Two coordination polymers [Ag(bib)]NO 3 ‚H 2 O (1) and [Ag(bib)]ClO 4 (2) with one-dimensional (1D) chain structure were synthesized by reactions of ditopic ligand containing imidazole donors, namely, 1-bromo-3,5bis(imidazol-1-ylmethyl)benzene (bib), with corresponding silver salts. While the bib ligand reacted with ditopic diacetato-zinc(II) acceptors, M 2 L 2 -type metallocyclic ring-like complex [Zn 2 (bib) 2 (OAc) 4 ]‚2H 2 O (OAc ) acetate anion) (3) was obtained, which was further connected by Br‚‚‚Br interactions to lead to the formation of 1D pseudopolyrotaxane. When ligand bib reacted with Zn(NO 3 ) 2 ‚6H 2 O and Mn(NO 3 ) 2 , two complexes [Zn(bib) 2 (H 2 O) 2 ](NO 3 ) 2 ‚ 2H 2 O (4) and [Mn(bib) 2 (H 2 O) 2 ](NO 3 ) 2 ‚2H 2 O ( 5) with 2D network structure were obtained in which the metal atoms had octahedral coordination geometry. The structures of these coordination complexes were determined by X-ray crystallography, and the results revealed that the coordination geometry of metal atoms have a great impact on the structure of the supramolecular architectures. Furthermore, the nitrate anions located in the voids between the 2D cationic layers in 4 can be exchanged by nitrite anions, which means that complex 4 with 2D network structure has anion exchange properties.

The configurations of stereocenters of chiral alcohols are commonly assigned by making a pair of diastereomeric Mosher esters and analyzing their 1 H NMR spectra by the subtraction protocol of the "advanced Mosher method". 1 In contrast, making Mosher esters of achiral alcohols is pointless. Or is it?Consider the pairs of methylene protons on either side of the carbinol carbon in the three classes of secondary alcohols 1a-3a shown in Figure 1. Chiral alcohol 1a-bearing different substituents on either side of the carbinol-is the usual candidate for the advanced Mosher rule. The (R)-and (S)-Mosher esters 1e are made and the resonances in their 1 H NMR spectra are assigned. Subtraction of the corresponding chemical shifts according to the rule provides the configuration. Achiral alcohol 2a-having the same substituents on either side of the carbinol-has no stereocenter and its methylene resonances are equivalent by symmetry. 2 The equivalence is broken in the Mosher ester 2e, and the resonances can now be assigned by a "backwards" application of the Mosher rule. 3 The second Mosher ester derivative of 2a is the enantiomer of 2e, so it provides no new information (its methylene resonances simply reverse places).There is no pressing need to assign proton resonances of Mosher ester derivatives of achiral compounds. But the analysis applies directly to chiral compounds that have elements of nearsymmetry. Consider alcohol 3a, bearing different but very similar substituents on either side of the carbinol. Because the compound almost has a plane of symmetry, the pairs of methylene protons will be (accidentally) chemical shift equivalent in the alcohol 3a but different in the Mosher ester 3e. Now, in a "shortcut" of the usual advanced Mosher rule, subtraction of the pair of resonances from each other (rather than from the corresponding resonances in the diastereomeric Mosher ester) provides the absolute configuration of the alcohol. The diastereomeric Mosher ester can be made and the advanced Mosher rule can be applied as usual, but like the enantiomer of 2e, the diastereomer of 3e will provide no new information.We selected the natural product petrocortyne A 4 as a suitable test of the "shortcut" Mosher method (Figure 2). This is a typical representative of a group of related natural products whose members exhibit diverse biological activities. 4 In particular, the dialkynyl carbinol stereocenter at C14 of petrocortyne A has a near-plane of symmetry that extends for seven carbon atoms on either side before being broken. As a consequence of this local symmetry, the formally different protons H11 and H17 are accidentally equivalent, but this equivalence should be broken by making a Mosher ester.* curran@pitt.edu . Supporting Information Available:Contains summary schemes for synthesis of fragments 5, 9, and 14, and copies of NMR spectra of the petrocortyne isomers and derived Mosher esters. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public Access NIH-PA Author ManuscriptNIH-P...

No abstract