Novel Fe (III) heterochelates: Synthesis, structural features and fluorescence studies

Article abstract of DOI:10.1016/j.saa.2009.12.076

Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H₂SB_n) and their Fe (III) heterochelates of the type [Fe(SB_n)(L)(H₂O)]·mH₂O [H₂SB_n = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = -CH₃, m = 4 (H₂SB₁); -C₆H₅, m = 2 (H₂SB₂); -CH₂-CH₃, m = 3 (H₂SB₃); -CH₂-CH₂-CH₃, m = 1.5 (H₂SB₄); -CH₂-C₆H₅, m = 1.5 (H₂SB₅) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (E_a), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported.

Full text of DOI:10.1016/j.saa.2009.12.076

Spectrochimica Acta Part A 75 (2010) 1321–1328
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Novel Fe (III) heterochelates: Synthesis, structural features and
fluorescence studies
C.K. Modia,∗, D.H. Janib, H.S. Patelb, H.M. Pandyaa
a Department of Chemistry, Bhavnagar University, Old Campus, Bhavnagar 364 002, Gujarat, India
b Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar 388 120, Gujarat India
a r t i c l e i n f o
a b s t r a c t
Article history:
Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H2SBn) and their Fe (III)
heterochelates of the type [Fe(SBn)(L)(H2O)]·mH2O [H2SBn = nicotinic acid [1-(3-methyl-5-oxo-1-
phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = –CH3, m = 4 (H2SB1); –C6H5,
m = 2 (H2SB2); –CH2–CH3, m = 3 (H2SB3); –CH2–CH2–CH3, m = 1.5 (H2SB4); –CH2–C6H5, m = 1.5
(H2SB5) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic
acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which
may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons
and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy
of activation (Ea), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have
been reported.
Received 21 July 2009
Received in revised form
19 December 2009
Accepted 31 December 2009
Keywords:
Fe (III) heterochelates
4-Acyl pyrazolone based hydrazides
Quinolone based drug
Fluorescence studies
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
Fluorescent compounds have potential applications as fluores-
cent sensor molecules in their solution for research in biology and
environmental science [1–7]. In the development of new lumines-
cent materials, metal complexes with Schiff base ligands are very
important for their applications.
4-Acyl pyrazolones can form a variety of Schiff bases and are
reported to be superior reagents in biological, clinical and ana-
lytical applications [8] variety of coordination compounds due
to keto–enol tautomerism in them [9]. Compounds containing
hydrazide and acylhydrazone moieties and their complexes also
possess biological activities, especially as potential inhibitors for
many enzymes [10,11].
2.1. Materials
All the chemicals used were of analytical grade and used
without further purification. The compounds 1-phenyl-3-methyl-
2-pyrazoline-5-ol and ␤-picolinic hydrazide were purchased from
E. Merck Ltd. (India). Acyl chlorides were purchased from Quali-
gens Fine Chemicals, India and used without further purification.
Quinolone based drug (HL) was purchased from Bayer AG (Wup-
pertal, Germany).
2.2. Instruments
Previously, we have synthesized a series of 4-acyl pyrazolone
derivatives and their transition metal complexes [12–14]. How-
ever, no information is available on their fluorescence properties.
Hence, in this paper, we report fluorescence properties of some 4-
acyl pyrazolone derivatives and their Fe (III) heterochelates. The
suggested structure of Schiff base ligands (H2SBn) is shown in
Scheme 1.
The fluorescence behaviors of ligands and their Fe (III) hete-
rochelates were studied using a Shimadzu RF-1501 Fluorescence
Spectrophotometer with Xe arc lamp as the light source at room
temperature. The slit width for excitation and emission was 10 nm,
and the scan speed was 1200 nm/min. Elemental analyses (C, H,
N) were carried out on Perkin–Elmer, USA, 2400-II CHN analyzer.
