SYNTHESIS AND CHARACTERIZATION OF TRANSmON METAL COMPLEXES WITH SCmFF BASE LIGANDS CONTAINING ONNI
N1S1.. DONOR ATOMS
,
Wan Siti Fatimah Bt. Wan Megat Mohammad
QD 474 W244
2008
Bachelor of Science with Honours (Resource Chemistry)
2008
~ r
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eusat Khi t Kaae~
UNIVERsm '! I A ARAW Q4300 Kota Sarnarabaa
P.KHIDMAT MAKLUMAT AKADEMIK UNIMAS
11111111 I" II "111111 1111111
1000166627
Synthesis and Characterization of Transition Metal Complexes with Schiff Base Ligands Containing ONNIN2S2-Donor Atoms
WAN SITI FA TIMAH BT. WAN MEGAT MOHAMMAD
This project is submitted in partial fulfillment of
the requirements for the Degree of Bachelor of Science with Honours (Resource Chemistry)
Faculty of Resource Science and Technology UNIVERSITI MALAYSIA SARA W AK
2008
DECLARATION
,....
No portion of the work referred to in this report has been submitted in support of an application for another degree of qualification of this or any other university or institution of higher learning.
Wan Siti Fatimah Bt. Wan Megat Mohammad (15486)
.
Chemistry Department
Faculty of Resource Science and Technology Universiti Malaysia Sarawak
ii
ACKNOWLEDGEMENTS
The author would like to express the greatest gratitude to Assoc. Prof. Dr. Md. Abu Affan as supervisor who has helped the author, for his unfailing help and guidance throughout the course of this project work. The author also would like to express her sincere thanks to Miss.
Irene and Mr. Foo, M.Sc. students of the Chemistry Department, UNIMAS for their inspiration and occasional help. Besides, the author would like to express her sincere thanks to Mr. Mohd. Zacaery bin Khalik and all staff of Chemistry Department for their inspiration and valuable advice to accomplish this work.
iii
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..
---~Chapter One: Introduction
1.1 Schiff base ligands containing NS-donor atom and their transition metal complexes
1.2 Schiff base ligands containing ON -donor atom and their transition metal
complexes 3
1.3 Chelate effect 4
1.4 Objectives of the project 5
Chapter Two: Literature Review 6
2.1 Schiffbase ligands containing NS-donor atom 6
2.2 Schiffbase ligands containing NS-donor atom and their transition metal
complexes 8
2.3 Schiff base ligands containing ON-donor atom 10
2.4 Transition metal complexes containing ON-donor atoms 12
Chapter Three: Materials and Methods 14
3.1 Research methodologies and framework 14
3.2 Solvent distillation 15
3.3 Synthesis of Schiff base ligands (1-2) 15
3.3.1 Synthesis of2-benzoylpyridine-2-hydroxybenzhydrazone ligand (1) 15 3.3.2 Synthesis of N,N'-bis(2-thiophene carboxaldehyde)-1,2-ethylene
diamine ligand (2) 16
3.4 Synthesis of transition metal complexes (3-9) 16
3.4.1 Synthesis of [Mn(CI9HI402N3)CH3COO]'2H20 (3) 16
3.4.2 Synthesis of [Co(CI9HI402N3)CI1'2H20 (4) 17
3.4.3 Synthesis of [Ni(CI9HI402N3)CI1'2H20 (5) 18
3.4.4 Synthesis of [Cu(CI9H'402N3)CI1'2H20 (6) 19
3.4.5 Synthesis of [Zn(C19H'402N3)N031'2H20 (7) 20
3.4.6 Synthesis of [CO(CI2HI2N2S2)]Ch·2H20 (8) 21
3.4.7 Synthesis of [Ni(CI2HI2N2S2)]Ch·2H20 (9) 22
Chapter Four: Results and Discussion 23
4.1 Synthesis and some physical properties 23
4.2 UV-Visible spectra studies 26
4.2.1 UV-Visible analyses of ligand (1) and its transition metal complexes
(3-7) 26
4.2.2 UV -Visible analyses of ligand (2) and its transition metal complexes
(8-9) 29
iv
f:#usal Khittrnal MaklUmal Akaaenn..
