na u e communica ions
A icle h ps://doi.o g/10.1038/s41467-022-32178-3
Selec i e sepa a ion o ligh a e-ea h ele-
men s by sup amolecula encapsula ion and
p ecipi a ion
Joseph G. O’Connell-Danes
1
, B yne T. Ngwenya
2
,Ca oleA.Mo ison
1
&
Jason B. Lo e
1
Sup amolecula chemical s a egies o Ra e Ea h (RE) elemen sepa a ions
a e eme ging which ampli y he small changes in p ope ies ac oss he se ies
o bias selec i i y in ex ac ion o p ecipi a ion. These ad ances a e impo an
as he REs a e c ucial o mode n echnologies ye hei ex ac ion, sepa a ion,
and ecycling using con en ional echniques emain challenging. We epo
he e a p e-o ganised iamidoa ene pla o m which, unde acidic, biphasic
condi ions, uniquely and selec i ely p ecipi a es ligh RE ni a ome ala es as
sup amolecula capsules. The capsules exhibi bo h in a- and in e molecula
hyd ogen bonds ha dic a e selec i i y, p omo e p ecipi a ion, and acili a e
he s aigh o wa d elease o he RE and ecycling o he ecep o . This wo k
p o ides a sel -assembly ou e o me al sepa a ions ha exploi s size and
shape complemen a i y and has he po en ial o in eg a e in o con en ional
p ocesses due o i s compa ibili y wi h acidic me al eed s eams.
Sup amolecula chemis y concep s such as sel -assembly, non-
co alen in e ac ions (NCIs), and p e-o ganisa ion a e inc easingly
e iden in hyd ome allu gical ex ac ion and ecycling p ocesses1–4.
These concep s a e also ele an o new p ocedu es ha sepa a e he
a e-ea h (RE) elemen s which a e c i ical elemen s and c ucial o
mode n, sus ainable, and g een echnologies5–10. While diglycolamide
ligands a e well-known hea y RE ex ac an s, i was only ecen ly
app ecia ed ha NCIs be ween ni a e coun e -anions and wa e
clus e s wi hin a e oil-kno o ganic s uc u e a e esponsible o
selec i i y11. Fu he mo e, s uc u ally p e-o ganised diglycolamide-
deco a ed eso cina enes ex ac ed selec i ely hea y REs om ni ic
acid, epo edly o ming bowl-shaped, sol a ed species in he o ganic
phase12. Mul i alency p inciples we e exploi ed in he a ou able iso-
la ion o hea y RE me al-o ganic amewo k (MOF) s uc u es o
olsalazine ligands13. Simila ly, low-coo dina e, hea y RE MOFs we e
o med selec i ely om hiophene-dica boxyla es and u ea sol en s
depending on sol en and anion s uc u e-di ec ing e ec s14.Sig-
nifican ly, he sel -assembly o e ahed al RE
4
(L)
4
cages showed a sel -
so ing, mul i alence mechanism in o ganic sol en s ha a ou ed
hea y o e ligh RE cages15. Selec i e p ecipi a ion o RE complexes
was also seen om o ganic o mildly acidic solu ions using ipodal
ligands ha bias monome -dime solu ion equilib ia, o e ing sig-
nifican enhancemen o sepa a ion ac o s (SFs) be ween selec ed
pai s o REs, o example dysp osium o e neodymium16,17.
These ad ances ely on he coo dina ion o ligands o he RE,
he eby dic a ing selec i i y owa ds he hea y REs due o hei smalle
ionic adii and enhanced Lewis acidi y. In con as , ionic liquids
ha e been shown o p e e en ially ex ac he ligh REs as dynamic
sup amolecula ni a ome ala e/ionic liquid assemblies, albei om
concen a ed-ni a eaqueousphases andno om heacidicsolu ions
necessa y o RE leaching18–20. In o de o a ge he sepa a ion o ligh
REs, he o ma ion o RE me ala es o anion- anspo mechanisms is
clea ly ad an ageous. Howe e , RE me ala es a e no o med in aqu-
eous phases21, and hei specia ion in o ganic phases is ill-defined and
ex emely di ficul o con ol. Ne e heless, p e-o ganised ecep o s
can p o ide sup amolecula hos en i onmen s o hese complex
anion gues s. A ipodal hexapy idyl iazine was eac ed wi h RE
chlo ides and ni a es o o m hos :gues complexes o RE chlo ido-
and ni a ome ala es; a 1:1 bowl-shaped en i onmen o chlo ide was
epo ed whe eas a comple ely encapsula ed 1:2 complex o med wi h
Recei ed: 5 May 2022
Accep ed: 20 July 2022
Check o upda es
1
EaS CHEM School o Chemis y, Uni e si y o Edinbu gh, Edinbu gh EH9 3FJ, UK.
