Electronic, bonding, and optical properties of 1d [CuCN]n (n = 1-10) chains, 2d [CuCN]n (n = 2-10) nanorings, and 3d [Cun (CN)n ]m (n = 4, m = 2, 3; n = 10, m = 2) tubes studied by DFT/TD-DFT methods.

The electronic, bonding, and photophysical properties of one-dimensional CuCN (n = 1-10) chains, 2-D CuCN (n = 2-10) nanorings, and 3-D Cu(n)(CN)(n) (n = 4, m = 2, 3; n = 10, m = 2) tubes are investigated by means of a multitude of computational methodologies using density functional theory (DFT) and time-dependent-density-functional theory (TD-DFT) methods. The calculations revealed that the 2-D CuCN (n = 2-10) nanorings are more stable than the respective 1-D CuCN (n = 2-10) linear chains. The 2-D CuCN (n = 2-10) nanorings are predicted to form 3-D Cun (CN)(n) (n = 4, m = 2, 3; n = 10, m = 2) tubes supported by weak stacking interactions, which are clearly visualized as broad regions in real space by the 3D plots of the reduced density gradient. The bonding mechanism in the 1-D CuCN (n = 1-10) chains, 2-D CuCN (n = 2-10) nanorings, and 3-D Cu(n)(CN)(n) (n = 4, m = 2, 3; n = 10, m = 2) tubes are easily recognized by a multitude of electronic structure calculation approaches. Particular emphasis was given on the photophysical properties (absorption and emission spectra) of the CuCN chains, nanorings, and tubes which were simulated by TD-DFT calculations. The absorption and emission bands in the simulated TD-DFT absorption and emission spectra have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made.