Download Mixed ligand transition metal(II) complexes of Knoevenagel

Indi an Journa l of Chemi stry
Vol. 44A . Ap ri l 2005 . pp. 093-699
Mixed ligand trans ition metal(II) co mplexes of Knoevenagel condensate-~­
ketoesters with 1,2-diaminobenzene: Synthesis, structural characterization ,
electroche mical behaviour and antimicrobial study
Raman "' , C Than garaja & S John son Raja
Departmen t of Chemi stry. VI-INS College. Virudhunagar 620 00 I , India
Email: drn_rarn an@y ahoo.co.in
Reeeil'ed 8 OrcellliJer 200-1 ; rel'ised 4 Feb/'llwy 2005
New Schill base mi xcd li ga nd tra nsiti on meta l co mplexes of th c compos i ti on. [ML(DI3 )1 ]C I1. w herc M =C u(II ). Ni (IJ ).
Co(ll ) and Z n( II ): L=Knoc \'cn agc l c o nd e n s a t e- ~ - k c t ocs t e r deri ved fro m I -hydroxy bcnzaldchyde and meth y l cs tcr o f 3ox obutan oic acid (I-IMOA)/c th y l cs ter of 3-oxobutan oic acid (I-I EOA )/N -pheny l-2-oxobu tanam ide ( I-IPOB ) and 1.2diaminobenLcne( DB ). were synthes izcd. T hey were characteri zed on th e basis of elcmcntal anal yses. magncti c
suscepti bil it y. FAB -mass. c lec tron ic absorpti on spec tra. IR. 11-1 MR.
NMR and ESR data. All th e co mplexes ex hi bi t
oc ta hedral geometry . Th eir magn eti.:: suscepti bili ty measurements and conductance data pro vidc evidence ror the monom eri c
and 1: 2 electrolyti c natures or th e co mplexes. respec ti vely. T he electroc hem ica l behavi our, thc anodic and cath odic potenti al
and th e num ber of electron tran sfer we re ca lculated using cyc lic vo ltammogra m. Thc antimicrobial acti vities o f th e li gand
and it s comp lexes ha vc becn studi ed by screening th e co mpounds again st vari ous microorgani sms (both Gram-pos iti ve and
Gram-negat i ve bac teria ) and the result s have been compared wi th the standard drug. ampi cillin . Th e data showed that th e
co mplexes wcre hi ghly act i ve th an that of th e free ligand and th e standard.
"c
fPC Cod e: Inl.Cl
7
C07F 1/08: C07F 15/04: C07 F 15/66: C07F 3/06
The coo rdinati on co mpl exes of 2,4-pentanedi one and
its deri vat ive Iigands have aroused co nsiderab le
interest ove r (ew decades ' ·'. It is we ll kn ow n th at the
enoli c proton of th e predomin ant ly ex istin g enol fo rm
of 2,4- pentan ed ione undergoes di ssociat ion to form a
number of complexes with metal ion s. Condensing
the active m e th y l e n ~ group of th e 2,4-pentanedi one
with aldehyde can prohibit th e for mati on of th e enol
tautomer (kn ow n as Kn oevenage l condensati on). 1,2Diaminobenzene is a va luabl e startin g materi al for the
sy nth esis of a large number of fu sed rin g sys tem,
mos t notab ly be nzimidazo les, several deri vati ves of
wh ich have bee n reported to possess a va ri ety of
biological acti vities4 .5 . There is considerab le interest
in th e study of mi xed li ga nd coord inated co mpl exes
of transiti on metals in view of th eir unusual magnetic
properti es, catal ytic ac tl VI ties and biochemical
behav iour6 -' ). Moreover, the stru ctural characteri zation
of the mi xed li gand complexes may be interesting due
to va ri ous rati os of coordinations like I: I, I :2, 1: 3,
etc. In co ntinu ati on of our studi es on such biologically
importan t a,~- un s aturated dicarbonyl compo und s, we
herein report the synthesis of so me new mi xeJ li ga nd
complexes of tran sit ion metal(ll ) ions with 1,2-
diami nobe nze ne
~- ketoester.
and
Kn ovenagel
co nden sate
Materials and Methods
All reactions and ex peri menta l manip ulati ons were
carri ed out in air. Anhydrou s grade meth anol and
DMSO were obtained from Fisher Sc ientifi c. l .2Diaminobenzene was obtained fro m SDS Fine
Chemicals
and
rec rysta lli zed
befo re
use.
