H-bonded adducts of [2,4,6-{(C10H21O)3C6H2NH}3C3N3] with [LnM{PPh2(C6H4CO2H)}] displaying columnar mesophases at room temperature

Article abstract of DOI:10.1021/ic501039n

Displacement of a labile ligand from appropriate precursor complexes by 2- or 4-PPh₂C₆H₄COOH yields neutral gold(I) and gold(III) [AuX_n(PPh₂C₆H₄COOH)] (n = 1, X = Cl; n = 3, X = C₆F₅), cationic gold(I) [Au(PPh₂C₆H₄COOH)₂]-(CF₃SO₃), and neutral chromium(0) [Cr(CO)₅(PPh₂C₆H₄COOH)] metallo-organic acids. [AuCl(4-PPh₂C₆H₄COOH)], [Au(C₆F₅)₃(4-PPh₂C₆H₄COOH)], and [Cr(CO)₅(2-PPh₂C₆H₄COOH)] have dimeric structures with typical carboxylic H-bond bridges, whereas [Au(C₆F₅)₃(2-PPh₂C₆H₄COOH)] gives a monomeric species with the carboxylic acid H bonded to cocrystallized solvent molecules. All gold-containing acids are emissive at 77 K in the range 404-520 nm and some of them also at 298 K with emission maxima from 441 to 485 nm. Reaction of these acid metal complexes with the triazine mesogen 2,4,6-{(C₁₀H₂₁O)₃C₆H₂NH}₃C₃N₃ affords some new hydrogen-bonded gold(I) and chromium(0) supramolecular adducts, but the related gold(III) complexes do not form adducts. The 4-diphenylphosphinobenzoic adducts display a columnar hexagonal mesophase (Col_hex) at room temperature, with a random one-dimensional stacking of the pseudo-discoid triazine-metallo-organic adducts into columns, where the metallo-phosphinoacid fragments act as the fourth branch of the trifold triazine core. The 2-diphenylphosphinobenzoic mixtures do not display mesophases, as they appear in the X-ray studies as mixtures of the triazine and the metallo-phosphinoacid complex. The aggregates are luminescent at 77 K, with emission maxima in the range 419-455 nm. (Chemical Equation Presented).

Full text of DOI:10.1021/ic501039n

Article
pubs.acs.org/IC
H-bonded adducts of [2,4,6-{(C10H21O)3C6H2NH}3C3N3] with
[LnM{PPh2(C6H4CO2H)}] displaying Columnar Mesophases at Room
Temperature
Ana B. Miguel-Coello,† Manuel Bardají,*,† Silverio Coco,*,† Bertrand Donnio,‡,§ Benoît Heinrich,‡
and Pablo Espinet*,†
†IU CINQUIMA/Química Inorgan
‡Institut de Physique et Chimie des Mater
Loess, BP 43, 67034 Strasbourg Cedex 2, France
́
ica, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid, Spain
iaux de Strasbourg (IPCMS), UMR 7504 (CNRS−Universite de Strasbourg), 23 rue du
́
́
§Complex Assemblies of Soft Matter Laboratory (COMPASS), UMI 3254 (CNRS−SOLVAY−University of Pennsylvania), CRTB,
350 George Patterson Boulevard, Bristol, Pennsylvania 19007, United States
S
* Supporting Information
ABSTRACT: Displacement of a labile ligand from appropriate
precursor complexes by 2- or 4-PPh2C6H4COOH yields neutral
gold(I) and gold(III) [AuXn(PPh2C6H4COOH)] (n = 1, X = Cl; n
= 3, X = C6F5), cationic gold(I) [Au(PPh2C6H4COOH)2]-
( C F 3 S O 3 ) , a n d n e u t r a l c h r o m i u m ( 0 ) [ C r -
(CO)5(PPh2C6H4COOH)] metallo−organic acids. [AuCl(4-
PPh2C6H4COOH)], [Au(C6F5)3(4-PPh2C6H4COOH)], and [Cr-
(CO)5(2-PPh2C6H4COOH)] have dimeric structures with typical
carboxylic H-bond bridges, whereas [Au(C6F5)3(2-
PPh2C6H4COOH)] gives a monomeric species with the carboxylic acid H bonded to cocrystallized solvent molecules. All
gold-containing acids are emissive at 77 K in the range 404−520 nm and some of them also at 298 K with emission maxima from
441 to 485 nm. Reaction of these acid metal complexes with the triazine mesogen 2,4,6-{(C10H21O)3C6H2NH}3C3N3 affords
some new hydrogen-bonded gold(I) and chromium(0) supramolecular adducts, but the related gold(III) complexes do not form
adducts. The 4-diphenylphosphinobenzoic adducts display a columnar hexagonal mesophase (Colhex) at room temperature, with
a random one-dimensional stacking of the pseudo-discoid triazine−metallo−organic adducts into columns, where the metallo−
phosphinoacid fragments act as the fourth branch of the trifold triazine core. The 2-diphenylphosphinobenzoic mixtures do not
display mesophases, as they appear in the X-ray studies as mixtures of the triazine and the metallo−phosphinoacid complex. The
aggregates are luminescent at 77 K, with emission maxima in the range 419−455 nm.
alkoxy chains are appropriate bricks to form H-bonded discotic
adducts with carboxylic acids and self-organize into liquid
crystalline columnar mesophases.12 We recently extended this
concept by integrating metal complexes containing carboxylic
acid functions and reported new types of supramolecular
metallomesogens, derived from 1:1 association of a triazine and
a 4-isocyanobenzoic acid complex of chromium(0), iron(0),
molybdenum(0), or tungsten(0). The hexagonal packing into
columnar mesophases found for the free triazine was
systematically preserved in the metal-containing supramolecular
adducts.13 In contrast, the corresponding gold(I) isocyanoben-
zoic acid complexes did not produce such adducts, likely
because the weakness of the H-bonding interactions with the
triazine and the high insolubility of the starting gold complexes
makes adduct formation thermodynamically unfavorable. Using
the same self-assembly concept, we could prepare mono- and
dinuclear thiolatobenzoic gold(I) adducts with the same
INTRODUCTION
■
Intermolecular hydrogen bonding can promote molecular self-
assembly into ordered supramolecular structures, allowing for
engineering of soft materials with specific functionalities.1 This
approach has been used successfully in the construction of
organic liquid crystalline architectures. Many examples of
simple to highly complex molecular self-assemblies have been
reported.2,3
There is interest in liquid crystalline systems forming
columnar arrangements due to their potential application in
opto-electronic devices with some advantageous properties:4
high charge-carrier mobility along the stacking axis, long-range
self-assembling, self-healing and easy processing due to fluidity,
solubility in organic solvents, and added properties such as
luminescence, conductivity, or magnetism (for metallomes-
ogens).
