A ruthenium nitrosyl with 4-vinylpyridine (4-vpy) as one ligand, namely, [Ru(Me2bpb)(NO)(4-vpy)](BF4) (1), has been synthesized and structurally characterized. This diamagnetic {Ru-NO}6 nitrosyl is photoactive and readily releases NO upon exposure to low-intensity (5-10 mW) UV light (quantum yield at 300 nm = 0.18). Radical-induced copolymerization of 2-hydroxyethyl methacrylate (HEMA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of 1 has afforded a 1-pHEMA, a transparent hydrogel in which 1 is covalently attached to the polymer backbone. Exposure of 1-pHEMA to UV light (5-10 mW) results in rapid release of NO (detected by NO electrode) that can be delivered to biological targets such as myoglobin. The photoactivity of 1-pHEMA is strictly dependent on exposure to UV light.

A light-activated NO donor, [Mn(PaPy3)(NO)]ClO4 (1a), has been incorporated into HEMA-based polymer hydrogel and the nitrosyl-polymer conjugate materials 1ax · HG and 1ax · HGMB have been characterized. The NO releasing properties and antibacterial capabilities of these materials in conjunction with growth attenuators such as hydrogen peroxide and methylene blue (MB) are reported. Since the nitrosyl releases NO only upon exposure to light, materials like 1ax · HGMB could be used as wound dressings that deliver NO under controlled conditions.

Although nitric oxide (NO) delivery systems have been fabricated with sol-gel-based materials, remote control of such systems with light has not been achieved. In this work, a fiber optic-based NO delivery system is described in which the photoactive metal-nitrosyl, [Mn(PaPy3)(NO)]ClO4 (1), has been employed in a sol-gel material. The material (1•FO) contains the manganese-nitrosyl which releases NO upon illumination with visible light. The NO-releasing capacity of 1•FO has been measured with an NO-sensitive electrode and the spatial diffusion of NO in solution has been visualized using the Griess reaction. The utility of 1•FO has been demonstrated in effective reduction of bacterial loads of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus (MRSA). The results suggest that a device that releases NO via illumination by optical fiber may have clinical applications in combating infections with both Gram-positive, Gram-negative and to some degree antibiotic resistant bacteria.

Three ruthenium nitrosyls, namely, [(Me(2)bpb)Ru(NO)(OAc)], [(Me(2)bpb)Ru(NO)(OBz)] (1), and [(Me(2)Qb)Ru(NO)(qca)](BF(4)) (2), have been synthesized from designed ligands with carboxamido-N donors. In all three complexes, a carboxylato-O donor is trans to the bound NO. The structures of 1 and 2 have been determined by X-ray crystallography. The nearly linear Ru-N-O bond angles [175.18(18) degrees and 175.0(3) degrees, respectively] and diamagnetism of the two nitrosyls are indicative of the {Ru-NO}(6) configuration. All three complexes exhibit nu(NO) in the range 1830-1890 cm(-1). When solutions of 1 and 2 are exposed to low-intensity (milliwatts) UV light, rapid release of NO is observed. The results of photochemical measurements indicate that the placement of the carboxylato-O donor trans to NO promotes the photorelease of NO in these nitrosyls much like Cl(-) and py. The presence of the carboxamido-N donor is, however, essential for the observed NO photolability because the structurally similar nitrosyl [(pyca)(2)Ru(NO)(Cl)] (3) (with carboxylato-O trans to NO) does not release NO upon exposure to UV light. Extension of conjugation in the ligand frame (quinoline rings in place of pyridine rings) increases both the rate of NO photorelease and the quantum yield of 2 compared to 1. The results of this investigation confirm that the combination of carboxamido-N donor(s) in the ligand frame and carboxylato-O trans to NO is a new structural motif in photoactive {Ru-NO}(6) nitrosyls.