Photochemistry of bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)strontium tetraglyme solutions for eventual liquid phase photochemical deposition

The mechanism of Sr(hfac)2TG (hfac = 1,1,1,5,5,5,hexafluoro-2,4-pentanedionato and TG, tetraglyme = 2,5,8,11,14-pentaoxapentadecane) photodegradation was investigated in methanol and dichloromethane at 254 and 300 nm. In methanol, photodegradation led to SrF2 through the attack of fluoride on the metal, occurring from the CF3 group in the intraligand excited state π–π*. In dichloromethane, a mixture of SrCl2 and SrF2 was obtained in proportions dependent on the initial complex concentration and irradiation wavelength. SrF2 was formed by photoexcited species of the complex with the same mechanism occurring in methanol. SrCl2 was formed by a solvent-initiated reaction at 254 nm, involving substitution of ligand by chloride ion, coming from photochemical solvent decomposition, whereas at 300 nm it was formed by a solvent–assisted reaction, involving an electron transfer to solvent from excited ligand in triplet state. The photochemical kinetics were followed by UV spectrophotometry, the photodecomposition products were recognized by ESI-mass, XRD and XPS. The Sr(hfac)2TG photodegradation was usefully exploited to obtain pure thin films or mixture of SrCl2 and SrF2 by the LPPD technique, operating in suitable experimental conditions. The films were characterized by SEM, XPS and XRD.