Molecular recognition of crown ethers by β-lactose in aqueous solutions

2006 ◽  
Vol 16 (1) ◽  
pp. 45-46
Author(s):  
Nadezhda L. Volkova ◽  
Elena V. Parfenyuk
Keyword(s):  
Molecular Recognition ◽  
Aqueous Solutions ◽  
Crown Ethers

scholarly journals Complex Uranyl Dichromates Templated by Aza-Crowns

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 462 ◽  
Author(s):  
Oleg Siidra ◽  
Evgeny Nazarchuk ◽  
Dmitry Charkin ◽  
Stepan Kalmykov ◽  
Anastasiya Zadoya
Keyword(s):  
Aqueous Solutions ◽  
Crown Ethers ◽  
Room Temperature ◽  
Organic Molecules ◽  
Negative Charge ◽  
Uranyl Compounds ◽  
One Dimensional ◽  
Chain Complexes ◽  
Aza Crown Ethers

Three new uranyl dichromate compounds templated by aza-crown templates were obtained at room temperature by evaporation from aqueous solutions: (H2diaza-18-crown-6)2[(UO2)2(Cr2O7)4(H2O)2](H2O)3 (1), (H4[15]aneN4)[(UO2)2(CrO4)2(Cr2O7)2(H2O)] (H2O)3.5 (2) and (H4Cyclam)(H4[15]aneN4)2[(UO2)6(CrO4)8(Cr2O7)4](H2O)4 (3). The use of aza-crown templates made it possible to isolate unprecedented and complex one-dimensional units in 2 and 3, whereas the structure of 1 is based on simple uranyl-dichromate chains. It is very likely that the presence of relatively large organic molecules of aza-crown ethers does not allow uranyl chromate chain complexes to condense into the units of higher dimensionality (layers or frameworks). In general, the formation of 1, 2, and 3 is in agreement with the general principles elaborated for organically templated uranyl compounds. The negative charge of the [(UO2)(Cr2O7)2(H2O)]2−, [(UO2)2(CrO4)2(Cr2O7)2(H2O)]4− and [(UO2)3(CrO4)4(Cr2O7)2]6− one-dimensional inorganic motifs is compensated by the protonation of all nitrogen atoms in the molecules of aza-crowns.

scholarly journals Molecular Recognition and Conductance in Crown Ethers

2003 ◽  
Vol 125 (46) ◽  
pp. 13936-13937 ◽  
Author(s):  
Chris Liu ◽  
Derek Walter ◽  
Daniel Neuhauser ◽  
Roi Baer
Keyword(s):  
Molecular Recognition ◽  
Crown Ethers

scholarly journals Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

2017 ◽  
Vol 13 ◽  
pp. 1572-1582 ◽  
Author(s):  
Spyros D Chatziefthimiou ◽  
Mario Inclán ◽  
Petros Giastas ◽  
Athanasios Papakyriakou ◽  
Konstantina Yannakopoulou ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Molecular Recognition ◽  
Aqueous Solutions ◽  
Crystalline State ◽  
Dimeric Complex ◽  
Nmr Studies ◽  
Guest Molecules ◽  
Crystallographic Order

The enantioselectivity of β-cyclodextrin (β-CD) towards L- and D-N-acetyltryptophan (NAcTrp) has been studied in aqueous solution and the crystalline state. NMR studies in solution show that β-CD forms complexes of very similar but not identical geometry with both L- and D-NAcTrp and exhibits stronger binding with L-NAcTrp. In the crystalline state, only β-CD–L-NAcTrp crystallizes readily from aqueous solutions as a dimeric complex (two hosts enclosing two guest molecules). In contrast, crystals of the complex β-CD–D-NAcTrp were never obtained, although numerous conditions were tried. In aqueous solution, the orientation of the guest in both complexes is different than in the β-CD–L-NAcTrp complex in the crystal. Overall, the study shows that subtle differences observed between the β-CD–L,D-NAcTrp complexes in aqueous solution are magnified at the onset of crystallization, as a consequence of accumulation of many soft host–guest interactions and of the imposed crystallographic order, thus resulting in very dissimilar propensity of each enantiomer to produce crystals with β-CD.

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