“…The transition metal coordination chemistry of thiocyanate or isothiocyanate ligands has extensively been developed for several decades mostly in view of the significance of the corresponding complexes in new fields like crystal engineering, supramolecular chemistry and host-gust chemistry [1,[11][12][13][14][15][16]. The well-known tetrahedral [Co(NCS) 4 ] 2À anion is useful building block, which is in combination with various positively charged moieties and gives rise to molecular solids with diverse physical properties and use as optical, magnetic and conductive materials [17][18][19][20] [21][22][23], in which the effect of the change of the substituted group on the phenyl ring of benzyl group of the cation on the crystal system, space group, weak interactions, the stacking mode of the anions and cations, and the magnetic properties have been systematically investigated. We here present synthesis, FT-IR, UV-Vis spectra, ESI-MS, single crystal structures, weak interactions, magnetic properties and luminescent properties of two new organic-inorganic molecular solids of [Co(NCS) 4 …”