A new 3-D Mn(II)-organic extended framework with a 1,4-naphthalenedicarboxylate ligand, [Mn(1,4-DNC)(DMA)]n(1), was obtained by the solvothermal reaction of MnCl2⋅4H2O and 1,4-naphthalenedicarboxylate (1,4-H2DNC) in dimethylacetamide organic solvents. Each Mn(II) atom is five-coordinated in a triagonal–bipyramidal coordination environment by four carboxylate O atoms from four different 1,4-DNC2–ligands and one O atom from a terminal DMA molecule. The neighboring Mn(II) atoms are doubly bridged by 1,4-DNC2–ligands to give a one-dimensional coordination polymeric chain [Mn(COO)2]n, and each chain is connected to four other different chains through µ4-kO1:kO2:kO3:kO4 1,4-DNC2–ligands to form a 3-D network of1. [ABSTRACT FROM AUTHOR]