The synthesis and characterization of [M(salen/salophen/saldeta)] [M=Cr(III), Mn(III) or Fe(III)] capped s-triazine cored tripodal trinuclear Schiff bases complexes

Article abstract of DOI:10.1007/s10847-018-0844-7

Abstract: Ligand complexes ([M(salen/salophen)]₂O, [M(saldeta)]Cl shortened as LC, M=Cr(III), Mn(III) or Fe(III)), have been synthesized. 2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (3) was synthesized with the reaction of p-hydroxybenzaldehyde

Full text of DOI:10.1007/s10847-018-0844-7

Journal of Inclusion Phenomena and Macrocyclic Chemistry
https://doi.org/10.1007/s10847-018-0844-7
ORIGINAL ARTICLE
The synthesis and characterization of [M(salen/salophen/saldeta)]
[M=Cr(III), Mn(III) or Fe(III)] capped s-triazine cored tripodal trinuclear
Schiff bases complexes
Berkman İşçi1 · Şaban Uysal1
Received: 11 July 2018 / Accepted: 19 September 2018
© Springer Nature B.V. 2018
Abstract
Ligand complexes ([M(salen/salophen)]2O, [M(saldeta)]Cl shortened as LC, M=Cr(III), Mn(III) or Fe(III)), have been
synthesized. 2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (3) was synthesized with the reaction of p-hydroxybenzaldehyde
(2) and cyanuric chloride (1). 2,4,6-tris(4-(4′-carboxyphenylimino)phenoxy)-1,3,5-triazine (5) was synthesized with the
reaction of 2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (3) and 4-aminobenzoic acid (4). 2,4,6-tris(4-(4-carboxyphenylimino)
phenoxy)-1,3,5-triazine was treated with SOCl2 in CH3CN, and 2,4,6-tris(4-(4′-chloroformylphenylimino)phenoxy)-1,3,5-
triazine (6) was obtained. 2,4,6-tris(4-(4′-chloroformylphenylimino)phenoxy)-1,3,5-triazine was reacted with 4-aminobenzoic
acid or 4-hydroxbenzoic acid in CH3CN, and 2,4,6-tris(4-(4′-(4′′-carboxyphenylamido)phenylimino)phenoxy)-1,3,5-triazine
(8) and 2,4,6-tris(4-(4′-(4′′-carboxyphenylformato)phenylimino)phenoxy)-1,3,5-triazine (9) were obtained. s-Triazine cored
tripodal trinuclear Schiff bases complexes were synthesized with the reaction of 8 and/or 9 and ligand complexes. The
complexes have been characterized as low-spin (S=1/2) distorted octahedral Fe(III)Salen/Salophen, low-spin (S=1) dis-
torted octahedral Mn(III)Salen/Salophen, high-spin (S=5/2) distorted octahedral Fe(III)Saldeta, high-spin (S=2) distorted
octahedral Mn(III)Saldeta and (S=3/2) distorted octahedral Cr(III)Salen/Salophen/Saldeta bridged by COO− groups. The
structure of all ligand and complexes were identified by using elemental analysis, thermal analyses (TGA-DTG), magnetic
susceptibility, ESI-MS, ICP–AES, UV–Vis, 1H-NMR, 13C-NMR and FT-IR spectral data.
* Şaban Uysal
sabanuysal@karabuk.edu.tr
1
Department of Chemistry, Faculty of Sciences, Karabuk
University, 78050 Campus of Demir-Celik, Karabuk, Turkey
Vol.:(0123456789)
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Journal of Inclusion Phenomena and Macrocyclic Chemistry
Graphical abstract
Keywords Cyanuric chloride · Salen · Salophen · Saldeta · Tripodal trinuclear complexes
In recent years, the widespread use of Schiff bases and
Introduction
metal complexes, especially in various qualitative and quan-
titative analyzes, enrichment of radioactive materials [10],
pharmaceutical industry [28, 29], the paint industry [11] and
plastics industry has further increased, and it has attracted
much attention due to their biochemical activities [28, 29],
especially the synthesis of many Schiff bases which can be
used in liquid crystal technology.
All of the s-triazine derivatives that have wide practical
applications are 2,4,6-mono, di- or tri-substituted, symmet-
rical and nonsymmetrical compounds are bearing different
substituents [1]. The most important reagent of obtained
these compounds is cyanuric chloride, owing to the reactiv-
ity of its chlorine atoms toward nucleophiles [1, 2]. Due to
the advantage of the temperature-dependent stepwise sub-
stitution of its three chlorine atoms by different nucleophiles
[3], cyanuric chloride has been proved to be a very useful
template for the synthesis of dendrimers, macrocycles, calix-
arene, supramolecular and combinatorial libraries [1, 4–8].
It is known that tripodal s-triazine cored Schiff base com-
plexes are used in medicine, plastic and polymer industry,
chemotherapeutic treatment of various cancer derivatives
[9], paper industry, as reactive dye [10, 11], textile indus-
try [12, 13], cleaning waste water [14], production of ion
exchange resins [14]. Examination of metal organic com-
plexes is one of the most active areas in material science and
chemical research. The interesting properties of these mate-
rials and their potential use in various applications including
electrical conductivity [15, 16], magnetism, ion exchange
[17, 18], catalysis [19–22], nonlinear optics [23–27], etc.
have witnessed significant developments in the fields.
Over the years, Schiff bases have played an important
role as chelating ligands for large-scale metal ions. Recently,
more attention has been paid to the Schiff base complexes
of metals in order to understand the complex biochemical
reactions [28].
Our ongoing research deals with also the design of new
ligands and ligand-complexes which can serve as efficient
chelating agents towards metal cations of a different nature.
In our previous studies, we have also synthesized and
characterized tripodal [M(salen/salophen)] capped mela-
mine based trinuclear complexes [2, 29–33], tetra-armed
[M(salen/salophen)] capped thiosemicarbazone [34], and
dendrimeric complexes [35, 36].
