A polyaromatic terdentate binding unit with fused 5,6-membered chelates for complexing s-, p-, d-, and f-block cations

Article abstract of DOI:10.1021/ic400526j

The polyaromatic terdentate ligand 6-(azaindol-1-yl)-2,2′-bipyridine (L7) combines one 5-membered chelate ring with a fused 6-membered chelate ring. It is designed to provide complexation properties intermediate between 2,2′;6′,2″-terpyridine (L1) (two fused 5-membered chelate rings) and 2,6-bis(azaindol-1-yl)pyridine (L6) (two fused 6-membered chelate rings). In polar organic solvents, L7 displays remarkable affinities for the successive fixation of two small univalent cations M = H⁺ or Li ⁺, leading to stable [M_m(L7)]^m+ (m = 1-2) complexes. Upon reaction with M = Mg²⁺ or Zn²⁺ cations, the large positive charge densities borne by the metals result in the successive cooperative complexation of two ligands to give [M(L7)_n] ⁿ⁺ (n = 1-2). For small Sc³⁺, unavoidable traces of water favor the formation of the protonated ligand at millimolar concentrations in acetonitrile, but the use of larger Y³⁺ cations leads to [Y(L7) _n]ⁿ⁺ (n = 1, 2), for which stability constants of log(β1,1Y,L7) = 2.9(5) and log(β1,2Y,L7) = 5.3(4) are estimated. The complexation behaviors are supported by speciations in solution, thermodynamic analyses, and solution and solid-state structures.

Full text of DOI:10.1021/ic400526j

Article
pubs.acs.org/IC
A Polyaromatic Terdentate Binding Unit with Fused 5,6-Membered
Chelates for Complexing s‑, p‑, d‑, and f‑Block Cations
Thi Nhu Y Hoang,*,† Marie Humbert-Droz,† Thibault Dutronc,† Laure Guenee,‡ Celine Besnard,‡
́
́
́
and Claude Piguet*,†
†Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4,
Switzerland
‡Laboratory of Crystallography, University of Geneva, 24 quai E. Ansermet, CH-1211 Geneva 4, Switzerland
S
* Supporting Information
ABSTRACT: The polyaromatic terdentate ligand 6-(azaindol-1-yl)-2,2′-bipyridine (L7)
combines one 5-membered chelate ring with a fused 6-membered chelate ring. It is designed
to provide complexation properties intermediate between 2,2′;6′,2″-terpyridine (L1) (two
fused 5-membered chelate rings) and 2,6-bis(azaindol-1-yl)pyridine (L6) (two fused 6-
membered chelate rings). In polar organic solvents, L7 displays remarkable affinities for the
successive fixation of two small univalent cations M = H+ or Li+, leading to stable
[Mm(L7)]m+ (m = 1−2) complexes. Upon reaction with M = Mg2+ or Zn2+ cations, the
large positive charge densities borne by the metals result in the successive cooperative
complexation of two ligands to give [M(L7)n]n+ (n = 1−2). For small Sc3+, unavoidable
traces of water favor the formation of the protonated ligand at millimolar concentrations in
acetonitrile, but the use of larger Y3+ cations leads to [Y(L7)n]n+ (n = 1, 2), for which stability constants of log(β1Y,,1L7) = 2.9(5)
and log(βY1,,2L7) = 5.3(4) are estimated. The complexation behaviors are supported by speciations in solution, thermodynamic
analyses, and solution and solid-state structures.
stability is improved by 5 orders of magnitude (log(βL1,n1,L1) =
INTRODUCTION
■
7.5−7.7), but the size-discriminating effects are leveled out.5h
Molecular mechanics have established that aliphatic 5-
membered chelate rings were geometrically adapted for
catching large cations, whereas six-membered analogues
To the best of our knowledge, only the third successive
thermodynamic constants K1L,3n,L5, transforming [Ln-
(L5)2(CH3CN)3]3+ into [Ln(L5)3]3+, display some noticeable
matched smaller metals (see Figure S1 in the Supporting
Information).1 In order to improve structural control and light-
size selectivity along the lanthanide series. These constants
decrease by 3 orders of magnitude in going from Ln = Gd(III)
to Lu(III), because of the steric constraints produced by the
helical wrapping of the three strands in the final complexes.5t,9d
With this in mind, we suspect that the large distortion of the
polyaromatic backbone detected upon meridional ter-coordi-
nation of L6 (fused 6,6-membered chelate) to Zn(II)10 or
Cu(II),11 compared with the coplanar arrangement found for
L1 (fused 5,5-membered chelate) in [Zn(L1)Br2],12 could
produce unusual thermodynamic effects. Along this line of
reasoning, we note that L6 indeed reacts with YI3 under
anhydrous conditions to give [Y(L6)n]3+ (n = 1, 2), despite its
claimed reluctance for large cations; however, the extreme
sensitivity of these complexes to moisture and their low
solubility prevent further investigations.10 Pushing forward this
strategy, we report here on the preparation of the unsym-
metrical terdentate aromatic ligands L7, which are made of a 5-
membered bipyridine chelate fused with a 6-membered
pyridine-azaindole ring,13 and we also explore its complexation
properties with spherical cations possessing various Z2/R
harvesting properties, aromatic rings were incorporated into the
chelating ligands and numerous large tervalent lanthanide
cations, Ln(III), acting as luminescent2 or magnetic3 probes,
were successfully coordinated not only with 5-, but also with 6-
or even with 7-membered polyaromatic chelates, in contra-
diction with the original rule of thumb.2 However, we note that
6- and 7-membered chelates, which are geometrically poorly
adapted for large Ln(III), systematically relied on negatively
charged ligands in order to benefit from the considerable
entropic driving force produced by the charge neutralization
accompanying the complexation process in polar solvents.1b,4
For neutral polyaromatic terdentate ligands, only fused 5-
membered chelates are known to give stable complexes with
tervalent Ln(III), among which the terdentate ligands L1,5 L2,6
L3,7 L4,8 and L59 are the archetypes (see Scheme 1).
