from The Journal of Physica1 Chemistry， 1982,お，1488.
Reprinted
Copyright
C 工982by the Ameriean Che面cal Socjety and reprinted by permission of tbe copyright owner
IIEi;1:￨
Anomalous Concenlrallon Depend●nce of the lnner-Sphere Hydratlon NumberChange
ln Aqueous EuC13 and GdC13 SOlullons
Ｈ．Ｋａｎｎｏ゛
ＷＱﾀﾞＱｓ７一昨．Ｍ幽6/四大，Wy9ず｡匍ｗ?
ar･d J. HIral●hl
鳩1齢r鳩1（恥脚1･必a/1）かC9如y蝕’jrxねS吻y−y ySIS加，7S4戯ぬ卯鴫JrbSylg∂S。匈WIr陶eSlyed;○咄泌Ｓリ，y卯ず;
jf7戸恥sぴα7y7;
F･lytsyj瓦ず甜匈
Raman
spectra of the aqu｡-ral･e earth k)。[Ln(H20),i]3゛(Ln゛+denotel
a rare earth ion，n − 8 and/or 9)in
gla朗y ral･eearth chloride solutions were obtained a8 a function of Mlt concentration. The population of ra:re
earth ions holding nine water
oleculea in theil･innerlnost hyd】･ation spheres increase with incl･easing 詰lt
concentration in EuC13 nd
GdC13 solutions. A qual峨ative discussion is givel for thia peeunx･ behavior.
I皿troduetion
Recent
Some
x-ray
difi･lctionl and Ramali2
with
aa3unlulated
tiess-6
of aqueous
studiel togeth一･
traa8port a.nd thermodytlamic
proper･
ra,eearth
electrolyte lolution8 have
EuC13
weighing
and
out
mer&Uy
water
methodi
Detans
of the
members
to eight for heavy ones. Purthermore，thisco ordination
number
cbange may be a major cause3･i･7of the
h7egula:rities
observed
for log.K(LK
is the 8tibiUty con-
same
According
to the ext411sivl wozk by Spedding
et al,,4.11
the
avellage hydration number
gy畠du畠Ilychanges 6･om ㎡ne
to
eight in the Nd9゛ to Tb3゛ region at ordina】･ytemper畠 tuzes.
0n the other hand， a＆掴tic change is obaerved in
七 the
7'l{gls8
tramition
tempersture}vs.Z
plot for raze
earth
peichlorate
solutions.6
and
several
a coonng
thermal
quenched
the
quenched
den(ytes
solution
to the
that
is きen8itive
found
(400-900
K/min)gave
change8
in these
portance
of the discretene腿 in solvent molecule● to solu tion
properties.
ln
this Letter, we zeport tlle anomslaus
behavia･ of the
totany
conoentration
dependexe
of the hydlatiQn 皿mberchangl
between
eilht and nine in aqueou麹EuCls
axld GdC13 so･
lutions:
the rse eaith ionsholding
nhle watar molecules
りbands
irltheizhmermost
with
increasing
ln the GdC13
were
the
across
solution
ofjR
Aqueousale
earth chloride soMjo㎜were
prepared by
di8soMng
thair oxides in excess HC1, sub舶quently
drying
under
an infz‘aredlamp， snd d皿utixlg with ditiUea wite￡
series.
were
obtained
(1)A.H･besasl
and F. H｡9p･ddilg,J.alm,j勿s.,70,2797,37S8
1979);7a,44211980)｡
− W￣ ㎜ ■ ■ ' ■￣
叫!!,!C･zl!!o
ad
J. Hizailhi.
aey7i｡PSys,
敗馬具Speddi㎎.M,J.Pa;al，adiS.0.λyes.
244a(1966).
12s4
11g
a965}.
J. Pliys， aik,￣i;
(り瓦･芦･_!lpeddilg.P.l｀.Cden,adA.Hab･sdxuss.J.j゛1りl.als一一
7S.110611974).
(10)S.P.Sinh●,lfe1.CZzj・.jlcま,2，S8，1978(1976)，
(11)(a)F.H.Sp｡ddj.ng
ald J. A.Rsd.J.昂y･，asl.，7S，1435
A.R･rd.J.J¥t:yl.，
胆丿叫ぞ･1!･jsp￥d1･g
uld
帥74);(b)F.H.SpMdilll,J.P.Wajtgs,and
J. L,Baiey,J.a｡,，j恥S.
ZJaia. 20. 189， 4a8(1975);(c)F.H.
