Diverse structures and adsorption properties of quasi-Werner-type copper(II) complexes with flexible and polar axial bonds

• Published in: Dalton transactions : an international journal of inorganic chemistry 2011-03, Vol.40 (10), p.2268-2274
• Main Authors: Noro, Shin-ichiro, Ohba, Tomonori, Fukuhara, Katsuo, Takahashi, Yukiko, Akutagawa, Tomoyuki, Nakamura, Takayoshi
• Format: Article
• Language: English
• Subjects: Adsorption; Benzene; Carbon dioxide; Copper; Crystal structure; Flexibility; Ligands; Transformations
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c0dt01129k

The quasi-Werner-type copper(II) complex, [Cu(PF(6))(2)(4-mepy)(4)] (1), in which 4-mepy is the 4-methylpyridine ligand, has flexible and polar axial bonds of Cu-PF(6). Flexibility of the Cu-PF(6) bonds induces diverse and unprecedented guest-inclusion structures, such as {[Cu(PF(6))(2)(4-mepy)(4)][Cu(PF(6))(4-mepy)(4)(acetone)]·PF(6)·4acetone} (γ-1⊃2.5acetone), {[Cu(PF(6))(2)(4-mepy)(4)][Cu(PF(6))(4-mepy)(4)(2-butanone)]·PF(6)·3.5(2-butanone)} (γ-1⊃2.25(2-butanone)), {[Cu(PF(6))(2)(4-mepy)(4)][Cu(PF(6))(4-mepy)(4)(H(2)O)]·PF(6)·4benzene} (γ-1⊃0.5H(2)O·2benzene), and {[Cu(PF(6))(2)(4-mepy)(4)]·2benzene} (γ-1⊃2benzene). Exposure of the dense form, α-1, to benzene vapor affords the benzene-inclusion complex {[Cu(PF(6))(2)(4-mepy)(4)]·2benzene} (γ-1⊃2benzene), all benzene guests of which are easily removed by vacuum drying, reforming guest-free, dense α-1' with smaller sized crystals than α-1. In contrast to α-1, which shows almost no CO(2) adsorption, α-1' adsorbs CO(2) gas with structural transformations, this being the first example that exhibits adsorption of gas in a dense Werner-type complex and a drastic change in adsorption properties depending on the size of the crystals.