Macrocyclic ZnII and CuII complexes as guests of the hybrid composites based on the layered MnPS3 phase. Comparison of spectroscopic properties

Article abstract of DOI:10.1080/00958972.2014.968145

A family of macrocyclic complexes [M₂LⁿCl₂] have been synthesized and characterized (M: Cu^II or Zn^II; Lⁿ: macrocyclic ligand derived from 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde and different aliphatic diamines and o-phenylenediamine). The influence of the aromaticity of the ligand and the metal center on the spectroscopic properties of the complexes (absorption and emission) has been studied. Making use of the weak interactions between hydrated potassium ions and the layers of the K_0.4Mn_0.8PS₃ precursor, the obtained macrocyclic complexes have been intercalated in the interlamellar space by a microwave assisted cationic exchange reaction. The optical properties of the obtained hybrid materials are reported. The absorption edge, recorded by solid state reflectance spectroscopy for Cu^II and the Zn^II macrocycle-based composites, is 1.67-1.76 eV, both shifted to lower energy compared with that of the pristine MnPS₃.

Full text of DOI:10.1080/00958972.2014.968145

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Macrocyclic ZnII and CuII complexes
as guests of the hybrid composites
based on the layered MnPS3 phase.
Comparison of spectroscopic properties
Pablo Fuentealbaab, Lorenzo Serónab, Camila Sánchezab, Jorge
Manzurbc, Verónica Paredes-Garciabd, Nancy Pizarrod, Marjorie
Cepedad, Diego Venegas-Yazigibe & Evgenia Spodineab
a Facultad de Ciencias Químicas y Farmacéuticas, Universidad de
Chile, Santiago, Chile
b CEDENNA, Santiago, Chile
Click for updates
c Facultad de Ciencias Físicas y Matemáticas, Universidad de
Chile, Santiago, Chile
d Departamento de Ciencias Químicas, Universidad Andrés Bello,
Santiago, Chile
e Facultad de Química y Biología, Universidad de Santiago de
Chile, Santiago, Chile
Accepted author version posted online: 23 Sep 2014.Published
online: 17 Oct 2014.
To cite this article: Pablo Fuentealba, Lorenzo Serón, Camila Sánchez, Jorge Manzur, Verónica
Paredes-Garcia, Nancy Pizarro, Marjorie Cepeda, Diego Venegas-Yazigi & Evgenia Spodine (2014)
Macrocyclic ZnII and CuII complexes as guests of the hybrid composites based on the layered MnPS3
phase. Comparison of spectroscopic properties, Journal of Coordination Chemistry, 67:23-24,
3894-3908, DOI: 10.1080/00958972.2014.968145
To link to this article: http://dx.doi.org/10.1080/00958972.2014.968145
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Journal of Coordination Chemistry, 2014
Vol. 67, Nos. 23–24, 3894–3908, http://dx.doi.org/10.1080/00958972.2014.968145
Macrocyclic ZnII and CuII complexes as guests of the hybrid
composites based on the layered MnPS3 phase. Comparison
of spectroscopic properties
PABLO FUENTEALBA†‡, LORENZO SERÓN†‡, CAMILA SÁNCHEZ†‡,
JORGE MANZUR‡§, VERÓNICA PAREDES-GARCIA‡¶, NANCY PIZARRO¶,
MARJORIE CEPEDA¶, DIEGO VENEGAS-YAZIGI‡‖ and EVGENIA SPODINE*†‡
†Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
‡CEDENNA, Santiago, Chile
§Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
¶Departamento de Ciencias Químicas, Universidad Andrés Bello, Santiago, Chile
‖Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile
(Received 29 May 2014; accepted 29 August 2014)
A family of macrocyclic complexes [M2LnCl2] have been synthesized and characterized (M: CuII or
ZnII; Ln: macrocyclic ligand derived from 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde and dif-
ferent aliphatic diamines and o-phenylenediamine). The influence of the aromaticity of the ligand
and the metal center on the spectroscopic properties of the complexes (absorption and emission) has
been studied. Making use of the weak interactions between hydrated potassium ions and the layers
of the K0.4Mn0.8PS3 precursor, the obtained macrocyclic complexes have been intercalated in the
interlamellar space by a microwave assisted cationic exchange reaction. The optical properties of the
obtained hybrid materials are reported. The absorption edge, recorded by solid state reflectance spec-
troscopy for CuII and the ZnII macrocycle-based composites, is 1.67–1.76 eV, both shifted to lower
energy compared with that of the pristine MnPS3.
*Corresponding author. Email: espodine@uchile.cl
Dedicated to Professor Juan Costamagna.
© 2014 Taylor & Francis

Macrocyclic ZnII and CuII complexes
3895
Keywords: Macrocyclic complexes; MnPS3 phase; Intercalation; Microwave radiation; Spectroscopic
properties
1. Introduction
The study of materials with lamellar structure has generated interest due to their anisotropic
physical properties and their structural conditions for becoming hosts of a wide range of
inserted guest molecules by intercalation reactions, such as organic compounds [1], organo-
metallic compounds [2], polymers [3, 4], monovalent and trivalent cations [1, 5–7]. The
obtained hybrid materials have received attention mainly because the properties of the final
composites are different from those of the initial precursors [1, 2, 4, 8–12].
Many layered compounds, such as double hydroxides [12–14], MS2 (M = Ti, Mo, Nb, Ta)
[15–18], and metal thiophosphates (MPS3) [19, 20], have been reported. Among these, an
important family of layered hosts is the transition metal MPS3, where the MnII phase is one
of the most interesting phases [21, 22]. The electric and magnetic properties for the MnPS3
phase indicate a semiconductor character with low values of conductivity and a material
presenting an antiferromagnetic exchange phenomenon [8]. From an optical point of view
the MnPS3 phase is almost a non-absorbing material. Furthermore, the intercalated
K
0.4Mn0.8PS3 phase is a useful precursor, due to the existence of weak host-guest interac-
tions between the interlamellar hydrated potassium ions and the layers of MnPS3, which
allow the exchange of these with bulky species, such as coordination compounds [22, 23].
The synthesis and structural characterization of macrocyclic complexes started forty years
ago, as reported by Zanello et al. [24]; these complexes present different properties such as
optical, magnetic, and antimicrobial activity that can modify the initial properties of MnPS3
[25–28]. For example, most of the phenoxido-bridged macrocyclic dinuclear CuII com-
plexes are known to present a strong antiferromagnetic interaction between the metal cen-
ters bridged by the phenoxido group [29]. By intercalating these macrocyclic complex
species into the MnPS3 phase, exhibiting the above-mentioned spectroscopic properties, it
is possible to generate new composites with different physical properties due to the interac-
tion of the host and guest moieties.
In the present work, a family of dinuclear ZnII and CuII macrocyclic complexes have
been synthesized. These complexes were intercalated in the MnPS3 phase, by means of the
K
0.4Mn0.8PS3 precursor, through a microwave assisted reaction. The layered materials have
been characterized in order to investigate the influence of the ZnII or CuII guest complex on
the optical properties of the MnPS3 layered host.
2. Experimental
2.1. Characterization
Copper and zinc analyses for the macrocyclic complexes were carried out on AAnalyst 700
Perkin Elmer equipment using an acetylene/air flame. The analyses of C, N, and H were
done on a Thermo Fisher Flash 2000 Elemental Analyzer. FT-IR spectra were registered,
using KBr pellets, on Bruker Vector 22 equipment. UV–vis absorption spectra were
recorded on an Agilent 8453 Diode-Array spectrophotometer. The molar absorptivity, є,
was calculated from 10-7 to 10−4 M concentrations. Emission and excitation spectra were
recorded on a Horiba Jobin-Yvon FluoroMax-4 spectrofluorometer with excitation wave-
length 350 nm. The luminescent quantum yield was calculated using sulfate quinine in a