In the literature, the behavior of tripodal Schiff base
complexes in the magnetic field has not been discussed
in detail. With this study, we wish to compensate this
shortcoming in the literature. It is expected that tripodal
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Journal of Inclusion Phenomena and Macrocyclic Chemistry
polymers will be resistant to high pressure and temper-
ature, chemical degradation. Thus, it is expected to be
used in industrial applications, especially in the ceramics
industry and as enamel material in future years.
Materials and methods
Melting points were measured using a Buchi SMP-20 melt-
ing point apparatus. Elemental analyses (C, H, N) were
determined using a Leco, CHNS-932 model analyzer.
In this work, we synthesize paramagnetic dendrim-
eric complexes which are sensitive to magnetic field and
resistant to heat and corrosion. Hydrogels sensitive to the
magnetic field can swell and shrink under the influence of
the magnetic field. The swelling and shrinkage behavior
of such polymers is used in controlled release and artifi-
cial muscle applications of drugs [9]. For the synthesis of
new tripodal Schiff base ligands, cyanuric chloride was
used as the starting material. Salen, salophen and saldeta
capped complex structures were synthesized and their
thermal and magnetic behavior were investigated. Dur-
ing the reaction, we connected substituents containing the
COO group to the cyanuric chloride step by step. Tripo-
dal dendrimeric complexes were obtained by interacting
with tripodal polymers and starting complexes [M(salen/
salophen/saldeta)].
1
The H-NMR spectra were recorded on a Bruker DPX-
400 400 MHz high performance digital NMR and Agilent
Annual Refill (400 MHz), FT-IR spectra on a Thermo SCI-
ENTIFIC NICOLET İS5 FT-IR spectrometer with İD5 ATR
apparatus (4000–440 cm−1). The thermal analyses were per-
formed on a Shimadzu DTA 50 and TG 50 H models using
10 mg samples. The DTA and TG curves were obtained at
a heating rate of 10 °C min−1. In all cases, the 50–700 °C
temperature range was studied under dry N2 atmosphere.
Magnetic susceptibilities of metal samples were determined
using a Sheerwood Scientific MX Gouy magnetic suscep-
tibility apparatus and magnetic measurements were carried
out using the Gouy method with Hg[Co(SCN)4] as calibrant.
The effective magnetic moments, µeff, per metal atom were
√
calculated from the expression: ꢀeff = 2.84 ꢁMT B.M.,
where χM is the molar susceptibility. The metal contents of
each complex were determined on a Varian, Vista AX CCD
Simultaneous model AES spectrophotometer.
Experimental
Reagents and solvents
Synthesis methods of the chemicals
Cyanuric chloride (1), p-hydroxybenzaldehyde,
p-aminobenzoic acid, p-hydroxybenzoic acid and all
solvents were purchased from Sigma. 2,4,6-tris(4-
formylphenoxy)-1,3,5-triazine (3), Ligand Complexes
([Cr/Mn/Fe(salen)]2O LC1 [37], [Cr/Mn/Fe(salophen)]2O
LC2 [37], [Cr/Mn/Fe(saldeta)Cl] LC3 [38]) were synthe-
sized according to the procedures described in the litera-
ture (Fig. 1).
Synthesis of 2,4,6‑tris(4‑(4′‑carboxyphenylimino)
phenoxy)‑1,3,5‑triazine [Trp(PABA)3] (5)
Solid K2CO3 (6 mmol 1.04 g and 25% excess) was added to a
solution of 4-aminobenzoic acid (3 mmol, 0.51 g) in 50 mL
AcOEt with stirring. After the solution of 2,4,6-tris(4-
formylphenoxy)-1,3,5-triazine “TRIPOD” (0.44 g, 1 mmol)
in 20 mL AcOEt was added dropwise with stirring. The mix-
ture was boiled under reflux for 20 h and cooled to room
Fig. 1 The structures of ligand complexes (M=Cr(III), Mn(III) or Fe(III))
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Journal of Inclusion Phenomena and Macrocyclic Chemistry
temperature. The solid precipitate was filtered and dissolved
in water. Then, 0.1 M HCl was added to solution until pH
6,50. The solid white fragment was filtered, the yellow liq-
uid solution was completely evaporated. The remaining dark
yellow crude product was dissolved in methanol. Insoluble
KCl was discarded and the solvent was completely removed,
then recrystallized with EtOH and dried in a vacuum cabinet
[32] (Scheme 1).
The synthesis procedure for [M(Salen/Salophen/
Saldeta)] capped complexes of 8 and 9 (M=Cr(III),
Mn(III) and Fe(III))
2,4,6-tris(4-(4′-(4′′-carboxyphenylamido)phenylimino)
phenoxy)-1,3,5-triazine (8) (2.32 g, 2.00 mmol) or
2,4,6-tris(4-(4′-(4′′-carboxyphenylformato)phenylimino)
phenoxy)-1,3,5-triazine (9) (2.32 g, 2.00 mmol) were dis-
solved in 20 mL of absolute methanol. And, a suspension of
[LC1/LC2/LC3 3.00/3.00/6.00 mmol] in 20 mL of absolute
methanol were added, and then the mixture was stirred at
85 °C under reflux for a 2 h period. A distinct change in
color and a decrease in pH (~2.5) were observed. While an
equivalent amount of methanol solution of NaOH (0.1 M)
was added dropwise to adjust the pH value to about 5.5,
the mixture was stirred and heated to 60 °C on a water bath
for 2 h. The solid product was cooled to room temperature
and filtered. The precipitated complexes were washed with
water, ethanol and diethylether and dried in a vacuum cabi-
net (Scheme 2).
Synthesis of 2,4,6‑tris(4‑(4′′‑chlorocarbonylphenyli
mino)phenoxy)‑1,3,5‑triazine [Trp(PABA)3Cl3]
1.20 mL SOCl2 in 10 mL CH3CN was added to solution of
2,4,6-tris(4-(4-carboxyphenylimino)phenoxy)-1,3,5-triazine
(3.99 g, 5.00 mmol) in 30 mL of CH3CN and stirred for 4 h
at 85 °C. The solid yellow product was filtered and washed
with diethylether, and then dried in a vacuum cabinet. The
products were purified by using column chromatography
(ethylacetate/n-hexane - 1/6 v/v) (Scheme 1).
