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Polymer complexes. Part XXVII. Novel mixed-valence-ligand poly(2-acryl-amido-1-phenyl-2-aminothiourea) complexes
PolymerDegradationand Stability46 (1994)31-40 © 1994Elsevier Science Limited Printed in Northern Ireland. All rights reserved 0141-3910194]$07.00
~ ~ 7, ELSEVIER
Polymer complexes. Part XXVII. Novel mixed-valence-ligand poly(2-acryl-amido-1phenyl-2-aminothiourea) complexes A. Z. El-Sonbati,* A. M. Hassanein, M. T. Mohamed* Chemistry Departments, Faculties of Science, Mansoura and Tanta Universities, Egypt
& A. B. Abd EI-Moiz* Physics Department, Faculty of Science, Assiut University, Assiut, Egypt (Received 3 March 1994; accepted 19 March 1994)
Polymer complexes of homopolymer (APATH) with Rh (III) and Ru (III) have been prepared and characterized through chemical analyses, thermal, electronic and infrared spectral studies, and magnetic and conductance measurements. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes ((1) and (2) in the paper), and in the mononuclear polymer compound (3) it acts as a neutral bidentate ligand coordinating through the thiocarbonyl sulphur and carbonyl oxygen atoms, while in the mixed ligand paramagnetic poly-chelates, which are obtained from the reaction of A P A T H with RuC13.XH20 in the presence of N-heterocyclic bases consisting of polymer complexes (7) and (9), and in mononuclear compounds (6) and (8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds (4) and (5) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. Various ligand field parameters have been calculated and discussed. The poly-chelates are of 1 : 1, 1 : 2 and 3: 2 (metal: poly-Schiff base) stoichiometry and exhibit five and six coordination. Thermogravimetric studies indicate that these polymer complexes are stable up to -200°C and undergo complete decomposition in the range 200-570°C resulting in the formation of the stable metal oxides. The toxicity of the complexes and ligand have been demonstrated.
INTRODUCTION
polymer and/or mixed-valence-ligand polymer complexes. Rhodium and Ruthenium complexes have received more attention in the last few years owing to their potential use as anticancer agents. 12 Paramagnetic complexes of R h o d i u m ( I I ) and R u t h e n i u m ( I I ) '3 and mixed valence complexes have been rare. Recently, we have reported the interaction of A P A T H with Rh (III) and R u ( I I I ) ions in the presence and absence of various N-heterocyclic bases. ~ As far as we know, this is the first attempt to prepare
Substantial work has been done by EI-Sonbati and his group 1-11 on polychelates derived from hydroxy-ketone, acryloyl chloride and various aliphatic and aromatic amines. However, no attempt seems to have been made to study the synthesis, characterization, coordination chemistry, thermal stability and biological function of some polymeric metal chelates of new homo* Present address: Sana'a University, Sana'a, PO Box 13492, Yemen. 31
32
A. Z. El-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. Abd EI-Moiz
and investigate the mixed-ligand-valence poly(2acrylamido- 1 - phenyl- 2- aminothiourea) complexes.
EXPERIMENTAL Experimental techniques previously) -1~
were
as
described
Materials Acryloyl chloride (Aldrich) was degassed, twice distilled on a vacuum line, stored over anhydrous Na2SO4 and kept below -18°C in a tightly stoppered flask. 1-Phenyl-2-aminothiourea (Merck) was used without further purification and 2,2'-azobisisobutyronitrile (AIBN) (Eastman Kodak) was purified by recrystallization from EtOH) 4 2-Acrylamido-l-phenyl-2-aminothiourea monomer (APATH) was prepared according to E1-Sonbati et aL 5-7 The infrared spectrum of the monomer shows the presence of a - N H absorption band in the 2950-3300cm -1 region and the 1HNMR spectrum of the monomer shows characteristic bands at 6 = 10.6-10-9 ppm due to NH groups.
Polymer synthesis PAPATH homopolymer was prepared by refluxing the monomer with dimethylformamide (DMF) as solvent and 0.1 w/v AIBN as initiator for 6 h. The polymer was precipitated by pouring into distilled water.