UNlVERSITI MALAYSIA SARAW.u
041()() Knt2 Samaranan
1
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I
I
4.3 Infrared (IR) spectra studies 31
4.3.1 IR spectra studies of ligand (1) and its transition metal complexes
(3-7) 31
4.3.2 IR spectra analyses of ligand (2) and its transition metal complexes
(8-9) 37
4.4 IH NMR studies of2-benzoylpyridine-2-hydroxybenzhydrazone ligand (1)
and its Zn(II) complex (7) 41
Chapter Five: Conclusion 45
Chapter Six: Suggestions for future research
46
References
47
Appendix
v
,...
t: List of Tables Pages
Table 1: Physical and analytical data of Schiff base ligands (1-2) and their
transition metal complexes (3-9) 25
Table 2: Molar conductance values of transition metal complexes (3-9) 26 Table 3: The
Amax
(nm) peaks of Schiff base ligand (1) and its transition metalcomplexes (3-7) 27
Table 4: The
Amax
(nm) peaks of Schiff base ligand (2) and its transition metalcomplexes (8-9) 29
Table 5: Main IR data of Schiff base ligand (1) and its transition metal complexes
(3-7) (cm-I)a 33
Table 6: Main IR data of Schiff base ligand (2) and its transition metal complexes
(8-9) (cm-I)a 38
Table 7: IH NMR data of ligand (1) and its Zn(II) complex (7) (0 ppm)b 42
vi
1
List of Figures Pages Fig. 1: Chemical structure ofS-benzyl-P-N-(5-methyl-2-furylmethylene)
dithiocarbazate (NS) 6
Fig. 2: Chemical structure ofS-benzyl-p-N-(2-furylmethylketone)dithiocarbazate
(NS') 7
Fig. 3: The thione (a) and the thiol (b) forms ofH2SNNNS (R
=
SCH2Ph) 8 Fig. 4: Synthesis of Cu2+,
Ni2 +and Zn2 + complexes from S-methyldithiocarbazatewith (a) 2-furylmethylketone (b) 5-methyl-2-furaldehyde 9 Fig. 5: Structural formulas of pyridoxal semicarbazone 11
Fig. 6: Structure of2-acetylpyridinebenzhydrazone 11
Fig. 7: Schiff base ligands 11
Fig. 8: Similarity between a non-symmetrical salen-type ligand and benzhydrazide
Schiff base ligand 12
Fig. 9: The structure ofCu complex with ligand of salicylaldehyde and glycine 13 Fig. 10: The keto (a) and the enol (b) forms of2-benzoylpyridine-2-hydroxybenz
hydrazone ligand (1) 23
Fig. 11: UV spectra of ligand (1) and its Zn(II) complex (7) in chloroform (1 x 10-4 M) 28 Fig. 12: UV spectra of ligand (2) and its Ni(II) complex(9) in chloroform (1 x 10-4 M) 30 Fig. 13: IR spectrum of [CI9H1S02N3] ligand (1) (As KBr disc) 34 Fig. 14: IR spectrum of[Mn(CI9HI402N3)CH3COO]-2H20 (3) (As KBr disc) 35 Fig. 15: IR spectrum of [CU(CI9HI402N3)CI]'2H20 (6) (As KBr disc) 36 Fig. 16: IR spectrum ofN,N'-bis(2-thiophene carboxaldehyde )-1 ,2-ethylenediamine
ligand [CI2HI2N2S2] (2) (As KBr disc) 39
Fig. 17: IR spectrum of [Ni(CI2HI2N2S2)]Ch'2H20 (9) (As KBr disc) 40 Fig. 18: IH NMR spectrum of ligand [CI9HlS02N3] (1) (In CDCh) 43 Fig. 19: IH NMR spectrum of [Zn(CI9HI402N3)N03]-2H20 complex (7) (In CDCh) 44 Fig. 20: UV spectra of ligand (1) and its Co(ll) complex (4) in chloroform (1 x 10-4 M) 53 Fig. 21: IR spectrum of[Co(CI9HI402N3)CI]-2H20 (4) (As KBr disc) 54 Fig. 22: IR spectrum of [Zn(CI9HI402N3)N03]'2H20 (7) (As KBr disc) 55 Fig. 23: IR spectrum Of[CO(CI2HI2N2S2)]Ch'2H20 (8) (As KBr disc) 56
