Aromatic chromophore-tethered Schiff base ligands and their iron(III)/chromium(III) Salen and Saloph capped complexes

Article abstract of DOI:10.1007/s10895-012-1075-8

Aromatic chromophores; pyrene, phenanthrene, anthracene, naphtalene and benzene-tethered Schiff base ligands and their iron(III)/chromium(III) Salen and Saloph capped complexes have been synthesized. Compounds have been characterized by means of FT-IR Spectroscopy, ¹H-NMR Spectroscopy, Magnetic Susceptibility, Elementel Analsis, TG/DTA measurements. Their fluorescence and absorbance properties have been investigated by Luminescence Spectroscopy and UV-vis Spectroscopy. Generally, ligands show an intense excimer fluorescence emissions in acetonitrilemethanol medium while iron(III) and chromium(III) complexes exhibit low fluorescence's. Intensity compared to ligands iron and chromium centers act as an extra chromophore that quench the pyrene, phenanthrene, anthracene, naphtalene and benzene molecules' singlet state. The mechanism of quenching is attributed to a iron (or chromium)-to-pyrene (or phenanthrene, anthracene, naphtalene and benzene) electronic energy transfer process. Springer Science+Business Media, LLC 2012.

Full text of DOI:10.1007/s10895-012-1075-8

J Fluoresc (2012) 22:1357–1370
DOI 10.1007/s10895-012-1075-8
ORIGINAL PAPER
Aromatic Chromophore-Tethered Schiff Base Ligands
and Their Iron(III)/Chromium(III) Salen and Saloph
Capped Complexes
Aslihan Yilmaz Obali & Halil Ismet Ucan
Received: 29 December 2011 /Accepted: 30 May 2012 /Published online: 14 June 2012
#
Springer Science+Business Media, LLC 2012
Abstract Aromatic chromophores; pyrene, phenanthrene, an-
thracene, naphtalene and benzene-tethered Schiff base ligands
and their iron(III)/chromium(III) Salen and Saloph capped
complexes have been synthesized. Compounds have been
relatively well exploited photophysical behaviors [1–4]. Fluo-
rescent molecules for 3d transition series trivalent metal ions
have been designed by means of a supramolecular approach: a
pyrene fragment (the signalling subunit-chromophore) has
been linked to Schiff base ligand (the receptor). Occurrence
of the metal receptor interaction can be signalled through either
quenching or enhancement of chromophore fluorescence.
Where the receptor is able to promote the one electron resulting
in oxidation of the metal, quenching takes place through a
photoinduced metal-to-chromophore electron transfer mecha-
nism. There are extensive investigations toward the character-
ization of chromophores including crown ether, calixarene, and
cyclodextrin derivatives with naphthalene, anthracene, or pyr-
ene chromophore. Recently, most of the chromophores
designed for metal ions operate by a photoinduced electron
transfer mechanism [5–15]. In a classic example from the de
Silva group [8–11], the binding component of the sensor is N-
(9-anthrylmethyl)-18-azacrown-6. The quenching of singlet
and triplet excited states of aromatic hydrocarbons by transition
metal ions and their coordination complexes is the most pop-
ular subject of intense investigations. A great deal of attention
has been devoted to the design and the synthesis of transition
metal complexes of chromophore-tethered ligands. These met-
allosystems have found applications of paramount interest in
many areas such as optical sensing, photocatalysis, DNA
cleavage. We have designed novel chromophore-tethered
ligands and investigated the quenching effect of Fe(III) and
Cr(III) on those compounds.
1
characterized by means of FT-IR Spectroscopy, H-NMR
Spectroscopy, Magnetic Susceptibility, Elementel Analsis,
TG/DTA measurements. Their fluorescence and absorbance
properties have been investigated by Luminescence Spectros-
copy and UV–vis Spectroscopy. Generally, ligands show an
intense excimer fluorescence emissions in acetonitrile-
methanol medium while iron(III) and chromium(III) com-
plexes exhibit low fluorescence’s. Intensity compared to
ligands iron and chromium centers act as an extra chromophore
that quench the pyrene, phenanthrene, anthracene, naphtalene
and benzene molecules’ singlet state. The mechanism of
quenching is attributed to a iron (or chromium)-to-pyrene (or
phenanthrene, anthracene, naphtalene and benzene) electronic
energy transfer process.
.
.
.
.
Keywords Fluorescence Schiff base Salen Saloph
Metal complexes
Introduction
Chromogenic or fluorogenic signaling is much more attractive
due to their sensitivity and easiness of signal detection. Among
the chromophores, pyrene, phenanthrene, anthracene, naphta-
lene compounds are most widely employed due to their
Metal complexes of the ‘Salen-type’ ligands have been
considered as interesting species in many fields of chemical
research because of some specific properties. Fe-Salen com-
plexes have been extensively studied in the solid state and in
solution [16–18]
:
A. Y. Obali (*) H. I. Ucan
Department of Chemistry, Science Faculty, Selcuk University,
Campus,
42075 Konya, Turkey
Tonami et al.[19] show a synthesis of a soluble polyphenol
by oxidative polymerization of bisphenol-A using Fe-Salen
e-mail: aslihanyilmazobali@gmail.com