3896
P. Fuentealba et al.
0.1 M solution of H2SO4 (Φquinine = 0.546 [30]). The absorbance for the complexes and the
reference compound were matched at 350 nm (values lower than 0.05 were employed). At
this absorbance, the CuII complexes do not emit, while the ZnII complexes present only one
emission band.
X-ray powder diffraction was performed using a Bruker D-8 Advance diffractometer with
a Cu Kα1 radiation in the 5° < 2θ < 60° range. Scanning electron microscopy (SEM) was
done using a Jeol Scanning Microscope (JSM-5410), with an Oxford Link Isis energy dis-
persive X-ray detector (EDXS). Diffuse reflectance spectra of solid samples were recorded
on Perkin Elmer equipment (Lamba 1050 UV/vis/NIR Spectrometer).
2.2. Syntheses
All the solvents were distilled before use, while amines and inorganic salts were used as
received. Pure elements were used to synthesize the host MnPS3 phase using the synthetic
method reported by Ruiz-León et al. [7]. The potassium precursor was synthesized by con-
tinuous stirring of the pristine phase in a 2 M potassium chloride solution for 24 h at room
temperature [22]. The macrocyclic complexes were intercalated by a microwave assisted
reaction (12 min. 800 W), as described by Spodine et al. [23]. The microwave apparatus for
synthesis was a Millestone, model LAVIS 1000 Multi-Quant, with a frequency of
2.459 GHz.
The synthesis of all the complexes was based on 2-hydroxy-5-methyl-1,3-benzenedicarb-
aldehyde, which was synthesized by oxidation of 2,6-bis(hydroxymethyl)-p-cresol, by the
procedure described by Papadopoulao et al. [31].
2.3. Synthesis of 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde
2,6-Bis(hydroxymethyl)-p-cresol (13.8 g) was dissolved in 1 L of chloroform under contin-
uous stirring at room temperature. Manganese dioxide (120 g) was added slowly to the
reaction mixture under continuous stirring, and the final suspension was refluxed for 6 h.
The obtained mixture was cooled to room temperature and filtered. The yellow solution
was evaporated under vacuum and the obtained yellow solid was purified by sublimation.
The product was characterized by FTIR spectroscopy (KBr pellets): 3028–2924 (νC–H aro-
matic ring), 2872 (νC–H aldehyde), 1681, 1666 (νC=O aldehyde). Anal. Calcd (C9H8O3) (%):
C, 65.85; H, 4.91. Found (%): C, 64.5; H, 5.1.
2.4. Syntheses of [2 + 1] hemicyclic ligands with aliphatic amines
The hemicyclic ligand was obtained using the corresponding aliphatic amine. In 10 mL of
2-propanol 150 mg (0.914 mM) of 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde was
dissolved with continuous stirring at room temperature. The appropriate aliphatic diamine
(ethylenediamine (27 μL) (I), 1,3-diaminopropane (34 μL) (II), 1,3-diamino-2-propanol
(37 mg) (III)) was added dropwise (90% of the corresponding molar relation, 0.411 mM),
thus avoiding formation of the macrocyclic species, and left to react for one hour. The solu-
tions were cooled to 5 °C, and the yellow–orange solids that precipitated were washed with
2-propanol and dried under vacuum (scheme 1).
(I) Yield; 100 mg, 62%. Anal. Calcd (C20H20N2O4): C 68.17; H, 5.72; N, 7.95. Found
for (I) (%): C, 67.8; H, 6.2; N, 7.9.

Macrocyclic ZnII and CuII complexes
3897
CH3
N
OH
OH
O
O
R = -CH2CH2- (I)
R
-CH2-CH2-CH2- (II)
-CH2-CH(OH)-CH2- (III)
N
CH3
Scheme 1. Hemicyclic ligands.
(II) Yield; 80 mg, 47%. Anal. Calcd (C21H22N2O4): C 68.84; H, 6.05; N, 7.65. Found
for (II) (%): C, 69.0; H, 6.3; N, 7.7.
(III) Yield; 80 mg, 45%. Anal. Calcd (C21H22N2O5): C 65.96; H, 5.80; N, 7.33. Found
for (III) (%): C, 65.1; H, 6.0; N, 7.3.
The obtained FTIR spectra (KBr pellets) have the same pattern for all the hemicyclic
ligands: 3030–2850 (νC–H aromatic ring and aliphatic chain from the amine), 1666 (νC=O
aldehyde), 1640 (νC=N Schiff base), 1565 (νC=C aromatic ring).
2.5. Syntheses of the macrocyclic complexes
2.5.1. Homonuclear symmetric complexes. Symmetric homonuclear macrocyclic
complexes were synthesized by a template reaction, similar to the procedure described by
Paredes–García et al. [32]. 2-Hydroxy-5-methyl-1,3-benzenedicarbaldehyde (150 mg, 0.914
mM) was refluxed for 1.5 h with 125 mg of ZnCl2 (or CuCl2, 156 mg, 0.914 mM) in 2-pro-
panol (25 mL) under a nitrogen atmosphere. Then 0.914 mM of the corresponding diamine
(ethylenediamine (1,5) (55 mg), 1,3-diaminepropane (2,6) (68 mg), 1,3-diamine-2-propanol
CH3
R = -CH2CH2- (I)
-CH2-CH2-CH2- (II)
-CH2-CH(OH)-CH2- (III)
o-C6H4
N
N
M = Zn (1)
M = Zn (2)
M = Zn (3)
M = Zn (4)
M = Cu (5)
M = Cu (6)
M = Cu (7)
M = Cu (8)
O
O
N
N
M
M
R
R
CH3
Scheme 2. Symmetric macrocyclic complexes (chloride ligands have been omitted for clarity).