Microanalytical data, IH NMR, 1.1C NM R and FABmass spect ra of th e compounds were performed at th e
Regional Sophi sticated Instrumen tati on Centre,
Central Drug Research Institute, Luck now (RSIC.
C DR I). The FAB-mass spectrum of the comp lex was
recorded on a Jeo l SX 102/DA-6000 mass
spectrometer/Data system usi ng Argon/Xenon (6 k V.
10 mA) as th e FAB gas. The accele rat ing vo ltage wa.
10k V and the spec trum was recorded at room
temperature using 3-nitrophenylcarbin ol as th e
matrix. The IR spectra of the sampl es were reco rded
on a Perki n-Elmer 783 spectrophotometer in 4000200 cm· 1 ran ge using KBr. The UV-vi s spec tra were
recorded on a Shi madzu UV -1 60 I spec trophoto meter.
The X-band ESR spectra of the comp lexes were
694
INDIAN J C1-IEM. SEC A . APR IL 2005
reco rded in DMSO at 300 K and 77 K at liT,
Mumbai , using TC E (tetracyanocth ylene) as the gmark er. Magnetic susceptibi lity measurements of the
comp lexes were carri ed out using Guoy balance using
copper sulphate as th e calibrant. Electrochemical
studies were carried out using EG&G Princeton
App li ed Research Potentiostat/Galvanostat Model
by
M270 software.
CV
273A, controlled
measurements were performed using a glassy carbon
workin g electrode, platinum wire auxiliary electrode
and
an
AgiAgCl
reference
electrode.
Tetrabutylammoniumperchlorate (TBAP) was used as
the supportin g electrolyte. All solutions were purged
with N2 for 30 min pri or to each set of ex periments.
The molar conductance of th e complexes was
measured in DMSO solution using a 305 Systronic
conductivity bridge.
Antibacterial activity
The in vitro biological scree nin g effects of the
investi gated compounds were tested against the
bacteria Klebsiella pneullloniae, Staphylococcl/s
aI/reus, Bacilllls subtilis, Sallllon ella typhi and
Esch erichia coli by the well-diffusion method, using
aga r as the nutrient medium. The test solutions were
prepared by dissolving the compounds in DMSO. In a
typical procedure, a well was made on the agar
n edium inoculated with microorganisms. The well
was filled with the test solution using micropipette
and the plate was incubated at 35°C for 24 h. During
this period, the test solution was diffused and the
grow th of the inoculated microorganisms was
affected. The inhibition zone developed on the plate
was measured.
Synthesis of Knoevenagel condensate
~-diketoes ters
The
Knoevenagel
condensate
~-ketoes ters
(HMOA/HEOA/HPOB) were prepared by the
following procedure '0: equimolar quantity of
I-hydroxybenzaldehyde and ~-ketoes ter was taken in
a 100 mL co nical flask and cooled for I h under
freezing mixture. After cooling the solution, I mL of
piperidine was added dropwise with constant stirring.
The mixture was kept under freezer for 24 h, the
prod uct separated was filtered and recrystalli sed 111
ethan ol.
Sy nthesis of mixed ligand complexes
The compl exes were prepared by mixing th e
appropriate
molar quantity of
Knoevenagel
co ndensate ~-ketoesters , 1,2-diaminobenzene and the
metal salts using th e following procedures.
Synthesis of copper complexes
An ethanolic so luti on ( 10 mL) of Kn oevenagel
condensate ~-k e to es t e r [HMOA (1. 1 g, 0.005
mol)/ HEOA ( 1. 17 g, 0.005 mol)/HPO B( 1405 g. 0.005
Illol)] was stirred with th e eth anolic .;;oluti on (5 mL )
of copper ch loride (0.670 g, 0.005 M) fo r ca. 5 h. To
th e above mixture, an ethanolic soluti on (5 mL) of
1,2-dialllinobenzene ( 1.08 g, 0.0 I mol) was added .
and the stirring was continued for ca. I h. The solid
product obtained was filtered an d was hed with
ethanol.
