preparation, structural characterization, biological and solid state

PREPARATION, STRUCTURAL CHARACTERIZATION, BIOLOGICAL AND SOLID STATE CONDUCTIVITY STUDIES OF SOME COORDINATION POLYMERS OF POLY SCHIFF BASE.

V . B. B a d w a i k and A . S. A s w a r *

Department of Chemistry, Sant Gadge Baba Amravati University, Amravati 444 602. E-mail: aswar2341(a).rediffmail. com

ABSTRACT Reaction between 2,4-dihydroxy-5-acetylacetophenone

and

thiocarbo-

hydrazide in equimolar ratio leads to the formation of new polymeric chelating ligand (PSB). This ligand reacts with metal salts of Ti(III), VO(IV), Cr(III), Mn(III), Fe(lII) and Zr(IV) to give coordination polymers of types [ ML.xH 2 0] n . All these polymeric complexes were characterized by 1R and electronic

spectra,

elemental

analysis,

thermogravimetry

and

magnetic

susceptibility measurements. IR spectral data confirm the coordination of ligand through the azomethine nitrogen and the phenolic oxygen atom to the metal ions. Presence of a coordinated water molecule in the complexes was demonstrated by thermogravimetry. TG data have also been analysed for kinetic parameters. The D.C. electrical conductivity of the complexes was measured in their compressed pellet form over 313-403 Κ temperature range. The

D.C.

electrical

measurements

show

that

the

compounds

are

semiconductors with moderate activation energy 0.17 - 0.70 eV and their conductivity increases with increasing temperature. Antibacterial activities have also been tested for these complexes.

INTRODUCTION Coordination

polymers having good

thermal

stability and

catalytic

activity have enhanced the development of polymeric materials from both

387

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Vol. 27, No. 6, 2007

Preparation, Structural Characterization Biological and Solid State

polymeric and monomeric ligands. It was only a few decades ago that polychelates

derived

from polymeric

ligands and transition

metal

ions

attracted the attention o f many investigators /1-3/. An efficient method for synthesizing such polymers consists in the introduction o f the inorganic component either as chemically bound or as a filler into the polymer. Depending on their structures, metal chelates of polymers can be used as catalysts /4/, high temperature and flame resistant fibers 151, semiconductors /6,7/, ion exchanging resins 111 and for agricultural purposes /8/. The coordination polymers, i.e. metal complexes derived from polymeric coordinating ligands, may also enjoy such advantageous features, as these complexes are generally thermally stable, insoluble in common solvents and have multiactive sites available within the molecule. The chemistry

of

carbohydrazide and thiocarbohydrazide, H 2 N-HN-CX-NH-NH 2 ( X = Ο or S ) compounds and some o f their derivatives has been reviewed by Kurzer and Wilkinson 191. Both hydrazine groups o f these compounds display normal reactivity towards carbonyl compounds and are expected to yield mono- and dihydrazone

derivatives which contain Ν, Ο and S donor atoms; the

derivatives can therefore function as suitable ligands for transition metals. Interestingly,

the

coordination

chemistry

of

the

corresponding

carbohydrazide derivatives is less explored /10/. Thiocarbohydrazide,

a

diamine, upon condensation with resdiacetophenone should give symmetrical polymeric

1,5-dithiocarbohydrazone.

Keeping

in

view

the

various

possibilities o f interaction of this polymeric Schiff base ligand with metals, efforts

were

undertaken

to

investigate

the

synthesis,

spectroscopic

characterization, thermal studies, semiconducting behaviour and antibacterial properties o f the polymeric thiocarbohydrazone Schiff base and its complexes with Ti(III), VO(IV), Cr(III), Mn(III), Fe(III) and Zr(IV) ions.

EXPERIMENTAL All the solvents used were distilled prior to their use. Titanium trichloride (anhydrous), vanadyl sulphate pentahydrate, chromium chloride hexahydrate, ferric chloride (anhydrous) supplied by S.D's Fine Chemicals, Mumbai were used for synthesis. Thiocarbohydrazide, manganese (III) acetate dihydrate, zirconium acetate and 2,4-dihydroxy -5-acetylacetophenone were synthesized by literature methods /11-13/.

