Effect of water/carboxymethylcellulose gel on the excimer formation of polyamine ligands functionalized with naphthalene.

Formation of intramolecular excimers was studied for the compounds 6,20-bis-naphthalene-2-ylmethyl-3,6,9,17,20,23,29,30-octaaza-tricyclo[23.3.1.1] triaconta-1(29),11,13,15(30),25,27-hexane (L1), a bis-naphthalene derivative, and N1-(2-{bis-[2-(3-amino-propylamino)-ethyl]-amino}-ethyl)-propane-1,3-diamine (L2), a tris-naphthalene derivative, incorporated in gels of carboxymethylcellulose sodium salt. Excimers are formed through dynamic processes as well as from ground state dimers. A mathematical treatment including preformed dimers was used to split the static and dynamic contributions in the excimer/monomer emission ratio. In the case of compound L1, the activation energy for excimer formation in water is 11 kJ mol(-1) and experimental evidence that the dynamic terms are identical in water and in the gel was achieved. On the other hand, ground state dimers are extremely favorable in the gel with an equilibrium constant of 8.2 at 25 degrees C. On the contrary, in the case of compound L2, the ground state dimers are observed in water but not in the gel. The results were interpreted as reflecting a balance between specific interactions (hydrogen bond) and confinement effects.

Specific supramolecular interactions between Zn(2+)-salophen complexes and biologically relevant anions.

Recognition of inorganic phosphates PO(4)(3-), P(2)O(7)(4-), and P(3)O(10)(5-) and nucleotides AMP(2-), ADP(3-), and ATP(4-) by Zn(2+)-salophen complexes 1 and 2 in ethanol was investigated by different spectroscopic techniques. (31)P NMR and mass spectrometry showed that anions of both series are bound by 1 and 2, while absorption and emission studies revealed that only nucleotides produce relevant changes in the spectral properties of the two hosts. (1)H NMR studies proved that the adenine aromatic group is involved in the complexation, thus pointing out the role of supramolecular ditopic receptors played by salophen derivatives toward this class of biologically relevant substrates. The lifetime of the photogenerated triplet state of the Zn(2+)-salophen compounds was measured by nanosecond laser flash photolysis, and the observed changes upon increasing the concentration of nucleotides allowed the identification of the formation of a 1:0.5 host/guest intermediate complex additionally to the formation of a 1:1 complex.