title: Cross-linked supramolecular polymer gels constructed from discrete multi-pillar[5]arene metallacycles and their multiple stimuli-responsive behavior.
abstract: A new family of discrete hexakis-pillar[5]arene metallacycles with different sizes have been successfully prepared via coordination-driven self-assembly, which presented very few successful examples of preparation of discrete multiple pillar[n]arene derivatives. These newly designed hexakis-pillar[5]arene metallacycles were well characterized with one-dimensional (1-D) multinuclear NMR ((1)H and (31) P NMR), two-dimensional (2-D) (1)H-(1)H COSY and NOESY, ESI-TOF-MS, elemental analysis, and PM6 semiempirical molecular orbital methods. Furthermore, the host-guest complexation of such hexakis-pillar[5]arene hosts with a series of different neutral ditopic guests G1-6 were well investigated. Through host-guest interactions of hexakis-pillar[5]arene metallacycles H2 or H3 with the neutral dinitrile guest G5, the cross-linked supramolecular polymers H2⊃(G5)3 or H3⊃(G5)3 were successfully constructed at the high-concentration region, respectively. Interestingly, these cross-linked supramolecular polymers transformed into the stable supramolecular gels upon increasing the concentrations to a relatively high level. More importantly, by taking advantage of the dynamic nature of metal-ligand bonds and host-guest interactions, the reversible multiple stimuli-responsive gel-sol phase transitions of such polymer gels were successfully realized under different stimuli, such as temperature, halide, and competitive guest, etc. The mechanism of such multiple stimuli-responsive processes was well illustrated by in situ multinuclear NMR investigation. This research not only provides a highly efficient approach to the preparation of discrete multiple pillar[n]arene derivatives but also presents a new family of multiple stimuli-responsive "smart" soft matters.
authors.affiliation: Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University , Shanghai 200062, P.R. China.
authors.forename: Zhong-Yu
authors.initials: ZY
authors.lastname: Li
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Chang-Wei
authors.initials: CW
authors.lastname: Zhang
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Chen
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Hongwei
authors.initials: H
authors.lastname: Tan
authors.forename: Yihua
authors.initials: Y
authors.lastname: Yu
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Li
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Yang
mesh_terms: D047250:Calixarenes; D003432:Cross-Linking Reagents / Q000138:chemical synthesis / Q000737:chemistry*; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry; D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D005782:Gels; D046911:Macromolecular Substances; D009944:Organoplatinum Compounds; D011108:Polymers; D000644:Quaternary Ammonium Compounds; C570642:pillar(5)arene; D047250:Calixarenes