Soft luminescent materials based on Ag(I) coordination complexes

Article abstract of DOI:10.1080/15421406.2013.763335

The synthesis and characterization of a new liquid-crystalline columnar 2,2′-bipyridine silver complex containing the 2,2′-bipyridine and benzoate as ancillary ligand, both functionalized with long alkyl chains was performed, along with a full photophysical investigation both in solution and in different condensed states. Furthermore, in order to get more insights about their solid-state architectures, structural studies have been performed on a model complex. The new complexes are luminescence in solution, but on passing to the condensed states, this luminescence is quenched or red-shifted, as a function of different soft or hard organizations inducted by varying the temperature. Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental resources: crystallographic data and table for Bz1. CCDC reference number 922531.

Full text of DOI:10.1080/15421406.2013.763335

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Soft Luminescent Materials Based on
Ag(I) Coordination Complexes
Elisabeta I. Szerb a , Daniela Pucci a , Alessandra Crispini a &
Massimo La Deda a
a Centro di Eccellenza CEMIF.CAL-LASCAMM, CR-INSTM Unità della
Calabria, Dipartimento di Chimica e Tecnologie Chimiche – CTC,
Università della , Calabria , Italy
Published online: 02 Apr 2013.
To cite this article: Elisabeta I. Szerb , Daniela Pucci , Alessandra Crispini & Massimo La Deda (2013)
Soft Luminescent Materials Based on Ag(I) Coordination Complexes, Molecular Crystals and Liquid
Crystals, 573:1, 34-45, DOI: 10.1080/15421406.2013.763335
To link to this article: http://dx.doi.org/10.1080/15421406.2013.763335
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Mol. Cryst. Liq. Cryst., Vol. 573: pp. 34–45, 2013
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2013.763335
Soft Luminescent Materials Based on Ag(I)
Coordination Complexes
ELISABETA I. SZERB,∗ DANIELA PUCCI, ALESSANDRA
CRISPINI, AND MASSIMO LA DEDA
Centro di Eccellenza CEMIF.CAL-LASCAMM, CR-INSTM Unita` della
Calabria, Dipartimento di Chimica e Tecnologie Chimiche – CTC,
Universita` della Calabria, Italy
The synthesis and characterization of a new liquid-crystalline columnar 2,2ꢀ-bipyridine
silver complex containing the 2,2ꢀ-bipyridine and benzoate as ancillary ligand, both
functionalized with long alkyl chains was performed, along with a full photophysical
investigation both in solution and in different condensed states. Furthermore, in order
to get more insights about their solid-state architectures, structural studies have been
performed on a model complex. The new complexes are luminescence in solution, but
on passing to the condensed states, this luminescence is quenched or red-shifted, as a
function of different “soft” or “hard” organizations inducted by varying the temperature.
Supplemental materials are available for this article. Go to the publisher’s online edition
of Molecular Crystals and Liquid Crystals to view the free supplemental resources:
crystallographic data and table for Bz1. CCDC reference number 922531.
Keywords Coordination chemistry; Luminescence; Metallomesogens
Introduction
Coordination complexes based on Ag(I) cations and N-donor pyridyl ligands have proved
to give rise to a wide variety of molecular architectures and supramolecular arrangements,
controlled simply by changing the nature of the molecular building blocks or reaction
parameters (solvent, reagents ratio, and temperature) [1].
