Solvatochromism is the property of a compound that causes it to change color in the presence of solvents with varying polarity. This phenomenon is most strikingly evidenced by a compound’s variable appearances in solvents of different polarities. Previous success in synthesizing the solvatochromic complex, [Mo(bpy)Cl4]- (bpy= 2,2’-bipyridine), which shifts over 100 nm in various solvents, lead to interest in the related compounds [Mo(bpy)Br4]-, [Mo(bpy)(SCN)4]-, [W(bpy)Cl4]-, and [W(bpy)Br4]-. Despite their structural similarities, syntheses of these compounds were highly varied. The bromide complexes were synthesized starting from the metal hexacarbonyl complex and elemental bromine while the tungsten chloride complex was synthesized using a mixture of tungsten hexacarbonyl and tungsten hexachloride. Preliminary results suggest that [Mo(bpy)Br4]- exhibits solvatochromism similar to it chloride precursor, but the analogous tungsten complexes appeared less so and suffered from rapid decomposition. Electrochemically, they showed reversible couples comparable to the [Mo(bpy)Cl4]- but shifted due the difference in ligands. However, the thiocyanate complex has not been observed to be solvatochromic.

Substituent effects on solvatochromism of group six metals

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