Preparation of the polymer complexes M3(APA TH)2CIs
M = Ru (III) or Rh (III) ((1) and (2)) An ethanolic solution of A P A T H was added slowly to a constantly stirred ethanolic solution of Rh(III) or Ru(III) chloride trihydrate with 0 . 1 w / v A I B N as initiator for 6 h at room temperature. The polymer complexes precipitated immediately and were refluxed for 1-5 h to complete the reaction. These were filtered,
washed several times with ethanol and ether and dried in a vacuum oven at 40°C for several days. R u ( A P A T H ) CI3 (3) Equimolar amounts of APATH and RuCI3.XH20 were dissolved in DMF with 0 - 1 w / v A I B N as initiator. The mixture was boiled under reflux for 6 h and the resulting polymer was precipitated by pouring into a large excess of distilled H20 containing dilute HC1 to remove the metal salt incorporated into the polymer complex. The polymer complex was filtered, washed with water and dried in a vacuum oven at 40°C for several days. [M(APAT)(APATH)CIJ2H20 ((4) and (5)) A hot solution of MCIa.XH20 (M = Rh (III) or Ru (III) (0.25 g, 1 mmol) in DMF (10cm 3) was added to a filtered solution of A P A T H (0.412 g, 2mmol) in DMF (25cm3). After adding 0.1 w/v AIBN the resulting solution was heated under reflux with constant stirring for 8 h. The solution was allowed to cool to room temperature. Addition of excess ammonia solution precipitated the polymer complexes, which were then centrifuged. The resulting polymer complexes were poured into a large excess of distilled H20 containing dilute HCI to remove the metal salt incorporated into them. The polymer complexes were finally filtered, washed with water, and dried in a vacuum oven at 40°C for several days. R u ( A P A T)2CI.D M F (6) A solution of RuCI3.XH20 (0.25 g, I mmol) in DMF (10 cm 3) was added to a filtered solution of A P A T H (0-206 g) in DMF (25 cm3). After adding 0.1 w / v A I B N as initiator the resulting solution was refluxed for 8 h. The solution was concentrated to about 5 cm 3 on a water bath and the resulting polymer complex was precipitated by pouring into a large excess of distilled H20 containing dilute HC1 to remove the incorporated metal salt. The polymer complex was finally filtered, washed with water and dried in a vacuum oven at 40°C for several days. [Ru(APA T)2CI(B)]H20 (B = 1120, Py or o-phen)
(7)-(9) A filtered alkaline solution (pH = 9-11) in DMF (25 cm 3) of A P A T H (2 mmol) was added to a solution of RuCI3.XH20 (0.26 g, I mmol) (50 cm 3 DMF) containing the appropriate heterocyclic base solution along with 0-1 w/v AIBN as
33
Polymer complexes--Part X X V I I initiator. T h e resulting solution was boiled u n d e r reflux for 12 h and the resulting p o l y m e r c o m p l e x was precipitated by adding the mixture to a large excess of distilled w a t e r containing a small a m o u n t of hydrochloric acid, the latter to r e m o v e any u n r e a c t e d metal salt. T h e p o l y m e r complex was filtered, w a s h e d with water, and dried in a v a c u u m oven at 40°C for several days. Measurements
