Lanthanide complexes with pyridinecarboxylic acids – Spectroscopic and thermal studies

Article abstract of DOI:10.1016/j.poly.2018.04.045

The effect of 14 lanthanides on the structure and the electronic system of isonicotinic acid was studied using IR (KBr), IR (ATR), Raman, UV–Vis, spectrofluorometric, elemental analysis and thermogravimetric (TG/DTG) methods. The influence of the lanthanides ions on the electronic charge distribution of the ligand is discussed. The nephelauxetic parameters and the degree of covalency in the lanthanide–ligand bonds were established. Moreover, the molecular structures of the lanthanide complexes with isonicotinic, nicotinic, picolinic and benzoic acids were compared, with a particular emphasis on the changes within the aromatic ring of metal complexes.

Full text of DOI:10.1016/j.poly.2018.04.045

Accepted Manuscript
Lanthanide complexes with pyridinecarboxylic acids - spectroscopic and ther-
mal studies
Grzegorz Świderski, Monika Kalinowska, Agnieszka.Z. Wilczewska, Julita
Malejko, Włodzimierz Lewandowski
PII:
S0277-5387(18)30245-6
https://doi.org/10.1016/j.poly.2018.04.045
POLY 13154
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
5 March 2018
28 April 2018
Please cite this article as: G. Świderski, M. Kalinowska, Agnieszka.Z. Wilczewska, J. Malejko, W. Lewandowski,
Lanthanide complexes with pyridinecarboxylic acids - spectroscopic and thermal studies, Polyhedron (2018), doi:
https://doi.org/10.1016/j.poly.2018.04.045
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Lanthanide complexes with pyridinecarboxylic acids - spectroscopic and thermal studies
1
*
1
2
2
Grzegorz Świderski , Monika Kalinowska , Agnieszka. Z. Wilczewska , Julita Malejko ,
1
Włodzimierz Lewandowski
1
Białystok University of Technology, Department of Chemistry, Biology and Biotechnology,
Wiejska 45E, 15-351 Białystok, Poland
2
Institut of Chemistry, University of Bialystok, Ciolkowskiego Street 1K, 15-245 Bialystok
*
Coresponding autor:
Grzegorz Świderski swider30@gmail.com; tel.: 571 443 159, fax: 85 746 95 59
Abstract
The effect of 14 lanthanides on the structure and the electronic system of
isonicotinic acid was studied using IR (KBr), IR (ATR), Raman, UV-VIS,
spectrofluorometric, elemental analysis and thermogravimetric (TG/DTG) methods. The
influence of the lanthanides ions on the electronic charge distribution of the ligand is
discussed. The nephelauxetic parameters and the degree of covalency in the lanthanide-ligand
bonds were established. Moreover, the molecular structures of the lanthanide complexes with
isonicotinic, nicotinic, picolinic and benzoic acids were compared, with a particular emphasis
on the changes within the aromatic ring of metal complexes.
Keywords: isonicotinates, nicotinates, picolinates, lanthanides, pyridinecarboxylic acid,
picolinic acid
Introduction
Pyridinecarboxylic acids are a biologically important group of ligands. The location of
the nitrogen atom in the aromatic ring in the ortho, meta and para positions causes formation
of metal complexes with different types of coordination. The isonicotinic ligand may act as
(
a) a bidentate bridging ligand (Fig. 1 IC), e.g. terbium [1] and europium [2] complexes, (b)
bidentate chelating (Fig. 1 IB) e.g. terbium [1] and europium [2] complexes, (c) monodentate
Fig. 1 IA) e.g. magnesium [3] and zinc [4] complexes, or (d) tridentate bridging and
(
chelating (Fig 1. ID), e.g. in a lanthanum complex [5]. Additionally, the nitrogen atom from
the aromatic ring may participate in metal coordination (Fig. 1 IE-H) [6-11]. In the
lanthanide nicotinates, the carboxylate group may be (a) bidentate bridging (Fig. 1 IIC), e.g.
dysprosium [12] and cerium [13] compounds, (b) bidentate chelating (Fig. 1 IIB) e.g. in a

dysprosium complex [12], or (c) monodentate (Fig. 1 IIA) e.g. zinc [14] and molybdenum
15] compounds. In the nicotinate complexes, the lanthanide ions may be bonded only
[
through the nitrogen atom (Fig. 1 II E) [16,17] or by the nitrogen atom and a monodentate
carboxylate group (Fig. 1 II F) [18,19].
In the picolinic acid molecule, the nitrogen atom is in the ortho position relative to the
carboxylic group. Thereby, the metal cation may be coordinated through the N-atom and
-
COO group at the same time. This causes the formation of a five-membered chelating ring,
which may be crucial for maintaining the stability of the complex. The coordination mode in
picolinic acid complexes may be (a) monodentate through the carboxylate group and nitrogen
atom (Fig 1. IIIC), e.g. terbium [20] and iron [21] complexes, (b) bidentate chelating (Fig 1.
IIIB), e.g. in a cadmium compound [22], (c) bidentate bridging with additional bonding
through the nitrogen atom (Fig 1 IIIC), e.g. in a holmium complex [23] or (d) monodentate
and bidentate chelating (Fig 1. IIID), e.g. in a uranium compound [24].
Pyridinecarboxylic acids are of great biological importance. Nicotinic and picolinic
acids are synthetized from tryptophan. Picolinic acid is regarded as a natural chelator which
facilitates assimilation, e.g. for chromium(III) and zinc(II) ions [25,26]. Nicotinic acid
(
niacin, vitamin B3) takes part in the synthesis and degradation of carbohydrates, fatty acids
and amino acids, as well as other metabolic transformations [27]. Nicotinic acid blocks the
degradation of lipids in fat tissue, thereby reducing the level of free fatty acids in the blood
[
28,29]. Isonicotinic acid derivatives were formerly used to treat mental illness – most of
them were withdrawn from sale because of their negative effects on the liver [30].
In our previous papers the effect of different metal ions on the electronic system of
pyridinecarboxylic acids was studied [31-36]. The spectroscopic studies (FT-IR, FT-Raman,
NMR) and quantum chemical calculations (theoretical IR, NMR spectra, electronic charge
distribution, aromatic indices) showed that alkali [31] and alkaline [32] metal ions disturb the
electronic charge distribution of picolinic acid and the degree of disturbance increases in the
order Li→Na→K→Rb→Cs and Mg→Ca→Sr→Ba. Moreover, spectroscopic studies
revealed that 3d transition metal ions (i.e. Cu(II), Fe(III) and Ni(II) ions) stabilize the
electronic system of picolinic acid [33]. Similar results were obtained for benzoic, salicylic
and nicotinic acids [37-41]. The dependency between the electronic charge distribution in the
studied complexes and the location of the elements in the periodic table was established [37].
Namely, alkali and heavy toxic metal ions (e.g. Ag(I), Pb(II), Hg(I) and Hg(II) ions) disturb
the electronic charge distribution in the studied ligands, whereas 3d and 4f metal ions (e.g.
Cr(III), Fe(III) and Ln(III)) stabilize it. The stabilization of the aromatic system in lanthanide

