A compound of the formula R1(CR3=CR4)nAr(CR4=CR3)nR2 wherein: n is 0 or 1; Ar represents aryl or heteroaryl having 1-5 aromatic rings which may be chain or fused or a combination of chain and fused, which may be substituted with alkoxy, fluoro, fluoroalkyl or cyano and which in the case of a 5-membered ring nitrogen heteroatom may be N-substituted with aryl or substituted aryl optionally further substituted with alkoxy, fluoro, fluoroalkyl or cyano; R1 and R2 independently represent aryl or nitrogen, oxygen or sulphur-containing heteroaryl having two or four fused aromatic rings one of which may be 5-membered and optionally substituted by aryl or heteroaryl having 1-5 chain or fused aromatic rings which may be further substituted with alkoxy, fluoro, fluoroalkyl or cyano; and R3 and R4 independently represent hydrogen, methyl, ethyl or benzyl. Also provided is a method of making a compound having electroluminescent and/or electroconductive properties, which comprises condensing an aromatic dialdehyde with a methyl-substituted heteroaryl compound having two or four fused rings which may be unsubstituted or may be further substituted by aryl or heteroaryl having fromone to four aromatic rings, said aryl or heteroaryl substituent or substituents optionally being substituted with one or more fluoro, fluoroalkyl or cyano substituents. The condensation may be carried our in acetic anhydride under reflux. The compounds may be incorporated e.g. as an electron transport layer into an optical light emitting diode, where embodiments can provide high electron mobility, low turn-on voltage and good lifetime, or into an electrostatic imaging member. A composition is provided comprising a compound as above and a second host or electron transport material and/or at least one dopant.