In this context, we are interested in the application of the inorganic chemistry engi-
neering in the field of liquid crystalline Ag(I) materials, to generate soft architectures with
tunable photophysical properties. It is worthy to mention that mesomorphic Ag(I) deriva-
tives are promising multifunctional materials for applications in electro-optical devices,
and therefore, the understanding of the relationship between structure and properties is
essential for a fine tuning of the photophysical properties of the final material [2]. Struc-
tural studies conducted on model molecules demonstrate how important the nature of the
different molecular parts is in the generation of specific intermolecular interactions in the
three-dimensional space [3]. In the area of liquid-crystalline Ag(I) materials, we reported
several works regarding supramolecular assemblies constructed by using as building blocks
∗Address correspondence to Elisabeta I. Szerb, Centro di Eccellenza CEMIF.CAL-LASCAMM,
CR-INSTM Unita` della Calabria, Dipartimento di Dipartimento di Chimica e Tecnologie Chimiche
– CTC, Universita` della Calabria, Via P. Bucci Cubo 14C Italy. Fax: +39 0984 492066. E-mail:
e.szerb@unical.it
[106]/34

Soft Luminescent Materials
[107]/35
differently functionalized oligopyridines and counterions with variable coordination ca-
pacities [4–8]. The change in the supramolecular structure and the inherent tuning of the
photophysical properties both in solution and in condensed state of the final materials was
followed by changing the nature of the N,N’-donor ligand (from 2,2ꢀ-bipyridines to 2,2ꢀ-
biquinolines differently functionalized with two or six long alkyl chains), the nature of coun-
terions (perchlorate – ClO4−, trifluoromethanesulphonate – OTF−, and dodecylsulphate –
DOS) and reaction conditions. Consequently, lamello-columnar and columnar mesophases
of different symmetries were obtained and, in some cases, it was possible to investigate the
photophysical properties of the Ag(I) complexes within the soft or condensed phases.
In particular, we followed two strategies. First, the coordination of the Ag(I) centre
with two chelating 2,2ꢀ-bipyridine-based ligands differently functionalized with several long
alkyl chains yielded disc-shaped ionic complexes of general formula [(bpy-R)2Ag]X pre-
sented in Chart 1. These complexes furthermore self-assembly into columnar mesophases,
whose symmetry depended on the type of the counterion used. In particular, the more
voluminous DOS counterion forced the arrangement into a more constrained rectangular
geometry [4]. The introduction of a chiral centre in the molecular structure, yielded room
temperature mesomorphism and blue emission in the liquid-crystalline state of the final
complexes [6].
Furthermore, the lowering of the stoichiometric ratio between the Ag(I) metal centre
and the N,N’-donor ligand to 1:1, resulted in a self-assembly of the complexes in different
supramolecular architectures, principally tuned by the coordinating ability of the counterion
(Chart 2) [7,8].
In particular, using the moderately coordinating OTf counterion, a chiral supramolecu-
lar polymeric network arrangement in the solid state [7] or blue emission in the mesophase
[8], were observed (Chart 2).
These stimulating results prompted us to investigate functional benzoates as more
versatile building blocks in the construction of supramolecular Ag(I) assemblies. Indeed,
1: R = COOC16H33
Colh 59 - 71°C
Emission at r.t. in solid phase: λmax = 350 nm
2: R = CONHC10H21
Colr 139 - 179°C
3: R = CONHC18H37
Colh 118 - 299°C
X = OSO2CF3
*
4: R = COOC10H19
Colh r.t. - 91°C
(Otf)
Emission at r.t. in mesophase: λmax = 460 nm
OC16H33
+
R
R
H2COOC
OC16H33
5: R =
Colh 69 - 97°C
R
N
N
N
N
N
OC16H33
-X
+
AgX
2
Ag
N
Emission at r.t. in solid phase: λmax = 367 nm
R
R
R
6: R = COOC16H33
Colr 81 - 85°C
[(bpy-R)2Ag](Otf)
Emission at r.t. in solid phase: λmax = 365 nm
*
7: R = COOC10H19
Colh r.t. - 57°C
X = OSO3C12H25
Emission at r.t. in mesophase: λmax = 486 nm
(DOS)
OC16H33
H2COOC
OC16H33
8: R =
Colr 77 - 90°C
OC16H33
Emission at r.t. in solid phase: λmax = 367 nm
Chart 1. Chemical structure, mesomorphism, and photophysical properties in solid and mesophase
for ionic Ag(I) complexes containing two bipyridine-based ligands [4–6].

