If there are suitable molecular interactions between nematic and non-nematic molecules and the resulting complexes have suitable length-to-width ratio, nematic-isotropic phase transition temperature (T-NI) can rise contrary to usually observed fall. This types of rise in T-NI were observed in binary systems composed of 5CB and aromatic acids, and were ascribed to the formation of hydrogen bonded complexes between 5CB solvent and non-nematic solutes [1-3]. We newly found that the T-NI rose in the binary systems in which there can not be expected to exist any hydrogen-bonded complexes. We studied the possibility of the complex formation by molecular interactions other than intermolecular hydrogen bonding between 5CB and non-nematic solutes. Their consequences on thermal properties of binary systems were investigated.