The authors introduce the notion of crown-like orders and introduce powerful tools for counting the endomorphisms of orders of this type. r r r r r r r r @ @ @ @ @ @ 1 3 5 7 2 4 6 8 r r r r r r r r @ @ @ @ @ @ 3 3 3 3 3 3 3 1 3 5 7 2 4 6 8 Figure 1: The fence and crown of order 4 r r r r r r r r r r r r · · · · · · @ @ @ @ @ @ @ @ @ @ −5 −3 −1 1 3 5 −4 −2 0 2 4 6 Figure 2: The infinite fence F

The synthesis and NOE-based structural characterization is described of thiacalix[4]arene tricarboxylic acid (7), thiacalix[4]crown-5 and -6 monocarboxylic acids (2 and 5), and the bis(N-methylsulfonyl)thiacalix[4]crowns-5 and -6 (4a,b). The 226Ra2+ selectivity coefficients, log(K(Ra)ex/K(M)ex), of the new thiacalix[4]arene derivatives are compared directly with those of thiacalix[4]crown-5 and...

By preparation and characterization of a series of pesudorotaxanes based on DB24C8 and paraquat derivatives, it was found that these complexes were stabilized by N⋅⋅⋅O interactions, C-H⋅⋅⋅O hydrogen bonding, and face-to-face π-stacking interactions. Because methyl protons of paraquat are involved in hydrogen bonding to the host, the substitution of any methyl hydrogen on paraquat causes apparen...

The two new ozonide compounds K([12]crown-4)2O3 · 1.5 NH3 (1) and Rb([12]crown-4)2O3 · 1.5 NH3 (2) were synthesized from the binary alkali metal ozonides and [12]crown-4 in liquid ammonia. The airand temperature-sensitive red, needle-shaped compounds crystallize isostructurally in the non-centrosymmetric space group Fdd2 (no. 43) with 16 formula units per unit cell. The lattice parameters are a...

Dibenzo-2 1-crown-7 (DB2IC7) and dibenzo-24-crown-8 (DB24C8) have been used to extract the metal ions (Na+. K+. Mg2+ and Ca2+) present in bittern, schoenite and in an artificial solution containing equimolar amount of the above mentioned metal ions. Ion chromatographic study of the organic extract shows that DB21 C7 extracts potassium with hi gh selectivity, whereas DB24C8 extracts comparable a...

The asymmetric unit of the title compound, [Co(C(44)H(28)N(4))]·C(12)H(24)O(6), contains one half of a Co(II)(TPP) (TPP is tetra-phenyl-porphyrin) complex and one half of an 18-crown-6 mol-ecule of crystallization, both lying on inversion centers. The Co(II)(TPP) complex exhibits a nearly planar conformation of the porphyrinate core [maximum deviation = 0.069 (2) Å] with an average Co-N distanc...

The title compound, C(2)H(2)·C(12)H(24)O(6)·2NH(3), was formed by co-crystallization of 18-crown-6 and acetyl-ene in liquid ammonia. The 18-crown-6 mol-ecule has threefold rotoinversion symmetry. The acteylene mol-ecule lies on the threefold axis and the whole mol-ecule is generated by an inversion center. The two ammonia mol-ecules are also located on the threefold axis and are related by inve...