3898
P. Fuentealba et al.
(3,7) (82 mg) or o-phenylenediamine (4,8) (100 mg)) dissolved in 10 mL 2-propanol were
added, and the reacting mixture was refluxed for 30 min, and left to react further at room
temperature with stirring for 24 h. The obtained solids were washed with 2-propanol and
methanol, and dried in vacuum (scheme 2).
[Zn2L1Cl2], C22H22Cl2N4O2Zn2 (1). Yield; 220 g, 84%. Anal. Calcd (%): C, 45.86; H,
3.85; N, 9.72; Zn, 22.70. Found (%): C, 45.1; H, 3.9; N, 9.8; Zn, 22.2.
[Zn2L2Cl2], C24H26Cl2N4O2Zn2 (2). Yield; 225 mg, 81%. Anal. Calcd (%): C, 47.71; H,
4.34; N, 9.27; Zn, 21.70. Found (%): C, 47.9; H, 4.4; N, 9.2; Zn, 21.0.
[Zn2L3Cl2], C24H26Cl2N4O4Zn2 (3). Yield; 240 mg, 83%. Anal. Calcd (%): C, 45.31; H,
4.12; N, 8.81; Zn, 20.56. Found (%): C, 45.4; H, 4.1; N, 8.7; Zn, 20.8.
[Zn2L4Cl2], C30H22Cl2N4O2Zn2 (4). Yield; 230 mg, 75%. Anal. Calcd (%): C, 53.60; H,
3.30; N, 8.33; Zn, 19.46. Found (%): C, 53.3; H, 3.4; N, 8.4; Zn, 19.3.
[Cu2L1Cl2 ](H2O)2, C22H26Cl2N4O4Cu2 (5). Yield; 220 mg, 79%. Anal. Calcd (%): C,
43.43; H, 4.31; N, 9.21; Cu, 20.89. Found (%): C, 43.3; H, 4.3; N, 9.3; Cu, 20.8.
[Cu2L2Cl2](H2O)2, C24H30Cl2N4O4Cu2 (6). Yield; 225 mg, 78%. Anal. Calcd (%): C,
45.29; H, 4.75; N, 8.80; Cu, 19.97. Found (%): C, 45.1; H, 4.8; N, 8.9; Cu, 20.3.
[Cu2L3Cl2](H2O)2, C24H30Cl2N4O6Cu2 (7). Yield; 230 mg, 76%. Anal. Calcd (%): C,
43.12; H, 4.52; N, 8.38; Cu, 19.01. Found (%): C, 43.3; H, 4.6; N, 8.2; Cu, 18.9.
[Cu2L4Cl2](H2O)2, C30H26Cl2N4O4Cu2 (8). Yield; 220 mg, 68%. Anal. Calcd (%): C,
51.14, H, 3.72; N, 7.95; Cu, 18.04. Found (%): C, 51.3; H, 3.8; N, 7.8; Cu, 18.0.
The FTIR spectra (KBr pellets) of all symmetric macrocyclic complexes show three main
vibration bands at 3030–2850 (νC–H aromatic ring and aliphatic chain from the amine);
1640 (νC=N Schiff base); 1565 cm−1 (νC=C aromatic ring). Furthermore, a band typical of
the ortho aromatic substitution is observed at 760 cm−1.
2.5.2. Homonuclear unsymmetric complexes. This family of macrocyclic species was
obtained through a stepwise reaction by a procedure similar to that reported by Sreedaran
et al. [33]. The procedure can be summarized as follows: to 0.273 mmoles of the corre-
sponding hemicyclic ligand (I, 96 mg; II, 100 mg; or III, 104 mg) suspended in 2-propanol,
triethylamine (80 μL) was added to deprotonate the ligand. A solution of the metallic salt
(0.545 mM, 75 mg ZnCl2, or 93 mg of CuCl2∙2H2O) in 10 mL of 2-propanol was added
dropwise and the mixture was reacted for one hour. Finally, o-phenylenediamine (0.273 mM,
30 mg) was added and the reaction mixture was stirred at room temperature for 24 h. The
solid was filtered off, washed with 2-propanol and methanol, and dried (scheme 3).
[Zn2L5Cl2], C26H22Cl2N4O2Zn2 (9). Yield; 145 mg, 85%. Anal. Calcd (%): C, 50.03; H,
3.55; N, 8.98; Zn, 20.95. Found (%): C, 50.2; H, 3.6; N, 8.8; Zn, 20.5.
[Zn2L6Cl2], C27H24Cl2N4O2Zn2 (10). Yield; 128 mg, 74%. Anal. Calcd (%): C, 50.81;
H, 3.79; N, 8.78; Zn, 20.49. Found (%): C, 50.9; H, 3.7; N, 8.9; Zn, 20.6.
[Zn2L7Cl2], C27H24Cl2N4O3Zn2 (11). Yield; 133 mg, 75%. Anal. Calcd (%): C, 49.57; H,
3.70; N, 8.56; Zn, 19.99. Found (%): C, 49.4; H, 3.7; N, 8.6; Zn, 19.8.
[Cu2L5Cl2 ](H2O)2, C26H26Cl2N4O4Cu2 (12). Yield; 156 mg, 87%. Anal. Calcd (%): C,
47.57; H, 2.99; N, 8.53; Cu, 19.36. Found (%): C, 47.9; H, 4.1; N, 8.4; Cu, 18.9.
[Cu2L6Cl2 ](H2O)2, C27H28Cl2N4O4Cu2 (13). Yield; 114 mg, 62%. Anal. Calcd (%): C,
48.36; H, 4.21; N, 8.36; Cu, 18.95. Found (%): C, 48.2; H, 4.2; N, 8.4; Cu, 19.0.
[Cu2L7Cl2 ](H2O)2, C27H28Cl2N4O5Cu2 (14). Yield; 137 mg, 74%. Anal. Calcd (%): C,
47.24; H, 4.11; N, 8.16; Cu, 18.51. Found (%): C, 46.7; H, 4.0; N, 8.0; Cu, 18.4.

