Trinuclear π-conjugated chromophores formed by a neutral ferrocenyl group and a cationic mixed ruthenium sandwich linked through an unsymmetrical Schiff-base complex spacer

The synthesis of neutral dinuclear unsymmetrical Schiff base complexes I and 2 was carried out in an one-pot two-step reaction sequence that involves the reaction of 1-ferrocenyl-1,3-butanedione with an excess of ethylenediamine in refluxing CH2Cl2, to generate the intermediate half-unit Fc-C(O)CH2C(CH3)=NCH2CH2NH2, Fe = (eta(5)-Cp)Fe(eta(5)-C5H4), CP = C5H5), followed by its in situ templated reaction with salicylaldehyde and nickel(II) or copper(n) acetate in refluxing CH2Cl2-EtOH (3 : 1) mixture. On the other hand, ionic trinuclear unsymmetrical complexes > 3] (+) PF6- and [4](+) PF6_ were synthesized by reacting dinuclear precursors 1 and 2, respectively, with [(TI 5_Cp *)Ru(CH3CN)31+PF6-, CP* = C5Me5, in refluxing CH2Cl2. Both complexes contain the neutral electron-releasing ferrocenyl group and the cationic electron-withdrawal sandwich, [(eta(5)-Cp*)Ru(eta(6)-arene)](+), connected by a tetradentate {M(ONNO) chelate (M = Ni, Cu). The new unsymmetrical organometallic Schiff base compounds were characterized by elemental analysis, IR, UV-Vis, H-1 NMR and EPR spectroscopy. In addition, the Ni(n) containing complexes I and [3]+PF6- were authenticated by X-ray diffraction analysis. Solvatochromic and electrochemical properties were also studied. The organometallic-inorganic hybrid unsymmetrical Schiff base complexes [3]+PF6- and [4]+PF6- can be defined as type I non-rod-shaped dipolar chromophores.