Here we describe the preparation, characterisation, liquid crystal properties and photophysical studies of new potassium salts of tetrakis(β-diketonate)europium(III) complexes based on long-chained symmetrical and unsymmetrically substituted 1,3-dialkyloxyphenyl-β-diketones ligands, K[Eu(OOR(n)R(m))4] (R(n) = OC6H4OCnH2n+1; R(m) = OC6H4OCmH2m+1; n = m = 8, 10, 12, 14, 16; n = 4, 8, m = 12, 16; n = 12, m = 16). All compounds exhibit mesomorphic and luminescence behaviour, regardless the presence of symmetrical or unsymmetrical ligands. It has been shown that the shortest molecular lengths, established by the summation of the two alkyl chains at the substituents of the β-diketonate ligand, give rise to more effective mesophase transition temperatures, while the asymmetry favours higher clearing temperatures. Related to the ionic salts based on long-chained pirazolium cations [H2pzR(n)]+ (R(n) = OC6H4OCnH2n+1; n = 4, 6, 8, 10, 12, 14, 16, 18) and tetrakis(1,3-bis(methoxyphenyl)propane-1,3-dionate)europium(III) as anion, they have also been studied and proved to be luminescent materials. By contrast, none of them was found to be mesomorphic. Therefore, the strategically increased chain length at the cation did not show to be effective for achieving liquid crystal properties. Integration of one of these luminescent europium complexes onto a polymeric PMMA matrix was positively evaluated towards its use as a temperature sensor and fluoride or cyanide ion sensor.