An unusual strategy for the design of coordination polymers based on the combination of large s cations and rigid d metal based secondary building units has been applied to the synthesis of the novel heterometallic potassium dicopper propionate [HKCu2Prop6] (Prop = propionate). The crystal structure of [HKCu2Prop6] is a dense 3D framework, which is constructed of alternating 0D [Cu2Prop4] SBUs and 1D-polymeric [K2(Prop···H···Prop)2]∞ “guide rods”. Temperature-dependent X-ray diffraction experiments have revealed the existence of a reversible single-crystal-to-single-crystal phase transition at ca. 195–200 K, which is followed by the temperature-driven ordering/disordering of flexible ethyl groups, minor rearrangements of the [Cu2Prop4] SBUs, and small distortions of the overall supramolecular motif. The low-temperature phase exhibits a large superstructural unit cell, whereas the high-temperature phase possesses a half unit cell. This transition, being first order, is additionally preceded by preliminary structural changes in the temperature range 180–195 K. Studies of magnetic properties have shown that the magnetic exchange between copper atoms in [HKCu2Prop6] remains unchanged upon the structural transformation. Similar behavior has been also revealed for the previously reported copper propionate hydrate [Cu2(H2O)2Prop4].

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The features of the coloration of the dorsal and ventral surfaces of the rare deep-sea Richardson’s ray Bathyraja richardsoni (Arhynchobatidae) in the length range from 14 to 146 cm have been studied and its ontogenetic changes have been traced. New data on the coloration of embryos, immature, maturing, and sexually mature individuals are presented. It is shown that variations in the coloration of the dorsal surface are insignificant, while the coloration of the ventral surface can vary significantly. The data obtained can be used in taxonomic and population studies, in the development of keys for species identification, in the preparation of faunal overviews and field guides, to facilitate understanding the features of coloration and its changes in deep-sea animals living in permanent darkness, and to expand knowledge about certain aspects of macro- and microevolution of deep-sea skates.

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