Synthesis and reactivity of Ln- and LnNa-macrocyclic compartmental Schiff base and polyamino complexes

Article abstract of DOI:10.1016/j.ica.2014.03.032

The [1+1] Schiff base macrocyclic ligands H₂L_A and H₃L_B, synthesized by condensation of 3,3′-(3- oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) (H₂L′) with 1,5-diamino-3-azamethylpentane (A′) and N,N-bis(2-aminoethyl)-2- hydroxybenzylamine·3HCl (HB′·3HCl), respectively, and their related polyamines H₂R_A and H₃R_B, which exhibit enhanced stability toward hydrolysis and greater flexibility, give rise to a wide series of mono-Ln and heterodinuclear-LnNa complexes. The crystal structure of [LuNa(R_B)(OH)]₂, determined by single-crystal X-ray diffraction, indicates the preference of the lutetium(III) ion and of the sodium(I) ion for the Schiff base and the crown-ether like chambers, respectively. To test the flexibility of reduced ligands and the possibility to encapsulate different lanthanide(III) ions in the coordinating moiety, [LuNa(R_B)(CH₃COO)]·2iPrOH, [LuNa(L _B)(Cl)], [LaNa(R_B)(Cl)] and [LaNa(L_B)(Cl)] are mixed with different lanthanide(III) salts to detect metalation, demetalation, transmetalation and/or site migration processes by ESI mass spectrometry and NMR spectroscopy. In particular the role of the metals and of the coordinating moiety in directing these processes is discussed. Furthermore, the possibility to use these complexes as probe for selective recognition of alkali and alkaline earth metal ions is tested by ESI mass spectrometry on [LuNa(R _B)(CH₃COO)]·2iPrOH and by the ²³Na NMR shift on [YbNa(R_B)(CH₃COO)]. The partial or total transmetalation of the sodium(I) ion represents a relevant result capable to open interesting scientific opportunities.

Full text of DOI:10.1016/j.ica.2014.03.032

Inorganica Chimica Acta 416 (2014) 226–234
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and reactivity of Ln- and LnNa-macrocyclic compartmental
Schiff base and polyamino complexes
Valentina Peruzzo a, Arianna Lanza b, Fabrizio Nestola c, Pietro Alessandro Vigato a, Sergio Tamburini a,
⇑
a Istituto per l’Energetica e Interfasi (I.E.N.I.), C.N.R., C.so Stati Uniti 4, Padova 35127, Italy
b Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland
c Dipartimento di Geoscienze, Università degli Studi di Padova, via Gradenigo 6, 35131 Padova, Italy
a r t i c l e i n f o
a b s t r a c t
The [1+1] Schiff base macrocyclic ligands H2LA and H3LB, synthesized by condensation of 3,30-(3-oxapen-
tane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) (H2L0) with 1,5-diamino-3-azamethylpentane (A0) and
N,N-bis(2-aminoethyl)-2-hydroxybenzylamineꢀ3HCl (HB0ꢀ3HCl), respectively, and their related poly-
amines H2RA and H3RB, which exhibit enhanced stability toward hydrolysis and greater flexibility, give
rise to a wide series of mono-Ln and heterodinuclear-LnNa complexes. The crystal structure of
[LuNa(RB)(OH)]2, determined by single-crystal X-ray diffraction, indicates the preference of the lute-
tium(III) ion and of the sodium(I) ion for the Schiff base and the crown-ether like chambers, respectively.
To test the flexibility of reduced ligands and the possibility to encapsulate different lanthanide(III) ions in
the coordinating moiety, [LuNa(RB)(CH3COO)]ꢀ2iPrOH, [LuNa(LB)(Cl)], [LaNa(RB)(Cl)] and [LaNa(LB)(Cl)]
are mixed with different lanthanide(III) salts to detect metalation, demetalation, transmetalation and/
or site migration processes by ESI mass spectrometry and NMR spectroscopy. In particular the role of
the metals and of the coordinating moiety in directing these processes is discussed.
Article history:
Received 15 November 2013
Received in revised form 21 March 2014
Accepted 23 March 2014
Available online 1 April 2014
Keywords:
Compartmental macrocycles
Lanthanide(III) Schiff base
Lanthanide(III) cyclic polyamine complexes
Heterodinuclear complexes
Furthermore, the possibility to use these complexes as probe for selective recognition of alkali and
alkaline earth metal ions is tested by ESI mass spectrometry on [LuNa(RB)(CH3COO)]ꢀ2iPrOH and by
the 23Na NMR shift on [YbNa(RB)(CH3COO)]. The partial or total transmetalation of the sodium(I) ion rep-
resents a relevant result capable to open interesting scientific opportunities.
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
The availability of asymmetric macrocyclic ligands represents
an almost necessary prerequisite to obtain stable mononuclear
The ability of compartmental macrocyclic ligands to coordinate
two (or more) lanthanide(III) ions in close proximity into their
adjacent coordination chambers by appropriate bridging groups
has been successfully experienced in the past [1–7]. It has been
verified that the shape of the coordinating sites of these ligands
is of paramount relevance in the encapsulation of two or more
4f-metal ions into the macrocyclic moiety. The [2+2] self- or tem-
plate condensation of 2,6-diformyl-4-substituted phenols with pri-
mary diamines of the type H2N(CH2)nX(CH2)nX(CH2)nNH2 give rise
to compartmental ligands with adjacent chambers, large enough to
accommodate two lanthanide(III) ions [8]. The interesting variety
of homodi- and polynuclear complexes obtained has allowed the
study of the mutual interactions between the lanthanide(III) ions
across the bridging ligands and to qualify and quantify the result-
ing catalytic, optical and magnetic properties [1,9–13,14–16].
complexes capable of evolving in positionally pure heterodinuclear
ones. Mononuclear complexes revealed their role in the prepara-
tion of molecular probes for the detection of alkali or alkaline earth
ions from suitable solvents (especially water), in the recognition of
specific charged or neutral organic species, in the formation of
single molecule magnets, single ion magnets or metal organic
frameworks, etc. [17,18,7b].
In the present paper the syntheses of [1+1] asymmetric
macrocyclic Schiff bases H2LA and H3LB and their related reduced
polyamino derivatives H2RA and H3RB (Scheme 1) are reported.
This paper is focused on the ability of these compartmental sys-
tems to form mononuclear lanthanide(III) or heterodinuclear lan-
thanide(III)–alkali or alkaline earth complexes.
Deep attention is devoted to determine the structure and prop-
erties of the polyamino derivatives whose relevance is in their
enhanced stability toward hydrolysis and in their enhanced
flexibility in comparison with the related Schiff base precursors.
