Cation and anion recognition characteristics of open-chain polyamines containing ethylenic and propylenic chains

Synthesis, Protonation and CuII Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

“…[18] Literature values [18,19] for the protonation constants of L 3 and L 4 are also included for comparison. The stability constants for the formation of Cu 2+ complexes with the L 1 and L 2 cyclophanes are included in Table 2 together with those previously reported for L 3 and L 4 .…”

“…The stability constants for the formation of Cu 2+ complexes with the L 1 and L 2 cyclophanes are included in Table 2 together with those previously reported for L 3 and L 4 . [18,19] All three cyclophanes allow for the formation of both mono-and dinuclear metal complexes whereas the open-chain L 4 ligand only forms mononuclear species. As usually occurs in these kinds of ligands, the nuclearity of the species formed is strongly dependent on the M/L molar ratio so that while for L 1 at a 1:1 ratio only mononuclear species are detected throughout the whole pH range studied, for a 2:1 ratio the dinuclear hydroxylated complex is the only species in solution above pH 6 ( Figure 2).…”

“…For a 2:1 molar ratio several dinuclear species can be detected which also dominate the species distribution curves above pH 6 ( Figure 3). [18,19] for the systems Cu 2+ -L 3 and Cu 2+ -L 4 are also included for comparative purposes. With regards to the actual values of the stability constants, the major observation made from the values in Table 2 is that the stability of the [CuL 2 ] 2+ species is significantly lower than that found for the same species with the other ligands suggesting a lower coordination number of the cyclophane in this case.…”

“…[20] and the H 3 CuL complex of 4,7,10,13-tetraazahexadecane-1,16-diamine shows its maximum at 590 nm (ε not given in the literature). [18] Both of these complexes contain a polyamine coordinated in a tridentate manner and coordination of an additional amine group leads to a shift of the maximum to shorter wavelengths by 15-60 nm relative to the 3  coordinated species: Cu(dien)(NH 3 ) 2+ has λ max = 576 nm (ε = 84  -1 cm -1 ), [20] for the CuL 2+ complex of 4,7,10,13-tetraazahexadecane-1,16-diamine λ max = 578 nm (ε = 178  -1 cm -1 ) [18] and for the HCuL 3+ and CuL 2+ species with 4,7,10-triazatridecane-1,13-diamine the values are λ max = 573 nm (ε = 187  -1 cm -1 ) and λ max = 585 nm (ε = 214  -1 cm -1 ), [20] respectively. Interestingly, increased molar absorptivities were also observed in the tetracoordinated species (ε = 170-200  -1 cm -1 ) with respect to the corresponding tricoordinated species (ε = 70-150  -1 cm -1 ), something which was attributed to distortion from an ideal square planar structure.…”

From Flexible to Constrained Tris(tetraamine) Ligands: Synthesis, Acid–Base Properties, and Structural Effect on the Coordination Process with Nucleotides

“…[2] In consequence, studies focusing on the recognition of nucleotides and especially ATP has increased over the last years. [3] Generally, the binding forces are mainly based on electrostatic interactions, and the association constants may possibly be enhanced by providing additional binding elements as hydrogen-bonding or π-stacking interactions. Among the various hosts presented in the literature, [4] polyamines and especially protonated polyamines are of special interest for anionic guest complexation.…”