36/[108]
E. I. Szerb et al.
9: R = COOC16H33 Lcol 96 - 146°C
[(bpy-R)Ag(Otf)]
[(bq-R)Ag(Otf)]
10: R = COOC16H33 Lcol 147 - 167°C
Emission at r.t. in solid phase: λmax = 560 nm
R
R
Emission in mesophase: λmax = 560 nm
N
N
X
OC16H33
OC16H33
Ag
(Otf)
Ag
[(bq-R)Ag](Otf)
H COOC
2
11: R =
Colobp
73 - 102°C
R
N
OC16H33
N
Emission at r.t. in solid phase: λmax = 490 nm
Emission in mesophase: λmax = 460 nm
R
2+
R
(ClO4)
N
R
R
Ag
R
R
N
N
N
-
(ClO4)2
12: R = COOC16H33
Lcol 80 - 106°C
[(bpy-R)3Ag2](ClO4)2
N
Ag
N
R
Chart 2. Chemical structure, mesomorphism, and photophysical properties in solid and mesophase
for Ag(I) complexes with 1:1 or 3:2 ligand to metal ratio [7,8].
benzoates may act as counterions [9,10] as well as monodentate [11] or bidentate [12]
ancillary ligands, yielding thus very different stereochemical arrangements. Furthermore,
the easiness of functionalization with long alkyl chains into the benzoate ions, affords
a simple way to increase the aliphatic part in the molecular structure of the resulting
complexes [13].
Therefore, as an extension of our work regarding soft materials based on Ag(I) com-
plexes, herein, we report on the synthesis and characterization of a new liquid-crystalline
complex, Bz12, containing a 2,2ꢀ-bipyridine functionalized with several long alkyl chains
as main ligand and the 3,4,5-dodecyloxybenzoate as complementary ligand. As main ligand
we used the promesogenic ligand 4,4ꢀ-bis[3,4,5-(tris-dodecyloxy)benzoyloxymethyl]-2,2ꢀ-
bipyridine, (bpy-H12) that resulted from our previous studies less versatile in the coordi-
nation towards Ag(I) ion, yielding always tetracoordinated ionic complexes [4]. In these
complexes, the columnar mesophase symmetries observed, depended on the type of the
counterion used. The introduction of a noninnocent ligand like the functionalized benzoate,
can induce the formation of a different coordination environment around the Ag(I) metal
centre, therefore, changing drastically the molecular structure and influence the photophys-
ical properties of the system. Furthermore, in order to clarify the structure of the final
complexes, we prepared a model complex, Bz1, using as main ligand the 4,4ꢀ-dimethoxy-
2,2ꢀ-bipyridine (bpy-C1) and 3,4,5-methyloxybenzoate as complementary ligand, on which
a structural study has been performed through single-crystal X-ray diffraction.
Results and Discussion
Synthesis and Characterization
The synthesis of the new Ag(I) complexes is presented in Scheme 1. In particular, dimeric
[13] Ag(I) alkyloxybenzoates p1 and p2, were obtained starting from the appropriate benzoic
acid derivatives [14] adapting a synthetically procedure reported in the literature [15]. The

Soft Luminescent Materials
[109]/37
5
6
R2
R1O
R1O
R1O
R1O
R1O
R1O
R1O
R1O
R1O
1
N
3
i)
iii)
COO2Ag2
COOH
COO
Ag
ii)
N
p1: R1 = OCH3
p2: R1 = OC12H25
R2
Bz1: R1 = OCH3; R2 = OCH3
OC12H25
OC12H25
OC12H25
7
O
O
Bz12: R1 = OC12H25; R2
=
Scheme 1. Synthesis and proton numbering of complexes Bz1 and Bz12: (i)NaOH, EtOH/H2O, r.t.,
2 hours; (ii) AgNO3, r.t., 2 hours; and (iii) bpy-C1 or bpy-H12, CHCl3, r.t., 16 hours.
corresponding complexes Bz1 and Bz12 were obtained by stirring for 16 hours at room
temperature (r.t.) in a vessel protected by light, a solution in chloroform of the two precursors
[16], respectively the Ag(I) benzoates (p1 or p2) and the proper bipyridinic ligands (bpy-C1
or bpy-H12) (Scheme 1).