Sp●ddilg， J，A.R鯵d，ud
A. Ha･
benschuas.J,jｺ?iys.Cll･,n.，81，106911977)｡
the
Alh,L
results
in glassy
moles
and
on
accu;rate
Raman
hydration
one
From
with
x-ray
number
the
state
ghls8
that
diffraction
that
tl｀an'
a value
8tate
studies
there
of
are
two
[Ln(H20)9]s゛
(JR＝24)and
concentration
between
(12)H.Raw恥n,“ln(qdcG1朗s
Formi4
Londo71，1967，Chapters l and 2.
(13)H.Kanno
and J，HIrai8hj，J.Ra,ua
state is
a Uquid
the l･esults shown
know
EuCI3
change
8pectrum
glassy
for the liquid
iolls･ ゜"lely
for the
8olutions
assignment
Rarnan
i8 the
results
advantage
frequency
to 79.
glassy
chloride
of salt)。
aqueous
it is certain
we
of the
for the
solution
important
near
the
earth
for theR＝20
The
Spedding,1
radius
except
rare
at ol: high肘thsll
e“th
ionic
of water/moles
state
together
吻(包oり9yo-r811e
The
of the
state, renecting
very
(i･l is the
aquo-Ilare
flleq｀lellcy chs"ge
a nonequinbrium
Habenschuss
of the
rate
structural
of the
gla息sy state.2.1s A
[Ln(H20)813゛ions,in
(R＝20)solutions｡
31
so-
cooling
i,l results
in the
l
gla88y
s＆mple
sman
vibl･ation
measurements
for a glassy
F4μΓe
a
ljlba:nd i8 on21y pos8n)leinthe
at a temperature
in
the
to 【Ln･
the
solutioM.
sitioil telllpel｀atuie(7g).Thus
obtained
￡･letJS,S53(1960)
al).{l.R.ChospjD
− ￣ − − 〃
(3)G.R.Ch｡DDin
sd
snd
A. J.G踏鰹･･,j{･sl.Cial.，4
J.GzafSo.jn･rl.Cajlyl.｡4.12s4
in
diagram.
aりl cel'taill tempei8tlfl'e
（
changes
the ･l result8
state i8 that
solution
of course
of the
is 唸e
in the
glas8y
for the
rate
summarized
the
solution,
of the wak
ions
cooling
only
solution
to ascertain
㎞)in
a funetion
＝24(jR
included
in the
sample
made
earth
ioll to show
ofca.rl･ying out Raman
Seetion
is de･
to a glassy
gla闘,12 Therefore，
were
a rare
stretching
eaith
solutions
rates
8tate
state
same
aqueous
earthion[Ln(H20),,]34')as
GdCI3
the
Discussion
displays
8ymmetric
of吟el戸e
quenched
a Uquid
l･ise to
gla88y
by
e弱entiany
ratio of 【Ln(馬O)9ls゛
(H20)8rios(Ln3゛
1ution3.1Ve
were
the
coohg
and
made
a glass is in a nonequi･
of the
on
at (ほferent
whether
from
histories
measurement8
dration
ExperimentaI
rate
by
crystals
solution8
meagurements
nnal
on
just
of com-
results｡
state， the
pendent
l
coordination spberes increase in number
salt concentration
㎞solution.
Raman
same
quenched
librium
and
of the im-
the
that
As
F4ure
solution， indicative
give
made
amount8
ol･GdCI3.6H20
connrming
reported.2
Results
of ions i
wel･e 幽o
required
as previously
The
significance of tllese observation息is that solution
properties
ale greatly dependent
Qn the inner-sphere
by･
number
the
EuC1316馬O
thereby
different
state
solution8
mixing
avanable
dis闘ed
cleally
shown that the inner･sphere
hydration number
of
rare
earth ions changes
fyom nine lk}r light rare ealth
・stant)s.Z(atx)mjcnumber)or
y･(ionicr●dius)ploll,which
a:re c匯Iled 8uch thinp
a圓“tetrad",8“double-double',9or
“inclined
W"1o effects.
GdCI3
and
and
Gd(馬
dependence
eight
and
System', Academjc
nine
h,ss，
Sped,･(Mc.，9.85(1980〉.
Letters
77?θ必tjms/
Ｃｅ
Lj
ＦＴ
Ｎｄ
Ｐ罰
Eu
Tb
Ｔ●
河O
沚Vy此a/aer吻吟，吻り眠尚.9，79∂2
1489
Lu
０ ０
１P
n
ＱＪ
z
_ｉ３／１ｊｌＵＳ
てbcり
R・IS
S●C13
∧
寵●26
７
０
３
ＭＶＭ￥１
351
1,05
１,ﾛﾛ
ﾖ側IC
Ojo
0.95
0､a5
RADIUs
o iりaREEsTM 101 / i
Fllur●i. Fr●quendes ･舗le ijlbanillorihe lLn(HIO)l]s゛lons (rl
°a. 9)ln glassy rare earth chkl｀ld●
s olutlon●.
