Spontaneous Assembly of 63 Topological Metal−Organic Nanotubes with Distinct Asymmetric Subunits for the Construction of Hydrophilic Intertube Channels Encapsulating Rare Helical Water-Chains

Abstract

The hydrothermal reaction of cadmium nitrate hydrate (Cd(NO3)2·4H2O) with p-terphenyl-type 4,4′-(1,4-phenylene)bis(2,6-dimethyl-3,5-pyridinedicarboxylic acid) (H4L), and phenanthroline (phen) in the presence of triethylamine leads to a three-dimensional supramolecular aggregate {[Cd3(phen)3(HL)2(H2O)2]·4.25H2O}n (1). In 1, the T-type second building units construct independent one-dimensional (1-D) metal−organic nanotubes (MONTs) with 63 topology containing distinct axially asymmetric subunits [R-Cd3(HL) and S-Cd3(HL)]. The adjacent RR-Cd5(HL)2 supersubunits form a hydrophilic intertube chiral channel (I), and the SS-Cd5(HL)2 supersubunits generate another type of hydrophilic intertube chiral channel (II). These two types of chiral channels encapsulate two corresponding types of helical water-chains with three pseudo screw axes, exhibiting a novel chirality transformation and transfer, namely, R-Cd3(HL) → RR-Cd5(HL)2 → chiral channel (I) → left-handed (M) water-helix, and S-Cd3(HL) → SS-Cd5(HL)2 → chiral channel (II) → right-handed (P) water-helix. Photoluminescence and nitrogen adsorption behavior of 1 have been examined.