The characteristic FT-IR bands (cm−1
) of
The characteristic FT-IR bands (cm−1) of complexes
(10–27);
[Trp(PABA)3Cl3] (6): C=N: 1609, 1594; C=O: 1703; C–H:
3036, 3007, 2888; CphO: 1306; C–N: 1111; C–Car: 1544,
1507, 1427.
[Trp(PABA)6(CrSalen)3] (10): C=N: 1599, 1613;
C=O: 1678; N–H: 3300 (Broad), 2894, 2833; C–H: 3100
(Broad); CphO: 1315, 1285; C–N: 1401 (amid), 1179, 1151;
C–Car: 1529, 1464; [Trp(PABA)6(CrSalophen)3] (11):
C=N: 1603; C=O: 1735, 1680; N–H: 3312 (Broad); C–H:
3100 (Broad), 2886, 2832; CphO: 1309, 1285; C–N: 1402
(amid), 1180, 1151; C–Car: 1530, 1513; [Trp(PABA)6(CrS
aldeta)3] (12): C=N: 1597, 1573; C=O: 1679; N–H: 3420
(amid), 3334, 3211; C–H: 3061, 2828; CphO: 1304, 1279;
C–N: 1404 (amid), 1178; C–Car: 1530, 1495; [Trp(PABA
)6(MnSalen)3] (13): C=N: 1620, 1599, 1542; C=O: 1678;
N–H: 3339; C–H: 3054, 2890, 2833; CphO: 1286; C–N:
1152, 1129; C–Car: 1422 (Broad); [Trp(PABA)6(MnSalo
phen)3] (14): C=N: 1622, 1597, 1557; C=O: 1679; N–H:
3413; C–H: 3060, 2892; CphO: 1241; C–N: 1370 (amid),
1126; C–Car: 1496, 1476, 1459, 1423; [Trp(PABA)6(MnS
aldeta)3] (15): C=N:1620, 1597, 1568; C=O: 1685,1677;
COO: 1385; N–H: 3345, 3205; C–H: 3011, 2884, 2832;
CphO: 1318; C–N: 1424, 1364; C–Car: 1541, 1467; [Trp(PA
BA)6(FeSalen)3] (16): C=N: 1627, 1597, 1557; C=O: 1679,
1642; COO: 1385; N–H: 3325; C–H: 3054, 2901; CphO:
1324; C–N: 1423, 1303, 1267; C–Car: 1544, 1470; [Trp(P
ABA)6(FeSalophen)3] (17): C=N: 1602, 1577, 1532; C=O:
1698, 1675; COO: 1377; N–H: 3357; C–H: 3017, 2889;
CphO: 1311; C–N: 1430, 1290, 1265; C–Car: 1490, 1461;
[Trp(PABA)6(FeSaldeta)3] (18): C=N: 1627, 1597, 1541;
C=O: 1683, 1641; N–H: 3359, 3257; C–H: 3052, 3023,
2964, 2919, 2896, 2868; CphO: 1330; C–N: 1430, 1379;
C–Car: 1470, 1446; [Trp(PABA)3(PHBA)3(CrSalen)3] (19):
C=N: 1623, 1602, 1565; C=O: 1682; COO: 1412; C–H:
3025, 2945, 2880; CphO: 1338, 1276; COC: 1243, 1122;
The synthesis of 2,4,6‑tris(4‑(4′′‑(4′′′‑carboxyphen
ylamido)phenylimino)phenoxy)‑1,3,5‑triazine (8)
and 2,4,6‑tris(4‑(4′′‑(4′′‑carboxyphenylformato)
phenylimino)phenoxy)‑1,3,5‑triazine (9)
2,4,6-tris(4-(4′-chloroformylphenylimino)phenoxy)-1,3,5-
triazine (1.71 g, 2.00 mmol) and AlCl3 (0.80 g, 6.00 mmol)
in 40 mL CH3CN were stirred for 1 h under reflux at 50 0C,
then a solution of 4-aminobenzoic acid (0.82 g, 6.00 mmol)
or 4-hydroxybenzoic acid (0.83 g, 6.00 mmol) in 20 mL
CH3CN was added to the suspension. This mixture was
stirred under reflux at 65 °C for 4–5 h at and cooled to room
temperature. The solid light yellow product was filtered and
washed with diethylether, and then dried in a vacuum cabi-
net. The products were purified by using column chromatog-
raphy (ethylacetate/n-hexane - 1/4 v/v) (Scheme 1).
The characteristic FT-IR bands (cm−1) of 8 and 9;
[Trp(PABA)6] (8): C=N: 1609, 1596; C=O: 1703; COO:
1398; N–H: 3413; C–H: 3036, 3009, 2889; CphO: 1317,
1247; C–N: 1398, 1135, 1111; C–Car: 1546, 1506, 1427;
[Trp(PABA)3(PHBA)3] (9): C=N: 1608, 1575; C=O: 1703;
COO: 1399; C–H:3032, 2942, 2886; COC: 1246, 110; C–N:
1176; C–Car: 1556, 1507, 1426.