Metal-containing H-bonded liquid crystals are still rare,5−11
but smectic and columnar mesophases can be produced by
judicious combination of the complementary building blocks.
2,4,6-Triarylamino-1,3,5-triazines equipped by 6 or 9 peripheral
Received: May 8, 2014
Published: October 1, 2014
© 2014 American Chemical Society
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triazine mesogen and demonstrated that the corresponding
supramolecular adducts also produce a stable Colhex mesophase
at room temperature.14 In all cases, the supramolecular
triazine−metallo−organic acid complexes stack in a comple-
mentary manner: the metallic thiolatobenzoic/isocyanobenzoic
acid fragment acts as a fourth branch of the triazine core in such
a way that the steric crowding is minimized and the interface
with the aliphatic continuum is smoothened. In other words,
the metal complex moieties are somehow buried into the
dominant aliphatic environment in such a way that each
discotic unit of adduct appears externally very similar to the free
triazine, a disc with aliphatic chains. The versatility of this
approach is therefore very promising for the design and
construction of room-temperature LC mesophases from metal-
containing molecules using other carboxylic acid linkers to
connect a metallic fragment to the triazine. A potential
consequence of linking additional groups (in this case metal
complexes) to a regular discotic molecule is that the new
adduct, having a substituent protruding from the central core, is
less symmetric, and this descent of symmetry might produce
changes in the properties of the material, as studied in less
complex systems.15
sterically and were chosen on purpose to challenge the ability of
the triazine to accommodate them into a discotic unit.
RESULTS AND DISCUSSION
■
Synthesis and Characterization of Diphenylphosphi-
nobenzoic Acid Metal Complexes. Reaction of diphenyl-
phosphinobenzoic acids 1 or 2 with [AuCl(tht)], [Au-
(C6F5)3(tht)], [Au(tht)2]CF3SO3 (tht = tetrahydrothiophene),
or hexacarbonyl chromium(0) leads to the corresponding
gold(I), gold(III), or chromium(0) complexes 3−10 (Scheme
1). They are air-stable, white (3−8) or yellow (9−10) solids at
room temperature and were characterized by CHN analysis, IR,
and NMR.
Scheme 1. Synthesis and Molecular Structures of the Gold or
a
Chromium−Organic Acids 3−10
In this study we examine the utility of 2- and 4-
diphenylphosphinobenzoic acids (Figure 1). The P atom is a
Figure 1. Structures of 2- and 4-diphenylphosphinobenzoic acids and
1H NMR labels.
a
(i) [AuCl(tht)]; (ii) [Au(C6F5)3(tht)]; (iii) 1/2 [Au(tht)2]CF3SO3;
general donor for any metal fragment, and therefore, these
ligands can be used as P ligands in the synthesis of many metal
complexes. They have also been used as carboxylate ligands.16
In line with our previous works on metallo−organic supra-
molecular assemblies, the carboxylic functional group of these
diphenylphosphinobenzoic acids is suitable to produce H
bonds. For instance, 2-diphenylphosphinobenzoic acid is a
dimer with typical carboxylic acid bridges,17 and gold(I),18,19
and copper(I)20 derivatives have been reported also as H-
bonded dimers.
P-containing metallomesogens are uncommon because of the
unfavorable tetrahedral geometry imposed by the phosphorus
atom.21 However, we reported recently that the hexagonal
columnar architectures produced by aggregation of isocyano−
or thiolato−metallo−organic acids to triazines are able to
accommodate some structurally voluminous molecular groups
between the branches of the triazine, still preserving the
mesogenic behavior.13,14 Achieving the same with phosphine
groups as linkers looks more challenging, but in the present
study we will show that some liquid crystals can be made. Even
more challenging is the use of 2-diphenylphosphinobenzoic
acid that, compared with its para isomer, introduces a violent
rigid kink in the supramolecule pursued. Three different metal
moieties were chosen that provide different features to the
potential metallomesogens: linear AuI, which is expected to be
favorable; octahedral Cr(CO)5, which has been shown before
to be reasonably favorable and is a good reporter of the
bonding interaction through ν(CO) of the carbonyl groups in
IR; and square-planar AuIII, which has not been checked before.
Some of the metal-containing moieties are very demanding
(iv) [Cr(CO)6] + Me3NO.
All complexes display one ν(CO) band from the
carboxylic group in the range 1719−1685 cm−1. The chromium
compounds also show carbonyl bands at 2064, 1987, and 1932
cm−1. In their H NMR spectra, the aromatic protons of the
1
metallo−organic acids are low-field shifted compared to the
free phosphine ligand. The largest shifts are about +0.32 ppm
for H5 in the ortho ligand and +0.40 ppm for H3 for the para
ligand. The assignments given were confirmed by COSY and
1H {31P} NMR. 19F NMR spectra of compounds 5 and 6 show
two sets (1:2 ratio) of three resonances (2:1:2 ratio) due to the
C6F5 groups in the range from −120 to −122 (Fortho), −157
(Fpara), and −160.5 and −161 ppm (Fmeta). A singlet at around
−79 ppm is observed for the triflate anion of compounds 7 and
8. The singlet observed in the 31P{1H} NMR spectra is low-
field shifted by 23−65 ppm in all complexes compared to the
free phosphine ligand.
X-ray Crystal Structure Determination of Complexes
4, 5, 6, and 9. Crystalline structures of 4, 5, 6, and 9 are shown
in Figures 2 and 3 with selected bond lengths and angles in
Tables 1 and 2. Compounds 4, 6, and 9 are dimers through the
carboxylic acid groups (bond lengths and angles in Table 3),
regardless of the phosphine ortho or para substitution pattern.
As expected, the gold(I) complex 4 displays a typical linear
coordination for gold, and gold(III) derivatives 5 and 6 show
slightly distorted square-planar geometries with standard Au−
C, Au−Cl, and Au−P bond distances somewhat longer for
gold(III) than for gold(I). The shortest intermolecular Au−Au
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Au(C6F5)3 fragment embedding the acid group, which
precludes ortho dimerization but not para dimerization. All
compounds show two different C−O bond lengths in the
carboxylic functional group (Table 1). A review in the literature
reports that formation of a carboxylic acid dimer requires the
absence of competitors, and in the known X-ray structure only
about 29% of the compounds form the classic dimer, whereas
the remaining 71% form hydrogen bonds with a large variety of
other acceptors.22
Hydrogen-Bonded Triazine−[M] Adducts. Triazine (T)
was reacted with the diphenylphosphinobenzoic acid ligands 1
and 2 and the metal complexes 3−10 in THF in the
appropriate molar ratio (1:1 or 2:1, depending on the number
of acid groups in the complex), followed by slow evaporation of
the solvent (Scheme 2). This afforded pale brown (free
phosphines and gold) or green (chromium) waxy solids, which
were then studied to see whether they correspond to defined
Tn adducts or not.