In particular, possible routes for the obtainment of these systems
⇑
Corresponding author. Tel.: +39 0498295963; fax: +39 0498295951.
E-mail address: tamburini@ieni.cnr.it (S. Tamburini).
http://dx.doi.org/10.1016/j.ica.2014.03.032
0020-1693/Ó 2014 Elsevier B.V. All rights reserved.

V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
227
2
2
1
3
1
3
4
4
O
O
O
O
O
O
O
O
O
O
O
O
12
13
12
13
OH
OH
N
OH
OH
N
OHHN
N
OHHN
N
5
6
5
6
7
OH
11
OH
7
N
N
N
N
OHHN
OHHN
8
10
9
H3-LB
H2-LA
H2-RA
H3-RB
Scheme 1. Synthesized ligands.
and for their characterization are nodal points for subsequent stud-
ies in the field of stable shift reagents with a specific affinity
towards alkali or alkaline earth metal ions.
The application of the reduced complexes is bound to a qualita-
tive study of metalation–demetalation, transmetalation reactions
both at the lanthanide(III) and sodium(I) ion in order to verify
the complexity and stability of the resulting system. In these stud-
ies ESI mass spectrometry revealed to be a fast and reliable tool to
detect these processes and the occurrence of homo- and heterodi-
nuclear species in solution.
Reactivity of [LuNa(RB)(CH3COO)], [LnNa(LB)(Cl)] (Ln = Lu, La)
and [LaNa(RB)(Cl)] in the presence of different lanthanide(III) salts,
monitored by ESI mass spectrometry and NMR spectroscopy, testi-
fies quite interesting metalation, demetalation and/or transmetala-
tion processes elucidating the role of the different 4f-metal(III) ions
in directing these reactions.
using graphite monochromatized MoK
a
radiation (50 kV, 40 mA).
Single crystals of [LuNa(RB)(OH)] were obtained by slow diffusion
of hexane in a solution of [LuNa(RB)(CH3COO)](NaCl)0.1ꢀ1iPrOH in
CH3OH. As the crystals undergo rapid decomposition when
exposed to the air, the sample was protected in a 0.5 mm borosil-
icate glass capillary, in presence of its mother solution and quartz
wool was used to prevent the sample from moving during the data
collection. Any attempt to perform low temperature measure-
ments for this material is useless as the mother solution would
freeze and at the same time no other solution or oil (i.e. silicon
oil) can allows the sample to remain stable over the time. There-
fore, we did not have any other possibility to collect diffraction
data using a different approach. Diffraction data were collected
by sampling a full sphere of reciprocal space by 1° steps in
x
and , with an exposure time of 20 s per frame. Data reduction
u
and empirical absorption correction were performed using CrysAlis
RED and Abspack, respectively [22]. Due to the non-conventional
sample setup, causing both high absorption and high background
noise from the capillary and quartz wool scattering, the integration
was truncated at a resolution of 1 Å, to allow reasonable values of
2. Experimental
2.1. Materials
the Rint and I/r. (0.06 and 7.76, respectively). The structure was
solved using SIR2011 [23] and least-squares refined against F2 with
SHELXL-2013 [22]. All non-hydrogen atoms were refined with aniso-
tropic ADPs, except for one lattice water molecule. Due to the low
resolution dataset, H atoms bound to O and N atoms could not be
located from the fourier-difference map and only the unambiguous
ones have been placed at geometrically calculated positions and
refined with a riding model.
The morphology and homogeneity of the complexes were
investigated using a Fei-Esem FEI Quanta 200 FEG instrument,
equipped with a field emission gun, operating in high vacuum con-
dition at an accelerating voltage variable from 0 to 30 keV, depend-
ing on the observation needs. EDX analyses were obtained by using
an EDAX Genesis energy-dispersive X-ray spectrometer at an
accelerating voltage of 25 keV.
Solvents, LnCl3ꢀnH2O and Ln(CH3COO)3ꢀmH2O, the amine pre-
cursor 1,5-diamino-3-azamethylpentane (A0), NaBH4 and the cata-
lyst Pd/C (10%) are commercial products (Aldrich, Riedel de Haën,
Carlo Erba or Fluka) and they are used without any further purifi-
cation. The diformyl precursor 3,30-(3-oxapentane-1,5-diyldi-
oxy)bis(2-hydroxybenzaldehyde) (H2L0) [19,20] and the amine
precursor
N,N-bis(2-aminoethyl)-2-hydroxybenzylamineꢀ3HCl
(HB0ꢀ3HCl) [21] were prepared according to literature.
2.2. Physico-chemical measurements
Elemental analyses were carried out using a Fisons 1108 ana-
lyzer. IR spectra were recorded as KBr pellets on a Mattson FTIR
spectrometer. All NMR spectra were recorded on a Bruker Avan-
ceIII-300 equipped with direct and inverse broad-band multinu-
clear probes and variable-temperature unit, with complexes
dissolved in CH3OH-d4 or DMSO-d6. The T1 longitudinal relaxation
times and the mixing times of NOESY experiments were measured
using the standard inversion recovery pulse sequence. ESI mass
spectrometric measurements were performed using a LCQ-Fleet
mass spectrometer (Thermo Fisher, USA) equipped with an ion
2.3. Macrocyclic Schiff base ligands
H2LAꢀ1.5H2O and [Na(H2LB)]ꢀ2NaCl are synthesized according to
literature [24,26]. The proposed formulations are confirmed by
NMR and IR spectroscopy, by elemental analysis, ESEM-EDS and
ESI mass spectrometry.
trap. Analyses were performed by infusion (13 lL/min) of metha-
nolic solutions of the samples (10ꢁ6 M). The spray capillary is
maintained at 30 °C and the applied voltage was 3 kV. Collisions
were performed by applying a supplementary rf (radiofrequency)
voltage to the end caps. Ion isolation was performed by a mass
window of 5 units. The supplementary rf voltage was in the range
30–35% of its maximum value (5 V-peak-to-peak).
Single-crystal X-ray diffraction measurements were carried out
at room temperature on a STOE STADI IV four-circle diffractometer
equipped with a Sapphire I CCD detector by Oxford Diffraction,
2.4. Macrocyclic polyamine ligands
[Na2(RA)]ꢀ1H2O is synthesized according to literature [24]. The
proposed formulation is confirmed by NMR and IR spectroscopy,
by elemental analysis, ESEM-EDS and ESI mass spectrometry.