vii
I
List of Schemes Pages
Scheme I: Fonnation of Schiff base ligands 2
Scheme 2: Tautomeric fonns. (a) Thione fonn. (b) Thiolo fonn. NS: X = CH3,
Y=H;NS':X=H, Y=CH3 7
Scheme 3: Synthesis ofPd2
+,
Sn2+,
Fe2+,
Cu2+, Co2+,
and Cd2+ complexes from Sbenzyldithiocarbazate with NS" 1 0
Scheme 4: Metal complex synthesis 13
Scheme 5: Structure of2-benzoylpyridine-2-hydroxybenzhydrazone ligand (1) 15 Scheme 6: Structures ofN,N' -bis(2-thiophene carboxaldehyde)-1 ,2-ethylenediamnie
ligand (2) 16
Scheme 7: Proposed structure of Mn(U) complex (3) 17
Scheme 8: Proposed structure of Co(Il) complex (4) 18
Scheme 9: Proposed structure ofNi(II) complex (5) 19
Scheme 10: Proposed structure ofCu(II) complex (6) 20
Scheme II: Proposed structure of Zn(II) complex (7) 21
Scheme 12: Proposed structure of Co(I1) complex (8) 22
Scheme 13: Proposed structure ofNi(U) complex (9) 22
viii
I
Synthesis and Characterization of Transition Metal Complexes with Schiff Base Ligands Containing ONNIN2~-DonorAtoms
Wan Siti Fatimah Bt. Wan Megat Mohammad
Chemistry Department
Faculty of Resource Science and Technology Universiti Malaysia Sarawak ABSTRACT
Five transition metal complexes (3-7) of 2-benzoylpyridine-2-hydroxybenzhydrazone ligand (1) and another two transition metal complexes (8-9) of N.N' -bis(2-thiophene carboxaldebyde)-1,2-ethylenediamine ligand (2) have been synthesized. Schiff base ligands (1-2) and their transition metal complexes (3-9) were characterized by using CHN analysis, UV-Visible and IR spectral studies. Among them, ligand (1) and its complex (7) have also been analysed by 'H NMR analysis. All transition metal complexes (3-9) are non electrolytic in nature. Spectral studies suggested that ligand (1) acts as a mononegative tridentate nature, while the ligand (2) acts as a neutral tetradentate nature in their transition metal complexes.
The probable structrures of the complexes have been deduced on the basis of their analytical and spectroscopic data.
Keywords: Transition metal complexes; N,N'-bis(2-thiophene carboxaldehyde )-1 ,2-ethylene diamine; 2-benzoylpyridine-2-hydroxybenzhydrazone; spectral studies.
ABSTRAK
Lima kompleks logam peralihan (3-7) dari ligan (1) 2-benzoilpiridina-2
hidroksibenzhidrazona dan dua lagi kompleks logam peralihan (8-9) dari ligan (2) N,N'
bis(2-thiofina karboksaldihida)-1,2-etilinadiamina telah disintesiskan. Schiff bes ligan (1-2) dan kesemua kompleks logam peralihan (3-9) telah dicirikan dengan menggunakan analisis CHN, UV-Visible dan kajian spectra JR. Antaranya, ligan (1) dan komplek (7) telah dicirikan dengan menggunakan JH NMR analisis. Kesemua kompleks logam peralihan (3-9) bersifat bukan elektolit secara semulajadi. Kajian spectra menunjukkan bahawa ligan (1) bertindak sebagai mononegatif tridentat secara semulajadi, manakala ligan (2) bertindak sebagai tetradentat yang bersifat neutral secara semylajadi dalam kompleks logam peralihan.