2
School o Geosciences, Uni e si y o Edinbu gh, Edinbu gh EH9 3FE, UK.
e-mail: [email p o ec ed]
Na u e Communica ions | (2022) 13:4497 1
1234567890():,;
1234567890():,;
ni a e22,23.Sup amolecula π-anion in e ac ions we e e iden along
wi h elec os a ic in e ac ions due o p o ona ion o he ecep o , bu
poo ex ac ion and negligible selec i i y was seen om aqueous ni ic
acid. Simila ly, a p e-o ganised a ene/quinoline-e he ipodal ecep-
o o med a 1:1 hos :gues complex wi h RE(NO
3
)
3
(MeOH)
3
in
me hanol h ough e he -alcohol hyd ogen bonding in e ac ions24. P e-
o ganised hexa-subs i u ed a ene pla o ms a e well-known o sel -
assemble in o sup amolecula ennis-ball s uc u es25,26,andcan
encapsula e simple anions such as fluo ide, ni a e, and a sena e27–29.
We an icipa ed ha hexa-subs i u ed a enes wi h amide appen-
dages would ha e he po en ial o o m capsula compounds wi h RE
me ala es and ha his would be a ou ed due o he amide N-H
hyd ogen bonding in e io along wi h amide O-a om si es o
p o ona ion30. He e we show ha an amide- unc ionalised hexa-sub-
s i u ed a ene ac s as a highly selec i e p ecipi an o ligh RE ele-
men s om 4–8M ni ic acid h ough he o ma ion o RE
ni a ome ala e sup amolecula capsules.
Resul s
Lan hanum capsule p ecipi a ion and cha ac e isa ion
The ipodal amido-a ene L (Fig. 1) was p epa ed and while only pa -
ially soluble in oluene and insoluble in ni ic acid, dissol es in o he
aqueous phase o a biphasic mix u e o oluene and 8 M HNO
3
. Addi-
ion o La(NO
3
)
3
o his biphasic mix u e wi h igo ous s i ing o e
24 h causes 1-La o p ecipi a e a he in e ace (Fig. 1). Analysis o bo h
aqueous and o ganic phases by ICP-MS shows ha comple e p e-
cipi a ion o 1-La occu s.
The La-con aining p ecipi a e 1-La was isola ed by fil a ion and
slu ied in ace oni ile, om which c ys als o med o e 4 mon hs. The
X- ay c ys al s uc u e displays he highly symme ical sup amolecula
capsule [{La(NO
3
)
6
}⊂(H
3
L
2
)]
n
in which he hexani a ome ala e
La(NO
3
)
6
3−is encapsula ed by wo p o ona ed amido-a ene ecep o s
(Fig. 2). These ecep o s adop ababab configu a ions simila o hose
seen o “flexi-ball”and ela ed sup amolecula s uc u es de i ed
om s a ically gea ed, hexa-alkyla ene pla o ms26,31. The La(NO
3
)
6
3−
anion is wel e coo dina e wi h he ni a es asymme ically κ2-bound
(La1-O4 = 2.6593(17) Å, La1-O2 = 2.6370(17) Å). The capsula s uc u e
is ein o ced by in amolecula hyd ogen bonding be ween he amide
N-H and a single ni a o O-a om ha is coo dina ed o La (N1(H)---
O2= 2.814(3) Å) and a e shown by NCI calcula ions o be he dominan
in a-capsule a ac ion (see Supplemen a y In o ma ion Fig. 1). These
in e ac ions esul in he o ien a ion o he pseudo-oc ahed al
ni a ome ala e such ha he apical ni a e oxygen a om O3 occupies
space be ween he in e digi a ing a ms o he ipodal ecep o s. As
such, he s uc u e o he in e io o he capsule complemen s ha o
he hexani a ome ala e like hose seen in he encapsula ion o me a-
la es by sel -assembled coo dina ion cages and unc ional molecula
flasks32–36. Each amide oxygen o each ecep o L is ½ p o ona ed,
esul ing in a o al o h ee p o ons pe capsule which balances he
cha ge o he ianionic me ala e. This esul s in a polyme ic, solid-
s a e s uc u e h ough hyd ogen bonding be ween p o ona ed amide
oxygen a oms o adjacen molecules (O1(H)---O1’=2.439(3)Å)(see he
Supplemen a y In o ma ion Fig. 2 o he ex ended s uc u e). These
sho in e -capsule hyd ogen bonds a e shown by quan um heo y
a oms in molecules (QTAIM)37 analysis o he p omolecula elec on
densi y o he DFT op imised s uc u e o be abou 3.5 imes s onge
han he in a-capsule N-H---O bonds (see Supplemen a y In o ma ion
Fig. 3). Thus, i is e iden ha he p o ona ed ecep o p esen s a
geome y ha complimen s he hexani a ome ala e h ough e ficien
in a-capsule hyd ogen bonding and is also designed o p esen s ong
in e -capsule in e ac ions ha ul ima ely leads o p ecipi a ion.
