Me al
Based
D ugs
Vol.
7,
N .
6,
2000
TERNARY
COPPER(II)
COMPLEXES
IN
SOLUTION
I21
FORMED
WITH
8-AZA
DERIVATIVES
OF
THE
ANTIVIRAL
NUCLEOTIDE
ANALOGUE
9-
[2-(PHOSPHONOMETHOXY)ETHYL]
ADENINE
(PMEA)
Raquel
B.
G6mez-Coca
,9-,
La isa
E.
Kapinos
,
An onin
Ho13
3,
Rosa io
A.
Vilaplana
,
F ancisco
Gonz ilez-Vilchez
and
Helmu
Sigel
*1
Ins i u e
o
Ino ganic
Chemis y,
Uni e si y
o
Basel,
Spi als asse
51,
CH-4056
Basel,
Swi ze land
<[email p o ec ed]>
2
Ino ganic
Chemis y
Depa men ,
Facul y
o
Chemis y,
Uni e si y
o
Se ille,
E-41071
Se ille,
Spain
Ins i u e
o
O ganic
Chemis y
and
Biochemis y,
Academy
o
Sciences,
CZ-
16610
P ague,
Czech
Republic
Dedica ed
o
he
memo y
o
P o esso
Ma c
Leng,
an
ou s anding
scien is
and
iend
Abs ac
The
s abili y
cons an s
o
he
mixed-ligand
complexes
o med
be ween
Cu(A m)
2+,
whe e
A m
2,2’-
bipy idine
(Bpy)
o
1,10-phenan h oline
(Phen),
and
he
dianions
o
9-[2-(phosphonome hoxy)e hyl]-8-aza-
adenine
(9,8aPMEA)
and
8-[2-(phosphonome hoxy)e hyl]-8-azaadenine
(8,8aPMEA)
(bo h
also
abb e ia ed
as
PA
2-)
we e
de e mined
by
po en iome ic
pH
i a ions
in
aqueous
solu ion
(25
C;
I
0.1
M,
NaNO3).
All
ou
e na y
Cu(A m)(PA)
complexes
a e
conside ably
mo e
s able
han
co esponding
Cu(A m)(R-PO3)
species,
whe e
R-PO-
ep esen s
a
phosph(on)a e
ligand
wi h
a
g oup
R
ha
is
unable
o
pa icipa e
in
any
kind
o
in e ac ion
wi hin
he
complexes.
The
inc eased
s abili y
is
a ibu ed
o
in amolecula
s ack
o ma ion
in
he
Cu(A m)(PA)
complexes
and
also
o
he
o ma ion
o
5-membe ed
chela es
in ol ing
he
e he
oxygen
p esen
in
he
-CH2-O-CH2-POZ3
esidue
o
he
azaPMEAs.
A
quan i a i e
analysis
o
he
in amolecula
equilib ia
in ol ing
h ee
s uc u ally
di e en
Cu(A m)(PA)
species
is
ca ied
ou .
Fo
example,
abou
5%
o
he
Cu(Bpy)(8,8aPMEA)
sys em
exis
wi h
he
me al
ion
solely
coo dina ed
o
he
phosphona e
g oup,
14%
as
a
5-membe ed
chela e
in ol ing
he
-CH2-O-CH2-PO3
z-
esidue,
and
81%
wi h
an
in amolecula
s ack
be ween
he
8-azapu ine
moie y
and
he
a oma ic
ings
o
Bpy.
The
esul s
o
he
o he
sys ems
a e
simila
hough
wi h
Phen
a
o ma ion
deg ee
o
abou
90%
o
he
in amolecula
s ack
is
eached.
The
exis ence
o
he
s acked
species
is
also
p o en
by
spec opho ome ic
measu emen s.
In
addi ion,
he
Cu(A m)(PA)
complexes
may
be
p o ona ed,
leading
o
Cu(A m)(H;PA)
+
species
o
which
i
is
concluded
ha
he
p o on
is
loca ed
a
he
phosphona e
g oup
and
ha
he
complexes
a e
mainly
o med
by
a
s acking
adduc
be ween
Cu(A m)
2+
and
H(PA)-.
Conclusions
ega ding
he
biological
p ope ies
o
hese
azaPMEAs
a e
sho ly
indica ed.
1.
INTRODUCTION
Nucleo ides
and
hei
me al
ion
complexes
play
a
key
ole
in
all
aspec s
o
me abolism
and
he e o e,
a emp s
o
exploi
nucleo ide
analogues
as
d ugs
a e
old
(e.g.[3l).4.Among
he
analogue,
s
wi h
biological
p ope ies
9-[2-(phosphonome hoxy)e hyl]adenine
(PMEA),
an
analogue
o
(2-
deoxy)-adenosiae
5’-monophosoha e
[(d)AMp2-],
is
a
mos
ema kable
one;
i
exhibi s
an i i al,
581
cy os a ic
[9,11
and
an ia h i ic
[ l]
e ec s.
Conside ing
he
b oad
biological
ac i i y
o
PMEA,
i
is
no
su p ising
ha
many
de i a i es
ha e
been
syn hesized
and
s udied,
[2]
and
i
is
now
clea
ha
in
o de
o
be
an i i ally
ac i e,
PMEA
and
i s
de i a i es
mus
be
phospho yla ed
in
he
cell
o
he
diphospha e
(PMEApp
4-)
and
his
is
hen
ecognized
by
DNA
polyme ases
as
a
subs a e
and
inco po a ed
in o
he
g owing
nucleic
acid
chain
which
is
e mina ed
he ea e .
[3’4]
Knowing
ha
polyme ases
depend
on
he
p esence
o
me al
ions
[15’16]
and
ha
he
nucleoside
5’- iphospha es
mus
be
p esen
as
complexes
(mos ly
Mg2+)
[7]
we
ha e
been
s udying
complexes
o
PMEA
[8"24]
and
a
mechanism
o
ac ion
has
been
p oposed
ecen ly
[25’261
in
which
he
co ec
loca ion
o
wo
me al
ions
a
he
iphospha e
chain
o
achie ing
a
desi ed
eac ion
is
emphasized.
[26]
In
o he
wo ds,
he
co ec
o ien a ion
o
he
nucleoside
5’- iphospha e
o
i s
analogue
in
he
ac i e-si e
ca i y
o
he
enzyme
is
c ucial.
[26]
One
o
he
ways
in
which
he
co ec
ancho ing
p ocess
o
a
subs a e
in
he
ac i e
si e
o
an
’z7]
enzyme
can
be
achie ed,
is
ia
s acking
in e ac ions
o
he
nucleobase
esidue,
e.g.
wi h
an
indole
moie y
o
a
yp ophan
uni .