Beyond the investigation of these neutral soft receptors for
the selective extraction of actinides over lanthanides in acidic
nuclear wastes, only slight interest was focused on their
potential selectivity along the lanthanide series. For terpyridine
L1, the fixation of the first binding unit gives moderately stable
[Ln(L1)(H2O)n]3+ complexes in water, whose formation
constants stepwise increase along the series (log(βL1,n1,L7) =
2.08−2.80 for Ln = La, Eu, Lu).5r In less-polar acetonitrile, the
Received: March 1, 2013
© XXXX American Chemical Society
A
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Scheme 1. Chemical Structures of the Terdentate
Polyaromatic Ligands L1−L7 in Their Relaxed trans−trans
Conformations
Scheme 2. Synthesis of Ligand L7 with Numbering Scheme
for NMR Data
NMR time scale with end points for M:L7 = 1.0 and 2.0, in
agreement with the formation of the [ML7]+ and [M2(L7)]2+
complexes detected by ESI-MS in the gas phase (see Table S3
in the Supporting Information). The complete set of
dynamically average chemical shifts can be satisfyingly fitted
to eqs 1 and 2, using nonlinear least-squares techniques, to give
log(β1M,1,L7) and log(β2M,1,L7) (Table 1),16 ligand distributions
(Figure 1 and Figure S6 in the Supporting Information) and
individual 1H NMR spectra (see Figure 2, as well as Figure S7,
Table S1, and Table S2 in the Supporting Information).
M,L7
M+ + L7 ⇌ [ML7]+
β
1,1
(1)
M,L7
2M+ + L7 ⇌ [M2L7]2+
β
2,1
electrostatic factors (Z is the charge of the cation in
electrostatic units and R is its ionic radius).
(2)
M,L7
m,1
As expected, the formation constants β
are reduced by a
RESULTS AND DISCUSSION
factor of 5−10 in pure CD3CN, because of the larger solvation
of the free cations in a more polar solvent. Compared with L1
(log(β1H,1,L1) = 3.4(1) and log(β2H,1,L1) = 5.3(3)) and with L6
(log(β1H,1,L6) = 5.3(3) and log(β2H,1,L6) = 8.9(3)) in CD3CN/
CDCl3 (1:1),10 L7 displays the largest affinity for protons
(log(βH1,1,L7) = 5.7(1) and log(β2H,1,L7) = 9.5(5)), together with
non-negligible formation constants with Li+, for which L1 and
L6 exhibited nonmesurable stability constants at millimolar
■
Synthesis of Ligand L7, and Complexation with
Univalent H+ and Li+ Cations. The terdentate ligand L7 is
obtained in two steps from 2-(tributylstannyl) pyridine (1)
with a 47% global yield (see Scheme 2). The initial Stille
coupling reaction uses commercially available 2,6-dibromopyr-
idine to give 6-bromo-2,2′-bipyridine (2),14 which is trans-
formed to L7 via a catalyzed Ullmann-type coupling reaction
with 7-azaindole.15 The 12 aromatic H NMR signals of L7
concentrations. The careful analysis of the individual H NMR
1
1
(see Figure 2 and Figures S2−S5 in the Supporting
Information) are compatible with an average planar Cs
symmetry, where the distal N atoms adopt trans−trans
conformations, with respect to the nitrogen of the central
pyridine ring, as shown in Scheme 2. The low-field resonances
of H2−H3 and H8−H9 pairs are diagnostic for their location
close to the electronegative N atoms of the adjacent
heterocyclic ring (see Tables S1 and S2 in the Supporting
Information), while the lack of a nuclear Overhauser enhance-
ment effect between the H atoms of each hydrogen pair
precludes cis−cis geometry.
spectra gives pertinent structural information. Upon titration
with H+, the concomitant downfield shift of the signals of H2,
H3, and H5 indicates a decrease in electronic density upon
protonation, but the trans conformation of the azaindol-
pyridine unit is not seriously affected by the fixation of the first
proton in [HL7]+ (red arrows in Figure 2).
In contrast, the upfield shift of H8 (−0.15 ppm) points to a
cis conformation of the 2,2′-bipyridine unit in [HL7]+, because
H8 is no more influenced by the N atom of the adjacent
pyridine ring,10 while the concomitant downfield shift of H10
(0.73 ppm) demonstrates that protonation occurs on the distal
pyridine ring (blue arrows in Figure 2).17 The second
protonation occurs at the azaindol ring and leads to a twisted
cis−cis conformation for the terdentate ligand in [H2L7]2+.
With M = Li+, the concomitant downfield shift of the signals of
1H NMR titrations of L7 in CD3CN/CDCl3 (1:1) or in
CD3CN with CF3SO3H (Figures S2 and S3 in the Supporting
Information) or with LiClO4 (Figures S4 and S5 in the
Supporting Information) exhibit fast-exchange processes on the
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Figure 1. Computed ligand speciation (mole fraction (%) of the ligand
in the various species) for the titrations of L7 with (a) CF3SO3H and
(b) LiClO4 in CD3CN/CDCl3 (1:1) at 298 K. Total ligand
concentration |L7|tot = 7.5 × 10−3 M.
H2−H3 and of H8−H9 in [LiL7]2+ implies a cis−cis
conformation for the ligand upon fixation of the first Li+
cation. The affinity for a second Li+ cation remains modest
and does further significantly affect the 1H NMR spectrum (see
Figure 2 and Figure S7 in the Supporting Information).
X-ray crystal structures solved for [HL7](CF3SO3) (3),
[H2L7](ClO4)2 (4), and [Li(L7)(ClO4)(H2O)] (5) confirm
the solution data with the coordinated polyaromatic terdentate
unit adopting coplanar trans−cis [HL7]+, twisted cis−cis
[H2L7]2+, and coplanar cis−cis [LiL7]+ conformations (see
Figure 3, as well as Figure S8 and Tables S4−S13 in the
Supporting Information). The protonated cations [HL7]+ and
[H2L7]2+ are involved in weak intramolecular and intermo-
lecular hydrogen bonds in the crystals of 3 and 4 (see Tables S7
and S10 in the Supporting Information). In 5, the univalent Li
metal displays standard Li−N distances18 and its coordination
sphere is completed with one water molecule and one
unidentate perchlorate counteranion to give the five-coordi-
nated pseudo-trigonal bypyramidal complex [Li(L7)(ClO4)-
(H2O)].19 Taking the molecular structures of cis−cis [H2L7]2+
as a rough model for the meridional ter-coordination of this
ligand around multivalent cations, we conclude that the shape
of the irregular triangle drawn by the three donor N atoms
(Figure 4) is intermediate between the pseudo-isosceles
triangles reported for [H2L1]2+ (adapted for large cations)20
and [H2L6]2+ (adapted for small cations).10
C
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1
Figure 2. Computed individual H NMR spectra for L7 (middle), [HL7]+ and [H2L7]2+ (top), and [LiL7]+ and [Li2L7]2+ (bottom) in CD3CN/
CDCl3 (1:1) with associated solution structures. Red arrows highlight diagnostic variations in the chemical shifts for establishing the conformation of
the azaindol-pyridine unit, whereas blue arrows hold for the bipyridine unit (see text).