Macrocyclic ZnII and CuII complexes
3899
CH3
R = -CH2CH2-
-CH2-CH2-CH2-
-CH2-CH(OH)-CH2-
M = Zn (9)
M = Cu (12)
M = Zn (10) M = Cu (13)
M = Zn (11) M = Cu (14)
N
N
O
N
N
M
M
R
O
CH3
Scheme 3. Unsymmetric macrocyclic complexes (chloride ligands have been omitted for clarity).
As for the unsymmetric macrocyclic complexes described above, the FTIR spectra for
the unsymmetric macrocyclic complexes show a similar pattern: 3030–2850 cm−1 (νC–H),
1640 cm−1 (νC=N), 1565 cm−1 (νC=C). In addition, the band typical of the ortho aromatic
substitution is observed at 760 cm−1.
2.6. Synthesis of the pristine phase, MnPS3, and the potassium precursor K0.4Mn0.8PS3
Pure MnPS3 phase was synthesized using the ceramic method, as described in the literature
[7]. High purity elements (Mn, P, S) were mixed in a 1 : 1 : 3 molar ratio and reacted in an
evacuated quartz tube at 750 °C for seven days. Then, the reactor was slowly cooled and a
green polycrystalline phase of MnII was obtained.
The potassium precursor was synthesized by stirring for 24 h at room temperature, a sus-
pension of the solid phase MnPS3, with an aqueous 2 M KCl solution [22]. The obtained
light green potassium precursor was characterized by SEM-EDX giving a K0.4Mn0.8PS3
stoichiometry.
2.7. Microwave assisted exchange reaction of the interlamellar potassium ions by the
macrocyclic complexes
The potassium precursor, K0.4Mn0.8PS3 (150 mg), was suspended in 15 mL of a concentrated
methanolic solution of 0.16 mmoles of the corresponding macrocyclic complex. The suspen-
sion was irradiated with microwave radiation (800 W) for 12 min. The solid was filtered,
washed with ethanol, followed by DMF, until the solvent became colorless. A representative
series of complexes was intercalated: symmetric homonuclear CuII complexes derived from
the aliphatic amines ethylenediamine and 1,3-diamino-2-propanol, [Cu2L1] and [Cu2L3]; un-
symmetric homonuclear CuII derived from the aliphatic amines ethylenediamine and 1,3-dia-
mino-2-propanol and o-phenylenediamine [Cu2L5] and [Cu2L7]; symmetric homonuclear
ZnII derived from ethylenediamine [Zn2L1] and from o-phenylenediamine [Zn2L4]. The
obtained composites were characterized by SEM-EDX giving the following stoichiometries:
[Cu2L1]0.07K0.26Mn0.8PS3 (a), [Cu2L3]0.07K0.26Mn0.8PS3 (b), [Cu2L5]0.08K0.24Mn0.8PS3 (c),
and [Cu2L7]0.09K0.22Mn0.8PS3 (d), for the CuII complexes, and [Zn2L1]0.07K0.26Mn0.8PS3 (e),
[Zn2L4]0.12K0.16Mn0.8PS3 (f) for the ZnII complexes.

3900
P. Fuentealba et al.
3. Results and discussion
3.1. Synthesis and structure
The obtained ZnII and CuII macrocyclic complexes were all characterized by elemental
analyses and infrared spectra. The first coordination sphere of the CuII centers of the
synthesized complexes was assumed to be five-coordinate, as determined by X-ray diffrac-
tion for 5, 6, 7, and 8 in previous work [34–39]. The structure of 7 shows that the chlorides
occupy axial positions in the first coordination sphere and are trans to each other [37],
while the other reported complexes have oxygen donors in the axial positions, provided by
water, methanol, DMF, nitrate or perchlorate [34–36, 38, 39]. Furthermore, analyses for the
synthesized complexes are consistent with two solvation waters in the proposed structure of
all the CuII complexes. In contrast, the elemental analyses for the ZnII complexes are in
agreement with an anhydrous structure, as was previously reported by Korupoju et al. for a
similar macrocyclic complex [40]. These authors describe the first coordination sphere of
the ZnII chloride complex as being five-coordinate with a square base pyramidal geometry.
Thus, both CuII and ZnII series of complexes are assumed as having five-coordinate metal
centers.
The combination of these molecular guests with layered hosts, such as MnPS3, gives
new functional materials. This can be accomplished by ion exchange reaction, which allows
the organized assembly of molecules into the interlamellar space of layered frameworks.
However, this synthetic procedure is time consuming, since the guest substitution is limited
by diffusion processes, and the charge and size of the intercalated molecules. Therefore, the
possibility to use microwave assisted intercalation has resulted in a promising synthetic
alternative to obtain new hybrid materials, such as the composites reported in this work
[23]. The microwave assisted synthesis permitted isolation and characterization of the
following homonuclear-based composites: [Cu2L1]0.07K0.26 Mn0.8PS3 (a), [Cu2L3]0.08K0.26
Mn0.8PS3 (b), [Cu2L5]0.08K0.24 Mn0.8PS3 (c), [Cu2L7]0.09K0.22Mn0.8PS3 (d);
[Zn2L1]0.07K0.26Mn0.8PS3 (e), [Zn2L4]0.12K0.16Mn0.8PS3 (f). These composites can also be
obtained by the more classical ion exchange procedure, which involves stirring the suspen-
sion of K0.4Mn0.8PS3 in a saturated solution of the corresponding macrocyclic complex for
several weeks at room temperature. The materials resulting from the microwave assisted
intercalation exhibit similar optical properties as the composites prepared by the classical
ion-exchange route. Therefore, only the optical properties of the composites obtained by the
microwave assisted method will be discussed in this work.
3.2. Spectroscopic properties of the macrocyclic complexes
All complex solutions were prepared in DMSO/H2O mixtures (ratio 1 : 2). The absorption
spectra were recorded from 300 to 800 nm, while the emission spectra were between
370 and 650 nm [27]. Both absorption and emission spectra will be analyzed and
discussed.
The absorption and emission spectra for all complexes under study are shown in figures 1
and 2. Tables 1 and 2 summarize the results of the spectroscopic studies of homonuclear sym-
metric and unsymmetric complexes, respectively.
The absorption maxima did not change their position in the studied concentration range,
so it was possible to infer that only one species was present in solution.