complexes is associated with the nephelauxetic effect. The nephelauxetic effect [42-44] is to
expand the probability of finding an electron in the central ion. This effect, typical for ions
with partially filled subshells, is caused by the penetration of electrons from the ligand into
the unfilled orbitals of the central ion. Donor electrons cause a decrease in the effective
charge of the nucleus, changing its central field. The central ion electrons, subjected to the
effective charge of the nucleus, increase the radial dimensions of their orbitals, which causes a
weakening of the inter-electron repulsion. The measure of the expansion of the cloud of
electron density of the metal under the influence of a ligand in the complex is the
nephelauxetic parameter [44-47]. In the La-Lu series, the degree of covalency of the bonds
increases, whereas the delocalization of the “f” orbitals decreases [45]. The covalency of
bonds in complexes is determined by the nephelauxetic effect of the ligands [43-44].
In the present work the physiochemical properties of a series of 14 lanthanide
isonicotinates and selected lanthanide nicotinates, picolinates and benzoates were studied by
spectroscopic and thermogravimetric methods.
Material and methods
Sample preparation
A 10 ml of water solution of lanthanide chlorides (that contain 0.2 mole of the
lanthanide ions) was added to a 10 ml water solution of sodium isonicotinate (0.6 moles), so
the metal:ligand stoichiometric ratio was 1:3. After a few days precipitates of the lanthanide
isonicotinates formed. The precipitates were filtered and washed with distilled water. The
o
solid residue was dried in a dryer at 90 C for 48h. In the same way the neodymium
nicotinate, picolinate and benzoate were obtained. The sodium salts of the
pyridinecarboxylates were synthesized by mixing the appropriate volume of sodium
hydroxide and the pyridinecarboxylic acids (the stoichiometric ratio was 1:1). The mixtures
o
were slowly evaporated on a water bath and the solid residue was dried at 90 C for 48h.
Measurements
-1
The FT-IR spectra were recorded with the KBr pellet method in the range 400-4000 cm
-
1
(
the resolution was 4 cm ) using an Equinox 55 FT-IR spectrometer. The ATR FT-IR spectra
were registered in the same range with the use of an Alfa spectrophotometer (Bruker). In this
paper the changes in the positions of individual bands from the IR spectra of the tested
compounds were discussed. Sometimes, quite small differences in the shifts of the
corresponding bands from the spectra of the series of compounds were observed. In order to

check the effect of the KBr matrix on the band locations, the ATR spectra were also registered
and compared. No effect of the KBr matrix on the band shifts was observed.
-1
The FT-Raman spectra were recorded in the range 4000–100 cm with a Multi-Raman
-
1
(
Bruker) spectrophotometer (the resolution was 4 cm ).
The UV and VIS spectra of aqueous solutions of the tested compounds (concentration 5 x
-5
-2
1
0 M and 5 x 10 M) were recorded using a DR 4000U HACH in the range 190-800 nm.
The luminescence spectra were registered using a F-7000 FL spectrofluorometer. The
-
4
emission and excitation spectra were recorded for aqueous solutions at the concentration 10
M, at a pH value close to neutral (7.1-7.2). The pH was corrected by the addition of microliter
amounts of NaOH at a concentration of 0.1 M. Thermogravimetric analysis (TGA) was
performed on a Mettler Toledo Star TGA/DSC1 unit. Argon was used as a purge gas (20 ml
-
1
min ). Samples (2-4 mg) were placed in aluminum pans and heated from 50 to 900°C with a
heating rate of 10 ºC/min.
Calculations
On the basis of the VIS spectra recorded for lanthanide ions and lanthanide complexes
with isonicotinic, nicotinic, picolinic and benzoic acids, the degree of bond covalency
between the metal and the ligand was calculated. The measure of the covalency can be
defined in terms of the nephelauxetic effect, which refers to the increase in the probability of
finding an electron in the central ion. The nephelauxetic parameter, β, describes the increase
in the cloud of the electronic charge density of metal ion under the influence of a ligand [48]:
1


(

av(complex) /av(aq. jon))
(1)

n
where νav is the average value of the band location and n is the number of electronic
transitions.
Sinha proposed the δ parameter which describes the degree of covalent bonding in metal
complexes [49]:
1

 (1 )100%
(2)

Results and discussion
IR and Raman spectra
The analysis of the bands from the IR spectra assigned to the vibrations of the
carboxylate anion of the lanthanide isonicotinates showed that isonicotinic acid may

