Review Lecture: Topography and Topology in Solid-State Chemistry

摘要: A survey of recent activity and current trends in solid-state chemistry reveals that several novel seemingly unrelated physicochemical phenomena, together with some bio-organic, mineralogical metallurgical attributes the solid-state, can now be interconnected. Four main topics are discussed. First, so far as behavioural patterns organic solids concerned, topochemical control is often crucial, it transpires reactivity many types unsaturated molecules governed more by precise molecular orientation stacking sequences within crystal structure than intrinsic electronic properties molecule itself. This fact has led to synthesis, strategem ‘crystal engineering’ (Schmidt 1971), stereochemically-pure, products also single-crystal, extended-chain polymers both which difficult if not impossible prepare conventional (solution) techniques. It absolute asymmetric syntheses, under abiotic conditions, from optically inactive materials, inducing or surface reactions chiral crystals. The selectivity high yields gas solids, facile conversion polymer crystals their folded-chain forms other manifestations chemistry. Structural defects, too, play a dominant role, they account for infrequent production topochemically ‘forbidden’ photo-induced reactions. existence stress-induced phase transformations structure-mimicry (in guest species assume host) further discoveries this general area. Second, control, needs distinguished topotaxy, important inorganic particularly intercalation (or its reverse) charged neutral accommodated between individual sheets layered compounds, thereby resulting expansion interlayer separation distances and, generally, modification sequence. Exceptionally selective may carried out interlamellar spaces silicate minerals, engineering, sense reactant locked well defined orientations conducive subsequent reaction matrixes, again becomes feasible proposition. third topic discussion faults, serve nexus structural principles general. relations characteristics range plausible mechanisms interconversion based on martensitic transformation, follows logically; changes coordination number going NaC1- CsC1-type structures example) rationalized terms continuous topological variation. Stacking faults intimately connected partial dislocations antiphase boundaries, these, turn, figure concepts understanding ultramicrostructure grossly non-stoicheiometric theme fourth discussed here. chemical consequences linear planar surveyed, there being summarizing role fuller one single, double pivoting crystallographic shear planes. Relations block adumbrated; merit introducing notion cylindrical fault inter alia relate ReO 3 -type tungsten bronze structures, outlined. considerable analogical value dislocation theory interpreting ultramicrostructural non-metallic especially revealed electron microscopy, emphasized throughout.