Proposed iron–nitrogen molecule produced in a solid nitrogen matrix

Abstract

Mössbauer spectra of ⁵⁷Fe in a solid nitrogen matrix were obtained. They include in addition to the monomer doublet, a doublet with an isomer shift of +0.71 ± 0.04 mm s^–1 and a quadrupole splitting of 1.17 ± 0.04 mm s^–1. The data suggest that an iron–nitrogen molecule is formed in the matrix and that the iron dimer is the initiating structure in the bonding of nitrogen to iron. The application of an external magnetic field of 31 kOe produces an internal field with a magnitude of 31 ± 2kOe at the ⁵⁷Fe nucleus in the proposed iron nitrogen molecule. An effective internal field at the ⁵⁷Fe nucleus of 900 ± 10 kOe is found for the iron monomer in a nitrogen matrix. Infrared spectra of iron–nitrogen matrices show nitrogen vibrational lines in the range 2017 to 2261 cm^–1. Absorption coefficients of these lines are proportional to the square of the iron concentration in the range 0.3 to 3 %. This functional relationship is expected if the iron dimer is involved in the bonding of the complex.