Microanalysis of all the samples was carried out at Cairo University Analytical Centre, the metal contents of the p o l y m e r complexes being calculated by a standard technique (see Table 1). H1.15 1 H N M R spectra were o b t a i n e d with a Jeol F X 90 F o u r i e r transform s p e c t r o m e t e r with D M S O - d 6 as solvent and T M S as the internal standard. I R spectra were r e c o r d e d on a P e r k i n - E l m e r 1340 s p e c t r o p h o t o m e t e r , and U V visible spectra were m e a s u r e d (nujol mull) on a Pye U n i c a m 8800 s p e c t r o p h o t o m e t e r . Magnetic
m e a s u r e m e n t s were carried out at r o o m temperature using G o u y ' s m e t h o d , employing Hg[Co(SCN)4] for calibration purposes, and were corrected for diamagnetism by using Pascal's constant. E P R m e a s u r e m e n t s of p o w d e r samples were r e c o r d e d at r o o m t e m p e r a t u r e (Tanta University, Egypt) using X - b a n d m i c r o w a v e frequency, as the first derivative, on a J E O L J E S F E 2 X G s p e c t r o m e t e r using 100 K H z magnetic field modulation, with diphenyl picryl hydrazyl ( D P P H ) as reference material. Thermogravimetric analysis (TG) and differential thermal analysis ( D T A ) were perf o r m e d on a Mettler T A 2 instrument using Micro-PT-Cups. D T A peak areas were used to calculate enthalpies. The A H value was estimated via the relationship, A H = A Ka m 1, where A is the area, Ka is the calibration constant of the apparatus and m is the sample weight. The instrument was calibrated with standards in the conventional way, and the precision expected is
Table 1. Elemental analysis and magnetic data of the polymer complexes*
No species~
(1) Rh3(APATH)2CI8d (2) Ru3(APATH)2C18" (3) Ru(APATH)C13 (4) [Rh (APAT) (APATH)C12]2H20 (5) [Ru(APAT)(APATH)CI2]2H20 (6) Ru(APAT)2CI.DMF (7) [Ru(APAT)2(HzO)Py]XC1 (8) Ru(APAT)2CI(H~O)2 (9) [Ru(APAT)CI2(o-phen.)]H20
Found (calc.) %
/,-eft'
C
H
N
S
C1b
Metal
(BM)
23.9 (23.9) 24.0 (24.1) 29-0 (28.9) 38.6 (38.6) 38.8 (38.8) 45-7 (45.7) 46-6 (46.6) 41.2 (41.2) 45.9 (46.0)
2.0 (2.1) 2.0 (2-0) 2.4 (2.3) 3.1 (3.0) 3.1 (3.0) 4-0 (3.9) 3.6 (3.6) 3-4 (3.3) 3.0 (2.9)
5.6 (5.7) 5.6 (5.5) 6.8 (6.7) 9.0 (8-8) 9.1 (9.0) 9.3 (9-1) 10-9 (11.1) 9.6 (9.4) 9.7 (9.5)
6.4 (6.6) 6.4 (6.5) 7.7 (7.8) 10.4 (10.2) 10.4 (10.2) 10.6 (10.4) 10.0 (9-8) 11.0 (10.8) 5-6 (5.4)
28.3 (28.5) 28.4 (28.5) 25.8 (25-7) 11.5 (11.3) 11.5 (11-3) 5.9 (6.1) 5.5 (5.3) 6.1 (6.0) 12.4 (12-2)
30.7 (30.9) 30-3 (30.5) 24.4 (24.3) 16.6 (16-4) 16-3 (16-11 16-7 (16.3~ 15.7 (15.4) 17.4 (17.2) 17.6 (17-2)
1.52 1.64 1-35" dia/ dial 1.67 2.08 1.81 1.71
* Microanalytical data as well as sulphur, metal and chloride estimations are in good agreement with the stoichiometry of the proposed complexes. a Insoluble in water and common organic solvents but slightly soluble in coordinating solvents such as DMSO and DMF, except compounds (1) and (2), coloured, non-hygroscopic, air-stable at room temperature for long periods. These do not possess sharp melting points. The molar conductances of these polymeric complexes in DMF are in the range 13-21 fU 1cm2 tool 1, indicating the non-electrolytic nature of the complexes. b Estimated gravimetrically. " Per metal ion and measured at room temperature and uncorrected for diamagnetism. Magnetic moments of ruthenium polymer complexes lie in the range 1.6-2.1 BM corresponding to one unpaired electron. a The insolubility in water and common organic solvents and lack of sharp melting points support the trimeric nature of these complexes. e Lower than the value expected for the one unpaired electron. I dia. = diamagnetic.