Within the frame of the site-binding approach,22 the
cumulative formation macroconstants (eqs 1 and 2) can be
modeled with eqs 3 and 4, respectively.
thermodynamic descriptions into free energies of connection
M,L7
ΔG
= −RT ln(f NM,L7), which include desolvation
connect, Ni
i
processes (the standard concentration of the reference state is
M,M
L7
M,M/RT)
L7
set to 1 M).24 Finally, u
= e−(ΔE
is the Boltzmann
M,L7
β
=
ω1H,1,(LN7)f M,L7
∑
1,1
N
i
i
factor correcting for the free energy of connection for any
(3)
i
intramolecular M···M interactions resulting from the close
location of the two cations in [M2L7]2+. Assuming that the
M,L7
β
=
ω2M,1,(LN7N)(f M,L7 )(fNM,L7 )uM,M
N
∑
L7(NN)
2,1
i
j
i j
M,L7
i
j
affinity of distal and central N donors are identical (f
=
N‑central
i≠j
(4)
M,L7
M,L7
f
= f
), the application of eqs 3 and 4 provides eqs 5
N‑distal
connect
and 6 for M = H+ (see Figures S9 and S10 in the Supporting
Information) and eqs 7 and 8 for M = Li+ (see Figure S11 in
the Supporting Information), from which pertinent microscopic
thermodynamic descriptions can be computed (see Table 1,
entries 3−6).25
In these equations, the sums run over all microspecies
possessing the same stoichiometry but differing by the precise
location of the metallic cations bound to each specific nitrogen
atom Ni (and Nj) in ligand L7. ω
M,L7
takes into account the
m,n
pure statistical (i.e., entropic) contribution due to change in
molecular rotational entropies occurring upon complexation for
each microspecies.23 Once the point group of each partner
H,L7
H,L7
β
β
= 2f
connect
(5)
(6)
(7)
1,1
M,L7
m,n
contributing to eqs 1 and 2 is at hand, ω
are easily
computed using the method of symmetry numbers (see Figures
H,L7
2,1
H,L7
connect
H,H
)2u
L7
S9 and S10 in the Supporting Information). f MN,L7 corresponds
= 2(f
i
to the absolute affinities of the Ni atom of the heterocyclic
aromatic ring involved in the coordination of the cation.
Application of the van’t Hoff isotherm transforms these
Li,L7
1,1
Li,L7
β
= 12f
connect
D
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The free energy of connection is much larger for the H+
cation than for the Li+ cation, because of the increase in size,
which reduces the electrostatic factor to Z2/R = 2.8 eu/Å for
five-coordinated Li(I).26 Interestingly, the unsymmetrical fused
5,6-membered chelate ligand L7 displays the largest affinity for
H,L7
small univalent cation (ΔG
= −30.8(6) kJ/mol and
connect
ΔGcLoi,nLn7ect = −13.2.(1.1) kJ/mol) compared with L1 (fused 5,5-
H,L1
Li,L1
membered chelates, ΔG
= −16.7(6) kJ/mol and ΔG
connect
H,L6
connect
> −5 kJ/mol) and L6 (fused 6,6-membered chelates, ΔG
connect
= −27.5(1.7) kJ/mol and ΔG
> −5 kJ/mol).10 The
Li,L6
connect
successive protonations of L1, L6, and L7 follow anticooper-
M,M,Lk
interaction
ative protocols with a reluctance of 6 < ΔE
< 9 kJ/mol
for the fixation of the second proton, while multilithiation in
[Li2L7]2+ is statistically within experimental uncertainties.
Complexation of L7 with Bivalent Mg2+ and Zn2+
Cations. Electron spin ionization−mass spectroscopy (ESI-
MS) titrations of L7 with M2+ cation in acetonitrile show the
initial formation of [M(L7)]2+ ([Mg(L7)(CH3CN)]2+ at m/z =
168.0 and [Zn(L7)]2+ at m/z = 169.4), followed by the fixation
of a second ligand to the divalent metal to give saturated
[M(L7)2]2+ complexes ([Mg(L7)2]2+ at m/z = 284.0 and
1
[Zn(L7)2]2+ at m/z = 304.6). H NMR titrations recorded in
CDCl3:CD3CN or in CD3CN operate under intermediate (M =
Mg; see Figure S12 in the Supporting Information) or slow (M
= Zn, Figure S13 in the Supporting Information) exchange rate
on the NMR time scale, which easily demonstrate that L7,
[ML7]2+, and [M(L7)2]2+ are the only ligand-containing
species. Integration of the 1H NMR signals of the same proton
in the different species provides quantitative speciations, from
which the macroscopic stability constants for eqs 9 and 10 are
deduced (see Table 1, columns 7−10, as well as Appendix I in
the Supporting Information), together with ligand distributions
(see Figure 5 and Figure S14 in the Supporting Information)
and individual 1H NMR spectra (see Figure 6, as well as Figures
S15 and S16 and Tables S1 and S2 in the Supporting
Information). For M = Mg2+, the considerable broadening of
the signal at 298 K forced us to solve the speciations at 253 and
263 K (see Figures S17−S19 and Table S14 in the Supporting
Information), from which the formation constants at 298 K
collected in Table 1 were estimated by using linear van’t Hoff
Figure 3. Perspective views (a) perpendicular and (b) parallel to the
central pyridine ring of the molecular structures of [HL7]+, [H2L7]2+
and [Li(L7)(OH2)(ClO4)] observed in the crystal structures of
[HL7](CF3SO3) (3), [H2L7](ClO4)2 (4) and [Li(L7)(ClO4)(H2O)]
(5). Color code: gray = C, blue = N, orange = H, violet = Li.
Hydrogen atoms are omitted for [Li(L7)(OH2)(ClO4)].
Mg,L7
Mg,L7
plots with ln(β1M,ng,L7) = −(ΔH
)/RT + (ΔS
)/R
1,n
1,n
Mg,L7
Mg,L7
(ΔH
and ΔS
are gathered in Table S14 in the
Supporting Information).
