Structure of Ni(II) Inclusion Complex in Solid/Solution States and the Enhancement of Catalytic Behavior in Electrochemical Hydrogen Production.

In this article, we investigate the encapsulation of K[Ni(maleonitriledithiolate)] () within a host molecule, β-cyclodextrin (β-CD), via single-crystal X-ray analysis. An inclusion complex, K{[Ni(maleonitriledithiolate)]@(β-CD)} (), was constructed from and two β-CDs. The anion guest Ni complex included a host cavity, constructed using two β-CDs, and the Ni atom of the anion was located between the two hydrophilic primary rims. Ultraviolet-visible absorption spectroscopy revealed that inclusion complex exhibited a 2:1 (host:guest) stoichiometry in the solution, which is consistent with the result obtained from X-ray crystallography. The association of the host and guest occurred in two steps, and the association constants for the first and second steps were 1.1(7) × 10 and 1.8(5) × 10 mol dm, respectively. The catalytic behavior of and was investigated for electrochemical hydrogen production in the aqueous solution of an acetate buffer (pH = 4.72). During the catalytic reaction, inclusion complex was observed to have a better catalytic reaction rate than . The study findings provide insights into the effects of the encapsulation of guest molecules within host structures.