Nanorod crystals of two new mercury(II) [Hg(II)] coordination polymers, [Hg(4-bpdh)Br 2 ] n ( 1) and [Hg(3-bpdh)Br 2] n ( 2) {4-bpdh ¼2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene and 3-bpdh -2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene}, were prepared from the reaction of Hg(II) bromide with 4-bpdh and 3-bpdh by a sonochemical method. The nanorod crystals of 1 and 2 were characterized by scanning electron microscopy, X-ray powder diffraction, and IR spectroscopy. Compounds 1 and 2 were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of 1 and 2 were studied by thermal gravimetric and differential thermal analyses, which revealed that nanostructures of 1 and 2 are somewhat less stable than their bulk materials.