This paper represents the hydrothermal synthesis of new isomorphous lanthanide-vanadium complexes with one-dimensional coordination polymers: [Pr(2)(VO(2))(2)(dipic)(4)(H(2)O)(9)] center dot nH(2)O with dipic = pyridine-2,6-dicarboxylic acid and n = 7.75. The structure determination shows a unique one-dimensional structure in which three types of chains run along the c-axis: the chain of positively charged praseodymium complexes bridged by a dipic ligand ([Pr(dipic)(H(2)O)5](+)), the chain of negatively charged, stacked vanadium complexes ([VO(2)(dipic)](-)), and the chain of neutral praseodymium complexes with a bridged dipic ligand and a coordinating dipic ligand ([Pr(dipic)[VO(2)(dipic)](H(2)O)(4)]). Such one-dimensional chains provide open channels which can accommodate water molecules. Not only accommodated water molecules but also ones coordinated to praseodymium ions were easily removed and absorbed upon heating at 200 degrees C and exposure of humidity at room temperature, respectively. (C) 2009 Elsevier Ltd. All rights reserved.