Photoluminescence of 1-D copper(l) cyanide chains: A theoretical description


Solid copper(l) cyanide occurs as extended one-dimensional chains with interesting photophysical properties. To explain the observed luminescence spectroscopy of CuCN, we report a series of computational studies using short bare and potassium-capped [Cu n(CN) n+1] ~(n = 1, 2, 3, 4, 5, and 7) chains as CuCN models. On the basis of TD-DFT calculations of these model chains, the excitation transitions in the UV spectrum are assigned as Laporte-allowed π-π transitions from MOs with Cu 3d π and CN π character to empty MOs with Cu 4p and CN π * character. Transitions between the HOMO (3d z) and LUMO (Cu 4p and CN π *) are symmetry forbidden and are not assigned to the bands in the excitation spectrum. The emission spectrum is assumed to arise from transitions between the lowest triplet excited state and the ground-state singlet. The lowest energy triplet for the model networks has a bent structure due to distortions to remove the degeneracies in the partially occupied MOs of the linear triplet. The S 0-T gap for the bent triplet chains is consistent with the emission wavelength for bulk CuCN. © 2009 American Chemical Society.

Publication Title

Inorganic Chemistry