[Na(H2RB)]: A methanol solution of [Na(H2LB)]ꢀ2NaCl (0.5 mmol,
311 mg) and NaBH4 (2.0 mmol, 75.66 mg) was refluxed for 1 h and
evaporated to dryness. The residue was treated with ethanol and
the clarified solution was again evaporated to dryness. The

228
V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
resulting solid was dissolved in iPrOH and the solution was clari-
fied. The final compound, obtained by evaporation to dryness,
was washed with diethyl ether and water was and then collected
by filtration and dried in vacuo.
solution is evaporated to dryness and ethanol is added. The solu-
tion was clarified, evaporated and iPrOH is added. The solution
was clarified, evaporated and chloroform was added to collect a
precipitate which was washed with water and dried in vacuo.
Yield: 85.2 mg, 32%. IR (cmꢁ1): 3281 (
m
(N–H)). ESI-MS: m/
Yield: 178 mg, 55.1%. IR (cmꢁ1): 3253 (
m (N–H)). ESI-MS (addi-
z = 524 [H3RB+H+]. 1H NMR CH3OH-d4 (ppm): 7.21 (d, 1H, 8), 7.18
(d, 2H, 1), 7.13 (m, 1H, 10), 6.97 (d, 2H, 3), 6.95 (m, 1H, 11), 6.93
(m, 2H, 2), 6.85 (m, 1H, 9), 4.37–4.21 (m, 4H, 12), 4.13 (s, 4H, 4),
4.03–3.92 (m, 4H, 13), 3.68 (s, 2H, 7), 3.26 (m, 4H, 5), 2.89 (t, 4H,
6). Anal. Calc. for C29H36N3NaO6: C, 63.84; H, 6.65; N, 7.70. Found:
C, 63.29; H, 6.36; N, 7.03%.
tion of NH4OAc): m/z 668 [Y(RB)(CH3COO)]ꢁ. 1H NMR CH3OH-d4
d (ppm): 7.10 (t, 1H, 8), 6.99–6.88 (m, 2H, 2), 6.87–6.70 (m, 3H,
9+3), 6.64–6.52 (m, 3H, 1+10), 6.50–6.30 (m, 1H, 11), 4.86–4.65
(m, 8H, 12+13), 4.28–4.16 (m, 4H, 4), 3.72 (s, 2H, 7), 2.81 (t, 4H,
6), 2.64 (t, 4H, 5). Anal. Calc. for C31H37N3NaO8Y: C, 53.15; H,
5.47; N, 6.00. Found: C, 52.26; H, 4.95; N, 5.85%.
[Y(RA)(Cl)]ꢀ3.5H2O: [Y(LA)(Cl)]ꢀ3H2O (1 mmol, 606 mg) in meth-
anol (100 ml) was treated with Pd/C (10%) under hydrogen pres-
sure (50 bar) at 70 °C for 3 h and then allowed to stand. The
mixture was filtered and the resulting solution was evaporated
to dryness. The precipitate, after addition of diethyl ether, was col-
lected by filtration, washed with water and diethyl ether and dried
in vacuo.
2.5. Schiff base complexes
[LaNa(LB)(Cl)], [LuNa(LB)(Cl)], [YNa(LB)(CH3COO)]ꢀ1iPrOH and
[Y(LA)(Cl)]ꢀ3H2O are synthesized according to literature [24,26].
The proposed formulations are confirmed by NMR and IR spectros-
copy, by elemental analysis, ESEM-EDS and ESI mass spectrometry.
Yield: 500 mg, 82%. IR (cmꢁ1): 3250 (
m (N–H)). ESI-MS: m/
2.6. Amino complexes
z = 588 [Y(RA)(Cl)2]ꢁ. 1H NMR CH3OH-d4 d (ppm) 0 °C: 6.99 (d,
2H, 1), 6.85 (d, 2H, 3), 6.57 (t, 2H, 2), 4.70–4.32 (m, 4H, 12+13),
4.32–4.13 (m, 4H, 4+120), 4.13–3.88 (m, 2H, 130), 3.35–3.29 (m,
1H, 6b), 3.21–3.10 (dt, 2H, 6a+50), 2.88–2.64 (m, 6H, 60a+60b+5),
2.30 (s, 3H, 7). Anal. Calc. for C23H37ClN3O8Y: C, 44.78; H, 6.21; N,
6.81. Found: C, 44.31; H, 6.26; N, 7.11%.
[Lu2(RA)(Cl)4]ꢀEtOH: [Na2(RA)]ꢀ1H2O (0.5 mmol, 247 mg) and
LuCl3ꢀnH2O (0.5 mmol, 196 mg) were mixed in methanol and the
solution refluxed for 3 h. The solution was evaporated and metha-
nol was added. The clarified solution was evaporated, ethanol was
added and the solution clarified again. After evaporation to dry-
ness, chloroform is added and the precipitate collected, washed
and dried in vacuo.
[DyNa(HRB)(CH3COO)](NaCl)ꢀ1H2O,
[LuNa(RB)(CH3-
COO)](NaCl)0.1ꢀ1iPrOH and [YbNa(RB)(CH3COO)]: A methanol solu-
tion of HB0ꢀ3HCl (1 mmol, 318.67 mg) and NaOH (6 mmol,
240 mg)) was added to a methanol solution of H2L0 (1 mmol,
117.19 mg)) and LnAc3ꢀnH2O (1 mmol, LnIII = DyIII – 411.5 mg, LuIII
– 352 mg, YbIII – 404 mg). After refluxing for 1 h, NaBH4 (4 mmol,
151.4 mg) was added and the mixture refluxed for another 1 h.
After evaporation to dryness iPrOH was added and the precipitate
was collected, washed with iPrOH and water and dried in vacuo.
[DyNa(HRB)(CH3COO)](NaCl)ꢀ1H2O: Yield: 403 mg, 52.7%. IR
Yield: 60 mg, 12.5%. IR (cmꢁ1): 3260 (
m (N–H)). ESI-MS: m/
z = 884 [Lu2(RA)(Cl)3]+. 1H NMR CH3OH-d4 45 °C(ppm): 6.84–6.53
(m, 4H, 1+3), 6.38–6.15 (m, 2H, 2), 4.2–4.02 (m, 4H, 120+130),
4.02–3.93 (m, 2H, 13), 3.93–3.80 (m, 2H, 12), 3.65 (s, 4H, 4),
2.78–2.64 (m, 2H, 60), 2.64–2.55 (m, 2H, 50), 2.55–2.42 (m, 2H, 6),
2.42–2.27 (m, 2H, 5), 1.89 (bs, 3H, 7). Anal. Calc. for C25H37Cl4Lu2N3-
O6: C, 31.04; H, 3.86; N, 4.34. Found: C, 32.15; H, 4.25; N, 5.02%.
