4′-hydrazone derivatives of 2,2′:6′,2″-terpyridine: Protonation and substituent effects

Article abstract of DOI:10.1002/ejoc.200800301

Four 4′-hydrazone derivatives of 2,2′:6′,2″- terpyridine which vary in their N- and C-substitution in the R′NN=CRPh unit have been prepared and structurally characterized. Protonation studies and solution behaviour of these compounds are described, as well as representative crystal structures of mono- and diprotonated derivatives. In the solid-state structures of each neutral compound, the tpy domain adopts the anticipated trans,trans-conformation, and intramolecular steric factors compete with π-stacking effects to control the amount to which the C-phenyl substituent twists out of the plane of the tpy unit. When R′ = H, the imine NH group engages in hydrogen bonding interactions in the solid state, except where R = Ph. In solution, variable temperature ¹H NMR spectroscopy shows that on going from R = Me to Ph (with R′ = H), the barrier to rotation about the C_py-N_imine bond increases; with R = R′ = H, the hydrogen bonding capabilities of the solvent to the imine NH influence this dynamic process. In the N-methyl derivative (R = H and R′ =Me), rotation about the C_py-N_imine bond is facile at room temperature. Protonation of the derivative with R = R′ = H results in an increase in the activation barrier to rotation, consistent with a greater π-contribution to the C_py-N_imine bond. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800301

FULL PAPER
DOI: 10.1002/ejoc.200800301
4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine: Protonation and
Substituent Effects
Jonathon E. Beves,[a] Edwin C. Constable,*[a] Catherine E. Housecroft,*[a]
Markus Neuburger,[a] Silvia Schaffner,[a] and Jennifer A. Zampese[a]
Keywords: Hydrazone / Protonation / Rotamers / 2,2Ј:6Ј,2"-Terpyridine
Four 4Ј-hydrazone derivatives of 2,2Ј:6Ј,2"-terpyridine which
vary in their N- and C-substitution in the RЈNN=CRPh unit
have been prepared and structurally characterized. Proton-
ation studies and solution behaviour of these compounds are
described, as well as representative crystal structures of
mono- and diprotonated derivatives. In the solid-state struc-
tures of each neutral compound, the tpy domain adopts the
anticipated trans,trans-conformation, and intramolecular ste-
ric factors compete with π-stacking effects to control the
amount to which the C-phenyl substituent twists out of the
cept where R = Ph. In solution, variable temperature 1H NMR
spectroscopy shows that on going from R = Me to Ph (with
RЈ = H), the barrier to rotation about the Cpy–Nimine bond
increases; with R = RЈ = H, the hydrogen bonding capabilities
of the solvent to the imine NH influence this dynamic pro-
cess. In the N-methyl derivative (R = H and RЈ = Me), rotation
about the Cpy–Nimine bond is facile at room temperature. Pro-
tonation of the derivative with R = RЈ = H results in an in-
crease in the activation barrier to rotation, consistent with a
greater π-contribution to the Cpy–Nimine bond.
plane of the tpy unit. When RЈ = H, the imine NH group en- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
gages in hydrogen bonding interactions in the solid state, ex-
Germany, 2008)
complexes.[23] As an extension of this work, we have investi-
gated the 4Ј-(3,5-dimethylpyrazol-1-yl)-2,2Ј:6Ј,2ЈЈ-terpyrid-
ine ligand and its complex formation,[24] and in the first of
a series of papers, we now report the formation of four 4Ј-
hydrazone derivatives of 2,2Ј:6Ј,2ЈЈ-terpyridine (compounds
1–4, Scheme 1) and describe structural aspects and solution
behaviour of these compounds and their conjugate acids. In
future papers, we will turn our attention to the coordination
behaviour of these and related ligands. However, it is ini-
tially important for us to understand how the free ligands
behave in solution.
Introduction
The chemistry of hydrazones and their metal complexes
has long been an area of active interest, because of their
properties appropriate for their applications in, for example,
sensors, non-linear optical and polymeric materials[1–6] and
their biological applications.[7–10] Within supramolecular
chemistry, Lehn has incorporated hydrazone units into pyr-
imidine- and pyridine-containing molecular strands that
undergo programmed self-organization into metal-free heli-
cal architectures[11–13] and metal-containing helical
wires[14,15] or grid-like arrays.[16–22] Among the latter are
[Co4L4]8+ complexes [L = 4,6-bis(benzylidenehydrazino)-2-
phenylpyrimidine or 2-phenylpyrimidine-4,6-dicarbalde-
hyde bis(phenylhydrazone)] in which the eight hydrazone
NH protons can be sequentially and reversibly removed in
pH-dependent steps resulting in significant changes in the
absorption spectra of the complexes.[18]
We have recently reported a series of [FeL2]2+ and
[RuL2]2+ complexes in which L is 4Ј-(2-pyridyl)-, 4Ј-(3-pyr-
idyl)- or 4Ј-(4-pyridyl)-2,2Ј:6Ј,2"-terpyridine, and have de-
scribed the effects of mono- and bis-N-methylation on the
absorption spectra and electrochemical properties of these
[a] Department of Chemistry, University of Basel,
Spitalstrasse 51, 4056 Basel, Switzerland
Scheme 1. Structures of ligands 1–4 and labelling used for the
NMR spectroscopic assignments. Rings A and D, and protons
HB3a and HB3b are only distinguished on the NMR timescale at
low temperature (see text). For compound 3, the second phenyl
substituent is ring E.
Fax: +41-61-267-1018
E-mail: catherine.housecroft@unibas.ch
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
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The salts [H22][MeOSO3]2, [H23][MeOSO3]2 and
[H24][MeOSO3]2 (all bright yellow solids) were made in an
analogous manner to [H21][MeOSO3]2. Although the elec-
trospray mass spectrum of these salts provided evidence
only for [H2]+ (m/z 366), [H3]+ (m/z 428) and [H4]+ (m/z
366), respectively, the NMR spectroscopic data were consis-
tent with the formation of [H22][MeOSO3]2, [H23]-
[MeOSO3]2 and [H24][MeOSO3]2. However, as with [H21]-
[MeOSO3]2, hydrolysis of the anion by water in the [D6]-
DMSO solvent led to the presence of MeOH in addition to
[MeOSO3]–.
Results and Discussion
Syntheses and Structural Studies
The synthetic route to hydrazones 1–4 (Scheme 1) was by
the well established acid-catalysed condensation of a hydra-
zine (4Ј-hydrazino-2,2Ј:6Ј,2ЈЈ-terpyridine or 4Ј-(1-methylhy-
drazino)-2,2Ј:6Ј,2ЈЈ-terpyridine[25–27]) and an aldehyde or
ketone (benzaldehyde for 1 and 4, acetophenone for 2, and
benzophenone for 3). The reaction of 4Ј-hydrazino-
2,2Ј:6Ј,2ЈЈ-terpyridine and benzaldehyde in methanol in the
presence of a few drops of concentrated H2SO4 resulted in
the formation of a bright yellow solid, elemental analysis of
which was consistent with the methyl sulfate salt of [H21]2+
(Scheme 2). This observation is reminiscent of the forma-
tion of methyl sulfate and ethyl sulfate salts of diprotonated
4Ј-(3,5-dimethylpyrazol-1-yl)-2,2Ј:6Ј,2ЈЈ-terpyridine when
4Ј-hydrazino-2,2Ј:6Ј,2ЈЈ-terpyridine reacts with pentane-2,4-
dione in MeOH or EtOH in the presence of concentrated
H2SO4.[24] The electrospray mass spectrum of [H21]-
[MeOSO3]2 was unhelpful in confirming the protonation
state of 1, showing evidence only for the [H1]+ ion (m/z
Treatment of each of aqueous solutions of
[H21][MeOSO3]2, [H22][MeOSO3]2, [H23][MeOSO3]2 and
[H24][MeOSO3]2 with excess NaBF4 led to the formation of
pale yellow [H1][BF4], [H2][BF4], [H3][BF4] and [H4][BF4],
respectively. Changes in the NMR spectroscopic data were
consistent with the conversion of each diprotonated to
monoprotonated tpy species. For example, a comparison of
the 13C NMR spectra (in [D6]DMSO) revealed that signals
for carbons CA4 and CA5 shifted to lower frequency upon
reaction of [H21][MeOSO3]2 with [BF4]–; ∆δ = 0.6 and 0.3
ppm for CA4 and CA5, respectively where ∆δ = δ([MeOSO3]–
salt – [BF4]– salt). Similarly, although the signal for CA3
is broad, a change in chemical shift to lower frequency is
observed. The addition of NH4PF6 to an aqueous solution
of [H21][MeOSO3]2 yielded, after purification, a pale yellow
solid product, analytical data for which were consistent
with [H1][PF6]. The aromatic region of the 13C NMR spec-
trum of a [D6]DMSO solution of the hexafluorophosphate
salt was essentially identical to that of the tetrafluoroborate
1
352). The room temperature H NMR spectrum in [D6]-
DMSO showed the presence of methyl protons at δ 3.38
and 3.15 ppm. The latter was assigned to MeOH[28] and
the former to the [MeOSO3]– ion. The combined relative
integrals for the methyl proton signals with respect to sig-
nals for the tpy protons were consistent with the formula-
tion [H21][MeOSO3]2. In the 13C NMR spectrum ([D6]-
DMSO), signals at δ 48.6 and 53.0 ppm were assigned to
MeOH[28] and [MeOSO3]–, respectively. We attribute the
presence of the MeOH (always present to some extent in
[D6]DMSO solutions of the sample) to hydrolysis of
[MeOSO3]– by residual water in the solvent.[24,29] When the
reaction of 4Ј-hydrazino-2,2Ј:6Ј,2ЈЈ-terpyridine and benzal-
dehyde was carried out in methanol in the presence of a few
drops of concentrated HNO3 or HCl, a bright yellow solid
was isolated in each case. [D6]DMSO solutions of these
1
salt. Detailed discussion of the H NMR spectra is given
later.
The reactions of [H21][MeOSO3]2, [H22][MeOSO3]2,
[H23][MeOSO3]2 and [H24][MeOSO3]2 with K2CO3 allowed
the neutral compounds 1, 2, 3 and 4 to be isolated. All
compounds have been fully characterized by electrospray
1
mass spectrometry, elemental analysis, H and 13C NMR
spectroscopy and single-crystal X-ray crystallography. In
the 1H NMR spectra, the loss of the resonance for the
methyl sulfate anion was consistent with the formation of
each neutral product. Colourless plates of 1 were grown by
slow evaporation of a CHCl3 solution of the compound.
Figure 1 shows the molecular structure of 1, with the tpy
unit in the anticipated trans,trans-conformation with typical
bond lengths and angles. The aromatic rings are signifi-
cantly twisted with respect to one another [angles between
the least-squares planes of rings containing N1 and N2, N2
and N3, and N2 and C17: 10.64(7), 20.87(7) and 24.26(8)°].
The substituents around the C=N bond adopt an (E)-con-
figuration. In crystalline 1, pyridine nitrogen atom N3 acts
as a hydrogen-bond acceptor and pairs of molecules of 1
associate as shown in Figure 2 (a). The evolution of the two
symmetry related N4–H1···N3i interactions leads to the for-
mation of weaker CHimine···Npyridine interactions as well as
a repulsive H91···H91i contact (2.38 Å). The V-shaped di-
meric motifs assemble as shown in Figure 2 (b), forming in-
terlocking zigzig chains which run parallel to the crystallo-
graphic c-axis.