The waxy materials obtained in the reactions aimed at
producing supramolecular hydrogen-bonded adducts were
examined by several techniques to find out their nature and
thermal properties. They can be classified in three groups: (1)
mixtures of the reactants, (2) hydrogen-bonded adducts, and
(3) uncertain materials. To the first group pertain the gold(III)
materials T5 and T6, which show clearly, at room temperature
in polarized optical microscopy (POM), a mixture of crystals
and liquid, indicating that the corresponding adducts have not
been formed. The rest of the compounds apparently show
mesophases at room temperature but with very different
thermal behavior. T2, T4, T8, and T10 resist some heating
maintaining the mesophase texture until the clearing point is
reached; moreover, as discussed in detail later, small-angle
powder X-ray diffraction (SAXS) studies support formation of
columnar mesophases by these hydrogen-bonded supra-
molecular adducts. Finally, whether the triazine forms or not
adducts T1, T3, T7, and T9 is doubtful, and their nature is
uncertain. Only T9 displays IR (ν(CO)) and SAXS data that
might support formation of the adduct: the A1 mode associated
mainly to the CO trans to the phosphine group diminishes
clearly in intensity and shifts +8 (for T9) or +10 cm−1 (for T10,
see Figure S1, Supporting Information). The same behavior
was observed in closely related adducts.13 The fact that T9 and
T10 give quite similar shifts seems to suggest that not only T10
but also T9 might be an adduct.23 The others (T1, T3, T7)
quickly decompose under the X-ray observation, with
formation of crystals of the starting acid, so their thermal
behavior looks uninteresting.
Figure 2. X-ray structures of dimers 4 (top) and 6 (bottom). H atoms
omitted for clarity, except for the carboxylic group. Displacement
ellipsoids are at the 25% probability level.
Overall, the results suggest that the stability of the H-bonded
adducts versus their separated components is modest and
structural variations in the components are critical. Thus,
aspects such as the size of the metallic moiety (as in T5 and T6)
or the angle made at the acid ring (2- versus 4-
diphenylphosphinobezoic) will determine whether the supra-
molecular material will be formed or not. The stability of the H-
bonded adducts is not very high even for the materials that
undoubtedly form adducts and mesophases, and diffusion-
ordered NMR spectroscopy (DOSY) shows that in CDCl3,
acetone-d6, or in THF-d8 solution T2, T4, T8, and T10 are
dissociated into their components. (see Figure S2, Supporting
Information). Thus, formation of a condensed phase is critical
for formation of adducts.
Figure 3. X-ray structure of compounds 5 (top) and 9 (bottom).
Displacement ellipsoids are at the 30% probability level. H atoms
omitted for clarity, except for the carboxylic group.
distance found for the gold(I) compound 4 is 6.4 Å, which
discards any gold−gold interaction. The chromium(0)
derivative 9 is also a H-bridged dimer that displays a slightly
distorted octahedral geometry for its two independent
molecules in the crystal. In contrast to 6, complex 5 is a
monomer with the hydrogen atom of the carboxylic group
bonded to the O atom of a cocrystallized diethyl ether
molecule. This is due to the high steric requirement of the
Thermal Behavior. The thermal behavior of the supra-
molecular adducts was investigated by differential scanning
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Table 1. Selected Bond Lengths (Angstroms) and Angles (degrees) for Complexes 3, 4, 5, and 6
a
b
3
4
4
5
6
c
Au−P
Au−Cl
2.26(1)
2.29(1)
2.232(4), 2.225(4)
2.278(4), 2.269(4)
2.2249(19)
2.271(2)
2.3808(18)
2.3768(13)
Au−C
2.070(7), 2.079(7), 2.109(7)
1.211(10)
2.068(5), 2.073(5), 2.077(5)
1.239(6)
OC
1.24(4)
1.34(3)
172.9(4)
1.24(2), 1.21(2)
1.29(2), 1.30(2)
177.5(1), 178.9(1)
1.245(9)
1.283(9)
O−C
1.329(9)
1.292(7)
P−Au−Cl
P−Au−C
C−Au−C
O−C−O
178.75(8)
176.2(2), 90.86(19), 94.0(2)
175.1(3), 87.9(3), 87.2(3)
124.5(8)
171.50(16), 91.58(14), 93.43(14)
173.45(19), 87.72(19), 87.95(19)
124.4(5)
125(4)
124(1), 125(1)
122.1(8)
a
b
c
Data from ref 19. Data from ref 18. Two independent molecules.
Table 2. Selected Bond Lengths (Angstroms) and Angles
(degrees) for Compound 9
Scheme 2. Reactions for Synthesis of Supramolecular
a
Triazine−Metalloacid Adducts, Tn
Cr(1)−P(1)
Cr(1)−C(1)
Cr(1)−C(2)
Cr(1)−C(3)
Cr(1)−C(4)
Cr(1)−C(5)
C(1)−O(1)
C(17)−O(6)
C(17)−O(7)
2.3985(9)
1.894(3)
1.861(4)
1.888(4)
1.900(3)
1.889(4)
1.128(4)
1.207(3)
1.319(3)
C(2)−Cr(1)−P(1)
C(1)−Cr(1)−C(4)
C(3)−Cr(1)−C(5)
O(1)−C(1)−Cr(1)
O(2)−C(2)−Cr(1)
O(3)−C(3)−Cr(1)
O(4)−C(4)−Cr(1)
O(5)−C(5)−Cr(1)
O(6)−C(17)−O(7)
176.65(14)
177.22(15)
176.65(17)
178.0(4)
177.7(5)
176.9(4)
176.8(3)
176.6(3)
123.2(2)
Table 3. Hydrogen Bonds Involving the Carboxylic Group
for Dimers 4, 6, and 9 and Monomer 5 (Angstroms and
a
degrees)
D−H···A
compound 4
d(D−H)
d(H···A)
d(D···A)
<(DHA)
O(1)−H(1)···O(2A)
O(1A)−H(1A)···O(2)
compound 6
0.820
0.820
1.808
1.808
2.594
2.594
160.09
160.09
O(2)−H(2)···O(1A)
O(2A)−H(2A)···O(1)
compound 9
0.820
0.820
1.814
1.814
2.631
2.631
174.97
174.97
a
H-bonding system is indicated by dashed lines. R = C10H21.
O(7)−H(7)···O(13)
O(14)−H(14A)···O(6)
compound 5
0.820
0.820
1.857
1.878
2.676
2.698
175.61
179.08
Attempted syntheses are (i) reactions with compounds 1−6, 9, and
10; (ii) the same with compounds 7 and 8.