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J Fluoresc (2012) 22:1357–1370
complex as catalyst. Barone et al. [20] show a catalytic activ-
ity toward the blend oxidation of hydrocarbons and undergo
electron transfer reactions, mimicking the catalytic functions
of peroxidases. Herein, we have reported the syntheses of
novel aromatic chromophore group-tethered carboxylic acid
ligands and their [Fe(III)/Cr(III) (Salen/Saloph)] capped com-
plexes. The reaction of [{Fe(Salen)}2O] with carboxylic acids
has been described by Wollmann and Hendrickson [21]. Koc
and Ucan have reported the synthesis and characterization of
1,3,5-tricarboxylato bridges with [Fe(III) (Salen/Saloph)]
[22]. We have preferred iron and chromium complexes be-
cause they are biologically significant at all the levels of living
organisms [23]. Chromium(III) complexes of Salen type
Schiff bases have been found to enhance insulin activity.
And also, various metal-Salen complexes such as manga-
nese(III), chromium(III) and nickel(II)-Salen complexes have
been used for the epoxidation of olefins [24–27].
Experimental
Materials and Methods
4-Aminobenzoic acid, benzaldehyde, 2-naphtaldehyde,
9-anthraldehyde, 9-phenanthrenecarbaldehyde, 1-pyrene-
carbaldehyde and all other reagents were purchased from Alfa
Aesar, Sigma Aldrich, Merck and used without further purifi-
cation. [{Fe(Salen)}2O], [{Fe(Saloph)}2O], [{Cr(Salen)}2O]
and [{Cr(Saloph)}2O] were prepared according to previously
published methods [28–30].
1H-NMR spectra were taken using a Bruker 400-MHz
Spectrometer. IR spectra were recorded using a Perkin
Elmer Spectrum 100 FT-IR spectrometer. Melting points
were determined by Büchi Melting Point B-540 instrument.
Elemental analyses were carried out using a LECO-CHNS-
932 elementel analyser. pH values were measured through a
Fig. 1 The structures of different tip Schiff base ligands

J Fluoresc (2012) 22:1357–1370
1359
Fig. 2 Complexation scheme of [Fe(Salen)Ln], [Fe(Saloph)Ln], [Cr(Salen)Ln] and [Cr(Saloph)Ln] (n stands for 1, 2, 3, 4, 5)
Table 1 Characteristic FT-IR values of the ligands and complexes
Compounds
C 0 N imine
C 0 O
COO¯
OH acid
ArCH
ArCH
C-C
C-H
aromatic
aliphatic
1
L1
1677
1631
1603
1623
1598
1684
1624
1601
1621
1595
1678
1621
1581
1623
1601
1685
1589
1581
1597
1530
1675
1628
1576
1624
1589
–
1288
1291
1317
1398
1385
1288
1286
1295
1398
1385
1285
1288
1313
1338
1399
1291
1296
1313
1291
1291
1291
1301
1305
1315
1291
2875
3150
3229
3339
3322
3015
3005
3110
3053
2919
3055
3245
3147
3150
3051
3000
3240
3227
3150
3033
3064
2807
3025
3012
3040
3048
851
785
757
760
743
864
748
749
740
740
876
869
872
873
847
854
863
853
855
859
840
851
854
839
848
1449
1444
1444
1470
1398
1448
1464
1463
1470
1458
1419
1441
1461
1443
1457
1426
1470
1461
1476
1457
1426
1434
1459
1414
1401
2548
2914
3015
2676
2921
2530
2905
2914
2498
2500
2533
2934
2987
2923
2929
2551
2864
2987
2988
2801
2538
2907
2845
2715
2912
2
[Fe(Salen)L1]
[Fe(Saloph)L1]
[Cr(Salen)L1]
[Cr(Saloph)L1]
L2
[Fe(Salen)L2]
[Fe(Saloph)L2]
[Cr(Salen)L2]
[Cr(Saloph)L2]
L3
[Fe(Salen)L3]
[Fe(Saloph)L3]
[Cr(Salen)L3]
[Cr(Saloph)L3]
L4
[Fe(Salen)L4]
[Fe(Saloph)L4]
[Cr(Salen)L4]
[Cr(Saloph)L4]
L5
1677
1578
1681
1676
–
–
3
–
4
–
5
–
6
2920
7
1644
1635
1684
1682
–
–
8
–
9
–
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
–
3155
1637
1604
1666
1666
–
–
–
–
–
3150
1631
1604
1685
1595
–
–
–
–
–
3047
[Fe(Salen)L5]
[Fe(Saloph)L5]
[Cr(Salen)L5]
[Cr(Saloph)L5]
1644
1603
1674
1623
–
–
–
–

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J Fluoresc (2012) 22:1357–1370
Orion Expondoble Ion Analyzer EA 940 pH meter. Mag-
netic susceptibilities of metal complexes were determined
using a Sheerwood Scientific MX Gouy magnetic suscepti-
bility apparatus using the Gouy method with Hg[Co(SCN)4]
as calibrant. The thermal analyses were performed on
Setaram SETSYS Evolution TGA/DTG DSC model. The
DTA and TG curves were obtained at the heating rate of
10 °C/min. In all cases, the 40–900 °C temperature range
was studied under a dry nitrogen atmosphere. UV–vis
spectra were recorded on Perkin Elmer Lambda 25 UV–
vis Spectrometer. The fluorescence measurements were
performed using a Perkin Elmer LS 55 Luminescence
Spectrometer.
Preparation of Ligands and Their Metal Complexes
Aromatic chromophore-tethered Sciff base ligands; 4-(benzy-
lidenamino)benzoic acid, 4-(napht-2-ilmethyleneamino)ben-
zoic acid,4-(anthracene-9-ilmethyleneamino)benzoic acid, 4-
(phenanthrene-9-ilmethyleneamino)benzoic acid, 4-(pyrene-
1-ilmethyleneamino)benzoic acid (L5) were synthesized orig-
inally (Fig. 1). N,N’-bis(o-hydroxybenzylidene)ethylenedi-
amine (Salen) and N,N’-bis(o-hydroxybenzylidene)-1,2-
diaminobenzene (Saloph) compounds and their oxygen
bridged Fe(III) and Cr(III) bridge complexes, [{FeSalen}2O],
[{FeSalophen}2O], [{CrSalen}2O], [{CrSalophen}2O] are
synthesized in accordance with the literature [31].
Fig. 3 1H-NMR spectra of the ligands; 4-(benzylidenamino)benzoic acid, 4-(napht-2-ilmethyleneamino)benzoic acid, 4-(anthracene-9-ilmethyleneamino)
benzoic acid, 4-(phenanthrene-9-ilmethyleneamino)benzoic acid, 4-(pyrene-1-ilmethyleneamino)benzoic acid in D6-DMSO

