Molecular recognition of hydrocarbon guests by a supramolecular capsule formed by the 4:4 self-assembly of tris(Zn(2+)-cyclen) and trithiocyanurate in aqueous solution.
We have previously reported that the trimeric Zn(2+)-cyclen complex (tris(Zn(2+)-cyclen), [Zn(3)L(1)](6+)) and the trianion of trithiocyanuric acid (TCA(3-)) assembled in a 4:4 ratio to form a cuboctahedral supramolecular cage, [(Zn(3)L(1))(4)(TCA(3-))(4)](12+) (hereafter referred to as a Zn-cage), in neutral aqueous solution (cyclen=1,4,7,10-tetraazacyclododecane). Herein, we examined the molecular recognition of C(1)-C(12) hydrocarbons (C(n)H((2n+2)) (n≈1-12)), cyclopentane, cyclododecane, cis-decalin, and trans-decalin by the Zn-cage under normal atmospheric pressure. This cage complex was also able to encapsulate guest molecules that had larger volumes than that of the inner cavity of the Zn-cage, thereby suggesting that the inner shape of the Zn-cage was flexible. Computational simulations of Zn-cage-guest complexes provided support for this conclusion. Moreover, the solvent-accessible surface areas (SASA) of the Zn-cage host, guest molecules, and the Zn-cage-guest complexes were calculated and the data were used to explain the order of stability determined by the guest-replacement experiments. The storage of volatile molecules in aqueous solution by the Zn-cage is also discussed.
Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan. shinaoki@rs.noda.tus.ac.jp
Shin
S
Aoki
Satoshi
S
Suzuki
Masanori
M
Kitamura
Takeharu
T
Haino
Motoo
M
Shiro
Mohd
M
Zulkefeli
Eiichi
E
Kimura
D000473:Alkanes / Q000737:chemistry*; D002214:Capsules; D002849:Chromatography, Gas; D003198:Computer Simulation; D000080027:Cyclams; D003517:Cyclopentanes / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009281:Naphthalenes / Q000737:chemistry*; D014227:Triazines / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
D000473:Alkanes; D002214:Capsules; D000080027:Cyclams; D003517:Cyclopentanes; D006571:Heterocyclic Compounds; D009281:Naphthalenes; D014227:Triazines; D014867:Water; C039408:trithiocyanuric acid; C007229:decalin; C038072:cyclen; D015032:Zinc; C012867:decane