Synthesis, Crystal Structure, and Optical Properties of a Polyoxometalate-Based Inorganic−Organic Hybrid Solid, (n-Bu4N)2[Mo6O17(≡NAr)2] (Ar = o-CH3OC6H4)

A novel organic−inorganic hybrid solid, (n-Bu4N)2[Mo6O17(NAr)2] (Ar = o-CH3OC6H4) 1, has been prepared by refluxing of (n-Bu4N)2[Mo6O19] and appropriate o-anisidine in acetonitrile with N - N ‘-dicyclohexylcarbodiimide (DCC) as the dehydrating agent. Compound 1 has been characterized by single-crystal X-ray diffraction. Both of the two terminal o-anisidido ligands are linked, respectively, to an Mo atom of the hexamolybdate in a terminal fashion and exhibit an almost linear coordination mode of the Mo⋮N triple bond character. The two o-anisidido aryl rings on the hexamolybdate cluster lie in the cis position, allowing π−π stacking of phenyl ring among the anions. In the crystal, the cluster anions of 1 aggregate into an interesting 1D double chain along the a-axis through π−π stacking and C−H···O hydrogen-bonding interactions. Compared to the hexamolybdate parent, this solid has a smaller optical band gap of 2.25 eV from UV−visible-near-IR reflectance spectroscopy studies. It has also been characterized by 1H NMR, IR, and UV/Vis spectroscopic techniques.