FT-IR spectra were recorded as KBr pellets on Nicolet-400D spec-
trophotometer. 1H NMR spectra were recorded on Advance 400
Bruker FT-NMR instrument in DMSO-d6 solvent. The magnetic
moments were obtained by the Gouy’s method using mercury
tetrathiocyanato cobaltate (II) as a celebrant (g = 16.44 × 10−6 c.g.s.
units at 20 ◦C). The FAB-mass spectrum of the heterochelate was
recorded with JEOL SX-102/DA-6000 mass spectrometer. Simul-
taneous TG/DTGs were obtained by a model 5000/2960 SDT, TA
Instruments, USA. The experiments were performed in N2 atmo-
∗
Corresponding author. Tel.: +91 278 2439852; fax: +91 278 2426706.
E-mail address: chetank.modi1@gmail.com (C.K. Modi).
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.12.076

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C.K. Modi et al. / Spectrochimica Acta Part A 75 (2010) 1321–1328
hydrogen-bonded –OH group. This indicates the involvement of the
5-OH group in intramolecular hydrogen bonding with azomethine
nitrogen. It also suggests that the ligands exist in enol form in the
solid state [15].
The Schiff base ligands (H2SBn) contain five potential donor
sites: (i) the enolic oxygen of the 5-OH group; (ii) the acyclic
azomethine nitrogen; (iii) amide nitrogen of amide–imidol form of
hydrazone moiety and (iv) carbonyl oxygen of amide–imidol form
of hydrazone moiety.
The Schiff base ligands (H2SBn) show a sharp and strong band
due to ꢀ(C
of the acyclic azomethine group at 1630–1640 cm−1
.
N)
The observed low-energy shift of this band in the heterochelates at
1608–1620 cm−1 suggests the coordination of azomethine nitrogen
[16].
The ꢀ(N–H) and ꢀ(C
modes of the lateral chain in the free
O)
Schiff bases appear at 3170–3192 and 1690–1702 cm−1, respec-
tively, indicates that the ligands exist in keto form in solid state.
However, in solution, ligands probably exist in tautomeric enol
form. The infrared spectra of heterochelates show a consider-
Scheme 1. The structure of Schiff base ligands (H2SBn).
sphere at a heating rate of 10 ◦C min−1 in the temperature range
50–800 ◦C, using Al2O3 crucible. DSCs were recorded using DSC
2920, TA Instrument, USA.
able negative shift of 10–15 cm−1 in ꢀ(C
absorption of the
O)
pyrazolone group, indicating a decrease in the stretching force
constant of (C O) as a consequence of coordination through the
oxygen atom of the ligand. Meanwhile, the new absorption band
attributed to ꢀ(C–O) [17] was observed at 1325–1333 cm−1. From
these observations, it is concluded that the ligand reacts in enol
form with prototropy, which incorporates into proton transfer
through oxygen atom of the ligand forming two bonds with the
metal ion.
In the present heterochelates, the bands observed in the
region 3420–3440, 1278–1298, 850–880 and 700–712 cm−1 are
attributed to –OH stretching, bending, rocking and wagging vibra-
tions, respectively due to the presence of water molecules. The
presence of rocking band indicates the coordination nature of the
water molecule [18].
2.3. Synthesis of ligands [H2SBn (where n = 1–5)]: general
procedure
Equimolar (10 mmol) ethanolic solutions (50 mL) of 3-methyl-
1-phenyl-4-acyl-1H-pyrazol-5-one and ␤-picolinic acid hydrazide
(25 mL) were refluxed with stirring for 3 h in round bottom flask.
The resulting solution was cooled overnight at room temperature in
an evaporating dish. The solvent was removed by evaporation and
colored oily product was obtained which was washed with diethyl
ether and dried in vacuo to constant mass and finally purified by
crystallized in appropriate solvents.
2.4. Synthesis of heterochelates
Comparing the main IR frequencies of Fe (III) heterochelates
with that of ciprofloxacin (HL) ligand, the following results were
found. Two very strong absorption peaks in the spectrum of the
ligand were observed at 1707 and 1627 cm−1 due to ꢀ(O–H) of
the carboxylic group and ꢀ(C O) groups, respectively. Absence
of the former band in the spectra of the heterochelates suggests
that this moiety participated in the bonding to the metal ion [19].