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Journal of Inclusion Phenomena and Macrocyclic Chemistry
Scheme 1 The synthesis route of ligands
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Scheme 2 The synthesis route of the all complexes
C–N: 1136; C–Car: 1551, 1490, 1465; [Trp(PABA)3(PHB
A)3(CrSalophen)3] (20): C=N: 1623, 1602, 1565; C=O:
1685; COO: 1415; C–H: 3049, 2816; CphO: 1336, 1275;
COC; 1256, 1126; C–N:; 1133; C–Car: 1540, 1485, 1462;
Trp(PABA)3(PHBA)3(CrSaldeta)3 (21): C=N: 1597, 1529;
C=O: 1680; COO: 1408; N–H: 3365 (Broad); C–H: 3059,
2825; CphO: 1332, 1280; COC:1278; C–N: 1129; C–Car:
1495, 1465; Trp(PABA)3(PHBA)3(MnSalen)3 (22): C=N:
1620, 1597, 1568; C=O: 1677; COO: 1424; C–H: 3057,
2833; CphO: 1332, 1281; COC: 1127; C–N: 1030; C–Car:
1541, 1493, 1467; Trp(PABA)3(PHBA)3(MnSalophen)3
(23): C=N: 1612, 1585, 1543; C=O: 1679; COO:
1420; C–H: 3015, 2828; CphO: 1342, 1282; COC:
1245, 1122; C–N: 1145; C–Car: 1536, 1490, 1472;
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Journal of Inclusion Phenomena and Macrocyclic Chemistry
Trp(PABA)3(PHBA)3(MnSaldeta)3 (24): C=N: 1618, 1576,
1555; C=O: 1680; COO: 1418; N–H: 3372; C–H: 3060,
2810; CphO: 1329, 1285; COC: 1256, 1128; C–N: 1140;
C–Car: 1529, 1476, 1469; Trp(PABA)3(PHBA)3(FeSalen)3
(25): C=N: 1625, 1597; C=O: 1682, 1652; COO:
1421; C–H: 3050, 3025, 2949; CphO: 1324; COC:
1243, 1125; C–N: 1146; C–Car: 1556, 1543, 1470;
Trp(PABA)3(PHBA)3(FeSalophen)3 (26): C=N: 1601,
1575, 1533; C=O: 1681; COO: 1377; C–H: 3063, 2950,
2830; CphO: 1311; COC: 1253, 1126; C–N: 1143; C–Car:
1491,1460, 1429; Trp(PABA)3(PHBA)3(FeSaldeta)3 (27):
C=N: 1608, 1577, 1530; C=O: 1682; COO: 1422; N–H:
3375; C–H: 3045, 2829; CphO: 1325, 1288; COC: 1246,
1124; C–N: 1147; C–Car: 1515, 1490, 1462.
spectra of the Trp(PABA)3Cl3 we originally synthesized are
analyzed, the singlet at 9.25 ppm corresponding to three
protons are attributed to CH hydrogen of azomethine group
(C6-H), and the dublet at 8.05 ppm corresponding to six
protons, the dublet at 7.82 ppm corresponding to six pro-
tons, the dublet at 7.20 ppm corresponding to six protons
and the dublet at 7.11 ppm corresponding to six protons are
attributed to aromatic CH hydrogens. When the 13C NMR
spectrum is examined for Trp(PABA)3Cl3, carbon peaks are
encountered at 178.753 ppm for C1, 167,293 ppm for C11,
159.110 ppm for C6, 158.850 ppm for C7, 157.530 ppm for
C2, 145.750 ppm for C4, 143.237 ppm for C5, 131.508 ppm
for C10, 131.286 ppm for C9, 125.522 ppm for C8 and
124.005 ppm for C3. These recorded 13C and 1H resonances
are consistent with the literature [40] (Fig. 2).
When the 1H NMR spectrum of the Trp(PABA)6 we orig-
inally synthesized are analyzed, the dublet at 9.19 ppm cor-
responding to three protons are attributed to CH hydrogen of
azomethine group (C6-H), and the dublet at 8.38 ppm corre-
sponding to six protons, the dublet at 7.88 ppm correspond-
ing to six protons, the dublet at 7.75 ppm corresponding to
six protons and the dublet at 7.35 ppm corresponding to six
protons, the dublet at 7.27 ppm corresponding to six protons
and the dublet at 6.76 ppm corresponding to six protons are
attributed to aromatic CH hydrogens. The broadly observed
value, corresponding to 3 protons at 5.01 ppm, is attrib-
uted to the amide group. The broad observation is due to
intramolecular H-bonding. When the 13C NMR spectrum is
examined for Trp(PABA)6, carbon peaks are encountered at
180.900 ppm for C1, 167.938 ppm for C16, 166.101 ppm for
C11, 164.056 ppm for C6, 159.002 ppm for C2, 158.002 ppm
for C7, 142.001 ppm for C12, 131.065 ppm for C10,
130.150 ppm for C14, 129.900 ppm for C4, 128.506 ppm for
C5, 126.903 ppm for C9, 125.426 ppm for C15, 122.998 ppm
for C8, 121.755 ppm for C13, 119.812 ppm for C3. These
recorded 13C and 1H resonances are consistent with the lit-
erature [2, 8, 30–36, 40] (Fig. 3).
Results and discussion
In the first section of the study, the target ligands 8 and 9
were synthesized in a four-step from cyanuric chloride in
high yield 92 and 82%, respectively. The structures of 3 and
5 had been identified in the literature [32, 39]. 2,4,6-tris(4-
(4′-chloroformylphenylimino)phenoxy)-1,3,5-triazine (6)
was prepared by reacting 5 with SOCl2. Then, 2,4,6-tris(4-
(4′-(4′′-carboxyphenylamido)phenylimino)phenoxy)-1,3,5-
triazine (8) and 2,4,6-tris(4-(4′-(4′′-carboxyphenylformato)
phenylimino)phenoxy)-1,3,5-triazine (9) were prepared by
reacting 6 with 4-aminobenzoic acid or 4-hydroxybenzoic
acid, respectively (Scheme 1). The ligands are soluble in
many organic solvents, such as acetone, chloroform, ethanol,
ethylacetate, DMSO and DMF.
[Cr/Mn/Fe(Salen)/(Salophen)]2O and [Cr/Mn/
Fe(Saldeta)]Cl were used as “ligand complexes (LC)” in our
study because they could coordinate to the other ligand [38].
As a result of the reaction of LC’s and 8 or 9, tripodal trinu-
clear complexes were obtained. These tripodal complexes
are some of the first examples of s-triazine-based trinuclear
complexes bridged to the chromium(III)/manganes(III)/
iron(III) centers by COO− (Scheme 2). All complexes are
in the solid state and, they are stable at room temperature.
They are soluble in organic solvents such as DMSO, DMF
and insoluble in water. The results of the elemental analyses
and physical properties of all ligand and complexes were
given in Table 1. The structural results of the ligand and
their complexes showed that all complexes are trinuclear.