The structural characterization and purity of the new derivatives reported herein (Bz1
1
and Bz12) were investigated by IR and H NMR spectroscopies and elemental analysis,
the data being presented in the experimental section. Furthermore, the neutral character in
CH2Cl2 solution was assessed by conductivity measurements for both complexes experi-
mental section (ESI) [8,17].
The coordination environment of the Ag(I) derivatives Bz1 and Bz12 in solution, was
examined through proton 1H NMR measurements. Both spectra showed similar chemical
shifts for the aromatic protons, respectively, protons 3, 5, and 6 from the 2,2ꢀ-bipyridine
ligand and proton 9 from benzoate. In particular, proton 3 is upfield shifted, whereas all
other aromatic protons shift at higher ppm with respect to the precursors (2,2ꢀ-bipyridine
ligand and silver benzoates, respectively). This suggests a similar structure of the two
complexes at least in solution.
IR spectra may give information in order to distinguish between the possible coor-
dination type of the benzoate ions, looking at the C–O stretching frequencies [11a]. In
particular, an increase of the antisymmetrical C–O stretching or a decrease of the sym-
metrical one may be an indication of the monodentate coordination mode. This is evident
for both complexes, Bz1 and Bz12 when compared with their precursors, p1 and p2, re-
spectively, where, as reported before, the benzoate has a bidentate coordination mode (see
Experimental Part). Indeed, the C–O antisymmetrical stretching frequency increases for
both complexes, (of 21.6 cm−1 and 67.9 cm−1 for Bz1 and Bz12, respectively), whereas the
symmetrical stretching remains more or less around the same frequency of the precursor.
Thermogravimetric analysis (TGA) measurements conducted on both complexes
showed a relatively good thermal stability, with decomposition occurring above 200◦C,
and the absence of coordination solvents in the pristine solids, confirmed also by elemental
analysis.
In the case of the model complex Bz1, single crystals suitable for X-ray diffrac-
tion analysis were grown in CH2Cl2 solution. As it is shown in Fig. 1(a), the Ag(I) ion,
three coordinated by the N,N-chelated bipyridine and the monodentated O-bonded 3,4,5-
methyloxybenzoate ligand (intramolecular distance Ag–O(4) of 2.892(5) Å), exhibits a
distorted T-shaped coordination geometry, with the N(1)-Ag-O(3) angle of 154.1(1)◦ and
the Ag-N(1) bond distances 0.12 Å shorter than the corresponding Ag-N(2) value. The

38/[110]
E. I. Szerb et al.
Figure 1. Perspective view of complex Bz1 with atomic numbering scheme (ellipsoids at the 40%
level) (a) and its packing diagram illustrating the formation of columns along the a direction between
association of dimers of molecules (b).
two pyridyl rings of the bipyridine ligand are found highly coplanar with the torsion angle
C(4)-C(5)-C(6)-C(7) of 1.6(1)◦.
The crystal packing of Bz1 is built up through the repetition of dimers of molecules
organized in a head-to-tail arrangement to each other along the a direction (Fig. 1(b)).
Within the dimer and between dimers strong ring-to-metal interactions exist, as proved by
the distances, between the centroid of the pyridine ring of one molecule and the Ag(I) ion
lying above, of 3.5 and 3.7 Å, and the angle between the centroid – Ag vector with the
normal to the aromatic plane of 22 and 28◦, respectively.
Mesomorphism
The thermal behaviour of complex Bz12 was investigated by differential scanning calorime-
try (DSC), polarizing optical microscopy (POM), and small-angle X-ray diffraction on
powder samples (PXRD).
Complex Bz12 exhibits an enantiotropic liquid-crystalline phase from almost r.t.
