Preface

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

“…An interesting feature of the substantial number of uranyl compounds [37,59], including seven structures reported herein, is the connection of adjacent coordination polyhedra through the common bridging vertices that can be depicted as a sort of a flexible ball-insocket arrangement. This flexibility results in the relative ease of adaptation of layered [(UO 2 ) x (TO 4 ) y ] zÀ systems to variable cations and other species present in the solutions during crystallization.…”

Actinyl Compounds with Hexavalent Elements (S, Cr, Se, Mo) – Structural Diversity, Nanoscale Chemistry, and Cellular Automata Modeling

“…It corresponds to the structural unit shown in Figure 19b (graph depicted in Figure 19a), which has the composition [(AnO 2 )(TO 4 ) 2 -(H 2 O)] and is observed in a large number of actinyl oxysalts, including uranyl selenates. [7] It is of interest that this unit can also be produced by using the CA described above. The results of computer modeling may shed some light into the process of self-assembly in uranyl selenate systems.…”

“…In actinyl sulfates, molybdates, selenates, and chromates, actinyl ions are equatorially coordinated by O atoms of tetrahedral complexes or OH groups and H 2 O molecules. The most frequently observed coordination is fivefold, leading to the formation of a flattened pentagonal bipyramid, AnO 7 , centered by an actinide ion (Figure 1b). Usually, coordination of an actinyl ion by a TO 4 tetrahedron is monodentate (AnO 7 and TO 4 groups share one O atom only), though bidentate coordination is quite common in uranyl sulfates.…”

“…The most frequently observed coordination is fivefold, leading to the formation of a flattened pentagonal bipyramid, AnO 7 , centered by an actinide ion (Figure 1b). Usually, coordination of an actinyl ion by a TO 4 tetrahedron is monodentate (AnO 7 and TO 4 groups share one O atom only), though bidentate coordination is quite common in uranyl sulfates. [9] Polymerization of actinyl ions through tetrahedral oxyanions results in formation of a whole family of extended complexes with different compositions and topologies (Figure 1c) Figure 2a, b.…”

“…From the fundamental viewpoint, these compounds are remarkable in their wide range of compositions and structures originating from combinatorial and topological possibilities of linkage of basic structural elements that leads to a large variety of topologi-cal and geometrical isomers. A review of the whole range of structures that occur in actinide oxysalts with the elements of the sixth group of the periodic table was published elsewhere; [7] some recent results are summarized in ref. [8] In this microreview, we outline the basic structural features of one particular group of these compounds, namely those in which actinyl ions are polymerized through tetrahedral oxyanions TO 4 (T = S, Cr, Se, and Mo).…”