Red-shifted photoluminescence is observed in the co-crystal of arene- and perfluoroarene-attached bipyridines, which is a perfectly layered array through arene–perfluoroarene interactions.

Single crystal structural analysis and thermogravimetric studies distinguished two kinds of electrostatic interactions: cation–π and arene–perfluoroarene interactions.

Dorsal-ventral pattern formation of the neural tube is regulated by temporal and spatial activities of extracellular signalling molecules. Sonic hedgehog (Shh) assigns ventral neural subtypes via activation of the Gli transcription factors. Shh activity in the neural progenitor cells changes dynamically during differentiation, but the mechanisms regulating this dynamicity are not fully understood. Here we show that temporal change of the intracellular cAMP level confers the temporal Shh signal, and the purinergic-type G-protein coupled receptor GPR17 plays an essential role for this regulation. GPR17 is highly expressed in the ventral progenitor regions of the neural tube and acts as a negative regulator of the Shh signal in chick embryos. While the activation of the GPR17-related signal inhibits ventral identity, perturbation of GPR17 expression leads to aberrant expansion of ventral neural domains. Notably, perturbation of GPR17 expression partially inhibits the negative feedback of Gli activity. Moreover, GPR17 increases cAMP activity, suggesting that it exerts its function by inhibiting the processing of Gli3 protein. GPR17 also negatively regulates Shh signalling in neural cells differentiated from mouse embryonic stem cells, suggesting that GPR17 function is conserved among different organisms. Our results demonstrate that GPR17 is a novel negative regulator of Shh signalling in a wide range of cellular contexts.

Flexible host frameworks of mononuclear coordination complexes were designed and encapsulated for several organic guest molecules through electrostatic interactions in their crystals, in which the unique guest recognitions and the uniform cavities were induced by fluorination of the coordination complexes. These unusual pseudopolymorphic cocrystal states of the fully fluorinated coordination complex, bis[bis(2,3,4,5,6-pentafluorobenzoyl)methanido]copper(II) (1), achieved several guest encapsulations, e.g., three benzenes; four toluenes; one, two, and four p-xylenes; one and two m-xylenes; one o-xylene; two mesitylenes; one durene; one and two anisoles; and two dimethoxybenzenes. Based on X-ray crystallographic studies of these crystals, the axial positions on the metal and the surrounding spaces by the pentafluorophenyl groups produced the flexible cavity, and the guest molecules were recognized by the cooperative effects of metal⋯π and arene–perfluoroarene interactions. However, the guest recognition of partially fluorinated coordination complexes, in which the pentafluorophenyl groups of 1 were replaced by 2,3,5,6-tetrafluorophenyl (2), 2,4,6-trifluorophenyl (3a), 2,6-difluorophenyl (4a), and 4-fluorophenyl (5) groups, clearly depended on the fluorination numbers, e.g., the number of encapsulated benzene molecules was three (1) > two (2 and 3a) > zero (4a and 5). No encapsulation was observed with any guest molecules for 4a, although cavity spaces similar to 1, 2, and 3a were present around the axial position on the metal as the result of steric hindrance of the ortho-substituted fluorines. Thermal studies of the corresponding guest releases also indicated that the number of fluorinations amplified the host–guest interactions. The cocrystals exhibit reversible guest encapsulation and release processes with the same and different guest molecules, which can be clearly monitored by color change and thermogravimetric observations. We now report the synthesis of fully and partially fluorinated β-diketonato Cu²⁺ complexes and their unique guest encapsulation phenomena depending on the position and the number of fluorine substitutions using X-ray crystallography and thermal analysis. These results prove that simple mononuclear complexes become host materials due to fluorination effects.