Synthesis of nickel complexes
An ethan olic solution ( 10 mL) of Knoevenagc l
condensate-~-ketoes ter
[H MOA (l. 1 g,
0.005
mol)/HEOA (1.17 g, 0.005 mol)/HPOB ( 1.405 g, 0.05
mol)] was stirred with th e ethanolic so luti on (5 mL)
of nickel chloride (1 . 188 g, 0.005 Illo!) for ca. 5 h. To
the above mixture, an ethanolic solu tion (5 mL) of
1,2-diaminobenzene (1.08 g, 0.0 I mol) was added,
and the stirring was continued for ca. I h. The solid
product obtained was filtered and washed with
ethanol.
Synthesis of cobalt complexes
An ethanolic solution (10 mL) of Knoevenagel
condensate ~-ketoester [HMOA (1.1 g, 0.005
mol)/HEOA (1.17 g, 0.005 mol)/HPOB (1.405 g,
0.005 mol)] was stirred with the ethanolic soluti on
(5 mL) of cobalt chloride (1.189 g, 0.005 M) for ca. 5
h. To the above mixture, an ethanol ic solution (5 mL)
of 1,2-diaminobenzene (1 .08 g, 0.0 I mol) was added
and refluxed for I h. The content was cooled and
filtered , then washed with hot ethanol.
Synthesis of zinc complexes
An ethanolic solution (10 mL) of Knoevenagel
g,
0.05
condensate ~-ketoes ter [HMOA( 1.1
mol)/HEOA(1.I7 g, 0.005 mol)/HPOB(1.405 g, 0.005
mol)] was stirred with the ethanolic solution (5 mL )
of zinc chloride(0.68 g, 0.005 mol) for ca. 5 h. To the
above mixture, an ethanolic solution (5 mL) of 1,2diaminobenzene (1.08 g, 0.0 I mol) was added, and
the stirring was continued for ca. l h. The sol id
product obtained was filtered and washed with
ethanol.
Results and Discussion
All the complexes are air stable, crystalline and
th eir carbon, hydrogen , nitrogen and metal
percentages agree with [ML(DB h ICh where M =
Cu(II),
Ni(ll), Co(ll)
and
Zn(lI );
L =
C' 2H' Z0 4/C IJ H' 40 4/C' 7H' S0 3' The co nductance of th e
chelates supports their 1:2 electrol ytic nature" . The
695
RAMAN 1'1 11 1.: M I XED LI GAN D COMPL EXES OF K NOEVEN AGEL CON D ENSA T E-~-KET OESTE R S
Tab le I- Phys ical and anal yti cal da ta or th e sy nt hesi zed cOlll pounds
Empirica l
formu la
COlllpound
Found (Caled) (% )
------''----- - - -- - -- - -Colour
M
C
1-1
N
CI
Y ield M elti ng/
(% ) Decomp.
point °C
0 1-1
2 15
B ro w n
75
220
I3l'Own
73
205
I3 l'O w n
78
2 ~0
65
2:'15
75
226
L ight
blue
Li ght
blue
L ight
blue
Pin k
82
198
Pin k
69
209
Pi nk
75
2 12
73
233
81
24 1
Co lourless
Colourless
Colourless
208
I 1. 18
( I 1. 13)
10.96
( 10.86)
10. 11
( 10.05 )
10.42
( 10.37)
10.09
( 10. 12)
9.39
(9.36)
10.55
( 10.4 1)
10.22
( 10. 15)
9.48
(9.39)
11 .52
( I 1.4 1)
11 .1 9
( 11 . 14)
10.29
( 10. 3 1)
H
21?
-
0"'-..
1
N I-I 2
M/
=
0/
I
"'-N 1-I 2
( t\ ~ d
ohm~ :
,
nOl~1
~I
Pd l
(IU d )
x I .
phys ica l and an alyti cal data of th e co mpl exes are
shown in Tab le I. Study of magneti c and elec troni c
spectral data is quite in fo rm ati ve in characteri zing the
geometry of the co mpl exes. The mono meri c nature of
th e co mp lexes was co nfirm ed by th eir magneti c
suscepti bility data. In case of Cu(lt) chelates th e
observed mag neti c moment and electro ni c spectra
R
w !.
