AN INFRARED SPECTROSCOPIC AND QUASI-RELATIVISTIC THEORETICAL-STUDY OFTHE COORDINATION AND ACTIVATION OF DINITROGEN BY THORIUM AND URANIUM ATOMS

The reactions of laser-ablated thorium and uranium metals in condensin g pure dinitrogen streams as well as argon/dinitrogen mixtures have pr ovided spectroscopic Evidence for the presence of several previously u ncharacterized actinide metal nitrides and dinitrogen complexes. Infra red spectra of the matrix isolated product species indicate that thori um and uranium atoms have a significant bond weakening effect on dinit rogen upon initial complexation and in some cases complete dinitrogen bond cleavage is observed. In the reactions of laser-ablated thorium a nd uranium atoms with pure dinitrogen, the primary products are the me tal mononitride (M-N), the metal dinitride (N-M-N), and in the uranium reactions, two dinuclear products U(mu-N)(2)U and NU(mu-N)(2)U. In th e reactions of thorium with dinitrogen in argon, the primary products are N-Th-N, Th(mu-N)(2)Th, and the dinitrogen complexes Th-eta(1)-N-2 and Th-eta(1):eta(1)-(N-2)(2). The complete ground-state electronic st ructure and vibrational spectrum cf each product molecule has been mod eled using quasirelativistic density functional calculations in order to lend support to the spectral assignments and to give insight into t he electronic structure of these new species. (C) 1998 American Instit ute of Physics.