Azonia spiro polyaza macrocycles containing biphenyl subunits as anion and cation receptors

A computational study on 3-azonia-, 3-phosphonia-, and 3-arsoniaspiro[2.2]pentanes and related three-membered heterocycles

A theoretical study at the ab initio MP2/6-311++G(d,p) level of theory is carried out to characterize several heterocyclic spiro[2.2]pentane cations with N, P, and As as spiro atoms. The strain and relative stability of the spiropentanes are obtained through isodesmic reactions. Nucleus-independent chemical shifts (NICS) and 3D NICS isosurfaces show σ-aromatic characteristics, similar to those found in cyclopropane. The interaction with the Cl(-) anion, which results in four different stationary structures, is studied and characterized by means of the atoms in molecules methodology, and Cl⋅⋅⋅pnicogen, Cl⋅⋅⋅H, and Cl⋅⋅⋅C interactions are found. The most stable structure in all cases corresponds to opening of one of the three-membered rings, due to the attack of the Cl atom, and C-Cl bond formation. Furthermore, the reaction with the 3-boranuidaspiro[2.2]pentane anion results in the formation of a new compound through cleavage of one ring of both reactants.

Fluorescent acridine-based receptors for H2PO4(-)

Two new pseudopeptidic molecules (one macrocyclic and one open chain) containing an acridine unit have been prepared. The fluorescence response of these receptors to a series of acids was measured in CHCl(3). Receptors are selective to H(2)PO(4)(-) versus HSO(4)(-), and an even higher selectivity is found over other anions such as Cl(-), Br(-), CH(3)COO(-), and CF(3)COO(-). We show that the macrocyclic receptor is more selective for H(2)PO(4)(-) than the related open chain receptor. The supramolecular interactions of triprotonated receptors with different anions have been modeled in silico and have been studied by different experimental techniques. Optimized geometries obtained by computational calculations agree well with experimental data, in particular fluorescence experiments, suggesting that the selective supramolecular interaction takes places through coordination of the anions to the triprotonated form of the receptor.