The latter band corresponding to ꢀ(C O) shifted to the lower fre-
quency region (∼1620 cm−1) in the spectra of the heterochelates
could be, due to coordination through either the ketone group
or the carboxylic group, to the metal ion. We confirm that the
coordination was through the ketonic group of the HL ligand as
The preparation of heterochelates was carried out by mixing hot
methanolic solution (50 mL) of Fe(NO3)3·9H2O (10 mmol) and a hot
methanolic solution (50 mL) of the Schiff base (H2SBn) (10 mmol)
and HL ligand (10 mmol) in water. The pH was adjusted to 6–7 by
drop wise addition of 25% NaOH solution in water. The mixture
was heated in a water bath for 4 h at 60 ◦C. The mixture was kept
overnight at room temperature. The obtained colored crystals were
washed with water, methanol and finally with diethyl ether and
dried in air.
3. Results and discussion
the antisymmetric ꢀas(COO
−
and symmetric ꢀs(COO modes of the
−
)
)
carboxylate group were observed at 1620 and 1384 cm−1, respec-
The analytical and physical data of the Schiff base ligands
(H2SBn) and their heterochelates are shown in Supplemental Data.
The heterochelates are colored and stable in air. They are insoluble
in water and in most organic solvents but soluble in DMF. The for-
mation of the heterochelates is assumed according to the chemical
reaction as shown below:
tively. The heterochelates produced a ꢁꢀ value of >200 cm−1 in
ꢀas(COO
−
(1595–1588 cm−1) and ꢀs(COO
−
(1380–1370 cm−1) sug-
)
)
gesting unidentate carboxylate coordination to the central metal
ions [12,20–22]. Accordingly ciprofloxacin (HL), in the isolated
heterochelates appears to act as a uninegative bidentate ligand
through the oxygen atom of the carbonyl group and enolic oxygen
of the carboxylate group.
Fe(NO3)3·9H2O + H2SBn + HL
In the far-IR region, two new bands at 455–465 and
410–420 cm−1 in the heterochelates are assigned to ꢀ(M–O) pyra-
zolone and ꢀ(M–N) modes, respectively. All of these data confirm the
fact that H2SBn behaves as a dinegative tridentate ligand forming
a conjugated chelate ring, with the ligand existing in the hete-
rochelates in the enolized form.
→ [Fe(SBn)(L)H2O]·mH2O + (9 − m)H2O + 3HNO3
(where n = 1, m = 4; n = 2, m = 2; n = 3, m = 3; n = 4 and 5, m = 1.5)
3.1. IR spectra of H2SBn and their heterochelates
The important infrared spectral bands and their tentative
assignments for the synthesized ligands and their heterochelates
were recorded as KBr disks. The Schiff base ligands H2SBn (where
n = 1–5) in the present investigation exhibit a broad band cen-
tered at 3372–3395 cm−1. This suggests the presence of a strongly
3.2. 1H NMR spectra of H2SBn and their heterochelates
The tautomerism of pyrazolones is an old problem of pyrazole
chemistry and thus it has been the subject of a considerable num-

C.K. Modi et al. / Spectrochimica Acta Part A 75 (2010) 1321–1328
1323
ber of studies [23–28]. The 1H NMR studies of Schiff base ligands
(H2SBn) (where n = 1–5) and their heterochelates were carried out
in DMSO-d6 at room temperature. A broad singlet corresponding to
one proton for Schiff base ligands (H2SBn) is observed in the range ı
11.9–12.7 ppm. This signal disappeared when D2O exchange exper-
iment was carried out. It shows the enolic nature of ligand and
broadness of singlet due to fast exchange interaction of proton
via keto–enol tautomerism with nitrogen of the azomethine group
[29]. It may be noted that the integration of this signal perfectly
matches with one proton and there is no other fragment(s) of this
signal, which suggests that only one tautomeric form of the Schiff
base ligands exists in solution under the experimental conditions.
Comparing with the solid state study, we prefer to assign this signal
to OH; however, assignment of this peak to NH cannot be ruled out
provided solid state structural evidence is not considered.
In the 1H NMR spectra of Schiff bases (H2SBn), the pyridine
ring (C5H4N) protons appeared as multiplet in the region of ı
7.98–9.10 ppm [31,32], which remain unaltered in the spectra of
heterochelates suggesting non-involvement of this group in coor-
dination.
