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Your search keyword '"Dąbrowa, Kajetan"' showing total 36 results
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36 results on '"Dąbrowa, Kajetan"'

30. Solid-state entrapment of water clusters by 26-membered pentamide unclosed cryptands - probing the <italic>para</italic>-substituent effect.

Author

Dąbrowa, Kajetan, Jurczak, Janusz, and Ceborska, Magdalena

Subjects
*HOST-guest chemistry, *CRYPTANDS, *HYDROGEN bonding, *WATER clusters, *SOLID state chemistry
Abstract

Twenty six membered unclosed cryptands end-capped with nitrophenyl (1), phenyl (2), and methoxyphenyl (3) amide substituent (lariat arm) were characterized by single crystal X-ray analysis to reveal the role of para-substituent on the solid-state stabilization of water clusters. Host molecules 1 and 3 crystallize in the same space group (P-1) forming isostructural assemblies with the same entrapped octameric water cluster build from a cyclic tetramer connected with four up-and-down positioned pendulous water molecules. In striking contrast, the host molecule 2 bearing the unsubstituted amido-phenyl group crystallizes in P21/c space group in which two host molecules stabilize acyclic water chain. This distinct crystallization behavior may be rationalized by differences in the electrostatic potential surfaces between hosts 1 and 3 as compared with 2 (para-substituent effect). [ABSTRACT FROM AUTHOR]

Published
2018
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31. Chirality of 20-membered unclosed cryptand: Macroring distortion via lariat arm modification.

Author

Jurczak, Janusz, Sobczuk, Adam, Dąbrowa, Kajetan, Lindner, Marcin, Niedbała, Patryk, and Stepniak, Pawel

Subjects
CHIRALITY, CRYPTANDS
Abstract

Some of 19-membered unclosed cryptands were recognized as chiral species in a solid state. While, in terms of 20-membered macrocycle, we tune the lariat arm, developing the synthesis of α- and β-naphthyl terminated moieties to gain the structural control over chirality phenomena of these systems. Indirect synthetic approach delineates the way to reach both target structures. Solely, macrocycle functionalized with the β-naphthyl group is capable of desirable interactions with the frame of entity inducing its stronger bending that leads to the chiral crystals formation. Their structural features were examined by single crystal X-ray diffraction and chiroptical method, represented by ECD/UV spectroscopy. [ABSTRACT FROM AUTHOR]

Published
2018
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32. Chloride-Templated Macrocyclization and Anion-Binding Properties of C2-Symmetric Macrocyclic Ureas from Sucrose.

Author

Łęczycka-Wilk, Katarzyna, Dąbrowa, Kajetan, Cmoch, Piotr, and Jarosz, Sławomir

Subjects
*CHLORIDES, *ANIONS, *MACROCYCLIC compounds, *HETEROCYCLIC compounds, *DISACCHARIDES, *SUCROSE, *ACETATES
Abstract

A high-yielding, one-pot simultaneous synthesis and full characterization of two regioisomeric C2-symmetrical macrocycles 3a and 3b from triphosgene and readily available hexa-O-benzyl-6,6'-diaminosucrose 1 is reported. The efficient macrocyclization (90% overall yield, -1:1 ratio of 3a vs 3b) is attributed to favorable steric constraints and to a templation by a chloride anion. 1H NMR titration studies and theoretical predictions revealed that both receptors show similar affinity for acetate and benzoate anions and enhanced preference for chloride over H2PO4-. [ABSTRACT FROM AUTHOR]

Published
2017
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36. Trapping of Octameric Water Cluster by the NeutralUnclosed Cryptand Environment.

Author

Dąbrowa, Kajetan, Ceborska, Magdalena, and Jurczak, Janusz

Subjects
*WATER clusters, *CRYPTANDS, *FUNCTIONAL groups, *SUPRAMOLECULAR chemistry, *MOLECULAR self-assembly
Abstract

Unclosed cryptands (UCs) are neutraland easily accessible compoundswith precisely defined spatial arrangement of various functional groups.They readily form crystals with a unusually high packing efficiency(≥0.8), thus providing a well-suited 3D-framework for studyof supramolecular assemblies. Herein, one example of the discreteeight-membered water cluster trapped in the matrix of UC 1 is presented.X-ray, ATR FT-IR, and DFT studies indicate extraordinary stabilityof this assembly, which originated from the cumulative interplay ofmany noncovalent interactionshydrogen bonds and London dispersionforces. [ABSTRACT FROM AUTHOR]

Published
2014
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