Macrocyclic ZnII and CuII complexes
3901
0.6
0.4
0.2
0.0
0.6
(a)
(b)
0.4
0.2
0.0
300
400
500
600
700
800
300
400
500
600
700
800
(nm)
(nm)
(d)
(c)
400
500
600
400
500
600
(nm)
(nm)
Figure 1. Absorption (a) and emission (c) spectra of the symmetric ZnII complexes: (1) ■ black; (2) ○ red; (3) ♦
blue; (4) ▴ green. Absorption (b) and emission (d) spectra of the symmetric CuII complexes: (5) ■ black; (6) ○
red; (7) ♦ blue; (8) ▴ green (see http://dx.doi.org/10.1080/00958972.2014.968145 for color version).
3.2.1. Absorption spectra of ZnII macrocyclic complexes. ZnII symmetric complexes
1, 2, and 3 with macrocyclic ligands derived from aliphatic amines have only one
absorption in the 370–400 nm range, while 4 with the macrocyclic ligand derived from
o-phenylenediamine has two absorptions at 370 and 425 nm [figure 1(a)]. The absorption
maxima are at 400 (є = 1.0∙104 M−1 cm−1) for 1, 370 (є = 1.1∙104 M−1 cm−1) for
2, 370 (є = 1.3∙104 M−1 cm−1) for 3, and 370 and 425 nm (є = 1.5∙104 and
8.8∙103 M−1 cm−1) for 4. The higher energy band is associated with the n → π*
ligand-centered transition and the 425 nm maximum is assigned to a metal to ligand charge
transfer band (MLCT) [41].
The unsymmetric ZnII complex (9) shows a band at 370 nm (є = 6.9∙103 M−1 cm−1),
with a small shoulder at 395 nm. The band at 370 nm is associated with a ligand-centered
n − π* transition similar to the one of the symmetric complex, while the shoulder at 395 nm
is ascribed to a MLCT absorption related to the o- phenylenediamine moiety of the ligand
[32]. For the unsymmetric complexes (10 and 11) ligand-centered transition bands are
observed at 350 nm (є = 8.6 × 103 (10); є = 1.1 × 104 M−1 cm−1 (11)) and the MLCT
absorptions at 385 nm (є = 1.2 × 104 (10)) and 395 nm (є = 1.6 × 104 M−1 cm−1 (11)).
Due to the lower aromaticity of the unsymmetric ligands, the MLCT band is blue-shifted,
as compared with the symmetric 4 derived from o-phenylenediamine. In addition, as shown

3902
P. Fuentealba et al.
0.6
0.6
0.4
0.2
0.0
(a)
(b)
0.4
0.2
0.0
300
400
500
600
700
800
300
400
500
600
700
800
(nm)
(nm)
(c)
(d)
400
500
600
400
500
600
(nm)
(nm)
Figure 2. Absorption (a) and emission (c) spectra of the unsymmetric ZnII complexes: (9) □ black; (10) ○ red;
(11) ▴ green. Absorption (b) and emission (d) spectra of the unsymmetric CuII complexes: (12) □ black; (13) ○
red; (14) ▴ green (see http://dx.doi.org/10.1080/00958972.2014.968145 for color version).
Table 1. Spectroscopic data for the symmetric macrocyclic complexes.
Complex
N°
λAbs (nm)
є (M−1 cm−1
)
λem (nm)
ϕ (%)
[Zn2L1]2+
[Zn2L2]2+
[Zn2L3]2+
[Zn2L4]2+
(1)
(2)
(3)
(4)
400
370
370
370
425
1.0 × 104
1.1 × 104
1.3 × 104
1.5 × 104
8.8 × 103
487
427
427
500
3.0
5.6
6.9
14.3
[Cu2L1]2+
[Cu2L2]2+
[Cu2L3]2+
[Cu2L4]2+
(5)
(6)
(7)
(8)
360
370
550–700
360
370
550–700
360
370
550–700
355
418
550–700
5.7 × 103
sh
487
427
427
500
–
–
–
–
~102
7.3 × 103
sh
~102
6.6 × 103
sh
~102
1.2 × 104
1.1 × 104
~102

Macrocyclic ZnII and CuII complexes
3903
Table 2. Spectroscopic data for the unsymmetric macrocyclic complexes.
Complex
[Zn2L5]2+
N°
λ
Abs (nm)
є (M−1 cm−1
)
λ
em (nm)
ϕ (%)
(9)
370
395
350
385
350
395
6.9 × 103
sh
493
5.5
[Zn2L6]2+
[Zn2L7]2+
(10)
(11)
8.6 × 103
1.2 × 104
1.1 × 104
1.6 × 104
496
496
7.8
8.4
[Cu2L5]2+
[Cu2L6]2+
[Cu2L7]2+
(12)
(13)
(14)
370
400
550–700
350
390
550–700
352
sh
493
496
496
–
–
–
1.1 × 104
~102
1.3 × 104
1.1 × 104
~102
1.2 × 104
1.1 × 104
~102
385
550–700
for the symmetric complexes, the intra-ligand bands in the complexes with 1,3-diaminepro-
pane and 1,3-diamine-2-propanol (2 and 3) are blue-shifted compared to the macrocyclic
ligand derived from ethylenediamine (1). Therefore, two maxima in the spectra of 10 and
11 can be distinguished.
3.2.2. Absorption spectra of CuII macrocyclic complexes. The CuII complexes derived
from macrocyclic ligands with aliphatic amines (5, 6, and 7) present an unsymmetric band
at 360 nm (є = 5.7 × 103 (5); є = 7.3 × 103 (6); є = 6.6 × 103 M−1 cm−1 (7)), with a shoulder
at 370–380 nm. The asymmetry of this absorption is assigned to the superposition of the
phenolate to copper(II) charge transfer band that can be expected for phenoxido-CuII com-
plexes in this same region [42]. Complex 8 has a band at 355 nm (є = 1.2 × 104 M−1 cm−1)
and a second one at 418 nm (є = 1.1 × 104 M−1 cm−1). The band at higher energy is
assigned to a ligand-centered n → π* transition, as in the ZnII complexes [figure 1(b)].
The unsymmetric complexes with CuII centers show spectra with two absorptions, as
observed for spectra of the ZnII ones (figure 2). Complex 12, derived from ethylenediamine
and o-phenylenediamine, shows an unsymmetric band at 400 nm (є = 1.1 × 104 M−1 cm−1)
with a shoulder at 370 nm. These two absorption bands are assigned to the same transitions
as in the ZnII complex (9), derived from the same ligand. For the unsymmetric 13 and 14,
with 1,3-diaminepropane and 1,3-diamine-2-propanol moieties, a higher energy band at 350
and 352 nm (є = 1.3 × 104 (13); є = 1.2 × 104 M−1 cm−1 (14)) is observed, respectively. A
second band is found at 390 and 385 nm (є = 1.1 × 104 M−1 cm−1 (13); є = 1.1 ×
104 M−1 cm−1 (14)) for both complexes. These two absorptions have the same origin as in
12, where the ligand-centered n − π* transition is shifted to higher energies in comparison
to complexes with ethylenediamine.
All spectra of the CuII complexes are characterized by a weak band at 550–700 nm
(є = ~ 102 M−1 cm−1) ascribed to d–d transition of the copper ion.
3.2.3. Emission spectra of ZnII macrocyclic complexes. Figure 1(c) shows the corre-
sponding spectra of the symmetric ZnII complexes, which emit at 487 (1), 427 (2), 427 (3),