J Fluoresc (2012) 22:1357–1370
1361
General Procedure for Syntheses of Schiff Base Ligands
4-(anthracene-9-ilmethyleneamino)benzoic acid (L3);
Yield: % 64 (0.21 g), M.P.: 253 °C, FT-IR: 1,678 cm−1(C 0
N), 1H-NMR (DMSO-d6): δ 7.5–7.7 (m, 4 H, (Ar)), 7.55 (d,
2H, -CH) ve 8.1 (d, 2H, -CH), 8.2 (d, 2H, -CH), 8.3 (s, 1H, -
To a stirred solution of (1 mmol) aldehyde (benzaldehyde
for L1, 2-naphtaldehyde for L2, 9-anthraldehyde for L3, 9-
phenanthrene carbaldehyde for L4, 1-pyrene carbaldehyde
for L5) in 10 mL acetonitrile, was added dropwise a solution
of (1.2 mmol) 4-aminobenzoic acid in 10 mL acetonitrile.
The reaction mixture was stirred at room temperature for
24 h. The resulting substance was filtered, washed with cold
ethanol and acetonitrile, recrystallized from methanol. The
crystals were filtered and dried in vacuo (0.4 bar) at 60 °C.
4-(benzylidenamino)benzoic acid (L1); Yield: % 67
CH), 8.8–8.9 (t, 4 H, -CH), 9.8 (s, 1H, -HC 0 N-), λems
:
300.63 nm, Fluorescence Intensity: 329.84 (λexc: 227.55 nm),
λmax: 253 nm, A: 3.3119.
4-(phenanthrene-9-ilmethyleneamino)benzoic acid
(L4); Yield: % 55 (0.18 g), M.P.: 256 °C, FT-IR:
1
1,685 cm−1(C 0 N), H-NMR (DMSO-d6): δ 7.43 (d, 1H)
ve 8.0–8.1 (d, 1H), 7.7–7.85 (m, 6H, (Ar)), 8.15–8.2 (d, 1H)
ve 8.86–8.90 (d, 1H), 8.3 (s, 1H, (Ar)), 8.55 (s, 1H, -HC 0 N-),
8.12–8.19 (d, 1H) ve 8.86–8.91 (d, 1H), 8.92–9.0 (d, 1H) ve
9.35–9.44 (d, 1H), Elementel analysis; Calculated (Found): C
81.23 (81.05), H 4.61 (4.52), N 4.30 (4.22), O 9.86 (10.11),
1
(0.13 g), M.P. : 205 °C, FT-IR: 1,677 cm−1(C 0 N), H-
NMR (DMSO-d6): δ 7.25–7.40 (d, 2H, -CH), 7.43–7.62 (m,
5H, (Ar)) ve 7.95 (d, 2H, -CH), 8.2 (d, 2H, -CH), 8.60 (s, 1H, -
HC 0 N-), λems: 351.22 nm, Fluorescence Intensity: 867.72
(λexc: 242.71 nm), λmax: 206 nm, A: 3.3474.
λ
ems: 296.87 nm, Fluorescence Intensity: 369.79 (λexc:
227.55 nm), λmax: 252 nm, A: 1.0832.
4-(napht-2-ilmethyleneamino)benzoic acid (L2); Yield: %
4-(pyrene-1-ilmethyleneamino)benzoic acid (L5); Yield: %
1
1
53 (0.14 g), M.P.: 225 °C, FT-IR: 1,684 cm−1(C 0 N), H-
46 (0.16 g), M.P.: 240 °C, FT-IR: 1,675 cm−1(C 0 N), H-
NMR (DMSO-d6): δ 7.25–7.40 (d, 2H, -CH), 7.44–7.65 (m,
2H, (Ar)) ve 7.95–8.03 (d, 2H, -CH), 7.90–8.20 (d, 2H, (Ar)),
8.41 (s, 1H, -CH), 8.81 (s, 1H, -HC 0 N-), λems: 297.65 nm,
NMR (DMSO-d6): δ 7.5 (d, 1H) ve 8.0–8.1 (d, 1H), 8.1–8.2
(t, 2H), 8.3 (s, 1H, (Ar)), 8.24–8.45 (m, 6H, (Ar)), 8.76–8.81
(d, 1H) ve 9.25–9.31 (d, 1H), 9.65–9.69 (s, 1H, -HC 0 N),
Elementel analysis; Calculated (Found):C 82.52 (82.67), H
4.29 (4.52), N 4.01 (4.28), O 9.18 (8.52), λems: 296.87 nm,
Fluorescence Intensity: 306.82 (λexc: 227.55 nm), λmax
:
248 nm, A: 2.537.
Figure:
Experiment: Asli-4
Crucible:Al2O3 100 µl
Carrier gas: Ar - Coeff. : 1
Mass (mg): 6.5
14/04/2010
Procedure: calibrasyon (Zone 1)
SETSYS Evolution - 1750
TG/%
dTG/%/min
2.5
Delta : 2.0268 %
5
2.0
1.5
Delta : -11.0503 %
0
-5
1.0
-10
-15
-20
-25
-30
-35
Delta : -12.1557 %
0.5
0.0
Delta : -8.2591 %
-0.5
-1.0
-1.5
Delta : -6.1352 %
Delta : -5.6772 %
-2.0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750 Sample temperature/°C
Fig. 4 TG/DTA diagram of [Fe(Saloph)L3]

