Synthesis, Crystal Structures and Lithium Encapsulation by Some Phenolic Aza Cages

Synthesis, characterization and X-ray crystal structures of cyclam derivatives. Part VI. Proton binding studies of a pyridine-strapped 5,12-dioxocyclam based macrobicycle

“…22 Shorter analogs (i.e., k, l, m = 4) were later shown to behave as ''proton sponges''. [23][24][25][26][27] Reinforced 28,29 and cross-bridged 17,[30][31][32] cyclic tetraamines such as 1,4,7,10-tetraazacyclododecane (cyclen) and 1,4,8,11tetraazacyclotetradecane (cyclam), are among the most common and readily accessible polynitrogenated bicyclic architectures. 33 They are obtained by linking either two adjacent or two nonadjacent secondary amines of the parent macrocycle.…”

Ligational Properties of Two New Phenolic Aza Cages towards Proton and Alkali Metal Ions − a Theoretical and an Experimental Approach

“…In other words, the phenolic group appears in its hydroxy form even in the neutral species. This behavior was also found for L, as already reported, [27] and can be explained by the different solvating power of the two media; the chargeϪcharge separation in water is successful, however, in methanol it is not. Nevertheless, it was possible to record the spectrum of the [HL1] ϩ species in methanol which shows a different absorption spectrum from the previous ones.…”

“…[27] The ligand is able to selectively encapsulate the lithium ion, a logK Ͼ3 is expected for the complexation process Li ϩ ϩ [H Ϫ1 L] Ϫ ϭ [LiH Ϫ1 L]. [27] At 300 K the molecule, both in the [H 2 L] 2ϩ [27] and the [H Ϫ1 L] Ϫ species, appeared rather rigid in the MD simulations performed in aqueous solution [the solvent was mimicked by using a distance-dependent dielectric constant ε(r) ϭ 80r, unpublished results]. In particular, the phenolic moiety does not change its orientation with respect to the [12]aneN 4 ring.…”

pH-Triggered Assembly of Organometallic Receptors for Lithium Ions

“…The Li + -specific ionophore, 12-crown-4, for example, displays a binding constant of log K = 4.25 in acetonitrile, whereas in water, no interaction with Li + could be detected at all (log K ≈ 0) . Among the few receptors which are able to bind Li + in water with high affinity, azamacrobicyclic cage molecules play a dominant role. , One of the highest stability constants was found for the cryptand (2,1,1) (log K = 5.5) 9g…”

“…This receptor also displays a good selectivity for Li + over Na + (200:1). For potential applications, however, azamacrobicyclic receptors show a severe disadvantage; the synthesis of these compounds generally requires several steps and proceeds with modest overall yields …”