coordinate to the lanthanide ions in different fashions. The bands derived from the
-
asymmetric stretching vibrations as(COO ) of the carboxylate group were located in the
-1
-1
-1
ranges 1542-1549 cm (IR KBr), 1542-1549 cm (IR ATR) and 1542-1550 cm (Raman),
-
-1
whereas the symmetric stretching vibrations  (COO ) were located at 1406-1418 cm and
s
-1
-1
-1
1
384-1385 cm (IR KBr), 1403-1416 cm (IR ATR) and 1417-1422 cm (Raman). The type
of metal coordination may be analysed on the basis of the difference between the values of the
-
-
-
-
wavenumbers of the bands assigned to the as(COO ) and 
s
(COO ), i.e. Δ(COO )=as(COO
-
-
)
-
s
(COO ) [37]. The Δ(COO ) parameter calculated for the lanthanide isonicotinates was in
-1
the range 128-138 cm and is lower or almost equal to the value calculated for sodium
-1
isonicotinate (137 cm ). This indicates that in the molecules of the lanthanide isonicotinates
the carboxylate group is slightly polarized (equalization of the C-O bonds) and the metal ion
is coordinated through bidentate chelating and/or bidentate bridging bonds. In the case of
several isonicotinates, additional bands assigned to the symmetric stretching vibration
-
-1
 (COO ) were observed in their IR spectra, i.e. for the lanthanide (1384 cm ), neodymium
s
-1
-1
(
1385 cm ) and europium (1384 cm ) complexes. It points to an additional monodentate or
tridentate coordination of the lanthanides by isonicotinic acid.
The literature crystal data for metal isonicotinates showed that the lanthanide ions are
coordinated by bidentate bridging (Fig. 1c) [50] as well as tridentate chelating and bridging
(
Fig. 1D) [51] bonds, which is in accordance with the analysis of the IR spectral data obtained
-
in this work. In the case of cerium isonicotinate, the value of the Δ(COO ) parameter was
similar to the value obtained for sodium isonicotinate, which indicated a bidentate bridging
or/and bidentate chelating type of coordination in the cerium complex. The crystal data for Ce
isonicotinate showed the bidentate bridging type of coordination in this molecule [50]. The
-
analysis of the wavenumbers of the bands derived from the (COO ) vibrations for the
neodymium and europium isonicotinates showed a similar type of metal coordination as was
observed in the lanthanide isonicotinate (i.e. bidentate chelating and monodentate chelation,
or tridentate chelating). There is no literature crystal data on Nd isonicotinate, but the
published crystal structure for Eu isonicotinate [51] showed bidentate chelating and bidentate
bridging bonding (Fig. 2B). There is no tridentate or monodentate types of coordination in the
Eu isonicotinate molecule which were suspected to be present taking into account the IR data
-
-
(
i.e. the values of the Δ(COO ) parameter). The values of the Δ(COO ) parameter may be
affected by evident polarization of the bidentate bridging bond which is reflected in the Eu-O
bond lengths in the carboxylate anion (i.e . 2.338 and 2.403 Å [46]). In the case of the terbium

-
isonicotinat,e the value of Δ(COO ) showed the bidentate (bridging and /or chelating) type of
metal coordination. In the crystal structure of Tb isonicotinate both types of coordination exist
[
50] (Fig. 2A). In the structures of the praseodymium, samarium, dysprosium, holmium,
erbium, thulium, iterbium and lutetium isonicotinates, the bidentate (bridging and /or
chelating) bonding [52] is present due to the low polarization of the metal-ligand bonds.
When comparing the IR and Raman spectra of lanthanide and sodium isonicotinates,
some distinct differences were observed (Table 1). The differences concerned the number,
wavenumber and intensity of the aromatic ring vibration bands. There were more evident
differences between the spectra of picolinic acid and its sodium salt than the lanthanide
complexes. The same was noticed in the case of benzoic acid and its metal complexes [53,49].
In the spectra of sodium isonicotinate, several bands assigned to the aromatic ring vibrations
disappeared (i.e. 8b IR, 8b Raman, 19a IR, 17b IR and Raman, 6a Raman),whilst the other
bands were shifted toward lower wavenumbers (8a IR and Raman, ʋCN IR, 9a IR and Raman,
1
8b IR and Raman, 12 IR and Raman, 17a IR, 6b IR) and had decreased intensities (19b IR
and Raman, 9a IR and Raman, 18a IR and Raman, 12 IR and Raman, 17a IR) compared with
the appropriate bands in the IR and Raman spectra of the lanthanide isonicotinates. The most
-1
distinct difference in the location of the bands concerned the band no. 18b (about 23 cm ). In
-
1
the case of the other bands, the difference did not exceed 10 cm . The increase in the
wavenumber and intensity of the bands assigned to the aromatic ring vibrations in the spectra
of the lanthanide isonicotinates comparing with the spectrum of sodium isonicotinate
suggested that the lanthanide ions may stabilize the electronic system of the isonicotinic
ligand. The same observations were reported in the case of other ligands, such as benzoic
[
54], salicylic [55] and triaurinecarboxylic acids [56]. In the series of La→Lu isonicotinates
the wavenumbers and intensities did not change in a regular fashion in contrast to the regular
changes that were observed in the case of the Li→Na→K→Rb→Cs isonicotinates [36] or
picolinates [31]. The transition metals, including lanthanides, slightly deform the electronic
charge distribution in the ligand molecule due to the formation of many delocalized covalent
bonds. This may guarantee to maintain the distribution of the electronic system in the
complexes of isonicotinic acid, similar to that observed in the isonicotinic acid molecule [57].
On the other hand, the strong polarization of the metal–ligand bonds causes a deformation of
the electronic charge distribution in the ligand molecule, which was observed in the case of
alkali metal isonicotinates [37] as well as benzoates [54], picolinates [31] and
halogenobenzoates [58,59].

UV spectra
In the UV spectra of lanthanide isonicotinates bands assigned to π→π* transitions
occurred. The maxima of the bands were located between 264.0 and 266.6 nm (Table 2). The
lanthanide complexes absorbed at higher wavelengths than the ligand (i.e. a bathochromic
shift of the π→π* bands). Moreover, the complexes of heavy lanthanide complexes absorbed
at higher wavelengths than the light lanthanide complexes. So there was a bathochromic shift
of the π→π* bands in the series of light lanthanides < heavy lanthanides. It was also observed
in the case of lanthanide benzoates [57]. In the series of La→Lu isonicotinates, the changes in
the values of the absorption maxima were irregular and insignificant.
Visible spectra
Some of the studied lanthanide isonicotinates absorbed in the visible range and the
bands were assigned to the f→f transitions of the central ions (Tables 3 and 4; Fig. 4). In the
frame of this work the visible spectra of neodymium, praseodymium, erbium, holmium and
samarium isonicotinates, their aqua ions as well as the neodymium complexes with nicotinic,
picolinic and benzoic acid were registered. Comparing the spectra of the lanthanide
carboxylates and their aqua ions, one could see a bathochromic shift and an increase in the
intensity of several bands in the spectra of the isonicotinate complexes. It showed an increase
in the covalency of the metal-ligand bond in comparison with the appropriate bands in the
aqua ions. The VIS spectral data was used to calculate the degree of bond covalency and the
obtained data pointed to an increase in the covalency in the series Pr→Nd→Sm→Ho→Er
isonicotinates (Table 4) with the increase in the atomic number of the lanthanides. Moreover,
in the series of central atoms La→Lu, there was a decrease in the degree of delocalisation of
the f orbitals. The values of the nephelauxetic parameters decreased in the order
Nd→Sm→Ho→Er isonicotinates.
In the series of La → Lu lanthanides, the atomic and ionic radii decrease. This
phenomenon is called contraction and is the result of the impact of the increasing charge of
the nucleus on the slightly changing 4f electron shell. As the size of the cations decreases,
their polarization capacity increases in the lanthanide series, which increases the nature of the
covalent bonds. Analogous effects have been described in the literature, and also observed in
our previous studies [45,53,55,57]. On the basis of the nephelauxetic calculated parameters
for neodymium complexes with benzoic as well as pyridinecarboxylic acids, the ligands can
be ordered according to the increasing values of the parameter, i.e. picolinic acid→nicotinic
acid→isonicotinic acid→benzoic acid (Table 3). The decrease in the covalency of the