(36.4◦C) to 59.2◦C (Table 1). On POM, a bright blue fan-shaped texture with homeotropic
Table 1. Optical and thermal data for complex Bz12
Transitiona
T/◦C
ꢀH/kJ·mol−1
First Cycle
C–Colh
Colh–I
I–Colh
Colh–I
I–Colh
36.4
59.2
59.1
60.0
59.3
18.9
73.3
4.6
5.5
5.4
Second Cycle
aC: crystal; Colh: columnar hexagonal mesophase, I: isotropic liquid.

Soft Luminescent Materials
[111]/39
Figure 2. POM micrograph of the texture developed by complex Bz12 on cooling at 50◦C.
zones was observed on cooling (Fig. 2) suggesting a columnar hexagonal mesophase. The
DSC scan contains only in the first heating cycle two transitions, corresponding to C–Colh
transition and Colh–I, respectively. On cooling and further heating-cooling cycles only the
second transition is observed.
An overview of the transition temperatures and the corresponding detectable enthalpies
is given in Table 1.
The distinct identification of the mesophase was made by PXRD. The X-ray pattern of
complex Bz12 (Fig. 3(a)) recorded on cooling at 50◦C consists, in the small angle region,
√
√
√
of four reflections in the ratio 1 : 3 : 4 : 7 characteristic of a two-dimensional lattice
of a hexagonal columnar phase, corresponding to the indexation (hk) = (10), (11), (20),
and (21), with cell parameter a = 37.8 Å. The fluid-like nature of the phase is confirmed
by the diffuse and broad-scattering halo h centered at 4.4 Å at wide angles of the X-ray
pattern (Fig. 3).
On cooling at r.t., the hexagonal columnar arrangement is kept in a kind of glassy state
and broad reflections appear in the wide-angle region of the PXRD pattern indicating the
formation of relatively strong intracolumnar interactions (Fig. 3(b)).
Photophysical Behavior
The photophysical properties of Bz1 and Bz12 were firstly collected in diluted
dichloromethane solutions, obtaining absorption, emission, and excitation spectra. As
shown in Fig. 4, the two spectra set have nearly the same shape. In particular, the absorption
bands of Bz1 (consisting of a maximum at 258 nm followed by a shoulder at 290 nm) are
blue-shifted with respect to the corresponding bands of Bz12 (270 and 300 nm, respec-
tively). Both samples show an emission maximum centered at 350 nm. These features are
ascribed to π→π∗ transitions localized on the bipyridine rings, slightly perturbed by the
silver coordination.
Interesting results are obtained when both compounds are examined as neat samples,
placing the microcrystalline powders between two quartz windows and recording their

40/[112]
E. I. Szerb et al.
Figure 3. PXRD pattern of Colh phase of complex Bz12 (a) at 50◦C on first cooling; (b) at r.t. after
the first heating-cooling cycle.
photophysical properties varying the temperature. During these heating-cooling cycles,
Bz1 and Bz12 yielded different results.
Compound Bz1 is not luminescent at room temperature as pristine powder solid, and
this behavior is retained until the melting point (172◦C). At this end, the isotropic sample
500
400
300
200
100
0
240
280
320
360
400
440
wavelengths (nm)
Figure 4. Excitation (on the left) and emission (on the right) spectra of Bz1 (dotted line) and Bz12
(continuous line) in dichloromethane solution.

Soft Luminescent Materials
[113]/41
100
90
80
70
60
50
40
30
20
10
0
350
400
450
500
550
600
650
700
λ/nm
Figure 5. Excitation (on the left) and emission (on the right) spectra of Bz1 obtained in the condensed
state at r.t. after one heating-cooling cycle.
shows an emission with a maximum centered at 615 nm, which is kept on cooling the sample
until room temperature. Figure 5 shows the cooled sample emission and excitation spectra,
whose shape are independent on further temperature changes. The excitation spectrum
shows a band at 390 nm, absent in the spectrum recorded in solution.