1
products exhibited the same H NMR spectroscopic signa-
tures for the tpy unit as in [H21][MeOSO3]2, suggesting the
formation of [H21][NO3]2 and [H21]Cl2. In each salt, the
signal for protons HA3 and HB3 are either very broad or
are not observed at 295 K. We return to a more detailed
discussion of the NMR spectra later.
Scheme 2. Formation of [H21]2+ as the methyl sulfate salt.
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4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine
the methyl substituents presumably prevent the evolution of
efficient NHimine···Npyridine interactions, with the result that
hydrogen bonding interactions are less favourable than in
1.
Figure 1. The molecular structure of 1 with thermal ellipsoids plot-
ted at the 50% probability level. Selected bond lengths and angles:
N4–C8 1.379(2), N4–N5 1.371(2), N5–C16 1.282(2), C16–C17
1.457(2) Å, N5–N4–C8 119.4(1), N4–N5–C16 116.6(1), N5–C16–
C17 121.2(2)°.
Figure 3. The molecular structure of 2 with thermal ellipsoids plot-
ted at the 50% probability level. Selected bond lengths and angles:
N4–C8 1.378(2), N4–N5 1.364(2), N5–C16 1.293(2), C16–C17
1.502(2), C16–C18 1.483(2) Å, N5–N4–C8 120.2(1), N4–N5–C16
118.2(1), N5–C16–C17 124.3(1), N5–C16–C18 115.9(1)°.
Figure 2. (a) Hydrogen bond association between pairs of mole-
cules of 1 in the solid state. Parameters: N4H1···N3i 2.19 Å,
N4···N3i 3.091(2), N4–H1···N3i 156°. C16H161···N3 2.62 Å,
C16···N3 3.482(2) Å, C16–H161···N3 144°. Symmetry code i = 2 –
x, y, 1/2 – z. (b) Assembly of hydrogen-bonded dimers of 1 in the
solid state.
X-ray-quality colourless plates of 2 (Figure 3) were
grown by slow evaporation of a CH2Cl2 solution of the
compound. Bond lengths and angles are unexceptional, the
tpy unit has the usual trans,trans-conformation, and the hy-
drazone adopts an (E)-configuration. The angles between
the least-squares planes of the rings containing N1 and N2,
Figure 4. Packing diagram for 2 showing interlocking π-stacked
pairs of molecules. One pair is shown in stick representation, and
illustrates the close CtpyH···CH3 contacts.
Crystals of 3.CH2Cl2 suitable for X-ray diffraction were
N2 and N3, and N2 and C17 are 6.06(7), 6.44(7) and grown by by slow evaporation of a CH2Cl2 solution of the
67.5(8)°, and therefore a molecule of 2 is much closer to compound. Figure 5 illustrates that the tpy domain is close
being planar than is 1. This is, presumably, a consequence to being planar [angles between the least-squares planes of
of the packing which is dominated by π-stacking (Figure 4). rings containing N1 and N2, and N2 and N3: 2.51(8) and
Pairs of molecules stack in slightly offset columns with a 6.74(8) Å] and adopts the expected trans,trans-conforma-
distance of 3.20 Å between the least-squares planes of the tion. The phenyl substituents are twisted away from the
molecules. The columns interlock as shown in Figure 4. The plane of the hydrazone unit [angles between the least-
packing efficiency of the crystalline lattice is 70.5%,[30] and squares planes of rings containing N2 and C17, and N2
the stabilizing energy gained from the extensive π-stacking and C23: 19.15(8) and 75.01(8)°], thus minimizing steric in-
must compensate for the repulsive energy of the close teractions. It is worth noting that the imine hydrogen atom
C
tpyH···CH3 contacts within each pair of molecules H4 is in close contact with the ipso-carbon atom C23
(H91···H173i = 2.37 Å, symmetry code i = 1 – x, 2 – y, 1 – (H4···C23 2.42 Å) and the adjacent C28 (H4···C28 2.67 Å),
z). The mode by which efficient packing is achieved by 2 a situation discussed previously by Drew et al.[31] The mole-
contrasts with that in 1 (packing efficiency of 69.9%[30]) in cules pack so that pairs of tpy units are π-stacked, with the
which NHimine···Npyridine and CHimine···Npyridine interactions planes of pyridine rings containing N2 and N3 being 3.58 Å
are important (Figure 2). In 2, the steric requirements of apart. The solvent CH2Cl2 molcules reside in cavities, hy-
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E. C. Constable, C. E. Housecroft et al.
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drogen bonded to pyridine N atoms [C29H292···N3 2.45 Å, character in the C8–N4 bond [1.389(2) Å compared to
C29···N3 3.273(3) Å, C29–H292···N3 143°. C29H291···N2i 1.378(2) or 1.379(2) Å in 1–3]. Other simple N-methyl hy-
2.55 Å, C29···N2i 3.417(3) Å, C29–H292···N2i 153°; sym- drazones also show this preference.[32–35] Pairs of molecules
metry code i = 1 – x,1 – y, 1 – z] and with additional weak (related by a crystallographic inversion centre) assemble so
contacts to phenyl rings (Cl1···H21ii 2.94 Å, symmetry code that the pyridine rings containing N2 are π-stacked (dis-
ii = –1 + x, –1 + y, z; Cl1···centroid ring containing C23 tance between planes of rings: 3.36 Å). Atom N2 makes a
3.79 Å). Presumably, the proximity of a phenyl substituent weak contact to a phenyl CH group in an adjacent pair of
1
to the imine NH group prevents the latter engaging in hy- molecules (N2···H231iC23i 2.70 Å, symmetry code i = /2 +
3
1
drogen bonded interactions. The closest approach of one x, /2 –y, /2 + z).
CH2Cl2 chlorine atom is 3.26 Å (N4H4···Cl1).
Figure 6. The molecular structure of 4 with thermal ellipsoids plot-
ted at the 50% probability level. Selected bond lengths and angles:
N4–C8 1.389(2), N4–N5 1.363(2), N5–C17 1.284(2), N4–C16
1.450(2), C17–C18 1.466(3) Å; N5–N4–C8 115.8(1), N4–N5–C17
119.1(2), N5–C17–C18 120.2(2)°.
Figure 5. The molecular structure of 3 in 3.CH2Cl2 with thermal
ellipsoids plotted at the 50% probability level. Selected bond
lengths and angles: N4–C8 1.378(2), N4–N5 1.361(2), N5–C16
1.288(2), C16–C17 1.479(2), C16–C23 1.495(2) Å; N5–N4–C8
118.5(1), N4–N5–C16 118.6(1), N5–C16–C17 116.2(1), N5–C16–
C23 123.9(1)°.
The mono- and diprotonated states of the 4Ј-hydrazone
derivatives of 2,2Ј:6Ј,2ЈЈ-terpyridine were confirmed by rep-
resentative structural studies. X-ray-quality crystals of
[H21]Cl2·DMSO were grown from a DMSO solution of the
compound. Figure 7 shows the [H21]2+ cation, hydrogen
bonded to the two chloride ions in the asymmetric unit. The
In each of compounds 1 to 3, the hydrazone unit con- tpy domain adopts a cis,cis-configuration. In an [H2tpy]2+
tains an NH unit which has the potential to engage in hy- ion, it is usual for the two outer pyridine rings to carry one
drogen bonded interactions, although in 3 this appears to proton each and for the latter to be involved in hydrogen-
be unfavourable on steric grounds (see above). The devia- bonded interactions with the central pyridine N-atom as
tion of the HNN=C framework from the plane of the cen- well as with an acceptor atom.[36–42] As Figure 7 illustrates,
tral pyridine ring of the tpy domain in each compound is the [H21]2+ ion in [H21]Cl2·DMSO falls into this structural
small. Each compound exhibits the same Cpy–Nimine bond pattern, with one chloride ion acting as a hydrogen-bond
length (see Figure captions) and this is shorter than the sum acceptor with respect to the [H21]2+ ion. The imine NH also
of the covalent radii (1.52 Å) indicating that the bond con- acts as a hydrogen-bond donor, interacting with the second
tains some π-character.
chloride ion (see Figure caption). The hydrogen-bonded
X-ray-quality crystals of 4 were grown by by slow evapo- motif locks the tpy unit into a near planar conformation
ration of a CH2Cl2/EtOH solution of the compound, al- [angles between the least-squares planes of the rings con-
lowing us to investigate the structural consequences of in- taining N1 and N2, and N2 and N3 are 9.90(7) and
troducing an N-methyl substituent. The structure of 4 is 7.72(7)°, respectively]. The phenyl substituent also lies close
shown in Figure 6; bond parameters are as expected and to this plane [angle between the least-squares planes of
the substituents about the C=N bond adopt an (E)-configu- rings containing N1 and C17: 8.95(8)°]. The latter is a con-
ration. The tpy domain has the anticipated trans,trans-con- sequence of the molecular packing; [H21]2+ cations as-
formation, and deviates slightly from planarity [angles be- semble into π-stacked columns with alternating distances
tween the least-squares planes containing N1 and N2, and of 3.19 and 3.49 Å between the least-squares planes drawn
N2 and N3: 9.45(9) and 9.00(9)°, respectively]. The phenyl through adjacent cations. The packing is completed by ex-
substituent is twisted out of the plane of the central pyr- tensive hydrogen bonding interactions involving the chlo-
idine ring by 20.42(9)°. The deviation of the N5N4C16 unit ride ions and DMSO solvent molecules.
from the least-squares plane of the ring containing N2 is
Yellow plates of [H22][NO3][MeOSO3]·H2O were grown
only 11.4(2)°, compared to a corresponding angle of 7.4(2)° by adding a drop of dilute aqueous HNO3 to an aqueous
for compound 1. This results in repulsive HMe···Hpy con- solution of [H22][MeOSO3]2 and allowing the solvent to
tacts, but this is presumably offset by retention of some π- evaporate slowly. A single-crystal X-ray diffraction study
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4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine
Figure 7. The molecular structure of [H21]Cl2 in the asymmetric
unit of [H21]Cl2·DMSO with thermal ellipsoids plotted at the 50%
probability level. Selected bond lengths and angles: N4–C8
1.362(2), N4–N5 1.367(2), N5–C16 1.290(2), C16–C17 1.465(2) Å;
N5–N4–C8 119.7(1), N4–N5–C16 115.0(1)°. Hydrogen bond pa-
rameters: N1H1···Cl1 2.26 Å, N1···Cl1 3.018(1) Å, N1–H1···Cl1
151°; N3H3···Cl1 2.25 Å, N3···Cl1 3.049(1) Å, N3–H3···Cl1 154°;
N1H1···N2 2.26 Å, N1···N 2.619(2) Å, N1–H1···N2 106°;
N3H3···N2 2.30 Å, N3···N2 2.638(2) Å, N3–H3···N2 104°;
N4H4···Cl2 2.29 Å, N3···N2 3.158(2), N3–H3···N2 173°.
Figure 8. The molecular structure of the [H22]2+–[NO3]– hydrogen-
bonded ion pair in [H22][NO3][MeOSO3]·H2O; thermal ellipsoids
are plotted at the 50% probability level. Selected bond lengths and
angles: C8–N4 1.377(4), N4–N5 1.363(3), C16–N5 1.299(4), C16–
C17 1.494(4), C16–C18 1.492(4) Å, C8–N4–N5 118.9(2), N4–N5–
C16 118.6(2), C18–C16–N5 115.2(3), C17–C16–N5 123.9(3), C17–
C16–C18 120.9(3)°. See text for the hydrogen bond parameters.
confirmed that 2 is diprotonated (Figure 8). The three pyr-
idine rings adopt a cis,cis-configuration, with the nitrate ion
acting as a hydrogen-bond acceptor [N1H1···O5 1.92 Å,
N1···O5 2.722(3) Å, N1–H1···O5 161°; N3H3···O5 1.95 Å,
N3···O5 2.762(3) Å, N3–H3···O5 161°]. As in [H21]2+, this
hydrogen bonding compels the tpy unit in [H22]2+ to be
planar [angles between the least-squares planes of the rings
containing N1 and N2, and N2 and N3: 2.7(1) and 4.6(1)°,
respectively]. The diprotonated state of the tpy derivative is
further stabilized by hydrogen-bonded interactions to N2
[N3H3···N2 2.29 Å, N3···N2 2.660(3) Å, N3–H3···N2 107°;
N1H1···N2 2.29 Å, N1···N2 2.670(3) Å, N1–H1···N2 107°].