neodymium–ligand bond occurred in the same order. For a more distant the location of the
nitrogen atom in the ring from the carboxylic group, a stronger nephelauxetic effect was
observed. The lack of a nitrogen atom in the ring of the benzoic acid molecule caused an
additional increase in the nephelauxetic effect.
Spectrofluorometric study
The fluorescence spectra of aqueous solutions of the lanthanide complexes with
isonicotinic acid as well as lanthanide aqua ions were measured. The complexes of Sm, Eu,
Tb and Dy were selected for this study. The emission spectrum of terbium isonicotinate
(
Figure 5B), upon excitation at 274 nm, showed four emission bands at 492, 547, 588 and 624
5
7
3+
nm, corresponding to the characteristic D
4
– F transitions (J = 6, 5, 4, 3) of the Tb ions.
J
The presence of characteristic emission bands of the Tb(III) ion indicates that an
intramolecular energy transfer between the ligand and the metal ion occurs. It can be seen
from Figure 6A that the fluorescence intensity for the Tb(III) ions is negligible. The intensity
of fluorescence of the Tb(III)-isonicotinic acid complex was comparable. However, the
concentration used to measure the emission spectra of the complex was two orders of
magnitude lower than that used for Tb(III) ions. Therefore, it can be concluded that the
terbium fluorescence was enhanced in the presence of isonicotinic acid. In the case of other
lanthanides (Sm, Eu and Dy), under the experimental conditions used, no characteristic
emission bands of the Ln(III) ions were observed in the fluorescence spectra of their
complexes with isonicotinic acid. This is in agreement with the observations of Chen and
Fukuzumi, [60] who revealed that isonicotinic acid is not suitable for the excitation of Sm,
Eu, and Dy ions. They also shown that the fluorescence properties of lanthanide complexes
can be affected by many factors, such as the type of metal, the type and number of organic
ligands that can absorb energy, the extent of the conjugation of the complex and the number
of the coordinated water molecules. To study the influence of the type of ligand, we compared
the fluorescence spectrum of terbium isonicotinate (Figure 5B) with the spectra of terbium
nicotinate (Figure 5C) and picolinate (Figure 5D). The observed intensities of the Tb(III)
emission lines indicated that the fluorescence enhancement was the strongest for the complex
with picolinic acid and the weakest for the complex with isonicotinic acid. Amanda et al. also
observed that picolinic acid, nicotinic acid and dipicolinic acid reinforced the fluorescence of
terbium [61].
Elemental analysis and thermogravimetric study

The synthesized lanthanide complexes with isonicotinic acid were mostly anhydrous,
with the general formula LnL (it should be noticed that the obtained solid residue of the
complexes were dried at 90 °C before spectral and thermal analysis). Some of the complexes
remained hydrated as LnL ‧ nH O (where n is 1, 2 or 4) (Table 5). The metal:ligand ratio was
:3, which was proven by their elemental analyses (Table 5). Isonicotinic acid was stable
3
3
2
1
below 160 °C, but at higher temperatures it underwent a one-step decomposition. The
anhydrous lanthanide isonicotinates decomposed in two stages. In the first stage of thermal
decomposition, about 30-40% of the complex mass was lost. This process is related to thermal
decarboxylation. This process takes place in the temperature range from about 400 to 550/600
o
C. In the next stage, the aromatic ring usually breaks down slowly (under anaerobic
o
conditions). The process was conducted to a temperature of 850 C. The end products at this
temperature were probably oxides of lanthanides and residues of unburnt carbon from the
aromatic pyridine ring. The least thermally stable complex among the respondents was
o
europium isonicotinate. The process of its decay began at a temperature of 360 C. The most
thermally stable complexes were the cerium, samarium and gadolinium isonicotinates. They
decomposed above 470 °C.
The thermal decompositions of selected compounds are shown in Figure 6. The
presence of crystallization water in the hydrated lanthanide complexes was also observed in
the infrared spectra in the form of wide vibrational bands of the OH groups in the range of
-1
approximately 3066-3096 cm .
Conclusion
1
. The analysis of IR and Raman spectra of lanthanide isonicotinates showed that
lanthanide ions, to a small extent, deform the electronic charge density within the
ligand molecule. This is due to the formation of many delocalized covalent bonds
between the metal and the ligand.
2
. The UV spectra of the isonicotinate complexes showed that heavy lanthanides absorb
at higher wavelengths than the light lanthanides. There is a bathochromic shift of the
*
π→π bands in the order of light lanthanides < heavy lanthanides. In the series of
*
lanthanide isonicotinates, the changes in the position of the π→π bands are slight and
irregular.
3
. The values of the nephelauxetic parameter decrease in the series Nd→Sm→Ho→Er
isonicotinates. Moreover, an increase in the value of the nephelauxetic index and a
decrease in the covalency of the metal-ligand bond are observed in the neodymium

complexes with the series picolinic acid→nicotinic acid→isonicotinic acid→benzoic
acid. The effect of the lanthanide ions on the electronic system of pyridene carboxylic
acid is strongly influenced by the location of the nitrogen atom in the ring of the
ligand.
4
. The intensity of fluorescence of lanthanide pyridinecarboxylates depend on the
position of the nitrogen atom in the aromatic ring. The largest increase in the
fluorescence is observed for terbium isonicotinate. The measurements were done at
pH ~ 7.1-7.2.
Acknowledgements
Studies have been carried out in the framework of the work no. S/WBiIŚ/3/2017 and
financed from the funds for science MNiSW.
Thermogravimetric analysis was performed at the Center of Synthesis and Analysis
BioNanoTechno of the University of Bialystok. The equipment of the Center of Synthesis and
Analysis BioNanoTechno of University of Bialystok was funded by the EU, project:
POPW.01.03.00–20–034/09–00.
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5
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Figures list:
Fig. 1. Type of coordination of the isonicotinate (I), nicotinate (II) and picolinate (III) metal
complexes
Fig. 2a. Crystallographic structure of terbium isonicotinate [50]
Fig. 2b. Crystallographic structure of europium isonicotinate [51]
Fig. 3a. IR spectra of isonicotinic acid (A), sodium isonicotinate (B), praseodymium
isonicotinate (C) and holmium isonicotinate (D)
Fig. 3b. Raman spectra of isonicotinic acid (A), sodium isonicotinate (B), praseodymium
isonicotinate (C) and holmium isonicotinate (D)

