Supramolecular approach to crystallization of polynuclear chromium(III)aqua hydroxo complexes:synthesis and crystal structures of complexes[Cr2(OH)2(H2O)8]~(4+)and[Cr4(OH)6(H2O)12]~(6+)with cucurbit[n]uril(n=7,8)

摘要

Supramolecular compounds of the compositions{[Cr2(OH)2(H2O)8](C42H42N28O14)2}-(NO3)4·18.75H2O(1)and{[Cr4(OH)6(H2O)12](C48H48N32O16)3}(NO3)6·55H2O(2)were synthesized from aqueous solutions of chromium(in)nitrate and the macrocyclic cavitand cucurbit[n]uril(C_(6n)H_(6n)N_(4H)O_(2n),where n=7 or 8,respectively).According to the X-ray diffraction study,the polynuclear chromium aqua complexes are disposed in cavities formed by the cucurbit[n]uril molecules and are linked to these molecules through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of the macrocycles.Compound 1 is the first example of supramolecular compounds of cucurbit[7]uril with metal aqua complexes.The isolation of the supramolecular adduct with cucurbit[8]uril 2 in the single-crystalline state allows the determination of the structure of the tetranuclear chromium aqua complex having an adamantane-like structure,[Cr4(mu 2-OH)6(H2O)12]~(6+),which has been previously unknown in the solid state.