[LaNa(RB)(Cl)]: NaBH4 (2.4 mmol, 90.8 mg) was added to a
methanol solution of [LaNa(LB)(Cl)] (0.6 mmol, 427.8 mg) and then
refluxed for 1 h. The solution was evaporated to dryness and etha-
nol was added. The solution was clarified, then evaporated. The
resulting solid was washed with chloroform and then water and
dried in vacuo.
(cmꢁ1): 3265 ( (N–H)). ESI-MS: m/z = 706 [DyNa(RB)]+ Anal. Calc.
m
for C31H37DyN3NaO8: C, 43.78; H, 4.74; N, 4.94. Found: C, 44.14;
H, 4.96; N, 4.70%.
[LuNa(RB)(CH3COO)]ꢀ2iPrOH: Yield: 754 mg, 89.5%. IR (cmꢁ1):
3264 (m
(N–H)). ESI-MS: m/z = 718 [LuNa(RB)]+. 1H NMR DMSO-d6
d (ppm): 7.25–6.99 (m, 2H, 8+10), 7.00–6.84 (m, 2H, 1), 6.80 (t,
1H, 9), 6.76–6.57 (m, 2H, 3), 6.52 (d, 1H, 11), 6.50–6.33 (m, 2H,
2), 4.34–4.06 (m, 4H, 12+120), 4.06–3.90 (m, 4H, 13+130), 3.93–
3.80 (m, 2H, 6a+6b), 3.77 (s, 4H, 4), 3.72 (s, 2H, 7), 3.28–2.95 (m,
4H, 5), 2.94–2.61 (m, 4H, 6a0+6b0). Anal. Calc. for C34H45Cl0.1LuN3-
Na1.1O9: C, 49.45; H, 6.06; N, 4.68. Found: C, 51.24; H, 5.26; N,
4.76%.
Yield: 250 mg, 62.5%. IR (cmꢁ1): 3265 (
m
(N–H)). ESI-MS: m/
z = 607 [La2(HRB)(RBꢁCH2PhOH)]2+
,
1319 [La2(RB)(RBꢁCH2-
PhOH)]+. 1H NMR DMSO-d6 d (ppm): 6.87 (m, 2H, 8+10), 6.67 (d,
2H, 1), 6.56 (d, 2H, 3), 6.42–6.04 (m, 4H, 2+11+9), 4.19–3.81 (m,
6H, 12), 3.63–3.40 (m, 2H, 13), 3.53 (s, 2H, 7), 3.32–3.18 (m, 1H,
60), 8.43 (m, 2H, 50), 2.36–2.24 (m, 1H, 6a), 2.22–2.09 (m, 1H, 6b),
2.02–1.85 (m, 2H, 5). Anal. Calc. for C23H34ClLaN3NaO6: C, 48.52;
H, 4.77; N, 5.85. Found: C, 48.03; H, 4.90; N, 5.52%.
[YbNa(RB)(CH3COO)]: Yield: 356 mg, 47.3%. IR (cmꢁ1): 3259 (
m
(N–H)). ESI-MS: m/z = 713 [Yb(RB)(H2O)+H+]. Anal. Calc. for C31H37-
N3NaO8Yb: C, 48.00; H, 4.81; N, 5.42. Found: C, 47.64; H, 5.12; N,
4.92%.
[LuNa(RB)(Cl)]: NaBH4 (1.6 mmol, 60.5 mg) was added to a
methanol solution of [LuNa(LB)(Cl)] (0.4 mmol, 299.6 mg) and then
refluxed for 1 h. The solution was evaporated to dryness and etha-
nol was added. The solution was clarified, then evaporated and
iPrOH was added. The final solution was clarified, evaporated and
chloroform was added to collect a precipitate which was washed
with water and dried in vacuo.
3. Results and discussion
Different synthetic pathways were tested in order to set up a
fast one-step procedure for the obtainment of the reduced com-
plexes. The explored synthetic strategies are reported in Scheme 2.
Yield: 150 mg, 49.8%. IR (cmꢁ1): 3251 (
m (N–H)). ESI-MS: m/
z = 718 [LuNa(RB)]+. 1H NMR CH3OH-d4 d (ppm): 7.33–7.23 (m,
1H, 10), 7.19 (d, 2H, 1), 7.16–7.08 (m, 1H, 8), 7.00 (d, 2H, 3), 6.97
(t, 2H, 2), 6.94–6.76 (m, 2H, 9+11), 4.36 (bs, 4H, 12), 4.25 (s, 4H,
4), 4.07 (bs, 4H, 13), 3.72 (s, 2H, 7), 3.33–3.15 (m, 4H, 6+60a+60b),
3.05–2.85 (m, 4H, 5+50a+50b). Anal. Calc. for C29H34ClLuN3NaO6:
C, 46.19; H, 4.55; N, 5.57. Found: C, 45.15; H, 4.33; N 5.40%.
[YNa(RB)(CH3COO)]ꢀ0.5H2O: NaBH4 (2 mmol, 75.7 mg) was
3.1. Schiff base, related amino ligands or sodium precursors
H2LAꢀ1.5H2O and [Na(H2LB)]ꢀ2NaCl, are obtained by [1+1] self
condensation of the diformyl precursor (H2L0) and diamino precur-
sor (A0 and HB0ꢀ3HCl, respectively) under high dilution [24].
The related polyamino compounds [Na2(RA)]ꢀH2O and [Na(H2RB)]
derive from the addition of NaBH4 to a chloroform/methanol
added to
a
methanol solution of [YNa(LB)(CH3COO)]ꢀ1iPrOH
(0.5 mmol, 324 mg) and the solution was refluxed for 1 h. The

V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
229
HB'
A'
-R -CH3
O
O
O
HO
OH
OH
OH
OH
N
N
O
O
O
HN
N
H2N
+NaBH4
Na
R
O
O
R
O
N
R
Na
N
O
HN
H2N
O
O
O
H2L'
+NaOH
+Ln(CH3COO)3
+NaBH4
+NaOH
+Ln(CH3COO)3
+Ln(CH3COO)3
1+/2+
1+/2+
O
O
O
N
+NaBH4
+Pd/C
O
HN
Na Ln
N
N
R
O
R
O
O
Na
N
Ln
O
O
HN
O
Scheme 2. Synthetic strategies.
solution of H2LAꢀ1.5H2O (4:1 ratio) and to a methanol solution of
[Na(H2LB)]ꢀ2NaCl (4:1 ratio) followed by washing with distilled
water to eliminate inorganic salts. The very low yield (5%) of
[Na(H2RB)] prompted us to use the template condensation fol-
lowed by in situ reduction, which proved to be a successful and fast
way for the synthesis of the amino complexes (see later). Because
of its higher yield (32%) [Na2(RA)]ꢀH2O was preferentially used as
starting material for mononuclear or polynuclear complexation.
diffraction data, likely affected by crystal twinning, did not allow
a satisfactory refinement [27]. As such, only the connectivity was
established but it is clear from these data that the structure of
[YNa(LB)(CH3COO)(H2O)] is (Fig. 1) quite similar to that of
[DyNa(LB)(PrOH)(Cl)], structurally ascertained in a previous work
[26].
