nitrosyls with nonporphyrin ligands (such as amines, Schiff
bases, thiolates, and ligands with carboxamide groups) readily
release NO upon illumination and generate Ru(III) pho-
toproducts. In contrast, photolysis of ruthenium nitrosyls derived
from porphyrins is followed by a rapid recombination that
reduces the release of NO. To date, notable progress has been
made in the area of [RuNO]^6 species derived from polydentate
ligands with strong absorption bands in the visible/NIR region
that could be used for site-specific light induced NO delivery
(75,97– 101 ).
Dinuclear hydrotris(pyrazolyl)borate complexes of ruthenium
were reported to be NN coupled by two nitrosyl ligands. These
complexes undergo transformation of the NN bridged into the
oxo-bridged dinuclear complexes with the release of N 2 O. The
NN bond is easily cleaved by oxidation and regenerated again
by reduction. This observation would provide significant infor-
mation regarding the mechanism of NO reduction to N 2 O by
nitrosyl complexes( 102 ).
Similarly to the iron complexes, the nitrite ruthenium com-
pounds might serve as photochemical NO delivery agents( 103 ).
Also the triruthenium cluster, [Ru 3 (m 3 -O)(m-CH 3 COO) 6 (CO)(L 1 )
(L 2 )] (where L 1 ¼[(NC 5 H 4 )CH 2 NHC(O)(CH 2 ) 10 S] 2 ,L 2 ¼4-
methylpyridine), which forms a self-assembled monolayer is able
to coordinate NO. The NO ligand can be selectively introduced
into the cluster to replace the originally bound CO ligand when
the Ru 3 cluster is oxidized by one electron, and part of the coor-
dinated NO can also be desorbed from the resultant NO-bound
monolayer when the cluster is reduced by one-electron from its
original oxidation state( 104 ). These findings demonstrate also
new prospects for the NO reactivity pathways in the interfacial
environmental space.
B.3. Copper NO complexes
NO is scavenged by Cu(II) complexes and diverse reaction pat-
hways were reported( 34 ):
i. Gaseous NO forms stable adducts with copper complexes as
in the case of dithiocarbamates, that changes their toxic pro-
perties (35,105).
ii. Cu(II) compounds are reduced, whereas NO is oxidized to
NO 2 ; such a pathway was suggested for copper complexes
with 1,10-phenantroline and its derivatives, for example:METAL COMPLEXES AS SOLAR PHOTOCATALYSTS 311