[28]
Fo
his
eason
we
became
in e es ed
in
he
PMEA
ela i es,
9-[2-(phosphonome hoxy)e hyl]-8-azaadenine
(9,8aPMEA)
and
8-[2-(phosphonome hoxy)e hyl]-8-
azaadenine
(8,8aPMEA)
(see
Fig.
1),
and
he
ques ion
was:
Do
he
s acking
p ope ies
o
PMEA,
9,8aPMEA
and
8,8aPMEA
di e ?
To
his
end
we
measu ed
he
s abili ies
o
he
mixed
iigand
Cu(A m)(PA)
complexes
whe e
A m
2,2’-bipy idine
(Bpy)
o
1,10-phenan h oline
(Phen)
and
2
2
PA-
9,8aPMEA-
o
8,8aPMEA
2-.
These
Cu(A m)(PA)
complexes
can
old
such
ha
he
313
Helmu
Sigel
e
al.
Te na y
Coppe (II)
Complexes
in
Solu ion[I,2]
Fo med
wi h
8-Aza
De i a i es
o
he
An i i al
Nucleo ide
Analogue
9-[2-(Phosphonome hoxy)e hyl)Adenine(PMEA)
a oma ic
ings
o
Bpy
o
Phen
can
in e ac
wi h
he
8-azaadenine
esidues.
In
ac ,
Bpy
and
Phen
ha e
p o en
e y
help ul
as
indica o s
o
e alua ing
he
s acking
capabili ies
o
a oma ic
esidues
in
me al
ion
complexes.
[21
A
s acking
in e ac ion
o
he
indica ed
kind
should
be
e lec ed
in
an
enhanced
o e all
complex
s abili y.p,29,l
Indeed,
he
esul s
ob ained
p o e
such
enhanced
s abili ies
and
hese
a e
compa ed
now
wi h
hose
ob ained
ea lie
pI
o
he
co esponding
Cu(A m)(PMEA)
complexes.
NH2 NH2
1N
PMEA2-
9’8aPMEA2-
N I
8’8aPMEA2-
7#
9
-O -O
3
o
/CH2
o
/CH2
-0
-O--P--C
/
C"
-O--P--C
/
C"
|
c/Oc/CH2
H2
H2
H2
H2
-O--P--
0
0
II
H:,
0
Figu e
1.
Chemical
s uc u es
o
he
dianions
o
9-[2-(p.hosphonome hoxy)e hyl]adenine
(PMEA2-),
9-[2-(phosphonome hoxy)e hyl]-8-azaadenine
(9,8aPMEA
-)
and
8-[2-(phosphonome hoxy)e hyl]-8-
azaadenine
(8,8aPMEA2-).
The
h ee
nucleo ide
analogues
a e
also
abb e ia ed
as
PA
2-.
2.
MATERIALS
AND
METHODS
2.1.
Ma e ials
Two old
p o ona ed
9-[2-(phosphonome hoxy)e hyl]-8-azaadenine,
i.e.
H2(9,8aPMEA)
,
and
i s
8-
isome
8-[2-(phosphonome hoxy)e hyl]-8-azaadenine,
H2(8,8aPMEA)
,
we e
syn hesized
by
alkyla ion
o
8-
azaadenine
wi h
a
syn hon
ca ying
he
s uc u al
ea u es
o
he
equi ed
side
chain.
[32]
2,2’-Bipy idine,
1,10-
phenan h oline
monohyd a e,
and
he
ni a e
sal s
o
Na
+
and
Cu
2+
(all
p o
anal si)
we e
om
Me ck
AG,
Da ms ad ,
FRG.
All
he
o he
eagen s
we e
iden ical
wi h
hose
used
p e iously
pal
and
all
solu ions
o
he
po en iome ic
pH
i a ions
we e
p epa ed
wi h
ul apu e
CO2- ee
wa e
as
desc ibed,
phi
2.2.
Po en iome ic
pH
Ti a ions
The
appa a us
o
he
po en iome ic
pH
i a ions,
he
calib a ion
p ocedu e,
he
compu e s,
and
he
calcula io_n
me hods
used
now
a e
he_same
as
in
[24].
The
s abili y
cons an s
hm (H.9
8aP4ZA)
and
K (9
8aP4ZA),
whe e
M
e+
Cu.(Bpy)
2+
o
Cu(Phen)
2+,
we e
de e mined
by
i _ a ing
30
m_L
o
aq6ous
0.83
mM
[: O3,
0.4
2+
2+
mM
9,8aPMEA
-,
and
4.4
mM
o
2.2
mM
Cu
/A m
(i.e.,
Cu
:A m:PA
11:11:1
o
5.5:5.5:1)
unde
N2
(25
C;
I
0.1
M,
NaNO3)
wi h
mL
0.03
M
NaOH.
Each
i a ion
was
epea ed
in
he
absence
o
ligand
and
he
di e ences
in
NaOH
consump ion
be ween
such
a
pai
o
i a ions
we e
used
o
he
calcula ions.
The
condi ions
o
he
measu emen s
wi h
8,8aPMEA
we e
iden ical
wi h
hose
gi en
abo e
o
9,8aPMEA.
I
may
be
added
ha
he
acidi y
cons an s
K2(PA)
and
K IH(PA
o
H2(PA)
and
H(PA)-,
l
l
+
espec i ely,
and
he
s abili y
cons an s
/Cu(H.PA,
and/Cu,PA o
he
bina y
Cu(H;PA)
and
Cu(PA)
.......
I331
complexes
we e
de e mined
unde
he
co esponding
condi ions.
Fu he mo e,
he
abo e
condi ions
a e
simila
o
hose
desc ibed
in
[24].
Unde
he
gi en
expe imen al
condi ions
he
o ma ion
o
he
Cu(A m)
2+
complexes
is+
p ac ically
comple e
[341
(in
ag eemen
he ewi h,
i a ions
o
solu ions
wi h
HNO3
and
HNO3
plus
Cu
/A m
we e
iden ical
in
he
lowe
pH
ange)
and
he e o e,
he
e alua ion
o
he
i a ion
da a
o
he
e na y
complexes
could
be
done
in
he
way
desc ibed
p e iously
o
bina y
complexes.
[241
The
Cu(Bpy)+/9,8aPMEA
5.5:1
and
11:1
sys ems
we e
e alua ed
in
he
pH
ange
3.4-5.3,
eaching
o ma ion
deg ees
o
abou
4.5
and
8%
o
Cu(Bpy)(H;9,SaPMEA)
+
and
64
o
78%
o
Cu(Bpy)(9,SaPMEA),
espec i ely.