In the preformed Schiff base complexes, especially those with
[LB]3ꢁ, the lanthanide(III) ion is in a specific coordination chamber
and hence their reduction with NaBH4 lead to complexes with the
lanthanide(III) ion in the same site without site migration. Further-
more, the starting Schiff base complexes are very soluble in water,
while the relative reduced products are insoluble in water and
sparingly soluble in most organic solvents.
Both the ligands are characterised by the lack of the
m
(C@N) IR
bands and by the presence of
m
(N–H) IR bands at 3285–
3281 cmꢁ1. These asymmetric compartmental systems contain
two different coordination chambers (i.e. one N3O2 Schiff base site
and one O2O3 crown-ether like site) in close proximity and differ-
ent enough to host different specific metal ions so producing hete-
rodinuclear species.
3.2. Schiff base complexes and related reduced amino derivatives
The compartmental ligands H2LA and H3LB easily produce hete-
rodinuclear LnNa complexes when reacted with lanthanide(III)
salts in the presence of the sodium(I) ion already experienced in
previous works; in these complexes the lanthanide(III) ion occu-
pies the iminic compartment while the sodium(I) ion fills the ethe-
ric chamber as observed in the structure of [YbNa(LA)(Cl)2(CH3OH)]
[25]. The interaction, induced by the close proximity of the two
metal ions in these complexes, is quite relevant, as demonstrated
by the chemical shift of the 23Na NMR signal. This interaction is a
fundamental prerequisite to have a shift reagent [19,20,26].
[LaNa(LB)(Cl)], [LuNa(LB)(Cl)] and [YNa(LB)(CH3COO)]ꢀiPrOH are
obtained by [1+1] template condensation of H2L0 and HB0ꢀ3HCl in
the presence of the correspondent LnCl3ꢀnH2O and of NaOH.
The 1H NMR spectrum in CH3OH-d4 and the IR spectrum of
[YNa(LB)(CH3COO)]ꢀiPrOH and [LuNa(LB)(Cl)] are quite superim-
posable while those of the LaNa complex are significantly different,
probably as a consequence of the larger size of the lanthanum(III)
ion.
X-ray diffraction data on crystals of [YNa(LB)(CH3COO)(H2O)],
grown by diffusion of diethyl ether in a methanol solution, confirm
the heterodinuclear nature of the complex with the lanthanide(III)
ion in the Schiff base compartment and the sodium(I) ion in the
crown-ether like compartment. However, the poor quality of the
Fig. 1. Qualitative drawing of the structure of [YNa(LB)(CH3COO)(H2O)].

230
V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
[LaNa(LB)(Cl)] and [LuNa(LB)(Cl)] are reduced by an excess of
in situ reduction of the resulting Schiff base complex by NaBH4.
A subsequent solvent removal and purification of the resulting
solid with iPrOH and finally with H2O to eliminate the inorganic
salts afford the same amino complex.
NaBH4 to give [LaNa(RB)(Cl)] and [LuNa(RB)(Cl)], respectively. 1D
and 2D-NMR spectra in DMSO-d6 and CH3OH-d4, respectively,
show that one metal ion, reasonably the lanthanide(III) one, is
hosted in the aminic compartment as suggested by the involve-
ment of these protons in geminal couplings. The symmetric but
broad signals of the O2O3 compartment support the coordination
of the sodium(I) ion in this site. ESI-MS of [YNa(RB)(CH3COO)], sim-
ilarly obtained by NaBH4 reduction of [YNa(LB)(CH3COO)]ꢀiPrOH,
shows the signal of [Y(RB)(CH3COO)]ꢁ (m/z 668) .
Thus, the template reaction of H2L0, HB0ꢀ3HCl, NaOH and Ln(CH3-
COO)3ꢀnH2O (LnIII = DyIII, LuIII, YbIII), in a 1:1:1:6 ratio in methanol,
followed by the addition of NaBH4 gives rise to the reduced
complexes [DyNa(HRB)(CH3COO)](NaCl)ꢀ1H2O, [LuNa(RB)(CH3-
COO)]ꢀ2iPrOH and [YbNa(RB)(CH3COO)]. The lack of the
m
(C@N)
IR band at 1628 cmꢁ1 and the presence of
m (N–H) IR bands at
The catalytic reduction with Pd/C at 50 bar and at 70 °C was
experienced on [LaNa(LB)(Cl)], [LuNa(LB)(Cl)], [YNa(LB)(CH3-
COO)]ꢀiPrOH and on H3LB, but it did not yield reduction products.
On the other hand, [Y(LA)(Cl)]ꢀ3H2O is successfully reduced by
Pd/C (see later). This suggests that the catalytic reduction mecha-
nism of Pd on the iminic bond is not prevented by the coordinated
metal ion but by the steric hindrance of the phenolic pendant arm
of the ligand H3LB. This synthetic route consists in the dissolution
of the starting Schiff base complex in methanol followed by addi-
tion of the catalyst in a sealed autoclave under magnetic stirring.
After three hours, the catalyst is filtered and the solvent
evaporated.
The Pd/C catalytic hydrogenation of [Y(LA)(Cl)]ꢀ3H2O, synthe-
sized according to literature [19,20], yields [Y(RA)(Cl)]ꢀ3.5H2O. 1H
NMR, 1H–1H NOESY and 1H–13C HMQC in CH3OH-d4 give informa-
tion on the coordination of the metal ion; in particular in [Y(LA)(-
Cl)]ꢀ3H2O both the coordinating chambers are characterized by
asymmetric signals indicating the involvement in the coordination.
On the contrary, in the NMR spectrum of [Y(RA)(Cl)]ꢀ3.5H2O in CH3-
OH-d4, collected at 0 °C to reduce the flexibility, only the aminic
chain participates in the coordination in agreement with the
involvement of the aminic site in the coordination of the yttriu-
m(III) ion.