(Calcd) cm-
65
69
Formula
CI2
H
'tO
Fi g. I - Structure o f th e co mpl ex es IM =C u(II ), Co(l l ). N i(lI ) and
Z n( II ) 1
50.46
(50.48)
5 1.26
(5 1.33)
55.08
(55. 11 )
50. 79
(50.92 )
5 1. 68
(5 1.75)
55.48
(55.53)
50.85
(50.90)
5 1.69
(5 1.74)
55.35
(55 .5 1)
50. 12
(50.32)
5 1.05
(5 1.1 7)
54.85
(54.95 )
4.82
(4.94)
5.06
(5. 17)
4.85
(4 .94)
4.9 1
( ~. 98)
5. 18
(5.2 1)
4.95
(4 .98)
4.89
(4.98)
5.20
(5.2 1)
4.96
(4.98)
4.89
(4.93 )
5.1 4
(5. 15)
4.89
(4.93 )
9.76
(9.82)
9.46
(9. 58)
10.96
( 11.08)
9.87
(9.90)
9. 59
(9.66)
I 1.1 5
( I 1. 17)
9.86
(9.89)
9.58
(9.66)
10.98
( 11.1 6)
9.65
(9.78)
9.5 1
(9.5 5)
11.0 I
( 11.05)
I .SO
12.50
( 12.42)
12.1 0
( 12. 12)
570.95
170.45
534.93
168 .OJ
I I. 2:'1
632.0~
17 1.46
1 . 7~
566. 11
150.35
3. 17
5 8 0. 1 ~
163.00
3. 19
627.20
172.24
566.34
168.54
3.9
580.36
143.40
3.7 5
627.42
167.34
~ .2
572.77
136.23
586.8
142.43
633 .86
139.40
( I 1. 2 1)
12.49
( 12.52)
12. 19
( 12.22)
11.32
( I 1.30)
12.56
( 12.52 )
12. 15
( 12.22)
11.28
( 11.30)
12.34
( 12.38)
12.02
( 12.08)
11.1 7
( I 1.1 8)
suggest a di storted octahedral geometry III terms or
John-Tell er effec t. The proposed stru ctu re of th e
co mpl ex is given in Fig. I.
Electronic a bsorption spectra
The elec troni c spectra of all the co mpl exes show a
broad absorpti on band at ca. 32250-29600 cm,l
region, whi ch is assigned to intraligand charge
transfer transition. In additi on, Cu(lI ) chelates show
bands at ca. 14600-1 5 100 cm· l, whi ch presumab ly
co ntains d-d transition. The band may be due to
2Eg- /T2g tranSItIon, whi ch is ass ignab le for
octahedral structure. Absence of any band below
10,000 cm· t rul es out the possibility of tetrahed ral
structure for the chelates. The ni ckel co mplexes
ex hibit three weak bands in the regions 24096-22988 .
16 129- 15873 and 12 195- 11 904 cm· 1 whi ch are
ass igned to 3A2g"-7 J TI g( P), JA2g--7JTl g(F) and JA2g--7JT2g
transiti ons, respecti ve ly whi ch fa vour octah edra l
geo metry . This is furth er supported by th eir magnetic
moment va lues, whi ch are in the range of 3.20-3. 17
B.M. The cobalt co mpl exes ex hibit three bands in th e
regions I 1627-11494, 16800-1 6 129 and 18500- 18000
cm· l, ass igned to 4T I g( F)--7 4 T2g , 4Tt i F)--74A 2g(F) and
4Tlg(F)--74T2g(F) transitions an d th e magneti c moment
I NDI AN J C H EM, SEC A . APRIL 2005
696
Tabl e 2 -
101.1
OH
L1C NMR spec tral data o f th e I Zn(l I MOA )( D[l)~ ICl ~ co mpl ex
;9'
" 2N
1,2'
2 -0""" I ( ' NH2
~, I
I)
Z,
-0
12
OC",
/' I""
"'106
NH,_
2'
J
2'
J
C I2
Valu es
(ppm)
Assignmen ts
Va lues
(ppm)
Assignmen! ;.
26.5
CI
149.6
C IO
195.2
C~
19S.3
CII
li S. I
C.1
30. 1
CI ~
14S.5
C4
147.1
154.6
C,
11 6. 1
C"
C 2,
15S.4
C6
130.S
C.1'
122.2
C7
126.5
Cs
140.5
C9
values fall in the ran ge(3.9-4.2 B.M.), whi ch co nfirms
th e oc tah edral arran ge ment of cobalt co mpl ex.
