Crystal Structures and Photoluminescence of Two Inorganic–Organic Hybrids of Anderson Anions

Two supramolecular compounds (Hbipy)2[Cr(OH)6Mo6O18H](bipy) (1) and (Hbipy)3[Al(OH)6Mo6O18]·3H2O (2) were synthesized and their crystal structures were analyzed with x-ray diffraction technique. In 1 the Anderson anion with six hydroxyl groups forms six hydrogen bonds with bipy molecules, forming a supramolecular layer, the layers are linked by hydrogen bonds between anions. In 2 the Anderson anion with three hydroxyl groups and terminal/bridging oxygen atoms forms six hydrogen bonds with bipy molecules, and lattice water molecules and the anions form also hydrogen bonds, constructing a supramolecular architecture. The intensive emission in 650–740 nm of 1 is attributed to R-lines of Cr3+ and the high intensity may be caused by energy transfer of bipy molecules through hydrogen bonds. In contrast, 2 gives only the π* → π emission of bipy molecules at 460 nm.