The ferrocene-pyrene dyad 3 is able to selectively sense the pyrophosphate anion. The anion recognition was evaluated using electrochemistry, (1)H NMR, as well as fluorescence spectroscopy. The binding event can be inferred from either the redox-shift (DeltaE(1/2) = -100 mV) or the emission intensity ratio of the pyrene monomer to the excimer emission bands in both the neutral and oxidized forms of the receptor upon complexation.

The synthesis and electrochemical, optical, and cation-sensing properties of the ferrocene-triazole-pyridine triads 3 and 5 are presented. Azidoferrocene 1 and 1,1'-diazidoferrocene 4 underwent the "click" reaction with 2-ethynylpyridine to give the triads 3 and 5 in 81% and 68% yield, respectively. Electrochemical studies carried out in CH(3)CN in the presence of increasing amounts of Zn(2+), Ni(2+), Cd(2+), Hg(2+), and Pb(2+) metal cations, showed that the wave corresponding to the ferrocene/ferrocenium redox couple is anodically shifted by 70-130 mV for triad 3 and 167-214 mV for triad 5. The maximum shift of the ferrocene oxidation wave was found for 5 in the presence of Zn(2+). In addition, the low-energy band of the absorption spectra of 3 and 5 are red-shifted (Δλ = 5-10 nm) upon complexation with these metal cations. The crystal structures of compounds 3 and 5 and the complex [3(2)·Zn](2+) have been determined by single-crystal X-ray methods. (1)H NMR studies as well as density functional theory calculations have been carried out to get information about the binding sites that are involved in the complexation process.

A generalization of the effective metric approach is proposed and applied both for the calculation of radial couplings and for the determination of diabatic states along a single coordinate using the formalism of variational effective Hamiltonian theory. The application to the ionic molecule NaRb+ shows that strictly diabatic states are obtained even for very short distances where a huge number of crossings are observed. Polarization and electronic delocalization effects are estimated. A comparison with various diabatization methods is performed. The proposed method brings a significant improvement with respect to the existing ones.

A number of monosubstituted (3, 4, 6, 8, 9, 11, and 13) and disubstituted (15 and 16) ferrocene-derived triazoles have been prepared, by using the copper-catalyzed click reaction, and fully characterized. The versatility of the click reaction enables the decoration of the ferrocene-triazole core, with additional substituents displaying different optoelectrochemical properties. The most salient features derived from the sensing studies are that receptors 3, 6, 15, and 16 undergo unprecedented cathodic shifts of the oxidation peak of the ferrocene/ferrocenium redox couple in the presence of F–, AcO–, H2PO4 –, and HP2O7 3– anions, whereas receptors 11 and 16 behave as dual redox and optically selective molecular sensors for Hg2+ cations. The isolated [6 3·Ni2+] complex has been characterized by X-ray analysis.

The preparation, electrochemical, electronic, and cation sensing properties of an indole-ferrocene-indole triad, are presented. A salient feature of this new structural motif is that the redox-active organometallic fragment is linked to the indole rings by unsaturated nitrogen functionalities. Triad behaves as a highly selective dual-redox and chromogenic chemosensor molecule for Hg(2+) cations: the oxidation redox peak is anodically shifted (DeltaE(1/2) = 210 mV), and the low energy band of the absorption spectrum is red-shifted (Deltalambda = 120 mm), upon complexation with this metal cation. This change in the absorption spectrum is accompanied by a dramatic colour change from orange to green which allows the potential for "naked eye" detection. (1)H NMR as well as DFT calculations have been carried out to get information about the molecular sites which are involved in bonding.