Powde X- ay di ac ion analysis o he bulk p ecipi a e o 1-La
shows excellen co ela ion wi h he calcula ed pa e n de i ed om
he single-c ys al s uc u e and confi ms ha he bulk p ecipi a e and
single-c ys als a e s uc u ally cohe en (Supplemen a y In o ma ion
Figs. 4 and 5). The Raman spec um o 1-La shows abso p ions a 1055
and 1039 cm−1assigned o La-O
2
(NO) asymme ic and symme ic
s e ches (Supplemen a y In o ma ion Fig. 6). E idence o p o ona ion
a he ca bonyl oxygen a om is p o ided by a shi in he C=O s e ch
om 1638 cm−1in L o 1576 cm−1in 1-La and he IR spec um shows
abso p ions a 3223 and 3069 cm−1 o hyd ogen-bonded N-H and O-H
g oups ha a e shi ed om hose in L (ν(N-H) 3297 cm−1) (Supple-
men a y In o ma ion Fig. 7). Mass spec a (ESI/MALDI/LDI) show only
ions ela ed o “hal -capsule”compounds such as La(NO
3
)
2
(L)+
(m/z= 932.46). The limi ed solubili y o 1-La in ace oni ile also inhibi s
he eco ding o any use ul NMR spec a. I is e iden om he accu-
mula ed da a ha he bulk ma e ial ha p ecipi a es om he biphasic
mix u e is capsula in na u e.
Selec i e a e-ea h p ecipi a ion
Significan ly, RE p ecipi a ions by L om mixed-me al RE(NO)
3
solu-
ionsa e selec i e. P ecipi a ion o La o Lu (excluding Pm)wi h excess
L om8MHNO
3
/ oluene ollows a sigmoidal end, wi h excellen
up ake o La o Nd (95–70%) compa ed wi h negligible/ze o up ake o
Fig. 1 | Encapsula ion and p ecipi a ion o he a e-ea h elemen s (REs). a The
ipodal amido-a ene L used in his s udy, b he capsula hexani a ome ala e
complex, [{La(κ2-NO
3
)
6
}⊂(H
3
L
2
)]
n
1-La,ca schema ic o he p ecipi a ion o a e-
ea hs by L om a biphasic ni ic acid/ oluene mix u es and i s s ipping using a
pola p o ic sol en such as wa e .
A icle h ps://doi.o g/10.1038/s41467-022-32178-3
Na u e Communica ions | (2022) 13:4497 2
Eu o Lu (<10–0%) (Fig.3). To ou knowledge, his is he fi s exampleo
selec i e me al sepa a ion by sup amolecula encapsula ion o any
me ala e, no jus he REs. The s uc u es o he p ecipi a es 1-P and
1-Nd we ee alua ed by PXRDand showa e y simila pa e n o ha o
1-La,albei wi hshi ed2θ alues as expec ed o smalle uni cell
pa ame e s o capsula complexes o hese me als (Supplemen-
a y Fig. 8).
I is ins uc i e o use (pseudo) SF alues o con ex ualise he
selec i i y in p ecipi a ione en hough hey a e no mally de i ed om
dis ibu ion coe ficien s o he pa i ioning o me als be ween wo
sol en phases (Fig. 4). The SF
La/RE
(whe e RE = Ce-Eu) a 298 K inc ease
d ama icallyin magni ude ac oss he se ies; no SFs we e calcula ed o
elemen s beyond Eu as p ecipi a ion is ze owi hin expe imen al e o .