Struktur molekul kompleks telah dicadangkan berdasarkan analisis dan data spektroskopik
Kata /cunei: Kompleks logam peralihan; N,N'-bis(2-thiofina karboksaldihida)-1,2-etilina diamina; 2-benzoilpiridina-2-hidroksibenzhidazona; kajian spectra.
IX
CHAPTER ONE INTRODUCTION
1.1 Schiff base ligands containing NS-donor atom and their transition metal complexes
The coordination chemistry of transition metal complexes has received great attention over the past few years. This is mainly due to the potential application of these complexes in various types of processes (Kia et af., 2006). Coordination compound is a compound that consists of central metal ion which is attached by ligands. Formation of complex compound may be regarded as a reversible association of one or more metal and ligands.
NiCI2
+ ..
~i~1I3)6]CI2(Green solution) (Purple crystal complex)
Ligands is defined as the neutral molecules or ions which are usually anions, and has the capability of attaching to the central metal ion in the formation of complex compound. In Lewis sense, the ligands act as Lewis bases which donate electron pair, and the central metal ion act as Lewis acid which accept the electron pair.
The Schiff base ligands are one of the most widely used ligands to form metal complexes due to the formation of remarkable versatility because of the intriguing observation that different ligands shows different biological properties, although they may differ only slightly in their molecular structure (Chew et af., 2004). Metal complexation is a widespread interest. It is
studied by inorganic chemists, physical, organic biochemists, pharmacologist, biomolecular biologist and also environmentalist.
Schiff bases are an important class of ligands in metal coordination chemistry even after almost a century since their discovery (Pettinari et al., 2001). Schiff bases is a chemical compounds containing a carbon-nitrogen bond. The nitrogen atom is connected to an aryl or an alkyl group but not hydrogen. Schiff bases can be synthesized by condensation reaction of primary amine and an aldehyde or ketone (Scheme 1). The formation of a Schiff base is an important step in many biochemical reactions (Parker, 1993).
+
R"-NH2+
R' Scheme 1: Formation of Schiff base ligands
Schiff base ligands can also be found in monodentate, bidentate, tridentate, tetradentate and others. The polydentate Schiff base ligands can form very stable complexes with transition metal and heavy metal ions. A large number of Schiff base ligands and their metals complexes have been studied due to their important characteristic and properties. Metals complexes of Schiff base have attracted great interest due to their remarkable antifungal, antibacterial, and antitumor activities (Tarafder et ai., 2002a).
The Schiff base ligands and their metal complexes have been tested for antibacterial activity against several strains which can build up resistant to classical antibiotic, such as Escherichia coli, Staphyococcus aureus and Pseudomonas aerugirwsa (Cholan et ai., 1993).
2
1.2 Schiff base ligands containing ON-donor atom and their transition metal complexes
Coordination complexes between metal ions and N20 2 donor ligands exhibit different types of crystal structure, a broad spectrum of biological properties, including antibacterial and antiviral activities (Zahra et al., 2005). Chemically, polydentate (tetradentate) ligands such as
N~are of interest because of the presence of several potential donor atoms, their flexibility to coordinate in either neutral or deprotonated forms.
For examples, Ni(II) complex with N202 Schiff base ligands derived from salicylaldehyde have long been used as homogeneous catalysts (Santos et al., 2000). The coordination chemistry of transition complexes with salen-type ligands has achieved a special status because of tbeir ~-binding reactivity, redox chemistry, unusual magnetic and structural properties, as well as their usage as models for metallo-proteins, as 'metallo-ligands' (Kasumov el al., 2005). Besides, it is also because of the chemical or electrochemical reduction of electrophiles, such as alkyl and aryl halides, and carbon dioxide (Azevedo et aI., 2002). Macrocyclic Schiff base ligands derived from thiosemicarbazide are of significant interest fro their pharmacological properties as antibacterial and anticancer agents (Arquero et aI., 1998).