A. Z. EI-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. A b d El-Moiz
34
around 5%. The area under a peak was traced on high quality tracing paper, cut out and weighed. The experimental conditions for the DTA runs were as follows: heating rate, 2°C/min; purge gas, dry nitrogen (100ml/min); sample weight, c. 10 mg. In the evaluation of antifungal activity, the ligand and metal complexes were incorporated in Czapeck's medium against Aspergillus nigor. Dimethylsulphoxide (DMSO) was used as a solvent for preparing different concentrations in the range 10-500 ppm of the chelating agent and metal complexes. The growth inhibition percentage was calculated on the basis of the average diameter of the fungal colony. Percentage inhibition = (C - T) x 100/C where C is the diameter of the fungus colony in the control plates after 8 days, T is the diameter of the fungus colony in treated plates after 8 days.
RESULTS AND DISCUSSION Characterization of the homopolymer N-Acryloyl-l-phenyl-2-aminothiourea (APATH) was prepared by the amidation reaction of acryloyl chloride with 1-phenyl-2-aminothiourea in presence of pyridine and hydroquinone under reflux in benzene. 1-6 The monomer APATH was characterized as in the experimental section. The monomer was then polymerized by radical polymerization initiated by 2,2-azoisobutyronitrile (AIBN). The homopolymer has been characterized by various techniques. 1-" Both IR and tH NMR spectroscopy were used to characterize the PAPATH homopolymer. The
IR spectrum of the new ligand (see Table 2) exhibits absorptions due to NH, CO, CS and the phenyl ring. T h e 1 H NMR spectrum of APATH homopolymer showed the expected peaks 6 (DMSO-d6) 10-6-10-9 (2H, 2NH), 2-89 (2H, CH2) and 9.08-7.64ppm (5H, C 6 H 5 ) protons, which are downfield from TMS. The first signal disappeared on adding D20, while the other signals were still observed. The NMR spectrum of APATH monomer showed the expected peaks and pattern of the vinylic group (CH2~---CH), i.e. 6 (DMSO-d6) 6.36 (dd, J = 17, 11 Hz) for the vinyl CH proton and 6 5.21 ppm (AM part of AMX system dd, J = 17, 1 Hz, and dd, J= 11, 1 Hz) for the vinyl CH2 protons, respectively. These peaks disappeared on polymerization while a triplet at 61-98 ( t , J = 7 H z ) and a doublet at 61.86ppm (d, J = 7Hz) appeared. This indicates that the polymerization of APATH monomer occurs on the vinyl group. It is worth noting that the rest of the proton spectrum of the monomer and polymer remain almost without change. The 13CNMR spectra of homopolymer and compound (3) have also been recorded. A considerable shift (Table 3) in the positions of carbons attached to the different participating groups clearly indicates the bonding of thione sulphur and carbonyl to the Ru atom. On the basis of the above spectral studies, octahedral geometry has been suggested for the Ru(APATH)CI3 type complex.
Characterization of the polymer complexes The stoichiometries of the complexes have been deduced from their elemental analysis results.
Table 2. Infrared band assignments (cm-~)for homopolymerand its polymer complexes* Species
C--S
C-~-O
PAPATH (1) (2) (3) (4) (5) (6) (7) a (8)" (9)
1240, 765 1220, 750 1225,755 1215, 745 1230,740 1225,735 1230, 750 1225,755 1215,750 1220,740
1660 1605 1605 1600 1595 1590 -----
C~N ----1620 1630 1590 1610 1615 1630
C--O
C--N
M--S
M--C1
----1190 1180 1215 1125 1240 1245
1520 1530 1525 1540 1510 1515 1535 1540 1545 1540
-345 340 350 355 352 360 365 362 352
-350 355 365 345 350 340 -335 345
* F o r t h e structures, see T a b l e 1. " T h e 7r-HOH m o d e of c o o r d i n a t e d w a t e r is f o u n d in the r e g i o n 7 8 0 - 8 1 0 cm-~.