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J Fluoresc (2012) 22:1357–1370
Fluorescence Intensity: 410.42 (λexc: 227.55 nm), λmax
241 nm, A: 2.4721.
:
Green, BM: 3.55, λems: 295.60 nm, Fluorescence Intensity:
245.87, λmax: 200 nm, A: 1.4634, [Cr(Saloph)L1]; Yield: %
48 (0.22 g), M.P.: 287 °C, FT-IR: 1,598 cm−1 (C 0 N), Color:
Green, BM: 3.23, λems: 295.60 nm, Fluorescence Intensity:
236.49, λmax: 200 nm, A: 1.8221.
General Procedure for Syntheses of Complexes
(For the complexes of L1 ligand, the fluorescence inten-
sities were measured at λexc: 242.71 nm).
To the suspension of (0.40 mmol) [{Fe(Salen)}2O] (or [{Fe
(Saloph)}2O], or [{Cr(Salen)}2O], or [{Cr(Saloph)}2O]) in
20 mL hot methanol, was added dropwise a solution of
(0.80 mmol) Ln ligand in 20 mL hot methanol. The reaction
mixture was refluxed at 50 °C for 36 h. The resulting sub-
stance was filtered, washed with hot methanol and diethyl
ether, dried in vacuo (0.4 bar) at 60 °C.
For the Complexes of L2 [Fe(Salen)L2]; Yield: % 61
(0.25 g), M.P.: 268 °C, FT-IR: 1,624 cm−1 (C 0 N), Color:
Brown, BM: 1.69, λems: 300.20 nm, Fluorescence Intensity:
264.46, λmax: 221 nm, A: 1.3493, [Fe(Saloph)L2]; Yield: %
68 (0.31 g), M.P.: 342 °C, FT-IR: 1,601 cm−1 (C 0 N), Color:
Brown, BM: 1.70, λems: 300.20 nm, Fluorescence Intensity:
232.14, λmax: 219 nm, A: 0.6474, [Cr(Salen)L2]; Yield: % 35
(0.13 g), M.P.: 278 °C, FT-IR: 1,621 cm−1 (C 0 N), Color:
Green, BM: 3.14, λems: 297.13 nm, Fluorescence Intensity:
359.69, λmax: 222 nm, A: 0.9533, [Cr(Saloph)L2]; Yield: %
56 (0.25 g), M.P.: 291 °C, FT-IR: 1,595 cm−1 (C 0 N), Color:
Green, BM: 3.43, λems: 301.73 nm, Fluorescence Intensity:
266.77, λmax: 221 nm, A: 1.8605.
For the Complexes of L1 [Fe(Salen)L1]; Yield: % 53
(0.23 g), M.P.: 253 °C, FT-IR: 1,631 cm−1 (C 0 N), Color:
Red, BM: 1.50, λems: 342.81 nm, Fluorescence Intensity:
336.62, λmax: 219 nm, A: 2.903, [Fe(Saloph)L1)]; Yield: %
62 (0.29 g), M.P.: 272 °C, FT-IR: 1,603 cm−1 (C 0 N), Color:
Brown, BM: 1.68 λems: 349.79 nm, Fluorescence Intensity:
464.7, λmax: 295 nm, A: 3.0874, [Cr(Salen)L1)]; Yield: % 34
(0.14 g), M.P.: 288 °C, FT-IR: 1,623 cm−1 (C 0 N), Color:
Figure:
Experiment:Asli-3
Crucible:Al2O3 100 µl
Carrier gas:Ar - Coeff. : 1
Mass (mg): 6.15
14/04/2010
Procedure: calibrasyon (Zone 1)
SETSYS Evolution - 1750
TG/%
dTG/%/min
2.5
Delta : 0.8730 %
Delta : 2.0392 %
5
2.0
1.5
0
Delta : -19.8414 %
-5
1.0
-10
-15
-20
-25
-30
-35
0.5
Delta : -3.4078 %
0.0
Delta : -7.0159 %
-0.5
-1.0
Delta : -10.3195 %
-1.5
-2.0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750 Sample temperature/°C
Fig. 5 TG/DTA diagram of [Fe (Saloph) L4]

