Studies on the formation of anionic complexes in the presence of high concentrations of anions in aqueous solution

Abstract

The olution che istry of transition etal ions is quite complex. Free etal ions do not exist in aqu~us solution but are M al ays present as aqua co pl exes of the type (H20)i. where n = 2-6 2nd n d not 8 the oxidation state of the metal ion. Thee quo complexes c n easily be crystallized out from their solutions. Most of the e cOllplexes are color d and absorb t pecific ave lengths in the visible region o~the electro magnetic radiations. The absDrption of light by transition met 1 complexes have been the subject of n rous investigations extented over a p riod of nearly ighty y ars. The first trustworthy quantitative data is that furnished in 1892 on th olutions of chlorides, sulphatea and nitrates of copp r. Sine then the UV andvvisible spectra of inorg ~ic i DB ~e kn n n t ; r cently that uch progr a he been ada in an underst nding of the b sia of the absorption bands which re being observed. The spectra is essentially due to interaetion between a set of attached groups (ligands) and the ato.io orbitals of th 0 ntr 1 etal ion. The fre ion of' any transition metal ba partially filled degenerate d-orbitals which co e und r the direct attack of electronic fielda of the lig nds, brought upto it fro various pr fered dir ctiona. The result is a crystal field splitting of the five deg nerate d-orbitala in a aanner which dep nda on the strength of the ligand field and the 5y try of the co plex. The absorption speetr of a complex ion in the visible r gion u ually rises fro th electronic j pa between these aeper te d-orbitals.