O(2)−H(2)···O(3)
0.821
1.825
2.626
164.89
a
Symmetry transformations used to generate equivalent atoms: for
mesophase for these four adducts that is compatible with a
hexagonal columnar arrangement.
compound 4 −x + 1, −y − 1, −z; for compound 6 −x, −y + 2, −z + 1.
This thermal behavior was confirmed by DSC measurements
(Table 4, Supporting Information Figure S4). T4, T8, and T10
behave as classical enantiotropic liquid crystals. For T2 the
columnar mesophase formed during the first cooling is
maintained at room temperature over several days. With
respect to the parent triazine, the mesophase-to-isotropic liquid
transition temperature (second heating) is very similar for the
gold(I) compounds T4 (ca. +2 °C) and T8 (ca. −2 °C) and
lower for compounds T2 and the chromium(0) T10 (about −20
°C). No sign of crystallization or glass transition was detected
on cooling the samples to −20 °C, but they became much less
fluid and looked frozen, suggesting that a glassy state had been
reached. Heating well above the clearing point produced adduct
decomposition to give some microcrystals of the starting
metallo−organic acids and free triazine. Only a very small
difference in transition temperature is observed between the
triazine and the corresponding gold adducts (T4 and T8). The
same somewhat unpredicted behavior was found in our
previous study with related gold adducts.14 We explain this
calorimetry (DSC), POM, and SAXS. The triazine used in this
work,24 bearing nine diverging decyloxy chains, displays a
columnar hexagonal mesophase (Colhex) from room temper-
ature to 57 °C, when it clears reversibly to the isotropic
liquid.13,14 The diphenylphosphinobenzoic acid derivatives 1
and 2 and metallo−organic acid complexes 3−10 are not
mesomorphic. Compound 10 and the free phosphines 1 and 2
have melting points in the range 87−175 °C, but complexes 3−
9 decompose without melting in the range 162−250 °C.
Remarkably, all supramolecular adducts derived from p-
diphenylphosphinobenzoic acid are liquid crystals at room
temperature (Table 4). Fluid and homogeneous optical textures
could be observed by POM for these adducts: sandy-like
textures for the phosphine adduct T2 and for the chromium
adduct T10; ill-defined pseudo-fan-shaped texture with some
dark (homeotropic) regions for T4 and T8 (Figure 4). These
textures, although nonspecific, unambiguously confirm a
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diffraction as a function of temperature, covering from room
temperature up to the isotropic liquid. The supramolecular
aggregates show limited stability under prolonged exposure to
X-ray beam and temperature. Unambiguous assignment of the
mesophases needed, however, access to more small reflections
than visible in the diffractograms acquired with conventional
laboratory sources. These missing reflections could be acquired
on a synchrotron SAXS line. Diffractograms of the adducts
containing 4-diphenylphosphinobenzoic acid as linker, T2, T4,
T8, and T10, exhibit at least two common characteristic features:
(i) in the small-angle region, one sharp and intense reflection
along, in some cases, with additional weaker reflections, which
are indicative of long-range ordered low-dimensional lattices,
and (ii) in the large-angle region, one broad, very strong,
scattering halo spreading between 3.5 and 5.5 Å (intensity
maximum at about 4.4−4.6 Å), corresponding to the overlap of
different, undifferentiated, lateral distances between aliphatic
Table 4. Optical, Thermal, and Thermodynamic Data of
Triazine (T) and Adducts (Tn)
a
b
b
compd
transition
T/°C
ΔH /J g−1
T
Colhex → I
I → Colhex
Colhex → I
H1:57.1
C1:42.6
H2:57.5
H1:37.4
H1:51
2.0
1.1
1.2
c
T1
T2
dissociated
Cr → I
11.2
1.7
I → Colhex
Colhex → I
C1:29.5
H2:35.8
H1:40.7
H1:60.0
C1:51.6
H2:59.6
H1:40
1.7
c
T3
T4
dissociated
Colhex → I
I → Colhex
Colhex → I
1.2
1.3
1.3
c
T7
T8
dissociated
Colhex → I
I → Colhex
Colhex → I
H1:55.6
C1:29.5
H2:55.4
H1:52.5
H1:38.3
C1:18.1
H2:35.7
1.3
1.0
1.1
tails and between adduct fragments (undifferentiated hch
+
h
adduct, Table 5). In all cases, the fundamental reflection
c
T9
T10
dissociated
dominates over the higher order reflections and is due to the
strong density contrast arising from the alternation of electron-
rich columns and electron-poor fluid and continuous zones.
This contrast is further enhanced by the presence of the
metallic ion within the columns and logically reduces the higher
order reflections (therefore the need to use a highly intense
source like synchrotron).
d
Colhex → I
2.5
2.7
3.7
I → Colhex
Colhex → I
a
Cr, crystalline phase; Colhex, columnar hexagonal phase; I, isotropic
b
liquid. H1, H2, C1: first and second heating and first cooling;
temperature corresponds to the peak maximum. Dissociated means
c
that the adducts are split into their triazine and metalloacid
components upon heating above the temperature mentioned.
lamellar arrangement cannot be fully excluded.
d
The diffractogram of the phosphine adduct T2 confirms
formation of a columnar hexagonal mesophase close to 40 °C:
it displays the strong and diffuse wide-angle scattering typical of
the molten aliphatic chains and cores, along four sharp, small-
angle reflections, in the square spacing ratio 1:√3:2:√7, which
were, respectively, indexed as to the (10), (11), (20), and (21)
reflections of a hexagonal lattice with a parameter of 29.05 Å
(Figure 5 and Table 5). On further heating above the
isotropization (at T = 65 °C) the supramolecular adduct
partially dissociates into its elementary components as
evidenced by the superposition of the diffraction peaks
associated with both the free triazine in its mesophase and
the phosphine acid 2 in its crystalline state (Supporting
Information, Figure S5). The adduct reforms readily and
recrystallizes on cooling to 25 °C. It shows a reversible behavior
only when heated below the clearing transition.
A
The adduct T4 exhibits a Colhex mesophase at room
temperature in a temperature range similar to that of T.
Diffractograms (Figure 6, Supporting Information Figure S5)
recorded at 25 and 50 °C indeed show two or three sharp
small-angle reflections of the hexagonal lattice, the broad
scattering of the molten chains and cores, as well as an
additional diffuse weak halo at midangle arising likely from
short-range metal−metal interactions within the columnar
structure. Thus, connection of the [AuCl] fragment onto the
phosphine modifies and enhances the mesophase stability with
respect to the nonmetallic structurally related T2 compound.
Actually, the presence of the metallic fragment is associated
with a slight contraction of the hexagonal cell (Table 5).