J Fluoresc (2012) 22:1357–1370
1363
(For the complexes of L2 ligand, the fluorescence inten-
sities were measured at λexc: 227.55 nm).
147.62, λmax: 250 nm, A: 0.5401, [Fe(Saloph)L4]; Yield: %
68 (0.31 g), M.P.: 293 °C, FT-IR: 1,581 cm−1 (C 0 N), Color:
Brown, BM: 1.86, λems: 299.18 nm, Fluorescence Intensity:
175.81, λmax: 254 nm, A: 1.5255, [Cr(Salen)L4]; Yield: % 35
(0.13 g), M.P.: 334 °C, FT-IR: 1,597 cm−1 (C 0 N), Color:
Green, BM: 3.16, λems: 300.71 nm, Fluorescence Intensity:
150.62, λmax: 207 nm, A: 3.5425, [Cr(Saloph)L4]; Yield: %
43 (0.19 g), M.P.: 399 °C, FT-IR: 1,530 cm−1 (C 0 N), Color:
Green, BM: 3.26, λems: 300.20 nm, Fluorescence Intensity:
176.06, λmax: 203 nm, A: 2.6077.
For the Complexes of L3 [Fe(Salen)L3]; Yield: % 68
(0.26 g), M.P.: 278 °C, FT-IR: 1,621 cm−1 (C 0 N), Color:
Brown, BM: 1.97, λems: 296.11 nm, Fluorescence Intensity:
526.96, λmax: 253 nm, A: 1.0055, [Fe(Saloph)L3]; Yield: %
73 (0.32 g), M.P.: 301 °C, FT-IR: 1,581 cm−1 (C 0 N),
Color: Brown, BM: 1.99, λems: 299.69 nm, Fluorescence
Intensity: 294.60, λmax: 250 nm, A: 1.0902, [Cr(Salen)L3];
Yield: % 42 (0.16 g), M.P.: 325 °C, FT-IR: 1,623 cm−1
(C 0 N), Color: Yellow, BM: 3.68, λems: 298.15 nm, Fluo-
rescence Intensity: 367.90, λmax: 255 nm, A: 1.4216, [Cr
(Saloph)L3]; Yield: % 53 (0.24 g), M.P.: 345 °C, FT-IR:
(For the complexes of L4 ligand, the fluorescence inten-
sities were measured at λexc: 227.77 nm).
For the Complexes of L5 [Fe(Salen)L5]; Yield: % 75
(0.14 g), M.P.: 293 °C, Color: Brown, BM: 1.84, FT-IR:
1,628 cm−1 (C 0 N), λems: 299.18 nm, Fluorescence Inten-
sity: 182.61, λmax: 232 nm, A: 1.4992, [Fe(Saloph)L5];
Yield: % 67 (0.13 g), M.P.: 290 °C, FT-IR: 1,576 cm−1
(C 0 N), Color: Brown, BM: 1.58, λems: 300.20 nm, Fluo-
rescence Intensity: 177.69, λmax: 238 nm, A: 1.2702, [Cr
(Salen)L5]; Yield: % 31 (0.06 g), M.P.: 323 °C, FT-IR:
1,601 cm−1 (C 0 N), Color: Yellow, BM: 3.70, λems
:
300.71 nm, Fluorescence Intensity: 265.26, λmax: 255 nm,
A: 3.321.
(For the complexes of L3 ligand, the fluorescence inten-
sities were measured at λexc: 227.56 nm).
For the Complexes of L4 [Fe(Salen)L4]; Yield: % 72
(0.28 g), M.P.: 275 °C, FT-IR: 1,589 cm−1 (C 0 N), Color:
Brown, BM: 1.97, λems: 299.18 nm, Fluorescence Intensity:
1,624 cm−1 (C 0 N), Color: Yellow, BM: 3.59, λems
298.67 nm, Fluorescence Intensity: 189.59, λmax: 232 nm,
:
Figure:
Experiment:Asli-2
Crucible:Al2O3 100 µl
Carrier gas:Ar - Coeff. : 1
Mass (mg): 9.1
13/04/2010
Procedure: calibrasyon (Zone 1)
SETSYS Evolution - 1750
TG/%
dTG/%/min
10
Delta : -6.6610 %
0
-5
8
6
4
2
0
-10
-15
-20
-25
-30
-35
-40
Delta : -20.5480 %
Delta : -14.9538 %
-2
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750 Sample temperature/°C
Fig. 6 TG/DTA diagram of [Cr (Salen) L4]

1364
J Fluoresc (2012) 22:1357–1370
Figure:
Experiment :Asli-1
Crucible:Al2O3 100 µl
Carrier gas:Ar - Coeff. : 1
Mass (mg): 7.78
13/04/2010
Procedure: calibrasyon (Zone 1)
SETSYS Evolution - 1750
TG/%
dTG/%/min
1.5
5
Delta : 1.9691 %
Delta : -5.4735 %
0
-5
1.0
0.5
Delta : -12.3713 %
-10
-15
-20
-25
-30
-35
0.0
Delta : -3.9846 %
-0.5
-1.0
Delta : -10.4583 %
-1.5
-2.0
Delta : -9.3222 %
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750 Sample temperature/°C
Fig. 7 TG/DTA diagram of [Fe (Saloph) L5]
A: 1.049, [Cr(Saloph)L5]; Yield: % 54 (0.11 g), M.P.:
395 °C, FT-IR: 1,589 cm−1 (C 0 N), Color: Yellow, BM:
Results and Discussion
3.68, λems: 301.73 nm, Fluorescence Intensity: 206.96, λmax
:
The synthesis of novel metal chelation driven molecular pin-
cers based on Salen type ligand substructures are described.
Five novel Schiff base ligands, Fig. 1, have different chromo-
phore groups. The oxygen bridged dimeric Salen type
239 nm, A: 0.2327.
(For the complexes of L5 ligand, the fluorescence inten-
sities were measured at λexc: 227.12 nm).
Fig. 8 Fluorescence intensities
of ligands at 297 nm (1×
10−6 M)
900,0
800
700
600
500
400
300
200
100
0,0
-
-
-
-
-
L1
L2
L3
L4
L5
240,0
260
280
300
320
330,0
nm