When the 1H NMR spectrum of the Trp(PABA)3(PHBA)3
we originally synthesized are analyzed, one peak at 12.15 ppm
for three COOH groups are present in the ligand, the singlet
at 8.73 ppm corresponding to three protons are attributed to
CH hydrogen of azomethine group (C6-H), and the dublet at
8.33 ppm corresponding to six protons, the dublet at 7.77 ppm
corresponding to six protons, the dublet at 7.60 ppm corre-
sponding to six protons and the dublet at 7.43 ppm corre-
sponding to six protons, the dublet at 6.82 ppm correspond-
ing to six protons and the dublet at 6.53 ppm corresponding
to six protons are attributed to aromatic CH hydrogens. The
peak at 12.15 ppm was not observed in the 1H NMR spec-
trum taken after the addition of D2O. When the 13C NMR
spectrum is examined for Trp(PABA)3(PHBA)3, carbon peaks
are encountered at 181.915 ppm for C1, 167.620 ppm for C16,
164.425 ppm for C11, 162.150 ppm for C6, 158.780 ppm for
Interpretation of 1H NMR analyses results
1H NMR spectrum of all the complexes could not be taken
because of their paramagnetic character. All these values
are in good harmony with the previously reported results
[2, 8, 30–36]. 1H NMR spectra of Tripod and Trp(PABA)3
1
are present in the literature [32, 39]. When the H NMR
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Table 1 The elemental analysis
data and physical properties of
all ligands and complexes
Compounds (empirical formula)
µeff
M.P.
[Mw]
Contents (%)
(B.M.) °C
Yield %
Calculated/Found
296 K
Color
C
H
N
M**
–
C45H27N6O9Cl3 (6)
Dia
225*
[854.09]
96%
63.28 3.19 9.84
Trp(PABA)3Cl3
White
63.12 3.12 9.75
C66H45N9O12 (8)
Dia
390*
[1156.12] 68.57 3.92 10.90
–
–
Trp(PABA)6
l. yellow 92%
68.45 3.90 10.81
[1159.07] 68.39 3.65 7.25
l. yellow 82% 68.25 3.61 7.16
[2107.96] 64.95 4.02 9.97
75% 64.88 4.00 9.91
[2252.09] 67.20 3.76 9.33
70% 67.10 3.70 9.30
C66H42N6O15 (9)
Dia
270*
Trp(PABA)3(PHBA)3
C
114H84N15O18Cr3 (10)
Trp(PABA)6(CrSalen)3
126H84N15O18Cr3 (11)
Trp(PABA)6(CrSalophen)3
121H103N18O18Cr3 (12)
Trp(PABA)6(CrSaldeta)3
114H84N15O18Mn3 (13)
Trp(PABA)6(MnSalen)3
126H84N15O18Mn3 (14)
Trp(PABA)6(MnSalophen)3
121H103N18O18Mn3 (15)
Trp(PABA)6(MnSaldeta)3
114H84N15O18Fe3 (16)
Trp(PABA)6(FeSalen)3
126H84N15O18Fe3 (17)
Trp(PABA)6(FeSalophen)3
121H103N18O18Fe3 (18)
Trp(PABA)6(FeSaldeta)3
114H81N12O21Cr3 (19)
Trp(PABA)3(PHBA)3(CrSalen)3
3.86
3.85
3.87
2.81
2.80
4.84
1.79
1.81
5.30
3.86
3.85
3.87
2.81
2.80
4.85
1.79
1.81
5.31
320*
7.40
Green
7.33
C
>400*
6.93
Green
6.88
C
350*
[2237.17] 64.42 4.46 11.27 6.97
Green
68%
[2116.79] 64.68 4.00 9.93
64.60 4.00 9.90
[2260.92] 66.94 3.74 9.29
D. brown 88% 66.85 3.70 9.25
225
D. brown 76%
64.31 4.42 11.20 6.92
C
360*
7.79
D. brown 85%
7.75
C
235
7.29
7.25
C
[2262.04] 64.25 4.59 11.15 7.29
64.20 4.55 11.10 7.25
C
245*
[2119.51] 64.60 3.99 9.91
7.90
Brown
84%
[2263.64] 66.85 3.74 9.28
90% 66.80 3.70 9.25
64.49 3.95 9.85
7.81
C
325*
7.40
Brown
7.36
C
312
[2248.71] 64.09 4.44 11.21 7.45
Brown
70%
[2110.92] 64.86 3.87 7.96
73% 64.80 3.85 7.90
[2255.05] 67.11 3.62 7.45
75% 67.05 3.58 7.41
[2240.12] 64.34 4.32 9.38
66% 64.23 4.30 9.33
[2119.74] 64.59 3.85 7.93
64.51 3.81 7.87
[2263.87] 66.85 3.61 7.42
D. brown 90% 66.76 3.56 7.35
230* [2248.95] 64.09 4.30 9.34
D. brown 70% 64.00 4.26 9.30
[2122.47] 64.51 3.85 7.92
88% 64.40 3.81 7.84
[2266.59] 66.77 3.60 7.42
91% 66.65 3.56 7.36
[2251.67] 64.01 4.30 9.33
68% 63.89 4.19 9.26
64.00 4.40 11.18 7.41
C
335*
7.39
Green
7.35
C
126H81N12O21Cr3 (20)
390*
6.92
Trp(PABA)3(PHBA)3(CrSalophen)3
Green
6.85
C120H96N15O21Cr3 (21)
300*
6.96
Trp(PABA)3(PHBA)3(CrSaldeta)3
Green
6.91
C
114H81N12O21Mn3 (22)
Trp(PABA)3(PHBA)3(MnSalen)3
126H81N12O21Mn3 (23)
Trp(PABA)3(PHBA)3(MnSalophen)3
120H96N15O21Mn3 (24)
Trp(PABA)3(PHBA)3(MnSaldeta)3
114H81N12O21Fe3 (25)
Trp(PABA)3(PHBA)3(FeSalen)3
230
7.78
D. brown 87%
7.75
C
240*
7.28
7.14
C
7.33
7.28
C
234*
7.89
Brown
7.81
C
126H81N12O21Fe3 (26)
315
7.39
Trp(PABA)3(PHBA)3(FeSalophen)3
Brown
7.35
C120H96N15O21Fe3 (27)
285*
7.44
Trp(PABA)3(PHBA)3(FeSaldeta)3
Brown
7.40
Bold elemental analysis values are found values
Mw Calculated molecular weight, MP Melting point,
*Decomposition, **M=Cr(III), Mn(III) and Fe(III)
C7, 157.527 ppm for C2, 155.881 ppm for C12, 132.690 ppm
for C9, 131.918 ppm for C14, 130.870 ppm for C4,
129.213 ppm for C5, 128.555 ppm for C10, 127.529 ppm for
C15, 122.588 ppm for C8, 121.888 ppm for C13, 121.706 ppm
for C3. These recorded 13C and 1H resonances are consistent
with the literature [2, 8, 30–36, 40] (Fig. 4).
