Trapping of Octameric Water Cluster by the Neutral Unclosed Cryptand Environment

Abstract

Unclosed cryptands (UCs) are neutral and easily accessible compounds with 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 3Dframework for study of supramolecular assemblies. Herein, one example of the discrete eight-membered water cluster trapped in the matrix of UC 1 is presented. X-ray, ATR FT-IR, and DFT studies indicate extraordinary stability of this assembly, which originated from the cumulative interplay of many noncovalent interactionshydrogen bonds and London dispersion forces.

Stabilization of Near Identical Hydrogen Bonded Octameric Water Clusters in Crystal Structures of Three Distinct Non-Charged Polyamide Macrocyclic Host Molecules

“…The host 2 has been synthetized and its crystal structure was determined by X-ray crystallography. It was found, unexpectedly, that host 2 contains near the same octameric water cluster as previously found in the crystal structures of analogs 1a [ 33 ] and 1b [ 10 ] . A comparative crystal structure analysis has been carried out to identify the role of macrocyclic skeleton and lariat arm on the formation of water clusters in the crystal lattice of hosts 1a – b and 2 .…”

“…Due to their inherent flexibility, they are able to adjust their shape to highly demanding guests, in particular anions. Lately, we showed that 26-membered pentamide unclosed cryptands are able to accommodate octameric water clusters in their structure [ 10 , 33 ], proving that such molecules are a good choice for studying the hydration phenomena of small organic compounds, as well as serving as a model for more complicated structures of biological importance. It may prove very useful as studying the hydration behavior of biological molecules still presents a challenge for modern science [ 34 , 35 ].…”

Catching the chloride: searching for non-Hofmeister selectivity behavior in systematically varied polyamide macrocyclic receptors

“…Unclosed cryptands Uc1-Uc5 [30][31][32] are structurally related to previously mentioned macrocycles M1-M13, however, only one side contains meso diacid moiety (dipicolinic acid), while the other side is constructed here from diacid derived from 2,6-dihydroxyaniline. The nitrogen atom of the latter group is a part of amide equipped with an additional p-nitrophenyl substituent (lariat arm) which is introduced at the intraannular position of the macroring.…”

“…8). Firstly, although macrocyclic scaffold is quite well preorganized for the binding of various guests via H-bond interactions, 31,32,45,46 complexation of a guest which is solely an H-bond acceptor (such as chloride), requires a 180°degree rotation of the lariat arm accompanied with the breaking of the intramolecular H-bond. This in turn, enables very strong, albeit not highly directional interaction with an anion (d N⋯Cl − = 3.12 Å, ≤159°), which has no direct contact with the TBA + counterion (Fig.…”

Steric Effect of a Capping Ligand on the Formation of Supramolecular Coordination Networks of Ni(II): Solid-State Entrapment of Cyclic Water Dimer

“…For the importance in both chemical and biological processes, the water–water interaction in water aggregates of varying degree has been the subject of both experimental and theoretical research in the past few decades. 1 − 15 These efforts have been primarily targeted to elucidate the structure–property correlations in such systems. In the biological systems, water maintains the stability and proper functioning of enzymes and proteins.…”