Fo
he
Cu(Phen)Z+/9,SaPMEA
5.5:1
and
l:l
sys ems
da a
we e
collec ed
in
he
pH
anges
3.4-5.0
and
3.4-4.8,
espec i ely,
eaching
o ma ion
deg ees
o
abou
8
and
14%
o
Cu(Phen)(H;9,SaPMEA)
+
and
abou
61
o
66%
o
Cu(Phen)(9,SaPMEA).
The
uppe
limi s
o
he
e alua ed
pH
anges
we e
always
de e mined
by
he
beginning
o
he
hyd olysis
o
he
Cu(A m)a
species.
Simila ly,
he
Cu(Bpy)2+/8,SaPMEA
5.5:1
and
11:1
sys ems
we e
e alua ed
be ween
p+H
3.6-5.3
and
3.5-5.3,
espec i ely,
wi h
o ma ion
deg ees
o
abou
7
and
12%
o
_Cu(Bpy)(H;8,SaPMEA)
and
abou
62
o
76%
o
Cu(Bpy)(8,SaPMEA),
espec i ely.
Fo
he
Cu(Phen)e+/8,SaPMEA
5.5:1
and
l:l
sys ems
da a
we e
collec ed
in
he
pH
anges
3.6-5.0
and
3.5-5.0,
espec i ely,
eaching
o ma ion
deg ees
o
abou
12
and
19%
o
Cu(Phen)(H;8,SaPMEA)
+
and
60
o
73%
o
Cu(Phen)(8,SaPMEA),
espec i ely.
The
calcula ed
s abili y
cons an s
showed
no
dependence
on
pH
o
on
he
excess
o
Cu-+/A m
employed.
The
inal
esul s
o
he
cons an s
a e
in
each
case
he
a e ages
o
he
e alua ions
o
i e
independen
pai s
o
i a ions.
Howe e ,
due
o
he
low
o ma ion
deg ees
eached
o
he
monop o ona ed
M(H;PA)
+/-
species,
he
s abili y
cons an s
gi en
o
hese
complexes
mus
be
conside ed
as
es ima es.
These
es ima es
we e
u he
subs an ia ed
by
compa isons
wi h
he
known
[181
alues
o
he
Cu(A m)(H;PMEA)
+
H
complexes
by
aking
he
di e en
acidi y
cons an s
(Kz(pA))
in o
accoun .
314
Me al
Based
D ugs
Vol.
7,
N .
6,
2000
2.3.
Spec opho ome ic
Measu emen s
The
UV-Vis
spec a
o
he
Cu2+/Phen/9,8aPMEA
o
8,8aPMEA
sys ems
we e
eco ded
in
aqueous
solu ion
and
1-cm
cells
wi h
a
Va ian
Ca y
3C
spec opho ome e
connec ed
o
an
IBM-compa ible
desk
compu e
(OS/2
sys em)
and
an
EPSON
s ylus
1500
p in e .
The
pH
o
he
solu ions
was
adjus ed
by
do ing
wi h
ela i ely
concen a ed
NaOH
and
measu ed
wi h
a
Me ohm
713
pH
me e
using
a
Me ohm
6.204.100
glass
elec ode.
Fu he
de ails
a e
gi en
in
he
legend
o
Figu e
4
in
Sec ion
3.5.
3.
RESULTS
AND
DISCUSSION
All
po en iome ic
pH
i a ions
(25
C;
I
0.1
M,
NaNO),
he
esul s
o
which
a e
summa-
ized
below,
we e
ca ied
ou
wi h
a
ligand
concen a ion
o
0.4
mM
and
a
CuZ+/A m
concen a-
ions
equal
o
o
below
4.4
mM.
Unde
hese
condi ions
sel -s acking
o
he
ligands
is
negligibly
small
as
has
been
shown
[81
o
PMEA;
he
same
applies
o
he
sel -associa ion
o
Cu(Phen) +.
[3]
This
means,
he
sel -associa ion
is
negligible
o
any
o
he
eac an s
unde
he
p esen
expe imen-
al
condi ions
and
he
esul s
gi en
below
ce ainly
e e
o
monome ic
species.
3.1.
De ini ion
o
he
Equilib ium
Cons an s
The
ligands
9,8aPMEA
2-
and
8,8aPMEA
2-,
abb e ia ed
as
PA
2-
(Fig.
1),
may
bind
wo
p o ons
a
he
phosphona e
g oup
and
one
a
N1
o
he
adenine
moie y.
F om
H(PMEA)
+
he
i s
p o on
is
eleased
om
he
-P(O)(OH)2
esidue
[]
wi h
pKa
1.2
and
he
same
may
be
su mised
o
he
o he
H(PA)
+
species.
Hence,
o
he
p esen
wo k
only
he
elease
o
he
p o on
om
he
+
(N
1)H
si e,
ollowed
by
he
one
om
he
-P(O)z(OH)-
g oup
need
o
be
conside ed:
H2(PA)
+/-
H(PA)-
+
H
+
(la)
/H2(PA)
[H(PA)-]
[H+]/[H2(PA)
+]
(1
b)
H(PA)-
PA
2-
+
H
+
(2a)
/H(PA)
PA2-]
[H+]/[H(PA)
-]
(2b)
Indeed,
he
expe imen al
da a
o
he
po en iome ic
pH
i a ions
o
he
M2+/pA
sys ems,
whe e
M
2+
Cu
2+,
Cu(Bpy)
2+
o
Cu(Phen)
2+,
can
be
ully
desc ibed
by
conside ing
he
acidi y
cons an s
o
Ha(PA)
+/-
(eqs
(1)
and
(2))
and
he
ollowing
equilib ia
(3)
and
(4),
M
2+
+
H(PA)-
,
M(H;PA)
+
(3a)
KM(H;PA)
[M(H;PA)+]/([M
2+]
[H(PA)-])
(3b)
M
2+
+
PA
2-
:
M(PA)
(4a)
/(PA)
[M(PA)]/([
M2+]
[pA2-])
(4b)
p o ided
he
e alua ion
o
he
da a
is
es ic ed
o
he
pH
ange
below
he
beginning
o
he
o ma-
ion
o
hyd oxo
complexes
which
was
e iden
om
he
i a ions
o
M
2+
wi hou
ligand.
I
should
be
no ed
ha
in
o mulas
like
M(H;PA)
+
he
H
+
and
he
PA
2-
a e
sepa a ed
by
a
semicolon
o
acili a e
eading,
ye
hey
appea
wi hin
he
same
pa en heses
o
indica e
ha
he
p o on
is
a
he
ligand
wi hou
de ining
i s
loca ion.
Equilib ia
(3a)
and
(4a)
a e
connec ed
ia
equilib ium
(5a),
and
he
co esponding
acidi y
cons an
(eq.
