Alkali-metal cation recognition induced isomerization of spirobenzopyrans and spironaphthoxazins possessing a crown ring as a recognition site: multifunctional artificial receptors
摘要:
Spirobenzopyrans and spironaphthoxazins possessing a monoaza-crown ring were synthesized. Isomerization of these compounds to the open colored merocyanines was induced by recognition of alkali-metal cations and the selectivity of the coloration was found to be governed by several factors: (1) the size of the crown ring, (2) the position of recognition, (3) electric properties of both the complexed cations and the merocyanine dipoles, and (4) the length of the alkyl chains connecting the spirobenzopyran units and the crown units. The spirobenzopyrans represent rationally designed multifunctional artificial receptors for alkali-metal cations.
reduction potential (modulationeffect) and to larger current responses (promotion effect). The magnitude of the modulation effects is determined by the binding affinity of the metal ions in the crown ether ligands, and by the distance between bound metal ions and the redox active cluster core. Variation of the linker between the cluster core and the metal ion bindingsite resulted in cluster compounds with
合成并表征了一系列 Fe4S4 簇化合物 I、III 和 V,其中立方簇核附加有四个冠醚硫醇盐配体,而 II 和 IV 带有没有冠醚部分的硫醇盐配体。这些化合物的光谱和电化学性质由硫醇盐配体的电子性质决定。仅在 III 的情况下,使用非常短的 α-硫代乙酰基接头将冠醚配体连接到簇核心,观察到配体的构象自由度受到限制。对碱金属和碱土金属离子(Li+、Na+、K+、Mg2+ 和 Ba2+)对簇化合物可逆 2-/3- 还原的影响进行了详细的电化学研究。在冠醚附加簇 I、III 和 V 的情况下,添加这些金属离子会导致阳极位移,即还原电位(调制效应)的正方向和更大的电流响应(促进效应)。调制效应的大小取决于冠醚配体中金属离子的结合亲和力,以及结合金属离子与氧化还原活性簇核之间的距离。簇核心和金属离子结合位点之间的接头的变化导致簇化合物对例如I和III的K+和Ba2+具有几乎相反的选择性。对于发现的化合物
A Simple, Regioselective Synthesis of 1,4-Bis(<i>tert</i>-butoxycarbonylmethyl)- tetraazacyclododecane
作者:Cong Li、Wing-Tak Wong
DOI:10.1021/jo026436+
日期:2003.4.1
A convenient synthetic route to 1,4-bis(tert-butoxycarbonylmethyl)tetraazacyclododecane (cyclen) (1) with high yield and excellent regioselectivity is described. Compound 1 reacted with a range of functionalized alkyl halides under two reaction conditions to give mono-N-alkylated 1,4-bis(tert-butoxycarbonylmethyl)tetraazacyclododecane (2-9) in good yield.
Solution studies of trimetallic lanthanide luminescent anion sensors: towards ratiometric sensing using an internal reference channel
作者:Sally E. Plush、Thorfinnur Gunnlaugsson
DOI:10.1039/b805610b
日期:——
Luminescenteuropium and terbium complexes and a mixed Eu(III)–Tb(III) complex were prepared, each with three macrocycles coordinating to a single lanthanide ion to form a trimetallic system, and can be used for the ratiometric sensing of anions in the case of the mixed complex.
We report herein the preliminary results obtained for spiropyrans 4 bearing a monoaza-crown ring (1) as a recognition site, of which isomerization to the colored merocyanines (2) is induced by recognition of alkali-metal cations. This new type of chromoionophore is conceptually different from the crown ether dyes so far synthesized, because in the latter cases, the absorption bands of chromophores