1,n
1,n
M,L7
M
2+ + L7 ⇌ [ML7]2+
β
1,1
(9)
M,L7
M
2+ + 2L7 ⇌ [M(L7)2]2+
β
(10)
1,2
The complexation of L7 with either Mg2+ or Zn2+ is similar
and shows the stepwise meridional tercoordination of two
terdentate ligands to give the dynamically average Cs-sym-
metrical [M(L7)]2+ and C2-symmetrical [M(L7)2]2+ complexes
on the NMR time scale. The systematic upfield shifts of H2, H3
and H9 are diagnostic for the transformation of the original
trans−trans into cis−cis conformation for L7 upon complex-
ation, while the global downfield shifts of the protons bound at
the para position of the pyridine rings (H1, H5 and H10) point
to the complexation of the three N-donors to M2+ (see Figure 6
and Figures S15 and S16 in the Supporting Information).17 It is
worth noting here the unusual, but expected, upfield shifts by
more than 1.0 ppm for H7 and H12 in [M(L7)2]2+, which
results from the location of these protons in the shielding
Figure 4. Geometries of the triangles formed by the donor N atoms in
the molecular structures of (a) [H2L1]2+,20 (b) [H2L7]2+, and (c)
[H2L6]2+.10
Li,L7
Li,L7
connect
Li,Li
)2u
L7
β
= 144(f
(8)
2,1
E
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(CF3SO3)2·0.13H2O (8). Each terdentate ligand is meridionally
coordinated to the central cation in agreement with the
solution structures deduced by NMR (see Figure 7, as well as
Figure S20 and Tables S15−S21 in the Supporting
Information). The bivalent metals are six-coordinated in
pseudo-octahedral environments as found for analogous
[Mg(L1)(OH2)3]Cl2,27 [Zn(L1)(S)X2]28 and [Zn(L1)2]X2
complexes.29 However, the adjacent five- and six-membered
chelates in L7 (instead of fused 5,5-membered chelates in L1)
induces 15−20° helical twists along the polyaromatic strand in
6 and 7 as similarly observed for [Li(L7)(ClO4)(H2O)] (5), a
distortion raised to 35°−45° in [Zn(L7)2]2+, whereas the
coordinated L1 ligands in [Zn(L1)2]2+ are essentially planar
(Figure 7 and Figure S21 in the Supporting Information).29
The average Mg−N and Zn−N bond distances are comparable
for complexes with L1 and L7, but their specific distributions
are different. With fused 5,5-membered chelates in L1, M(II) is
located closer to the central pyridine ring (for instance Mg−
Npycentral = 2.12 Å, Mg−Npydistal = 2.20 Å in [Mg(L1)-
(OH2)3]2+), whereas fused 5,6-membered chelate rings in L7
put M(II) at a remote distance from the central pyridine
nitrogen donor atom, while the distal M−N interactions are
shortened (Mg−Npycentral = 2.20 Å, Mg−Npydistal = 2.13 Å ≈
Mg−Nazadistal = 2.12 Å in [Mg(L7)(OH2)3]2+).13a This effect is
further amplified when two fused 6,6-membered chelate rings
are coordinated to Zn(II) as reported for [Zn(L6)(CF3SO3)2]
(Zn−Npycentral = 2.25 Å, Zn−Nazadistal = 2.00 Å).10
The thermodynamic analysis of eqs 9 and 10 within the
frame of the site-binding model22 gives eqs 11 and 12 (see
Figure S22 in the Supporting Information), from which the
Figure 5. Computed ligand speciation (mole fraction (%) of the ligand
in the various species) for the titrations of L7 with (a) Mg(ClO4)2 and
(b) Zn(CF3SO3)2 in CD3CN/CDCl3 (1:1) at 298 K. Total ligand
concentration |L7|tot = 7.5 × 10−3 M.
M,L7
L7,L7M
microscopic describers ΔG
and ΔE
are computed
connect
interaction
(see Table 1, entries 3−6).
M,L7
M,L7
β
β
= 24f
connect
(11)
(12)
domain of the pyridine ring of the adjacent ligand (see Figure 6,
top).
X-ray crystal structures were solved for [Mg(L7)(OH2)3]-
(ClO4)2 (6), [Zn(L7)(THF)(CF3SO3)2] (7) and [Zn(L7)2]-
1,1
M,L7
1,2
M,L7
= 24(f
)2uML7,L7
connect
Figure 6. Computed individual 1H NMR spectra for L7, [Zn(L7)]+, and [Zn(L7)2]2+ in CD3CN/CDCl3 (1:1) with associated solution structures.
Red arrows highlight chemical shifts variations diagnostic for establishing the conformation of the azaindol-pyridine unit, whereas blue arrows hold
for the bipyridine unit (see text).
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[HL7]+ and [H2L7]2+ produced by the severe hydrolysis of
small Sc3+ with a trace of water, according to eq 13 (six-
CN=6
coordinate ionic radius R
= 0.75 Å and pK1a,Sc =10−4.55 in
Sc
water; see Figure S23 in the Supporting Information).26,30
3+ + H2O ⇌ [M(OH)]2+ + H+ Ka1,M
M
(13)
In order to minimize water content, Sc(CF3SO3)3 was
replaced with anhydrous ternary complexes [La-
(hfac)3(diglyme)]31 and [Y(CF3SO3)3(diglyme)]32 containing
larger La3+ (nine-coordinate ionic radius R
= 1.36 Å, pK1a,La
CN=9
La
=10−9.01 in water, hfac = hexafluoroacetylacetonate) and Y3+
cations (RCYN=9 = 1.08 Å, pK1a,Y =10−8.81 in water).26,30 Titration
of L7 with [La(hfac)3(diglyme)] at millimolar concentrations
in CD3CN displays only weak interactions and |La|tot/|L7|tot
ratios larger than 5.0 are required for recording reliable changes
1
in the H NMR spectra (see Figure S24 in the Supporting
Information).
The situation is different with [Y(CF3SO3)3(diglyme)], for
which significant quantities of [Y(L7)]3+ and [Y(L7)2]3+ (slow
exchange on the NMR time scale) are formed together with
comparable amounts of protonated ligands [HL7]+ and
[H2L7]2+ (fast exchange on the NMR time scale; see Figure
S25 in the Supporting Information). The complete titration
process can be satisfyingly modeled in CD3CN by simulta-
neously considering eqs 1, 2, 9, 10, and 13, adapted for M = Y3+
(eqs 14−18), together with eq 19 for taking into account partial
water dissociation in pure acetonitrile.33 The fitting process
used multi-Lorentzien deconvolutions of the complete 1H
NMR spectra, and it converged to log(βY1,,1L7) = 2.9(5) and
log(βY1,,2L7) = 5.3(4) with the ligand distribution depicted in
Figure 8 (see Appendix 2 in the Supporting Information).
H,L7
H+ + L7 ⇌ [HL7]+
β
= 105.3
(14)
(15)
(16)
(17)
1,1
H,L7
2H+ + L7 ⇌ [H2L7]2+
Y3+ + L7 ⇌ [YL7]3+
Y3+ + 2L7 ⇌ [Y(L7)2]3+
β
= 109.1
Figure 7. Perspective views of the molecular structures of (a)
[Mg(L7)(OH2)3]2+, (b) [Zn(L7)(THF)(CF3SO3)2], and (c) [Zn-
(L7)2]2+ observed in the crystal structures of [Mg(L7)(OH2)3]-
(ClO4)2 (6), [Zn(L7)(THF)(CF3SO3)2] (7), and [Zn(L7)2]-
(CF3SO3)2·0.13H20 (8). Color code: gray = C, blue = N, red = O,
yellow = S, light blue = F, green = Mg, pink = Zn. Hydrogen atoms are
omitted for clarity.