(5b))
may
be
calcula ed
wi h
equa ion
(6):
M(H;PA)
+
M(PA)
+
H
+
]-IM(H;PA
[M(PA)]
[H+]/[M(H;PA)
+1
(5a)
(5b)
P/M(H;PA)
P/H(PA)
+
log
KMMM(H;PA)-
log
KMMM(PA)
(6)
The
equilib ium
cons an s
acco ding
o
equa ions
(3),
(4),
and
(5)
a e
lis ed
in
columns
2,
3,
and
4
o
Table
1,
espec i ely.
The
acidi y
cons an s
o
he
ligands
(see
oo no e
"a"
in
Table
1)
and
he
s abili y
cons an s
o
he
bina y
Cu(H;PA)
+
and
Cu(PA)
complexes
will
be
discussed
in
a
di e en
con ex .
[33]
He e
we
concen a e
on
he
p ope ies
o
he
e na y
complexes.
315
Helmu
Sigel
e
al.
Te na y
Coppe (II)
Complexes
in
Solu ion[I,2]
Fo med
wi h
8-Aza
De i a i es
o
he
An i i al
Nucleo ide
Analogue
9-[2-(Phosphonome hoxy)e hyl)Adenine(PMEA)
Table
1.
Loga i hms
o
he
S abili y
Cons an s
o
he
Te na y
Cu(A m)(H;PA)
+
(eq.
(3))
and
Cu(A m)(PA)
(eq.
(4))
Complexes
as
De e mined
by
Po en iome ic
pH
Ti a ions
in
Aqueous
Solu ion,
Toge he
wi h
he
Nega i e
Loga i hms
o
he
Acidi y
Cons an s
(eqs
(5)
and
(6))
o
he
Cu(A m)(H;PA)
+
Species
a
25
C
and
I
0.1
M
(NaNO3)
a’b
M
/M(PA)
M(PA)
log
KM(H;PA
log
P/(H;PA)
A
log
KCu/A m/PA
d
Cu(9,8aPMEA)
[33]
0.95+
0.25
3.98
+
0.04
3.8
+
0.25
Cu(Bpy)(9,8aPMEA)
1.4
+
0.25
4.56
+
0.06
3.7
+
0.3
0.58
+
0.07
Cu(Phen)(9,8aPMEA)
1.7
+
0.25
4.81
+
0.06
3.7
+
0.3
0.83
+
0.07
Cu(8,8aPMEA)
[33]
1.3
+
0.25
3.68
+
0.06
4.4
+
0.25
Cu(Bpy)(8,8aPMEA)
1.7
+
0.25
4.49
+
0.05
4.0
+
0.3
0.81
+
0.08
Cu(Phen)(8,SaPMEA)
2.0
+
0.25
4.79
+
0.07
4.0
+
0.3
1.11
+
0.09
a
The
acidi y
cons an s
o H2(9,8aPMEA)
+/-
a e
pgHH2 9
8aPMEA
2.73
+
0.02
and
pKHH(9,8aPWWA
6.85
+
0.02;
hose
o
H2(8,8aPMEA)
+
a e
pKHH2(8
8aPMEA)-"
3.56’4’
0.02
ahd
pKHH(8
8aPMEA)-
6.79
+
0.Ol.
3"3],b
b
The
e o s
gi en
a e
h ee
imes’ he
s anda d
e o
o
he
me.n
alue
o
he
sum
o
he
p obable
sys ema ic
e o s,
whiche e
is
la ge .
The
e o
limi s
o
he
de i ed
da a
(columns
4
and
5)
we e
calcula ed
acco ding
o
he
e o
p opaga ion
a e
Gauss.
The
alues
in
his
column
a e
es ima es
(see
Sec ion
2.2)
d
S abili y
cons an
di e ences
calcula ed
acco ding
o
eq.’(9).
3.2.
On
he
S uc u e
o
he
Monop o ona ed
Te na y
Cu(A m)(H;PA)
+
Complexes
The
analysis
o
po en iome ic
pH
i a ions
only
yields
he
amoun
and
dis ibu ion
o
he
species
o
a
ne
cha ged
ype;
i.e.,
u he
in o ma ion
is
equi ed
o
loca e
he
binding
si es
o
he
p o on
and
he
me al
ion
in
Cu(A m)(H;PA)
+
species.
A
compa ison
o
he
acidi y
cons an s
o
H2(9,8aPMEA)
+,
P/H2(9,8aPMEA)
2.73
an.d
P/H(9,8aPMEA)=
6.85,
wi h
pKCu(A m)(H;9,8aPMEA)
3.7
(Table
1)
o
he
Cu(A m)(H;9,8aPMEA)*
complexes
e eals
ha
he
p o on
in
hese
complexes
mus
be
loca ed
a
he
phosphona e
g oup,
since
me al
ion
coo dina ion
mus
gi e
ise
o
an
acidi ica ion,
[36,371
which
amoun s
o
A
pK
a
pKIH(9,8aPMEA)-
pKCu(A m)(H;9,8a+PMEA)
(6.85
4-
0.02)
--(3.7
+
0.3)
3.15
+
0.3
in
he
p esen
case.
In
he
Cu(A m)(H;8,SaPMEA)
species
he
p o on
is
also
clea ly
bound
a
he
phosphona e
g oup
hough
he
acidi ica ion
due
o
he
me al
ion
migh
be
somewha
less
p onounced:
A
pK
a
PH(8,SaPMEA)-
P/Cu(A m)(H;8,8aPMEA)
(6.79
+/-
0.01)
(4.0
+-
0.3)=2.8+0.3.
Whe e
is
he
Cu(A m)
2+
uni
loca ed?
In
p inciple,
he e
a e
wo
possibili ies"
One,
whe e
Cu(A m)
2/
is
s acked
wi h
he
pu ine
sys em
o
H(PA)-,
designa ed
as
[Cu(A m)/(H;PA)]s,
and
ano he
one,
whe e
Cu(A m)
2+
is
coo dina ed
ei he
o
he
N1/N7
si es
o
he
adenine
esidue
(see
[24]),
[H;PA’Cu(A m)]a+de,
o
o
he
phosphona e
g oup
which
al eady_
ca ies
he
p o on.
Howe e ,
he
o ma ion
o
his
la e
species
wi h
bo h
he
p o on
and
Cu(A m)
+
a
he
phosphona e
g oup
is
unlikely,
in
ag eemen
wi h
p e ious
conclusions.
