Spontaneous Assembly of 6<sup>3</sup> Topological Metal−Organic Nanotubes with Distinct Asymmetric Subunits for the Construction of Hydrophilic Intertube Channels Encapsulating Rare Helical Water-Chains

The hydrothermal reaction of cadmium nitrate hydrate (Cd(NO<sub>3</sub>)<sub>2</sub>·4H<sub>2</sub>O) with <i>p</i>-terphenyl-type 4,4′-(1,4-phenylene)bis(2,6-dimethyl-3,5-pyridinedicarboxylic acid) (H<sub>4</sub>L), and phenanthroline (phen) in the presence of triethylamine leads to a three-dimensional supramolecular aggregate {[Cd<sub>3</sub>(phen)<sub>3</sub>(HL)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]·4.25H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1</b>). In <b>1</b>, the T-type second building units construct independent one-dimensional (1-D) metal−organic nanotubes (MONTs) with 6<sup>3</sup> topology containing distinct axially asymmetric subunits [<i>R</i>-Cd<sub>3</sub>(HL) and <i>S</i>-Cd<sub>3</sub>(HL)]. The adjacent <i>RR</i>-Cd<sub>5</sub>(HL)<sub>2</sub> supersubunits form a hydrophilic intertube chiral channel (I), and the <i>SS</i>-Cd<sub>5</sub>(HL)<sub>2</sub> 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, <i>R</i>-Cd<sub>3</sub>(HL) → <i>RR</i>-Cd<sub>5</sub>(HL)<sub>2</sub> → chiral channel (I) → left-handed (<i>M</i>) water-helix, and <i>S</i>-Cd<sub>3</sub>(HL) → <i>SS</i>-Cd<sub>5</sub>(HL)<sub>2</sub> → chiral channel (II) → right-handed (<i>P</i>) water-helix. Photoluminescence and nitrogen adsorption behavior of <b>1</b> have been examined.