3
1.3 Chelate effect
Chelate effect is one of the properties that affecting the stability of the complexes in the nature of the ligands. Chelate is a group of units that hold tightly to the central metal ions to produced heterocyclic ring. Complexes containing chelate effect are usually more stable than similar complexes containing no ring. For example, coordination compound which involving a chelating, multidentate ligand has an unusual stability as compared to the same coordination compounds which only involving monodentate ligand (Rodgers, 2002). The greater stability of a chelate complex as compared to that of a non-chelated complex is due to the increase in entropy.
Cd2 + (aq) + 2 en (aq)
Overall stability constant, Log
p
= 10I 0.6Cd2 + (aq) + 4 MeNH2 (aq) c [Cd(MeNH2)4f+ (aq)
Overall stability constant, Log
p
= 106. 5 (Jones, 2002)The stability constant,
p
for the complex [Cd(enh]2+ (aq) is almost 104 times greater compared to [Cd(MeNH2)4]2+ (aq). This is due to the fact that the former complex contains chelate rings while the later one has no chelate ring. Indeed, Schiff base chelating systems offer a considerable versatility in their substituent groups (Mevellec et al., 2002).4
1.4 Objectives of the Project
The main objectives of this project are:
a. to synthesize two Schiff base ligands.
b. to synthesize transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) ions.
c. to characterize Schiff base ligands and their transition metal complexes by CHN analyses, UV-visible, FTIR and lH NMR spectra analyses.
d. to detennine the molar conductance values of the synthesized transition metal complexes.
5
CHAPTER TWO LITERATURE REVIEW
2.1 Scbiff base ligands containing NS-donor atom
Schiff base ligands are able to coordinate metals through imine nitrogen and other group.
Ketones also tend to fonn imines but the reactions tend to occur less readily than with aldehyde. Nowadays, active and well designed Schiff base ligands are considered "privileged
ligands". In fact, Schiff bases are able to stabilize many different metals in various oxidation states, controlling the perfonnance of metals in a large variety of useful catalytic transfonnations (Cozzi, 2004).
The Schiff base ligands containing NS-donor atoms also acted as bidentate, tridentate and pentadentate ligands. Isomeric bidentate ligands having nitrogen-sulfur donor sequence were prepared by condensing S-benzyldithiocarbazate (SBDTC) with 5-methyl-2-furaldehyde to produce NS ligand (Figure 1) and with 2-furyl-methylketone for NS' ligand (Figure 2) (Tarafder et a/., 2002b).
Figure 1: Chemical structure ofS-benzyl-~-N-(5-methyl-2-furylmethylene) dithiocarbazate (NS)
6
II
Figure 2: Chemical structure ofS-benzyl-~-N-(2-furylmethylketone)dithiocarbazate (NS')
Schiff base ligands derived from S-benzyldithiocarbazate with 5-methyl-2-furyldehyde (Figure I) have shown highly cytotoxic against leukemia cells (CEM-SS) when combined or fonned complexes with lead, Pb(U) (Tarafder et al., 2002).
According to Joshi and his co-workers (2002), the presence of transition metal in human blood plasma indicates their importance in the mechanism for accumulated storage and transport of transition metals in living organisms. Transition metal complexes playa key role in biological system such as cell division, respiration, nitrogen fixation and photosynthesis.
S-methyldithiocarbazate (SMDTC) exists in tautomeric fonns through the loss of thiolo protons (Scheme 2). For these reason, both Schiff bases behaved as uninegatively charged bidentate ligands by coordinating through the thiolo sulfur and the azomethine nitrogen (farafder el al., 2002a).
x ¥
SCH3 X SCH3_N-N--{
..