2,1
Y,L7
β
1,1
Y,L7
1,2
β
Y3+ + H2O ⇌ [Y(OH)]2+ + H+
Ka1,Y = 10−8.81
Since the ionic radius of six-coordinate Mg2+ (0.72 Å) and
(18)
(19)
Zn2+ (0.74 Å) are comparable,26 their affinity for L7 is similar
H2O ⇌ OH− + H+ Ks = 10−16.35
M,L7
connect
with ΔG
≈ −15 kJ/mol in CDCl3:CD3CN (1:1), a value
reduced by 20%−30% in more-polar CD3CN. Surprisingly, the
free energy of connection increases only slightly when going
from M = Li+ to Mg2+, despite the doubling of both positive
charge and electrostatic factor. This suggests that solvation
processes play a major role in the complexation reactions
According to the complicated speciation observed in
solution, the isolation of pure yttrium complexes is difficult,
but brownish X-ray quality crystals of [Y(L7)2Cl2]I3·CH2Cl2
(9) slowly deposited during the air evaporation of a CH3CN/
CH2Cl2 (1:8) solution containing YI3(THF)3.5 (1 equiv)34 and
L7 (2 equiv; see Figure 9, as well as Figures S26 and S27, in
addition to Tables S22−S24 in the Supporting Information).35
The 8-coordinated Y(III) metal in the [Y(L7)2Cl2]+ cation is
sandwiched between the two twisted terdentate ligands, with
the two Cl− anions completing a pseudo-square antiprism
(Figure 9). The Y−N bond distances (2.462−2.613 Å, average
2.54(7) Å) are similar to those reported for [Y(L1)-
(OH2)4Cl]2+ (8-coordinate: 2.52(3) Å),36 [Y(L1)-
(OH2)2(NO3)2]+ (9-coordinate: 2.49(2) Å)37 and [Y(L1)3]3+
(9-coordinate: 2.52(3) Å).38 However, the yttrium atom, which
is located within the plane defined by the three coordinated
donor N atoms for complexes with L1, lies at 1.187 and 1.197
Å from the related coordination planes in [Y(L7)2Cl2]+ (Figure
occurring in polar organic solvents, a statement substantiated
M,L7
by the enthalpy-penalized (ΔH
> 0), but entropy-driven
1,n
Mg,L7
complexation processes (ΔS
≫ 0) revealed by vant’ Hoff
1,n
plots for Mg2+ (see Table S14 in the Supporting Information).
We also notice that the fixation of the second terdentate ligand
in [M(L7)2]2+ is much more favorable for Mg2+ (positive
L7,L7M
cooperativity ΔE
≈ −15 kJ/mol), while a rough
interaction
statistical behavior is found for Zn2+, but the large uncertainties
affecting this parameter for M = Mg prevent more-detailed
interpretations.
Complexation of L7 with Trivalent Sc3+, La3+, and Y3+
Cations. Titration of L7 with hygroscopic Sc(CF3SO3)3 in
CD3CN shows the exclusive formation of the protonated ligand
G
dx.doi.org/10.1021/ic400526j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
chelates (see Figure S1 in the Supporting Information),1 The
intermediate structural characteristics provided by L7 (i.e., two
fused 5,6-membered chelates) remove this effect in polar
organic solvents. The terdentate ligand L7 indeed efficiently
reacts with H+ (ΔG
≈ −30 kJ/mol), and it displays
H,L7
connect
M,L7
significant affinities for M = Li+, Mg2+, Zn2+, and Y3+ (ΔG
connect
≈ −15 kJ/mol to −10 kJ/mol) without exhibiting pertinent
dependence on the cationic electrostatic factors Z2/R. Under
these conditions, the use of easily hydrolyzed cations such as
Sc3+ or Y3+, in the presence of a trace of water, leads to
unavoidable competition with protonation. Structurally speak-
ing, this rough invariance of the affinity for various cations is
correlated with their close interactions with the two distal
donor N atoms, while the central N atom is remote. The
opposite situation occurs for coordinated L1, which better
encapsulates the incoming cations, thus optimizing enthalpic
contributions. Therefore, it is not so suprising that the fixation
of Mg2+ to L7 proved to be strictly entropy-driven with
deleterious positive enthalpic contributions. This limitation
could be overcome by using less-coordinating anhydrous
organic solvents, as suggested by the systematic increase in
binding affinity observed upon going from CH3CN to
CH3CN:CDCl3 (1:1), and cyclic ethers are currently
investigated for pushing this strategy forward. We finally note
that the successive fixation of two monovalent cations to L7 is
anticooperative, but the alternative binding of two ligands L7 to
a single bivalent or tervalent cation may be driven by
remarkable positive cooperativities.
Figure 8. Computed ligand speciation for the titrations of L7 with
[Y(CF3SO3)3(diglyme)] in CD3CN at 298 K. Total ligand
concentration |L7|tot = 7.5 × 10−3 M.
Figure 9. Perspective views (a) perpendicular and (b) parallel to the
central pyridine ring of the terdentate ligands in the molecular
structure of [Y(L7)2Cl2]+ observed in the crystal structure of
[Y(L7)2Cl2]I3·CH2Cl2 (9). Color code: gray = C, blue = N, green =
Cl, yellow = Y. Hydrogen atoms are omitted for clarity.
EXPERIMENTAL SECTION
■
Chemicals were purchased from Strem, Acros, Fluka AG, and Aldrich,
and used without further purification, unless otherwise stated.
10,34
La(hfac)3·diglyme,31 Y(CF3SO3)3·diglyme32 and YI3(THF)3.5
were prepared according to literature procedures. Silicagel plates
Merck 60 F254 were used for thin layer chromatography (TLC) and
Fluka silica gel 60 (0.04−0.063 mm) or Acros neutral activated
alumina (0.050−0.200 mm) was used for preparative column
chromatography.