[241
Hence,
we
a e
le
wi h
he
species
[H;PA’Cu(A m)]a+de
and
[Cu(A m)/(H’PA)]
+,
s
and
we
ha e
o
conside
he
in amolecula
equilib ium
(7):
[H;
PA.Cu(A m)]a+de
[Cu(A m)/(H;PA)]s
(7)
An
e alua ion
ollowing
exac ly
he
ou e
desc ibed
in
[2]
leads
o
he
conclusion
ha
o
all
ou
Cu(A m)(H;PA)
+
sys ems
he
s acked
species
in
equilib ium
(7)
domina e
wi h
o ma ion
deg ees
o
mo e
han
70%,
mos
likely
being
be ween
80
and
95%.
As
one
migh
expec ,
he
o ma ion
deg ee
o
[Cu(Phen)/(H;PA)]s
is
abou
10%
la ge
han
he
one
o
[Cu(Bpy)/(H;PA)]s.
3.3.
P oo
o
an
Inc eased
S abili y
o
he
Mixed
Ligand
Cu(A m)(PA)
Complexes
[38391
The
s abili y
o
mixed-ligand
complexes
may
be
quan i ied
by
conside ing
equilib ium
(8a);
he
co esponding
equilib ium
cons an
is
calcula ed
wi h
equa ion
(9).
Cu(A m)
2+
+
Cu(PA)
....
Cu(A m)(PA)
+
Cu
2+
10
zx
log
KCu/A m/P
A
[Cu(A m)(PA)]
[Cu
2+]
[Cu(A m)
2+
[Cu(PA)]
(8a)
(8b)
A2u(A m)
--log/C(PA)
A
log
KCu/A m/P
A
log
"Cu(A m)(PA)
(9)
316
Me al
Based
D ugs
Vol.
7,
N .
6,
2000
Acco ding
o
he
gene al
ule
o
complex
s abili ies,
K
>
K?,
equilib ium
(8a)
is
expec ed
o
be
on
he
le
side
wi h
nega i e
alues
o
A
log
KCu/A m/P
A,
in
ag eemen
wi h
s a is ical
conside-
a ions,
[38’39]
i.e.,
A
log
Kcu/s a is
-0.5.
[39]
F om
e
alues
lis ed
in
column
5
o
Table
i
is
e iden
ha
equilib ium
(8)
is
signi ican ly
displaced
o
he
igh
side.
Mo e
impo an ,
howe e ,
is
a
compa ison
wi h
he
esul s
ob ained
o
he
dianion
o
phosphonome hoxye hane
(PME:-),
CH3CH2-O.CH2-PO-,
which
e lec s
he
p ope ies
o
he
side
chain
o 9,8aPMEA
2-
and
8,8aPMEA’--
(Fig.
1).
Indeed,
hese
esul s,
A
log
KCu/B ) /PME
0.13
+
0.04
and
A
log
Kcu/Phen/PM
E
0.17
+
0.05,[311a e
conside ably
smalle
han
he
alue s
o
A
log
KCu/A m/P
A
o
he
Cu(A m)(PA)
complexes,
which
means
ha
he
adenine
esidue
con ibu es
o
he
s abili y
o
he
Cu(A m)(PA)
species.
This
compa ison
hus
p o ides
he
i s
clea
hin
o
he
occu ence
o
an
in amolecula
s acking
in e ac ion
in
hese
la e
men ioned
complexes.
Ano he
way
o
e alua e
he
inc eased
s abili y
o
e na y
Cu
+
complexes,
independen ly
o
he
p ope ies
o
he
bina y
Cu(9,8aPMEA)
and
Cu(8,8aPMEA)
species,
es s
on
he
p e iously
es ablished
[2’311
s aigh -line
co ela ions
o
log
KUu( mm)
RPO
e sus
p/
po)
plo s
(eqs
(10)
c
)(
3)
and
(11)),
whe e
R-PO-
ep esen s
phospha e
monoes e
o
phosphona e
lgands
in
which
he
esidue
R
is
unable
o
in e ac
wi h
Cu(A m)Z/:
log
Ko
u(Bpy)
0.465
x
Cu(Bpy)(R-PO3)
P/H(R-PO3)
+
0.009
(10)
log
zCu(Phen)
"’Cu(Phen)(R-PO3)
0.465
x
PKH(R.PO3
+
0.018
(11)
The
e o
limi s
o
log
s abili y
cons an s
calcula ed
wi h
gi en
p/,,
alues
and
equa ions
H(R-PO3
(10)
and
(1
1)
a e
+0.07
and
+0.06
(3)
log
uni s,
espec i ely,
in
he
pH
ange
5-8.[
311
The
e e ence
lines
as
de ined
by
equa ions
(10)
and
(11)
a e
shown
in
Figu e
2,
whe e
he
s abili y
cons an s
log
Ko
u(A m)
e sus
he
acidi y
cons an s
pK
o
he
9,8aPMEA
and
Cu(
m)(P
8,8aPMEA
species
a e
also
pAl o e,
oge he
wi h
he
co esponding
da ’a
l]
o
he
Cu(A m)(PME)
sys ems.
All
hese
da a
poin s
a e
abo e
hei
e e ence
lines,
p o ing
an
inc eased
complex
s abili y
which
mus
mean
[41
ha
aside
om
2+
he
Cu(A m)
-phosphona e
coo dina ion
u he
in e ac ions
ake
place.
The
e ical
dis ances
in
Figu e
2
be ween
he
da a
poin s
due
o
Cu(A m)(9,8aPMEA),
Cu(A m)(8,8aPMEA)
and
Cu(A m)(PME)
and
he
e e ence
lines
a e
a
measu e
o
he
ex en
o
he
in amolecula
in e ac ions
in
hese
complexes
and
hey
can
be
de ined
acco ding
o
equa ion
(12)
(in
his
case,
PA
2-
also
ep esen s
PME2-)
log
ACu/A m/P
A
log
,.’Cu(A m)
log
,.’Cu(A m)
’Cu(A m)(PA)
a"Cu(A m)(PA)op
(12a)
k,-Cu(A m)
log
k,Cu(A m)
log
’"Cu(A m)(PA)exp l
"Cu(A m)(PA)calcd
(12b)
u(A m)
u(A m)
The
exp essions
log
(eq
(12b))
and
log
Kc
u
A m
PA
o
(eq
(12a))
a e
synonymous
/u(A m)(PA)calcd
p
because
he
calcula ed
alue
equals
he
s abili y
cons an
o
he
lopen’
isome ,
Cu(A m)(PA)o,,
n
2
2+
which
only
a
-PO3-/Cu(A m
)
in e ac ion
occu s.
The
i s
e m
on
he
igh
hand
side
in
equa ion
(12)
is
he
expe imen ally
de e mined
s abili y
cons an
(e .
(4)),
whe eas
a
alue
o
log
K(2 /!.