While SFs o La/Ce, La/P , and La/Nd a e simila o he s a e-o - he-a
phospho us acids in sol en ex ac ion expe imen s38, hose in ol ing
La/Sm and onwa ds a e la ge , om 63 o La/Sm o 248 o La/Eu. As
noDyp ecipi a ionisseen heSF
Nd/Dy
is e ec i ely infini e and
he e o e g ea ly exceeds hose seen in sepa a ions using s a e-o - he-
a ipodal hyd oxypy idone (SF
Dy/Nd
213)17 and bo a e (SF
Nd/Dy
986)
p ecipi an s39.
E ec o a iables on p ecipi a ion and sepa a ion
The concen a ion o ni ic acid is an impo an ac o o bo h he
ex en and selec i i y o p ecipi a ion (Fig. 3). No o li le p ecipi a ion
is seen o concen a ions below 4 M, while inc easing om 6 o 8 M
HNO
3
inc eases p ecipi a ion o he ligh REs wi h a sligh shi o he
igh o he se ies. Inc easing he concen a ions o ni ic acid o 10 and
12 M causes a u he shi o he igh o he RE se ies bu hese da a
a e comp omised due o significan ni a ion o he oluene sol en
(Supplemen a y In o ma ion Fig. 9). This enhanced p ecipi a ion
beha iou seen a high acid concen a ions is unusual o anion
anspo and p ecipi a ion mechanisms o which acid/anion ans-
po is usually compe i i e and inhibi s me al up ake. A 4 M HNO
3
,
while p ecipi a ion is lowe in ex en (64% La s. 94% a 8 M HNO
3
)a
ma ked shi in SFs is e iden , becoming infini e beyond Sm (SF
La/Sm
180, SF
La/Nd
7).
The e ec o M:M’ a io on he amoun and selec i i y o p e-
cipi a ion was p obed o h ee bina y mix u es: La/Nd; La/Dy; Nd/Dy
a 5:1; 1:1; 1:5 a ios (Supplemen a y In o ma ion Fig. 10). While he
selec i i y is essen ially unchanged by he p esence o an excess o
me al, he o e all p ecipi a ion is enhanced a highe absolu e me al
concen a ions. Fu he mo e, a me al concen a ions a ac o o en
lowe , negligible p ecipi a ion is seen whe eas a a ac o o en highe
he la ge quan i y o p ecipi a e p oduced esul s in significan
Fig. 2 | X- ayc ys al s uc u e and DFT NCI analysis o 1-La [{La(NO
3
)
6
}⊂(H
3
L
2
)]
n
.
aX- ay c ys al s uc u e ( op-down iew). Fo cla i y, all hyd ogen a oms excep
hose in ol ed in hyd ogen bonding and a diso de componen o he amide a m
a e omi ed (whe e shown, he mal displacemen ellipsoids a e d awn a 50%
p obabili y). N-H and O-H hyd ogen a oms we e loca ed in he di e ence Fou ie
map and (O1)H is 50% occupied on a c ys allog aphic special posi ion. A om col-
ou s: La = g een; oxygen = ed; ni ogen = blue; ca bon = sil e ; hyd ogen= g ey.
bDFT s uc u e showing non-co alen in e ac ions. NCI a ac i e hyd ogen bond
in e ac ions a e ep esen ed as blue disks. A om colou s: La = g een; oxygen= ed;
ni ogen = blue; ca bon = sil e ; hyd ogen= g ey.
Fig. 3 | P ecipi a ion o REs by he ipodal amido-a ene L. P ecipi a ion a ising
om a 0.0025M mixed-RE solu ion in 2 o 8 M HNO
3
/ oluene equal- olume
biphasic mix u e a e he addi ion o 3.5 mmol L (5- old excess L ela i e o me al)
a 298 K.
Fig. 4 | Sepa a ion ac o s (SFs) be ween REs (La-Eu) on p ecipi a ion by L.
De e mined om p ecipi a ions a ising om a 0.0025 M mixed-me al solu ion in
8 M HNO
3
/ oluene equal- olume biphasic mix u e a e he addi ion o 3.5mmolL
(5- old excess L ela i e o me al) a 298K. Sepa a ion ac o s a e calcula ed om
pseudo-dis ibu ion a ios, whe e he me al los om he aqueous phase ( ela i e
o he eed solu ion) is assumed o be en i ely con ained in he p ecipi a e.
