PNNL

Abstract

Reactions of BiI3/CuI mixtures with tetrahydrothiophene (THT) in toluene produce 2-D sheet networks BiCu3I6(THT)n (n = 2, 3, or 4), depending on reaction conditions. All three compounds are based on BiI6 octahedra which share pairs of (eta2-I)2 with the Cu(I) structural building units (SBU). In the case of n = 3, Cu(I) SBUs consist of closed Cu3(eta2-THT)3 rings, while for n = 4, the SBU rings are opened to form (THT)2Cu(eta2-THT)Cu(eta2-THT)Cu(THT)2 arcs. The removal of a THT in BiCu3I6(THT)2 collapses the copper SBU to Cu3(eta2-THT)2 in which a pair of eta3-I bridge Cu/Cu/Bi, supporting a close Cu…Cu interaction of 2.677 Å. Formed along with BiCu3I6(THT)2 is the more complex Bi3.33Cu12I22(THT)8 which shares many structural features with the former complex. Products of SbI3/CuI with THT in toluene were also prepared. The SbCu3I6(THT)2 network shows Cu3(eta2-THT)2 SBUs, like its Bi cogener, but the pairs of eta3-I bridge Cu/Cu/Cu, forming Cu6I6 barrels each with a trio of 2.626 Å Cu…Cu interactions. Isolated SbI3 units are also present, with alternating layers having SbI3 stacked above the Cu6I6 barrels. A molecular compound, Bi3Cu3I12(THT)6 consists of a face-sharing Sb3I12 stack, which is bonded in asymmetric fashion through eta2-I and eta3-I with a Cu(THT)2 and a (THT)Cu(eta2-THT)Cu(THT)2 SBU. The metal-halide bonds were investigated via QTAIM and NLMO analyzes, demonstrating that these bonds are mostly ionic in nature and occur between the Bi/Sb and I p orbitals. Hirshfeld analysis shows significant H…H and H…I interactions between layers or molecules. All complexes show clean ligand losses via thermogravimetry. Diffuse reflectance spectroscopy (DRS) reveals band edges for the Bi species of 1.71-1.82 eV, while those for the neutral Sb complexes are in the range of 1.94-2.06 eV. Mapping of the electronic structure via Density of State calculations indicate population of antibonding Bi/Sb-I orbitals in the excited state.