A m),
can
be
calcula ed
wi h
he
acidi y
cons an
P/’"PA’
and
he
s aigh -line
equa ions
(1--0u V(l]ai"As
indica ed
abo e,
such
a
calcula ed
alue
ha { i ies
he
s abili y
o
he
open
isome .
The
ligand
PME
2-
o e s
o
me al
ions
he
phosphona e
g oup
o
coo dina ion,
bu
an
in e -
ac ion
wi h
he
e he
oxygen
is
also
possible
as
has
epea edly
been
p o en.
[822’41’421
This
gi es
ise
o
5-membe ed
chela es
and
he e o e
equilib ium
(13a)
needs
o
be
conside ed"
H
O
ROCP,
0,,
%"M2+
R--
0,,,,
H
0
%M2"
(13a)
317

Helmu
Sigel
e
al.
Te na y
Coppe (II)
Complexes
in
Solu ion[I,2]
Fo med
wi h
8-Aza
De i a i es
o
he
An i i al
Nucleo ide
Analogue
9-[2-(Phosphonome hoxy)e hyl)Adenine(PMEA)
K
[Cu(A m)(PME)c]/[Cu(A m)(PME)op]
(13b)
The
dimensionless
equilib ium
cons an
K
(eq.
(13b))
is
calcula ed
acco ding
o
equa ion
(14),
K
10
lg
aCu/A m/PME
(14)
5,0-
4,8-
4.6-
’E
4.4-
OO
4.2
4.0-
3.8
3.6
O
3.4
E
z
m
2.8
2.6
2.4-
2.2
8,8aPMEA2-
O0
9,8aPMEA
2"
,
PME
2-
"’,Cu(Bpy)(R.PO3)
(Phen)(R-PO
3)
6.0
6.2
6.4 6.6 6.8
7.0
7.2
7.4
7.6
7.8 8.0 8.2
H
pKHH(R.PO3)
o
PKH(PA
Figu e
2.
E idence
o
an
enhanced
s abili y
o
he
e na y
Cu(A m)(9,8aPMEA)
Cu(A m)(8,SaPMEA)
((C),O),
and
Cu(A m)(PME)
(A,,)
complexes
based
on
he
ela ionship
be ween
log
/,,_
u(
Ann
u(Ann)( -PO3)
o
log
"Cu(Ann)(PA)and
PK(R-PO3)
o
pKIH(pA)
in
aqueous
solu ion
a
I
0.1
M
(NaNO
3)
and
25
C.
The
plo ed
da a
o
9,8aPMEA
and
8,8aPMEA
a e
om
Table
and
hose
o
PME
om
[31].
The
ASu(Ann)
wo
e e ence
lines
ep esen
he
log
Cu(Ann)( .po3) e sus
P/(-PO3)
ela ionship
o
e na y
Cu(A m)(R-PO3)
complexes
(eqs
(10)
and
(11));
R-PO-
symbolizes
phosphona es
o
phospha e
monoes e s
in
which
he
g oup
R
is
unable
o
unde go
any
kind
o
hyd ophobic,
s acking
o
o he
ype
o
in e ac ions,
i.e.
ligands
like
D- ibose
5-monophospha e,
me hanephosphona e
o
e hanephosphona e.
[31
The
b oken
line
holds
o
A m
Bpy
and
he
solid
line
o
A m
Phen.
Bo h
s aigh
lines
ep esen
he
si ua ion
o
e na y
complexes
wi hou
an
in amolecula
ligand-ligand
in e ac ion.
The
e ical
do ed
lines
emphasize
he
s abili y
di e ences
om
he
e e ence
lines;
hey
equal
log
ACu/A m/P
A
as
de ined
in
equa ion
(12).
and
now,
knowing
K,
he
pe cen age
o
he
closed
isome ,
Cu(A m)(PME)c,
in
equilib ium
(13a)
can
be
ob ained wi h
equa ion
(15)"
%
Cu(A m)(PME)c
100.
K/(I
+
KI)
(15)
318
Me al
Based
D ugs
Vol.
7,
N .
6,
2000
Table
2.
Quan i ica ion
o
he
S abili y
Inc ease
ia
loe
ZCu/A m/P
A
(eq.
(12))
o
he
Cu(A m)(PA)
Complexes,
whe e
PA
9,8aPMEA
2-,
8,8aPMEA
2-
o
PME
"-,
and
A m
Bpy
o
Phen,
Toge he
wi h
he
Ex en
o
he
In amolecula
Chela e
Fo ma ion
(eq.
(13))
in
he
Cu(A m)(PME)
Species
[311
in
Aqueous
Solu ion
a
25
C
and
I
0.1
M
(NaNO3)
a
log
1o
Cu(A m)(PA)
Cu(Ann)
b
Cu(Ann
Kia
Cu(Ann)(PA)exp l
Cu(Ann)(PA)calcd
log
ACu/Ann/P
A
%Cu(A m)(PME)cl
Cu(Bpy)(9,8aPMEA)
4.56
+
0.06
Cu(Phen)(9,8aPMEA)
4.81
+
0.06
3.19
+
0.07
1.37
+
0.09
3.20
+
0.06
1.61
+
0.08
Cu(Bpy)(8,8aPMEA)
4.49
+
0.05
3.17
+
0.07
1.32
+
0.09
Cu(Phen)(8,8aPMEA)
4.79
+
0.07
3.18
+
0.06
1.61
+
0.09
Cu(Bpy)(PME)
[31]
3.86
+
0.03
3.27
+
0.07
0.59
+
0.08
2.89
+
0.68
74
+
5
Cu(Phen)(PME)
31]
3.90
+
0.04
3.28
+
0.06
0.62
+
0.07
3.17
+
0.69
76
+
4
Fo
he
e o
limi s
see
oo no e
’b’
o
Table
1.
These
alues
a e
om
column
3
in
Table
1.
These
cons an s
we e
calcula ed
wi h
eqs
(10)o
(11)
and
he
H
pK(pA
alues
gi en
in
oo no e
’a’
o
Table
1.
See
eqs
(13b)
and
(14).
Calcula ed
acco ding
o
equa ion
(15).
F om
he
esul s
gi en
in
he
lowe
pa
o
Table
2
i
is
e iden
ha
he
closed
isome
o
Cu(A m)(PME)
is
an
impo an
species
wi h
a
o ma ion
deg ee
o
abou
75%.
Na u ally,
he
o -
ma ion
o
he
co esponding
isome
in ol ing
he
e he
oxygen
is
also
o
be
expec ed
(see
Fig.
1)
o
he
Cu(A m)(9,8aPMEA)
and
o
Cu(A m)(8,8aPMEA)
sys ems
and
we
designa e
i
as
Cu(A m)(PA) o.
