Four 2,2′-dipyridylamino-s-triazine-substituted ligands, each of which incorporate different aromatic substituents (phenoxo, 4-CN-phenoxo and benzylamino) with different degrees of bulk and flexibility, have been formed and incorporated into a number of mononuclear FeII complexes of type trans-[FeII(L)2(NCX)2]·solvent (in which X = S, Se and BH3). These ligands were designed to promote π–π stacking between complexes. The complexes reported have been comprehensively characterised using single-crystal diffraction techniques in combination with magnetic susceptibility measurements. Light-induced excited spin-state trapping (LIESST) measurements have been performed on selected complexes. Light irradiation has shown the occurrence of a reversible photoswitching process at low temperature.