Molecular structures of the inclusion complexes β-cyclodextrin–1,2-bis(4-aminophenyl)ethane and β-cyclodextrin–4,4′-diaminobiphenyl; packing of dimeric β-cyclodextrin inclusion complexes

Abstract

The present investigation is part of an ongoing study on the influence of the long end-functonalized guest molecules DBA and BNZ in the crystal packing of beta-cyclodextrin (betaCD) dimeric complexes. The title compounds are 2:2 host:guest complexes showing limited host-guest hydrogen bonding at the primary faces of the betaCD dimers. Within the betaCD cavity the guests exhibit mutual pi...pi interactions and between betaCD dimers perpendicular NH...pi interactions. The DBA guest molecule exhibits one extended and two bent conformations in the complex. The BNZ guest molecule is not planar inside betaCD, in contrast to the structure of BNZ itself, which indicates that the cavity isolates the molecules and forbids the pi...pi stacking of the aromatic rings. NMR spectroscopy studies show that in aqueous solution both DBA and BNZ form strong complexes that have 1:1 stoichiometry and structures similar to the solid state ones. The relative packing of the dimers is the same in both complexes. The axes of two adjacent dimers form an angle close to 20 degrees and have a lateral displacement approximately 2.45 A, both of which characterize the screw-channel mode of packing. Although the betaCD/BNZ complex indeed crystallizes in a space group characterizing the latter mode, the betaCD/DBA complex crystallizes in a space group with novel dimensions not resembling any of the packing modes reported so far. The new lattice is attributed to the three conformations exhibited by the guest in the crystals. However, this lattice can be transformed into another, which is isostructural to that of the betaCD/BNZ inclusion complex, if the conformation of the guest is not taken into account.

Spatially dependent H-bond dynamics at interfaces of water/biomimetic self-assembled lattice materials

“…that indicates, on average, 4.5-7 water molecules form strong H bonds with one β-CD (Fig. 1 and SI Appendix, section S1), and is in line with previous studies (26)(27)(28)(29)(30). Furthermore, our previous vibrational sum-frequency generation (VSFG) study (19), X-ray diffraction (XRD), and atomic force microscopy-IR spectroscopy (AFM-IR) results (SI Appendix, section S3) suggest that there could be heterogeneity in the strongly bound water distribution of the self-assembly.…”

Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

“…The pair of L-NAcTrp molecules inside the dimer are found in orientational disorder, i.e., the guest exhibits a major orientation, molecules C and D (occupancy 65%), and a co-existing minor orientation (molecules E and F , occupancy 35%) in a statistical fashion. The dimers pack along the axis a at an angle of 19° thus forming a broken channel (Intermediate packing) [ 10 , 27 ]. The mean distance of the centers of mass of two consecutive β-CD dimers is 5.78 Å. Co-crystallized with each dimer, 21.45 water molecules are found distributed over 36 sites.…”

“…Moreover, trends in enantioselectivity do not follow trends in association constants, i.e., the association constants for the β-CD complexes of both enantiomers of N -acetyltyrosine, N -acetylphenylalanine and N -acetyltryptophan are in decreasing order, whereas their enantioselectivity (ratio of the binding constants, K , of the L- to the D-enantiomer) shows an increasing order (1.04, 1.1 and 1.34, respectively). X-ray crystallography, on the other hand, can improve our understanding of chiral recognition by CDs at the atomic level by providing insight into the interactions and the fit of the guest in the cavity, taking into account that crystal lattice forces may introduce additional and more stringent parameters for the enantiodiscrimination [ 9 – 10 ]. However, the crystallographic structures of diastereomeric complexes of CDs with chiral guest molecules in the literature are scarce.…”

Κρυσταλλογραφική Μελέτη Δομής Βιολογικών Μακρομορίων

“…H ιδιότητα αυτή είναι πολύ χρήσιµη αφού επιτρέπει τη γνώση της κρυσταλλικής διευθέτησης ενός συµπλόκου, έχοντας ως µοναδική πληροφορία τις διαστάσεις της µοναδιαίας κυψελίδας του. Υπάρχουν όµως και διαφοροποιήσεις οι οποίες οφείλονται στο ξενιζόµενο µόριο 186. Οι τέσσερεις διατάξεις των διµερών των συµπλόκων της βCD.…”

“…Οι τέσσερεις διατάξεις των διµερών των συµπλόκων της βCD. Κάθε µόριο κυκλοδεξτρίνης παριστάνεται από το επτάγωνο των γλυκοζιτικών οξυγόνων Ο4n 186. Στις περιπτώσεις του διαύλου (CH) και της ενδιάµεσης διευθέτησης (IM), τα διµερή διατάσσονται παράλληλα κατά µήκος του άξονα c και a αντιστοίχως.…”