Anion Binding of Inorganic Phosphates by the Hexaaza Macrocyclic Ligand 3,6,9,17,20,23-Hexaazatricyclo[23.3.1.1^11,15]triaconta-1(29),11(30),12,14,25,27-hexaene

Abstract

The interaction of mono-, di-, and tripolyphosphate anions with the various protonated forms of the hexaaza macrocyclic ligand BMXD,3,6,9,17,20,15 ]triaconta-1(29),11(30),12,14,25,27-hexaene, was investigated by potentiometric equilibrium studies. The protonated ligand forms a number of stable binary complexes in solution with each of the anionic substrates and the strength of interaction increases in the order mono-< di-< tripolyphosphate. Formation constants for all the species found are reported and compared with those of analogous systems. The hexahydrobromide salt of BMXD, (H 6 BMXD)Br 6 ‚7H 2 O crystallizes in the orthorhombic system, space group Pna2 1 , with a ) 11.597(4) Å, b ) 12.604(4) Å, c ) 27.361(7) Å, and Z ) 4. The binary complex (H 4 BMXD-H 2 P 2 O 7 )Br 2 ‚5.2H 2 O crystallizes in the monoclinic system, space group C2/c, with a ) 28.194(6) Å, b ) 13.875(3) Å, c ) 20.811(4) Å, β ) 113.72(3)°, and Z ) 8. The X-ray structure results reveal the nature of the interaction between the protonated macrocycle and anionic substrates to be that of multiple hydrogen bonding.

Anion binding with some 22- and 28-membered selenaaza macrocycles: Structural aspects and 77Se NMR studies

“…. .Br À distances $3.285(3) Å are well within the sum of the van der Waals radii 3.45 Å and are comparable to those found in similar macrocycle bromide derivatives [18].…”

Artificial Receptors for the Recognition of Phosphorylated Molecules

“…Macrocycle 66 , in which the furan rings are replaced with phenyl rings, is characterized by a basicity that falls between that of 18 and 65 ; it was found to bind inorganic phosphate similarly to 18 . 180 The bis-phenyl macrocycle 66 was observed to bind pyrophosphate more strongly than did the bis-furan macrocycle 65 , with triphosphate being complexed even more effectively. Single crystal X-ray diffraction analysis of the 66 :pyrophosphate complex revealed a twisted chair-type shape with the anion completely enclosed within the cavity.…”

Protonated Macrobicyclic Hosts Containing Pyridine Head Units for Anion Recognition

“…[18,27] Furthermore, the two secondary amine groups may act as additional hydrogenbond donors, as previously observed for different polyaza macrocyclic receptors. [28] These NH groups can be hardly protonated owing to delocalisation of the amine lone pair into the aryl ring. Indeed, electrostatic interactions between a negatively charged anion and a positively charged ligand can influence and enhance binding.…”