26 November 1999 Ž . Chemical Physics Letters 314 1999 83–90 www.elsevier.nlrlocatercplett ž / 2q Physicochemical properties of Ru bpy entrapped in silicate 3 bulks and fiber thin films prepared by the sol–gel method Krzysztof Maruszewski a,b, ) , Marek Jasiorski a,b , Malgorzata Salamon b , Wieslaw Stre ¸ k a a Institute for Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50-950 Wroclaw, Poland ´ b Chemistry Department, Opole UniÕersity, Oleska 48, 45-951 Opole, Poland Received 17 June 1999; in final form 27 September 1999 Abstract Ž Ž . 2q . Silicate porous xerogels doped with ruthenium bipyridine Ru bpy complex have been obtained in the bulk form and 3 in thin films on optical fibers. The hypsochromic shifts in the absorption and emission maxima are accompanied by fourfold increase in the lifetimes of the entrapped complex. The temperature-dependent lifetimes reveal that silicate xerogels induce two competing thermally activated processes in the excited state decay of the immobilized complex. The excited state Ž . 2q lifetimes of the doped bulk xerogels and the fibers coated with thin films containing Ru bpy are virtually identical to 3 those obtained for the fibers coated with additional gas-impermeable layers. q 1999 Elsevier Science B.V. All rights reserved. 1. Introduction Ž . Polypyridine complexes of Ru II have attracted the attention of researchers for many decades, mainly due to their chemical robustness and a wide variety w x of photochemical processes which they display 1–4 . Better understanding of the basic processes underly- Ž . 2q ing the physicochemical behavior of Ru bpy and 3 its analogues has stimulated development of many possible applications of this class of molecules. One of the basic requirements of practical systems is that Ž the active molecules should be immobilized in or . w x on some sort of a solid matrix 5–8 . This provides mechanical stability as well as enabling the introduc- ) Corresponding author. Fax: q48-71-3441-029; e-mail: marusz@int.pan.wroc.pl tion of subtle modifications of the dopant properties due to the specific host–guest interactions. Applica- tions of such doped solid materials span a wide w x range of fields – from catalysis 9,10 to photosensi- w x tizers in solar energy conversion schemes 11,12 . w x One of the most often used matrices are zeolites 13 which are well suited for physical adsorption on their surfaces as well as for doping with molecules from Ž . 2q w x Ž . 2q the Ru bpy family 14–22 . Since Ru bpy is 3 3 larger than the open ‘windows’ leading into most of the known zeolite structures, it is usually necessary w x to adopt the ‘ship-in-bottle’ synthetic strategy 14,17 . This method is based on stepwise creation of the complexes within the zeolite supercages and zeolite Y is an often employed matrix thanks to its large Ž . supercages ca 1.2 nm . However, this method has an important restriction caused by the fixed size of 0009-2614r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2614 99 01130-6