A new viologen(4,4'-bipyridinium)-based complex [N-ethyl-4,4'-bipyridinium][CdBr4], in which N-ethyl-4,4'-bipyridinium (EQ(2+)) has been generated in situ, has been synthesised via hydrothermal reaction and structurally characterised by single-crystal X-ray diffraction. [N-ethyl-4,4'-bipyridinium][CdBr4] features an isolated structure, based on an N-ethyl-4,4'-bipyridinium moiety and a cadmium atom terminally bound by four bromine atoms. Photoluminescence investigation reveals a broad and intense emission in blue region, which may originated from pi -> pi* charge-transfer interaction of the N-ethyl-4,4'-bipyridinium moiety.