The imine NH group is hydrogen-bonded to atom O4 of
the [MeOSO3]– anion [N4H4···O2 2.04 Å, N4···O2
2.859(4) Å, N4–H4···O2 161°]. The hydrogen-bonded inter-
actions are further extended to the solvate water molecule
and then, via a crystallographic inversion centre, to a repeat
unit (Figure 9). The phenyl ring is essentially coplanar with
the tpy unit [angle between the least-squares planes of the
Figure 9. Part of the hydrogen-bonded network in [H22][NO3]-
[MeOSO3]·H2O; symmetry code i = 1 – x, 1 – y, 2 – z. N and O
atoms are shown in black. Parameters for hydrogen bonded interac-
tions is given in Table S1 (see Supporting Information).
C6 ring and ring containing N2: 6.2(2)°]. The [H22]2+ cat- respectively]. It adopts a cis,cis-conformation, with both of
ions are stacked in the crystal lattice to generate a herring- atoms N1 and N3 participating in hydrogen-bonded inter-
bone architecture (Figure S1) consisting of alternating lay- actions with the N2H2 unit [see discussion of (H1)+ and
ers with separations (calculated for least square planes (H2)+]. The deviations of atoms N4, N5 and C16 from the
through each molecule) of 3.22 and 3.48 Å. The shorter of least-squares plane of the central pyridine ring are 0.08,
these separations arises from π-stacking between pyridine 0.11 and 0.41 Å, respectively. Neither phenyl substituent is
rings containing atoms N2 and N3, whereas coplanar with the central pyridine ring [angles between the
Cmethyl···pycentroid interactions (C17···centroid of ring con- least-squares planes of the rings containing C17 and N2,
taining N1: 3.55 Å) give rise to the larger layer spacing.
and C23 and N2: 23.6(1) and 64.2(1)°, respectively]. In the
Attempts to grow crystals of yellow [H23][MeOSO3]2 by crystal lattice, cations are arranged in head-to-tail pairs
slow evaporation of an aqueous solution of the salt instead with π-stacking of the central rings of the tpy units (dis-
gave rise to X-ray-quality colourless plates of tance between rings containing atoms N2: 3.40 Å). This re-
[H3][MeOSO3]. The structure of the [H3]+ cation is shown sults in unfavourable H11···H251a contacts (2.2 Å, sym-
in Figure 10. The tpy domain is close to being planar metry code a = –x, 1 – y, 1 – z). The cation pairs assemble
[angles between the least-squares planes of rings containing into columns, with adjacent pairs being slightly offset from
atoms N1 and N2, and N2 and N3: 2.8(1) and 11.42(9)°, one another. Anions and cations are associated through hy-
Eur. J. Org. Chem. 2008, 3569–3581
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E. C. Constable, C. E. Housecroft et al.
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drogen bonding, with the imine NH acting as the hydrogen- involved in stabilizing hydrogen-bonded interactions with
bond donor [N4H4···O3 1.89 Å, N4···O3 2.789(2) Å, N4– the NH unit, while the counterions or solvate are preferen-
H4···O3 151°].
tially involved in hydrogen bonding with the hydrazone
NH. The two outer pyridine rings in each of the [H2]+ and
[H1]+ cations are twisted out of the plane of the central ring
with angles between the least-squares planes of the rings
containing N1 and N2, and N2 and N3 of 10.8(1) and
6.5(1)° in [H2][BF4], and 7.2(2) and 16.3(2)° in [H1][PF6]·
H2O. The phenyl ring in [H2][BF4] is not coplanar with the
central pyridine ring [angle between the least-squares pla-
nes: 18.4(9)°]. This results in a reduction in the conjugation
along the C8N4N5C16C18 chain, which manifests itself in
a longer Cphenyl–Cazomethine bond [1.483(3) Å] compared to
that in [H1][PF6]·H2O [1.457(6) Å] in which the phenyl and
central pyridine rings are coplanar [angle between least-
squares planes: 0.7(2)°]. The difference between the molecu-
lar structures of the cations appears to be associated with
the crystal packing. In [H1][PF6]·H2O, cations are stacked
with alternating separations of 3.29 and 3.32 Å. This
pattern arises from the interactions of each phenyl ring with
an imino nitrogen atom (N5) on one side and a π-stacked
pyridine ring (containing N2) on the other. The overall
packing can be described in terms of stacks of cations, be-
tween which run columns of water molecules and [PF6]–
anions (Figure S2, Supporting Information). In contrast,
the packing motif in [H2][BF4] consists of pairs of [H2]+
Figure 10. The molecular structure of the [H3]+ cation in
[H3][MeOSO3]; thermal ellipsoids are plotted at the 50% prob-
ability level. Selected bond lengths and angles: N4–N5 1.376(2),
N4–C8 1.348(2), N5–C16 1.292(2), N2–H2 0.98, N1···H2 2.20,
N3···H2 2.25, N1···N2 2.630(2), N2···N3 2.650(2) Å; N5–N4–C8
118.8(2), N4–N5–C16 117.1(2)°.
The change in protonation state that accompanies dissol- cations related by a C2 axis (Figure S3). There is π-stacking
ution of [H21][MeOSO3]2 or [H22][MeOSO3]2 in hot MeOH between pairs of pyridine rings containing N3 (distance be-
followed by anion exchange, was confirmed by single crystal tween planes: 3.35 Å) and N2 (distance between planes:
structure determinations of [H2][BF4] [colourless plates 3.31 Å). The cavity formed by the hydrazone NH and
grown by slow evaporation of an aqueous acetone (1:5) methyl group accommodates a [BF4]– ion with associated
solution of the salt] and of [H1][PF6]·H2O [colourless plates hydrogen-bonded interactions [N4···F2i 2.798(4) Å, N4–
obtained by slow evaporation of a MeCN/H2O (5:1) solu- H4···F2i 148°; C4···F1 3.337(3) Å, C4–H41···F1i 172°;
tion of the compound]. Figure 11 and Figure 12 show the C7···F1i 3.359(3) Å, C7–H71···F1i 171°; C17···F2i
molecular structures of the [H2]+ and [H1]+ ions present in
[H2][BF4] and [H1][PF6]·H2O, respectively. In both salts
and in [H3][MeOSO3], the tpy unit adopts a cis,cis-confor-
mation. This is in contrast to the cis,trans-conformation ob-
served in [Htpy][CF3SO3][43] and [Htpy][ReO4].[44] In these
salts, a [CF3SO3]– or [ReO4]– anion resides close to the site
of protonation in the cation and participates in a hydrogen-
bonded interaction which is in addition to the N–H···N in-
teraction responsible for the cis-arrangement of two of the
pyridine rings. A pertinent difference between [Htpy]+ and
the family of monoprotonated tpy ligands in this study is
the presence of the hydrazone NH group which may also
become involved in hydrogen bonding. In [H3][MeOSO3],
the hydrazone NH group in the [H3]+ cation is hydrogen
bonded to the methyl sulfate anion [N4–H4 0.98,
N4H4···O3 1.89, N4···O3 2.789(2), N4–H4···O3 151°]. Simi-
larly, in [H2][BF4], the hydrazone NH group participates in
hydrogen bonding to the [BF4]– counterion (see later). In
Figure 11. The molecular structure of the [H2]+ cation in [H2][BF4]
with thermal ellipsoids plotted at the 50% probability level. Se-
lected bond lengths and angles: N4–C8 1.355(2), N4–N5 1.372(2),
N5–C16 1.289(2), C16–C17 1.500(3), C16–C18 1.483(3), N2–H2
0.92, N1···H2 2.18, N3···H2 2.23, N1···N2 2.615(3), N2···N3
2.616(3) Å, N5–N4–C8 117.3(2), N4–N5–C16 118.8(2), N5–C16–
[H1][PF6]·H2O, the hydrazone NH is hydrogen bonded to
the solvate water molecule [N4H2···O1 1.93 Å, N4···O1
2.806(5) Å, N4–H2···O1 178°], and the latter forms weak
hydrogen bonds to the [PF6]– anion. We propose that the
[H1]+, [H2]+ and [H3]+ cations adopt cis,cis-conformations
in order that both of the outer pyridine N-atoms may be C17 124.9(2), N5–C16–C18 114.2(2), C17–C16–C18 120.9(2)°.
3574 Eur. J. Org. Chem. 2008, 3569–3581
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4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine
3.427(4) Å, C17–H173···F2i 163°; symmetry code i = x, 1 – same (1.38 Å). Hence, differences in the barrier to rotation
1
y, /2 + z]. The packing is then further extended through about the Cpy–Nimine bond are likely to be steric rather than
aromatic CH···F interactions and stacking of dimeric mo- electronic in origin. Consistent with this, we observe that
tifs.
on going from 2 to 3 in [D6]DMSO, the increased steric
demands of the C-phenyl vs. C-methyl substituent increases
the barrier to rotation. At room temperature, the observa-
tion that H3B appears as a broad signal for 1, but a sharp
singlet for 2, indicates that introducing the C-methyl sub-
stituent lowers the barrier to rotation about the Cpy–Nimine
bond. Based on steric arguments, this was a unexpected ob-
servation. However, changing the solvent to [D6]acetone re-
sults in the expected trend: the H3B signal full-width-at-
half-height 4.8, 5.3 and 9.0 Hz for 1, 2 and 3 respectively.
The solvent dependence of the dynamic behaviour of 1 can
be rationalized in terms of the ability of the NH proton to
engage in hydrogen bonding with
a
suitable ac-
ceptor.[31,47,48] DMSO is expected to be a better hydrogen-
bond acceptor than acetone,[49] and association between 1
and the solvent will result in steric hindrance that will slow
down the rate of rotation about Cpy–Nimine bond. The hy-
drogen bonding capacity of the imine NH in 1 is apparent
in its packing in the solid state (Figure 8), and this observa-
tion is in line with the results of several studies of phenylhy-
drazones which conclude that such hydrogen bonding is the
predominant factor is determining solid state conformation
and solution dynamic behaviour.[31,50] Consistent with the
proposal that hydrogen bonding between the imine NH and
solvent molecules hinders rotation about the Cpy–Nimine
Figure 12. The molecular structure of the [H1]+ cation in [H1][PF6]·
H2O with thermal ellipsoids plotted at the 40% probability level.
Selected bond lengths and angles: C8–N4 1.346(5), N4–N5
1.377(5), C16–N5 1.284(5), C16–C17 1.457(6), N2–H1 0.89,
N1···H1 2.24, N3···H1 2.25, N1···N2 2.636(5), N2···N3 2.653(5) Å,
C8–N4–N5 119.8(3), N4–N5–C16 115.5(3), C17–C16–N5
121.2(4)°.
