Organotin macrocyclic receptors

Tin-containing macrocycles 14-16 use the capacity of the metal atom acceptor to capture halide anions in the cavity, acting like inverse crown ethers [49-51]. Thus, 

Monocyclic Cl2Sn[(CH2) ]2SnCl2 (n = 8, 10, and 12) bind two Cl anions rapidly but are poorly selective and there is little dependence on ring size [56]. The anionbinding capacity of tricyclic organotin cryptands depends on the tin-tin distance in the host [57, 58]. 

Strong anion binding capacity (towards and Cl ) is also observed for non-cyclic methylene bridged, tri- and tetratin hosts, X(Ph2SnCH2) SnPh2X ( = 2 or 3, X = F and Cl) which form [X(Ph2SnCH2) SnPh2X](X ) i anionic complexes [59]. 

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A very unusual mixed-metal receptor has been prepared by Jurkschat and co-workers [68]. Macrocycle 102 comprises two ferrocene reporter units linked together by two Lewis acidic organotin spacers. Electrochemical measurements in dichloromethane solution show anion-induced cathodic shifts of the ferrocene/ferrocenium redox couple of 130 mV for chloride, 210 mV for fluoride and 480 mV for dihydrogenphosphate. 

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