3.3. Mass spectra
The representative mass spectrum of the Schiff base H2SB2 lig-
and is shown in Supplemental Data. The molecular ion peak was
observed at m/e 397 (Calcd. 397.15). A weak peak at m/e 277 (Calcd.
276.11) is due to the formation of (C17H14N3O)+, with the elimi-
nation of one –NH group and (C6H4NO)+ m/e 106 (Calcd. 106.03)
ion from the molecule. The species further degrade with the loss
of one –CH3 group forming (C16H11N3O)+ with peak at m/e 261
(Calcd. 261.09). Prominent peaks for (C6H5N)+ and (C6H5)+ ions are
observed at m/e 91 and 77, respectively.
The recorded mass spectra (Fig. 1) and the molecular ion peak for
the heterochelate [Fe(SB1)(L)(H2O)]·4H2O have been used to con-
firm the molecular formulae. The first peak at m/e 736 represents
the molecular ion peak of the heterochelate. The fragmentation
pattern is given in Scheme 2. The primary fragmentation of the
heterochelate takes place due to the loss of –CH3 group from
the species (a) to give species (b) with peak at m/e 723. The
species (b) further degrades with the subsequent loss of one
coordinated water molecule and –C3H5 species forming species
(c) with their peak at m/e 662. The sharp peak (base peak)
observed at m/e 390 represents the stable species (g) with 99.6%
abundance.
In the aromatic region, specifically for H2SB2 ligand, phenyl
protons of the benzoyl group indicate the typical effect on their
chemical shifts, whose signals are observed in the down field region
from the benzene standard (ı = 7.01–7.58) in the order of ortho-
, para-, and meta-positions (ꢁı = positive o ꢀ p > m) characteristic
for a monosubstituted benzene bonded to the electrophylic >C
N
group (chemical shift values (ı) o: 7.83, m: 7.64 and p: 7.60 ppm
of Ph-ring protons of 4-benzoyl group). On the other hand, phenyl
protons bonded to the N atom of the pyrazolone ring show a net
effect of the diamagnetic ring current on the pyrazolone ring and
the electron-donating property of the >N–N group (chemical shift
values (ı) o: 7.58, m: 7.26 and p: 7.11 ppm of Ph-ring protons of
pyrazolone group). Both of these effects further increase aromatic-
ity of the pyrazolone ring due to the electron delocalization on
the ring system. It should be noted that the ring current effect
is a down field shift (ꢁı = positive o ꢀ p > m), while the electron-
donating effect is an up field shift (ꢁı = negative m ꢀ p > o) [30].
Probably, the ring current effect is much greater than the electron-
donating one, and thus we get the order of chemical shift values (ı)
o: 7.62, m: 7.20 and p: 7.04 for the heterochelates.
3.4. Fluorescence spectra of ligands [H2SBn] (where n = 1–5) and
its heterochelates
The liquid-state fluorescence emission spectra of the ligands
(H2SBn) and its heterochelates were measured in N,N-dimethyl
formamide (DMF) with a concentration of 1 × 10−5 M at room tem-
perature. The fluorescence emission spectra of ligands (H2SBn)
and their heterochelates are displayed in Figs. 2 and 3, respec-
tively. Obviously, upon excitation at ꢂmax,ex = 550 nm, all the ligands
[H2SBn] (where n = 1–5) exhibit fluorescent properties in the green
It was found that the signal of the –NH proton of the lateral
chain of Schiff bases (H2SBn) disappeared in the spectra of hete-
rochelates, presumably because of enolization and subsequent loss
of –NH proton by coordination with the metal ion through carbonyl
oxygen.
Fig. 1. The typical FAB-mass spectrum of a heterochelate [Fe(SB1)(L)(H2O)]·4H2O.