Howe e ,
he
log
ACu/A m/P
A
alues
lis ed
in
column
4
o
Table
2
a e
by
abou
0.7
o
log
uni
la ge
o
he
la e
men ioned
complexes
han
o
he
Cu(A m)(PME)
species
and
his
mus
mean
ha
in
he
sys ems
wi h
9,8aPMEA
and
8,8aPMEA,
nex
o
Cu(A m)(PA)op
and
Cu(A m)(PA)l/o,
a
hi d
isome
mus
occu
which
in ol es
he
adenine
esidue.
The
ligands
9,8aPMEA
z-
and
8,8aPMEA
2-
o e
only
wo
such
possibili ies"
The
phosphona e-coo dina ed
Cu(A m)
2+
o ms
(i)
a
mac ochela e
wi h
one
o
he
ni ogens
o
he
adenine
esidue,
o
(ii)
an
in amolecula
s ack
be ween
he
a oma ic
ing
sys ems
o
Bpy/Phen
and
he
adenine
moie y.
Tha
he
i s
possibili y
is
no
o
ele ance
has
been
discussed
in
de ail
o
3’-deoxa-PMEA,
[21
and
he
same
a gumen s
also
apply
he e,
whe eas
o
he
second
possibili y
in ol ing
in amolecula
s acks,
many
examples
exis .
[2,28,30,31,39’40’43]
Hence,
he
addi ional
enhanced
complex
s abili y
may
be
a ibu ed
indeed
o
in amolecula
s ack
o ma ion.
Applica ion
o
space- illing
molecula
models
e eals
ha
he
adenine
esidue
o
he
9,8aPMEA
o
8,8aPMEA
ligands,
which
a e
equa o ially
chela ed
o
Cu(A m)
2+
ia
he
phospho-
ha e
g oup
and
he
e he
oxygen,
canno
s ack
well
wi h
he
a oma ic
ings
o
he
also
equa o ially
coo dina ed
A m;
a
subs an ial
and
s ain- ee
o e lap
o
he
a oma ic
sys ems
is
only
possible
i
he
e he
oxygen
is
no
equa o ially
coo dina ed
o
Cu
e+.
This
la e
si ua ion
is
depic ed
in
Figu e
3
o
9,8aPMEA.
Howe e ,
om
he
molecula
models
i
is
also
e iden
ha
an
apical
e he
oxygen
coo dina ion
and
simul aneous
s ack
o ma ion
would
be
compa ible
wi h
each
o he
in
he
Cu(A m)(PA)
species
wi h
PA
2-
9,8aPMEA
o
8,8aPMEA.
Hence,
he e
a e
a ious
in amole-
cula ly
s acked
Cu(A m)(PA)
species
possible
including
hose
wi h
somewha
di e en
o ien a ions
o
he
a oma ic
ings
owa d
each
o he .
As
he e
is
a
p esen
no
way
o
dis inguish
hese
a ious
isome s
and
con o me s
om
each
o he ,
we
ea
all
he
s acked
species
oge he
and
designa e
hem
as
Cu(A m)(PA)s
.
The
sum
o
he
abo e
easonings
hen
gi es
ise
o
he
equilib ium
scheme
(16),
whe e
he
pu e
phosphona e-coo dina ed
isome
is
designa ed
as
Cu(A m)(PA)op.
I
is
e iden
ha
he
uppe
b anch
o
his
equilib ium
scheme
e lec s
equilib ium
(13a)
while
he
lowe
b anch
e lec s
he
s acking
in e ac ion
(Fig.
3).
Cu(A m)(PA)c,o
Cu(A m)
2+
+
PA
2-
Cu(A m)(PA)op
Cu(A m)(PA).
(16)
319
Helmu
Sigel
e
al.
Te na y
Coppe (lI)
Complexes
in
Solu ion[I,2]
Fo med
wi h
8-Aza
De i a i es
o
he
An i i al
Nucleo ide
Analogue
9-[2-(Phosphonome hoxy)e hyl)Adenine(PMEA)
H2
NV7
x
/,OH
’
H2!
O
Figu e
3.
Ten a i e
and
simpli ied
s uc u e
o
a
Cu(Phen)(9,8aPMEA)
species
wi h
an
in amolecula
s ack.
The
o ien a ion
o
he
a oma ic
ings
may
a y
among
he
s acked
species;
such
a
s acked
complex
in
solu ion
should
no
be
conside ed
as
being
igid.
3.4.
E alua ion
o
he
In amolecula
Equilib ia
In ol ing
Th ee
Di e en
Cu(A m)(PA)
Species
Based
on
he
equilib ium
scheme
(16)
he
co esponding
equilib ium
cons an s
can
be
de ined
as
gi en
in
equa ions
(17)-(19):
log
"R2u(A m)(PA)opk’Cu(A m)
[Cu(A m)(PA)op]/([Cu(A m)2+]
[pA2-])
(17)
KI/o
[Cu(A m)(PA)cl/O]/[Cu(A m)(PA)op]
(18)
Kl/s
[Cu(A m)(PA)s ]/[Cu(A m)(PA)op]
(19)
Wi h
hese
de ini ions
he
expe imen ally
accessible
equilib ium
cons an
(4b)
can
be
e o mula ed
as
equa ion
(20):
[20a,31]
[Cu(A m)(PA)]
(4b)
(A m)(PA)
[Cu(A m)2+
[pA2_]
([Cu(A m)(PA)op]
+
[Cu(A m)(PA)cl/O]
+
[Cu(A m)(PA)s
])
[Cu(A m)
2+
[PA
2-
/(Cu(A m)
k-Cu(A m)
+
Kl/s "
"’Cu(A m)(PA)op
k,Cu(A m)
+
KI/O
"’Cu(A m)(PA)op
"xCu(A m)(PA)op
(20a)
(20b)
k’Cu(A m)
"’Cu(A m)(PA)op
(1
+
KI/0
+
Kl/s
)
(20c)
F om
he e
one
a i es
easily
[31
a
equa ion
(21),
whe e
Cu(A m)(PA)in / o
e e s
o
he
sum
o
all
he
species
wi h
an
in amolecula
in e ac ion:
Cu(A m)
Cu(A m)(PA)
10
Ig
ACu/A m/PA
(21
a)
K
Kl/ o
,Cu(g m)
"’Cu(A m)(PA)op
320
Me al
Based
D ugs
Vol.
7,
N .
6,
2000
[Cu(A m)(PA)in /
(21
b)
/’(i
Kl/ o
[Cu(A m)(PA)op
[Cu(A m)(PA)cl/O]
+
[Cu(A m)(PA)s ]
[Cu(A m)(PA)op
(21c)
KI/0
+
Ki/s
(2
d)
In
hose
ins ances
whe e
he
s acked
species
do
no
o m,
he
abo e
equa ions
educe
o
he
wo-
isome
p oblem
ea ed
in
equa ions
(13)
and
(14).