_N-N=<S SH
y (a) y (b)
Scheme 2: Tautomeric fonns. (a) Thione fonn. (b) Thiolo fonn. NS": X = CH3, Y = H;
NS"': X
=
H, Y = CH37
3)
iously reported some metal complexes of the pentadentate N3S2 ligand (Figure 3 (a) R
=
derived from 2,6-diacethylpyridine and S-methyldithiocarbazate. In addition,
·tution of the methyl groups on the sulfur atoms by benzyl groups in the ligand readily vide the pentadentate ligand (Figure 3 (b) R = SCH2Ph) (Ali et
at.,
2003).H3C CH3 H3C CH3
I I I I
H, ...,N
N N, ... H
N ... N
N N,
N
RAS SAR R),lSH HSJl. R
(a) (b)
Figure 3: The thione (a) and the thiol (b) forms ofH2SNNNS (R = SCH2Ph)
2.2 Schiff base ligands containing NS-donor atom and their transition metal complexes
Transition metal complexes containing Schiff base ligands have been extensively studied in bioactivity areas or field. Researchers in this area have been continuing the syntheses of new nitrogen-sulfur donor ligands through the condensation reaction with various aldehydes and btons. 'The number of ligands synthesized continues to increase because of the interesting observation that different ligands show different biological properties, although they may differ only slightly in their molecular structures (Chew et
at.,
2004).A bidentate Schiff base ligands derived from S-methyldithiocarbazate (SMDTC) with 2
ftuylmethylketone to form (NS) S-benzyl-~-N-(2-furylmethyl ketone) dithiocarbazate and
8
5-methyl-2furaldebyde (NS') to form S-benzyl-p-N-(5-methyl-2-furylmethylene)
.lthi4:>ea1rbal~te and their metal complexes have been synthesized (Figure 4) (Tarafder et al.,
M
=
Cu2+, Ni2+, Zn2+X = CI-, CH3COO
(a) (b)
Figure 4: Synthesis
ofci+,
Ni2+and Zn2+ complexes from S-methyldithiocarbazate with (a) 2-furylmethylketone (b) 5-methyl-2-furaldehydeAccording to Joshi and his co-partner (2002), the presence of transition metal in human blood plasma indicates their importance in the mechanism for accumulated storage and transport of
transition metals in living organisms. Transition metal complexes playa key role in biological system such as cell division, respiration, nitrogen fixation and photosynthesis.
The metal complexes of these uninegatively charged bidentate Schiff base ligands with cadmium (Cd2) , lead (Pb2) and cobalt (C02) have been prepared and characterized (Chew et aI.,2004).
9
Abs. ethanol Resulting clear
+
KOH ligand solution+
MX2nHzONS ligand
-nHzO
Heated at 90°C Cooled in ice-bath
M = Fe2+, C02+, Pd2+, Cd2+, Sn2+
X = Cl-, CH)COO
n =2, 3
Scheme 3: Synthesis ofPd2
+,
Sn2+, Fe2+, Cu2+, C02+ and Cd2+ complexes from S-benzyldithiocarbazate with NS".·"'lllrth.F"rnI,nl'P. the capacity of sulfur donor centers in mixed hard-soft ligand system to stabilize 11D1OOmITIOn oxidation states, to generate unfamiliar coordination number in the resultant
""'Int::i'tinn metal complexes and to take part in diverse type of redox reaction with both
. "'1""11... and electrochemical, is recognize (Rana el al., 2002). A coordination chemistry of has continued to attract attention in recent years due to its presence in several U IIOlOl21cat systems. For examples, a mononuclear Mn(lII) centre was found in the active site
some enzymes that display superoxide dismutase activity (John el al., 2005).
Schiff base ligands containing ON-donor atom
A
new tridentate ligand containing ONN-donor atom has been reported by Leovac (2004).Pv1l'ittl,\YII thiosemicarbazone has been synthesized from the condensation reaction of aqueous
or alcoholic solutions of pyridoxal and the corresponding semicarbazide derivative. The structural fonnula of pyridoxal semicarbazone has shown as in Figure 5.
10
x =
0-+ PLSC, X=
S-+ PLTSCFigure 5: Structural formulas of pyridoxal semicarbazone
Schiff base ligand containing ONN-donor atoms has been reported (Affan et al., 2005).