Interpretation of FT‑IR analyses results
When FTIR spectra of the ligands we originally synthesized
are analyzed, they seem to be in accordance with the litera-
ture. FTIR spectrum interpretation of Trp(PABA)3 is present
in the literature [32]. The IR band at 1594 cm−1 observed in
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 2 1H NMR (a) and 13C NMR (b) spectra of Trp(PABA)3Cl3
the FTIR spectrum of Trp(PABA)3Cl3 is the characteristic
band of the C(1)=N group in the s-triazine ring. The IR
bands at 1609 cm−1 for the other azomethine group, and
1703 cm−1 for carbonyl group are the characteristic bands
of C(6)=N and C(11)=O stretching vibrations, respectively
[40]. The observed IR bands at 3036 cm−1, 3007 cm−1ve
2888 cm−1 belong to aromatic and aliphatic C-H groups,
respectively. The observed aromatic ring stretching bands
between 1544–1427 cm−1 have proven the structure.
at 1398 cm−1 and 1399 cm−1 for both ligands are evalu-
ated for carboxylate COO− groups as bending vibrations,
respectively. The FTIR bands between 2942–2886 cm−1 and
3036–3007 cm−1 are attributed to aliphatic and aromatic
C–H stretching vibrations, respectively. The observed band
at 1398 cm−1 and 1246–1110 cm−1 are evaluated for amid
group (Ph-CONH-Ph) as bending vibration and ester (Ph-
COO-Ph) group as asymmetrical and symmetrical stretch-
ing vibrations, respectively. The observed aromatic ring
stretching bands between 1556–1426 cm−1 have proven the
structure (Figs. 5, 6).
The FTIR bands observed between 1613 cm−1 and
1608 cm−1 of Trp(PABA)6 and Trp(PABA)3(PHBA)3
belonging to C(6)=N stretching vibrations, and at 1703 cm−1
belonging to C(16)=O groups for both of the ligands are char-
acteristic [2, 8, 30–32, 35, 36]. The FTIR bands observed
When FTIR spectra of the [M(salen/salophen)] (M=Cr3+,
Mn3+ and Fe3+) capped complexes of Trp(PABA)6
ve Trp(PABA)3(PHBA)3 we originally synthesized
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 3 1H NMR (a) and 13C NMR (b) spectra of Trp(PABA)6
are analyzed, that the band at 1703 cm−1 for carbonyl
C=O groups of the ligands are observed in the range
of 1698–1677 cm−1 as a weaker band, and the bands
belonging to azomethine groups (C=N) in the range of
1627–1620 cm−1 originating from MSalen/Salophen caps
indicate that Msalen and Msalophen caps coordinate to COO
groups [2, 8, 30–32, 35, 36] (Figs. 5, 6).
(Table 1). For Fe(III) complexes such as [Fe(III)(salen or
salophen)], magnetic moments depend greatly upon the
axial ligands. Many works in the literature have reported
that Fe(III) cores exhibit high spin (S = 5/2) if only one
ligand donor oxygen atom coordinates to the Fe(III) cores
of salen or salophen complexes [37]. We reported in our
previous studies [2, 8, 30–36, 40–42] that when COO− ion
coordinates to Fe(III) core of salen/salophen/saldeta com-
plexes through its only one oxygen atom, Fe(III) core
exhibits high spin (S = 5/2). That is, Fe(III) has the elec-
Similarly, in the FTIR spectra of the [MSaldeta]
(M=Cr3+, Mn3+ and Fe3+) capped complexes of these both
original ligands, in addition to all of these observed bands,
the band around 3257–3205 cm−1 attributed to the N-H
vibration indicates that the ligands are coordinated to the
metal centers of the MSaldeta caps. FTIR band observed
in the range of 3420–3313 cm−1 for [M(saldeta)] (M=Cr3+,
Mn3+ and Fe3+) capped complexes of Trp(PABA)6 have
been attributed to N–H vibration of amid groups (Ph-
CONH-Ph). The observation of these bands as a broad band
with N–H bands in some complexes is due to intramolecular
and/or intermolecular H-bonds [40–42] (Fig. 5).
2
tronic structure of t2g3eg for complexes including salen
type groups. In this work, owing to obtaining all tripodal-
trinuclear [(Fe(III)salen/salophen)] complexes exhibited
low spin (S = 1/2), we have evaluated that COO− groups
of 8 and 9 coordinated to Fe(III) core of salen/salophen
with both oxygen atoms. That is, Fe(III) has the electronic
structure of t2g5eg0 for complexes including salen or salo-
phen groups. Similarly, since our all obtained tripodal-
trinuclear [(Fe(III)saldeta)] complexes exhibited high
spin (S = 5/2), we have considered that COO− groups of 8
and 9 coordinated to Fe(III) core of salen/salophen with
only one oxygen atom. That is, Fe(III) has the electronic
structure of t2g3eg2 for complexes including saldeta groups
[41, 42]. As for Cr(III) complexes, if COO− ion coordi-
nates to Cr(III) core of salen/salophen/saldeta complexes
Interpretation of magnetic susceptibility
measurements
The proposed structures of the tripodal-trinuclear com-
plexes were confirmed with magnetic measurements
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 4 1H NMR (a) and 13C NMR (b) spectra of Trp(PABA)3(PHBA)3
through its only one or both oxygen atoms, Cr(III) core
exhibits spin (S = 3/2). That is, Cr(III) has the electronic
oxygen atom. That is, Mn(III) has the electronic structure
1
of t2g3eg for complexes including saldeta groups [8, 42].