Solution Behaviour
In solution, each of compounds 1 to 4 exists as a single bond is the observation that the rotation is facile in com-
1
isomer, shown by NOESY experiments to be the (E)-isomer pound 4 (i.e. the N-methyl derivative). The H NMR spec-
as observed in the solid state. This is the expected isomer tra of 1, 2 and 3 at 195 K (Figure 14) are consistent with
for aryl hydrazones.[45] The 1H NMR spectra of compounds static structures in which the 4Ј-substituent lies in, or close
1 to 4 and of their protonated analogs are instructive in to, the plane of the tpy unit. Protons H3a and H3b
terms of the following two fluxional processes: (i) rotation (Scheme 1) were assigned from the NOESY cross peak be-
about the Cpy–Nimine bond, and (ii) rotation about the Cpy– tween H3a and HNH. Coupling between HB3a and HB3b is
1
Cpy bonds. We first consider the H NMR spectra of the resolved for 1 with J = 2.1 Hz. Although each of the re-
neutral compounds, shown in Figure 13. In [D6]DMSO, the maining tpy proton signals also splits at 195 K, overlap of
room temperature spectra show well separated resonances signals precludes unambiguous assignments to rings A and D.
for the tpy protons; changing the solvent to [D6]acetone
We consider the effects of protonation on dynamic be-
(see below) results in overlap of the HA3 and HA6 signals. haviour with a detailed study of the series 1, [H1]+ and
In each spectrum in Figure 13, the resonances assigned to [H21]2+. There is a significant change in the chemical shift
the tpy protons reveal that pyridine rings A and D for the signal assigned to the NH proton and signals in the
(Scheme 1) are equivalent in the NMR timescale, suggesting aromatic region when 1 is protonated. This is exemplified
1
that there is rotation of the 4Ј-substituent about the Cpy– by comparing the H NMR spectra of 1 (Figure 13) and
Nimine bond. With the exception of proton HA6 in com- [H21][MeOSO3]2 (Figure 15). The figures also illustrate that
pound 3, the only signal the line shape of which changes in the room temperature spectrum of 1, the signal for HB3
along the series is that assigned to H3B, i.e. the proton clos- is broad while that for HA3 is a well-resolved doublet. In
est to the 4Ј-substituent. For compound 4, the signal is contrast, both signals are extremely broad in the spectrum
sharp at 295 K, consistent with fast rotation about the Cpy– of [H21][MeOSO3]2. Upon warming to 360 K, the reso-
Nimine bond. Analogous dynamic behaviour is observed for nances assigned to HA3 and HB3 sharpen (Figure 16), con-
the NHMe substituent in N-methylaniline.[46] On cooling firming their assignments. Low temperature 1H NMR spec-
an [D6]acetone solution of 4, the signal for H3B splits, but tra of [H21][MeOSO3]2 could not be acquired because the
only broad signals at δ 9.05 and 8.19 ppm are resolved at compound was very poorly soluble in common low freezing
195 K (Figure 14). The latter have been assigned to H3b and point solvents. However, salts of [H1]+ were more amenable
H3a, respectively (see Scheme 1) by analogy with com- to low temperature studies. Cooling an [D6]acetone solution
pounds 1–3 (see below). For 1, 2 and 3, it is important to of [H1][PF6] to 255 K results in a splitting of the signals for
note that the solid-state structural data for these com- HA3 and HB3 to give pairs of equal intensity signals (HA3 δ
pounds reveal that the Cpy–Nimine bond lengths are the 8.82 and 8.43 ppm, and HB3 δ 8.62 and 7.90 ppm). Coup-
Eur. J. Org. Chem. 2008, 3569–3581
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3575

E. C. Constable, C. E. Housecroft et al.
FULL PAPER
Figure 13. Aromatic and NH regions of the 500 MHz 1H NMR spectra of neutral compounds 1 to 4 in [D6]DMSO at 295 K. See
Scheme 1 for atom labelling.
Figure 14. Aromatic and NH regions of the 500 MHz 1H NMR spectra of neutral compounds 1 to 4 in [D6]acetone at 195 K. See
Scheme 1 for atom labelling.
ling between HB3a and HB3b is observed with J = 1.8 Hz. signal is sharp (δ 12.3 ppm at 195 K and δ 11.6 ppm at
Pairs of signals for all the pyridine ring protons are resolved 315 K in [D6]acetone) over the whole 360–195 K tempera-
by 220 K. The assignments shown in the lowest trace in ture range, the pyridinium proton is not observed above
Figure 16 were made using NOESY and COSY experi- 255 K. On cooling, a broad signal at δ 13.4 ppm becomes
ments, starting with NOESY cross peaks between the visible at 255 K and is sharp at 195 K.
NHimine and HB3a, and HB3a and HA3 protons (see
Both [H2tpy]2+ and [Htpy]+ are weak acids (pKa = 3.57
Scheme 1 for labelling). The variable temperature NMR and 4.54, respectively, 298 K, in 0.2  aqueous KCl).[51] The
spectroscopic data are consistent with rotation about the fact that treatment of [H21][MeOSO3]2 or [H22][MeOSO3]2
Cpy–Nimine bond being rapid on the NMR timescale at in hot MeOH with NaBF4 or NH4PF6 results in the forma-
360 K, and frozen out at low temperatures with [H1]+ tion of tetrafluoroborate or hexafluorophosphate salts of
adopting the static structure shown in Figure 5. The spec- [H1]+ or [H2]+ indicates that, in the absence of a strong
troscopic data illustrated in the figures indicate that the ac- hydrogen-bond acceptor (viz. [MeOSO3]–), [H21]2+ and
tivation barrier to rotation increases upon protonation of [H22]2+ will partially deprotonate in solution. We argued
1, and this is consistent with a greater contribution from the that it should be possible to prepare [H21][PF6]2 by treat-
resonance form for [H1]+ shown on the right of Scheme 3. ment of 1 with an excess of HPF6 under conditions where
Changes in the signal for HA3 give information concerning 1 and [H1]+ were the most potent proton acceptors avail-
rotation about the Cpy–Cpy bonds. Again, protonation able. The addition of HPF6 (60% aqueous) to a solution of
raises the energy barrier to rotation, consistent with the 1 in EtOH resulted in the immediate precipitation of a
pyridine N atoms being involved in hydrogen bonding inter- bright yellow solid. Elemental analysis was consistent with
actions with the proton. Finally, although the imine NH the formation of [H21][PF6]2. However, there is evidence
3576
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Eur. J. Org. Chem. 2008, 3569–3581

4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine
Conclusions
We have synthesized and fully characterized four 4Ј-hy-
drazone derivatives 1–4 of 2,2Ј:6Ј,2ЈЈ-terpyridine which vary
in their N- and C-substitution. In the solid-state structures
of compounds 1–4, the tpy domain adopts the anticipated
trans,trans-conformation, and intramolecular steric factors
compete with π-stacking effects to control the amount to
which the C-phenyl substituent twists out of the plane of
the tpy unit. In each of compounds 1 to 2, the imine NH
engages in hydrogen bonded interactions, but in 3 this ap-
pears to be unfavourable on steric grounds. In solution,
variable temperature 1 H NMR spectroscopy shows that the
increased steric demands of the C-phenyl in 3 vs. C-methyl
substituent in 2 increases the barrier to rotation about the
Cpy–Nimine bond, while in 1, the hydrogen bonding capabili-
ties of the solvent to the imine NH influence this dynamic
process. In 4, rotation about the Cpy–Nimine bond is facile
at room temperature. Protonation of 1 results in an increase
in the activation barrier to rotation, consistent with a
greater π-contribution to the Cpy–Nimine bond.
Figure 15. Aromatic and NH regions of the 500 MHz 1H NMR
spectra of [H21][MeOSO3]2 in [D6]DMSO at 295 K. See Scheme 1
for atom labelling.
Experimental Section
General: 1H and 13C NMR spectra were recorded on a Bruker Av-
ance DRX 500 spectrometer; the numbering scheme for the ligands
is shown in Scheme 1. Chemical shifts for 1H and 13C NMR spectra
are referenced to residual solvent peaks with respect to TMS = δ 0
ppm. Electrospray mass spectra were recorded using a Finnigan
MAT LCQ mass spectrometer. Melting points were recorded on
a Stuart Scientific melting point apparatus SMP3. 4Ј-Hydrazino-
2,2Ј:6Ј,2ЈЈ-terpyridine was prepared as previously reported, and
spectroscopic data were consistent with those in the literature.[25–27]
In the 1H NMR spectra listed below, data at 360 K are given when-
ever the spectrum at 295 K contains very broad or unresolved sig-
nals.
4Ј-(1-Methylhydrazino)-2,2Ј:6Ј,2ЈЈ-terpyridine: This was prepared as
described previously, m.p. 212–214 °C (ref.[25] 217–219 °C). 1H
NMR spectroscopic data were consistent with literature data.[25]
13C{1H} (125 MHz, [D6]DMSO, 295 K): δ = 158.2 (CB4), 156.2
(CA2/B2), 154.7 (CA2/B2), 149.0 (CA6), 137.1 (CA4), 123.9 (CA5),
120.7 (CA3), 103.5 (CB3), 41.7 (CMe) ppm.
Figure 16. Aromatic region of the 500 MHz 1H NMR spectra of
(a) [H21][MeOSO3]2 in [D6]DMSO at 295, 315 and 360 K, and (b)
[H1][PF6] in [D6]acetone at 220 K. See Scheme 1 for atom labelling.
[H21][MeOSO3]2: 4Ј-Hydrazino-2,2Ј:6Ј,2ЈЈ-terpyridine (0.20 g,
0.76 mmol) was dissolved in hot methanol (15 cm3), and excess
benzaldehyde (0.10 g, 0.94 mmol) was added giving a colourless
solution. A few drops of concentrated H2SO4 were added, and a
yellow precipitate formed almost immediately. The suspension was
heated at reflux for 3 h and then cooled to room temperature. The
bright yellow solid product was collected by filtration and washed
with EtOH. [H21][MeOSO3]2 was isolated as a yellow powder
(0.42 g, 0.73 mmol, 96%). 1H NMR (500 MHz, [D6]DMSO,
360 K): δ = 12.02 (br., HNH), 8.89 (ddd, J = 4.8, 1.7, 0.9 Hz, 2 H,
HA6), 8.53 (d, J = 8.0 Hz, 2 H, HA3), 8.34 (s, 1 H, HHC=N), 8.19
(td, J = 7.7, 1.7 Hz, 2 H, HA4), 8.11 (s, 2 H, HB3), 7.91 (dd, J =
7.9, 1.5 Hz, 2 H, HC2), 7.72 (ddd, J = 7.6, 4.8, 1.0 Hz, 2 H, HA5),
7.5 (m, 3 H, HC3+C4), 3.39 (s, HOMe, see text) ppm. 1H NMR
(500 MHz, [D6]DMSO, 295 K): δ = 12.45 (s, NH), 8.93 (d, J =
4.4 Hz, 2 H, HA6), 8.7 (v br., HA3), 8.5 (v br., HB3), 8.30 (s, 1 H,
HHC=N), 8.25 (t, J = 7.6 Hz, 2 H, HA4), 7.96 (dd, J = 7.5, 2.0 Hz,
2 H, HC2), 7.79 (dd, J = 6.8, 5.3 Hz, 2 H, HA5), 7.50 (m, 3 H,
Scheme 3. Resonance structures for [H1]+.
that in [D6]acetone solution, an equilibirium mixture of
1
[H21][PF6]2 and [H1][PF6] exists; the H NMR spectrum at
195 K exhibits two sets of signals (one well resolved and
the other broadened).