Figure 6: Structure of2-acetylpyridinebenzhydrazone
hydrazones Schiff Base ligands, RR'C=N-NR'R"', can acts as herbicides, insecticides, ...:m('toc~lae:s, rodenticides, plant growth regulators, sterilants for houseflies. In analytical
" JelTlistlry, hydrazones find applications as multidentate ligands (Figure 7) for transition
. lCtalls in colorimetric or fluorimetric determinations (Monfared et al., 2007).
Figure 7: Schiff base ligands
11
_N
lllerallv. the electronic and structural properties of the ligands play an important role in the properties (Pouralimardan et al., 2006). For example, non-symmetrical salen-type (Figure 8a) have some similarities to the product of salicylaldehyde and condensation (Figure 8b). While salen-type ligands act as tetradentate _ting agents, because of short N-N bound and molecular conformation. Pouralimardan his fiiends expected that benzhydrazone to act mainly as tridentate chelating ligand or illBdenUiIte bridging ligands.
n N~
OH
HO~R
(a) (b)
8: Similarity between a non-symmetrical salen-type ligand and benzhydrazide Schiff base ligand
Transition metal complexes containing ON-donor atoms
analytical chemistry hydrazones find application by acting as multidentate Jigands with .msiltion metal group. Various studies have also shown that the azomethine group having pair of electron in either a 1t or
sl
hybridized orbital on rigonally hybridized nitrogen considerably biological importance (Pouralimardan et al., 2006).12
r1
[MnCl(L1 )(H20 )2][MnCl(L2MH20)2]
x~.>-)I~
[MnCl(L3)][MnCl(L4)]
yz °
[MnCI 2(H20)(LS)]Y
HLI: Z = C-OH, Y = OCH3, X = H HL2: Z = C-OH, Y = OH, X = H HV:Z=C-OH, Y=H, X=H HL4: Z = C-OH, Y = H, X = Br
LS:Z=N, Y = H, X=H
Scheme 4: Metal complex synthesis
.rticl~llaJQ' ,a large number of transition metal complexes of Schiff base ligands derived from
lie
condensation of salicylaldehyde and it derivatives with various primary amines becomes• hot topics of contemporary research (Li et aI., 2007). The use foreground of such metal
I< is also promising such as acting as single-molecule magnets (SMMs), as
" n-j'inel-;cellt probes, as catalysts for specific DNA and RNA cleavage reactions, and also as an
IIKoYI II'V -" inhibitor against urease and xanthine oxidase (XO).
Figure 9: The structure of Cu complex with ligand of salicylaldehyde and glycine
13
-Visible IIQmpleXI=S
CHAPTER THREE MATERIALS AND METHODS
Researcb Metbodologies and Framework
the chemicals were purchased from Fluka, Aldrich or J. T. Baker. All the solvents were and dried by standard methods. Schiff base ligands and their transition metal _'JeXI~ were characterized by CHN analyses, UV-visible, FTIR and I H NMR spectra
CHN analyses were recorded with FlashEA 1112 Series CHN elemental analyzer at
~UMAS. Infrared spectra were recorded as KBr disc using Perkin Elmer Spectrum GX .lII1er-'Transform Spectrometer (4000-370 cm-') at UNlMAS. IH NMR spectra were
"~1Prl in chloroform (CDCb) solution on a Jeol 500 MHz FT-NMR spectrophotometer at
~,"U"'U'"l.~. UV-Visible spectra were recorded with chloroform on a Perkin Elmer Lambda 25 Spectrophotometer at UNIMAS. Molar conductance of transition metal are measured at room temperature using Jenway 4510 conductivity meter at
Schiff base ligands were synthesized py condensation reaction. The first ligand, 2
was synthesized by condensation reaction of 2
-.euzo1ylp:yridline and 2-hydroxybenzhydrazide in absolute ethanol in 1: 1 mole ratio. The _ :ond ligand, N,N'-bis(2-thiophene carboxaldehyde)-I,2-ethylenediamine was also prepared the similar procedure using ethylenediamine and 2-thiophene carboxaldehyde in 1:2 mole
14
