New supramolecular hosts: Synthesis and cation binding studies of novel Tröger's base-crown ether composites
作者:Alla Manjula、Madhavarao Nagarajan
DOI:10.1016/s0040-4020(97)00759-x
日期:1997.8
A simple and straightforward synthesis of a novel class of supramolecular hosts containing the Tröger's base moiety is reported. The cationbinding properties of these macrocycles were investigated using Cram's picrate extraction method.
The host–guest complexation behavior of cyclic oligosaccharides, permethylated cycloinulohexaose 1, permethylated cycloinuloheptaose 2, and permethylated cycloinulooctaose 3 with metal cations has been characterized by means of UV-visible, NMR, and electrospray ionization (ESI) mass spectrometry. In the crystal state, the structures of 1·K+, 1·Rb+, and 1·Cs+ were same as that of the 1·Ba2+ complex which has a u-u-d-u-u-d (u = up, d = down) furanose ring arrangement for the plane of the crown ring moiety. The association
constants (KS) in THF and in [2H6]acetone at 298 K were evaluated. The binding ability of host 1 with metal cations was of the same degree as that of calix[6]arene derivative 4 and much higher than those of hosts 2 and 3. The thermodynamic parameters of the complexation of host 1 with metal cation in THF were determined, and it was suggested that the entropy change for the solvation of the metal cations was one of the important factors in the complexation equilibrium. It was clarified that the structure of the host 1·K+ complex in solution at low temperature (furanose ring arrangement: u-d-u-d-u-d) was different from that in the crystal state (u-u-d-u-u-d arrangement)
by the coalescence behavior in 1H-NMR. The relative peak intensity of the complex ions of host 1 or 2 with two alkali metal ions in ESI mass spectrometry (in acetone) showed a correlation in the first order approximation with the ratio of the corresponding complex ion concentrations estimated from the KS values.
balls (MBs), enabling transmembrane ion transport selectivity to be custom designable. The modularly tunable MBm-Cn (m = 4-7; n = 6-12) structures consist of a C60-fullerene core, flexible alkyl linkers Cn (i.e., C6 for n-C6H12 group), and peripherally aligned benzo-3m-crown-m ethers (i.e., m = 4 for benzo-12-crown-4) as ion-transporting units. Screening a matrix of 16 such MBs, combinatorially derived
Controlled self-assembly of bis(crown)stilbenes into unusual bis-sandwich complexes: structure and stereoselective [2+2] photocycloaddition
作者:Sergey P. Gromov、Artem I. Vedernikov、Natalia A. Lobova、Lyudmila G. Kuz'mina、Stepan S. Basok、Yuri A. Strelenko、Michael V. Alfimov、Judith A. K. Howard
DOI:10.1039/c0nj00780c
日期:——
shown by 1H NMR spectroscopy that symmetrical bis(crown)stilbenes (L) and small alkali and alkaline-earth metal cations form 1(L) ∶ 1(Mm+) and 1(L) ∶ 2(Mm+) complexes in MeCN solutions. In the case of large or hydrated metal cations such as Cs+, Rb+, K+, Ba2+, Sr2+, [Ca(H2O)x]2+ and stilbenes with a small crown-ether cavity as compared with the metal cation size, stable bis-sandwich complexes 2(L) ∶ 2(Mm+)
它是由示出1 H NMR光谱的是对称的双(冠)芪(L)和小碱金属和碱土金属阳离子形成1(L):1(M米+)和1(L):2(M米+)MeCN解决方案中的复合物。在较大或水合金属阳离子(例如Cs +,Rb +,K +,Ba 2 +,Sr 2 +,[Ca(H 2 O)x ] 2+)和丁苯醚中,冠醚空穴较小的情况下与金属阳离子的大小,稳定的双夹心络合物2(L):2(M m +)也可以形成。由双(18-冠-6)二苯乙烯与丙烷二铵离子也可制得稳定的双假夹心2:2络合物。阐明了冠醚大小,阳离子大小和性质对二苯乙烯光转化途径和产物组成的影响。双(假)三明治复合物经过有效的立体选择性[2 + 2]光环加成,主要生成新的1,2,3,4-四冠环丁烷的rctt异构体。通过X射线衍射证实了双(皇冠)对苯二甲酸酯和所获得的环丁烷的配合物的结构。