Naphthalenediimides,　an　attractive　class　of　electron-deficient　organic　dyes　with　rich　redox　and　photoredox　properties,　have　been　investigated　extensively　as　building　blocks　for　coordination　networks　or　metal–organic　frameworks　in　recent　decades.　However,　most　of　the　available　work　has　focused　on　d-block　metal　cations　rather　than　f-block　lanthanide　ions,　whose　complexes　exhibit　a　large　variability　in　coordination　numbers.　In　this　article,　four　coordination　polymers　composed　of　naphthalenediimides　and　lanthanide　cations,　namely　catena-poly[[[tris(nitrato-κ2O,O′)lanthanide]-bis{μ-N,N′-bis[(1-oxidopyridin-1-ium-3-yl)methyl]-1,8:4,5-naphthalenetetracarboxdiimide-κ2O:O′}-[tris(nitrato-κ2O,O′)lanthanide]-μ-N,N′-bis[(1-oxidopyridin-1-ium-3-yl)methyl]-1,8:4,5-naphthalenetetracarboxdiimide-κ2O:O′]　methanol　disolvate],　{[Ln(C26H16N4O4)1.5(NO3)3]·CH3OH}n,　with　Ln　=　Eu,　1,　Gd,　2,　Dy,　3,　and　Er,　4,　have　been　successfully　synthesized　under　hydrothermal　conditions.　Single-crystal　X-ray　diffraction　analyses　revealed　that　the　four　compounds　are　isomorphic　and　that　each　asymmetric　unit　contains　one　nine-coordinated　Ln　centre,　one　and　a　half　diimide　ligands,　three　nitrate　anions　and　one　uncoordinated　methanol　molecule.　In　addition,　each　metal　centre　is　surrounded　by　nine　O　atoms　in　a　distorted　tricapped　trigonal–prismatic　geometry.　Two　centres　are　bridged　by　two　cis　ligands　to　form　a　ring,　which　is　further　bridged　by　trans　ligands　to　generate　one-dimensional　chains.　Neighbouring　chains　are　stacked　via　π–π　interactions　between　pyridine　rings　to　give　a　two-dimensional　structure,　which　is　stabilized　by　π–π　interactions　between　naphthalene　rings,　forming　the　final　three-dimensional　supermolecular　network.　Solid-state　optical　diffuse-reflectance　spectral　studies　indicate　that　compound　4　is　a　potential　wide　band　gap　semiconductor.　©　International　Union　of　Crystallography,　2019