The Solid State Photochemical Decomposition of Potassium Ethylenediaminetetraacetatomanganate (III)

Abstract

The photochemical effect on the decomposition of solid potassium ethy enediaminetetraacetatomanganate (III)was examined by irradiating it with a mercury lamp(Toshiba SHL-100UV) at a distance of 15 cm. The principal mercury line spectra occurred between 250 and 600nm, below 300 nm the intensity was weak and it showed maximum at 546 nm.
Infrared spectra of K[MnEDTA]e2(1/2) H20 and the reaction products were L e4amined by the NujoFrtiull method. The spectrum of the chelate before irradiation indicated the pres. ence of'eoorainated carboxylic acid group band at 1680 cm i. However, the intensity of this bapd decreased markedly a ter irradiation, and a new band appeared at ab6ut 1610 cmi, due to the reductio: n-of the manga: nese(III)chelate to the manganese(II)1 According to Sievers and B-aMii-a r, b D, (Coo) chanW wh6h the ratio of metal ion charge to its radius is 3.6thg sqrpe was true for the change of manganese(III)to manganese(II)and the above mentioned shift of band was thus well explained. The 2349 cm th band shownl in the Fig.1 was due to the CO2 gas produced in the decompositon process.
The. ch-ange of the powder surface diffuse reflectance spectra of the chelate by irradiation is given in Fig.2. The spectrum of the initial chelate had peak maxima, one at 5PO nm and 6ther in the region lower than 330 nm. Aftet irradiation, both maxima dis-appeareq.
Tha process oV the photochemical decomposition may be shown by the following fashion.