IR spectra
The IR spectra of all the li ga nds and co mpl exes
under study show broad bands in th e region 30003250 cn,-I . It indicates th at th e pheno li c - OH group
prese nt in th e salicylaldehyde moi ety of the li gands is
not in vo lved in coo rdin at ion. All th e liga nds show a
prominent peak at ca. 1720 cn,-I co rres ponding to
v(C=O) keto group. A sli ght dow nfi eld shift has been
obse rved in the spectra of the complexes. The
observed dow nfi eld shift, go ing from the free ligand
to metal complexes suggests neutral ketonic
coo rdination of carbonyl groups to th e metal. These
results are co mparable to the data reported
elsew here I2 .". Further, the IR spectra of the
co mpl exes show th e band attributed to v(NH 2) of the
coordinated amino group, whi ch appea rs at
wavenumber, t;v>50 cm' l than in the spectrum of 1,2diamin obenzene wherein the nitrogen coo rdination is
obse rved by tracin g a medium intens ity band around
1525- 1535 cm' l. Compari so n with the IR spectra of
the liga nds, the complexes show new ~a nd s. in the far
IR regions 500-450 and 400-350 cm . ass ignable to
M-O and M- stretchin g vibrat ions respectivelyl 4.
i\ lass Silectra
The FAB mass spectrum of [Cu(HMOA)(DB h ]CI 2
co mpl ex shows the molec ul ar ion peak at 570 III/ Z
(C 24 H2S 40 4CuC1 2) and base peak at 107 III/ Z
(C6HSN2). wh ich confirms the stoichi ometry of metal
comp lexes as being of the rML(DB )2]C I2 type.
'1-1 and DC 'i\ IR
The IH
M Rand Uc N M R spectra of the
lZn( HMOA)(DBh]CI 2 were recorded in DMSO-dc, at
room temperature. The IH NMR spectrum shows the
following signal s: pheny I multi plet at 7.34-7.41 8
(1= 1.5 Hz), -C-CH., at 3.50 8, -OCHJ at 2.55 8 and the
- OH at 11 .75 8. A broad absorption around 6.2 8 is
due to the NH 2 pro ton.
The
IJC
NMR
spect ral
data
of
th e
[Zn(HMOA)( DB)2]Cl 2 was give n in Tab le 2. The data
indicate th e prese nce of th e ex pec ted number of
signal s corresponding to the number of chemically
di fferent types of carbon atom present in th e
complex. The signal s at ca. 26.5, ) 95.2, 11 8. 1 and
65 .3 ppm are assigned to meth yl, carbonyl, meth ene
and meth oxy carbon of th e ~- ket oes(e r moiety an d
147, 11 6 and 130 ppm are due to I ,2-diami nobenze ne
signal s of the zinc complex. It is well kn ow n from th e
literature l5 th at the sp.1 hybridi zed carbon abso rbs at
hi gh field region , whereas Sp 2 hybri dized carbon atom
at low field region. The C=O carbon absorbs arou nd
190 ppm and -OCH3 group absorbs slightl y dow nfi eld
than the methyl carbo n due to the des hi elding effec t
of th e directl y attached electronegative oxygen. The
aromatic carbon absorbs usually in the dow n field
region. A sli ght downfi eld shi ft was observed when
compared with that of th e free li ga nd .
ESR spect ral studies
The X-band ESR spectra of the ~o pper complexes
were recorded in DMSO at 300 K and 77 K. The
spectra of all the complexes at 300 K show one
intense absorption band in the hi gh field region and
are isotropic due to dumpling motion of th e
molecules. However, th ese molecules in the frozen
state show four well resolved peaks with low
intensities in the low fi eld region , Fro m the spectra Ai",.
A ll, A1., g is<', gil and g1. were calcu lated and the va lues are
Table 3. The magnetic susceptibility
ooiven in
measure men t revea ls that the copper complexes ha ve
magnetic moment ( 1.72- 1.78 B.M.) corresponding to
697
RAMAN el al.: MIXED LIGAND COMPLEXES OF KNOEVENAGEL CONDENSATE-~-KETOESTE R S
Tabl e :l-
Sp in -Hamil tonian parameters of
A" x 10-4 cm-I
Complex
I C u ( HM OA)(DB) ~ lCI !