3253 cmꢁ1 support the reduction of the imine group. The formula-
tion and the Ln:Na:Cl ratio is confirmed by ESEM-EDS and by ele-
mental analyses. A further proof of the reduction of the Schiff base
ligands derives from the recovery of the 1H NMR spectrum of the
free H3RB after the addition of formic acid to a CH3OH-d4 solution
of [LuNa(RB)(CH3COO)](NaCl)0.1ꢀiPrOH. This treatment causes com-
plete demetalation of the complex. In the ESI-MS conditions
[LuNa(RB)(CH3COO)]ꢀ2iPrOH gives rise to the ion [LuNa(RB)]+ (m/z
718.09).
By diffusion of n-hexane in a methanolic solution of [LuNa(RB)(-
CH3COO)]ꢀ2iPrOH, crystals of [LuNa(RB)(OH)]2 are obtained. Crys-
tals are poorly soluble in most common NMR solvents with
respect to [LuNa(RB)(CH3COO)]ꢀ2iPrOH reflecting the formation of
a different structure.
The NMR spectra of the poorly soluble [LuNa(RB)(OH)]2 in CH3-
OH-d4 and DMSO-d6 are characterized by a high noise level. How-
ever, 2D-NMR analyses confirm the metal ion coordination. In fact,
the signals of the aromatic rings of the formyl precursor are pres-
ent as multiplets and also the signals of the aminic and etheric
chains give rise to multiplets both in DMSO-d6 and in CH3OH-d4.
In particular, the signal of the –CH2–N groups is a singlet at
3.77 ppm.
The close proximity between the lanthanide(III) and the
sodium(I) ion was verified on [YbNa(RB)(CH3COO)] by the 23Na
NMR shift in CH3OH-d4 at 30 °C. The spectrum is characterized
by the signal at 0 ppm characteristic of NaCl (added to the solution
to calibrate the spectrum) and by a broad signal at 85 ppm. It is
well known that complexes containing dinuclear (or polynuclear)
magnetic entities at appropriate distance and/or in well defined
stereochemistry exhibit peculiar magnetic properties, arising from
the nature and the magnitude of the interactions between the
metal ions within the molecular framework [19,20]. The entity of
the shift is correlated to several parameters (e.g. the distance
between the two interacting nuclei, the geometry of the metal ions
inside the coordinating chambers, temperature, etc.) Thus, the
extent of the 23Na NMR shift in [YbNa(RB)(CH3COO)] is strongly
related to the interaction between the sodium(I) and the paramag-
netic lanthanide(III) ion [28,29]. A comparison with the analogous
[YbNa(LA)(Cl)2], [25] whose 23Na NMR shift lies at ꢁ40 ppm at
25 °C in CH3OH-d4, shows a different interaction between the
metal ions in the two complexes, giving rise to different shift val-
ues. In principle, an important role is played by the different geom-
etry and flexibility of the coordinating chamber in [RB]3ꢁ and in
[LA]2ꢁ, the former bearing an additional coordinating atom on
the pendant arm; in spite of this difference, the Yb–Na interaction
persists generating the 23Na shift (Fig. 2).
Equimolar amounts of [Na2(RA)]ꢀH2O and of LuCl3ꢀnH2O in
methanol after work-up give rise to the homodinuclear complex
[Lu2(RA)](Cl)4ꢀEtOH. Qualitative ESI-MS studies indicate that the
addition of equimolar amounts of LaCl3ꢀnH2O or YCl3ꢀnH2O to the
preformed [Na2(RA)]ꢀH2O without purifivcation produces mononu-
clear derivatives together with NaLn and Ln2 complexes. In partic-
ular, the mononuclear lanthanum(III) complex gives rise to the
ions [La(H2RA–CH3)(Cl)2]+ (m/z 626, Relative Abundance = 80%)
and [LaNa(H2RA–CH3)(Cl)3]+ (m/z 684, 100%). Similarly, the yttriu-
m(III) complex gives rise to four different main species: [Y(HRA)
(Cl)]+ (m/z 554, 70%), [YNa(RA)(Cl)]+ (m/z 576, 100%), [YNa(H2RA–
CH3)(Cl)3]+ (m/z 634, 40%) and [Y2(HRA)(RA)(Cl)2]+ (m/z 1107,
20%). Furthermore, ESI-MS testifies that the addition of equimolar
amounts of LuCl3ꢀnH2O to a solution of the preformed [Na2(RA)]-
ꢀ1H2O lead to the mononuclear lutetium(III) complex (m/z 640,
100%), the dinuclear LuNa and Lu2 complexes at m/z 662 (15%)
and 884 (40%), respectively. ESI-MS data are not in contrast with
the synthetic result above reported: the formation of the homodi-
nuclear species in solution is indeed remarkable and, despite the
concurrent presence of mononuclear and heterodinuclear species,
which are detected thank to the intrinsic high sensitivity of mass
spectrometry, it represents the only isolated complex in the solid
state. The ionic radius seems to be a nodal point for the obtainment
either of mononuclear or dinuclear species.
The step-by-step synthetic procedure for the obtainment of the
reduced complexes is time consuming and the final yield is not sat-
isfactory. Especially the recovery of the Schiff base complexes
requires a long work-up because of its high solubility in water
and in most organic solvents. The subsequent reduction of the pre-
formed complex with NaBH4 or Pd/C–H2 and the collection of the
resulting complex are easier. This long procedure can be shortened
and simplified if the template condensation reaction in the pres-
ence of the appropriate lanthanide(III) salt is followed by the
3.3. Crystal structure
The crystals of [LuNa(RB)(OH)]2 are very unstable under atmo-
spheric conditions therefore a special setup was necessary in order
to allow the analysis by single-crystal X-ray diffraction (see Exper-
imental section). Diffraction data were obtained only up to a reso-
lution of 1 Å, nevertheless it was possible to deduce the molecular
structure with reasonable confidence (Fig. 3).

V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
231
Fig. 2. 23Na NMR spectrum of [YbNa(RB)(CH3COO)] in CH3OH-d4 at 25 °C.