Similarly, mesomorphism is maintained in the corresponding
dimeric adduct (T8): T8 is mesomorphic at room temperature,
and SAXS revealed unequivocally formation of a Colhex phase,
deduced from the presence of the two small-angle reflections
indexed as (10) and (11) of a hexagonal lattice (Figure 6,
Supporting Information Figure S5). The chromium adduct T10
shows mesomorphism, but only in a narrow range around room
temperature (Figure 6). Although the nature of the mesophase
Figure 4. Polarized optical microscopic texture observed for the free
triazine T (top left) and for adducts T4 (top, right), T8 (bottom left),
and T10 (bottom right) obtained on cooling from isotropic liquid at
room temperature. Enlarged pictures are available in Supporting
Information Figure S3.
similarity assuming that the metal complex moieties are
somehow buried into the dominant aliphatic environment of
the azine chains in such a way that each discotic unit of adduct
appears externally very similar to the triazine discs. In fact, the
mesophases of T and Tn (n = 2, 4, 8, 10) mix perfectly in
contact experiments. In contrast, addition of additional metal
complex to Tn systems does not result in mixing, providing
further evidence for specific adduct formation.
Further information and elucidation of the mesophases
observed comes from studies of small-angle powder X-ray
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a
Table 5. Geometrical Parameters of Mesophases Obtained from SAXS for the Tn Adducts
compound
T/°C
q/Å−1
d/Å
hk
I
a/Å
S/Å2
Vmol/Å3
hadduct/Å
triazine
30
40
25.83
25.15
14.54
12.57
9.51
10
10
11
20
21
10
11
10
11
10
VS(sh)
VS(sh)
W(sh)
29.82
29.05
770
731
2966
3432
3.85
4.69
T2
0.2498
0.4320
0.4997
0.6608
0.2550
0.4412
VW(sh)
W(sh)
T4
25
20
20
24.64
14.24
25.70
14.85
26.0
VS(sh)
W(sh)
28.46
29.7
30.1
701
764
780
3845
7440
3752
5.48
4.87
4.81
T8
VS (sh)
VW (sh)
VS (sh)
T10
a
T = temperature of the experiment; q = wave vector (q = 2π/d); d = d spacing; hk = Miller indices; I = reflection intensity (VS, very strong; W,
weak; VW, very weak; sh: sharp); a = hexagonal lattice parameter; S = cross-columnar section area (S = A2√3/2); Vmol = molecular volume (triazine
and adducts); hadduct = molecular height per adduct (hadduct = Vmol/SN, where N is the number of triazines per complex, e.g., N = 1 for monomers, N
= 2 for dimers).
Figure 5. SAXS diffractogram (synchrotron) of adduct T2 at ca. 40 °C,
after cooling from isotropic liquid.
cannot be unequivocally assigned on the basis of the unique
visible reflection, the analogy with the other structurally related
adducts T4 and T8, and the overall similar trends observed with
their mesomorphic behavior reasonably support assigning the
mesophase as Colhex too. A lamellar arrangement cannot be
fully excluded.
As commented above, reaction between the gold(III)-based
acids (5 or 6) and triazine does not proceed and thus does not
yield wanted adducts T5 or T6. Diffractograms of the binary
mixture T+6 (recorded at 25 °C in the pristine state, 55 °C,
and then back at 25 °C; see Supporting Information, Figure S5)
confirm nonformation of the H-bonded adduct, as evidenced
by the superposition of the distinct signals of each species,
namely, the sharp small-angle reflection of T in the Colhex (T =
25 °C), which broadens when entering in the isotropic phase
(T = 55 °C), and the numerous sharp reflections scanning the
entire diffraction angle range of 6 in the crystalline state (at all
temperatures).
For the materials containing 2-diphenylphosphinobenzoic
acid complexes the results are very different. The material
labeled T3 (T + 3) appears immediately dissociated upon
heating and on beam exposure as shown by SAXS, which
Figure 6. X-ray diffraction patterns for (a) T4 at 25 °C, (b) T8 at 20
reveals phase coexistence between solid free phosphine acid
°C, and (c) T10 at 20 °C.
and pure triazine in its mesophase (Supporting Information,
Figure S5). T7 (T + 7) and T9 (T + 9) (Supporting
Information, Figure S5) show a similar behavior.
and smoothing the columnar interface.14 The columnar phase
results from the stacking of these pseudo-discotic adducts into
columns with a slight elongation of each unit (disc) when
passing from the triazine to the adducts (see hadduct values in
Table 5). Unlike other triazine thiolatobenzoic acid systems
In summary, mesomorphism is exclusively observed for the
analogous p-[M]−phosphine adducts, suggesting that the
metallo−organic acids again play the role of a fourth arm of
the triazine, thus filling the empty regions between the arms
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reported before,14 none of the ortho systems exhibits
mesomorphic properties, probably because adducts have not
been formed. The weakness (T4) or absence of the diffuse
signal previously observed for the thiolatobenzoic acid
compounds at midangle suggests that the metallic ions are
essentially camouflaged within the branch of the triazine with
little interactions between neighbors and without protruding in
the aliphatic continuum. This difference may be ascribed to the
different geometry around the P and S atoms, respectively. The
tetrahedral geometry around the P atom of the phosphine
group will keep the metallic fragment closer to the columnar
core due to the bent angle at P, whereas the diverging phenyl
entities will be partly mixed with the aromatic parts forming the
columnar cores and the aliphatic chains, without dramatically
changing the distribution of the electronic density, as was the
case for the thiolatobenzoic acid systems having a closer to
linear geometry around the S atom. Obviously, the ortho
position does not allow for such arrangement and on the
contrary will disrupt the packing of adducts along the columns.
Photophysical Behavior. Emission and excitation spectra
of the free phosphine and metallo−organic acids were recorded
in the solid state at 77 or 298 K and in CH2Cl2 frozen solution
at 77 K. None of them emits in solution at 298 K. Emission and
excitation spectra of the supramolecular adducts (T2, T4, T8,
T10) were recorded in the solid state at 77 or 298 K. Spectra of
complex 8 and adduct T8 at 77 K are shown as representative
examples in Figure 7. Details of the excitation and emission
spectra are given in Tables S1 and S2, Supporting Information.
range in spite of the modifications in the metallic fragment and
also close to a strong emission of the free triazine, which
appears at 423 nm. Thus, the conclusion is that this emission in
the adducts is triazine centered, and the expected phosphine- or
Au−P-centered emissions in T2, T4, and T8 are of lower
intensity and overlapped by the azine-centered emission.