9). This specific geometry is not the simple result of using 6-
membered polyaromatic chelate rings, since a strictly planar
YN3 core was recently reported for the complexation of a
terdentate carbazole-bis(oxazoline) ligand possessing two fused
6,6-membered chelate rings.39 We however note the operation
of various intramolecular and intermolecular π-stacking
interactions in [Y(L7)2Cl2]+, which could contribute to the
stabilization of the observed sandwich conformation (see
Figure S27 in the Supporting Information). The thermody-
namic analysis of eqs 16 and 17 within the frame of the site-
binding model22 gives eqs 20 and 21 (Figure S28 in the
Preparation of 2-(tributylstannyl) Pyridine (1). n-BuLi (8 mL,
1.6 M in hexane, 12.5 mmol) was added dropwise to a solution of 2-
bromo pyridine (1.99 g, 12.5 mmol) in dry THF (5 mL) at −78 °C,
and the mixture was stirred for 1 h. Tributyltin chloride (3.4 mL, 12.65
mmol) was quickly added to the solution at −78 °C, and stirring
continued for 3 h at −78 °C, then 30 min at room temperature. The
reaction was quenched with saturated aqueous NH4Cl solution (10
mL) and extracted with ethylacetate (3 × 25 mL). The combined
organic layers were washed with brine, then water and finally dried
over anhydrous Na2SO4. The solvent was evaporated under reduced
pressure to give 2.7 g of 2-(tributylstannyl) pyridine (1, 12.5 mmol,
yield = 99%) as a dark brown liquid.
Supporting Information), from which we can calculate a
Y,L7
microscopic free energy of connection of ΔG
=
connect
−12.1(2.9) kJ/mol for a noncooperative complexation process
in CD3CN; this is a behavior very similar to that previously
described for Zn2+ (Table 1, entries 3−6), but much less
1H NMR (CDCl3, 400 MHz): δ (ppm) 8.74−8.72 (m, 1H); 7.49
(dt, 1H); 7.40 (m, 1H); 7.09−7.13 (m, 1H); 1.57 (t, 6H,); 1.30−1.35
(m, 6H); 1.10−1.14 (m, 6H); 0.88 (t, 9H). ESI-MS m/z: 370.18 [M
+H]+.
Y,L1
Y,L5
connect
efficient than ΔG
≈ ΔG
= −30(3) kJ/mol reported
connect
for terdentate-fused 5,5-membered chelates in acetonitrile.2f
Y,L7
Y,L7
β
β
= 6f
connect
Preparation of 6-bromo-2,2′-bipyridine (2). 2-(tributylstannyl)
pyridine (1) (3.8 g, 10.32 mmol) was added to a degassed solution of
2,6-dibromo pyridine (2.6 g, 10.97 mmol) and Pd(PPh3)4 (608 mg,
0.53 mmol) in toluene (4 mL). The mixture was refluxed under an
inert atmosphere for 12 h, the solvent evaporated and the resulting
residue disolved in CH2Cl2 (10 mL). Extraction with 6 M aq HCl (3 ×
10 mL) provided an aqueous layer, which was carefully neutralized
with 10% aq ammonia (60 mL) at 0 °C, then extracted with
dichloromethane (3 × 30 mL). The combined organic layers were
washed with water and dried over anhydrous Na2SO4. The solvent was
evaporated and the resulting solid residue was purified by column
chromatography (CH2Cl2/MeOH: 99.5/0.5 → 99/1) yielded 1.3 g of
(20)
(21)
1,1
Y,L7
1,2
Y,L7
= 6(f
)2uYL7,L7
connect
CONCLUSION
■
The coordination chemistry of the semirigid polyaromatic
terdentate ligands L1 (fused 5,5-chelates)5r and L6 (fused 6,6-
chelates)10 follows the geometrical rules established during the
1990s claiming that 5-membered chelate rings prefer large
cations, whereas the reverse situation holds for 6-membered
H
dx.doi.org/10.1021/ic400526j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
6-bromo-2,2′-bipyridine (2, 5.5 mmol, yield = 53%) as a white solid.
1H NMR (CDCl3, 400 MHz): δ (ppm) 8.69 (m, 1H); 8.43 (td, 1H, 3J
= 8.0 Hz); 8.40 (dd, 1H, J = 7.6 Hz, J = 0.8 Hz); 7.84 (dt, 1H, J =
7.6 Hz, 4J = 2 Hz); 7.69 (t, 1H, 3J = 8.0 Hz); 7.51 (dd, 1H, 3J = 8.0 Hz,
4J = 0.8 Hz); 7.35 (m, 1H). ESI-MS, m/z: 235.1 [M+H]+.
acetonitrile (0.5 mL). The slow diffusion of tetrahydrofuran (THF),
followed by filtration and drying, afforded 12 mg [ZnL7](CF3SO3)2
(0.019 mmol, yield 51%) as a white microcrystalline powder. Slow
diffusion of THF into a concentrated solution containing L7 (1 equiv)
and Zn(CF3SO3) (1 equiv) in CH3CN gave X-ray quality prisms of
[Zn(L7)](CF3SO3)2 (7). 1H NMR (CD3CN, 400 MHz): δ 9.04 (d, 3J
= 6 Hz, 1H); 8.78 (dd, 3J = 5.4 Hz, 4J = 1.4 Hz, 1H); 8.60 (td, 3J = 7.3
Hz, 1H); 8.50 (dd, 3J = 7.8 Hz, 4J = 1.5 Hz, 1H); 8.44 (t, 3J = 7.7 Hz,
3
4
3
Preparation of 6-(azaindol-1-yl)-2,2′-bipyridine (L7). 6-
Bromo-2,2′-bipyridine (866 mg, 3.6 mmol), 7-azaindole (390 mg,
3.30 mmol), K2CO3 (993 mg, 7.2 mmol), trans-1,2-diaminocyclohex-
ane (41 mg, 0.36 mmol), and CuI (35 mg, 0.18 mmol) in dioxane (10
mL) were degassed with N2 for 30 min. The mixture was then refluxed
under an inert atmosphere for 72 h. The solvent was evaporated, and
the resulting brown residue was extracted with CH2Cl2 (3 × 40 mL)
and washed with water. The organic layer was dried over MgSO4, and
the solvent was evaporated under reduced pressure. The resulting solid
was purified by column chromatography (CH2Cl2/MeOH: 99/1) to
yield 787 mg of 6-(azaindol-1-yl)-2,2′-bipyridine (L7, 2.9 mmol, yield
= 87%) as a white solid. 1H NMR (CDCl3, 400 MHz): δ 9.02 (dd, 1H,
3J = 8.2 Hz, 4J = 0.8 Hz); 8.73 (m, 1H); 8.60 (d, 1H, 3J = 3.6 Hz); 8.53
3
3
1H); 8.42 (dt, J = 7.7 Hz, 4J = 2 Hz, 1H); 8.40 (dt, J = 7.6 Hz, 4J =
1.6 Hz, 1H); 8.27 (d, 3J = 4.1 Hz, 1H); 8.09 (dd, 3J = 7.7 Hz, 4J = 1.6
3
4
5
Hz, 1H); 7.93 (ddd, J = 7.7 Hz, J = 5.3 Hz, J = 1.0 Hz, 1H); 7.68
3
4
3
(dd, J = 7.8, J = 5.4 Hz, 1H); 7.12 (d, J = 4.08 Hz, 1H). Elemental
analysis: Calcd for ZnC19H17N4S2F6O6: C, 35.89; H, 1.90; N, 8.81.