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C.K. Modi et al. / Spectrochimica Acta Part A 75 (2010) 1321–1328
region at room temperature, and the maximum emission peaks are
at 615, 620, 620, 625 and 700 nm, respectively. There are slight
red shifts of the emission energies of the five ligands. Moreover,
the fluorescence emission intensities depend upon the introduction
of different substitutions in the ligand molecules. Electro-donating
groups (propyl, ethyl and methyl) and electro-withdrawing groups
(phenyl, benzyl) on the 4-position of the pyrazolone ring can
drastically alter the electron density and the electron conjugate
system of the ligands H2SBn [33,34]. However, when the het-
erochelates are excited at the same wavelength, the spectra of
the heterochelates [Fe(SBn)(L)(H2O)]·mH2O (where n = 1–5) have
a slightly red shift as compared to the ligands as shown in Fig. 3,
which probably was led by the charge transfer that was caused
by the alternation of the structure of the ligand during the formu-
Scheme 2. The suggested fragmentation pattern of [Fe(SB1)(L)H2O]·4H2O.

C.K. Modi et al. / Spectrochimica Acta Part A 75 (2010) 1321–1328
1325
Scheme 2. (Continued ).
lation of heterochelate. The maximum emission of heterochelate
3.5. Electronic spectra and magnetic moments
[Fe(SB4)(L)(H2O)]·1.5H2O is at 455 nm in the blue region, while
those of [Fe(SB5)(L)(H2O)]·1.5H2O heterochelate with maximum
emission band at 800 nm in the red region. Except for the emis-
sion intensity, the shapes of the emission spectra of ligands H2SBn
and their heterochelates are similar, so the emission properties of
heterochelates are believed to originated from ␲* → ␲ transitions
in the ligands. The significant red shift of the fluorescence spectra of
the heterochelates compared to ligands may be due to the chelating
of the ligand to the Fe (III) ion, which enhances the ligands ability
to accept electrons and decreases the electron transition energy
[35].
The information regarding geometry of the heterochelates was
obtained from their electronic spectral data and magnetic moment
values. In the present work, electronic spectra of heterochelates
exhibit two bands at around ∼20,000 and ∼32,500 cm−1 are
6
4
assigned to the A1g → T2g and MLCT transitions, respectively in
the d5-system of the Fe (III) atom. From the electronic spectra, an
octahedral geometry around the central metal ion is suggested.
This is further supported by the magnetic measurement data
of Fe (III) heterochelates which falls in the range 5.90–6.01 B.M.
[36,37].

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C.K. Modi et al. / Spectrochimica Acta Part A 75 (2010) 1321–1328
Fig. 4. The typical Freeman–Carroll plot for thermal degradation of a heterochelate
[Fe(SB4)(L)(H2O)]·1.5H2O.
Fig. 2. Fluorescence spectra of ligands [H2SBn] (where n = 1–5) in 10−5 M DMF solu-
tion at room temperature.
(where n = 1, m = 4; n = 3, m = 3; n = 4, m = 1.5)
◦
C
110−–→220
[Fe(SBn)(L)] + H2O
3.6. Thermal studies
[Fe(SBn)(L)H2O]
removal of coordinated water molecule
◦
C
[Fe(SBn)(L)] 220−–→350
[Fe(SBn)]
Each decomposition process follows the trend
removal of HL ligand
heat
◦
C
350−–→800
Fe2O3
Solid-1−→ Solid-2 + Gas
[Fe(SBn)]
removal of H SB ligand
n
2
This process comprises of several stages. The method reported
by Freeman–Carroll method [38] has been adopted. Plots of
[ꢁlog(dw/dt)/ꢁ log wr] vs. [ꢁ(1/T)/ꢁ log wr] were linear for all
of the decomposition steps. The energy of activation Ea was cal-
culated from the slopes of these plots for a particular stage and
the order of reactions (n) determined from the intercept, showing
first order reaction over the entire range of decomposition for all of
the heterochelates. A typical Freeman–Carroll plot for the thermal
degradation of [Fe(SB4)(L)H2O]·1.5H2O is shown in Fig. 4.
