Lanthanum Lead Oxide Hydroxide Nitrates with a Nonlinear Optical Effect

Two new lanthanum lead oxide hydroxide nitrates with acentric structure, [LaPb8O(OH)(10)(H2O)](NO3)(7) (1) and [LaPb8O(OH)(10)(H2O)](NO3)(7) 2H(2)O (2), have been prepared under subcritical hydrothermal conditions and crystallize in the space groups of Cc and P2(1)2(1)2(1), respectively. The crystal structure of compound 1 consists of the novel [LaPb8O(OH)(10)(H2O)](7+) clusters regularly arranged along the ab plane with nitrate ions as the counterions around the clusters by Pb-O bonds, developing into a three-dimensional net framework, while the structure of compound 2 is composed of [LaPb8O(OH)(10)(H2O)](7+) clusters and [NO3](-) groups as the bridging groups, forming a three-dimensional net framework with crystallized water molecules filling in the gaps. The experiments confirmed that compound 1 is the residue of compound 2 after efflorenscence. Besides, the [LaPb8O(OH)(10)(H2O)](7+) clusters present mirror symmetry in structures of the two compounds. The second-harmonic-generation (SHG) measurements for the two nitrates indicate that the SHG responses for compounds 1 and 2 are 1.3 and 1.1 times that of KH2PO4, respectively. Theoretical calculations confirmed that the SHG efficiency of compounds 1 and 2 mainly arises from the NO3- groups in the structure.