0
structure of t2g3eg for complexes including salen/salo-
Magnetic susceptibility measurements of the complexes
provide information regarding to their structures and are
presented in Table 1. This conclusion is supported by the
results of the elemental analyses suggesting that these trip-
odal-trinuclear complexes have three octahedral structures.
phen/saldeta groups. So, we proposed that COO− ion
coordinates to Cr(III) core of salen/salophen complexes
through its both oxygen atoms, and COO− ion coordinates
to Cr(III) core of saldeta complexes through its only one
oxygen atom [2, 8, 30–36, 40–42]. As for Mn(III) com-
plexes, these complexes have the electronic structure of
t2g4eg0 for complexes including salen or salophen groups.
In this work, owing to that all obtained tripodal-trinuclear
[(Mn(III)salen/salophen)] complexes exhibited low spin
(S = 1), we have evaluated that COO− groups of 8 and 9
coordinated to Mn(III) core of salen/salophen with both
oxygen atoms. That is, Mn(III) has the electronic struc-
Interpretation of TGA‑DTG analyses results
In order to test the thermal durability of the obtained com-
plexes, five of them were selected and their TGA-DTG ana-
lyzes were carried out. The samples in N2 atmosphere were
hated at 10° Celsius per minute in the temperature range
25–700 °C. The TGA curves are presented in Fig. 7. When
we study the TGA curves, it appears that the complexes
obtained have high thermal resistance. The weight losses
for all selected complexes are in good harmony with the
calculated values.
0
ture of t2g4eg for complexes including salen or salophen
groups. Similarly, since our all obtained tripodal-trinuclear
[(Mn(III)saldeta)] capped complexes exhibited high spin
(S = 2), we have evaluated that COO− groups of 8 and
9 coordinated to Mn(III) core of saldeta with only one
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
◂Fig. 5 FTIR spectra of Trp(PABA)6 (a) and its tripodal Fe(III) com-
plexes ([Trp(PABA)6(FeSalen)3] (b), [Trp(PABA)6(FeSalophen)3] (c)
and [Trp(PABA)6 (FeSaldeta)3] (d))
to (–NH-Ph-) group linked to the s-triazine core, and it is
theoretically calculated as 12.15%. The third decomposi-
tion step carried out in the temperature range of 390–595 °C
corresponds to (–C=N-Ph-C=O) group with 17.01% weight
loss. This weight loss is in good agreement with theoreti-
cally calculated one (17.49%). Decomposition continues
after 700 °C. However, according to the information we
obtain from the literature, degradation of the FeSaldeta
group corresponds to these temperatures [41, 42] (Fig. 7d).
In TGA-DTG curve of Trp(PABA)3(PHBA)3(FeSalophen)3,
we see three decomposition step up to 700 °C. The first step
in the temperature range of 115–250 °C was carried out with
7.24% weight loss. In this step, FeSalophen group detach from
main structure, and CO2 gas was released. This weight loss
is good harmony with theorically calculated one (5.83%).
The second decomposition step in the temperature range of
250–385 °C was carried out with 12.29% weight loss. This
corresponds to (–NH-Ph-) group linked to the s-triazine core,
and it is theoretically calculated as 12.06%. The third decom-
position step starts at 385 °C, and continues after 700 °C.
After this point, the decompositions of FeSalophen group and
residue organic parts linked to s-triazine center are carried
out. The decomposition data we obtained are in accordance
with the literature [30–32, 34–36, 40–42] (Fig. 7e).
In the TGA-DTG curve of Trp(PABA)6(MnSalophen)3
and Trp(PABA)6(FeSalen)3, it seems that the first weight lose
begins at 95–230 °C. In this degradation step, it is seen that
experimental and theoretical weight loss (15.20%, 12.10%
and 15.83%, 19.10% respectively) are in agreement with the
molecular weight of the –NH-Ph-CO2 group. The separation
of this group means that the MnSalophen or FeSalen caps
have been broken off from the molecular structure. In the
second degradation step for Trp(PABA)6(MnSalophen)3 in
the temperature range of 230–395 °C, the observed mass
loss of 22.68% is close to the calculated mass of 26.15%
of the organic fraction linked to the s-triazine core. In the
second degradation step for Trp(PABA)6(FeSalen)3 in the
temperature range of 250–380 °C, the observed mass loss of
9.90% is close to the organic fraction linked to the s-triazine
core. So, there is a good fit here too. Weight losses after
380 °C continue the decomposition of the remaining organic
fraction and MnSalophen or FeSalen groups linked to the
s-triazine core. During the thermal analysis, the decompo-
sition of the MnSalophen and FeSalen groups could not be
completed because heating was carried out up to 700 °C.
However, this last stage decomposition starting temperature
(395 °C) is in accordance with the literature [30–32, 34–36,
40–42] (Fig. 7a, c).
Interpretation of ESI‑MS analyses results
In TGA-DTG curve of Trp(PABA)6(FeSalophen)3, it is
seeming that first decomposition begins in the temperature
range of 95–180 °C. In this decomposition step, it is seen
that experimental and theoretical weight loss (3.90 and
5.10%, respectively) are in agreement with the molecu-
lar weight of the CO2 group. The separation of this group
means that the FeSalophen caps have been broken off from
the molecular structure. The total weight loss of 23.13% in
the second and third decomposition steps observed in the
temperature range of 180–420 °C corresponds to (–C=N-
Ph-C=ONH-Ph-) group linked to the s-triazine core, and it
is theoretically calculated as 25.85%. In the final decomposi-
tion step, the observed weight loss of 21.05% starts at 420 °C
and continues after 700 °C. According to the information we
obtain from the literature, degradation of the FeSalophen
groups corresponds to these temperatures [30–32, 34–36,
40–42] (Fig. 7b).