3904
P. Fuentealba et al.
and 500 nm (4). The calculated percentages of the quantum yield were 3.0 (1), 5.6 (2), 6.9
(3), and 14.3% (4).
As can be observed, the emission band for the complex with the aromatic ligand (4) is
red-shifted compared to symmetric complexes with macrocyclic ligands based on
non-aromatic amines (1, 2, and 3). Macrocyclic 1 showed the lowest quantum yield, being
doubled when the aliphatic chain increased by one carbon in 2 and 3 (table 1). The
presence of the OH substituent in the aliphatic amine of the macrocyclic ligand of 3 did not
affect the emission wavelength of the corresponding complex, as compared with 2, while
the quantum yield showed a slight increase. Complex 4, whose ligand is completely
delocalized, shows the highest quantum yield.
Figure 2(c) shows the corresponding emission spectra of the unsymmetric ZnII com-
plexes. Complex 9 whose ligand is derived from ethylenediamine and o-phenylenediamine
shows an emission band at 493 nm (ϕ, 5.5%). A comparison of the spectra indicates that
the unsymmetric 9 emits at a wavelength between the emissions of 1 and 4, corresponding
to the symmetric macrocyclic complexes derived from ethylenediamine and o-phenylenedi-
amine, respectively (figure 3). Similar behavior is observed for the unsymmetric macrocy-
clic 10 (ϕ, 7.8%) and 11 (ϕ, 8.4%); they emit between the emission wavelengths of the
corresponding symmetric complex with the aliphatic amine (2) and the symmetric complex
with o-phenylenediamine (4).
3.2.4. Emission spectra of CuII macrocyclic complexes. The CuII macrocyclic complexes
did not emit under the conditions for the ZnII complexes. However, when the concentration
of the complexes was increased and the equipment setup was modified, the emission band
could be detected. Quantum yields could not be measured for these complexes. Symmetric
and unsymmetric CuII species have the same emission behavior as the ZnII symmetric
(figure 1) and unsymmetric (figure 2) complexes. Among the CuII macrocyclic complexes,
the complex with the aromatic amine (8) presents the most intense band, as compared with
the symmetric complexes with aliphatic amines and the unsymmetric complexes.
Considering that both ZnII and CuII complexes with the same macrocyclic ligand emit at
the same wavelength, as shown in tables 1 and 2, it is possible to infer that the emission
proceeds via an intraligand process. Similar behavior has been reported for RuII and ReI
(4)
(9)
(1)
400
500
600
(nm)
Figure 3. Comparison of the emission spectra of the symmetric ZnII complexes with ethylenediamine (1) (○ red),
o-phenylenediamine (4) (▴ green), with that of the unsymmetric ZnII complex derived from ethylenediamine and
o-phenylenediamine (9) (■ black) (see http://dx.doi.org/10.1080/00958972.2014.968145 for color version).

Macrocyclic ZnII and CuII complexes
3905
complexes [43, 44]. Excitation spectra of the complexes show the same behavior as the
absorption spectra, proving that the ligand is responsible for the emission.
3.3. Optical properties of the lamellar composites
The energy gap for MnPS3 was calculated from the solid state reflectance spectrum; a value
of 2.5 eV was obtained (figure 4). However, the previously reported energy gap for this
same layered phase by Kamata et al., using photoelectron measurements, was 3.0 eV [45].
To explain the nature of this energy gap, the electronic structure of the thiophosphates was
calculated in the eighties by Khumalo and Hughes [46]. The calculations showed that the
valence band is constituted by the 3pxpy and 3s orbitals of the P–S bond, and the 3pz orbital
from the P–P bond, of P2S6 anion. The metal t2g and eg localized orbitals were obtained at
higher energies as compared with the valence band. The conduction band at higher energy
corresponds to the antibonding 3pz of the P–P bond and sulfur [46]. According to Grasso,
the main absorption band at 2.5 eV is from the valence band formed by the 3pxpy and 3s
orbitals of the P–S bond to the atomic orbitals of the manganese ion [47–49].
As shown in table 3, all composites have spectra with energy gaps lower than the pristine
MnPS3 phase (2.5 eV). This can be explained by accepting that during the intercalation pro-
cess the complexes lose their axial ligands and enter the interlamellar space as square planar
cationic species [28]. This can be inferred from the interlamellar distance of 9.9 Å given by
the powder diffraction data (figure 5) and the calculated distances for the macrocyclic spe-
cies (height, ~14 Å; width, ~13 Å) (scheme 4). However, inside the interlamellar space the
complexes are parallel to the layers and the metal centers interact with the protruding sul-
furs, thus restoring their initial pyramidal square base geometry. In this way, the interaction
of the metal centers and the ligands of the complexes may be assumed to be maximum with
the inorganic network.
The optical data obtained from the reflectance spectra indicate that those composites with
aliphatic amines still produce the shift of the energy gap, indicating that the shift in
the energy value is not only due to delocalization in the macrocyclic ligand derived from
the aromatic diamine (table 3). Thus, the importance of the interaction of the ligand with
20
10
0
3
1
2
E (eV)
Figure 4. Diffuse reflectance spectra of composites [Cu2L1]0.07K0.26Mn0.8PS3 (a) (○ red) and
[Zn2L1]0.07K0.26Mn0.8PS3 (e) (♦ blue) (see http://dx.doi.org/10.1080/00958972.2014.968145 for color version).