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3577

E. C. Constable, C. E. Housecroft et al.
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HC3+C4), 3.38 (s, HOMe, see text) ppm. 13C{1H} NMR (125 MHz,
ppm. 1H NMR (500 MHz, [D6]DMSO, 295 K): δ = 11.97 (s, HNH),
[D6]DMSO, 295 K): δ = 156.0 (CB4), 149.2 (CA6), 147.8 (CC=N), 8.68 (d, J = 4.0 Hz, 2 H, HA6), 8.62 (br., HA3), 8.25 (s, 1 H,
146.8 (CA2+B2), 139.8 (CA4), 133.7 (CC1), 130.7 (CC4), 129.0 (CC3),
HHC=N), 8.16 (t, J = 7.4 Hz, 2 H, HA4), 8.1 (v br., HB3), 7.92 (d, J
= 7.1 Hz, 2 H, HC2), 7.69 (t, J = 5.2 Hz, 2 H, HA5), 7.50 (m, 3 H,
HC3+4) ppm. 13C{1H} NMR (125 MHz, [D6]DMSO, 295 K): δ =
155.4 (CB4), 149.4 (CA6), 148.5 (CA2+B2), 146.6 (CC=N), 139.1 (CA4),
133.9 (CC1), 130.4 (CC4), 128.9 (CC3), 127.5 (CC2), 126.6 (CA5),
122.4 (br., CA3), 104.2 (br., CB3) ppm. ES-MS: m/z = 352 [H1]+.
C22H18F6F6N5P·0.75H2O (624.88): calcd. C 51.72, H 3.85, N 13.71;
found C 51.71, H 3.86, N 13.63.
127.8 (CC2), 127.1 (CA5), 122.8 (br., CA3), 105 (br., HB3), 53.0 (CMe
)
ppm. ES-MS: m/z = 352 [H1]+. C24H27N5O9S2 (593.63): calcd. C
48.56, H 4.58, N 11.80; found C 48.77, H 4.21, N 11.97.
[H21][NO3]2: The method and scale were as for [H21][MeOSO3]2,
replacing concentrated H2SO4 by HNO3 (Caution!). [H21][NO3]2
was isolated as a bright yellow powder (0.24 g, 0.50 mmol, 70%).
1H NMR (500 MHz, [D6]DMSO, 295 K): δ = 12.28 (br., NH), 8.93
(d, J = 4.7 Hz, 2 H, HA6), 8.6 (v br., HA3), 8.32 (s, 1 H, HHC=N),
8.24 (t, J = 7.3 Hz, 2 H, HA4), 7.98 (dd, J = 7.8, 1.5 Hz 2 H, HC2),
7.77 (dd, J = 7.5, 5.0 Hz, 2 H, HA5), 7.50 (m, 3 H, C3+4) ppm;
signal for HB3 not observed at 295 K. 13C{1H} NMR (125 MHz,
[D6]DMSO, 295 K): δ = 149.1 (CA6), 147.0 (CC=N), 139.4 (CA4),
133.8 (CC1), 130.5 (CC4), 128.9 (CC3), 127.6 (CC2), 126.8 (CA5),
122.4 (br., CA3) ppm, CA2,B2,B3,B4 not observed . ES-MS: m/z = 352
[H1]+. C22H19N7O6·0.25H2O (401.94): calcd. C 54.83, H 4.08, N
20.34; found C 54.93, H 3.93, N 20.11.
1: [H21][MeOSO3]2 (0.50 g, 0.87 mmol) was dissolved in water
(100 cm3) to give a yellow solution. Solid K2CO3 was added until
a colourless solution was obtained. The solution became almost
colourless and was extracted into CH2Cl2 (3ϫ50 cm3) and the
solution was dried with Na2SO4. Solvent was removed to give neu-
tral 1 which was purified by chromatography using a short column
(alumina, CH2Cl2 with 1% MeOH). 1 was isolated as a white solid
(0.25 g, 0.71 mmol, 82%); m.p. 210–212 °C. 1H NMR (500 MHz,
[D6]DMSO, 295 K): δ = 11.14 (HNH), 8.74 (ddd, J = 4.7, 1.7,
0.8 Hz, 2 H, HA6), 8.62 (td, J = 8.0, 1.0 Hz, 2 H, HA3), 8.16 (br.,
HB3), 8.06 (s, 1 H, HHC=N), 7.99 (td, J = 7.6, 1.8 Hz, 2 H, HA4),
7.76 (dd, J = 7.2, 1.3 Hz, 2 H, HC2), 7.48 (m, 4 H, HA5+C3), 7.39
(tt, J = 7.3, 1.3 Hz, 1 H, HC4) ppm. 13C{1H} NMR (125 MHz,
[D6]DMSO, 295 K): δ = 155.5, (CA2/B2), 155.4 (CA2/B2), 152.7 (CB4),
149.2 (CA6), 140.7 (CC=N), 137.2 (CA4), 134.8 (CC1), 129.1 (CC4),
[H21]Cl2: The method and scale were as for [H21][MeOSO3]2, re-
placing concentrated H2SO4 by HCl. [H21]Cl2 was isolated as a
bright yellow powder (0.17 g, 0.40 mmol, 53%). 1H NMR
(500 MHz, [D6]DMSO, 295 K): δ = 12.66 (s, HNH), 8.93 (d, J =
4.3 Hz, 2 H, HA6), 8.62 (br., HA3), 8.37 (s, 1 H, HHC=N), 8.24 (t, J
= 7.6 Hz, 2 H, HA4), 7.97 (d, J = 7.0 Hz 2 H, HC2), 7.77 (dd, J =
6.5, 4.9 Hz, 2 H, HA5), 7.51 (m, 3 H, HC3+4), signal for HB3 not
observed at 295 K ppm. 13C{1H} NMR (125 MHz, [D6]DMSO,
295 K): δ = 155.6 (CA2+B2), 149.1 (CA6), 147.9 (CC=N), 139.4 (CA4),
133.8 (CC1), 130.4 (CC4), 128.9 (CC3), 127.5 (CC2), 126.7 (CC5),
122.4 (CA3), 104 (br., CB3) ppm, CB4 not observed. ES-MS: m/z =
352 [H1]+. C22H19Cl2N5·3.5H2O (487.38): calcd. C 54.22, H 5.38,
N 14.37; found C 54.02, H 5.02, N 14.40.
128.9 (CC3), 126.3 (CC2), 124.2 (CA5), 120.8 (CA3), 103.8 (br., CB3
)
ppm. ES-MS: m/z = 352 [H1]+. C22H17N5·H2O (369.42): calcd. C
71.53, H 5.18, N 18.96; found C 71.62, H 4.97, N 18.88.
[H21][PF6]2: HPF6 (60% in water, 2 cm3) was added to a solution of
1 (0.10 g, 0.28 mmol) in EtOH (30 cm3). A bright yellow precipitate
which formed was collected by fitration and washed with EtOH
(10 cm3). The solid was dissolved in acetone, HPF6 (1 cm3) was
added and the solution was filtered to remove a small amount of
solid material. Et2O was added and the resulting yellow precipitate
was collected. [H21][PF6]2 (0.036 g, 0.056 mmol, 20%). 1H NMR
(500 MHz, [D6]DMSO, 360 K): δ = 11.74 (s, HNH), 8.86 (d, J =
4.7 Hz, 2 H, HA6), 8.54 (d, J = 7.9 Hz, HA3), 8.28 (s, 1 H, HHC=N),
8.15 (dt, J = 7.9, 1.6 Hz, 2 H, HA4), 8.10 (s, 2 H, HB3), 7.89 (d, J
= 6.9 Hz, 2 H, HC2), 7.67 (dd, J = 7.1, 5.2 Hz, 2 H, HA5), 7.49 (m,
3 H, HC3+4) ppm. 1H NMR (500 MHz, [D6]DMSO, 295 K): δ =
12.25 (s, HNH), 8.92 (d, J = 4.4 Hz, 2 H, HA6), 8.62 (br., HA3), 8.31
(s, 1 H, HHC=N), 8.23 (t, J = 7.7 Hz, 2 H, HA4), 8.10 (v br., HB3),
7.97 (d, J = 6.9 Hz, 2 H, HC2), 7.76 (dd, J = 6.8, 5.1 Hz, 2 H, HA5),
7.52 (m, 3 H, HC3+4) ppm. 13C{1H} NMR (125 MHz, [D6]DMSO,
295 K): δ = 155.8 (CA2+B2), 149.2 (CA6), 147.3 (CC=N), 139.5 (CA4),
133.7 (CC1), 130.6 (CC4), 128.9 (CC3), 127.7 (CC2), 126.9 (CA5) ppm,
[H1][BF4]: [H21][MeOSO3]2 (0.10 g, 0.17 mmol) was dissolved in a
minimum volume of hot water and excess NaBF4 was added. The
yellow-green precipitate that formed was collected by filtration and
washed with water and cold EtOH. [H1][BF4] was isolated as a pale
1
yellow solid (0.070 g, 0.16 mmol, 92%). H NMR (500 MHz, [D6]
DMSO, 360 K): δ = 11.42 (br., HNH), 8.82 (d, J = 4.8 Hz, 2 H,
HA6), 8.55 (d, J = 8.0 Hz, HA3), 8.22 (s, 1 H, HHC=N), 8.11 (s, 2 H,
HB3), 8.09 (t, J = 7.4 Hz, 2 H, HA4), 7.96 (d, J = 6.4 Hz, 2 H, HC2),
7.75 (ddd, J = 7.7, 4.9, 0.8 Hz, 2 H, HA5), 7.5 (m, 3 H, HC3+4
)
ppm. 1H NMR (500 MHz, [D6]DMSO, 295 K): δ = 12.23 (br.,
HNH), 8.91 (d, J = 4.3 Hz, 2 H, HA6), 8.6 (v br., HA3,B3), 8.29 (s, 1
H, HHC=N), 8.21 (t, J = 7.4 Hz, 2 H, HA4), 7.96 (d, J = 6.4 Hz, 2
H, HC2), 7.75 (t, J = 7.7 Hz, 2 H, HA5), 7.5 (m, 3 H, HC3+4) ppm.
13C{1H} NMR (125 MHz, [D6]DMSO, 295 K): δ = 155.6 (CB4),
149.3 (CA6), 148.0 (CA2+B2), 146.8 (CC=N), 139.2 (CA4), 133.8 (CC1),
130.5 (CC4), 128.9 (CC3), 127.6 (CC2), 126.8 (CA5), 122.4 (br., CA3),
CA3,B3,B4 not observed. ES-MS: m/z
=
352 [H1]+.
C22H18F12N5P2·1.5H2O (669.36): calcd. C 39.42, H 3.31, N 10.45;
found C 39.69, H 3.26, N 10.14.
104.1 (br., CB3
)
ppm. ES-MS: m/z
=
352 [H1]+.
C22H18BF4N5·1.5H2O (466.24): calcd. C 56.67, H 4.54, N 15.02;
found C 57.02, H 4.37, N 15.07.
[H22][MeOSO3]2: 4Ј-Hydrazino-2,2Ј:6Ј,2ЈЈ-terpyridine (0.20 g,
0.76 mmol) was dissolved in hot methanol (15 cm3), and excess ace-
[H1][PF6]: An excess of NH4PF6 was added to a solution of tophenone (0.10 g, 0.83 mmol) was added giving a colourless solu-
[H21][MeOSO3]2 (0.10 g, 0.17 mmol) dissolved in a minimum vol-
ume of hot water. A pale yellow precipitate formed and was col-
lected by fitration, washed with water and cold EtOH. [H1][PF6]
was isolated as a pale yellow solid (0.042 g, 0.084 mmol, 49%).