Table 1
The complex, which crystallizes in the monoclinic system, with
Crystal data and structure refinements for complex [LuNa(RB)(OH)]2.
space group P21/c, and with 4 complexes per unit cell (Table 1),
forms a dimer, in which two lutetium(III) ions are linked by two
l
Complex
LuNa(RB)(OH)
-OHꢁ anions. The ligand hosts one sodium(I) ion in its O3O2
Formula
C
60H70Lu2N6Na2O16ꢀ2MeOHꢀH2O
crown-ether-like site and one lutetium(III) ion in the adjacent
ON3O2 aminic chamber; therefore the two ions, in close proximity
to each other (Luꢀ ꢀ ꢀNa 3.526(5) Å), share two bridging Oꢁ groups,
which pertain to opposite phenolate moieties of the (RB) macrocy-
cle. The sodium(I) ion exhibits a distorted 6-fold coordination,
involving five O atoms of the (RB) ligand and one additional
coordinated CH3OH molecule in apical position, whereas the lute-
tium(III) ion has an 8-fold coordination, completed in the apical
positions by the phenolate arm on the outer side of the dimer
Molecular weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
1605.20
monoclinic
P21/c
11.3466 (19)
12.794 (3)
23.985 (6)
90.00
95.374 (17)
90.00
3466.6 (13)
297(2)
2
1.538
1612
2.195
39289
a
(°)
b (°)
c
(°)
V (Å3)
T (K)
and two l
-OHꢁ anions on the inner side. Although it was not pos-
Z
Dcalc (g cmꢁ3
F(000)
)
sible to locate experimentally the hydrogen atoms pertaining to
OH and R2NH groups, the amino form of (RB) is confirmed by the
tetrahedral bond geometry around the N atoms. From the residual
electron density it can be inferred that some other solvent mole-
cules are present, very likely being hydrogen bonded to the O of
the apical phenolate group. The easy evaporation of such solvent
molecules could be the cause for the instability of the crystals
under atmospheric conditions, as the dimers themselves are poorly
interacting with each other and the packing is probably achieved
via weak hydrogen bonds with the lattice solvents conditions.
l(Mo K
a
) (mmꢁ1
)
Reflections collected
Unique reflections
Observed reflections [I > 2
3253
2933 [Rint = 0.0595]
r
(I)]
R [I > 2
R [all data]
Goodness of fit (GOF) on F2
r(I)]
R1(F) = 0.0615, wR2(F2) = 0.1581
R1(F) = 0.0719, wR2(F2) = 0.1667
1.178
processes and subsequent site migration of the different metal ions
(Table 2). ESI mass spectrometry can highlight the formation and
stability of each species occurring in solution in consequence of
these processes. The sensibility of this technique (concentration
of 10ꢁ6 M are required) makes the qualitative analyses feasible
in spite of the low solubility in organic solvents. Quantitative stud-
ies are very difficult considering the analytes concentration.
The lutetium(III) ion is the heaviest in the 4f-series and it has
the smallest ionic radius. The ESI-MS analyses of a methanol solu-
tion containing equimolar amounts of Ce(CH3COO)3ꢀnH2O and
3.4. Reactivity of LuNa and LaNa complexes
3.4.1. Lutetium(III) and lanthanum(III) substitution by different
lanthanide(III) ions
[LuNa(RB)(CH3COO)]ꢀ2iPrOH, [LuNa(LB)(Cl)], [LaNa(RB)(Cl)] and
[LaNa(LB)(Cl)] were mixed with lanthanide salts in methanol in
order to verify by ESI mass spectrometry the formation of new spe-
cies deriving from transmetalation, demetalation or metalation
Fig. 3. (left) ORTEP representation (with 30% probability ellipsoids) of the asymmetric unit for LuNa(RB)(OH) with partial labeling scheme; (right) sketch of the dimer
arrangement (hydrogen atoms have been omitted for clarity.

232
V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
[LuNa(RB)(CH3COO)]ꢀ2iPrOH gives rise to a spectrum where the
base peak is attributed to [LuCe(RB)(CH3COO)2]+ (m/z 953.3) while
additional signals due to [Ce2(RB)(CH3COO)2]+ (m/z 918.3, 15%) and
[Lu2(RB)(CH3COO)2]+ (m/z 988.3, 10%) are detected. By collision of
the LuCe complex the ion [LuCe(RB)(CH3COO)]+ (m/z 893.2) forms
with one acetate as counteranion and a deprotonated –NH–.
The addition of an equimolar amount of the smaller ytter-
bium(III) acetate to [LuNa(RB)(CH3COO)]ꢀ2iPrOH results in the for-
mation of [LuYb(RB)(CH3COO)2]+ (m/z 986.7, 100%) while only
traces of [LuNa(RB)(CH3COO)]+ (m/z 778.3, 10%) are present.
According to these results, the larger cerium(III) ion generates
various species when reacted with the LuNa aminic complex and
in spite of its large radius it gives rise also to the dinuclear ceriu-
m(III) complex. The coordination of the pendant arm to the ceriu-
m(III) ion makes the dinuclear LuCe complex stable. Usually, these
complexes loose the pendant arm [30], but in this case the LuCe
complex undergoes the loss of the acetate with a deprotonation
of the aminic group. The ytterbium(III) ion completely transmeta-
lates the sodium(I) ion from the related LuNa complex giving rise
to the predominant LuYb dinuclear complex.
formation of the homodinuclear species [Y2(RB)(CH3COO)2]+ at m/
z 816.2 (RA = 80%) and of the heterodinuclear species [LaY(RB)(-
CH3COO)2]+ at m/z 866.2 form (RA = 100%).
[LaNa(LB)(Cl)] gives rise to mixture of mono-, homo- and hete-
rodinuclear species when mixed with Ln(CH3COO)3ꢀnH2O (Ln = Lu,
Ce, Gd, Y) while the analogous LuNa does not react at all. Although,
it is not possible to find a general rule, it seems that the larger lan-
thanum(III) ion can be replaced by the smaller lanthanide(III) ion
while the lutetium(III) ion cannot be substituted, probably because
of its good fitting in the Schiff base chamber. More generally, we
can state that the more flexible amino complexes can easily
undergo metalation reactions with the formation of homo- and/
or heterodinuclear complexes, while in the related Schiff base com-
plexes the fitting of the metal is of paramount relevance for the for-
mation of new species and for the determination of the process and
of its extent. In the starting aminic complexes this metal fitting is
also quite relevant for demetalation–metalation reactions by the
second added metal ion but the shape and the coordinating ability
(enhanced in H3RB with respect to H2RA) favours the complete or
partial coordination of the incoming second metal ion.
ESI-MS study was carried out also on the mixtures resulting by
the addition of Ln(CH3COO)3ꢀnH2O (Ln = Ce, Gd, Yb) to [LuNa(LB)(-
Cl)] in order to understand the behaviour towards transmetalation
and demetalation reactions and to compare the resulting data with
those obtained from the reduced analogue. The width of the coor-
dinating chamber and the ionic radius of the lutetium(III) ion seem
to prevent transmetalation and metalation reactions and hence the
only significant peak in the ESI mass spectra is the one of
[LuNa(LB)]+ (m/z 714.1).