Found: C, 35.50; H, 2.19; N, 8.71.
[Zn(L7)2](CF3SO3)2 (8). Stoichiometric amounts of L7 (10 mg, 0.037
mmol) and Zn(CF3SO3)2 (6.7 mg, 0.019 mmol) were dissolved in
acetonitrile/dichloromethane (1:1, 1 mL). The solvent was then
partially evaporated. Slow diffusion of THF afforded 4 mg of X-ray-
1
quality prisms of [Zn(L7)2](CF3SO3)2 (0.004 mmol, yield 24%). H
4
3
4
(td, 1H, 3J = 7.6 Hz, J = 1.2 Hz); 8.45 (dd, 1H, J = 4.8 Hz, J = 1.6
Hz); 8.32 (dd, 1H, 3J = 7.6 Hz, 4J = 0.8 Hz); 8.03 (t, 1H, 3J = 8.0 Hz);
8.0 (dd, 1H, 3J = 8.0 Hz, 4J = 1.6 Hz); 7.88 (dt, 1H, 3J = 7.6 Hz, 4J = 2
Hz); 7.36 (d, 1H, 3J = 4.8 Hz); 7.20 (dd, 1H, 3J = 8.0 Hz, 4J = 4.8 Hz);
NMR (CD3CN, 400 MHz) δ 8.64 (7, 3J = 8.1 Hz, 1H,); 8.51 (d, 3J =
7.8 Hz, 1H); 8.43 (d, 3J = 8.2 Hz, 1H); 8.30−8.27 (m, 2H, H2); 8.13
3
4
3
4
(dd, J = 7.8 Hz, J = 1.4 Hz, 1H); 8.05 (dt, J = 8.0 Hz, J = 1.6 Hz,
1H); 7.76 (d, 3J = 5.0 Hz, 1H); 7.71 (d, 3J = 6.6 Hz, 1H); 7.33 (dd, 3J
6.70 (d, 1H, J = 4 Hz). 13C NMR (CDCl3, 100 MHz): δ 156.82
3
4
3
4
= 6.8 Hz, J = 5.8 Hz, 1H); 7.04 (dd, J = 7.8 Hz, J = 5.3 Hz, 1H);
7.02 (d, 3J = 4.1 Hz, 1H). Elemental analysis: Calcd for
ZnC36H24N8S2F6O6: C, 47.61; H, 2.66; N, 12.33. Found: C, 46.75;
H, 3.00; N, 11.60.
(Cquat); 154.58 (Cquat); 150.16 (Cquat); 149.21 (C12); 147.69
(Cquat); 143.16 (C7); 139.35 (C1); 136.88 (C10); 129.07 (C5);
126.44 (C3); 123.84 (C11); 123.39 (Cquat); 121.23 (C9); 117.42
(C8); 117.20 (C6); 115.63 (C2); 102.56 (C4). ESI-MS (CH2Cl2): m/
z 272.93 [M+H]+. Elemental analyses: Calcd for C17H12N4: C 74.98%,
H 4.44%, N 20.58%. Found C 74.63%, H 4.31%, N 20.30%.
Preparation of the Complexes. [HL7](CF3SO3) (3). Diethyl ether
was slowly diffused into a concentrated solution containing L7 (1
equiv) and HCF3SO3 (1 equiv) in CH3CN/CH2Cl2 (1:1) to give X-
ray quality prisms of [HL7](CF3SO3).
[Y(L7)2Cl2]I3·CH2Cl2 (9). Brownish X-ray quality crystals of [Y-
(L7)2Cl2]I3·CH2Cl2 (9) slowly deposited during the air evaporation of
a concentrated CH3CN/CH2Cl2 (1:8) solution containing
YI3(THF)3.5 (1 equiv) and L7 (2 equiv).
1
Spectroscopic Measurements. H and 13C NMR spectra were
recorded on a Bruker Avance 400 MHz spectrometer. Chemical shifts
are given in parts per million (ppm), with respect to TMS. In a typical
1H NMR tiration experiment, 500 μL of a 7.5 × 10−3 M solution of
ligand L7 in CD3CN/CDCl3 (1:1) were reacted with successive
aliquots of solutions of CF3SO3H, LiClO4, Mg(ClO4)2, Zn(CF3SO3)2,
or Y(CF3SO3)·diglyme in the same solvent mixture. After each aliquot,
the 1H NMR spectrum was recorded at 298 K and the global chemical
shifts matrix was fitted to pertinent equilibria using the HypNMR-
2008 software.16 Pneumatically assisted electrospray ionization−mass
spectroscopy (ESI-MS) spectra were recorded from 10−4 M solutions
on an Applied Biosystems API 150EX LC/MS System equipped with a
Turbo Ionspray source. Elemental analyses were performed by K. L.
Buchwalder from the Microchemical Laboratory of the University of
Geneva.
X-ray Crystallography. Summary of crystal data, intensity
measurements, and structure refinements for [HL7](CF3SO3) (3),
[H2L7](ClO4)2 (4), [Li(L7)(OH2)(ClO4)] (5), Mg(L7)(OH2)3]-
(ClO4)2 (6), [Zn(L7)(THF)(CF3SO3)2] (7), [Zn(L7)2]-
(CF3SO3)2·0.13H20 (8), and [Y(L7)2Cl2]I3·CH2Cl2 (9) were
collected in Tables S4, S15, and S22 in the Supporting Information).
All crystals were mounted on quartz fibers with protection oil. Cell
dimensions and intensities were measured at 180 or 293 K on a
Agilent Supernova diffractometer with mirror-monochromated Cu-
[Kα] radiation (λ = 1.54184 Å). Data were corrected for Lorentz and
polarization effects and for absorption. The structures were solved by
direct methods (SIR97),40 all other calculation were performed with
ShellX9741 systems and ORTEP342 programs. CCDC-926740 to
CCDC-926747 (3-9) contain the supplementary crystallographic data.
The CIF files can be obtained free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, U.K.; fax: (+44) 1223-
336-033; or deposit@ccdc.cam.ac.uk).