By comparing these results with those obtained in solution, it can be concluded that in
the pristine solid state, complex Bz1 experiences intermolecular interactions able to quench
the luminescence showed in a diluted solution, where the photophysical properties of the
single molecule are evidenced. Most likely, in the isotropic state the contacts between the
chromophores are weakened, allowing for a recovery of the luminescence experienced as a
single molecule in the solution. The persistence of the molecular interactions in the isotropic
state accounts for the red-shifting of the excitation and emission bands with respect to the
solution spectra.
Compound Bz12 shows a more complex behavior following the thermal course. Indeed,
like compound Bz1, the microcrystalline solid state sample of Bz12 does not emit at room
temperature and becomes luminescent after the melting point (59.2◦C) is reached, showing
a maximum at 580 nm (the corresponding excitation spectrum shows a peak at 370 nm and
a shoulder at 420 nm; Fig. 6). During the cooling cycle, the emission is retained, and the
intensity increases until 40◦C. At room temperature no luminescence is detected.
It is reasonably to suppose that, like compound Bz1, strong intermolecular interac-
tions existing in the solid state of complex Bz12, quench the molecular luminescence. In
the isotropic state, the intermolecular contacts between the chromophores are reasonable
weakened, therefore again the luminescence is partially recovered. On cooling from the
isotropic state, a highly disordered liquid crystalline phase is formed (between 80◦C and
40◦C), where the absence of intermolecular interactions within the columns is proved by
the absence of indicative reflections in the wide angle region of the PXRD pattern (Fig.
3(a)).

42/[114]
E. I. Szerb et al.
100
90
80
70
60
50
40
30
20
10
0
350
400
450
500
550
600
650
λ/nm
Figure 6. Excitation (on the left) and emission (on the right) spectra of Bz12 obtained in the
mesophase at 45◦C on first cooling cycle.
At room temperature, relatively strong interactions between the chromophores, trans-
lated into relatively strong reflections observed in the wide-angle region of the X-ray
diffraction pattern of the complex Bz12 (Fig. 3(b)), could be responsible of the lumines-
cence quenching.
Conclusions
Two new Ag(I) complexes, Bz1 and Bz12, containing N,N’-bipyridine functionalized lig-
and and benzoate ions as coordinated ancillary ligand, have been synthesized and fully
characterized.
The single-crystal X-ray characterization of Bz1 has confirmed the formation of neutral
derivatives in which the Ag(I) ion is three coordinated by the N,N-chelated bipyridine and
the monodentated o-bonded three substituted benzoate ligands.
Moreover, complex Bz12, increases the family of Ag(I) luminescent liquid-crystalline
complexes, containing a suitable functionalized benzoate, able to cooperate with the main
ligand in the assembling of specific supramolecular architectures for the formation of
columnar liquid-crystalline phases. Strong intermolecular contacts between chromophores
are probably on the base of the luminescence quenching observed on passing from solution
to the solid state. Nevertheless, a partial recovering of the luminescence is obtained when
an amorphization process is induced by changing temperature. In particular, Bz12 is found
to be luminescent also in its hexagonal columnar mesophase, where highly disordered
molecular organization within the columns, help the chromophores to behave as isolate
units.

Soft Luminescent Materials
[115]/43
Experimental
Materials and methods: All commercially available starting materials were used as
received without further purification. Ligand 4,4ꢀ-dimethoxy-2,2ꢀ-bipyridine (bpy-C1)
was purchased from Sigma-Aldrich. Ligand 4,4ꢀ-bis[3,4,5-(tris-dodecyloxy)benzoyloxy
methyl]-2,2ꢀ-bipyridine (bpy-H12) was synthesized as previously reported [s1]. For the
model compound, the starting material, 3,4,5-trimethoxybenzoic acid, was purchased from
Sigma-Aldrich and used as received, whereas the 3,4,5-tridodecyloxybenzoic acid was
synthesized as previously reported [s3].
