Complexes of Linear Carbon Clusters with Water

The complexes of linear Cn (n = 4−9) carbon clusters with water have been formed in argon matrices and studied via FTIR spectroscopy. In most complexes, the CC stretching mode bands are shifted to the blue from the respective Cn carbon cluster bands, and the OH stretching frequencies are shifted to the red. The observed shifts compare well with displacements predicted by density functional theory calculations. Isotopic 12C/13C substitution has been used to confirm the vibrational assignments of the C5·H2O and C6·H2O complexes. With higher water concentrations in the matrix, bands appear that are assigned to complexes with more than one water molecule, such as H2O·C3·H2O, C3·(H2O)2, and H2O·C3·(H2O)2. Photolysis of the complexes leads to a number of CnO species, such as C5O, C7O, and C9O, for which band assignments are proposed. The implications of these results for the production of molecules on grains in the interstellar medium are discussed.