Photoreactivity of the (2,2′-bipyridyl)hexacyanotungstate(IV) ion in aqueous solution

✍ Scribed by B. Sieklucka; J. Szklarzewicz; A. Samotus

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 263 KB
• Volume: 70
• Category: Article
• ISSN: 1010-6030
• DOI: 10.1016/1010-6030(93)80006-u

✦ Synopsis

The electronic spectrum of the (\mathrm{W}(\mathrm{bpy})(\mathrm{CN}){5}{ }^{2-}) ion (bpy, (2,2^{\prime})-bipyridyl) in the visible region is dominated by metal-to-ligand charge transfer (MLCT) transitions. The complex undergoes photosubstitution with the preferential loss of the bpy ligand. The wavelength-independent quantum yields (\Phi) increase from (3.1 \times 10^{-3}) (at (\mathrm{pH}) 1) to (7.2 \times 10^{-3}) (in the range (\mathrm{pH}) 8.12-10.85). The photoreaction occurs from a short-lived, low-lying ligand field (LF) state. The lower reactivity in acidic medium suggests that the formation of the intermediate (\mathrm{W}(\mathrm{CN}){6}(\mathrm{OH})_{2}{ }^{4-}) is more efficient than the formation of the aqua-substituted analogue. A scheme of photoreactions and thermal reactions based on the experimental observations is presented.