3906
P. Fuentealba et al.
(001)
2 (°) d (Å)
MnPS3
13.6
6.5
9.3
K
0.4Mn0.8PS3 9.5
Composites
8.9 9.9-10.0
10
20
30
40
50
60
2
Figure 5. Diffractograms of the pristine phase MnPS3 (black), the potassium precursor K0.4Mn0.8PS3 (red), and a
representative final composite [Cu2L1]0.07K0.26Mn0.8PS3 (blue) (see http://dx.doi.org/10.1080/00958972.2014.
968145 for color version).
Scheme 4. Schematic representation of the intercalated complexes showing the main dimensions.
Table 3. Energy gap (eV) for the composites, derived from the intercalation of
different macrocyclic complexes in MnPS3.
Composite
Energy gap (eV)
Energy gap (nm)
[Cu2L1]0.07K0.26Mn0.8PS3 (a)
[Cu2L3]0.07K0.26Mn0.8PS3 (b)
[Cu2L5]0.08K0.24Mn0.8PS3 (c)
[Cu2L7]0.09K0.22Mn0.8PS3 (d)
[Zn2L1]0.07K0.26Mn0.8PS3 (e)
[Zn2L4]0.12K0.16Mn0.8PS3 (f)
[Zn2L4]0.05K0.30Mn0.8PS3] (3)*
[Zn2L4]0.10K0.20Mn0.8PS3] (2)*
1.71
1.73
1.69
1.71
1.67
1.76
1.85
1.80
725
717
733
725
742
704
670
688
*Ref. [28].

Macrocyclic ZnII and CuII complexes
3907
the P–S of the P2S6 anions is still to be considered. However, the fact that the nature of the
metal center does produce some small differences in the values of the energy gap of the
composites can be considered as evidence that the interaction of the sulfur of the P2S6
anions with the metal centers of the intercalated complexes (ZnII, CuII) also influences the
obtained values of the absorption edge. Since the optical properties of composites of the
same stoichiometry have to be compared [50], it is possible to give as an example
[Cu2L1]0.07K0.26Mn0.8PS3 (a) and [Zn2L1]0.07K0.26Mn0.8PS3 (e), with Eg = 1.71 eV and
Eg = 1.67 eV, respectively (figure 4). The above-mentioned observations indicate that the
intercalated complexes have to be considered as a whole in their interaction with the
protruding sulfurs of the lamellae, influencing the optical properties of the composites.
4. Conclusion
The spectroscopic properties of symmetric and unsymmetric macrocyclic ZnII and CuII
complexes suggest the importance of the nature of both the ligand and the metal center, on
the absorption and emission behavior.
Due to the lower aromaticity of the unsymmetric ligands, the MLCT band is blue-shifted
in spectra of the corresponding complexes, as compared with the symmetric complexes
derived from o-phenylenediamine. For symmetric species, the intra-ligand bands in the
spectra of the complexes with 1,3-diaminepropane and 1,3-diamine-2-propanol are blue-
shifted as compared with spectra of the corresponding complexes with the macrocycle
derived from ethylenediamine.
The emission band for the symmetric complexes with the aromatic ligand, derived from
o-phenylenediamine, is red-shifted compared to those complexes which are based on macro-
cyclic ligands with ethylenediamine, 1,3-diaminopropane, and 1,3-diamino-2-propanol. The
presence of the ligand derived from o-phenylenediamine enhances the emission of the com-
plexes; the ZnII complex (4) has the highest quantum yield, as compared with 1, 2, and 3.
The unsymmetric macrocyclic ZnII and CuII complexes emit between the emission wave-
length of the corresponding symmetric complex with the aliphatic amine and the symmetric
complex with o-phenylenediamine.
All composites have spectra with energy gaps lower than the pristine MnPS3 phase
(2.5 eV). Thus, the interaction of the intercalated complex in the interlamellar space
influences the optical properties of the composites by decreasing the absorption edge of the
corresponding spectra.
Acknowledgements
The authors thank FONDECYT project 1120001 and the LIA-MIF 836 international collab-
oration project (CNRS/CONICYT) for financial support. PFC acknowledges CONICYT
doctoral grant and thesis support grant (21110612).
References
[1] I. Lagadic, P.G. Lacroix, R. Clément. Chem. Mater., 9, 2004 (1997).
[2] X. Zhang, H. Zhou, X. Su, X. Chen, C. Yang, J. Qin, M. Inokuchi. J. Alloys Compd., 432, 247 (2007).