Slow evaporation of a solution of [H1][PF6] in acetone/water (5:1)
gave X-ray-quality crystals of [H1][PF6]·H2O. 1H NMR (500 MHz, as
[D6]DMSO, 360 K): δ = 11.45 (br., HNH), 8.82 (d, J = 4.7 Hz, 2 H,
HA6), 8.55 (d, J = 8.0 Hz, HA3), 8.22 (s, 1 H, HHC=N), 8.11 (s, 2 H,
tion. A few drops of concentrated H2SO4 were added, and a bright
yellow precipitate formed after heating the mixture for a few min-
utes. The suspension was heated at reflux for 3 h and then cooled
to room temperature. The bright yellow solid was collected by fil-
tration and washed well with MeOH. [H22][MeOSO3]2 was isolated
a
yellow powder (0.45 g, 0.76 mmol, 100%). 1H NMR
(500 MHz, [D6]DMSO, 360 K): δ = 11.28 (s, HNH), 8.93 (d, J =
4.4 Hz, 2 H, HA6), 8.57 (br., HA3), 8.28 (s, 2 H, HB3), 8.25 (t, J =
HB3), 8.09 (dt, J = 7.8, 1.7 Hz, 2 H, HA4), 7.84 (d, J = 7.0 Hz, 2 7.7 Hz, 2 H, HA4), 8.04 (dd, J = 7.7, 1.4 Hz, 2 H, HC2), 7.78 (dd,
H, HC2), 7.75 (dd, J = 7.5, 4.7 Hz, 2 H, HA5), 7.50 (m, 3 H, HC3+4
)
J = 6.8, 5.2 Hz, 2 H, HA5), 7.50 (m, 3 H, C3+4), 3.38 (s, HOMe, see
3578
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3569–3581

4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine
text), 2.50 (HCMe, overlaps with solvent peak) ppm. 13C{1H} NMR observed. ES-MS: m/z = 428 [H3]+. C30H29N5O8S2·2H2O (687.74):
(125 MHz, [D6]DMSO, 295 K): δ = 149.2 (CA6), 139.5 (CA4), 128.5 calcd. C 52.39, H 4.84, N 10.18; found C 52.28, H 4.67, N 10.22.
(CC3,C4), 126.8 (CA5), 126.5 (CC2), 14.4 (CMeC
)
ppm,
[H3][BF4]: [H23][MeOSO3]2 (0.20 g, 0.31 mmol) was dissolved in
hot water (10 cm3) and excess NaBF4 was added. After stirring at
room temperature for 1 h, the resulting solid was collected and
washed well with water and cold EtOH. [H3][BF4] was isolated as
CA2,A3,B2,B3,B4,C1,C=N not observed. ES-MS: m/z = 366 [H2]+.
C25H27N5O8S2·0.75H2O (603.15): calcd. C 49.78, H 4.76, N 11.61;
found , C 49.72, H 4.61, N 11.41.
1
a green-yellow powder (0.06 g, 0.12 mmol, 37%). H NMR ([D6]-
[H2][BF4]: [H22][MeOSO3]2 (0.10 g, 0.17 mmol) was dissolved in a
minimum volume of hot water and an excess of NaBF4 was added.
The mixture was heated to 50 °C and was maintained at this tem-
perature with stirring for 1 h, after which time a yellow-green solid
had formed. The precipitate was collected by filtration and was
washed well with water and cold EtOH. [H2][BF4] was isolated as
DMSO, 295 K): δ = 10.53 (s, 1 H, NH), 8.86 (br.d, J = 3.3 Hz, 2
H, HA6), 8.53 (br. s, 2 H, HA3), 8.33 (br. s, 2 H, HB3), 8.17 (t, J =
7.1 Hz, 2 H, HA4), 7.66 (m, 7 H, HA5+C/E), 7.46 (dq, J = 4.9, 1.7 Hz,
3 H, HC/E), 7.45 (d, J = 3.3 Hz, 2 H, HC2) ppm. 13C{1H} NMR
([D6]DMSO, 295 K): δ = 149.2 (CA6), 138.8 (CA4), 137.4 (CC1/E1),
132.4 (CC1/E1), 129.8 (CC4/E4), 129.7 (CC4/E4), 129.5 (CC/E2/3), 129.0
(CC/E2/3), 128.6 (CC/E2/3), 127.4 (CC/E2/3), 126.1 (CA5), 122.0 (HA3),
105.4 (HB3) ppm, CA2,B2,B4,C=N not observed. ES-MS: m/z = 428
[H3]+. C28H22BF4N5·H2O (533.33): calcd. C 63.06, H 4.54, N
13.13; found C 62.86, H 4.16, N 12.93.
a
yellow-green solid (0.062 g, 0.13 mmol, 80%). 1H NMR
(500 MHz, [D6]DMSO, 360 K): δ = 10.67 (br., HNH), 8.81 (ddd, J
= 4.3, 1.7, 0.9 Hz, 2 H, HA6), 8.46 (dt, J = 8.0, 1.0 Hz, 2 H, HA3),
8.22 (s, 2 H, HB3), 8.09 (dt, J = 8.0, 1.7 Hz, 2 H, HA4), 7.91 (dd, J
= 8.3, 1.4 Hz, 2 H, HC2), 7.61 (ddd, J = 7.6, 4.8, 1.1 Hz, 2 H, HA5),
7.44 (m, 3 H, HC3+4), 2.47 (CMe) ppm. 13C{1H} NMR (125 MHz,
[D6]DMSO, 295 K): δ = 149.3 (CA6), 139.2 (CA4), 137.6 (CC1),
3: [H23][MeOSO3]2 (0.25 g, 0.38 mmol) was dissolved in H2O
(10 cm3), and solid K2CO3 (5 g) was added. CH2Cl2 (50 cm3) was
added and the biphasic mixture was sonicated for 1 h. The two
phases were separated and the aqueous layer extracted with CH2Cl2
(3ϫ300 cm3). The combined organic fractions were dried with
Na2SO4 and the solvent was removed to give 3 as a pale orange
microcrystalline solid which was recrystallised from EtOH/CH2Cl2
to give 3 as an off-white solid (0.065 g, 0.15 mmol, 40%); m.p. 212–
129.6 (CC4), 128.6 (CC3), 126.6 (CC2), 126.4 (CA5), 122.3 (CA3),
B4,A2,B2,C=N
104.5 (br., CB3), 14.3 (CMe) ppm, C
not observed. ES-
MS: m/z = 366 [H2]+. C23H20BF4N5·0.5H2O (462.25): calcd. C
59.76, H 4.58, N 15.15; found C 59.93, H 4.41, N 15.17.
2: [H22][MeOSO3]2 (0.30 g, 0.51 mmol) was dissolved in warm H2O
(10 cm3) and the mixture was filtered through fluted filter paper to
remove a small amount of solid impurities. Solid K2CO3 was added
to the cream precipitate that formed was extracted into CH2Cl2
(3ϫ100 cm3) and dried with Na2SO4. Removal of the solvent gave
2 which was purified by chromatography using a short column (alu-
mina, CH2Cl2 with 1% MeOH). 2 was isolated as an off-white solid
(0.11 g, 0.30 mmol, 58%); m.p. 192–193 °C. 1H NMR (500 MHz,
[D6]DMSO, 295 K): δ = 10.13 (s, HNH), 8.72 (d, J = 4.1 Hz, 2 H,
HA6), 8.61 (d, J = 7.9 Hz, 2 H, HA3), 8.33 (s, 2 H, HB3), 7.99 (t, J
= 7.6 Hz, 2 H, HA4), 7.85 (d, J = 7.3 Hz, 2 H, HC2), 7.47 (m, 4 H,
HC3+A5), 7.39 (m, 1 H, HC4), 2.37 (s, 3 H, HMe) ppm. 13C{1H}
NMR (125 MHz, [D6]DMSO, 295 K): δ = 155.7, (CA2+B2), 153.5
(CB4), 149.1 (CA6), 145.1 (CC=N), 138.8 (CC1), 137.2 (CA4), 128.5
(CC3), 128.4 (CC4), 125.7 (CC2), 124.1 (CA5), 120.7 (CA3), 104.3 (br.,
1
214 °C. H NMR ([D6]DMSO, 295 K): δ = : 9.89 (s, NH), 8.69 (d,
J = 3.9 Hz, HA6), 8.60 (d, J = 7.9 Hz, HA3), 8.34 (s, HB3), 7.97 (td,
J = 7.7, 1.7 Hz, HA4), 7.61 (m, 3 H, HC/E3+4), 7.51 (dd, J = 8.3,
1.4 Hz, 2 H, HC2/E2), 7.46 (ddd, J = 7.4, 4.7, 1.1 Hz, HA5), 7.41 (m,
3 H, HC/E3+4), 7.37 (dd, J = 8.0, 1.5 Hz, 2 H, HC2/E2) ppm. 13C{1H}
([D6]DMSO, 295 K) δ /ppm 155.7 (CA2/B2), 155.3 (CA2/B2), 153.1
(CB4), 149.1 (CA6), 147.3 (C=N), 138.3 (CC1/E1), 137.1 (CA4), 133.0
(CC1/E1), 129.4 (CC3/E3), 129.2 (CC4/E4), 129.1 (CC3/E3), 128.6 (CC4/
E4), 128.5 (CC3/E3), 126.6 (CC2/E2), 124.1 (CA5), 120.7 (CA3), 105.0
(CB3). ES-MS: m/z = 428 [H3]+. C28H21N5·0.5H2O (436.51): calcd.
C 77.04, H 5.08, N 16.04; found C 76.75, H 4.97, N 16.05.
[H24][MeOSO3]2: Excess benzaldehyde (0.10 g, 0.94 mmol) was
added to a solution of 4Ј-(1-methylhydrazino)-2,2Ј:6Ј,2ЈЈ-terpyrid-
ine (0.20 g, 0.72 mmol) in hot methanol(15 cm3). Upon the ad-
dition of a few drops of concentrated H2SO4 followed by stirring
for a few minutes, the cloudy reaction mixture converted into a
pale yellow solution. This was heated under reflux for 12 h, after
which time it was cooled to room temperature. Et2O was added
until a cream precipitate began to form.The reaction mixture was
left in the freezer overnight and was then filtered. The solid residue
was washed well with Et2O, and [H24][MeOSO3]2 was isolated as a
pale yellow microcrystalline solid (0.33 g, 0.56 mmol, 78%). 1H
NMR (500 MHz, [D6]DMSO, 295 K): δ = 8.94 (d, J 4.6 Hz, 2 H,
HA6), 8.81 (d, J 8.0 Hz, 2 H, HA3), 8.46 (s, 2 H, HB3), 8.37 (s, 1 H,
HHC=N), 8.24 (t, J 7.5 Hz, 2 H, HA4), 8.00 (d, J 7.2 Hz, 2 H, HC2),
7.80 (dd, J 7.2, 5.2 Hz, 2 H, HA5), 7.54 (m, 2 H, HC3,C4), 3.83 (s,
3 H, HMe), 3.37 (s, HOMe, see text) ppm. 13C{1H} NMR (125 MHz,
[D6]DMSO, 295 K): δ = 157.1 (CB4), 147.7 (CA2,B2), 149.0 (CA6),
144.1 (CC=N), 139.3 (CA4), 134.5 (CC1), 130.3 (CC4), 129.0 (CC3),
126.9 (CC2), 126.4 (CA5), 122.5 (CA3), 105.8 (CB3), 52.8 (COMe),
33.3 (CMe) ppm. ES-MS: m/z = 366 [H4]+. C25H27N5O8S2·H2O
(607.66): calcd. C 49.41, H 4.81, N 11.53; found C 49.37, H 4.55,
N 11.66.
CB3), 13.6 (CMe
)
ppm. ES-MS: m/z
=
366 [H2]+.