388


Reviews in Inorganic Chemistry

Badwaik and Aswar

Synthesis of Polymeric Ligand DHATCH 2,4-dihydroxy-5-acetylacetophenone

(DHA)

(3.88 g, 0.02

mol)

was

dissolved in 20 ml ethanol while heating on a water bath. To this solution, a EtOH - D M F (60:40 v/v; 20ml) solution of thiocarbohydrazide (TCH) (2.12 g, 0.02 mol) was added drop-wise with continuous shaking and the reaction mixture was refluxed on a sand bath for 2h. The golden brown solid mass obtained was filtered, washed with ethanol and petroleum ether and dried in vacuo (yield 78 %, m.p. 294 °C). The reaction scheme is as follows:

OH

HO

HaN-HN-C-NH-NH, 0= C

C= Ο

I CH.

Reflux

2h

S

CH, (DHA)

(TCH)

Fig. 1: Scheme I

Preparation of the Polymeric Complexes The metal polychelates were prepared by following general procedure. Equimolar quantities of metal salt and ligand were dissolved separately in hot ethanol (20 ml) and D M F (20 ml) respectively and mixed in hot condition with constant stirring. The reaction mixture was refluxed on sand bath for about 3-5h. On cooling, a coloured complex precipitated out; it was filtered, washed with DMF and ethanol. Digesting these complexes on a water bath in DMF purifed the obtained crude mass. Finally all these complexes were dried in an air oven at 80 °C.

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Physical measurements Elemental analysis (C-H-N) was carried out on Carlo Erba 1106 analyzer at Microanalytical Laboratory, CDRI, Lucknow (India). Sulphur was estimated as barium sulphate by Messenger's method. Metal contents in the complexes were determined by standard methods after decomposing the organic matter with a mixture of HCIO„, H 2 S0 4 and HNOj (1:1.5:2.5) /14/. IR spectra were recorded on a Perkin Elmer-RX-I spectrophotometer using KBr pellets. 'H NMR spectrum of the ligand was recorded in mixed solvent CDC13 + DMSO on a JEOL GSX-400 spectrometer. Reflectance spectra of the complexes were recorded in the range 1200-200 nm (as MgO) on a Beckman DK-2A Spectrophotometer. The magnetic susceptibilities were determined at room temperature by Gouy's method using Hg [Co(NCS) 4 ] as a calibrant. A double-ended, one side sealed tube with zero diamagnetic susceptibility was used for measuring the magnetic suseptibility, and diamagnetic corrections were made using Pascal's constant. The solid state D.C. electrical conductivity of the compounds was measured using a Zentech electrometer over 313-403 Κ temperature range. The sample was pressed into circular discs of 12 mm diameter and 2 mm thickness at a pressure of 5 ton cm"2. Thermogravimetric analyses of the compounds were studied in the temperature range 40-700 °C on Perkin -Elmer TG-2 thermobalance in ambient air with a heating rate of 10 °C min"1. The antibacterial activity of the ligand and complexes was studied by disc diffusion method against the bacteria Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa and staphylococcus aureus.

RESULTS AND DISCUSSION The complexes are coloured solids, air stable for a long time and insoluble in common organic solvents, but form suspentions in DMF and DMSO. The complexes decompose without melting when heated above 330 °C. The analytical and physical data of the complexes are presented in Table 1. The analytical data of the metal complexes indicate that the complexes have 1:1 metal:ligand stoichiometry. The reaction of resdiacetophenone with thiocarbohydrazide afforded a product as shown by Scheme I. Its "H NMR spectrum shows signals at (6 in ppm) 12.42 s (OH), 11.40 s (NH) and 3.18 s (CH3). The singlets observed at δ 7.25 and 7.73 ppm may be assigned to