1
The H NMR spectra were recorded on a Bruker Avance AC-300 spectrometer in
[D6]DMSO, CDCl3 or CD3OD solution, using tetramethylsilane as internal standard. El-
emental analyses were performed with a Perkin Elmer 2400 microanalyzer by the Micro-
analytical Laboratory at the University of Calabria. Infrared spectra (KBr) in the range
4000-400 cm−1 were recorded on a Spectrum One FT-IR Perkin Elmer spectrometer.
Mesomorphism: The textures of the mesophases were examined with a Leica DMLP
polarizing microscope equipped with a Leica DFC280 camera and a CalCTec (Italy) heating
stage. The thermal stability was measured on a Perkin-Elmer Thermogravimetric Analyzer
Pyris 6 TGA, respectively, the transition temperatures and enthalpies were measured on a
Perkin-Elmer Pyris1 Differential Scanning Calorimeter with a heating and cooling rate of
10◦C/min. The apparatus was calibrated with indium. Three heating/cooling cycles were
performed on each sample. The powder X-Ray diffraction patterns were obtained using
a Bruker AXS General Area Detector Diffraction System (D8 Discover with GADDS)
with Cu-Kα radiation (λ = 1.54056 Å). The highly sensitive area detector was placed at a
distance of 20 cm from the sample and at an angle (2θD) of 14◦. A CalCTec (Italy) heating
stage was used to heat the samples at a rate of 5◦C/min to the appropriate temperature.
Measurements were performed by placing the samples in Lindemann capillary tubes with
an inner diameter of 0.5 mm.
Photophysical Measurements. Spectrofluorimetric grade solvents were used for the
photophysical investigations in solution, at room temperature. A Perkin-Elmer Lambda
900 spectrophotometer was employed to obtain the solution absorption spectra. The ex-
amined compounds are fairly stable in solution, as demonstrated by the constancy of their
absorption spectra over a week. Steady-state emission spectra were recorded on a HORIBA
Jobin-Yvon Fluorolog-3 FL3-211 spectrometer equipped with a 450 W xenon arc lamp,
double-grating excitation and single-grating emission monochromators (2.1 nm/mm dis-
persion; 1200 grooves/mm), and a Hamamatsu R928 photomultiplier tube. Emission and
excitation spectra were corrected for source intensity (lamp and grating) and emission spec-
tral response (detector and grating) by standard correction curves. Powder samples have
been prepared by placing the powder between two quartz plates, in such a position that the
luminescence has been measured in reflection mode, in front-face arrangement to reduce
the scattered light.
To reach the mesophase, the two quartz plates were heated in the sample compartment
of the spectrofluorimeter by means a customized hot stage realized by CaLCTec s.r.l.
(Rende, Italy).
Synthesis
Ag(I) 3,4,5-trimethyloxybenzoate (p1): To a solution of 3,4,5-trimethyloxybenzoic acid
(0.300 g, 1.414 mmol) in ethanol (25 mL) a solution of NaOH (0.057 g, 1.414 mmol) in
water (5 mL) was added dropwise. The reaction mixture was stirred for 2 hours at room
temperature, and then an equimolar quantity of AgNO3 (0.240 g, 1.414 mmol) was added.

44/[116]
E. I. Szerb et al.
After stirring for another 2 hours at r.t., the white precipitate formed was filtered out and
washed with ethanol to give the product (0.451 g, 85%) as a white solid. M.p. > 300◦C;
IR(KBr): νmax/cm−1 1565.9 cm−1 (C–O antisymm.), 1383.6 cm−1 (C–O symm.); 1H NMR:
δH (300 MHz, CDCl3) 7.22 (2H, s), 3.82 (3H, s), and 3.74 (6H, s).