Whereas the thermal fragmentation scheme for heterochelates
[Fe(SBn)(L)(H2O)]·mH2O (where n = 2, m = 2; n = 4, m = 1.5) is given
below:
[Fe(SBn)(L)H2O] · mH2O
◦
50–215
C
−→
removal of crystalline water molecules+one coordinated water molecule
[Fe(SBn)(L)] + H2O + mH2O
(where n = 2, m = 2; n = 5, m = 1.5)
3.6.1. The thermal behavior of heterochelates
◦
The thermal fragmentation scheme for heterochelates
[Fe(SBn)(L)(H2O)]·mH2O is as shown below:
C
[Fe(SBn)(L)] 215−–→350
[Fe(SBn)]
removal of HL ligand
◦
[Fe(SBn)(L)H2O] · mH2O
[Fe(SBn)]
350−–→800
Fe2O3
C
removal of H SB ligand
n
2
◦
50–110
C
−→
[Fe(SBn)(L)H2O] + mH2O
The anhydrous heterochelates show great thermal stability up
to 220 ◦C; and in the third subsequent stage for heterochelates, the
decomposition and combustion of ligand (HL) occurs. The fourth
subsequent stage for heterochelates shows the decomposition and
combustion of ligand (H2SBn). The removal of ligand (H2SBn) under-
goes decomposition forming Fe2O3 as the final residue.
removal of crystalline water molecules
The thermodynamic activation parameters of the decompo-
sition process of dehydrated heterochelates such as activation
entropy (S*), pre-exponential factor (A), activation enthalpy (H*)
and free energy of activation (G*), were calculated using the
reported equations [39] and are tabulated in Table 1. According to
the kinetic data obtained from DTG curves, all the heterochelates
have negative entropy, which indicates that the studied hete-
rochelates have more ordered systems than reactants [40]. The
kinetic parameters, especially energy of activation (Ea) is helpful
in assigning the strength of the bonding of ligand moieties with
the metal ion. The calculated Ea values of the investigated hete-
rochelates for the degradation stage of ligand (HL) are in the range
25.25–32.54 kJ mol−1. The relative high Ea value indicates that the
ligand (HL) is strongly bonded to the metal ion [41]. From the above
discussion an octahedral geometry of the heterochelates can ten-
tatively be assumed as shown in Fig. 5.
Fig. 3. Fluorescence spectra of heterochelates [Fe(SBn)(L)(H2O)]·mH2O (where
n = 1–5) in 10−5 M DMF solution at room temperature.

C.K. Modi et al. / Spectrochimica Acta Part A 75 (2010) 1321–1328
1327
Table 1
Kinetic parameters of heterochelates.
Compounds
TG range (◦C)
Ea (kJ mol−1
)
n
A (s−1
)
S* (J K−1 mol−1
)
H* (kJ mol−1
)
G* (kJ mol−1
)
[Fe(SB1)(L)(H2O)]·4H2O
50–110
110–200
200–340
340–800
50–215
215–330
330–800
50–115
115–200
200–340
340–800
50–90
12.55
14.36
25.25
38.32
14.73
27.67
43.52
10.28
17.22
30.69
33.84
9.21
14.09
25.52
33.79
15.20
32.54
41.31
0.98
0.98
0.99
1.00
0.99
1.00
1.00
1.00
1.00
0.99
0.98
1.01
0.98
1.00
1.01
1.00
0.99
1.01
0.97
1.22
3.97
5.25
1.18
2.34
5.45
0.32
19.66
22.42
33.55
0.11
0.13
4.33
8.38
0.10
2.20
33.55
−100.98
−100.22
−99.73
−98.66
−102.09
−99.00
−98.14
−103.46
−100.30
−96.93
−95.22
−102.53
−101.51
−97.31
−96.22
−102.52
−98.56
−95.44
9.66
10.01
11.03
28.31
9.96
20.62
30.31
5.52
43.69
61.66
73.55
97.90
32.77
66.69
103.85
43.41
62.99
70.61
90.33
34.59
58.63
78.45
107.04
35.54
62.40
93.49
[Fe(SB2)(L)(H2O)]·2H2O
[Fe(SB3)(L)(H2O)]·3H2O
7.42
15.77
25.10
0.45
[Fe(SB4)(L)(H2O)]·1.5H2O
[Fe(SB5)(L)(H2O)]·1.5H2O
90–220
2.49
220–450
450–800
50–210
210–350
350–800
11.51
26.95
0.47
10.85
22.43
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.saa.2009.12.076.
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