Fig. 4. Visible spectra for the neodymium aquo ion and neodymium picolinate, isonicotinate
and nicotinate complexes
-2
3
Fig 5. Emission spectra of (A) Tb(III) ions (10 mol/dm ), λexc = 348 nm; (B) the Tb(III)-
-4
3
isonicotinic acid complex (10 mol/dm ), λexc = 274 nm; (C) the Tb(III)-nicotinic acid
-
4
3
-4
complex (10 mol/dm ), λexc = 274 nm; and (D) the Tb(III)-picolinic acid complex (10
3
mol/dm ), λexc = 276 nm
.
Fig 6. TG and DTA decomposition curves of Nd(ISO)
Dy(ISO) (anhydrous complex) B, Na(ISO)
hydrated
3
4H O (hydrated complex) A,
2
.
3
3
(anhydrous complex) C and Eu(NIC)
complex)
3
2H O
2
(
D

-
1
Table 1. The wavenumbers [cm ] of selected bands that occurred in the IR and Raman spectra of isonicotinic acid and the lanthanide isonicotinate complexes
Isonicotinic
acid
Isonicotinates
La
Assignment
s
Assignme
nts
according
Na
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
to Wilson
[62]
IR KBr
IR ATR
Raman
3449 m *
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
(OH) **
(CH)ar
(C=O)
(CC)ar
(CC)ar
-
-
IR KBr
IR ATR
Raman
3053 w
-
3077 m
-
-
3065 m
-
3060 m
-
-
3051 s
-
-
3066 m
-
3066 m
-
3066 m
-
3077 m
-
-
3076 m
-
3072 m
-
3073 m
-
7b
-
-
-
-
3056 w
3072 vs
3066 s
3066 s
3069 w
3069 w
3067 vs
3071 m
3067 s
3069 vs
3069 m
3066 vs
3069 s
3071 vs
3073 vs
3073 vs
IR KBr
IR ATR
Raman
1714 s
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1712 m
1690 vw
IR KBr
IR ATR
Raman
1616 m
1616 w
1617 m
1589 vs
1587 s
1603 s
1606 s
1604 m
1605 s
1604 s
1602 s
-
-
-
-
1599 s
1599 s
1598 m
1599 vs
1598 s
1600 vs
1600 m
1609 vw
1596 vs
-
1598 vs
-
1595 vs
-
1593 vs
-
1595 vs
-
8a
8b
-
-
-
-
1600 m
1606 s
1604 w
1600 m
1604 w
16004 vs
1602 s
1602 s
1600 s
1600 m
1602 s
IR KBr
IR ATR
Raman
1566 m
-
-
-
-
1589 s
1587 s
1577 w
1589 s
1586 s
1581 m
1593 s
1589 s
-
1588 vs
1587 s
-
1589 s
1586 s
-
1581 s
1579 vs
1581 vs
1580 s
-
-
-
-
-
1568 vw
1571 vw
1587 s
1577 w
1579 s
-
-
1580 s
-
1589 s
-
1585 s
1584 vw
1583 s
1584 w
1587 s
-
1571 vw
1594 vw
-
IR KBr
IR ATR
Raman
-
-
-
1545 vs
1544 vs
1552 w
1547 s
1544 s
1548 m
1545 s
1545 s
1548 m
1544 s
1544 s
1546 m
1545 s
1542 vs
1542 s
1544 s
1547 vs
1546 s
1547 vs
1546 s
1547 vs
1546 s
-
1546 vs
1545 s
1548 vs
1546 s
1547 vs
1546 s
1549 vs
1548 s
1549 vs
1546 s
as(COO )
1544 s
1542 s
1546 vw
1538 vw
1550 vw
1548 w
1548 w
1548 w
1552 w
1542 w
1542 w
1543 w
IR KBr
IR ATR
Raman
-
1500 w
1505 vw
1500 w
1496 m
1492 m
1494 w
1494 m
1495 m
1494 w
1496 m
1495 m
1496 m
1496 m
1495 m
1496 vw
1494 s
1496 m
-
1498 m
1503 m
1500 m
1498 m
1495 w
1498 m
1503 s
1497 m
1500 m
-
1496 m
1495 w
1496 w
1497 m
1495 w
1500 w
1497 m
1495 w
1498 w
1497 m
1497 w
1498 m
(CC)ar
(CC)ar
19b
19a
-
1495 m
1496 vw
1504 m
1504 vw
1500 vw
1498 vw
IR KBr
IR ATR
Raman
-
-
-
-
-
-
-
-
-
-
-
-
-
1425 vs
1423 s
1426 vs
-
1428 vs
1425 s
-
-
-
1433 vs
1432 vs
1446 s
1433 vs
-
-
-
-
-
1429 s
1440 s
-
1429 s
1444 s
1438 m
1432 vw
1434 w
1436 w
1422 vs
1438 vs
1436 w
1438 s
1445 s
-
IR KBr
IR ATR
Raman
-
-
-
1413 vs
1410 vs
1415 vw
1412 s
1413 vs
1409 vs
1419 s
1406 vs
1403 vs
-
1411 s
1405 vs
-
1408 vs
1405 vs
-
1409 vs
1409 vs
1417 w
1409 vs
1408 vs
-
1411 vs
1409 vs
-
1411 vs
1409 vs
-
1418 vs
1410 vs
1422 s
1416 vs
1413 vs
-
1416 vs
1412 vs
-
1418 vs
1416 vs
-
1418 vs
1413 vs
-
s(COO )
1410 vs
1417 m
-
IR KBr
IR ATR
Raman
-
-
-
-
-
-
1384 vs
-
-
-
-
-
-
1385 s
-
-
-
1384 vs
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
s(COO )
-
-
-
-
1386 w
IR KBr
IR ATR
1338 s
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
(OH)
1337 m