3908
P. Fuentealba et al.
[3] D. Zhang, J. Qin, K. Yakushi, Y. Nakazawa, K. Ichimura. Mater. Sci. Eng., A, 286, 183 (2000).
[4] A. Murugan. Electrochim. Acta, 50, 4627 (2005).
[5] L. Silipigni, G. Di Marco, G. Salvato, V. Grasso. Appl. Surf. Sci., 252, 1998 (2005).
[6] R. Clement, A. Leaustic, K. Marney, A.H. Francis. J. Lumin., 60–61, 355 (1994).
[7] D. Ruiz-León, V. Manrıquez, J. Kasaneva, R.E. Avila. Mater. Res. Bull., 37, 981 (2002).
́
[8] X. Zhang, X. Su, X. Chen, J. Qin, M. Inokuchi. Microporous Mesoporous Mater., 108, 95 (2008).
[9] B.M. Choudary, S. Madhi, N.S. Chowdari, M.L. Kantam, B. Sreedhar. J. Am. Chem. Soc., 124, 14127 (2002).
[10] Y.V. Kuzminskii, B.M. Voronin, N.N. Redin. J. Power Sources, 55, 133 (1995).
[11] P.G. Lacroix, R. Clement, K. Nakatani, J. Zyss. Science, 263, 558 (1994).
[12] G. Abellán, F. Busolo, E. Coronado, C. Martí-Gastaldo, A. Ribera. J. Phys. Chem. C, 116, 15756 (2012).
[13] E. Coronado, C. Martí-Gastaldo, E. Navarro-Moratalla, A. Ribera, J.R. Galán-Mascarós. J. Mater. Chem., 20,
9476 (2010).
[14] E. Coronado, J.R. Galán-Mascarós, C. Martí-Gastaldo, A. Ribera. Chem. Mater., 18, 6112 (2006).
[15] F.R. Gamble, F. DiSalvo, R. Klemm, T. Geballe. Science, 168, 568 (1970).
[16] E. Coronado, C. Martí-Gastaldo, E. Navarro-Moratalla, E. Burzurí, A. Camón, F. Luis. Adv. Mater., 23, 5021
(2011).
[17] Y. Wu, H. Li, L. Ji, Y. Ye, J. Chen, H. Zhou. Surf. Coat. Technol., 236, 438 (2013).
[18] C.N.R. Rao, H.S.S. Ramakrishna Matte, U. Maitra. Angew. Chem. Int. Ed., 52, 13162 (2013).
[19] Q. Liu, W. Zhou, Ch Gao, T. Hu, X. Zhao. Chem. Phys. Lett., 477, 388 (2009).
[20] N. Ismail, M. Madian, A.A. El-Meligi. J. Alloys Compd., 588, 573 (2014).
[21] A.A. El-Meligi, A.M. Al-Saie, H. Al-Buflasa, M. Bououdina. J. Alloys Compd., 488, 284 (2009).
[22] S. Floquet, S. Salunke, M.L. Boillot, R. Clément, F. Varret, K. Boukheddaden, E. Rivière. Chem. Mater., 14,
4164 (2002).
[23] E. Spodine, P. Valencia-Gálvez, P. Fuentealba, J. Manzur, D. Ruiz, D. Venegas-Yazigi, V. Paredes-García,
R. Cardoso-Gil, W. Schnelle, R. Kniep. J. Solid State Chem., 184, 1129 (2011).
[24] P. Zanello, S. Tamburini, P.A. Vigato, G.A. Mazzocchin. Coord. Chem. Rev., 77, 165 (1987).
[25] X. Zhang, H. Zhou, X. Su, X. Chen, Ch Yang, J. Qin, M. Inokuchi. J. Alloys Compd., 432, 247 (2007).
[26] H. Ōkawa, H. Furutachi, D.E. Fenton. Coord. Chem. Rev., 174, 51 (1998).
[27] M. Mukhopadhyay, D. Banerjee, S. Mukherjee. J. Phys. Chem. A, 110, 12743 (2006).
[28] E. Spodine, P. Valencia-Gálvez, J. Manzur, V. Paredes-García, N. Pizarro, K. Bernot, D. Venegas-Yazigi.
Polyhedron, 44, 187 (2012).
[29] D. Venegas-Yazigi, D. Aravena, E. Spodine, E. Ruiz, S. Alvarez. Coord. Chem. Rev., 254, 2086 (2010).
[30] G.A. Crosby, J.N. Demas. J. Phys. Chem., 75, 991 (1971).
[31] E.P. Papadopoulos, A. Jarrar, C.H. Issidorides. J. Org. Chem., 31, 615 (1966).
[32] V. Paredes-García, D. Venegas-Yazigi, A. Cabrera, P. Valencia, M. Arriagada, D. Ruiz-León, N. Pizarro,
A. Zanocco, E. Spodine. Polyhedron, 28, 2325 (2009).
[33] S. Sreedaran, K. Bharathi, A. Rahiman, K. Rajesh, G. Nirmala, L. Jagadish, V. Kaviyarasan, V. Narayanan.
Polyhedron, 27, 1867 (2008).
[34] S.K. Dutta, U. Flörke, S. Mohanta, K. Nag. Inorg. Chem., 37, 5029 (1998).
[35] L.K. Thompson, S.K. Mandal, S.S. Tandon, J.N. Bridson, M.K. Park. Inorg. Chem., 35, 3117 (1996).
[36] S.S. Tandon, L.K. Thompson, J.N. Bridson, V. McKee, A.J. Downard. Inorg. Chem., 31, 4635 (1992).
[37] D. Venegas-Yazigi, S. Cortés, V. Paredes-García, O. Peña, A. Ibañez, R. Baggio, E. Spodine. Polyhedron, 25,
2072 (2006).
[38] E. Spodine, Y. Moreno, M.T. Garland, O. Pena, R. Baggio. Inorg. Chim Acta, 309, 57 (2000).
[39] K. Brychcy, K. Dräger, K.-J. Jens, M. Tilset, U. Behrens. Chem. Ber., 127, 465 (1994).
[40] S.R. Korupoju, N. Mangayarkarasi, S. Ameerunisha, E.J. Valente, P.S. Zacharias. J. Chem. Soc., Dalton
Trans., 2845 (2000).
[41] D.N. Kumar, B.S. Garg. Spectrochim. Acta, Part A, 64, 141 (2006).
[42] ThM Rajendiran, R. Kannappan, R. Mahalakshmy, J. Rajeswari, R. Venkatesan, P. Rao. Transition Met.
Chem., 28, 447 (2003).
[43] A.P. Zipp, L. Sacksteder, J. Streich, A. Cook, J.N. Demas, B.A. DeGraff. Inorg. Chem., 32, 5629 (1993).
[44] R.H. Schmehl, I.V. Rubtsov, T.A. Grusenmeyer, Y. Yue, J. Pham. Abstr. Pap. Am. Chem. Soc., 245 (2013).
[45] A. Kamata, K. Noguchi, H. Tezuka, T. Kashiwakura, Y. Ohno, Sh. Nakai. Phys. Soc. Jpn., 66, 401 (1997).
[46] F.S. Khumalo, H.P. Hughes. Phys. Rev. B, 23, 5375 (1981).
[47] V. Grasso, S. Santangelo, M. Piacentini. Solid State Ionics, 20, 9 (1986).
[48] V. Grasso, F. Neri, L. Silipigni. Il Nuovo Cimento, 13, 633 (1991).
[49] V. Grasso, F. Neri, S. Santangelo, L. Silipigni, M. Piacentini. J. Phys. Condens. Matter, 1, 3337 (1989).
[50] P. Valencia, J. Manzur, A.M. Garcia, V. Paredes-Garcia, R. Cardoso-Gil, W. Schnelle, R. Kniep, P. Fuentealba,
D. Venegas-Yazigi, E. Spodine. J. Chil. Chem. Soc., 58, 1952 (2013).