C23H19N5·0.33H2O (371.38): calcd. C 74.38, H 5.34, N 18.86;
found C 74.58, H 5.37, N 18.72.
[H23][MeOSO3]2: Excess benzophenone (0.16 g, 0.87 mmol) and
4Ј-hydrazino-2,2Ј:6Ј,2ЈЈ-terpyridine (0.20 g, 0.76 mmol) were dis-
solved in hot MeOH (20 cm3). A few drops of concentrated H2SO4
were added to the solution and a white precipitate formed which
redissolved on heating. The solution was heated at reflux for 3 h
to ensure that the reaction had reached completion. On cooling the
reaction mixture to room temperature, only a small amount of solid
precipitated. Et2O was added to afford [H23][MeOSO3]2 as a bright
yellow powder which was collected and washed with MeOH
(0.42 g, 0.64 mmol, 85%). 1H NMR (500 MHz, [D6]DMSO,
295 K): δ = 10.74 (s, 1 H, NH), 8.92 (d, J = 3.8 Hz, 2 H, HA6), 8.6
(v br., 2 H, HA3), 8.33 (br., 2 H, HB3), 8.24 (br.dd, J = 7.8, 4.6 Hz,
2 H, HA4), 7.77 (br.dd, J = 5.7, 4.0 Hz, 2 H, HA5), 7.67 (m, 5 H,
HC/E), 7.46 (m, 5 H, HC/E), 3.37 (s, 6 H, HMe) ppm. 1H NMR ([D6]-
DMSO, 360 K): δ = 10.20 (s, NH), 8.84 (d, J = 4.7 Hz, 2 H, HA6),
8.48 (d, J = 7.9 Hz, 2 H, HA3), 8.30 (s, 2 H, HB3), 8.13 (td, J = 7.8,
1.6 Hz, 2 H, HA4), 7.66 (m, 7 H, HA5+C/E), 7.45 (m, 3 H, HC/E),
7.42 (dd, J = 7.8. 1.5 Hz, 2 H, HC/E) ppm. 13C{1H} NMR ([D6]-
[H4][BF4]: [H24][MeOSO3]2 (0.15 g, 0.26 mmol) was dissolved in a
DMSO, 295 K): δ = 149.1 (CA6), 139.1 (CA4), 126.7 (CA5), 132.3 hot 1: 4 MeOH/H2O (50 cm3) mixture and excess aqueous solution
(CC/E1), 137.1 (CC/E1), 130.0 (CC/E), 129.6 (CC/E), 129.0 (CC/E),
128.6 (CC/E), 127.7 (CC/E), 52.8 (CMe) ppm, CA2,A3,B2,B3,B4,C=N not
of NaBF4 was added to give a pale yellow precipitate which was
collected and washed well with water and a little MeOH (0.096 g,
Eur. J. Org. Chem. 2008, 3569–3581
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3579

E. C. Constable, C. E. Housecroft et al.
FULL PAPER
0.21 mmol, 83%). 1H NMR (500 MHz, [D6]DMSO, 295 K): δ = β = 98.8945(5)°, U = 4334.60(8) Å3, Z = 8, Dc = 1.389 Mgm–3,
8.90 (d, J = 4.4 Hz, 2 H, HA6), 8.76 (d, J = 8.2 Hz, 2 H, HA3), 8.45
(s, 2 H, HB3), 8.30 (s, 1 H, HHC=N), 8.21 (t, J = 7.4 Hz, 2 H, HA4),
µ(Mo-Kα) = 0.108 mm–1, T = 173 K, 6359 reflections collected. Re-
finement of 3549 reflections (335 parameters) with I Ͼ3.0σ (I) con-
7.96 (d, J = 7.3 Hz, 2 H, HC2), 7.72 (dd, J = 7.0, 5.0 Hz, 2 H, HA5), verged at final R1 = 0.0530 [R1 (all data) = 0.0821], wR2 = 0.0511
7.54 (t, J = 7.4 Hz, 2 H, HC3), 7.48 (t, J = 7.3 Hz, HC4), 3.78 (s, 3
H, HMe) ppm. 13C{1H} NMR (125 MHz, [D6]DMSO, 295 K): δ =
149.1 (CA6), 145.5 (CC=N), 138.9 (CA4), 130.0 (CC4), 129.0 (CC3),
127.5 (CC2), 126.2 (CA5), 122.3 (CA3), 105.7 (CB3), 39.5 (CMe) ppm,
CA2,B2,B4,C1 not observed. ES-MS: m/z = 366 [H4]+, 388 [4 +
Na]+, 753 [2(4) + Na]+. C23H20BF4N5·0.75H2O (466.76): calcd. C
59.18, H 4.64, N 15.00; found C 59.27, H 4.33, N 14.92.
[wR2 (all data) = 0.0630], gof = 1.297.
Crystal Data for [H22][NO3][MeOSO3]·H2O: C24H26N6O8S, M =
588.57, monoclinic, space group P21/c, a = 8.3471(4), b = 27.284(1),
c = 11.7194(4) Å, β = 106.504(3)°, U = 2559.0(2) Å3, Z = 4, Dc =
1.450 Mgm–3, µ(Mo-Kα) = 0.188 mm–1, T = 173 K, 5797 reflections
collected. Refinement of 3348 reflections (352 parameters) with I
Ͼ1.0σ (I) converged at final R1 = 0.0690 [R1 (all data) = 0.1279],
wR2 = 0.0671 [wR2 (all data) = 0.0944], gof = 1.125.
4: [H24][MeOSO3]2 (0.10 g, 0.17 mmol) was dissolved in H2O
(10 cm3) and solid K2CO3 was added until a preciptate formed. The
cream solid was extracted into CH2Cl2 (3ϫ30 cm3), the combined
extracts were dried with MgSO4 and the solvent was removed. The
residue was recrystallised from CH2Cl2/EtOH (with added solid
K2CO3 to ensure complete deprotonation). Compound 4 was iso-
lated as a cream microcrystalline solid (0.015 g, 0.041 mmol, 24%);
m.p. 211–212 °C. 1H NMR (500 MHz, [D6]DMSO, 295 K): δ =
8.75 (ddd, J = 4.8, 1.6, 0.8 Hz, 2 H, HA6), 8.63 (d, J = 7.9 Hz, 2
H, HA3), 8.42 (s, 2 H, HB3), 8.03 (s, 1 H, HHC=N), 8.00 (td, J = 7.8,
1.8 Hz, 2 H, HA4), 7.81 (d, J = 7.3 Hz, 2 H, HC2), 7.49 (m, 4 H,
HC3+A5), 7.40 (t, J = 7.3 Hz, 1 H, HC4), 3.60 (s, 3 H, HMe) ppm.
13C{1H} NMR (125 MHz, [D6]DMSO, 295 K): δ = 155.7 (CA2/B2),
155.6 (CA2/B2), 154.6 (CB4), 149.3 (CA6), 139.4 (CA4), 137.4 (CC =
N), 135.8 (CC1), 129.0 (CC3+C4), 126.6 (CC2), 124.4 (CA5), 121.1
(CA3), 105.4 (CB3), 32.8 (CMe) ppm. ES-MS: m/z = 366 [H4]+.
C23H19N5·H2O (383.45): calcd. C 72.04, H 5.52, N 18.26; found C
72.00, H 5.25, N 18.07.
Crystal Data for 2: C23H19N5, M = 365.44, monoclinic, space
group P21/n, a = 16.547(1), b = 5.4934(4), c = 20.324(1) Å, β =
99.378(3)°, U = 1822.8(2) Å3, Z = 4, Dc = 1.332 Mgm–3, µ(Mo-Kα)
= 0.082 mm–1, T = 173 K, 3887 reflections collected. Refinement
of 2614 reflections (253 parameters) with I Ͼ1.0σ (I) converged at
final R1 = 0.0447 [R1 (all data) = 0.0752], wR2 = 0.0523 [wR2 (all
data) = 0.0714], gof = 1.139.
Crystal Data for [H3][MeOSO3]: C29H25N5O4S, M = 539.61, mo-
noclinic, space group P21/c, a = 8.9734(3), b = 23.860(1), c =
12.3514(3) Å, β = 105.356(2)°, U = 2550.1(2) Å3, Z = 4, Dc
=
1.405 Mgm–3, µ(Mo-Kα) = 0.174 mm–1, T = 173 K, 5813 reflections
collected. Refinement of 3582 reflections (352 parameters) with I
Ͼ1.7σ (I) converged at final R1 = 0.0495 [R1 (all data) = 0.0873],
wR2 = 0.0543 [wR2 (all data) = 0.0684], gof = 1.150.
Crystal Data for 3·CH2Cl2: C29H23Cl2N5, M = 512.44, monoclinic,
space group P21/c, a = 10.8031(4), b = 9.6855(4), c = 24.417(1) Å,
β = 99.785(2)°, U = 2517(2) Å3, Z = 4, Dc = 1.352 Mgm–3, µ(Mo-
Kα) = 0.286 mm–1, T = 173 K, 4905 reflections collected. Refine-
ment of 3632 reflections (325 parameters) with I Ͼ3.0σ (I) con-
verged at final R1 = 0.0379 [R1 (all data) = 0.0507], wR2 = 0.0441
[wR2 (all data) = 0.0554], gof = 1.111.
Crystal Structure Determinations. General: Data were collected on
a Bruker–Nonius Kappa or Stoe IPDS CCD instrument; data re-
duction, solution and refinement used the programs COLLECT[52]
and SIR92[53] or XRED[54] and SHELXS86,[55] DENZO/SCALE-
PACK[56] and CRYSTALS.[57] Structures have been analysed using
Mercury v. 1.4.2,[58] and searches for related structures carried out
in the Cambridge Structural Database (v. 5.28)[59] using Conquest
v. 1.9.[58]
Crystal Data for 4: C23H19N5, M = 365.44, monoclinic, space
group P21/n, a = 13.7297(8), b = 8.5408(5), c = 15.9176(9) Å, β =
102.628(4)°, U = 1821.4(2) Å3, Z = 4, Dc = 1.333 Mgm–3, µ(Mo-
Kα) = 0.082 mm–1, T = 173 K, 4369 reflections collected. Refine-
ment of 2626 reflections (253 parameters) with I Ͼ1.5σ (I) con-
verged at final R1 = 0.0454 [R1 (all data) = 0.0851], wR2 = 0.0562
[wR2 (all data) = 0.0760], gof = 1.110.
Crystal Data for 1: C22H17N5, M = 351.41, monoclinic, space
group C2/c, a = 14.0879(8), b = 12.5006(6), c = 20.1787(9) Å, β =
94.112(3)°, U = 3544.5(3) Å3, Z = 8, Dc = 1.317 Mgm–3, µ(Mo-Kα)
= 0.082 mm–1, T = 173 K, 4058 reflections collected. Refinement
of 2306 reflections (244 parameters) with I Ͼ2.0σ (I) converged at
final R1 = 0.0394 [R1 (all data) = 0.0845], wR2 = 0.0428 [wR2 (all
data) = 0.0782], gof = 0.919.
CCDC-681421 (for [H21]Cl2·DMSO), -681422 (for [H22][NO3]-
[MeOSO3]·H2O), -681423 (for [H1][PF6]·H2O), -681424 (for
[H2][BF4]), -681425 (for [H3][MeOSO3]), -681426 (for 1), -681427
(for 2), -681428 (for 3·CH2Cl2) and -681429 (for 4) contain 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.