CONCLUSIONS
■
2-Diphenylphosphinobenzoic and 4-diphenylphosphinobenzoic
acids behave toward metal centers as typical monodentate
phosphine ligands do. Thus, gold(I) or gold(III) and
chromium(0) complexes have been prepared. The free
carboxylic functional groups of these two phosphine acids or
their metallo−organic acids produce H-bridged dimers, except
for the o-phosphine gold(III) complex because of its
voluminous substituents at gold. They can also form donor−
acceptor adducts with an appropriate triazine, providing some
p-phosphine chromium(0) and gold(I) metalloacid−triazine
supramolecular adducts that display stable hexagonal columnar
mesophases at room temperature. In the columnar stacking of
adducts the metallic fragment finds room to accommodate itself
as a wedge filling the space between the branches of the trefoil
molecular architecture of the triazine units. This is an example
showing how the triazine bearing nine lateral alkoxy chains
manages to accommodate pretty large metal−organic fragments
to produce adducts without losing the mesomorphic behavior.
However, the very unfavorable sterics of the o-phosphine
metalloacids is clearly detrimental for formation of adducts with
the triazine. It is doubtful whether they really form at all
adducts or simply their adducts do not stand moderate
temperatures close to room temperature or X-ray irradiation.
The Achilles heel of the supramolecular entities discussed here
is the weakness of the connection of the two components, the
hydrogen bond. Otherwise, it looks like that with heavily alkyl-
substituted azines pretty unfavorable geometries and fairly
voluminous groups can be accommodated into discoid
products that display mesophases at low temperature with a
columnar order.
EXPERIMENTAL SECTION
■
General procedures are as reported before.14 1H, 19F, and 31P{1H}
NMR chemical shifts are quoted relative to SiMe4 (external, 1H),
CFCl3 (external, 19F), and 85% H3PO4 (external, 31P). Emission and
excitation spectra at 298 and 77 K were measured in the solid state as
finely pulverized KBr mixtures and in deoxygenated CH2Cl2 solutions
(about 10−3 M) in quartz tubes with a Perkin-Elmer LS-55
spectrofluorimeter. For characterization of the LC mesophases, in
addition to POM and DSC, small-angle X-ray scattering techniques
were used. Variable-temperature small-angle X-ray patterns were
obtained using a linear focalized monochromatic Cu Kα1 beam (λ =
1.5405 Å) using a sealed-tube generator (900 W) equipped with a bent
quartz monochromator. In all cases, the crude powder was filled in
thin Lindemann capillaries of 1 mm diameter and 10 μm wall thickness
in air (corrections for air were made) and then heated to produce the
mesophase. An initial set of diffraction patterns was recorded with a
curved Inel CPS 120 counter gas-filled detector linked to a data
acquisition computer; periodicities up to 70 Å can be measured and
the sample temperature controlled to within 0.01 °C from 20 to 200
°C. Alternatively, patterns were also recorded on an image plate;
periodicities up to 120 Å can be measured (scanned by STORM 820
from Molecular Dynamics with 50 mm resolution). For some samples,
synchrotron patterns were obtained on the SWING synchrotron
beamline in the SAXS configuration at 12 keV energy (proposal
20120951) using a homemade transmission oven of 0.1 °C accuracy
and filling samples in 1 mm Lindemann capillaries.
Figure 7. Excitation and emission spectra of 8 (bold line) and T8
(normal line) dispersed in KBr at 77 K. Note that the plot is in
normalized intensity. This produces a deceptive appearance of
identical intensity for the two compounds.
4-Diphenylphosphinobenzoic acid and all the gold metal-
loacids are emissive at 77 K in the range 404−520 nm and
some of them also at 298 K with emission maxima from 441 to
485 nm. However, neither the chromium compounds 9 and 10
nor the free 2-diphenylphosphinobenzoic acid show any
emission in this range. Consequently, this emission is associated
with the Au−P(acid) fragment. Many gold(I) compounds are
luminescent in the visible region,25 but luminescent gold(III)
compounds are comparatively scarce.26
All adducts emit and show, at 77 K, a structureless broad
emission band in the range 419−455 nm, which appears not
only for the complexes containing the Au−P(acid) fragment
but also for the chromium adduct T10 and the free ligand
adduct T2. Moreover, this emission appears within a narrow
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Table 6. Details of Crystallographic Data and Structure Refinement for Acids 4, 5, 6, and 9
4
5·Et2O·H2O
C41H15AuF15O4P
6·CHCl3
9·0.25hexane
C25.50H15CrO7P
empirical formula
fw
C19H15AuClO2P
538.70
C38H16AuCl3F15O2P
1123.79
1084.47
293(2)
516.34
temp (K)
wavelength (Å)
cryst syst
293(2)
293(2)
293(2)
0.71073
1.54184
monoclinic
P2(1)/c
14.4299(2)
15.2743(3)
18.6396(4)
90
0.71073
1.54184
triclinic
monoclinic
P2(1)/c
18.9328(5)
7.12915(16)
16.7656(4)
90
triclinic
space group
unit cell dimens: a (Å)
b (Å)
P−1
P−1
9.8540(8)
10.4075(4)
19.2765(17)
92.533(5)
99.200(7)
93.152(5)
1945.7(2)
2
10.9729(5)
14.6769(7)
15.7818(8)
78.135(4)
74.224(4)
88.521(4)
2392.4(2)
4
c (Å)
α (deg)
β (deg)
94.008(2)
90
98.8129(19)
90
χ (deg)
vol. (Å3)
2257.40(10)
4
4059.79(14)
4
Z
density (calcd) (Mg/m3)
1.585
1.774
1.918
1.434
abs coeff (mm−1
)
6.712
8.194
4.135
4.951
F(000)
1024
2088
1080
1052
cryst habit
needle
plate
plate
plate
cryst size (mm)
0.32 × 0.05 × 0.05
2.16−28.68
0.26 × 0.13 × 0.08
3.10−75.15
0.27 × 0.19 × 0.07
2.10−28.76
0.29 × 0.19 × 0.08
2.97−75.08
Θ range for data colln
index ranges
−21 ≤ h ≤ 24, −6 ≤ k ≤ 9,
−17 ≤ h ≤ 16, −18 ≤ k ≤ 12, −12 ≤ h ≤ 9, −7 ≤ k ≤ 13,
−13 ≤ h ≤ 6, −18 ≤ k ≤ 18,
−22 ≤ l ≤ 12
−23 ≤ l ≤ 22 −23 ≤ l ≤ 22
−19 ≤ l ≤ 18
no. of reflns collected
no. of independent reflns
max and min trans.