J Fluoresc (2012) 22:1357–1370
1365
Fig. 9 Fluorescence intensities
of L1, [FeSalenL1],
900.0
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
-
-
-
-
-
-
L1
[FeSalophL1], [CrSalenL1],
[CrSalophL1], methanol-
acetonitrile solvent mixture at
355 nm (1×10−6 M)
[FeSalenL1]
[FeSalophL1]
[CrSalenL1]
[CrSalophL1]
Methanol-Acetonitrile
0.0
220.0
240
260
280
300
320
nm
340
360
380
400
420.0
complexes [{FeSalen}2O], [{FeSaloph}2O], [{CrSalen}2O]
and [{CrSaloph}2O] can be called as ligand complexes. In
this context we have performed the complexation of ligand
complexes and fluorescent Schiff base ligands, as seen in
Fig. 2. The resulting complexes are different tip Schiff base
complexes bridged by carboxylate anions to the Fe(III) and Cr
(III) centers. All compounds are stable at room temperature in
solid state. Their structures are characterized and their fluo-
rescence and absorbance properties are investigated.
1,678, 1,685, 1,675 cm−1. After complexation with ‘ligand
complex’structures, these bands were shifted to lower frequen-
cies has indicated that oxygen atoms of Schiff base ligands are
coordinated with the ‘ligand complex’ structures (Table 1).
The vibrations of imine -CH 0 N- groups for [Fe(Salen) L1]
is 1,631 cm−1, [Fe(Saloph) L1] is 1,603 cm−1, [Cr(Salen) L1] is
1,623 cm−1, [Cr(Saloph) L1] is 1,598 cm−1, [Fe(Salen) L2] is
1,624 cm−1, [Fe(Saloph) L2] is 1,601 cm−1, [Cr(Salen) L2] is
1,621 cm−1, [Cr(Saloph) L2] is 1,595 cm−1, [Fe(Salen) L3] is
1,621 cm−1, [Fe(Saloph) L3] is 1,581 cm−1, [Cr(Salen) L3] is
1,623 cm−1, [Cr(Saloph) L3] is 1,601 cm−1, [Fe(Salen) L4] is
1,589 cm−1, [Fe(Saloph) L4] is 1,581 cm−1, [Cr(Salen) L4] is
1,597 cm−1, [Cr(Saloph) L4] is 1,530 cm−1, [Fe(Salen) L5] is
1,628 cm−1, [Fe(Saloph) L5] is 1,576 cm−1, [Cr(Salen) L5] is
1,624 cm−1, [Cr(Saloph) L5] is 1,589 cm−1. For the
ligands the bands between 2,875 and 3,047 cm−1 assigned
to the carboxylate -OH group vibrations. The bands at
FT-IR Spectra, 1H-NMR Spectra, Magnetic Moment,
Elemental Analysis and Thermal Analysis Interpretations
of the Compounds
From FT-IR spectra of ligands Ln (n01,2,3,4,5) and their
complexes, it was seen that the vibrations of the imine -CH 0
N- groups of ligands Ln in order were observed at 1,677, 1,684,
Fig. 10 Fluorescence
400.0
380
360
340
320
300
280
260
240
220
200
180
160
140
120
100
80
intensities of L2, [FeSalenL2],
[FeSalophL2], [CrSalenL2],
[CrSalophL2], methanol-
acetonitrile solvent mixture at
299 nm (1×10−6 M)
-
-
-
-
-
-
L2
[FeSalenL2]
[FeSalophL2]
[CrSalenL2]
[CrSalophL2]
Methanol-Acetonitrile
60
40
20
0.0
200.0
220
240
260
280
300
320
340
360
380
400
420.0
nm

1366
J Fluoresc (2012) 22:1357–1370
Fig. 11 Fluorescence
600.0
intensities of L3, [FeSalenL3],
[FeSalophL3], [CrSalenL3],
[CrSalophL3], methanol-
acetonitrile solvent mixture at
299 nm (1×10−6 M)
-
-
-
-
-
-
L3
560
540
520
500
480
460
440
420
400
380
360
340
320
300
280
260
240
220
200
180
160
140
120
100
80
[FeSalenL3]
[FeSalophL3]
[CrSalenL3]
[CrSalophL3]
Methanol-Acetonitrile
60
40
0.0
200.0
250
300
350
400
430.0
nm
1,288, 1,288, 1,288, 1,291, 1,291 cm−1 for the ligands
were assigned to -C 0 O groups shifted due to the coor-
dination of [Fe(Salen)], [Fe(Saloph)], [Cr(Salen)] and [Cr
(Saloph)] with COO− groups to 1291, 1295, 1313, 1296,
1301. These FT-IR values are compatible with previous works
[30, 31].
(Salen)Ln], [Fe(Saloph) Ln], [Cr(Salen) Ln] and [Cr(Saloph)
Ln] shows paramagnetic property with a magnetic suscepti-
bility values, given in experimental part, respectively. It is
seen that the [{FeSalen}2O], [{FeSaloph}2O], [{CrSalen}2O]
and [{CrSaloph}2O] containing compounds are represented
by the electronic structure of t2g5eg0 and t2g3eg0. The
magnetic data for the [{FeSalen}2O], [{FeSaloph}2O],
[{CrSalen}2O] and [{CrSaloph}2O] complexes show good
harmony with the low spin d5 and d3 metal ion in an octahe-
dral structure [31].
Elementel analyses were performed for the ligands 4-
(phenanthrene-9-ilmethyleneamino)benzoic acid, L4, and
4-(pyrene-1-ilmethylenaamino)benzoic acid, L5. According
to the analyses results, the found values are compatible with
calculated values. For L4; calculated (found) C 81.23
(81.05), H 4.61 (4.52), N 4.30 (4.22), O 9.86 (10.11), for
L5; calculated (found) C 82.52 (82.67), H 4.29 (4.52), N
1
In order to identify the ligand structures the H-NMR
spectra were recorded in DMSO-d6. The signals in spectra
of Ln ligands at δ08.60, 8.81, 8.80, 8.55, 9.67 ppm chem-
ical shifts correspond to single protons of -CH 0 N- azome-
thine groups, Fig. 3. For the complex structures because the
Fe(III) and Cr(III) metals are paramagnetic 1H-NMR spectra
did not be taken. To identify the complex structures after FT-
IR studies magnetic moments were measured at room tem-
perature. On the basis of spectral evidence the dendrimeric
low spin Fe(III) and Cr(III) cations have an approximately
octahedral environment. The magnetic moment of [Fe
Fig. 12 Fluorescence
-
-
-
-
-
-
L4
400.0
380
360
340
320
300
280
260
240
220
200
180
160
140
120
100
80
intensities of L4, [FeSalenL4],
[FeSalophL4], [CrSalenL4],
[CrSalophL4], methanol-
acetonitrile solvent mixture at
299 nm (1×10−6 M)
[FeSalenL4]
[FeSalophL4]
[CrSalenL4]
[CrSalophL4]
Methanol-Acetonitrile
60
40
20
0.0
200.0
220
240
260
280
300
nm
320
340
360
380
400.0