I
is
e iden
ha /I
Kl/ o
acco ding
o
equa-
ion
(21a)
can
be
calcula ed
ia
he
alues
log
ACu/A m/P
A
as
de ined
by
equa ion
(12)
and
lis ed
in
he
uppe
pa
o
column
4
in
Table
2.
Table
3.
ln amolecula
Equilib ium
Cons an s
o
he
Fo ma ion
o
he
Th ee
Di e en ly
S uc u ed
Cu(A m)(PA)
Species
Shown
in
he
Equilib ium
Scheme
(16),
Toge he
wi h
he
Pe cen ages
in
Which
These
Species
Occu
in
Aqueous
Solu ion
a
25
C
and
I
0.1
M
(NaNO3)
a
No.
Cu(A m)(PA)
log
ACu/Ann/l:,
A
g
’=
KI/ o
%Cu(A m)(PA)in / o
%Cu(A m)(PA)op
a
Cu(Bpy)(9,8aPMEA)
2a
Cu(Phen)(9,8aPMEA)
1.37
+
0.09
22.44
+
4.86
95.73
+
0.88
4.27
+
0.88
1.61
+
0.08
39.74
+
7.50
97.55
+/-
0.45
2.45
+
0.45
3a
Cu(Bpy)(8,8aPMEA)
1.32
+
0.09
19.89
+
4.33
4a
Cu(Phen)(8 SaPMEA)
1.61
+
0.09
39.74
+
8.44
No.
Cu(A m)(PA)
K
I/O
Ki/s
95.21
+
0.99
4.79
+
0.99
97.55
+
0.51
2.45
+/-
0.51
%Cu(A m)(PA)el/o
b
%Cu(A m)(PA)s
b
Cu(Bpy)(9,SaPMEA)
2.89
+/-
0.68
19.55
+
4.91
2b
Cu(Phen)(9,SaPMEA)
3.17
+/-
0.69
36.57
+/-
7.53
3b
Cu(Bpy)(8,SaPMEA)
2.89
+/-
0.68
17.00
+/-
4.38
4b
Cu(Phen)(8,8aPMEA)
3.17
+
0.69
36.57
+/-
8.47
12.3
+/-
3.9
83.4
+/-
4.0
7.8
+/-
2.2
89.8
+/-
2.2
13.8
+/-
4.3
81.4
+/-
4.4
7.8
+
2.3
89.8
+
2.4
a
The
alues
lis ed
in
he
hi d
column
o
he
uppe
pa
a e
om
he
ou h
column
in
he
uppe
pa
o
Table
2.
The
alues
o
K’
Ki/ o
ollow
om
eq.
(21a)
and
%Cu(A m)(PA)in / o
is
calcula ed
analogously
o
eq.
(15).
The
alues
gi en
in
he
six h
column
o
%Cu(A m)(PA)op
ollow
om
100
%Cu(A m)(PA)in / o .
The
cons an s
o
K o
in
column
3
o
he
lowe
pa
a e
om
column
5
in
he
lowe
pa
o
Table
2
( o
he
co esponding
jus i ica ion[
311
see
also
ex
in
Sec ion
3.4);
wi h
eq.
(21d)
and
he
now
known
alues
o
K’
and
KI/0
ha
o
Kl/s
may
be
calcula ed
(column
4
in
he
lowe
pa ).
All
e o
limi s
co espond
o
h ee
imes
he
s anda d
de ia ion
(3);
hey
we e
calcula ed
acco ding
o
he
e o
p opaga ion
a e
Gauss.
b
These
alues
we e
calcula ed
ia
eq.
(18)
wi h
K o
and
%Cu(A m)(PA)op.
The
alues
o
%Cu(A m)(PA)s
ollow
om
he
di e ence
%Cu(A m)(PA)in / o -
%Cu(A m)(PA)cl/o
(c .
eqs
(21b)
and
(2
c));
%Cu(A m)(PA)s
may
also
be
calcula ed
ia
eq.
(19)
wi h
K s
and
%Cu(A m)(PA)op.
The
esul s
a e
he
same
o
bo h
calcula ion
me hods
ye
he
e o
limi s
a e
unde s andably
la ge
o
he
second
me hod
(da a
no
shown).
The
esul ing
K
alues
a e
gi en
in
he
ou h
column
o
he
uppe
pa
o
Table
3
and
hey
allow
o
calcula e
he
concen a ions
o
he
open
isome s,
Cu(A m)(PA)op.
To
be
able
o
calcula e
he
o ma ion
deg ee
o
he
species
ha
o m
he
i e-membe ed
chela e
wi h
he
e he
oxygen,
i.e.
Cu(A m)(PA)c/O
(eq.
(18)),
we
made
he
jus i ied
assump ion
ha
Cu(A m)(PME)c
(Sec ion
3.3;
Table
2)
I31
and
Cu(A n)(PA)cl/O
ha e
he
same
s abili y,
i.e.
ha
he
equilib ium
cons an
K o
o
Cu(A m)(PA)cVO
equals
he
co esponding
alue
(=
K)
o
Cu(A m)(PME)c.
Knowledge
o
K
and
K/o
pe mi s
now
o
calcula e
K/s
by
using
equa ion
(21d)
and
hence
he
o ma ion
deg ee
o
he
Cu(A m)(PA)s
species.
Finally,
he
di e ence
be ween
100
and
he
sum
o
he
pe cen ages
o
Cu(A m)(PA)op
and
Cu(A n)(PA)c O
will,
o
cou se,
also
esul
in
%
Cu(A m)(PA)s
and
Ki/s .
The
esul s
o
hese
Calcula ions
a e
summa ized
in
he
lowe
pa
o
Table
3.
Conside ing
he
equilib ium
scheme
(16)
and
he
co esponding
esul s
summa ized
in
Table
3
se e al
conclusions
a e
e iden :
(i)
All
h ee
s uc u ally
di e en
species
a e
o med
in
app eciable
amoun s
in
he
Cu(Phen)(9,8aPMEA)
and
Cu(Phen)(8,SaPMEA)
sys ems.
(ii)
The
s acked
species
(Fig.
3)
clea ly
domina e,
eaching
o ma ion
deg ees
o
abou
80
o
90%.
(iii)
Consequen ly,
he
o ma ion
deg ee
o
he
i e- nembe ed
chela es
in ol ing
he
e he
oxygen
is
supp essed,
oughly
speaking
o
abou
10%,
compa ed
wi h
he
app oxima ely
75%
p esen
in
he
Cu(A n)(PME)
sys ems
(c
Table
2).
321