A.K. Singh, B.P. Baranwal / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 98 (2012) 302–306
303
photocatalytic activity [15,16]. In this light we have reported some
2.3. Synthesis of [Ti(acac)Cl(dbzm)(OOCC15H31)] (1)
titanium(IV) complexes having Ti–O–C bond with increased resis-
tance towards hydrolysis [17].
Sodium salts of b-diketones were prepared by adding the re-
quired amount of sodium metal to an excess of isopropanol (so-
dium isopropoxide formed in situ). The solution thus formed was
added slowly to the b-diketones in isopropanol and the contents
were boiled to reflux for 2 h. Removal of excess solvent under vac-
uum yielded the desired sodium salts of b-diketones. To the sus-
pension of [Ti(acac)Cl3] [22] (2.11 g, 8.33 mmol) in benzene
(40 mL), sodium palmitate (2.32 g, 8.33 mmol) was added. The
contents were stirred for 8 h followed by refluxing for 2 h. The con-
tents were filtered using G 4 sieve to remove insoluble sodium
chloride formed during the reaction. The excess solvent was re-
moved in vacuo and an yellow coloured solid, [Ti(acac)Cl2(OOCC15-
H31)] (A) was obtained. This composition was confirmed by the
elemental analysis and infrared spectral study [17]. To a solution
of A (1.82 g, 3.90 mmol) in benzene (50 mL), sodium salt of dib-
enzoylmethane (Nadbzm) (0.95 g, 3.90 mmol) was added. The con-
tents were stirred for 9 h followed by refluxing for 3 h. Insoluble
sodium chloride formed during the reaction was filtered out. Ex-
cess solvent from the soluble part was removed in vacuo to yield
a dark yellow solid. It was purified in dichloromethane-n-hexane
mixture (1:1 ratio). An analogous procedure was adopted to syn-
thesize other titanium(IV) complexes and details of analytical re-
sults are given in Table 1.
Keeping in view of these objectives, we report here an easier
method of synthesis for nano-sized, mixed-ligand complexes of
titanium(IV) in which titanium is attached with all the different
type of four ligands. Carboxylic acid and b-diketones have been
used in the light that incorporation of these ligands in titanium(IV)
complexes may enhance the cytotoxicity providing a better candi-
date for anticancer agents [18,19]. These ligands act as potential
chelating agents providing hydrolytically stable nature of the prod-
ucts. The complexes are hydrolytically stable bearing Ti–O–C link-
age, a basic requirement for catalytic action. The complexes are
characterized using different spectral techniques and their coordi-
nation behavior is discussed.
2. Experimental
2.1. Materials and analytical methods
All the reactions were carried out under anhydrous conditions.
Organic solvents (Qualigens) were dried and distilled before use by
standard methods [20]. Sodium palmitate, acetylacetone, benzoyl-
acetone, dibenzoylmethane (Aldrich) and TiCl4 (BDH) were used as
received. Titanium and chlorine were estimated gravimetrically as
TiO2 and AgCl respectively [21].
3. Results and discussion
Some mixed-ligand complexes of titanium(IV) were synthe-
sized by stepwise substitutions of chloride ions from titanium tet-
rachloride as depicted below:
2.2. Physico-chemical measurements
1H NMR spectra were recorded at 300 MHz on a Bruker DRX-
300 NMR spectrometer in CDCl3. Electronic spectra were recorded
on Hitachi U-2000 spectrophotometer in toluene. Infrared spectra
were recorded on a Perkin-Elmer RX1 FTIR spectrophotometer
using KBr discs. Powder XRD data were collected on a PW 1710 dif-
fractometer. The operating voltage of the instrument was 30 kV
and the operating current was 20 mA. The intensity data were col-
lected at room temperature over a 2h range of 5.025–79.925° with
a continuous scan mode. Transmission electron microscopy (TEM)
images were obtained on a Tecnai 30 G2S – Twin electron micro-
scope with an accelerating voltage of 300 kV on the surface of a
carbon coated copper grid. Molar conductance were measured on
century CC-601 digital conductivity meter at 10ꢀ2–10ꢀ3 molar
solutions in nitrobenzene. Solid state conductance measurements
were carried out with Keithley 6220 Precision current source and
keithley 2182 A Nanovoltmeter. Magnetic moment was measured
on a Gouy balance using Hg[Co(SCN)4] as a calibrant. Elemental
analyses (C, H) were done on a Vario EL III Carlo Erba 1108 elemen-
tal analyzer. Molecular weights were determined in a semi-micro
ebulliometer (Gallenkamp) with a thermistor sensing device.
TiCl4þHacacBenzene
! ½TiðacacÞCl3ꢁþHCl"
Reflux
½TiðacacÞCl3ꢁþC15H31COONaBenzene
!
½TiðacacÞCl2ðOOCC15H31ÞꢁþNaCl#
Reflux
A
AþnNaLBenzene
! ½TiðacacÞCl2ꢀnðLÞnðOOCC15H31ÞꢁþnNaCl#
Reflux
where Hacac = acetylacetone; NaL = Sodium salt of dibenzoylme-
thane (Hdbzm) or benzoylacetone (Hbzac) and n = 1 or 2.
Benzene was chosen as a solvent in these substitutions because
sodium chloride formed during the reaction was insoluble and the
titanium(IV) complexes were soluble which could make the sepa-
ration easy. The molar conductance of complexes at 10ꢀ2–10ꢀ3
molar concentrations in nitrobenzene was obtained in the range
2–8 Oꢀ1 cm2 molꢀ1 which indicated them to be non-electrolytes
[23]. Solid state conductance measurements were done for all the
complexes and were found in the range 1.8 ꢂ 106–3.2 ꢂ 106 O at
295 K using current 1 ꢂ 10ꢀ8 A and voltage 1.4 ꢂ 10ꢀ2 V. This
clearly indicated them to show high resistance or they could be
said to behave like insulators. Room temperature magnetic
Table 1
Analytical results for the titanium(IV) complexes.
Reactantsa (g, mmol)
Product (colour) (% yield)
MP (°C)
Found (calculated)%
Ti Cl
7.18 5.29
Molecular weight found (calcd.)
C
H
[Ti(acac)Cl2(OOCC15H31)] + Nadbzm
(1.82, 3.90) (0.95, 3.90)
[Ti(acac)Cl2(OOCC15H31)] + Nadbzm
(1.91, 4.0) (1.9, 8.1)
[Ti(acac)Cl2(OOCC15H31)] + Nabzac
(2.1, 4.40) (0.82, 4.41)
[Ti(acac)Cl2(OOCC15H31)] + Nabzac
(1.8, 3.81) (1.40, 7.63)
[Ti(acac)Cl(dbzm)(OOCC15H31)]
(Dark yellow) (83) (1)
[Ti(acac)(dbzm)2(OOCC15H31)]
(Yellow) (85) (2)
[Ti(acac)Cl(bzac)(OOCC15H31)]
(Dark yellow) (88) (3)
[Ti(acac)(bzac)2(OOCC15H31)]
(Yellow) (81) (4)
138
146
116
124
65.48
(65.40)
72.28
(72.15)
62.16
(62.15)
67.87
7.57
(7.49)
7.19
(7.14)
7.88
(7.92)
7.69
652
(661)
854
(848)
610
(599)
733
(724)
(7.24)
5.48
(5.36)
(5.64)
8.02
5.82
(7.99)
6.49
(5.92)
(6.61)
(67.94)
(7.80)
a
Reflux about 3–4 h.