J Fluoresc (2012) 22:1357–1370
1367
Fig. 13 Fluorescence
500.0
intensities of L5, [FeSalenL5],
[FeSalophL5], [CrSalenL5],
[CrSalophL5], methanol-
acetonitrile solvent mixture at
299 nm (1×10−6 M)
-
-
-
-
-
-
L5
460
440
420
400
380
360
340
320
300
280
260
240
220
200
180
160
140
120
100
80
[FeSalenL5]
[FeSalophL5]
[CrSalenL5]
[CrSalophL5]
Methanol-Acetonitrile
60
40
0.0
200.0
220
240
260
280
300
320
340
360
380
400
420.0
nm
4.01 (4.28), O 9.18 (8.52). The chosen complexes [Fe
(Saloph)L3], [Fe(Saloph)L4], [Cr(Salen)L4] and [Fe(Saloph)
L5] have also been thermally investigated and their plausible
degradation schemes are presented in Figs. 4, 5, 6 and 7. For
those complexes, thermal decomposition of the anhydrous [Fe
(Saloph)] and [Cr(Salen)] complexes left from the ligands
have started in the range of the first step 250–575 °C, the
second step 475–690 °C and the final step 585–695 °C. The
final decomposition products were metals and aromatic rings,
pyrene, phenanthrene and anthracene. The observed weight
losses for all ligands and complexes are in good harmony with
the calculated values.
Table 2 Excitation wavelengts,
No
Compounds
λeks (nm)
λems (nm)
Fluorescence intensity
emission wavelenghts and max-
imum fluorescence intensity
values of the ligands and
complexes
1
L1
242.71
242.71
242.71
242.71
242.71
227.55
227.55
227.55
227.55
227.55
227.56
227.56
227.56
227.56
227.56
227.77
227.77
227.77
227.77
227.77
227.12
227.12
227.12
227.12
227.12
351.22
342.81
349.79
295.60
295.60
297.65
300.20
300.20
297.13
301.73
300.63
296.11
299.69
298.1
867.72
336.62
464.71
245.87
236.49
306.82
264.46
232.14
359.69
266.77
329.84
526.96
294.60
367.90
265.26
369.79
147.62
175.81
150.62
176.06
410.42
182.6
2
[Fe(Salen)L1]
[Fe(Saloph)L1]
[Cr(Salen)L1]
[Cr(Saloph)L1]
L2
[Fe(Salen)L2]
[Fe(Saloph)L2]
[Cr(Salen)L2]
[Cr(Saloph)L2]
L3
[Fe(Salen)L3]
[Fe(Saloph)L3]
[Cr(Salen)L3]
[Cr(Saloph)L3]
L4
[Fe(Salen)L4]
[Fe(Saloph)L4]
[Cr(Salen)L4]
[Cr(Saloph)L4]
L5
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
300.71
296.87
299.18
299.18
300.71
300.20
296.87
299.18
300.20
298.67
301.73
[Fe(Salen)L5]
[Fe(Saloph)L5]
[Cr(Salen)L5]
[Cr(Saloph)L5]
177.69
189.59
206.96