υ _ Π fN» fN Ο β Τ Ο ο Ο ο χ χ χ χ — ON οο ON 2 ε NO Ο Ό "t vi f i ON fN

Chemistry

0.708

0.660

in Inorganic

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Reviews

0.220

and Aswar

Electrical Conductance

Badwaik

— ο ΤΛ — Π oo f^ fN fN CN fN Ο CN Ο Ο Ο b b b b b b b Ο b b b b Χ χ χ X χ x χ X χ X χ χ χ X VI ο VI Rm — fN Tf- VI NO r-; V> oo v> V> Ρ ΤΊ NO OO NO NO FN rn rn V ) TF r - Κ NO fN Tf VI FN NO RN CI ON

b

υ -w

-—* , Ν -—. fN r - fN τΐ· m NO Ο ON fN fN NO — NO r - — — CN — Ρ Ρ ro rn Ρ 00 m fN CN fN —; Ο m fN ""1 (Ν (Ν 00 οο ON oo oo oo od oo oo NO NO r^ Κ Κ T-^ •—^

ON Ρ

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s s

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RR ON

CS Β

"Λ Β 4> ε ν Ξ Ξ

TT

OO ON

Ν Ο ON NO fN FN

NO CN

v>

Ο NO

fN

*—'

fN fN fN Ν—'

oo fN VI ON —; Ο ""> r>"> o< rΓ Ο ΓΟ SΓΝ Ο FN

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ΓON —

s

TT

TT

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-

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«T

ο

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FN

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ON Ο

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b — fN fN

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Ο

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complexes

composition of the

Proposed U ΙΛ

S

CNJ

Ο

π

χ

5 A,, 5 B,-» 5E and LMCT transitions, respectively, towards square pyramidal geometry around Mn(lII) ion. The electronic spectrum of Zr(IV) complex does not show any dd transitions.

Magnetic m o m e n t A magnetic study of the complexes was carried out to investigate the valency and stereochemical aspects of the central metal ion. Ti(III) and VO(IV) complexes

show a magnetic moment

1.69 and

1.67

B.M.

respectively, indicating the presence of one unpaired electron. The Cr(III) complex has a magnetic moment 3.92 B.M., in accordance with the spin-only value for three unpaired electrons in an octahedral geometry /18/. The magnetic moment of Mn(III) complex is found to be 4.87 B.M., showing the presence of four unpaired electrons. The high-spin octahedral geometry is suggested for the Fe(III) complex by its magnetic moment value 5.84 B.M., corresponding to five unpaired electrons. The Zr(IV) complex is diamagnetic as expected .


Vol. 27, No. 6, 2007


Electrical conductance studies According to thermal decomposition temperature, electrical conductivity of the complexes were measured in their compressed pellet form over a range of 313-403

Κ temperature.

Figure 2 illustrates a typical

temperature

dependence of the electrical conductivity during the heat treatment. By analyzing the shape of In σ = f (10 3 / T) graphs (Fig. 2), useful information

-82

• DHATCH -8.6

• Ti(lll) DHATCH i VO(IV) DHATCH

-9

χ Cr(lll) DHATCH * Mn(lll) DHATCH

-9.4

• Fe(lll) DHATCH -98

+ Zf(IV) DHATCH

-10:2

J G

-10.6

β

1 -11

-11.4

-11.8

-12.2

-12.6 2.4 -13

2.5

26

2.7

2.8

2.9

3

3.1

3.2

3.3

ioYr (K1) Fig. 2: Temperature dependence of log"

regarding the processes occurring in the investigated complexes during the heat treatment can be obtained. The Arrhenius equation can be expressed as σ =

σ 0 exp

394

(-Ea / KT), where σ 0 is the constant

depending


on

the

Badwaik and Aswar

Reviews in Inorganic Chemistry

s e m i c o n d u c t i n g nature, Ea is the thermal activation energy for the electrical conduction and Κ is the Boltzman Constant. A plot of Ιησ versus 1000/T yields a straight line, w h o s e slope can be used to d e i c i m i n e the thermal activation

energy

of

the

complexes

/19/.

