-4) consist of two or three broad peaks with different magnitude of blue-shift or red-shift towards the atomic transition of Mg^⋅+ (3 ²P←3 ²S) due to different interactions of Mg^⋅+ with bonding or antibonding orbitals of the N≡C- group.