The exploration of supramolecular interactions stemming from the [UO2(NCS)4(H2O)]2− tecton and substituted pyridinium cations

Abstract

The synthesis and crystal structures of eight compounds containing the anionic uranyl isothiocyanate tecton [UO₂(NCS)₄(H₂O)]²⁻, charge balanced by substituted pyridinium cations (4XpyH: X = Cl, Br, I, SCN, CH₃, NH₂, N(CH₃)₂) are reported. Hydrogen bonding interactions between coordinated water molecules and the non-coordinated sulfur atoms (O–H₂⋯S) of the adjoining tectons facilitate the formation of infinite ‘pseudo’ chains of inorganic tectons. The substituted pyridinium cations were paired with these fixed uranyl isothiocyanate tectons due to their ability to sustain multiple intermolecular interactions with the sulfur atoms of the uranyl tectons, thus promoting assembly. The variation of the substituent group bound to the organic cations allowed for the resulting non-covalent interactions to be systematically assessed in order to determine their relative effects upon packing. Additionally, respective acceptor–donor pairings as well as the relative strengths of the halogen, pseudohalogen [C–X⋯A (X = Cl, Br, I, SCN and A = O, S)] and hydrogen bonding [R–H⋯A (R = N, C and A = O, S, π)] interactions were investigated. The acceptor–donor relationships emulated hard–soft pairings and consequently increased in strength as a function of this trend.