35
Polymer complexes--Part XXVII Table 3. ~sC NMR spectral data (fi, ppm) of homopolymer and compound (3) PAPATH (3)
1
2
3
4
5
6
7
8
9
10
147.81 145.80
123.09 122.20
119.98 119-87
135.49 134.56
146.39 146.08
148.48 147.07
177-09 170-71
172.82 183.87
32-1 33.4
16.22 18.21
These indicate that the Ru(III) and Rh (III) complexes fall into two distinct categories. The first is trinuclear while the second is a mononuclear polymer complex. The deprotonation is confirmed by the effervescence resulting from the formation of HC1 gas during complex formation, and has been assessed quantitatively by both pH measurement and a spot-test technique, as well as detection of a characteristic odour.S-1 l The infrared spectra of all the polymer complexes showed a number of differences from the spectrum of the homopolymer (see Table 2), principally in regions associated with the NH group, C = S , C = O groups and ring vibrations. The spectra of the polymer complexes in nujol or KBr pellets were compared with the spectrum of homopolymer in the solid state. The infrared spectrum of homopolymer showed four bands with N - - H stretching region. The presence of four bands in this region instead of the usual two implies the existence of various types of N - - H bands, which could result from intermolecular or intramolecular donor-acceptor interactions among the various coordination sites present in the homopolymer. These bands occur in the same region in the spectra of the polymer complexes, showing that the amine (NH) groups are not participating in coordination in compounds (1)-(9).
The strong band at 1660cm i is assigned to (CO). Homopolymer has a C~--~-S(thione) group with an adjacent proton, and this group is likely to undergo enolization. However, the absence of v ( S - - H ) (2570cm -1) indicates that the homopolymer exists predominantly in the thione form in the solid state. The presence of a strong band (v (C~-~-S)(1240 cm-t)) also supports this assumption. The bands 1450 (--N--C~--~-S), 1070 (NCN), 765 (NCO) and 700cm ~ (C---O out of plane bend) 1~ are also present. A strong band is observed at 1520 cm 1, which seems to arise from C - - N vibration of the thiocarbamides. On complexation of (1)-(3), the last two bands are shifted to a lower wave number showing that the thione sulphur and the carbonyl oxygen are coordinated to the metal ion. Thus homopolymer
acts as a bidentate neutral ligand coordinating via the CS and CO in both the thione and ketone groups forming a 6-membered ring. On examination of IR spectra of homopolymer and compounds (1)-(3), it is observed that there is no great change in N - - H stretching and bending vibrations, but there is a considerable decrease in the intensity and frequencies of C~---S (10-30 cm 1) and C - - O (50-75 cm 1) stretching bands. This indicates that coordinations are through thiocarbonyl sulphur and carbonyl oxygen in compounds (1)-(3). Furthermore, a slight increase in the C - - N stretching frequencies on coordination also supports these complexes. The Rh (III) and Ru (III) polymeric complexes show (Rh--C1) and (Ru--C1) frequencies that seem too low for terminal Rh--Cl and Ru--C1 bands and correspond to bridging chlorine (245-205 cm ~) groups. However, bands in the region 350-365cm-I may be attributed to terminal Rh--Cl and Ru--Cl groups, corresponding to which there are no ligand bands. Analytical data (Table 1) suggest the formulae Rh3(APAT)2CI~ and Ru3(APAT)2Cls. The /.~-eff value of polymeric compounds (1) and (2) assumes a trimeric structure. The paramagnetism of the compounds (1) and (2) indicates the presence of Rh (II) and Ru (II) in the polymeric compounds. ~6 PAPATH, being a good reducing agent, brings about the reduction of Rh (III) to Rh (II) or Ru (III) to Ru (II). From elemental analysis, magnetic susceptibility and IR spectra, a trimeric structure is tentatively proposed. In this structure, two six-coordinated Rh (III) or Ru (III)ions occupy the extreme positions while a four-coordinated Rh(II) or R u ( I I ) i o n occupies the middle position. The three metal ions are connected by dichloro-bridges. The four chlorine atoms surrounding the Rh(II) and Rh(III) or Ru(II) and Ru(III) are probably responsible for the lower magnetic moments shown by the polymeric complexes (1) and (2). In contrast, A P A T H reacts in the enol form by displacement of the (3200cm ~) N H - - group hydrogen atom adjacent to the C - - O group, to form a C - - O single bond. This phenomenon was