Figure

2

shows

a

positive

temperature c o e f f i c i e n t of the conductivity, in a c c o r d a n c e with conventional semiconducting

behaviour

/ 20/

where

the

conductivity

increases

exponentially with increasing temperature. T h e increase starts when charge carriers

have

enough

activation

energy.

Also,

during

the

increase

of

temperature the mobility of these carriers increases. T h i s is a property o f typical s e m i c o n d u c t o r s . In addition to this, the values b e t w e e n 3.09 χ 10"12 7.01 χ 10" 8 (Ω"' cm"') indicate the semiconducting nature of the c o m p l e x e s at room t e m p e r a t u r e /2I /. T h e thermal activation e n e r g y lies in the range 0.17 — 0.70 eV.

Thermal Studies T h e thermal d e c o m p o s i t i o n behaviour of the ligand and its c o m p l e x e s was studied by thermogravimetric analysis in the t e m p e r a t u r e range 40700"C. T h e t h e r m o g r a m s of D H A T C H and its metal c o m p l e x e s are shown in Fig. 3 and s h o w well-defined stages of d e c o m p o s i t i o n pattern. T h e r m o g r a m of Ti(lII), F e ( I l l ) and Z r ( I V ) c o m p l e x e s s h o w weight loss c o r r e s p o n d i n g to two lattices and one coordinated water molecule in the r a n g e 9 0 - 2 2 0 °C. [ % wt. loss, obs./calc.; Ti(III) : 9.18/9.01, Fe(III) : 8.94/8.83, Z r ( I V ) : 8.30/8.15 for lattice water and Ti(lII):4.99/4.95, Fe(III):4.89/4.84, Z r ( I V ) :4.57/4.44 for coordinated water] T h e weight loss up to 110 °C indicates the p r e s e n c e of one lattice water molecule in each of the V O ( I V ) and Cr(III) c o m p l e x e s [% wt.loss

, obs./calc.:

VO

(IV)

:5.30/5.18,

Cr(lll):

4.78/4.66]

1221. T h e

t h e r m o g r a m of C r ( l l i ) c o m p l e x shows two distinct regions: 120-180 °C and 2 0 0 - 2 7 0 °C, c o r r e s p o n d i n g to the loss of one coordinated water and one chloride m o l e c u l e respectively . [% wt. loss, obs./calc.; For H ; 0 : 4 . 9 8 / 4 . 8 9 and CI: 10.31/10.14 ] T h e Mn(III) c o m p l e x is almost stable up to 190 °C, indicating a b s e n c e of any water molecule. T h e weight loss at - 2 8 0 °C may be assignable to the loss of an acetate group [% wt.loss, obs./calc.: 15.81/15.69], In T i ( i l l ) , Cr(III), Fe(III) and Zr(IV) c o m p l e x e s , a rapid weight loss w a s observed between 3 0 0 - 4 0 0 "C, the quantitative elimination of ligand took place at ~ 6 5 0 "C, followed by complete d e c o m p o s i t i o n of the c o m p l e x e s to their respective metal oxides. T h e thermal degradation of the ligand molecule


182.03

194.38

259.78

8.68 χ ΙΟ -4

14.36

17.09

13.86

25.73

19.90

13.69

23.65

23.30

9.01

•a ο JZ ω 2 -a Ο •> ο ΖI C

&

Ο(Ν ο rj «/— Ν Χ (Ν υ Ο Η (Ν

m

(Ν (Ν Ο •f

οfN Χ Ζ

·«•

10.55

21.65

17.31

22.35

294*

Activation Enei (kJmoF1] Compound

Μ

263.09

172.40 249.60

17.98 20.84 16.83

10.34

21.98

MP*/Half Decomp. Temp. (°C)

ιη m ο Ό οο Ον Μ" ΓΟ ι/Ι VO τΤ ci ΓΟ ΓΟ ΓΟ ΓΛ

ω

9.82

11.06 11.78

*S Χ

"as

b χ m rf; (Ν 19.69

178.80 250.23

b χ οο νο ΓΛ

8.44

168.63