Unexpected Polymorphism in Bromoantimonate(III) Complexes and Its Effect on Optical Properties

Reactions of [SbBr6](3-) containing HBr solutions with bromide salts of 1,1'-(1,2-ethanediyObis(pyridine) (PyC22+) or 1,1 '-( 1,2-ethanediy1)bis(3,5-dimethylpyridine) (3,5-MePyC22+) initially result in the formation of the deep orange complexes Cat[SbBr5] (1 and 2), featuring unusual Sb center dot center dot center dot Br interactions in the solid state. In the mother liquor, 1 transforms into discrete binuclear (C2Py)(2)[Sb2Br10], which demonstrates polymorphism (triclinic 3 and monoclinic 4), while 2 transforms into polymeric (3,5-MePy){[SbBr4]} (5). DFT calculations reveal that the system of noncovalent Sb center dot center dot center dot Br contacts may be responsible for the appearance of the observed optical properties (unusual deep orange coloring).

Automated summary

The reactions of [SbBr6](3-) with HBr solutions and bromide salts of PyC22+ or 3,5-MePyC22+ form deep orange complexes with unusual Sb center dot center dot Br interactions. Further investigation reveals polymorphism in the crystal structures of these compounds and DFT calculations suggest a correlation between noncovalent Sb center dot center dot Br contacts and optical properties.