Ag(I) 3,4,5-trimethyldodecyloxybenzoate (p2): To
a
solution of 3,4,5-
trimethyldodecyloxy-benzoic acid (0.300 g, 0.444 mmol) in ethanol (25 mL) a solution
of NaOH (0.015 g, 0.444 mmol) in water (5 mL) was added dropwise. The reaction mixture
was stirred for 2 hours at r.t., and then an equimolecular quantity of AgNO3 (0.075 g,
0.444 mmol) was added. After stirring for another 2 hours at room temperature, the white
precipitate formed was filtered out and washed with ethanol to give the product (0.278 g,
82%) as a white solid. M.p. = 154◦C; IR(KBr): νmax/cm−1 1519.9 cm−1 (C–O antisymm.),
1365.3 cm−1 (C–O symm.); 1H NMR: δH (300 MHz, CDCl3) 7.21 (2 H, s), 3.30 (6 H, m),
1.72 (6 H, m), 1.45–1.22 (54 H, overlapped peaks), and 0.88 (9 H, t, 3J = 6.6 Hz).
Bz1: A solution of bpy-C1 (0.100 g, 0.461 mmol) and precursor p1 (0.147 g,
0.231 mmol) in CHCl3 (50 ml) was stirred in a vessel protected by light for 16 hours
at r.t. Then the solution was filtered under celite, the solvent was concentrated and diethyl
ether was added to the solution. The precipitate formed was filtrated out and dried to give
the pure complex Bz1 as a white waxy solid (0.212 g, 86%). M.p. = 172◦C. Anal. Calc.
for C22H23AgN2O7 (535.3 g·mol−1): C, 49.36; H, 4.33; N, 5.23; Found: C, 49.40; H, 4.25;
N, 5.42; IR(KBr): νmax/cm−1 1587.5 cm−1 (C–O antisymm.), 1385.8 cm−1 (C–O symm.);
1H NMR: δH (300 MHz, CDCl3) 8.70 (2 H, d, J(H,H) = 5.9 Hz, H6), 7.49 (2 H, d, J(H,H)
=
2.3 Hz, H1), 7.45 (2 H, s, H3), 6.98 (2 H, dd, J(H,H) = 5.9 Hz, 2,3 Hz, H5), 3.97 (3 H, s,
CH3O-benzoate), 3.92 (6 H, s, CH3O-bipyridine), 3.89 (6 H, s, CH3O-benzoate); and
M
(CM = 1·10−5 mol·L−1, CH2Cl2) = 7 cm2·ꢁ−1·mol−1
.
Bz12: A solution of bpy-H12 (0.150 g, 0.098 mmol) and precursor p2 (0.076 g,
0.049 mmol) in CHCl3 (50 ml) was stirred in a vessel protected by light for 16 hours
at r.t. Then the solution was filtered under celite; the solvent was concentrated and diethyl
ether was added to the solution. The precipitate formed was filtrated out and dried to give
the pure complex Bz12 as a white waxy solid (0.184 g, 81%). Thermal behavior in Ta-
ble 1. Anal. Calc. for C141H241AgN2O15 (2312.29 g·mol−1): C, 73.24; H, 10.51; N, 1.21;
Found: C, 73.15; H, 10.29; N, 1.20; IR(KBr): νmax/cm−1 1587.8 cm−1 (C–O antisymm.),
1363.5 cm−1 (C–O symm.); 1H NMR: δH (300 MHz, CDCl3) 8.87 (2 H, d, J(H,H) = 5.1 Hz,
H6), 8.15 (2 H, s, H3), 7.54 (2 H, d, J(H,H) = 4.8 Hz, H5), 7.38 (2 H, s, H1), 7.30 (4 H, s,
H7), 5.45 (4 H, s, CH2OOC), 4.02 (18 H, m, OCH2), 1.79 (18 H, m, OCH2CH2), 1.50–1.25
(162 H, overlapped peaks, CH2), 0.88 (27 H, t, J(H,H) = 6.6 Hz, CH3); and
(CM
M
= 1·10−5 mol·L−1, CH2Cl2) = 3 cm2·ꢁ−1·mol−1. Electronic Supplementary Information
(ESI) available: crystallographic data and table for Bz1. CCDC reference number 922531.
Acknowledgement
Financial support received from the Ministero dell’Istruzione, dell’Universita` e della
Ricerca (MIUR) through the Centro di Eccellenza CEMIF.CAL (CLAB01TYEF) is grate-
fully acknowledged.
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