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New Metal ComplexesDerived from 1-N-(6-Nitrobenzimidazole-1-carbonylmethyl)-4-(α-naphthyl)-3-thiosemicarbazideXu Pengfei a , Xu Zhuguo b & Wu Shaozu ca Department of Chemistry , LanzhouUniversity , Lanzhou, 730000, P. R. Chinab Lanzhou Medical Collage , Lanzhou, 730000c Central Research Institute of Building andConstruction of M. M. R. , Beijing, 100088Published online: 23 Aug 2006.

To cite this article: Xu Pengfei , Xu Zhuguo & Wu Shaozu (1996) New MetalComplexes Derived from 1-N-(6-Nitrobenzimidazole-1-carbonylmethyl)-4-(α-naphthyl)-3-thiosemicarbazide, Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 26:1, 11-19, DOI: 10.1080/00945719608004242

To link to this article: http://dx.doi.org/10.1080/00945719608004242

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SYNTH. REACT. INORG. MET.-ORG. CHEM., 26(1), 11-19 (1996)

NEW MEZAL COMPLEXES DERTVED FROM 1-N- (6-NI'TROBENZIlWDAZOLFi- 1-CARBONyLMETHyL)-

4- (u-NAPHTHYL)-~-THICSEMICARBAZIDE

Xu Pengfei

Department of Chemistry, Lanzhou University, Lanzhou 730000, P. R. China

xu ztluguo Lanzhou Medical Collage, Lanzhou 730000

w u sham

Cenaal Research Institute of Building and Construction of M. M. R. , Beijing 100088

AlsrRAm

ThesynthesisandcharacterizationofMn(P),Cu(II),Co(lI),Ni(I),Pb

(P ) and UOz ( VI ) complexes of the new ligand 1-N- (6-nitrobenzimidazole- 1- carbonylmethyl)-4- (a -naphthyl ) -3- tmiw&de ("MS) is reported. Infrared

spectral data show that NBNMS behaves as a tetradentate hgand involving the carbonyl

and thiocarbonyl groups in conjunction with the adjacent nitrogen a t o m ( C = N

groups). Each ligand bridges to two metal centers. This result in polymers that grow

through consecutive ligand-metal linkages for all but UOz( VI >. In contrast, NBNMS

acts as a monobasic tridentate ligand with U02( v1 ).

INTRODUCTION

since the structure of Vitamin BIZ had beem reported, many studies of imidazoles

and benzimidamles have focused on the significant biological activities1*2*5 of this

molecule. Preston' has reported that a massive reseach effort has been expended upon

the chemistry of imidazoles and benzimidazoles with particular emphasis on the

11

Copyright 0 1996 by Marcel Deker, Inc.

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12 xu, xu, AND wu

synthesis of new compounds for pharmacological screening. &thi5 reported the

synthesisof 1-N- ( 6-nitrobenzimidazole- 2-carbOnylmethyl)- 4-phenyl- 3-thiosemim-

bazide and an investigation of its biological activites. But, 1-N- (6-nitrobenzimidazoie-

1 carbonylmethy1)- 4- (a- naphy1)- 3- thiosemicarbazide and its metal complexes were

not reported. In this paper, we wish to describe the preparation and characterization of

NBNMS as well as its new complexes with six metals.

EXPERIMENTAL

All chemicals used were of analytical grade. Elemental analyses were carried out

on a 1106 Element Analysis Instrument. Infared spectra were recorded as KJ3r disks on

a Nicolet 17OSX IT-IR spectrometer. Melting points were taken on a Kofler Melting

Point Apparatus and are uncorrected. W spectra were recorded with a Shimadzu W-

240 spectrophotometer. Thermal analyses were obtained using a Dupont 1090B thermal

analytical apparatus in NZ atmosphere.

Synthesis of the Ligand

The ligand was prepared from 6-nitrobenzimidazole as shown in Scheme I .

Ethyl 6-Nitrobenzimidazole- 1-acetate ( 2 ) . A mixture of 4 . 1 g (0.025 mole) 6-

nitrobenzimidazole, 6 g anhydrous KzC03 and 2 mL polyethylene glycol 400 in 150 mL, dry ethyl acetate was refluxed and 3 mL ethyl chloroacetate was added in drops and

the mixture agitated for five hours. The inorganic solids were filtered and the

precipitate was washed with cold water three times. The organic layer was separated

and the solvent removed on a rotary evaporator. The product was used without further

recrystallization for the next reaction. Mp. 96-98%, yield 65%, 4.05 g.

6-Nitrobenzimidazole-1-acetic Acid Hydrazide(3). To a suspension of (2) (2. 49 g ,

0.01 mole) in ethanol (50 mL), 1 . 2 mL (0.02 mole) of 85% hydrazine hydrate

was added and the reaction mixture refluxed for 1.5 h. After cooling to room

temperature the resulting solid was filtered, washed thoroughly with cold water, dried

and recrystallised from ethanol. Yield, 84%, 1.97 g. Mp. 192--194.C.