3.4.2. Sodium transmetalation by CaII, LiI and KI
As shown by the X-ray crystallographic investigation, in the
heterodinuclear LnNa complexes the sodium(I) ion resides in the
crown-like chamber because of its affinity for this set of oxygen
donors. In order to test the possible use of these systems as molec-
ular probes in the presence of these ions, it is important to evaluate
this affinity in comparison with other alkaline metal ions such as
CaII, LiI and KI.
The addition of gadolinium acetate to [LuNa(LB)(Cl)] was fol-
lowed also by NMR. The resulting 1H spectrum in CH3OH-d4 is
characterized by the broadening of the signals without any shift
of its position, thus indicating that there is a weak interaction
without complexation of the paramagnetic metal ion to the start-
ing complex, as ascertained also by ESI mass spectrometry (Fig. 4).
Similar ESI-MS measurements were carried out on methanol
solutions containing equimolar amounts of [LaNa(RB)(Cl)] and
Lu(CH3COO)3ꢀ6H2O, Y(CH3COO)3ꢀ3.5H2O or Gd(CH3COO)3ꢀnH2O.
The addition of Lu(CH3COO)3ꢀ6H2O gives rise to [LaLu(RB)(CH3-
COO)2]+ (m/z 952.2, 100%) while only traces of [LuNa(RB)]+ (m/z
718.4, 5%) and of [Lu2(RB)(CH3COO)2]+ are present at 0 and (m/z
988.2, 30%). The signal of [LaLu(RB)(CH3COO)2]+ after collision
gives rise to [LaLu(RB–H)(CH3COO)]+ (m/z 892.0) indicating the sta-
bility of the two metal ions in the coordinating moiety. The addi-
tion of Gd(CH3COO)3ꢀnH2O gives rise to the homodinuclear
complex [Gd2(RB)(CH3COO)2]+ (m/z 954.1) which looses one ace-
tate ion by collision. The heterodinuclear LaGd complex is present
in traces (<10%). The addition of Y(CH3COO)3ꢀ3.5H2O causes the
ESI-MS testifies that the addition of an equimolar amount of
CaCl2 to a methanol solution of [LuNa(RB)(CH3COO)]ꢀ2iPrOH leads
to a complete transmetalation and the ion [LuCa(RB)(Cl)]+ (m/z
770) is detected. The addition of an equimolar amount of LiCl gives
rise to [LuLi2(RB)(Cl)]+ (m/z 744.4) which yields [LuLi(RB)]+ (m/z
702.2) by collision. The signal of [LuK(RB)]+ (m/z 734.4) is detected
by mixing equimolar amounts of KBr and [LuNa(RB)(CH3-
COO)]ꢀ2iPrOH in methanol. [LuK(RB)]+ undergoes the loss of the
pendant arm by collision without loosing the dinuclearity. The for-
mation of the species [LuCa(RB)(Cl)]+ indicates a complete trans-
metalation of the sodium ion; the spectra arising by the addition
of LiCl or KBr indicate that more complex processes occur.
Although some signals are difficult to justify, the heterodinuclear
complexes LuLi and LuK, appear to be the most stable species as
indicated by collision induced fragmentation; however they are
not the only species as indicated by the presence of many other
signals. The transmetalation process of sodium by calcium, lithium
and potassium depends on the ionic radius of the transmetalating
ion (it has to fit well in the coordinating chamber), on the
Table 2
Transmetalation, demetalation and metalation processes followed studying the product ions by ESI mass spectrometry.
Starting
Product ions with relative abundances (CH3COOꢁ = X; Clꢁ = Z)
complexes
Y(III)
Ce(III)
Gd(III)
Yb(III)
Lu(III)
/
[LuNa(LB)(Z)]
[LuNa(RB)(X)]
No reaction
No reaction
No reaction
[LuYb(RB)(X)2]+
(100%)
[LuCe(RB)(X)2]+ (100%) [Ce2(RB)(X)2]+
(15%) [Lu2(RB)(X)2]+ (10%)
[LuNa(RB)(X)2]+
(10%)
[LaNa(LB)(Y)]
[YNa(LB)]+ (100%)
[YLa(X)(Z)]+ (45%)
[YLa(LB)(X)2]+ (25%)
[Ce(LB)+H+] (100%) [CeNa(LB)]+ (30%)
[Ce(H2–LB)(Z)]+ (20%) [Ce2(LB)(X)(Z)]+
(20%) [CeLa(LB)(X)2]+ (20%)
[Gd(LB)+H+]
(100%)
[LuNa(LB)]+ (100%) [LuNa(LB)(X)+H+] (95%)
[LuLa(LB)(X)(Z)]+ (25%) [Lu2(LB)(X)(Z)]+ (5%)
[LuLa(LB)(X)2(Z)+H+] (95%)
[Gd(LB)+H+]
(50%)
[LaNa(RB)(Y)] [Y2(RB)(X)2]+ (80%)
[LaY(RB)(X)2]+ (100%)
[Gd2(RB)(X)2]+
(100%)
[LaLu(RB)(X)2]+ (100%) [LuNa(RB)]+ (5%)
[Lu2(RB)(X)2]+ (30%)
[GdLa(RB)(X)2]+
(10%)

V. Peruzzo et al. / Inorganica Chimica Acta 416 (2014) 226–234
233
Fig. 4. 1H NMR in CH3OH-d4 of [LuNa(LB)(Cl)] before (a) and after (b) and (c) addition of equimolar amounts of Gd(CH3COO)3ꢀnH2O.
lanthanide(III) ion in terms of affinity towards the alkali or alkaline
earth metal ion (although a general trend was not found) and on
the experimental temperature. Calcium and sodium have similar
ionic radii, 0.99 and 0.97 Å, respectively, and probably they fit well.
Lithium and potassium, 0.76 and 1.38 Å, respectively, are probably
too small or too large to produce a complete transmetalation. The
results of a previous work [19,20] with similar complexes of H2LA
parallel those obtained with the reduced H3RB, this indicating that
the changes in the chamber hosting the lanthanide(III) ion (the
reduction and the addition of the pendant arm) does not dramati-
cally influence the transmetalation reaction occurring in the
crown-like compartment. Furthermore, mass spectrometry exper-
iments proved to be powerful and sensible tools to confirm the
results obtained by NMR spectroscopy without the need of high
solubility and high concentrations.
Acknowledgements
We thank Mr. A. Aguiari, and Mrs. A. Moresco for technical
assistance. The research was also supported by ‘‘Progetto d’Ateneo
2006’’ to FN.
Appendix A. Supplementary material
CCDC 945572 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at http://dx.doi.org/10.1016/
j.ica.2014.03.032.
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