Supramolecular self-assemblies of beta-cyclodextrins with aromatic tethers: factors governing the helical columnar versus linear channel superstructures.
A series of 6-O-(p-substituted phenyl)-modified beta-cyclodextrin derivatives, i.e., 6-O-(4-bromophenyl)-beta-CD (1), 6-O-(4-nitrophenyl)-beta-CD (2), 6-O-(4-formylphenyl)-beta-CD (3), 6-phenylselenyl-6-deoxy-beta-CD (4), and 6-O-(4-hydroxybenzoyl)-beta-CD (5), were synthesized, and their inclusion complexation behavior in aqueous solution and self-assembling behavior in the solid state were comparatively studied by NMR spectroscopy, microcalorimetry, crystallography, and scanning tunneling microscopy. Interestingly, (seleno)ethers 1-4 and ester 5 displayed distinctly different self-assembling behavior in the solid state, affording a successively threading head-to-tail polymeric helical structure for the (seleno)ethers or a mutually penetrating tail-to-tail dimeric columnar channel structure for the ester. Combining the present and previous structures reported for the relevant beta-CD derivatives, we further deduce that the pivot heteroatom, through which the aromatic substituent is tethered to beta-CD, plays a critical role in determining the helix structure, endowing the 2-fold and 4-fold axes to the N/O- and S/Se-pivoted beta-CD aggregates, respectively. This means that one can control the self-assembling orientation, alignment, and helicity in the solid state by finely tuning the pivot atom and the tether length. Further NMR and calorimetric studies on the self-assembling behavior in aqueous solution revealed that the dimerization step is the key to the formation of linear polymeric supramolecular architecture, which is driven by favorable entropic contributions.
Liu
Yu
Y
Department of Chemistry, State Key Laboratory of Elemento-Organtic Chemistry, Nankai University, Tianjin 300071, PR China. yuliu@public.tpt.tj.cn
Fan
Zhi
Z
Zhang
Heng-Yi
HY
Yang
Ying-Wei
YW
Ding
Fei
F
Liu
Shuang-Xi
SX
Wu
Xue
X
Wada
Takehiko
T
Inoue
Yoshihisa
Y
D001555:Benzene Derivatives / Q000138:chemical synthesis*; D003460:Crystallization; D018360:Crystallography, X-Ray; D003505:Cyclodextrins / Q000138:chemical synthesis*; D019281:Dimerization; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D016252:Microscopy, Scanning Tunneling / Q000379:methods; D008958:Models, Molecular; D012996:Solutions / Q000737:chemistry; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D047392:beta-Cyclodextrins
D001555:Benzene Derivatives; D003505:Cyclodextrins; D012996:Solutions; D047392:beta-Cyclodextrins; D014867:Water; C031215:betadex