Raman
1334 w
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
IR KBr
IR ATR
Raman
1314 w
-
-
1321 m
1330 m
1322 vw
1320 w
1328 m
1322 vw
1320 m
1328 w
1320 vw
-
1319 w
1320 m
1320 w
1319 w
1320 m
1320 w
1316 vw
1320 vw
1320 vw
1320 w
1320 m
-
1319 vw
1318 vw
1322 vw
1320 vw
1320 vw
1320 vw
1320 vw
1318 vw
1322 vw
(CC)ar
(C-O)
(CH)
(C-N)ar
(CH)
(CH)
(CH)
(CH)
(CH)
-
14
1316 vw
1322 vw
-
1321 vw
1320 vw
1320 m
-
1318 vw
1322 vw
1320 vw
1318 vw
IR KBr
IR ATR
Raman
1303 s
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1300 w
1311 vw
IR KBr
IR ATR
Raman
1234 s
1232 m
1237 w
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
IR KBr
IR ATR
Raman
1215 s
1221 m
1221 w
1222 w
1224 w
1222 m
1218 w
1218 m
1222 w
1220 w
1219 m
1225 m
1220 m
1221 vw
1218 m
1225 m
1224 m
1214 vw
1221 w
1221 m
1220 vw
1221 w
1222 m
1222 m
1221 w
1224 vw
1222 m
1221 s
1222 w
1218 w
1222 w
1222 w
1220 m
1222 w
1225 w
1218 w
1222 w
1224 w
1222 w
1222 w
1222 w
1222 w
1222 w
1222 vw
1222 m
1215 m
1212 m
1220 vw
IR KBr
IR ATR
Raman
1147 s
1153 w
-
1160 vw
-
1160 w
-
1161 w
1156 m
1158 m
1161 vw
1157 m
1156 w
1160 w
1158 w
1154 vw
1153 w
1156 w
1161 vw
-
1161 vw
1167 vw
1158 m
1163 vw
1167 w
-
1161 vw
-
1154 vw
1154 vw
1156 m
1154 vw
1160 vw
1150 vw
1156 vw
1154 vw
1152 w
1154 vw
1154 vw
1154 m
9a
1147 m
1141 vw
1150 m
1158 m
1158 m
1158 vw
1162 m
1158 m
IR KBr
IR ATR
Raman
1093 s
-
1068 w
1088 vw
-
1088 w
1088 w
1089 vw
1089 w
1088 m
1089 vw
1091 vw
1089 m
-
1082 w
1085 w
1085 vw
1082 w
1085 vw
1085 m
1085 vw
1086 vw
1082 vw
1078 vw
1087 vw
1081 vw
-
-
-
1082 w
-
1082 vw
-
18b
1071 vw
1068 vw
-
-
-
-
-
-
-
-
1082 vw
1085 vw
1085 vw
1085 vw
1083 vw
IR KBr
IR ATR
Raman
1030 vs
1028 m
1027 s
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
IR KBr
IR ATR
Raman
-
-
-
1061 w
1061 w
1062 m
1069 m
1061 w
1062 w
1069 vw
1062 m
1062 m
1066 w
1062 w
1062 m
1066 vw
1062 m
1062 w
1066 vw
1061 w
1062 m
1068 vs
1061 w
1062 m
1062 vw
1061 w
1061 m
1059 w
1066 vw
1061 w
1061 vw
1064 w
1061 w
1062 w
1062 w
1062 vw
1061 vw
1066 vw
18a
12
1062 vw
1068 vw
1059 vw
1064 vw
1059 vw
1064 vw
1061 vw
1066 vw
1054 vw
1066 vw
IR KBr
IR ATR
Raman
-
-
-
997 w
997 vw
998 s
1003 vw
1003 m
1000 vs
1000 w
1003 w
1000 vs
1004 w
-
1004 vw
1003 m
1006 w
1007 m
1008 w
1006 m
1006 w
1005 w
1006 m
1010 w
1009 m
1014 s
1010 w
1010 vw
1008 vs
1010 m
1010 w
1014 w
1004 w
1011 vw
1008 s
1004 w
1011 vw
-
1006 vw
1018 vw
1017 w
1004 vw
1018 w
1017 m
1004 vw
1014 vw
1015 m
1004 vs
IR KBr
IR ATR
Raman
-
-
-
-
-
994 s
994 m
994 m
-
990m
994 s
992 vw
990 m
994 vs
994 m
994 m
994 vs
IR KBr
IR ATR
Raman
-
-
-
-
890 vw
896 vw
901 w
-
892 vw
-
-
-
891 vw
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
γ(CH)
γ(CH)
17b
17a
885 m
892 vw
-
-
-
-
-
-
881 vw
-
885 w
-
887 vw
-
887 w
-
887 vw
-
IR KBr
IR ATR
Raman
857 s
862 w
862 w
865 vw
870 vw
874 vw
874 w
-
-
-
-
872 vw
867 m
862 m
-
-
-
-
-
-
-
857 s
-
-
-
-
869 vw
-
IR KBr
IR ATR
-
-
853 w
853 w
840 w
847 m
845 w
845 m
847 w
850 m
848 vw
848 m
857 m
848 m
862 w
862 m
864 w
864 m
865 w
846 w
865 m
865 m
865 w
868 w
865 w
865 w
867 w
871 w
870 w
872 w
867 w
872 w
s(COO )