A l.x 10-4 cm- 1 Ai", x I 0-1 CIll -
1
in DMSO soluti on
gil
.til.
g iso
,
rr
0!
,
y-
rCu(HM OA)(DB)! JCI !
175 .2:1
58.67
76.66
2.248
2.05 1
2. 152
0.7933
0.6S:l3
0.5-1 1S
ICu(HEOA)(DB)! lCI!
169.S4
72.58
85_75
2.25 1
2.053
2. 13 1
0.7822
0.7 159
0.5S38
rCu (HPOI3 )( DB h ICl!
165_04
49 .55
80.00
2.238
2.049
2. 147
0.7541
0.67 57
n'--:l55
Table 4-The cyclic vo italllnlogram data o f ICu(HMOA )(DBh ICl! (0.01 mol) comp lex in DMSO at 300 K (scan rat e 100 mVsCoup le
Cu( II )/Cu( III )
Cu(II )/Cu(l )
Cu(I)/Cu(O)
l
)
Ep,,( mV)
Epc( mV )
fp" ( ~lA)
fpc (pA)
f p) fp"
- 120.58
-268.40
-955.57
-69.74
-965.70
- 1170.71
58.25
53_14
55.65
6 1.42
86.32
60.28
1.05-1
1_62-1
1.0S:l
determine the cov al ent bonding parameter for the
Cu(l!) ion in various ligand field environments. The in plane a-bonding cova lency parameter, a" is related to
All , gil and 81. accordin g to the foll owing equati on ,
~
a- = -(A II/O.036) + (811-2.0023) + 317(g1.- 2.002 3) +
0.04
...
If the va lue of a "=0.5 indicates comp lete covalent
2
bonding, whi le the value of a =1.0 suggests comp lete
ioni c bonding. The observed value of Cf? is 0.75-0.79.
indicates that the co mplexes have covalent character.
The out-of-plane n -bonding (y-) and in-plan e nbonding (~") parameters are also ca lcul ated from the
following expressions:
C
<II
c....
c....
::::I
U
~" = (811- 2.0023) EI/- 8Aa"
0.1
0.2
-0.6
-1.4
EIV) versus Ag / AgCl
Fig. 2- Cyclicvoltammogral11 of ICu( HMOA)(D I3 )! JCI! at 300 K
the one unpaired electron indicat ing that the complexes
are monomeric and the ESR spectra of Cu(ll ) chelates
do not show any band - 1600 G due to the t,lIls= ±2
tran sition and thi s precl udes the presence of M-M
interacti on 1(,.17.
In axial spectra, the g va lues are related w ith
exchange interacti on co upling constant (G) by the
ex pression G = gll-2IgW2. According to H a thawai 8. 1~,
if the value of C is larger than four, exchange
interaction is negl igible becau se the local tetragonal
axis is mi saligned. For the present copper comp lexes,
the G valu es are 4.73-4.86, whi ch sugges t that the local
tetragonal axis is ali gned parall el or slightly misali gned
and consistent with d// ground state. Electron spin
resonance and optical spec tra have been used to
y2 = (81. - 2.0023) EI/-2Aa2
In the equati on A=828 cm' l for the free ion and EI
is the elec troni c tran sition energy of "E 2g --7 2 T 2g . Th e
observed ~" (0.67-0.7 1) and Y-(0.53-0.58) va lues
indicate th at there is a substanti al interacti on in the in plan e bonding, whereas the out-of-plane bonding is
co mpl etely ioni c. Thi s is also confirmed by th e orbi tal
reducti on factor (KII and K1. ), which was esti mated
from th e si mple relati on
" f.l.2
KII= a-I-'
and
Si gnificant information about th e nature o f bonding
in the complex can be derived from the relative
magn itude of the KII and K1.' In the case of pure a bonding, KII-K1. impli es cons iderable in-plane TIbonding. For th e copper comp lexes th e observed
KII(O.50 -0 .56) and K1.(OAO-OA6) values impl y the
signi fica nt in-plane n -bonding.
