Modification of immobilized metal complexes toward the design and synthesis of functional materials for nitric oxide delivery

Functional polymeric materials containing immobilized metal complexes with the potential to bind nitric oxide (NO) are described. The materials were synthesized using template copolymerization techniques and contain immobilized metalloporphyrin and metallosalen (N,N'-bis(salicylidene)-1,2-ethylenediaminato(2-)) sites where NO binding occurs. A potential drawback of current materials designed for NO-delivery is the rebinding of NO to the material after release. To minimize this undesirable rebinding event, materials were prepared in which immobilized sites contain additional covalently-linked functional groups that can bind to the metal centers after NO dissociation. A model system with a covalently attached Co(II)salen complex and pyridine groups confirmed that the immobilized sites bind NO in the presence of the additional ligands. Attempts to immobilize an iron porphyrin, containing two axial imidazole ligands, were unsuccessful because the lability of the iron center prevented the formation of a stable template. Instead, the desired material was achieved by selecting Co-III porphyrin with axially coordinated imidazole ligands as the template complex. Once immobilized, a procedure was developed to remove the cobalt ions and incorporate iron into the sites. The site structure of these new immobilized sites was examined spectroscopically. (c) 2006 Wiley Periodicals, Inc.