36
A. Z. EI-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. Abd El-Moiz
observed for compounds (4)-(9) where the ligand is a bidentate monobasic SO donor. The IR band of the amide group (C---O) disappears from the spectra of the complexes (4)-(9) and a new band characteristic of (NCO-) appears as a distinct pair in the 1180-1245 cm -1 range (C--O) (enolic) mode in the complexes indicating the destruction of the carbonyl group due to enolization through the imidol oxygen. A strong band at 1615cm -~ is assigned to the v ( C = N ) . Coordination of the C~--~-S of the homopolymer moiety is indicated by a negative shift of 20-30cm -~, observed in the v(C~----S) mode of all the polymeric complexes compared with its position at 765cm-1 in the homopolymer.1~ Also, in compounds (7) and (9) a new band appears in the region 1615-1620 cm -1, attributable to coordinated pyridine.8 Thus, the nitrogen of the pyridine is coordinated to metal ions. In the spectrum of compound (6), the band associated with the carbonyl absorption v (C--O), which is at 1675 cm -1 in the spectrum of DMF, is shifted to lower frequency by 15 cm -1, indicating the coordination of DMF to the central ion. 16 Finally, the ligand may be a bidentate monobasic/neutral ligand, coordinating through the enolic, carbonyl oxygen atom, and thione sulphur atom. This behaviour is found in compounds (4) and (5). Steric factors prevent the coordination of all the donors to a single metal ion. This mode of complexation is confirmed by the following evidence: the appearance of new bands due to v ( C = N ) and v (C----O) 3'4 with respect to the other bands due to v (C---O) and v (C~--~S). The non-ligand bands appearing in the 490-330 and 370-320cm -~ regions may tentatively be assigned to v(M---O) and v (M--S) vibrations, respectively.~7
Magnetochemical and spectroscopic studies Magnetic susceptibility measurements at room temperature show that the magnetic moments of polymer complexes mostly lie in the range 1.52-2.08BM (Table 1), corresponding to one unpaired electron. The (4) and (5) polymer complexes were found to be diamagnetic. The insights into the structure and geometries of the polymeric metal complexes were further supported by electronic spectral data (Table 4). Bands I, II and III around 38460, 34482 and
32 786 cm -1 of PAPATH in DMF are assigned to the intraligand tr-tr* transitions mainly located on the N--C~--~--Sand the n-~r transition. Weak band III was shifted towards the higher energy region in the spectra of polymeric complexes (1) and (2). This band may be assigned to an n-zr transition and the shift may be due to coordination. The band observed at 24390cm -1 in the spectrum of compound (1) may be due to the 1mlg----)lT2g transition of Rh (111).TM The rhodium polymeric compound (3) shows only intraligand transitions. All other expected transitions 19were probably masked by intraligand bands. The electronic spectra of the Ru (III) polymer complexes show 15 625-15 267 (2T2g--->4Tlg), 18 867-17 857 (2T2g--*4T2g) and 23 80920 833 cm -~ (2T2g--,2Tlg) transitionsY 9 In the spectra of Ru (III) polymer complexes, some of these transitions could not be observed, probably because of masking by a strong charge-transfer (CT) and/or intraligand (IL) transition. A band or shoulder around 34 48232 786cm-~ is assigned to the intraligand transition. Another band at 30769cm -~ in the spectrum of [Ru(APAT)ECIPy]H20 may be assigned to M--~L or L---~M charge-transfer transitions. The electronic spectrum of [Rh(APAT)(APATH)C12]2H20 polymer complex and the ligand field parameters are given in Table 4. The values are comparable with those observed for other complexes of this metal ion with the same donor ligands. 