I I
哩1410 390 370
39D 370 350 330
RAMAM SH]FI
/CM￣1
咋:ぷこ流:口吻7認にr¨cl･
tt雲丿勁迄ごs諧な:な乙
coordjination number
of Eua゛ iom㎞3.23
M
aqueous
EuC4
旨詣な詰二次昌芯;?忿が
に鴬だこ惣雷昌宏酋tこ惣
ｺﾞ酋ﾋ雷ぷ旨昌ごZた
1
｡
次ご雲旨ぼ忿1昌む雲たご(こ
ご1ご惣忿忿次回昌之7昌1こ
worthwhile
to further examine
hy(1ration numbel, change
忿:智之tlご亡酋ご謔･な
り0 410 390 370 350
mented
experimental
ｺﾞ痙燐勁酋迦だ昌之ごこ
QIG 伺0 370 350 330ヽ･-
the ana】ogy between
in rare earth aquo
the
ions and the
data for the latter casel“19 and the
ＲＡＭＡＮ ＳＨＩＦＩ／ｃＭ'￨
＼
FISぽ●2.Varl畠110n
Df the
ｈｅりband
l,1band
EuCls and GdC13 solullons.
in
the
Figure
glassy
2.
corre8ponds
∼394
and
molt
and
ExarninaUon
of the EuC!a
with
EuCls
sddon
in
solutioD昌匯re
of Figure
the
Raman
salt
ln glassy
9lassy
shown
in
2 show鳥也atinthec醵e
peak
disappes･s
ions， increasesbl
concentration
euri)piumions
when
may
be interpreted
by the
R
while
＝15.This
are in the form
comment
tl･ation dependence
must be made
of the SmC13
here about the concen，
and TbCI3 solutions. As
忿ご巴渚ばrた忿こ忿ご
at ∼369cm'1,which
intensity
the
peak
indicates
fな忿こなな芯i営次ここtご
at
al-l， corrspondi㎎to[Eu{H20}a】゜゛iom,d･icxlasee
almost
cha:nge in ra:re ea】･thions
anだ2j;･
GdCIB
to [Eu(H20)91s゛
an increase
wlth satt
salt concer11ralon
concer霜atlon
忿昔瓢iご燐≧堂な昌旭
that
of
the equinbrium
reaction between
eight and
nine coordi-
glassy EuC13 solution of R ＝15.
gadonnium
ions exist in the for
nation8 is displa｡ed to one side in SmC13 and TbC13 sohl･
tions at low temperatures,
at leastjn
the glas8･forming
glassy GdC13 &olution of j? ＝25,the
appears ln
in the
R ＝20 8olution
and
aljpuars
ule 几＝zU
801ul;10n an(IDeconleS
niore (10n11nant than the lGd(H20)813゛
species in the glassy j? ＝15
芯ｺ剽;臨なご口たt忿た昌
solution，A:n allomal(m
point of these observations is that
the ral･eearth ions having the lal･gerinner,sphere hydJ･ation
ｺﾞt忿乙旨応ｺご忿訟ゴこ:?nation
ln the R ＝15 solution, there a:re15 water
numbel･(Le.，9)increase
in number
with a decrea騎in water
content in the solutions. A 8traightforwalld conclu息ion
巴こ;応ご忿こ雲仙ごご旨ば
from the expelimental
results is that, when sufficient water
molecules＆re
not available to form a complete
second
hydration
sphere ajround a Eu3゛ or Gd3゛ ion，the coordination number
of nine becomes
mol･e stable than eight at
沿ぱ昌諮げ幄燃ほU昌‰
k)w temperatu.res.This
anomalous
behavior is 侭l apparent
reversal of what the law of mas8 action teU8‘us when we
coMider
the reactionexpressed
in a conventional
wayj.e｡
[Ln(H20)913ﾊ==[Ln(H20)8134'＋H20
Unfortunately
we
cannot
at present
がve a c!ear-cut ex･
molecules
for
｡｡佃copy"，
≒混ta忿ぶ･ぼ昌
,昌‰
Rzrg
ys.aem｡66.57(1962);
Appl. Clie,71.,6,23(1963)｡
昌t C‘ A Angen “d DI M‘ Giu°I J. 7″゛o゛ぎ.M゛cl.
