A cuboctahedral supramolecular capsule by 4 : 4 self-assembly of tris(Zn-II-cyclen) and trianionic trithiocyanurate in aqueous solution at neutral pH (cyclen=1,4,7,10-tetraazacyclododecane)

作者：Aoki S; Shiro M; Kimura E^*

来源：Chemistry - A European Journal, 2002, 8(4): 929-939.

DOI：10.1002/1521-3765(20020215)8:4<929::AID-CHEM929>3.0.CO;2-Q

• host-guest systems
• molecular recognition
• nanostructures
• supramolecular chemistry
• zinc

A 1:1 mixture of a tris(Zn-II-cyclen) (1: [Zn3L1], L-1= 1,3,5-tris-(1,4,7,10-tetraazacyclododecan-1-ylmeth- yl)benzene) and trithiocyanuric acid (TCA) yielded a 4:4 self-assembly complex [(Zn3L1)4-(TCA(3-))(4)] (6) through the formation of Zn-II-S- coordination bonds and hydrogen bonds between 1,3,5-triazine N and cyclen NH (cyclen = 1,4,7,10-tetraazacyclododecane); the supramolecular capsule structure was revealed by X-ray crystal structure analysis. The capsule exterior represents a twisted cuboctahedral framework containing a nanoscale truncated tetrahedral cavity. The crystal data: formula (C144HN72O58S12Zn12)-N-308 (6[NO3](12). 22H(2)O), Mr=5145.75, cubic, space group F432 (No. 209), a= 39.182(1) Angstrom, V= 60153(3) Angstrom(3), Z=8, R=0.100, R-w= 0.259. Lipophilic organic molecules with the matching sizes, for example, ([D-4]2,2,3,3)-3-(trimethylsilyl)propionic acid (TSP), 1-adamantanecarboxylic acid, 2,4-dinitrophenol (2,4-DNP), adamantane (ADM), or the tetra-n-propylammonium (TPA) cation, are encapsulated in the inner cavity, as revealed by remarkable upfield shifts of the H-1 NMR, signals of these guest molecules. The encapsulation of ADM was confirmed by X-ray crystal structure analysis. Crystal data of the ADM-encapsulating complex: formula C154H334N72O63S12Zn12 (6-ADM[NO3](12). 27H(2)O), M-r=5372.06, cubic, space group F432 (No. 209), a = 39.061 (1) Angstrom, V= 59599(3) Angstrom(3), Z = 8, R = 0.103, R-w = 0.263. The 4:4 self-assembly was stabilized by incorporation of one of these guest molecules. The apparent 4:4 self-assembly constants for 6 in the presence of an excess amount of a guest TPA, logK(app)(K-app=[6-TPA]/[1](4)[TCA](4)) (m(-7))), were determined to be 34.0 +/- 2.0 and 35.5 +/- 3.0 by potentiometric pH and UV spectrophotometric titrations, respectively. An apparent encapsulation constant for 2,4-DNP, log K-enc (K-enc = [6-2,4-DNP]/[6][2,4-DNP] (m(-1))), was 6.0 +/- 0.1 at pH 7.0 (50m(M) HEPES with I=0.1 (NaNO3)), as determined by UV titrations. The lipophilicity of the inner cavity was close to that of 2-propanol, as a quantum yield (Phi) of 0.24 +/- 0.1 for the fluorescent emission of 7-diethylaminocoumarin-1-carboxylic acid (20 mum) in the capsule was close to the Phi of 0.22 found for 2-propanol. Encapsulation properties of the present Zn-II-containing cage have been compared with those of cyclodextrins and Fujita's Pd-II-containing supramolecular cage. The exterior chirality of the 4:4 complex was controlled from within by an encapsulated chiral guest molecule, 2,10-camphorsultam, as indicated by Cotton effects in the circular dichroism spectra.

• 出版日期2002-2-15