| Summary: | In this work, we report a study of two thermotropic liquid crystalline samples showing a not common mesophase behavior. The samples, namely a di-benzyloxy biphenyl derivative labelled <b>9/2 RS/RS</b>, and a bimesogenic liquid crystal labelled <b>L1</b>, show a direct transition between two isotropic phases followed, at lower temperatures, by the optically isotropic, 3D structured, cubic phase. These systems have been investigated by means of <sup>1</sup>H NMR diffusometry and <sup>1</sup>H NMR relaxometry in order to characterize their isotropic–isotropic’–cubic mesophase behavior, mainly on the dynamic point of view. In particular, the temperature trend of the self-diffusion coefficients measured for both samples allowed us to significantly distinguish between the two isotropic phases, while the temperature dependence of the <sup>1</sup>H spin-lattice relaxation time (T<sub>1</sub>) did not show significant discontinuities at the isotropic–isotropic’ phase transition. A preliminary analysis of the frequency-dependence of <sup>1</sup>H T<sub>1</sub> at different temperatures gives information about the main motional processes active in the isotropic mesophases.
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