9039
12 575 13 316
14 476
4774 [R(int) = 0.0258]
0.752 and 0.525
4774/0/205
7959 [R(int) = 0.0338]
0.601 and 0.349
8046 [R(int) = 0.0260]
0.796 and 0.450
9356 [R(int) = 0.0247]
0.720 and 0.480
9356/0/622
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
7959/0/559
8046/0/541
1.115
1.021
1.041
1.025
R1 = 0.0447, wR2 = 0.1296
R1 = 0.0686, wR2 = 0.1421
R1 = 0.0457, wR2 = 0.1198
R1 = 0.0781, wR2 = 0.1397
1.089 and−1.470
R1 = 0.0391, wR2 = 0.0869
R1 = 0.0504, wR2 = 0.0937
1.113 and−1.018
R1 = 0.0409, wR2 = 0.1070
R1 = 0.0595, wR2 = 0.1215
0.391 and−0.330
largest difference peak and 1.429 and −0.649
hole (e·Å−3
)
Synthesis of the Precursors. [AuCl(tht)],27 [Au(C6F5)3(tht)],28
[Ag(CF3SO3)(tht)],29 and [{(C10H21O)3C6H2NH}3C3N3]12 were
prepared according to literature methods. The other reagents were
obtained from commercial sources.
(CDCl3, 376 MHz): δF −119.5 (brm, 4F, Fo−Au), −121.7 (m, 2F,
Fo−Au), −157.1 (t, N = 18.0 Hz, 3F, Fp−Au), −160.7 (m, 4F, Fm−
Au), −161.2 (m, 2F, Fm−Au). 31P{1H} NMR (CDCl3, 162 MHz): δP
23.9 (s). IR (KBr): 3087 ν(O−H), 1689 ν(CO), 970, 804, 792
(C6F5) cm−1. Yield of 6: 95 mg, 73%. Mp: 240 (dec.). Anal. Calcd: C,
44.24; H, 1.51; N, 0. Found: C, 44.46; H, 1.98; N, 0. 1H NMR
(CDCl3, 400 MHz): δH 7.44−7.47 (m, 8H, Hm and Ho of Ph), 7.53
(dd, JHH = 8.5 and JHP = 11.7 Hz, 2H, H3), 7.60 (m, 2H, Hp of Ph),
8.10 (dd, JHH = 8.5 and JHP= 2.5 Hz, 2H, H2). 19F NMR (CDCl3, 376
MHz): δF −119.9 (m, 4F, Fo−Au), −121.7 (m, 2F, Fo−Au), −156.6 (t,
N = 18.8 Hz, 2F, Fp−Au), −156.7 (t, N = 19.4 Hz, 1F, Fp−Au),
−160.5 (m, 4F, Fm−Au), −160.8 (m, 2F, Fm−Au). 31P{1H} NMR
(CDCl3, 162 MHz): δP 18.1 (s). IR (KBr): 3066 ν(O−H), 1702
ν(CO), 969, 804 sh, 795 (C6F5) cm−1.
Synthesis of [AuCl(PPh2C6H4CO2H)] (ortho (3) and para (4)) and
[Au(C6F5)3(PPh2C6H4CO2H)] (ortho (5) and para (6)). To a dichloro-
methane solution (20 mL) of [AuXn(tht)] (100 mg; X = Cl, n = 1,
0.31 mmol for the synthesis of 3 and 4; X = C6F5, n = 3, 0.13 mmol for
the synthesis of 5 and 6) was added the corresponding
diphenylphosphinobenzoic acid 1 or 2 (96 mg, 0.31 mmol, for
synthesis of 3 and 4; 40 mg, 0.13 mmol, for synthesis of 5 and 6), and
the reaction was stirred at room temperature for 90 min. The solution
was then concentrated to ca. 5 mL. Addition of hexane afforded
compounds 3−6 as white solids. Compound 5 was purified from the
starting materials by crystallization from chloroform/diethyl ether
mixture. Yield of 3: 134 mg, 80%. Mp: 205 (dec.). Anal. Calcd: C,
Synthesis of [Au(PPh2C6H4CO2H)2](CF3SO3) (ortho (7) and para
(8)). To an acetone (20 mL) solution of [AuCl(tht)] (50 mg, 0.156
mmol) was added [Ag(CF3SO3)(tht)] (54 mg, 0.156 mmol), and the
mixture was stirred at room temperature for 1 h protected from the
light. Precipitate of AgCl was filtered off. The corresponding
diphenylphosphinobenzoic acid (1 or 2: 96 mg, 0.31 mmol) was
added to the solution. After stirring for 1 h, the solution was
concentrated to ca. 5 mL. Addition of hexanes afforded compounds 7
and 8 as white solids. Yield of 7: 129 mg, 86%. Mp: 219 (dec.). Anal.
1
42.36; H, 2.81; N, 0. Found: C, 42.55; H, 2.71; N, 0. H NMR (d6-
acetone, 400 MHz): δH 7.02 (ddd, JHP = 12.7 Hz, JHH = 7.79 and 1.1
Hz 1H, H3), 7.60−7.53 (m, 10H, Ho, Hp, and Hm), 7.69 (tt, JHH = 7.8
and 1.7 Hz, JHP = 1.7 Hz, 1H, H4), 7.79 (tt, JHH = 7.7 and 1.5 Hz, JHP
=
1.5 Hz, 1H, H5), 8.34 (ddd, JHH = 7.5 and 1.6 Hz, JHP = 4.4 Hz, 1H,
H6). 31P{1H} NMR (d6-acetone, 162 MHz): δP 37.49 (s). IR (KBr):
3062 ν(O−H), 1685 ν(CO) cm−1. Yield of 4: 140 mg, 84%. Mp:
200 (dec.). Anal. Calcd: C, 42.36; H, 2.81; N, 0. Found: C, 41.97; H,
1
Calcd: C, 48.86; H, 3.15; N, 0. Found: C, 48.56; H, 3.30; N, 0. H
1
2.74; N, 0. H NMR (d6-acetone, 400 MHz): δH 7.67−7.61 (m, 10H,
NMR (d6-acetone, 400 MHz): δH 7.07 (ddd, JHH = 7.9 and 1.3, JHP =
Ph), 7.73 (dd, JHH = 7.9 and JHP =12.7 Hz, 2H, H3), 8.20 (dd, JHH
=
12.9 Hz, 1H, H3), 7.62−7.55 (m, 10H, Ph), 7.71 (tt, JHH = 7.6 and 1.6,
JHP = 1.6 Hz, 1H, H4), 7.81 (tt, JHH = 7.6 and 1.5, JHP = 1.5 Hz, 1H,
H5), 8.39 (ddd, JHH = 7.9 and 1.4, JHP = 4.4 Hz, 1H, H6). 19F NMR
(d6-acetone, 376 MHz): δF −79.3 (s). 31P{1H} NMR (d6-acetone, 162
MHz): δP 47.4 (s). IR (KBr): 3058 ν(O−H), 1702 ν(CO), 1225,
636 (CF3SO3) cm−1. Yield of 8: 72 mg, 48%. Mp: 162 (dec.). Anal.
7.9 and JHP = 2.2 Hz, 2H, H2). 31P{1H} NMR (d6-acetone, 162 MHz):
δP 34.34 (s). IR (KBr): 3062 ν(O−H), 1694 ν(CO) cm−1. Yield of
5: 38 mg, 29%. Mp: 210 (dec.). Anal. Calcd: C, 44.24; H, 1.51; N, 0.