1368
J Fluoresc (2012) 22:1357–1370
Fig. 14 Maximum absorbance
sequence of ligands (1×10−5 M)
Fluorescence and Absorbance Investigation of Ligands
and Complexes
L1, shows the lowest fluorescence. According to the conjugat-
ed π electron system fluorescence property changes. Increase
of the aromatic groups in a system enhance the fluorescence.
We proved that knowledge; at 297 nm the fluorescence inten-
sities of ligands were observed as: L5 > L4 > L3 > L2 > L1.
Schiff base compounds generally give weak emission
bands. This is due to photoinduced electron transfer (PET)
from lone pair of imine nitrogen to the photo-excited pyrene
(or phenanthrene, anthracene, naphtalene, benzene) which
leads to fluorescence quenching [32]. Herein, fluorescence
intensities of L1,L4,L5 with the concentration 1×10−6 M (at
355 nm for L1, 299 nm for L4 and L5) are higher than their
metal complexes. This is because of quenching effect of iron
and chromium metals on chromophore groups. Ligands L1,L4,
L5 show more fluorescence than their complexes but interest-
ingly, the other L2 and L3 ligands do not (Figs. 9, 10, 11, 12
and 13). In some fluorescence studies, somehow, it is seen Fe
(III) and Cr(III) complexes show unexpected results [33–35].
The fluorescence intensity values at their excitation wave-
lengths of all compounds were given in Table 2.
The electronic absorption spectra of the free ligands and
their metal complexes were recorded in solution at room
temperature by UV–vis absorption spectroscopy. Absor-
bance studies were performed for all compounds between
200 and 800 nm. The solvent mixture were methanol-
acetonitrile (4:3) with the concentration 1×10−5 M. The
UV–vis absorption spectrum of all the compounds (1×
10−5 M) exibits absorption bands between λmax: 200–
420 nm. As seen from Fig. 14, the decrease of aromatic
groups in a system shifts maximum absorbance wavelenghts
to the lowest energy regions. This shifts were resulted from
π → π* ve n → π* electronic transitions between conju-
gated aromatic group and azomethine (CH 0 N) group in a
system. Absorbances of all compounds at their maximum
wavelengths were given in Table 3.
All compounds were synthesized originally and all showed
fluorescent property. Herein, fluorescent properties of
chromophore-tethered Schiff base ligands and their complexes
were measured in methanol-acetonitrile (4:3) medium with the
concentration 1×10−6 M. As seen from Fig. 8 when all the
ligands (1×10−6 M) excited at 297 nm, pyrene-appended one,
L5, shows the highest fluorescence and benzene-appended one,
Table 3 Maximum absorbance values of ligand and complexes on
UV-spectra
No
Bileşikler
λmaks (nm)
Absorbans (A)
1
L1
206
219
295
200
200
248
221
219
222
221
253
254
250
255
255
252
250
254
207
203
241
232
287
232
201
3.3474
2.903
2
[Fe(Salen)L1]
[Fe(Saloph)L1]
[Cr(Salen)L1]
[Cr(Saloph)L1]
L2
[Fe(Salen)L2]
[Fe(Saloph)L2]
[Cr(Salen)L2]
[Cr(Saloph)L2]
L3
[Fe(Salen)L3]
[Fe(Saloph)L3]
[Cr(Salen)L3]
[Cr(Saloph)L3]
L4
[Fe(Salen)L4]
[Fe(Saloph)L4]
[Cr(Salen)L4]
[Cr(Saloph)L4]
L5
3
3.0874
1.4634
1.8221
2.537
4
5
6
7
1.3493
0.6474
0.9533
1.8605
3.3119
1.0657
1.0902
1.4216
3.321
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
1.0836
0.5401
1.5255
3.5425
2.6077
0.2495l
1.4992
1.3726
1.049
Conclusion
[Fe(Salen)L5]
[Fe(Saloph)L5]
[Cr(Salen)L5]
[Cr(Saloph)L5]
In this context, fluorescent different tip Schiff base ligands
are presented. All ligands contain a potential donor group
capable of coordinating with the other ligand. We have
2.4721

J Fluoresc (2012) 22:1357–1370
1369
14. Kubo K, Ishige R, Sakurai T (1998) Synthesis and complexation
behavior of N, N′-bis (9-anthrylmethyl)-1, 4, 10, 13-tetraoxa-7,
diazacyclooctadecane. Heterocycles 48:347
15. Kubo K, Ishige R, Sakurai T (1999) Synthesis and complexation
behavior of N-(1-naphthylmethyl)-1,4,7,10,13-pentaoxa-16- aza-
cyclooctadecane. Talanta 48:181
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structures, electrochemistry and magnetic properties of chain-like
dicyanamide manganese(III) and iron(III) complexes with salen
ligand. New J Chem 26:1397–1401
17. Darensbourg D, Ortiz CG, Billodeaux DR (2004) Synthesis and
structural characterization of iron(III) salen complexes possessing
appended anionic oxygen donor ligands. Inorg Chim Acta
357:2143–2149
18. Roy P, Dhara K, Chakroborty J, Nethaji M, Banerjee P (2007)
Synthesis and crystall structure of an iron (II) dimeric complex.
Indian J Chem 46A:1947–1950
19. Tonami H, Uyama H, Oguchi T, Higashimura H, Kobayashi S
(1999) Synthesis of a soluble polyphenol by oxidative polymeri-
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chosen [{FeSalen}2O], [{FeSaloph}2O], [{CrSalen}2O],
[{CrSaloph}2O] as ‘ligand complexes’ because they can
coordinate with the other ligand. These complexes are dif-
ferent tip Schiff base complexes bridged by carboxylate
anions to the iron and chromium centers. Their structures
1
were characterized by means of FT-IR Spectroscopy, H-
NMR Spectroscopy, Magnetic Susceptibility, Elementel
Analsis, TG/DTA. The magnetic data for the complexes
show good harmony with the d5 and d3 metal ion in an
octahedral structure. Absorption and fluorescence properties
were investigated by UV–vis Spectroscopy and Lumines-
cence Spectroscopy.
Acknowledgments We thank the Scientific Research Projects Foun-
dation of Selcuk University (Konya/TURKEY) (SUBAP-Grant Number
2010/09101052) for financial support of this work produced from a part
of Aslıhan YILMAZ OBALI’s MSc Thesis.
20. Barone G, Silvestri A, La Manna G (2005) DFT computational
study on FeIII-N, N′-ethylene-bis(salicylideneiminato) derivatives.
Mol Struct THEOCHEM 715:79–83
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