N-Salicylidene anil anions as thermo-sensitive components of organic–inorganic hybrid materials

New N-salicylidene meta and para aminobenzenesulfonate anions (1 and 2) presenting both reversible thermochromic properties and high thermal stability have been synthesized. These functional organic components have been successfully inserted into inorganic cationic [CuII(phen)3] and [NiII(phen)3] frameworks, as a proof of concept, affording [Cu(phen)3](1)2 (C1), [Ni(phen)3](1)2 (C2), [Cu(phen)3](2)Cl·5H2O·2CH3CH2OH (C3) and [Ni(phen)3](2)Cl·7H2O·CH3OH (C4), that have all been structurally characterized by single crystal X-ray diffraction. Temperature dependent fluorimetry demonstrates, for the first time, that keto-enol tautomerization of the anion is effective in the organic–inorganic hybrid materials, even though no thermochromism is observed. This insertion method paves the way towards the synthesis of a panel of hybrid multifunctional materials.