Clle゛'1Z9゛2243
(l
問昌1昌だ聚迦なぷ忿こ酋緊2昌:
tごだ昌旨tむ胎;7r
s°1'゛'･
c. ｀‘゛･｀j･･
1490
weakly
hy＆ogen
bonded
to other
water
molecules).
Among
wate】･molecu!es trapped in these three configurations，thewaterm幽cules
in the nrst envbnment(type
l)al･e con3idered to be the most stable at low temperatures.Next
in stability a】･ethose in the second
ration and the mo倦t un8table
configuration｡
ones
co
｢igu-
are tho8e in the third
From
x･ray diffraction studies,uo it is now firmly estabnshed that even in these concentratsd chloride solutionj
○
iND
CR＝15−25)the
earth ion is made
Mhttp://wｗw.ε
麟回ｌ
F19u｢●4. Schematlc
two-dimenslonal presentatlon of a ooncentrated
aqueous
rarg earth chbride s4)lutlon:(A)all rare earlh lons are elght
c4xydlnated;(B)allrlre
sarth ions are nile cooai姻ed.Some
of 廿1●
type 3 water rrK)￨●cules(closed small clrcles)ln the A solution enter
l陶the p岫ry騨白呻聊s
ln the B so ､o喝軸t吻becorr啼
(rK)｢e stable. Comparlson
of the two solu110ns shows that the molar
yolume of the B solutk)n ls 8maller tharl that foi‘
the A solutlon，wNch
means
that more eff●ctlve approaches
between
catjons and anlons
are posslble in the B sQlutlon.
shen
of a
r＆re
eajrth
molecules
to share
and哨ree
chloride
molecules
may
be
theae
intrinsic
of the
te仕ahedral
earth
earth
ion
where
catioil
lol･ “
＼
for the
hydration
chloride
fact
ion
water
molecules
in
mind，
anom＆lous
number
water
solutions,
structure
and
configurations: the
where
a watel･ molecule
chloride
a water
or a chloride
is one
earth
of 8olvent
thi8
water
and
where
rare
water
a
con･
cha.nge
as follows｡
concentrated
configuration
rare
6−7
of water
With
exphmation
typical
is one
hydrated
sharing
anions.
dependence
given
only
scarcity
qualitative
centration
ln
and
remain
each
ions.The
extensive
cations
tentative，
three
between
imposea
between
ion， there
a
water
anioll
ions
(a type
molecule
ion
(a type
i8 no molヽe
in8tead
there
first one
to both
l water);the
2 water);and
c(x)rdinates
second
to either
the
a rare
the salt concentration
increases， some water molecules
outside of the inner一息here hydration ghens become
a kind
of dangling state due to a lack of water molecules and the
resulting breakdown
of the second hyd:ration spheres.
Therefore，maximizatk)n
of the type l water molecules or
minimization
of the type 3 water molecules， which means
that some of these danghg
wa細,molecules(蛸冶3
water
molecules)enter
into the imlermo8t
hydration spheres， is
the most stable state for the sokions
at low temperatuJ･es，
Ile8ulting in the increa8e of nine-coordinated
rare earth
ions.This
situation may be weU exemplified schematicajly
in Figure 4 in which type 3 water molecules in the A solution al･e shown to enter into the innermost
hydration
sphere8 in the B solution to become
more stable｡
At the moment
the explanation is rathenpeculative
and
itis evidenUhat
cloaer examinations
are needed
before
we get a fuU quantitative acoount of the behavior. More
extensive wolrk is in prog7ess and win be reported 8hortly｡
Acho 歹dgmeM.
We al･ethankful
Angd
for hi8 valuable suggeetk)n3.This
a3sisted by a Grant4n-aid
for Sdantifk
Ministry of Education。
to PI･ofessor C. A，
wol･k ws partja恥
Re8earch from 函3
third
to neithel･a
3 ｀゛tel･ ゜olecule･jt
around
a r＆re
molecules.
As
are
is the
coordinates
coordinates
molecule
(8 type
thge
innermost
coordination
up exclusively of water
l“y
be
99}(!!),¥･!･･j吻legdDJ･W呻，J.Am.aa･.SQc･，
98. 4424
(1976);(b)L.＆Smith,Jr,,aild
D. L,Wertz,J.MQri.7V・1.alm.,39，
95(1977);(c)M.
L. Steelj and D. L.Wertz,Z,z｡,i.Cみ4,。｡，16,1225(1977)｡
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