INFRARED ABSORPTION SPECTROSCOPY OF SMALL CARBON CLUSTER $\cdot$ WATER COMPLEXES ISOLATED IN SOLID Ar

$^{a}$ B.J. Ortman, R.H. Hauge, J.L. Margrave, and Z.H. Kafafi, J. Phys. Chem. 94, 7973 (1990). $^{b}$ J. Szczepanski, S. Ekem, and M. Vala, J. Phys. Chem. 99, 8002 (1995). $^{c}$ S. Ekern, J. Szczepanski, and M. Vala, J. Phys. Chem. 100, 16109 (1996). $^{d}$ S. Ekern and M. Vala, J. Phys. Chem. 101, 3601 (1997).Author Institution: Department of Chemistry and The Center for Chemical Physics, GainesvilleThe 1:1 complexes between $C_{n} (n \leq 13)$ carbon clusters and the $H_{2}O$ molecule formed in Ar matrices at 12K have been investigated $experimentally.^{ab}$ In addition, IR absorption bands found with higher energy than the $C_{n} \cdot H_{2}O C-C$ stretching bands have been assigned to 1:2 complexes with the general structure $H_{2}O \cdot C_{n}\cdot H_{2}O$, rather than $C_{n}\cdot (H_{2}O)_{2}$. The proposed structure is supported by geometry optimization and harmonic frequencies calculated at $B3LYP/6-31G^{\ast \ast}$ level for the $C_{n}\cdot H_{2}O, H_{2}O \cdot C_{n}\cdot H_{2}O$ and $C_{n} \cdot (H_{2}O)_{2}$ systems. In particular, the ${^{13}}C$-labeled experimental spectra for ${^{12/13}}C_{5}\cdot H_{2}O$ and ${^{12/13}}C_{6}\cdot H_{2}O$ complexes will be presented and compared to the calculated ones at the $B3LYP/6-31G^{\ast \ast}$ level. The $C_{n}O$ and $C_{2}H_{2}$ final photoproducts observed after UV matrix photolysis will be discussed within the context of possible photo-production of these species in interstellar $space.^{cd}