A icle h ps://doi.o g/10.1038/s41467-022-32178-3
Na u e Communica ions | (2022) 13:4497 3
en ainmen o he aqueous phase and e oneous concen a ion
measu emen s.
Va ying he M:L a io in a La single-me al biphasic mix u e esul s
in an inc ease in p ecipi a ion up o ca. wo equi alen s o L, a e
which li le inc ease in p ecipi a ion quan i y is seen (Supplemen a y
In o ma ion Fig. 11); his suppo s he obse ed o mula ion o he
capsula complex.
The p esence and iden i y o he o ganic phase is c ucial. The
ipodal amide L is insoluble in HNO
3
a he concen a ions in es i-
ga ed and only dissol es in biphasic mix u es wi h oluene o hep ane;
Ldissol esinchlo o o mbu ,in hiscase, emainsunp o ona edin he
o ganic phase. Dissolu ion o L in o 8 M HNO
3
unde biphasic condi-
ions, ollowed by emo al o he oluene phase and addi ion o
La(NO
3
)
3
, esul s in no p ecipi a ion o 1-La. While he o ganic phaseis
equisi e o p ecipi a ion, he o ganic/aqueous (o/a) a io can be e y
low, wi h he ex en o p ecipi a ion o 1-La simila o o/a a ios om
0.05 (74%) o 1.0 (81%) along wi h li le a ia ion in RE selec i i y
be ween 1-RE (RE = La, Nd, Dy; Supplemen a y In o ma ion Fig. 12).
This necessi y o a non-pola o ganic phase hin s ha capsule o -
ma ion occu s a an oil-wa e in e ace simila o ha seen o sup a-
molecula mic ocapsules40. Also, he p e alence o pen a-
ni a ome ala e s uc u es o he hea y REs sugges s ha s uc u al
complemen a i y be ween he p e-o ganised hos amewo k and
gues ni a ome ala es in he sup amolecula assembly p ocess is
impo an o selec i i y. The o ma ion o highe -o de ni a ome a-
la es is mo e likely in a non-pola phase18, so ein o cing he impo -
ance o he biphasic assembly p ocess.
Finally, he s ipping o he me al om 1-La and he ecycling o L
is s aigh o wa d. The 1-La p ecipi a e is isola ed by fil a ion and
washed wi h HNO
3
, emo ing any unp ecipi a ed REs. Subsequen
dissolu iono hesolidsina p o icsol en suchasme hanolcauses he
capsules o up u e and, on addi ion o wa e , L p ecipi a es om
solu ion, lea ing a supe na an o La(NO
3
)
3
in me hanolic HNO
3
.
Ligand L can be ecycled o u he use (Supplemen a y In o ma ion
Fig. 13). This ease o s ipping he RE and ecycling o L eflec s bo h
hesup amolecula na u eo hebondingin1-RE and heweakbasici y
o he amide g oups, bo h o which a e in insic o he ecep o design.
The selec i i y o he ligh REs shown by his ecep o , i s abili y
o unc ion unde highly acidic condi ions, and he ease o s ipping
he RE wi h ecycling o he ecep o may con ibu e o he de elop-
men o a use ul RE sepa a ions p ocess. Howe e , hese aspec s mus
be balanced by he ela i ely complex syn hesis o he ecep o , he
po en ial di ficul y in designing a con inuous sepa a ion p ocess
in ol ing p ecipi a ion, and he a iabili y o sou ce ma e ials such as
RE o es and magne s.
Me hods
All sol en s and eagen s we e used as ecei ed om Sigma-Ald ich,
Fishe Scien ific UK, Al a Aesa , Ac os O ganics o VWR In e na ional.
Deionised wa e was ob ained om a MilliQ pu ifica ion sys em.
