Low-Dimensional Hybrid Halides of Cu(I) and Ag(I) with Organic and Transition Metal Complex Cations

Abstract

Recent years have seen a tremendous surge in the amount of research dedicated towards the structural and functional exploration of organic-inorganic hybrid halometallates, shedding light to newer directions in the domain of solid-state chemistry. In that regard, coinage metal (Cu, Ag, Au) based hybrid materials have particularly emerged interesting due to their superior stability along with structural diversity and tunable dimensionality arising from numerous coordination environments around the metal ions, leading to fascinating physical properties. This thesis primarily discusses about the synthesis of alluring d10-Cu(I) and Ag(I) halide materials bearing possible metallophilic (M---M) interactions, and their various application possibilities. Here, we have discussed about single crystals of a Cu(I) halide-based perovskite-like organic–inorganic hybrid, (TMA)Cu2Br3, (TMA = tetramethylammonium), consisting of one-dimensional inorganic anionic chains of –(Cu2Br3)nn-–, where the Cu(I)–Cu(I) distance indicates the possibility of a newly coined phenomenon called excitonic cuprophilic interactions, and consequently exhibiting an impressive photoresponsive effect. Then, (TMA)AgBr2 (TMA = tetramethylammonium) crystals, comprising of 1D –(AgBr2)nn-– chains stabilized by TMA cations with a periodic arrangement of shorter and longer Ag(I)---Ag(I) bonds are studied. Theoretical calculations show alternate -like bonding involving dxy orbitals of 4d10 Ag(I), attributing to the ultralow thermal conductivity and thermally deactivated electrical transport in the system. Thereafter, (4,4-bpy)Ag2Br4 (4,4-bpy = 4,4-bipyridine) system is investigated, which crystallizes in the non-centrosymmetric P21 space group at ambient condition, thereby showing ferroelectricity. Interestingly, it undergoes phase transition around ~330 K to induce centrosymmetry in the compound (with space group P21/c), and losing its ferroelectric behavior, therefore demonstrating intriguing structure-property correlation. Finally, we have discussed about [Ru(2,2-bpy)3]2Ag6Br12 system (2,2-bpy = 2,2-bipyridine), which consists of [Ru(2,2-bpy)3]3+, as a transition metal cation, electrostatically stabilized by 2D anionic chains of (Ag6Br11)n5n- and Br- anions, exhibiting interesting emission properties originating from the influence of the anionic structure. Further, it shows ultra-low value of thermal conductivity due to the presence of possible argentophilic (Ag---Ag) interactions in the system.