IN- (6-Nitrobenzimidazole-1-carbonylmethyl >- 4- ( a-naphthyl 1- 3-thiosemicarbazide

(4) . A mixture of 2.36 g (0.01 mole) of ( 3 ) and 1.85 g (0.01 mole) of 1- -

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NEW METAL COMPLEXES 13

@b where R'=

Scheme I

naphthylisothiocyanate in 100 mL of ethanol was heated on a water bath for 2 h. The

solid obtained after subsequent concentration and cooling was filtered, dried and

recrystallised from DMSO-ethanol. Yield, 91%, 3.82 g. Mp. 158-16OC.

Synthesis of Metal Chelates

A solution of 0.210 g (0.5 m o l e ) NBNh4S in 10 mL absolute ethanol and 1. 5

mL DMSO was added with constant stirring to 0.55 m o l e of metal acetate in 5 mL of

absolute ethanol. 'The mixture was stirred at reflux temperature for three hours, the

products were collected on a filter, washed with hot water, hot ethand, and diethyl

ether, and then dried in a vacuurh desiccator over anhydrous calcium chIoride.

REsuLls AND DISCUSSION

A general equation for the formation of complexes is shown below:

NBNMS + M(OAc), * mHzO + (NBNUS-2H)M * rB,O + (m-n)H,O + 2HOAc

m = l , 2, 3 , 4 ;

M=Cu ( I ) , Co( I ) , Ni ( I ) , Mn( I ) , and Pb( I ).

n=Oor I .

2NBNMS UOz(0Ac)z 2H20 + (NBNUS-H)JJO, + 2HzO + 2HOAc

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14 xu, xu, AND wu

All the metal( II ) chelates are colored (Table 1). They are quite stable in air, and all have limited solubility in dimethylformamide (DMF) and dimethylsulphoxide

(DMSO). They are insoluble in other common organic solvents. Analytical data are

reported in Table 1.

Infrared Spectra

The positions of infrared bands of NBNMS and its complexes have been collected

in Table 2. The infrared spectrum of the free ligand showed three bands at 3260, 3177 and

3104 cm-' , assigned6 to u(N--H) of atoms N 4 , 2, and 1, respectively. The strong band

at 1703 em-' is assigned to the stretching vibration of the carbonyl group in NBNMS

and this band is absent in the spectra of the metal complexes (Table 2). The weak band

at 1000 cm-' is assigned to the U(N-N) stretching vibration associated with the carbonyl

group and thioketo group. The broad, but weak bands at 2150 - 1930 cm-' are

assigned to stretching vibrations of the N- H **. 0 group, and they may suggest the

presence of intramolecular hydrogen bonding'. No bands exist in the 3400-3500

cm-'or in the 2600-2500 cm-' regions which would be expected if OH and/or SH groups were present. This indicates the presence of NBNMS in the thione and keto form

as a solid (Scheme II ). The metal bonding sites have been determined by comparing the spectra of the

complexes and the free ligand (Table 2). The infrared spectra and elemental a n a l p

of NBNMS complexes show the ligand can behave as a bridging binegative tetradentate

ligand, coordinating through the enolic oxygen atom and the nitrogen atom of the N?H

group from one end and the thiol sulphur atom and the nitrogen atom of the N'H group

on the other with the replacement of hydrogen atoms from the enolized carbonyl and

thiocarbonyl group. Geometric factors prevent the coordination of aU the donors to a

m e metal ion, and thus a polymeric chain grows through consecutive ligand metal

linkage as shown in Scheme Ill.

This mode of complexation is supported by the following: (1) The disappearance

of the carbonyl, thiocarbonyl bands, and uJNH), u&w vibrations with the simultaneous

appearance of new bands in the 1630 - 1621 cm-' and 1595 - 1580 cm-' regions

asignable'to ucc,+& and uc,& vibrations associated with nitrogem 1 and 2. (2) The

appearance of new bands in the 1190 cm-' and 620 an-' regions assignableg to

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NEW METAL COMPLEXES 15

Mp,

( d e c C )

Table 1. Analytical and Physical Data of Compound

Yield Elemental Analyses(%) Found (Calc. )

(%) H N

Complex

Formula cnlour

NBNMS white

cdI@Ko6 -

WBNhiS)Cu HzO blue

GOHl&KoSCU

158-160

261-262

>300

>300

>300

>300

208-209

57.16 3. 72 20. 18

(57.14) (3. 81) (20.00)

47.85 2. 89 17. 16

(48.05) (3.20) (16.82)

48.32 3. 15 16.93

(48.49) (3.23) (16. 97)

48.20 3. 06 16. 47

(48.51) (3. 23) (16.98)

48.26 3. 14 16. 54

(48.89) (3.26) (17. 11)

88

90

92

88

91

37.97 2. 14 13. 13

(38.39) (2.24) (13. 44)

43.25 3. 00 14. 89

(43.32) (2. 71) (15. 16)

88

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16 XU, XU, AND WU

1

R-C- NH I I I

N-C-fW-R' s O... / 2 'H

Scheme I

I M- - t

I M-

I N

S ""'3 Scheme N

u(c-0) and ~ ( c - s ) vibrations, respectively, and (3) the observation of new bands in the

510 cm-' and 390 cm-' regions assignable'0*" to U(M-O) and u(M-N), respectively.