Syn hesis o ipodal amidoa ene (L)
Nea 3,5,5- ime hylhexanoyl chlo ide (5.64 ml, 29.7 mmol, 3.3 equi .)
was added d opwise o a solu ion o 1,3,5- is(aminome hyl)-2,4,6-
ie hylbenzene (2.41 g, 9.6 mmol) in a mix u e o THF (200 ml) and
NE
3
(4.8 ml). The mix u e was s i ed a oom empe a u e o 24 h
a e which he p ecipi a e was fil e ed and he fil a e e apo a ed
unde educed p essu e o gi e an o -whi e solid. Rec ys allisa ion
om oluene ga e 4.0g, 62% o L as a colou less solid: 1HNMR
(601 MHz, chlo o o m-d)δ5.21 ( , J=4.5Hz, 3H), 4.49 (d, J=4.3Hz,
6H), 2.72 (q, J= 7.5 Hz, 6H), 2.19 (dd, J= 13.6, 6.2 Hz, 3H), 2.15–2.10 (m,
3H), 1.94 (dd, J= 13.6, 7.9 Hz, 3H), 1.27–1.21 (m, 12H), 1.11 (dd, J=13.9,
6.7 Hz, 3H), 1.00 (d, J= 6.6 Hz, 9H), 0.93 (s, 27H); 13C NMR (126 MHz,
CD
3
CN) δ171.64,143.59,132.39,50.28,45.58,37.34,30.56,29.33,27.19,
22.61, 22.02, 15.58; FT-IR ν= 3304, 2955, 2904, 2869, 1632, 1525, 1494,
1466, 1364; ESI-MS (m/z)C
42
H
75
N
3
O
3
[M+ Na]+, calcd. 692.570, ound
692.571. NMR da a a e shown in Supplemen a y In o ma ion Figs. 14
and 15.
P ecipi a ion p ocedu e o mixed-RE solu ions
Ni ic acid solu ions (1–12 M) we e p epa ed by dilu ion o con-
cen a ed ni ic acid wi h ul a-pu e deionised wa e . Mixed-RE solu-
ions (0.0025 M) we e p epa ed by dilu ion o a 0.1M s ock solu ion
con aining La-Lu (no Pm, Sc,Y) me al sal s in o he p epa ed ni ic acid
solu ions ogi ea o alaqueousphase olumeo 2ml.Toluene(2ml)
was added o each sample. Solid L (0.35 mmol) was added o a ial
alongwi h a magne ic s i ba ( he o de o addi ion o RE ni a e andL
is no impo an ). The mix u e was s i ed o 24 h a 298K a 700 pm
a e which he s i ba was emo ed. Samples we e p epa ed o ICP-
MS o measu e he me al con en emaining in he aqueous phase
(compa ed wi h he eed solu ion) o de e mine me al up ake by L.
Samples we e dilu ed by500x in 2% ni ic acid p io o ICP-MS analysis.
These p ocedu es we e epea ed in duplica e.
P ecipi a ion p ocedu e o bina y-mixed-RE solu ions a ying
me al:me al mola a ios
Ni ic acid solu ions (8M) we e p epa ed by dilu ion o concen a ed
ni ic acid wi h ul a-pu e deionised wa e . Bina y-mixed-RE solu ions
(La/Dy, La/Nd, Nd/Dy) a me al:me al mola a ios o 5:1, 1:5, and 1:1
(0.0125 M and 0.0025 M espec i ely) we e p epa ed by dilu ion o
0.1M s ock solu ions o La, Nd, and Dy me al sal s in o he p epa ed
ni ic acid solu ions o gi e a o al aqueous phase olume o 2 ml.
Toluene (2ml) was added o each sample. Solid L (0.15 o 0.05 mmol,
5- old excess ela i e o me al) was added o a ial along wi h a mag-
ne ic s i ba . The mix u e was s i ed o 24 h a 298 K a 700 pm a e
which he s i ba was emo ed. Samples we e p epa ed o ICP-MS o
measu e he me alcon en emainingin heaqueousphase(compa ed
wi h he eed solu ion) o de e mineme alup akebyL.Sampleswe e
dilu ed by 5000x in 2% ni ic acid p io o ICP-MS analysis. These
p ocedu es we e epea ed in duplica e.
P ecipi a ion p ocedu e om single-me al lan hanum solu ion
a ying ligand:me al mola a ios
Ni ic acid solu ions (8M) we e p epa ed by dilu ion o concen a ed
ni ic acid wi h ul a-pu e deionised wa e . La(NO
3
)
3
(0.0025 M) solu-
ions we e p epa ed by dilu ion o a 0.1M s ock solu ion con aining
lan hanum ni a e in o he p epa ed ni ic acid solu ions o gi e a o al
aqueous phase olume o 2ml. Toluene (2 ml) was added o each
sample. The p ecipi a ions we e ca ied ou using a ying concen a-
ions o L (0.005 mol) which was added o a ial as a solid along wi h a
magne ic s i ba . The mix u e was s i ed o 24h a 298K a 700 pm
a e which he s i ba was emo ed. Samples we e p epa ed o ICP-
MS o measu e he me al con en emaining in he aqueous phase
(compa ed wi h he eed solu ion) o de e mine me al up ake by L.