Raman
-
852 m
853 m
855 s
855 s
855 w
855 m
855 w
867 s
857 m
865 w
871 m
852 m
871 w
873 w
873 m
IR KBr
IR ATR
Raman
-
-
-
776 s
778 m
779 m
-
778 m
777 m
-
769 m
770 s
773 w
770 s
-
770 s
769 m
-
768 m
763 s
-
773 s
773 s
770 m
-
773 vs
772 s
-
773 m
770 m
774 vw
770 m
768 s
770 m
768 m
-
769 m
-
770 m
768 m
772 vw
γs(COO-)
(CCC)
(CCC)
(CCC)
(CCC)
(CCC)
-
-
772 s
778 vw
774 vw
778 vw
767 vw
IR KBr
IR ATR
Raman
-
712 s
711 m
-
712 m
712 m
713 vw
712 m
712 m
713 vw
711 m
711 s
711 w
711 s
-
712 s
711 m
-
712 m
711 s
-
711 m
711 s
712 m
712 m
715 vw
711 s
711 m
-
714 m
-
712 m
708 s
712 m
708 m
709 vw
708 m
707 s
710 m
709 m
711 vw
6a
6b
4
-
705 vw
711 vw
709 vw
724 vw
715 vw
705 vw
IR KBr
IR ATR
Raman
698 s
697 m
-
698 s
698 s
-
698 m
701 m
697 vw
-
-
-
698 m
-
-
-
697 m
653 s
-
-
-
-
IR KBr
IR ATR
Raman
677 s
675 s
664 m
684 s
671 m
671 s
670 s
670 s
666 m
671 s
673 s
666 s
673 m
673 s
685 s
673 s
666 m
684 m
683 s
678 m
677 s
666 s
677 m
677 m
682 vw
677 s
675 m
-
678 m
678 s
671 s
-
680 m
683 m
-
-
680 m
683 s
-
-
684 s
-
-
-
682 vw
666 m
666 vw
666 w
IR KBr
IR ATR
Raman
658 w
659 w
664 w
666 m
668 m
-
666 w
668 s
-
666 m
-
-
671 m
670 s
671 m
669 m
666 m
-
-
659 m
666 m
670 m
664 w
664 w
IR KBr
IR ATR
Raman
-
-
-
592 w
596 m
592 m
-
598 w
591 m
-
598 w
595 m
-
599 vw
600 m
-
609 m
602 m
-
-
-
-
-
-
-
-
-
-
-
-
591 m
-
582 m
-
578 w
-
576 w
-
576 w
-
573 m
-
575 w
-
575 w
576 w
576 w
-
-
IR KBr
IR ATR
Raman
-
-
-
528 w
540 m
542 m
538 m
548 vw
542 m
545 s
547 w
547 s
-
538 m
537 m
539 vw
547 w
534 m
-
562 w
565 s
561 w
561 m
-
564 m
562 m
-
562 w
562 m
-
559 m
564 s
561 w
562 m
564 vw
561 w
562 m
-
561 w
562 m
564 vw
as(COO )
-
-
-
-
547 vw
554 vw
562 vw
*
*
The intensities of the bands were assigned as: vs – very strong, s - strong, m - medium, vw – very weak, w – weak
* The types of vibrations were assigned as: ν – stretching vibrations, β – in-plane deforming vibrations, βring – in-plane deforming vibrations of the ring, γ – out-of-plane deforming vibrations, - deforming vibrations
of the ring, sym – symmetric vibrations, as – asymmetric vibrations

-5
Table 2. The maximum of absorption [nm] from the UV spectra of lanthanide isonicotinate complexes (in water solution, 5 x 10 M, pH = 7.2).
Compound name
Max absorption
UV spectra [nm]
Molar absorption
coefficient
3
-1
-1
10 [l mol cm ]
Isonicotinic acid
264.0
266.0
265.0
264.0
264.8
265.4
264.6
265.8
264.8
265.6
266.2
266.2
265.0
266.6
266.0
266.2
1
2
1
1
2
1
2
1
1
1
1
1
1
0
1
0
.00
.20
.30
.86
.16
.90
.04
.56
.84
.20
.14
.12
.10
.42
.06
.64
Sodium isonicotinate
Lanthanum isonicotinate
Cerium isonicotinate
Praseodymium isonicotinate
Neodymium isonicotinate
Samarium isonicotinate
Europium isonicotinate
Gadolinum isonicotinate
Terbium isonicotinate
Dysprosium isonicotinate
Holmium isonicotinate
Erbium isonicotinate
Thulium isonicotinate
Iterbium isonicotinate
Lutetium isonicotinate

Table 3. The main absorption bands from the VIS spectra, nephelauxetic parameters and bond covalency for neodymium complexes with benzoic acid and
pyridinecarboxylic acids
Transition
from the
ground
Neodymium aquo ion
Neodymium benzoate
complex
Neodymium nicotinate
complex
Neodymium isonicotinate Neodymium picolinate
complex
complex
Wavenumber/
Molar Wavenumber/
Molar Wavenumber/
absorp λmax
tivity
Molar Wavenumber/
absorp λmax
tivity
Molar Wavenumber/
absorp λmax
tivity
Molar
absorp
tivity
(ε) at
4
level I9/2
λmax
absorp λmax
tivity
(ε) at
(ε) at
(ε) at
(ε) at
λmax
λmax
λmax
λmax
λmax
-1
-1
-1
-1
-1
-
1
[l mol
-1
[l mol
-1
[l mol
-1
[l mol
-1
[l mol
[
cm ]
[nm]
-1
[cm ]
[nm]
-1
[cm ]
[nm]
-1
[cm ]
[nm]
-1
[cm ]
[nm]
-1
cm ]
cm ]
cm ]
cm ]
cm ]
4
H
9/2
7/2
3/2
12594
13514
13661
14727
17422
19157
19531
21008
21368
21692
23419
794
740
732
679
574
522
512
476
468
461
427
11.1
7.0
4.4
0.6
6.7
3.9
1.7
0.6
0.6
0.6
0.4
12563
13514
-
796
740
-
8.2
6.4
-
12594
13514
13661
14706
17360
19157
19531
21008
21277
21696
23365
794
740
732
680
576
522
512
476
470
461
428
9.8
7.1
4.2
1.0
8.1
4.6
2.4
1.4
1.4
1.4
1.4
12594
13514
13661
14727
17361
19157
19531
21008
21276
21692
23364
794
740
732
679
576
522
512
476
470
461
428
13.6
10.0
6.5
12531
13477
13624
14706
17301
19084
19531
21008
21277
21645
23364
798
742
734
680
578
524
512
476
470
462
428
12.1
10.6
6.8
4
F
S
F
4
4
9/2
2
14706
17361
19157
19570
21053
21368
21692
23364
680
576
522
511
475
468
461
428
0.8
8.3
3.9
2.0
0.9
0.8
0.9
0.8
2.6
2.0
4
G
5/2, G7/2
11.0
7.4
13.8
6.7
4
G
7/2
9/2
2
2
G
4.8
3.7
-
3.6
2.1
D
3/2
3.5
2.1
4
G
11/2
3.6
2.1
2
P
1/2
3.3
1.9
Covalency (δ) and nephelauxetic ratio (β)
β
δ
0.9995
0.0456
0.9988
0.1216
0.9989
0.1129
0.9972
0.2762