Also, NBNUS behaves as a mononegative tridentate ligand via NQ, the enolic

oxygen (=C-OH) with the displacement of a hydrogen atom from the latter group

and thiocarbonyl sulphur as shown in Scheme lV. This mode of chelation is found in

the complex (NBNUSH)2U02 and is supported by the foUowing: ( 1 ) the

disappearmce of bands of both the carbonyl oxygen and N'H with the simultaneous

appearance of new bands in the 1621 and 1190 cm-I regions attributable'to qcnN)and

u ( ~ - ~ ) , respectively, ( 2 ) the thiocarbonyl bands and & vibration remain and the

appearance of new bands in the region 317 cm-l due" to U(U-S) is an indication that

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NEW METAL COMPLEXES

NBNMS

17

260-320 CHZCONFUWC- 20.5(20.0)

340-550 c,a7m- ,s 41.2(41. 4)

Scheme N

HzO

cdf7m-

Table 3. TGA Data for h'BNhfS and (NBNM)Cu H@

4. O(3. 6)

28. O(28. 4)

Compound I Temperature(C1 I Leaving group I Weight h(%)'

C~H&SOZCH&ONNC

residue CuS

r 2 0 0 - 2 5 0 1 C ~ H f i 3 0 ~ - I 38.2(38. 6)

48.0C48.8)

20.0(19. 1)

40-60

200-350

400-700 ( M W ) C u * H z O

. Calculated values given in parentheses.

thiocarbonyl is taking part in complexation and (3) the appearance of new bands in the

regions 511, 390 cm-' assignable*0 to u ( ~ - ~ ) , u(~-~), respectively.

'H NMR Spectrum of the Ligand

'Ihe'H NMR spectrum of NBNMS in DhS0-b shows three broad peaks at

lo. 63, 9 .94 and 9.72 ppm that are downfield from TMS; all these disappear upon

adding DzO, indicating that these peaks can be assigned to the MI protons of groups 1 ,

2 and 4 , respectively. A smglet at 5. 25 ppm and a multiplet at 7. 3 - 8. 6 ppm are

attributed to the protons of C H z and aryl groups, respectively.

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18

No.

1

2

3

4

XU, XU, AND WU

Table 4. UV Spectra of the Ligand and Ih Complexes (cm-')

Compd. KBand B B a n d CTBand d-d Band

- NBNMS 37500 33400 -

(NBNMS)Cu.HzO 37200 32000 30300 23600 16600 12900

(NBNMS)Co.H@ 37400 32000 30000 23500 16300 13280

(NBNMS)Ni-H,O 37500 32000 30000 23000 16700 13600

? h e r d Analyses

The TGA data are listed in Table 3. The decomposition temperatures of the

complexes are higher than the ligand. This added stability may be the result of stable

five-membered rings which decrease the possibilities for low energy decomposition

pathways.

Electronic Spectra

The electronic spectra of NBNh4S and three of its complexes are listed in Table 4. They are observed in DMF and d-d bands are observed in nujol mull spectra.

'Re K and B transition bands are observed at 37500 cm-' and 33400 cm-' for

N B M . Compared to the free ligand , in the complexes, the B band is shifted to lower

wave numbers which is consistent with an increase in the degree of n- cloud

conjugation. The d-d bands'3 show frequencies a t 23000 cm-', 16000 cm-' and

13000 cm-' . A CT band exhibits its absorbance at about 30000 cm-I.

ACKNOWLEDGEMENT

This work was supported by the Gansu Province Mid-youth Science Fund. The

authors gratefully acknowledge this support.

REFERENCES

1. S. Bahadur, A. K. Gaoel and R. S. Verma, J. Indian Chem. Soc., - 53, 1163 (1976).

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NEW METAL COMPLEXES 19

2. 0. P. D. George and M. John, Japan Kokai 76, 1 4 1 , 870; Chem. Abstr. , 87, 53304e (1977).

3. Werchan Hans G. , Dittrich Guenter and Held Paul, German (East) Patent, 127, 636; Chem. Abstr., 88, 1 3 6 6 8 0 ~ (1978).

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Received: 23 August 1994 Referee I: K . Moedritzer Accepted: 12 July 1995 Referee 11: D. X. West

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