I DIAN J C H EM . SEC A. A PRIL 2005
698
Table 5- Ant ibactc ria l activ ity o f the co mpound s by we ll di l"fu sion meth od (Zo ne of inhibiti on in
COIll(l()und/cOlllplex
II MOA
HEOA
HPOB
DB
ICu( H MOA) ( DB h JCI ~
ICu( HEO A) (DB h ICl ~
IClI( HPOB) ( DB )~JC I ~
1Ni( HIvIOA) ( DB )~ JCl 2
INi ( HEOA) ( DB h ICl ~
INi ( HPOB) ( DB)21C1 2
ICo( HM OA) ( DI3 )2 1C1 2
ICo( H EOA) ( DB h ICl 2
ICo( HPOB ) ( DB h ICI2
IZn( HM OA) (DB)~ I Cl2
IZn( H EOA) ( DI3 l2jC I2
IZn( HPOB ) ( Dl3 h 1C 12
Esch crichia
coli
Klcbsiclla
I'l/ clIl/ lOl/ia e
R
6
9
7
16
17
15
10
18
9
6
10
II
15
I:l
I:l
I,,)
16
15
I,,)
12
16
I,,)
II
19
Antimicrobial activity
The in vilro biological sc reenin g effect of the
in ve tigated compounds were tested against
Klebsiella pn ellllloniae, Staphylococclls all reus,
Bacilllls slIbtilis, Sallllonella typhi, and Escherichia
coli. The inhibition zones were meas ured and are
li sted in Table 5. Antibacterial screening data reveal
that the toxicity of metal chelates has increased
co nsiderably as co mpared to their paren t ligands
against the same microorgani sms and under identical
experimental conditions [the MIC (minimum
inhibitory concentration) values of the control against
03
th e growth of Staphylococclls allrells is 1.6x I 0 mol
0
whereas for the ligands are in the range 2.6-3.8x I 0 '
mol , but the copper complexes have the values in the
03
range of 1.4-2 .3x Io mo l]. The increase in th e
activity of the metal chelates may be due to the effect
of metal ions on the normal cell process20022. The
Bocililts
SIII}(ilis
I:l
II
8
14
7
12
23
25
5
6
12
I,,)
21
18
2,,)
13
19
17
12
II
2,,)
9
II
23
2,,)
12
12
19
18
19
18
23
21
9
The
cyclic
vo ltammog ram
of
th e
[Cu(HMOA)(DB h ]C1 2 (0. 1 mol ) complex in DMSO
at 300 K in the potential range +0. 1 to -1.4 Y was
recorded and show n in Fig. 2 and th eir values are
given in Table 4. It shows a we ll defined redox
process corresponding to th e formation of th e quasireversible couple copperCIl )/copper(III ). The rati o of
cat hodic and anodic peak current values indicates that
the co upl e is simple one elec tron transfer process.
These comp lexes also show two quasi-reversibl e
peaks in the negative region which could be assigned
as copper( 11)/copperO) and copperO )/copper(O)
couples.
So llllol/ ella
(yphi
I:l
18
14
17
Elcctrochcmical hchaviour
S((lpll.'·lo(·occlls
allrClls
12
7
I:l
1111ll )
16
I ,,)
I,,)
12
IR
16
15
II
13
13
15
polarity of th e metal ion is cons iderab ly redu ced on
chelat ion, which is mainly because of partiall y
sharin g of its positive charge with the donor groups
and possibly IT-electron delocalisation over th e 'vvhole
chelate rin g. Such chelati on increases th e lipop hili c
character of the meta l complexes whi ch probably
breakdown of permeability barrier of the cel ls
res ulting in interference with normal cell process.
Conclusion
We have sy nth es ized so me mi xed li gand
complexes of Cu(II), Ni(II), CoOl) and Zn(lI ) metal
ions with 1,2-d iaminobenzene and Knovenagel
condensate
B-ketoesters.
They
ha ve
bee n
characterized
by
microanal ytical,
spectral ,
electrochemical and magnetic studi es to es tabli sh th e
proposed octahedral geo metry. The antib ac terial study
shows that th e complexes are hi ghl y act ive than that
of the free Iigands and th e control.
Acknowledgment
The authors ex press their sincere th anks to th e
Head, Departm ent of Chemistry, Principal and th e
Managing Board of YHNSN College, fo r providing
research faci lities and Prof. P Manisankar,
Department of Industrial Chemistry, Alagappa
University, Karaikudi for providing c.y . faciliti es.
One of the authors (CT) expresses hi s since re thanks
to Tami l Nadu Government (DCE) for finan cial
sll pport.
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