Found: C, 44.46; H, 1.98; N, 0. 1H NMR (CDCl3, 400 MHz): δH 6.97
(dd, JHH = 7.8 Hz, JHP = 13.0 Hz, 1H, H3), 7.34−7.63 (m, 12H, Ph +
H4 + H5), 8.17 (dd, JHP = 4.5 Hz, JHH = 7.2 Hz, 1H, H6). 19F NMR
1
Calcd: C, 48.86; H, 3.15; N, 0. Found: C, 48.80; H, 3.49; N, 0. H
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T8, and T10; X-ray diffraction patterns not included in the text;
excitation and emission data for all compounds and adducts.
This material is available free of charge via the Internet at
http://pubs.acs.org.
NMR (d6-acetone, 400 MHz): δH 7.61−7.73 (m, 10H, Ph), 7.78 (dd,
JHH = 8.3 Hz, JHP = 11.7 Hz, 2H, H3), 8.17 (d, JHH = 8.3 Hz, 2H, H2).
19F NMR (d6-acetone, 376 MHz): δF −79.3 (s). 31P{1H} NMR (d6-
acetone, 162 MHz): δP 45.8 (s). IR (KBr): 3058 ν(O−H), 1719
ν(CO), 1224, 637 (CF3SO3) cm−1.
Synthesis of [Cr(CO)5(PPh2C6H4CO2H)] (ortho (9) and para (10)).
To a suspension of [Cr(CO)6] (110 mg, 0.5 mmol) in 30 mL of
acetonitrile was added a solution of Me3NO (35 mg, 0.5 mmol) in 30
mL of acetonitrile. The mixture was stirred for 3 h under inert
atmosphere at room temperature. Solvent was removed under vacuum,
and the residue was dissolved in tetrahydrofuran (20 mL). Then, a
solution of the corresponding diphenylphosphinobenzoic acid (1 or 2:
153 mg, 0.5 mmol) in tetrahydrofuran (20 mL) was added dropwise.
After stirring for 2 h, the solvent was removed under vacuum. The dry
residue was washed with cold pentane and recrystallized from diethyl
ether to give 9−10 as greenish yellow solids. Yield of 9: 150 mg, 60%.
Mp: 250 (dec.). Anal. Calcd: C, 57.84; H, 3.03; N, 0. Found: C, 58.14;
H, 3.42; N, 0. 1H NMR (d6-acetone, 400 MHz): δH 7.08 (dd, JHH = 8.0
and JHP = 11.8 Hz, 1H, H3), 7.42−7.71 (m, 12H, H4 + H5 + Ph), 8.27
(br, 1H, H6). 31P{1H} NMR (d6-acetone, 162 MHz): δP 61.5 (s). IR
(KBr): 2064, 1985, 1931 ν(CO), 1696 ν(CO) cm−1. Yield of 10:
112 mg, 45%. Mp: 87. Anal. Calcd: C, 57.84; H, 3.03; N, 0. Found: C,
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: bardaji@qi.uva.es.
*E-mail: scoco@qi.uva.es.
*E-mail: espinet@qi.uva.es.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the Spanish Comision
́
Interministerial de Ciencia y
́
Tecnologia (Project CTQ2011-25137) and the Junta de
Castilla y Leon
The authors acknowledge SOLEIL for provision of synchrotron
radiation facilities, particularly Dr. Javier Perez for assistance in
́
(Project VA302U13) for financial support.
1
́
58.11; H, 3.40; N, 0. H NMR (d6-acetone, 400 MHz): δH 7.56−7.61
(m, 10H, Ph), 7.66 (dd, JHH = 8.3 and JHP = 10.1 Hz, 2H, H3), 8.17
(dd, JHH = 8.3 and JHP = 1.8 Hz, 2H, H2). 31P{1H} NMR (d6-acetone,
162 MHz): δP 56.2 (s). IR (KBr): 2064, 1989, 1934 ν(CO), 1702
ν(CO) cm−1.
using beamline SWING. B. H. and B. D. thank the CNRS for
support.
REFERENCES
■
Reactions to Prepare Hydrogen-Bonded Triazine−Metallo−
Organic Acid Adducts, Tn. Supramolecular complexes were prepared
from the pure components (triazine, T, and the various acids 1−10).
Exact stoichiometric molar amounts of the two compounds were
dissolved in dry tetrahydrofuran at room temperature, and solvent was
swept off by passing a stream of gaseous nitrogen, affording the
adducts as pale brown (free phosphines and gold) or green
(chromium) waxy solids. The corresponding Tn materials where
then studied. Only T2, T4, T8, and T10 were unambiguously identified
as hydrogen-bonded adducts.
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SingleCrystal Structure Determination of Metallo−Organic
Acids 4, 5, 6, and 9. CCDC 1000572−1000575 contain the
supplementary crystallographic data for 4, 5, 6, and 9. These data can
be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Crystals of 4 and 9
were obtained by slow diffusion of hexanes into an acetone (4) or a
dichloromethane (9) solution at −18 °C. Crystals of 5 and 6 were
obtained by slow diffusion of diethyl ether into chloroform solutions at
−18 °C. Crystals were then mounted on a glass fiber and transferred
to the SuperNova Oxford Diffraction diffractometer. Crystal data and
details of data collection and structure refinement are given in Table 6.
Cell parameters, data reduction, and absorption corrections were
carried out with the CrysAlis system software.30 The structure was
refined anisotropically on F2.31 All non-hydrogen atomic positions
were located in difference Fourier maps and refined anisotropically.
Hydrogen atoms were placed in their geometrically generated
positions. The structure of 4 contains some disordered solvent
molecules, and we were unable to properly model it. Compound 5
crystallizes with incipiently disordered diethyl ether and water
molecules. Compound 6 crystallizes with an incipiently disordered
chloroform molecule. The four molecules of Cr(0) in the unit cell of 9
crystallize with one highly disordered hexane molecule.
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ASSOCIATED CONTENT
* Supporting Information
■
S
X-ray crystallographic details in CIF format; FTIR spectra of
triazine, chromium metallo−organic acid 10, and the
corresponding aggregate with the triazine T10; DOSY spectra
of T2 and T10; polarized optical microscopic texture observed
for the free triazine T and aggregates T2, T4, T8, and T10
obtained on cooling from isotropic liquid at room temperature;
DSC thermograms for the free triazine T and aggregates T2, T4,
(5) Donnio, B.; Guillon, D.; Bruce, D. W.; Deschenaux, R.
Metallomesogens. In Comprehensive Coordination Chemistry II: From
Biology to Nanotechnology; McCleverty, J. A., Meyer, T. J., Eds.;
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