Table 4. The main absorption bands from the VIS spectra, nephelauxetic parameters and bond covalency for lanthanide complexes with isonicotinic acid
Praseodymium
aquoion
Samarium
aquoion
Holmium
aquoion
Erbium
aquoion
isonicotinate
isonicotinate
isonicotinate
isonicotinate
Wavenumber/
Wavenumber/
Transition Wavenumber/ Wavenumber/ Transition Wavenumber/
Wavenumber/
Transition
from the
Wavenumber/
Wavenumber/
Transition
from the
ground
λmax
λmax
from the
λmax
λmax
from the
ground
λmax
λmax
λmax
λmax
ground
ground
3
6
5
4
level H
4
level H5/2
level I
8
level I15/2
-
1
-1
-1
-1
-1
-1
-1
-1
[
cm ]
[nm]
444
[cm ]
[nm]
444
[cm ] [nm] [cm ] [nm]
[cm ] [nm]
[cm ]
[nm]
416
[cm ] [nm]
[cm ]
[nm]
3
4
5
5
2
2
2
2523
1368
22523
P
2
0
25000
24096
400
415
24876 402
24038 416
F
7/2
5/2
24038
22222
416
450
24038
G
5
6
24691
22222
405
450
24510
408
448
H
9/2
3
3
1
6
4
4
468
481
589
21368
20747
16949
468
482
590
P
P
22124
21142
18657
15576
452
473
536
642
G
22321
20243
19157
F
7/2
5
5
5
2
2
1
0790
6978
P
1
22727
21598
440
463
477
22727 440
21552 464
20921 478
I
15/2
21368
18622
15576
468
537
642
F
2
F
4
F
5
20284
19157
18450
493
522
494
522
H
11/2
4
4
D
2
F
5/2
S
3/2
4
4
2
0964
I
11/2
542
652
18519
15337
540
652
I
9/2
4
1
5337
I
9/2
Covalency parameters and nephelauxetic ratio (β)
Β
Δ
0.9991
0.0901
0.9976
0.9972
0.2851
0.9961
0.3891
0.2390

Table 5. Elemental analysis and thermoanalytical results for the lanthanide isonicotinates and Eu nicotinate
Compound formula νOH band (H Content [%]
o
2
O1 ) in color
TG/T range ( C) Mass loss (%) Loss
-
IR spectra [cm ]
yield
I, II, III-stages
C
C
H
H
N
N
Exp.
Calc. Exp.
Calc. Exp.
2.39 8.15
Calc.
[
La(C
Ce(C
Pr(C
Nd(C
5
NH
NH
NH
NH
4
COO)
3
]
-
white
65-70
42.67 42.79 2.29
8.32 I 400-500
II >660
8.30 I 470-580
580
8.00 I 460-595
II > 600
7.21 I 100-190
II 465-600
III > 600
7.60 I 100-210
II 470-570
III > 570
7.84 I 155-205
II 360-455
III >455
8.03 I 470-580
II pon 580
8.00 I 455-560
II >560
7.95 I 430-555
II >555
7.65 I 70-140
II 445-560
58
28.8
65
< 65
65
CO . CO
Pyridine ring
2
[
[
[
5
4
COO)
3
]
-
white
green
violet
70-80
70-75
70-80
42.66 42.69 2.24
41.34 41.60 2.43
36.98 37.11 3.12
2.39 8. 23
2.69 7.98
3.46 7.19
CO
Pyridine ring
CO . CO
Pyridine ring
4H
CO
Pyridine ring
2H
CO
Pyridine ring
2
. CO
>
.
5
4
COO)
3
] H
2
O
3060
3077
2
< 65
87.5
56.4
< 56.4
93.5
62
< 60
96.7
67
< 67
64
< 64
68
< 68
63.9
< 63.9
97.8
62.7
< 62.7
89
75.5
< 73
71.5
< 71.5
66
.
5
4
COO)
3
] 4H
2
O
2
O
2
. CO
.
[Sm(C
5
NH
4
COO)
3
] 2H
2
O
3087
3081
yellow
white
75-85
70-80
38.90 39.12 2.78
40.05 40.31 2.46
2.92 7.56
2.63 7.74
2
O
2
. CO
.
[Eu(C
5
NH
4
COO)
3
] H
2
O
2
H O
CO
Pyridine ring
CO . CO
Pyridine ring
CO . CO
Pyridine ring
CO . CO
Pyridine ring
2
. CO
[
[
[
[
Gd(C
5
NH
4
COO)
3
]
-
white
white
white
pink
65-70
75-80
75-85
65-75
41.12 41.29 2.16
40.89 41.16 2.23
40.78 40.88 2.19
38.97 39.36 2.52
2.31 8.21
2.30 7.98
2.29 7.78
2.57 7.59
2
Tb(C
Dy(C
Ho(C
5
NH
4
COO)
3
]
-
-
2
5
5
NH
4
COO)
COO)
3
3
]
2
.
NH
4
] 1H
2
O
3072
2
H O
2
CO . CO
III > 560
7.88 I 80-430
Pyridine ring
[Er(C
5
NH
4
COO)
3
]
-
pink
70-80
40.07 40.52 2.09
2.27 7.88
CO . CO
Pyridine ring
CO . CO
Pyridine ring
CO . CO
Pyridine ring
CO . CO
Pyridine ring
2
II 440-570
>
650
[Tm(C
[Yb(C
[Lu(C
5
NH
NH
NH
4
COO)
COO)
COO)
3
]
-
-
-
white
white
white
75-80
70-80
65-70
40.57 40.39 2.13
39.89 40.09 2.17
40.02 39.94 2.10
2.26 7.71
2.24 7.34
2.24 7.42
7.85 I 430-555
II > 560
7.79 I 440-580
II > 580
7.86 I 430-560
II >680
2
5
4
3
]
2
< 66
71
<71
5
4
3
]
2

.
[
Eu(C
Nic)
5
NH
4
COO)
3
] 2H
2
O
3066, 3096
white
75-80
39.02 39.00 2.61
2.91
7.59
7.58
I 100-240
II 380-565
III >570
93.8
64
2
H O
(
2
CO . CO
< 64
Pyridine ring

23

24

25

26

27

28

29