Thirteen N-butylpyridinium salts, including three monometallic [C 4 Py] 2 [MCl 4 ], nine bimetallic [C 4 Py] 2 [M 1Àx a M x b Cl 4 ]a nd one trimetallicc ompound [C 4 Py] 2 [M 1Ày-z a M y b M z c Cl 4 ](M = Co, Cu, Mn; x = 0.25, 0.50 or 0.75 and y = z = 0.33), were synthesized and their structure and thermala nd electrochemical properties were studied. All compoundsa re ionic liquids(ILs) with melting points between 69 and 93 8C. X-ray diffraction provest hat all ILs are isostructural. The conductivity at room temperature is be-tween1 0 À4 and1 0 À8 Scm À1 .S ome Cu-based ILs reach conductivities of 10 À2 Scm À1 ,w hichi s, however, probablyd ue to IL dec. This correlates with the opticalb andgap measurementsi ndicating the formation of large bandgap semiconductors.A te levated temperaturesa pproaching the melting points, the conductivities reach up to 1.47 10 À1 Scm À1 at 70 8C. The electrochemical stability windowso ft he ILs are between2.5 and 3.0 V.