Samples we e dilu ed by500x in 2% ni ic acid p io o ICP-MS analysis.
Recycling expe imen s
Ni ic acid solu ions (8M) we e p epa ed by dilu ion o concen a ed
ni ic acid wi h ul a-pu e deionised wa e . La(NO
3
)
3
(0.025 M) solu-
ions we e p epa ed by dilu ion o a 0.1M s ock solu ion con aining
lan hanum ni a e in o he p epa ed ni ic acid solu ions o gi e a o al
aqueous phase olume o 4ml. Toluene (2ml) was added o each
sample. Solid L (0.05 mol) was added o a ial along wi h a magne ic
s i ba . The mix u e was s i ed o 24 h a 298 K a 700 pm a e
which he s i ba was emo ed. Samples we e p epa ed o ICP-MS o
measu e he me alcon en emainingin heaqueousphase(compa ed
wi h he eed solu ion) o de e mineme alup akebyL.Sampleswe e
dilu ed by 1000x in 2% ni ic acid p io o ICP-MS analysis. The me al-
con aining p ecipi a e was collec ed h ough fil a ionanddissol edin
me hanol (3ml) and he ee ligand p ecipi a ed wi h wa e (1 ml). The
A icle h ps://doi.o g/10.1038/s41467-022-32178-3
Na u e Communica ions | (2022) 13:4497 4
p ecipi a ed ligand was collec ed by fil a ion and added o a new
biphasic solu ion. The p ecipi a ion and analysis p ocedu e we e ca -
ied ou as be o e.
X- ay c ys al s uc u e o 1-La
Colou lessblocks we e g own by slow e apo a ion o a supe sa u a ed
solu ion (10 mM) o 1-La in ace oni ile o e a pe iod o se e al
mon hs. X- ay da a we e collec ed a 120 K on an Ox o d Di ac ion
Supe no a, Dual, Cu a Ze o A las di ac ome e using Cu-K
α
adia ion
(λ= 1.5418 Å). The s uc u e was sol ed by di ec me hods using
ShelXT and efined using a ull-ma ix leas -squa es efinemen using
ShelXL41,42, bo h wi hin he Olex2 ( 1.5) so wa e43. X- ay da a a e p e-
sen ed in Supplemen a y In o ma ion Table 1.
Powde X- ay di ac ion
Da a o La/Nd/Dy powde s we e collec ed using a B uke D2 phase
di ac ome e in eflec ion geome y wi h Cu Kα adia ion
(λ=1.541 Å). A LynxEye posi ion sensi i e de ec o was used o collec
da a o e he 2θ ange 5–45° o 45 min. Sample p epa a ion in ol ed
g inding powde samples, a loading in o he ecess (1 mm deep) o a
ze o-backg ound silicon (911) subs a e. The La da a we e analysed
using a Pawley fi ing ou ine in he Topas Academic ( e sion 6)
so wa e sui e.
ICP-MS analysis
ICP-MS analysis was ca ied on an Agilen 7800 Single Quad upole
Induc i ely Coupled Plasma Mass Spec ome e . Samples in 2% ni ic
acid we e aken up by a pe is a ic pump a a a e o 0.3 ps in o a
Mic oMis nebulise and a qua z Sco ype sp ay chambe . A gon
plasma condi ions we e 1550 W RF powe and gas flows o 15, 1.07, and
0.9 l min−1 o plasma, auxilia y, and nebulise flow, espec i ely.
IR and Raman spec oscopy
Raman spec a we e eco ded on an InVia Renishaw spec ome e a
532 and 785 nm. Fou ie ans o m-in a ed (ATR FT-IR) measu emen s
we e collec ed on a Pe kin Elme 65 FT-IRspec ome e o e he ange
4000–500 cm−1.