[H2L7](ClO4)2 (4). The dissolution of L7 (10 mg, 0.037 mmol) in
acetonitrile/dichloromethane (1:1, 1 mL), followed by the addition of
6 M aq HClO4 (16 μL, 0.093 mmol) resulted in the precipitation of
[H2L7](ClO4)2. The solid was filtered, washed with dichloromethane,
diethyl ether and dried under vacuum to afford a 13 mg of
[H2L7](ClO4)2 (0.027 mmol, yield 74%) as a white solid. Slow
diffusion of THF into a concentrated solution containing L7 (1 equiv)
and HClO4 (2 equiv) in CH3CN/CH2Cl2 (1:1) gave X-ray quality
1
prisms of [H2L7](ClO4)2 (4). H NMR (CD3CN, 400 MHz): δ 8.94
(d, 3J = 3.6 Hz, 1H); 8.88 (dd, 3J = 8.0 Hz, 4J = 1.0 Hz, 1H); 8.82 (dt,
3J = 7.8 Hz, 1H); 8.71 (d, 3J = 7.8 Hz, 1H); 8.60 (d, 3J = 6.0 Hz, 1H);
3
3
3
8.48 (t, J = 8.1 Hz, 1H); 8.35 (d, J = 7.8 Hz, 1H); 8.28 (d, J = 3.8
Hz, 1H); 8.22 (t, 3J = 7.2 Hz, 1H); 8.07 (d, 3J = 8.3 Hz, 1H, H2); 7.83
(dd, 3J = 7.9 Hz, 4J = 6.0 Hz, 1H, H6), 7.26 (d, 3J = 3.8 Hz, 1H, H4).
Elemental analysis: Calcd: C17H14N4Cl2O8 ([H2L7](ClO4)2): C,
43.15; H, 2.98; N, 11.83. Found: C, 43.00; H, 3.00; N, 11.90.
[Li(L7)(OH2)(ClO4)] (5). Heptane was slowly diffused into a
concentrated solution containing L7 (1 equiv) and LiClO4 (1 equiv)
in CH3CN/CH2Cl2 (1:1) to give X-ray quality prisms of [Li(L7)-
(OH2)(ClO4)].
[MgL7](ClO4)2·3H2O (6). Stoichiometric amounts of L7 (10 mg,
0.037 mmol) and Mg(ClO4)2 (8.3 mg, 0.037 mmol) were dissolved in
acetonitrile/dichloromethane (1:1, 1 mL). The solvent was partially
evaporated and slow diffusion of diethyl ether afforded 5 mg of X-ray
quality prisms of [MgL7](ClO4)2·3H2O (0.009 mmol, yield 25%). 1H
NMR (CD3CN, 400 MHz): δ 8.87 (d, 3J = 4.5 Hz, 1H); 8.63 (dd, 3J =
5.3 Hz, 4J = 1.4 Hz, 1H); 8.54 (d, 3J = 8.2 Hz, 1H), 8.45 (dd, 3J = 7.8
Hz, 4J = 1.5 Hz, 1H); 8.42 (t, 3J = 8.1 Hz, H1); 8.40 (dt, 3J = 8.0 Hz, 4J
= 1.5 Hz, 1H); 8.34 (dt, 3J = 7.7 Hz, 4J = 1.6 Hz, 1H); 8.22 (d, 3J = 4.1
3
4
3
Hz, 1H); 8.05 (dd, J = 7.7 Hz, J = 1.5 Hz, 1H); 7.85 (ddd, J = 7.6
Hz, 4J = 5.2 Hz, 5J = 0.9 Hz, 1H); 7.62 (dd, 3J = 7.9, 4J = 5.3 Hz, 1H);
7.09 (d, 3J = 4.1 Hz, 1H). Elemental analysis: Calcd for
MgC17H18N4Cl2O11: C, 37.15; H, 3.30; N, 10.19. Found: C, 37.28;
H, 3.32; N, 10.04.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Methods of speciation (Appendixes 1 and 2). Tables of H
[Zn(L7)](CF3SO3)2 (7). Stoichiometric amounts of L7 (10 mg, 0.037
mmol) and Zn(CF3SO3)2 (13.45 mg, 0.037 mmol) were dissolved in
NMR chemical shifts, crystal data, geometric parameters, bond
I
dx.doi.org/10.1021/ic400526j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Madic, C.; Ephritikhine, M. Eur. J. Inorg. Chem. 2002, 1439−1446.
(l) Fukuda, Y.; Nakao, A.; Hayashi, K. J. Chem. Soc., Dalton Trans.
2002, 527−533. (m) Cotton, S. A.; Franckevicius, V.; How, R. E.;
Ahrens, B.; Ooi, L. L.; Mahon, M. F.; Raithby, P. R.; Teat, S. J.
Polyhedron 2003, 22, 1489−1497. (n) Guillaumont, D. J. Phys. Chem. A
2004, 108, 6893−6900. (o) Berthet, J.-C.; Nierlich, M.; Miquel, Y.;
Madic, C.; Ephritikhine, M. Dalton Trans. 2005, 369−379.
distances and bond angles, and thermodynamic data. Figures
showing molecular structures with numbering schemes and
crystal packing, H NMR titrations, ligand speciations and
applications of the site binding model. A CIF file for
compounds [HL7](CF3SO3) (3), [H2L7](ClO4)2 (4), [Li-
(L7)(OH2)(ClO4)] (5), Mg(L7)(OH2)3](ClO4)2 (6), [Zn-
(L7)(THF)(CF3SO3)2] (7), [Zn(L7)2](CF3SO3)2·0.13H20
(8), and [Y(L7)2Cl2]I3·CH2Cl2 (9). This material is available
free of charge via the Internet at http://pubs.acs.org.
1
(p) Sen
́
ec
́
hal-David, K.; Hemeryck, A.; Tancrez, N.; Toupet, L.;
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Reibenspies, J. H.; Hancock, R. D. Inorg. Chem. 2011, 50, 2764−2770.
(s) de Bettencourt-Dias, A.; Bauer, S.; Viswanathan, S.; Maull, B. C.;
Ako, A. M. Dalton Trans. 2012, 41, 11212−11218. (t) Di Bernardo, P.;
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AUTHOR INFORMATION
Corresponding Author
■
*E-mail addresses: Claude.Piguet@unige.ch (C.P.), Thi.
Hoang@unige.ch (T.H.Y.H.).
Notes
(6) (a) Drew, M. G. B.; Hudson, M. J.; Iveson, P. B.; Madic, C.;
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(b) Boubals, N.; Drew, M. G. B.; Hill, C.; Hudson, M. J.; Iveson, P.
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from the Swiss National Science Foundation
is gratefully acknowledged.
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K
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