We investigated the mass spectrometry (ESI-MS) spectra of
four complexes selected in all complexes of this work whose
calculated molecular weights are given in Table 1. Molecular
ion peaks of the cations exhibited the same isotope distribu-
tions with the theoretically calculated ones. ESI-MS spectra
of these complexes show many molecular ion peaks (m/z)
of the cations some of which were identified in Fig. 8 for
selected complexes. The molecular ion peaks analyzed in
this work are summarized in Table 2 which demonstrates the
molecular ion peaks as given in the corresponding fragment
in Fig. 9. That is, from the investigation of ESI-MS spectra
of the complexes, it was seen that the calculated molecular
weights of the compounds were in good agreement with the
measured intensities of the ESI-MS spectra (Fig. 8).
Interpretation of Ultraviyole‑visible (UV–vis) spectra
In TGA-DTG curve of Trp(PABA)6(FeSaldeta)3, it seems
that first decomposition begins in the temperature range of
190–290 °C. In this first decomposition step, experimental
weight loss (6.58%) is consistent with a calculated weight
of 5.78% of the CO2 group released by the separation of the
FeSaldeta cap from the main structure. The second decom-
position step carried out with 9,40% weight loss in the tem-
perature range of 290–390 °C. This weight loss corresponds
Four complexes were selected in all compound, and UV–vis
spectra were taken in the range of 200–800 nm. Spectra of
the complexes were given in Fig. 10. The UV–Vis bands at
235-264-300-321, 204-244-300-372, 219-234-265-297-327
and 247-296-372 nm for complexes Trp(PABA)6(FeSalen)3,
Trp(PABA)6(FeSalophen)3, Trp(PABA)6(FeSaldeta)3 and
Trp(PABA)3(PHBA)3(FeSalophen)3, respectively, have
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 6 FTIR spectra of Trp(PABA)3(PHBA)3 (a) and its tripodal Fe(III) complexes ([Trp(PABA)3(PHBA)3(FeSalen)3] (b) and [Trp(PABA)3(PH
BA)3(FeSalophen)3] (c))
been attributed to intramolecular π → π* ve n → π* elec-
tronic transitions. That the UV–vis bands at 508, 563, 530
and 588 nm for these complexes, respectively, are caused
by 1T2g →1Eg electronic transition are supported by the lit-
erature. These bands observed in UV–vis spectra of these
complexes in the three armed dendrimeric structure have
indicated that metal ions are in octahedral geometry. Mag-
netic susceptibility values also support this.
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 7 TGA-DTG curves of [Trp(PABA)6(MnSalophen)3] (a) and [Trp(PABA)6(FeSalophen)3] (b) [Trp(PABA)6(FeSalen)3] (c),
[Trp(PABA)6(FeSaldeta)3] (d) and [Trp(PABA)3 (PHBA)3(FeSalophen)3] (e)
strategy for preparing tripodal-trinuclear [M(Salen/Salo-
phen/Saldeta)]-capped complexes uses a complex as a
“ligand” that contains a potential donor group capable of
coordinating to the other ligand. We have chosen [Cr(III)/
Mn(III)/Fe(III)(Salen/Salophen)]2O and [Cr(III)/Mn(III)/
Conclusions
In this study, two novel tripodal-oligomeric ligands and
their eighteen novel tripodal-trinuclear [M(Salen/Salophen/
Saldeta)]-capped complexes were synthesized. Synthetic
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
◂Fig. 8 ESI-MS
spectra
of
[Trp(PABA)6(MnSalen)3]
(a),
anions to the Cr(III), Mn(III) or Fe(III) centers. Their struc-
tures were characterized by means of elemental analysis,
1H NMR, 13C NMR, FT-IR spectroscopy, ESI-MS, UV–vis
spectroscopy, thermal analyses and magnetic susceptibility
measurements. The magnetic data for the complexes show
good harmony with the d4 (S=1) (for Mn(Salen/Salophen)
capped complexes) or (S = 2) (for Mn(Saldeta) capped
[Trp(PABA)6(FeSalophen)3] (b), [Trp(PABA)3(PHBA)3(CrSaldeta)3]
(c) and [Trp(PABA)3(PHBA)3(FeSalen)3] (d)
Fe(III)(Saldeta)]Cl as “ligand complexes” because they
can coordinate to the other ligand. These complexes are
some examples of these complexes bridged by carboxylate
Table 2 Molecular ion spectra and the percentages of the identified peaks for different complexes of this work
Compounds num- Fragment (1)
Fragment (2)
Fragment (3)
Fragment (4)
bers (codes)
Molecular
RA (%)
Molecular
RA (%)
Molecular
RA (%)
Molecular
RA (%)
weight (g/mol)
weight (g/mol)
weight (g/mol)
weight (g/mol)
13 (A)
17 (B)
21 (C)
25 (D)
456.08
505.07
497.10
458.06
76
47
86
49
527.16
728.14
720.17
527.16
45
85
71
40
679.14
750.22
750.22
681.12
51
65
51
74
750.22
–
–
55
–
–
750.22
64
RA denotes relative abundance, (A) [Trp(PABA)6(MnSalen)3], (B) [Trp(PABA)6(FeSalophen)3], (C) [Trp(PABA)3(PHBA)3(CrSaldeta)3], (D)
[Trp(PABA)3 (PHBA)3(FeSalen)3]
Fig. 9 The estimated ESI-MS fragments of [Trp(PABA)6(MnSalen)3] (a), [Trp(PABA)6(FeSalophen)3] (b), [Trp(PABA)3(PHBA)3(CrSaldeta)3]
(c) and [Trp(PABA)3 (PHBA)3(FeSalen)3] (d)
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 10 UV–vis spectra of selected complexes in all compounds
complexes), d5 (S = 1/2) (for Fe(Salen/Salophen) capped
complexes) or (S=5/2) (for Fe(Saldeta) capped complexes),
and d3 (S=3/2) (for all Cr(III) complexes) metal ion in octa-
hedral structures. It has been defined that these complexes
are thermally more stable than the other tripodal complexes
that we synthesized.
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Acknowledgements This study was produced from Berkman İşçi’s M.
Sc. Thesis. The authors are grateful to Karabuk University Coordinator
of Scientific Research Projects (Project No: KBÜBAP-17-YL-035) for
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