A new acid–base indicator containing complex: Hydrothermal synthesis, crystal structure and properties of [Cd(en)2(H2O)2](MO)2

The first example of cadmium complex containing methyl orange [MO, (CH3)2NC6H4N = NC6H4SO3Na], formulated as [Cd(en)2(H2O)2](MO)2 1 (en = ethylenediamine) was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, IR, XRD, elemental analysis and Raman spectroscopic analysis. Compound 1 display a two-dimensional supramolecular layer structure with ladder-like supramolecular chain by X-ray crystallographic analysis. MO anion immobilized by H-bonds, as acid–base indicator, shows a similar behavior in comparison with its solution counterpart in terms of response to pH.