Chemistry Reference
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H
N
H
N
N
S
O
N
I
II
III
(CH
2
)
3
(CH
2
)
3
NMe
2
Me
2
N
+
N
S
NMe
2
N
O
N
Me
2
N
S
+
X
IV
VII
NO
2
(CH
2
)
3
NMe
2
+
Me
2
N
S
NMe
2
N
CCCl
N
O
N
Et
2
N
NH
2
S
+
XI
V
VIII
NMe
2
NMe
2
CCCH
Me
Me
CH
2
Me
+
N
N
N
S
+
S
N
NH
2
Me
2
N
VI
IX
XII
SCHEME 5.1
Phenothiazines,. phenoxazines,. and. phenazines. as. artiicial. electron. acceptors. for. use. with.
oxidase-based.biosensors.
CN
C
CN
O
S
S
NC C
S
S
CN
O
XIII
XIV
XV
SCHEME 5.2
Parabenzoquinone,.tetracyanoquinodimethane,.and.tetrathiafulvalene.
methylene. green. V,. toluidine. blue. VI,. promazine. VII,. chloropromazine. VIII,. promethazine. IX,.
Meldola.blue.X,.Nile.blue.XI,.and.phenazine-methosulfate.XII.(see.Scheme.5.1)..These.mediators.
were.often.incorporated.directly.into.the.paste,.alone.or.together.with.enzymes.(in.case.of.second-
generation.biosensors),.but.many.efforts.have.been.directed.to.improve.their.immobilization.at.the.
electrode.surface.and.to.prevent.their.leaching.into.the.solution..This.was.especially.achieved.by.
means.of.their.adsorption.onto.inorganic.particles.(e.g.,.silica.or.other.metal.oxides),.which.were.
subsequently.dispersed.in.the.carbon.paste.matrix.
Other. organic. electrocatalysts. are.
p
-benzoquinone. XIII. and. related. compounds,. tetracya-
noquinodimethane. XIV,. and. tetrathiafulvalene. XV. (Scheme. 5.2).. Finally,. an. important. class. of.
mediators.widely.used.as.carbon.paste.modiiers.is.illustrated.in.Scheme.5.3.and.represents.organo-
metallic.compounds,.such.as.ferrocene.XVI.and.ferrocene-based.derivatives,.osmium-bipyridine.
complexes.(e.g.,.osphendione.XVII,.Scheme.5.3)..Metal.porphyrins.and.especially.those.based.on.
cobalt. or. copper. (e.g.,. cobalt-tetraphenyl-porphyrin. XVIII),. and. cobalt. phthalocyanines,. are. also.
very.frequently.used.(Scheme.5.4).
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