The immobilization and properties of the nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF6)(2), Ru-NO, entrapped in a silica matrix by the solGel process is reported herein. The entrapped nitrosyl complex was characterized by spectroscopic (UV-vis, infrared (IR), X-ray photoelectron, and C-13 and Si-29 MAS NMR) and electrochemical techniques. The entrapped species exhibit one characteristic absorption band in the UV-vis region of the electronic spectrum at 354 nm and one IR v(NO) stretching band at 1865 cm(-1), as does the Ru-NO species in aqueous solution. Our results show that trans-[Ru(NO)Cl(cyclam)](PF6)(2) can be entrapped in a SiO2 matrix with preservation of the molecular structure. However, in a SiO2/SiNH2 matrix, the complex undergoes a nucleophilic attack by the amine group at the nitrosonium. Irradiation of the complex, entrapped in the SiO2 matrix, with light of 334 nm, resulted in NO release. The material was regenerated to its initial nitrosyl form by reaction with nitric oxide. (c) 2006 Elsevier Inc. All rights reserved.