Mass spec ome y
ESI-FT-ICR MS measu emen s o 1-La in CH
3
CN we e eco ded in
posi i e-ion mode using he s anda d B uke ESI sp aye wi h a Sola iX
FTICR mass spec ome e . All mass spec a we e analysed using
Da aAnalysis so wa e. Ions we e assigned manually.
NCI plo s and QTAIM analysis
A omic posi ions in he c ys al s uc u e we e op imised using
CASTEP17.2144,wi hon- he-fly pseudopo en ials and a plane-wa ecu
o o 750eV, coupled o he PBE DFT unc ional and TS dispe sion
co ec ion scheme45–47. B illouin zone sampling was below 0.05 Å−1.
Geome y op imisa ion c i e ia: ene gy ole ance = 2 × 10−5eV a om−1,
max o ce= 0.05 eV Å−1, max a omic displacemen = 2 × 10−3Å. Follow-
ing geome y op imisa ion, a cha ge densi y cube wasgene a ed using
he CASTEP2CUBE acili y and subsequen ly used o gene a e he NCI
plo using he CRITIC2 code, which was also employed o he QTAIM
analysis based on he p omolecula elec on densi y de i ed o he
op imised DFT s uc u e48–50. The NCI g aphical ou pu was p ocessed
using VMD1.9.351 o isualise he hyd ogen bond in e ac ion 3D iso-
su ace da a (p esen ed a educed elec on densi y s= 0.5 au and
sign(λ2)ρ=−0.05–−0.03 au), and O igin19 o p esen all NCIs as a 2D
ep esen a ion.
Da a a ailabili y
X- ay da a a e a ailable ee o cha ge om he Camb idge C ys al-
log aphic Da a Cen e (h ps://www.ccdc.cam.ac.uk/da a_ eques /ci )
unde e e ence numbe CCDC 2142978. The quan i a i e me al
analyses, IR, Raman, and NMR da a a e a ailable in he Edinbu gh
Da aSha e Reposi o y h ps://doi.o g/10.7488/ds/3419. The au ho s
decla e ha all o he da a suppo ing he findings o his s udy a e
a ailable wi hin he pape and i s Supplemen a y In o ma ion files.
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Acknowledgemen s
This esea ch was unded by he Uni e si y o Edinbu gh and he Na u al
En i onmen Resea ch Council E4: Edinbu gh Ea h, Ecology and
En i onmen Doc o al T aining Pa ne ship, g an numbe NE/S007407/
1(PhDs uden ship o J.O’C.-D., ecei ed by J.B.L.). We hank he Edin-
bu gh Compu e and Da a Facili y (ECDF, C.A.M.) o access o high-
pe o mance compu ing. We a e g a e ul o compu a ional suppo
om he UK Ma e ials and Molecula Modelling Hub, which is pa ially
unded by EPSRC (EP/PO20194 and EP/T022213, C.A.M.), o which
access was ob ained ia he UKCP conso ium and unded by EPRSC
g an e EP/P022561/1 (C.A.M.). We also hank D Ca oline Ki k a he
Uni e si y o Edinbu gh o eco ding and analysing he powde X- ay
di ac ion da a and D Ga y Nichol a he Uni e si y o Edinbu gh o his
help wi h single-c ys al X- ay c ys allog aphy.
Au ho con ibu ions
J.G.O’C.-D. unde ook all o he expe imen al wo k and analy ical cha -
ac e isa ion, spec oscopic analysis, and X- ay c ys allog aphy. C.A.M.
pe o med he NCI analysis. J.G.O’C.-D., C.A.M., B.T.N., and J.B.L. ana-
lysed he da a and w o e he manusc ip . C.A.M., B.T.N., and J.B.L.
di ec ed he esea ch.
Compe ing in e es s
The au ho s decla e no compe ing in e es s.
Addi ional in o ma ion
Supplemen a y in o ma ion The online e sion con ains supplemen a y
ma e ial a ailable a
h ps://doi.o g/10.1038/s41467-022-32178-3.
Co espondence and eques s o ma e ials should be add essed o
Jason B. Lo e.
Pee e iew in o ma ion Na u e Communica ions hanks Rebecca
Abe gel and he o he , anonymous, e iewe (s) o hei con ibu ion o
he pee e iew o his wo k.
Rep in s and pe mission in o ma ion is a ailable a
h p://www.na u e.com/ ep in s
Publishe ’s no e Sp inge Na u e emains neu al wi h ega d o ju -
isdic ional claims in published maps and ins i u ional a filia ions.
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