Crystal Data for [H1][PF6]·H2O: C22H20F6N5O1P1, M = 515.40,
¯
triclinic, space group P1, a = 8.5007(7), b = 11.4295(7), c =
12.079(1) Å, α = 75.730(5), β = 89.492(4), γ = 85.558(5)°, U =
1133.9(2) Å3, Z = 2, Dc = 1.509 Mgm–3, µ(Mo-Kα) = 0.197 mm–1,
T = 173 K, 5171 reflections collected. Refinement of 2616 reflec-
tions (316 parameters) with I Ͼ1.0σ (I) converged at final R1 =
0.0955 (R1 (all data) = 0.1851), wR2 = 0.0898 [wR2 (all data) =
0.1395], gof = 1.020.
Supporting Information (see footnote on the first page of this arti-
cle): Table S1 (hydrogen-bonded interactions in [H22][NO3]-
[MeOSO3]·H2O); Figure S1 (packing of [H22]2+ cations in
[H22][NO3][MeOSO3]·H2O); Figure S2 (packing of [H1]+ cations in
[H1][PF6]·H2O); Figure S3 packing of [H2]+ cations and associa-
Crystal Data for [H21]Cl2·DMSO: C24H25Cl2N5O1S1, M = 502.47,
¯
triclinic, space group P1, a = 7.228(1), b = 13.115(3), c =
13.320(3) Å, α = 77.47(3), β = 74.47(3), γ = 86.72(3)°, U =
1187.7(5) Å3, Z = 2, Dc = 1.405 Mgm–3, µ(Mo-Kα) = 0.389 mm–1,
T = 173 K, 10344 reflections collected. Refinement of 6375 reflec-
tions (298 parameters) with I Ͼ2.0σ (I) converged at final R1 =
0.0528 [R1 (all data) = 0.0826], wR2 = 0.0491 [wR2 (all data) =
0.0618], gof = 1.079.
–
tion with BF4 anions in [H2][BF4].
Acknowledgments
Crystal Data for [H2][BF4]: C23H20BF4N5, M = 453.25, monoclinic,
space group C2/c, a = 21.8489(2), b = 13.7414(1), c = 14.6131(2) Å,
We thank the Swiss National Science Foundation and the Univer-
sity of Basel for financial support.
3580
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3569–3581

4Ј-Hydrazone Derivatives of 2,2Ј:6Ј,2"-Terpyridine
[30]
[31]
A. L. Spek, J. Appl. Crystallogr. 2003, 36, 7–13.
M. G. B. Drew, G. R. Willey, J. Chem. Soc. Perkin Trans. 2
1986, 215–220.
G. Tosi, L. Cardellini, G. Bocelli, Acta Crystallogr., Sect. B
1988, 44, 55–63.
E. Chiba, K. Tani, M. Shuto, N. Haga, M. Tokonami, Acta
Crystallogr., Sect. C 1990, 46, 414–417.
M. Nagel, R. Allmann, Cryst. Struct. Commun. 1981, 10, 905–
908.
G. Tosi, P. Bruni, L. Cardellini, G. Bocelli, Gazz. Chim. Ital.
1984, 114, 111–115.
M. G. B. Drew, M. J. Hudson, P. B. Iveson, M. L. Russell, J.-
O. Liljenzin, M. Skålberg, L. Spjuth, C. Madic, J. Chem. Soc.,
Dalton Trans. 1998, 2973–2980.
C. J. Kepert, B. W. Skelton, A. H. White, Aust. J. Chem. 1994,
47, 391–396.
C. Berthon, M. S. Grigoriev, Acta Crystallogr., Sect. E 2005,
61, o1216–o1217.
I. A. Charushnikova, C. Den Auwer, Russ. J. Coord. Chem.
2004, 30, 511–519.
[1] C. Serbutoviez, C. Bosshard, G. Knöpfle, P. Wyss, P. Prêtre, P.
Günter, K. Schenk, E. Solari, G. Chapuis, Chem. Mater. 1995,
7, 1198–1206.
[2] D. Lupo, H. Ringsdorf, A. Schuster, M. Seitz, J. Am. Chem.
Soc. 1994, 116, 10498–10506.
[3] D. Saravanakumar, S. Devaraj, S. Iyyampillai, K. Mohandoss,
M. Kandaswamy, Tetrahedron Lett. 2008, 49, 127–132.
[4] D. Millán, M. Domínguez, M. C. Rezende, Dyes Pigm. 2008,
77, 441–445.
[32]
[33]
[34]
[35]
[36]
[5] R. S. Becker, F. Chagneau, J. Am. Chem. Soc. 1992, 114, 1373–
1381.
[6] V. Getautis, J. V. Grazulevicius, M. Daskeviciene, T. Mali-
nauskas, V. Jankauskas, J. Sidaravicius, A. Undzenas, Eur. Po-
lym. J. 2007, 43, 3597–3603.
[7] C. A. M. Fraga, E. J. Barreiro, Curr. Med. Chem. 2006, 13,
167–198.
[8] S. Rollas, S. G. Küçükgüzel, Molecules 2007, 12, 1910–1939.
[9] C. M. Armstrong, P. V. Bernhardt, P. Chin, D. R. Richardson,
Eur. J. Inorg. Chem. 2003, 1145–1156.
[10] P. V. Bernhardt, P. Chin, P. C. Sharpe, D. R. Richardson, Dal-
ton Trans. 2007, 3232–3244.
[11] J.-L. Schmitt, A.-M. Stadler, N. Kyritsakas, J.-M. Lehn, Helv.
Chim. Acta 2003, 86, 1598–1624.
[12] J.-L. Schmitt, J.-M. Lehn, Helv. Chim. Acta 2003, 86, 3417–
3426.
[13] K. M. Gardinier, R. G. Khoury, J.-M. Lehn, Chem. Eur. J.
2000, 6, 4124–4131.
[14] A.-M. Stadler, N. Kyritsakas, J.-M. Lehn, Chem. Commun.
2004, 2024–2025.
[37]
[38]
[39]
[40]
[41]
K. N. Robertson, P. K. Bakshi, S. D. Lantos, T. S. Cameron, O.
Knop, Can. J. Chem. 1998, 76, 583–611.
M. G. B. Drew, P. B. Iveson, M. J. Hudson, J.-O. Liljenzin, L.
Spjuth, P.-Y. Cordier, Å. Enarsson, C. Hill, C. Madic, J. Chem.
Soc., Dalton Trans. 2000, 821–830.
W. Huang, H. Qian, J. Mol. Struct. 2007, 832, 108–116.
A. Hergold-Brundic´, Z. Popovic´, D. Matkowic´-Calogovic´, Acta
Crystallogr., Sect. C 1996, 52, 3154–3157.
A. Kochel, Acta Crystallogr., Sect. E 2006, 62, m37–m38.
See for example: G. R. Newkome, N. S. Bhacca, J. Org. Chem.
1971, 36, 1719–1720; A. F. Hegarty, P. J. Moroney, F. L. Scott,
J. Chem. Soc. Perkin Trans. 2 1973, 1466–1471.
L. Lunazzi, C. Magagnoli, M. Guerra, D. Macciantelli, Tetra-
hedron Lett. 1979, 20, 3031–3032.
[42]
[43]
[44]
[45]
[15] A.-M. Stadler, N. Kyritsakas, G. Vaughan, J.-M. Lehn, Chem.
Eur. J. 2007, 13, 59–68.
[16] L. H. Uppadine, J.-P. Gisselbrecht, J.-M. Lehn, Chem. Com-
mun. 2004, 718–719.
[46]
[47]
[48]
[49]
[50]
[51]
[17] L. H. Uppadine, J.-M. Lehn, Angew. Chem. Int. Ed. 2004, 43,
F. Kaberia, B. Vickery, G. R. Willey, M. G. B. Drew, J. Chem.
Soc. Perkin Trans. 2 1980, 1622–1626.
B. Vickery, G. R. Willey, M. G. B. Drew, Acta Crystallogr.,
Sect. C 1985, 41, 1072–1075.
240–243.
[18] M. Ruben, J.-M. Lehn, G. Vaughan, Chem. Commun. 2003,
1338–1339.
[19] F. Loiseau, F. Nastasi, A.-M. Stadler, S. Campagna, J.-M.
Lehn, Angew. Chem. Int. Ed. 2007, 46, 6144–6147.
[20] A.-M. Stadler, N. Kyritsakas, R. Graff, J.-M. Lehn, Chem. Eur.
J. 2006, 12, 4503–4522.
[21] M. Barboiu, M. Ruben, G. Blasen, N. Kyritsakas, E. Chacko,
M. Dutta, O. Radekovich, K. Lenton, D. J. R. Brook, J.-M.
Lehn, Eur. J. Inorg. Chem. 2006, 784–792.
[22] A.-M. Stadler, F. Puntoriero, S. Campagna, N. Kyritsakas, R.
Welter, J.-M. Lehn, Chem. Eur. J. 2005, 11, 3997–4009.
[23] J. E. Beves, E. L. Dunphy, E. C. Constable, C. E. Housecroft,
C. J. Kepert, M. Neuburger, D. J. Price, S. Schaffner, Dalton
Trans. 2008, 386–396.
[24] J. E. Beves, E. C. Constable, C. E. Housecroft, M. Neuburger,
S. Schaffner, Polyhedron 2008, in press.
[25] G. Lowe, A. S. Droz, T. Vilaiven, G. W. Weaver, L. Tweedale,
J. M. Pratt, P. Rock, V. Yardley, S. L. Croft, J. Med. Chem.
1999, 42, 999–1006.
[26] G. Lowe, A. S. Droz, J. J. Park, G. W. Weaver, Bioorg. Chem.
1999, 27, 477–486.
[27] Z. Zhou, G. H. Sarova, S. Zhang, Z. Ou, F. T. Tat, K. M. Kad-
ish, L. Echegoyen, D. M. Guldi, D. I. Schuster, S. R. Wilson,
Chem. Eur. J. 2006, 12, 4241–4248.
J. L. Cook, C. A. Hunter, C. M. R. Low, A. Perez-Velasco, J. G.
Vinter, Angew. Chem. Int. Ed. 2007, 46, 3706–3709.
See for example: G. J. Karabatos, R. A. Taller, J. Am. Chem.
Soc. 1963, 85, 3624–3629, and ref.[47,48]
.
E. Farkas, É. A. Enyedy, G. Micera, E. Garribba, Polyhedron
2000, 19, 1727–1736.
COLLECT Software, Nonius BV, 1997–2001.
A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr.
1994, 27, 435–435.
XRED, v. 1.08, Stoe & Cie software, 1996.
G. M. Sheldrick, SHELXS86, Univ. of Göttingen, Germany,
1986.
Z. Otwinowski, W. Minor, Methods in Enzymology, vol. 276
(Eds.: C. W. Carter, R. M. Sweet Jr), 1997, Academic Press,
New York, pp. 307.
P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout, D. J.
Watkin, J. Appl. Crystallogr. 2003, 36, 1487–1487.
I. J. Bruno, J. C. Cole, P. R. Edgington, M. K. Kessler, C. F.
Macrae, P. McCabe, J. Pearson, R. Taylor, Acta Crystallogr.,
Sect. B 2002, 58, 389–397.
F. H. Allen, Acta Crystallogr., Sect. B 2002, 58, 380–388.
Received: March 20, 2008
[52]
[53]
[54]
[55]
[56]
[57]
[58]
[28] H. E. Gottlieb, V. Kotlyar, A. Nudelman, J. Org. Chem. 1997,
62, 7512–7515.
[29] Rodd’s Chemistry of Carbon Compounds, 2nd ed. (Ed.: S.
Coffey), Elsevier, Amsterdam, 1965, vol. I, part B, pp. 68–71.
[59]
Published Online: May 30, 2008
Eur. J. Org. Chem. 2008, 3569–3581
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3581