15 The /3 value (40%) of the free ion suggests considerable orbital overlap with strong covalency bonding. E1-Sonbati et al. ~5 have demonstrated that a decrease in the values of/3 is associated with a reduction in the positive charge of the cation and a tendency towards reduction to the next lower oxidation state. The value of the room temperature magnetic moment of Ru3(APATH)2CI8 (1.64 BM) is lower than the predicted value (2.10 BM). The lowering of the /z-eft value may arise due to the presence of lower symmetry ligand fields, metal-metal interactions or extensive electron delocalization.2° Ruthenium (III) polymeric complex (Ru(APATH)CI3), is insoluble in almost all the common organic solvents and has /z-eft= 1.35 BM, which is considerably lower than the value expected for one unpaired electron. This
37
Polymer complexes--Part X X V I I
Table 4. Electronic spectral bands, assignments, ligand field parameters and proposed geometries for the polymer complexes (1)-(9)* Species
Band position A,.ax (cm ')
PAPATH ~
38 460 34 482 32 786 24 390 13 648 17 598 22 700 17 500 20 000 25 600 17 800 20 200 24 800 38 022 32 258 37 735 32 467 21 739 18 867 33 112 30 769 23 809 33 898 18 181 34 482 20 833
(1) (2) (3) (4)b (5) (6)
(7) (8) (9)"
Assignment 7r~ re* ~ ~ re* n --* Jr IAIg--+ IT2g 2 T 2 --* 4T2 2T2g----~ g 2A2gg , 2Tlg 2T2g--->2A2g, 2Tig
Geometry
Octahedral Octahedral Octahedral
CT or IL IA,. ~ 2T,. ,Alg-+ iTlg
Distorted octahedral
Alg-+ T2g IL IL or CT IL 2T2g-----~2AEg, 2Tlg 2T2g~ 4T2g
Distorted octahedral
IL CT 2T2g--+ 2A2g, 2Tlg IL 2T2g--->4T2g IL 2T2g--+ 2Tlg
Distorted octahedral
Distorted octahedral
Distorted octahedral Distorted octahedral
* For the structures, see Table 1. o Homopolymer and spectrum taken in DMF solvent. h Dq = 2125 cm-% B = 293 cm -t,/3 = 0.40, v2/v, = 1-12. ' o-Phenanthroline is known to behave as a n-bonding ligand and forms strong metal-ligand covalent bonds. might be either due to high values of s p i n - o r b i t coupling constants in the heavier transition elements which often lead to very low magnetic moments, or due to m e t a l - m e t a l interaction. T h e electronic spectrum of the p o l y m e r complex displays three bands: 1 7 0 0 0 c m ' (2T2g-->2Azg, 2T~g) (lowest spin allowed d - d transition) and 20 000-25 600 cm-1) (charge transfer or intraligand). '5 Since the h o m o p o l y m e r is bidentate in this p o l y m e r complex, coordination through C~--~S and C - - O , a chlorine-bridged structure, is c o m m e n s u r a t e .
Table 5. g-Values
of some of the Ru(lll) complexes
Species
(6) (7) (9)
polymer
EPR spectra g~
gy
g:
g"
2.72 2-31 2-22
2.23 2.14 2.22
1.78 2-00 1.94
2.28 2-15 2.13
"g = (1/3g~ + 1/3g~ + 1/3g~)m.
Electron paramagnetic resonance T o interpret the E P R data, we have used the m e t h o d described by Bleanery, O ' B r i e n and EI-Sonbati, which has b e e n successfully applied to m a n y complexes. 9a~-23 Thus the E P R study of c o m p o u n d s (6) and (7) indicates the rhombic distortion for these p o l y m e r complexes, and axial s y m m e t r y for c o m p o u n d (9) (Table 5). O n the basis of analytical, conductivity, magnetic, spectroscopic and E P R data, a distorted octahedral g e o m e t r y is assigned to R u (III) and R h (III) p o l y m e r complexes, assuming that the h o m o p o l y m e r is bidentate and coordinated through the carbonyl oxygen and sulphur of the thioamide group.
Thermal methods o f analysis Thermogravimetry T h e synthesis of thermally stable polychelates is n o w a promising area in the chemistry of heat resistant polymers. Some of the polymers
38
A. Z. El-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. Abd El-Moiz
containing metal ions linked by chelate rings derived from organic groups show exceptional thermal stability. Aromatic backbone units are much more stable than aliphatic ones and they have significantly higher melting temperatures. Thermogravimetric curves for PAPATH homopolymer and polymer complexes of APATH with RhCI3.XH20 and RuCI3.XH20 are shown in Fig. 1, and for the mixed ligand with RuC13.XHaO in Fig. 2. The polymer complexes are more stable than PAPATH homopolymer. This is similar to the results obtained by E1-Sonbati L2,7 and his school 24,25 with polymer complexes of 5-vinylsalicylidene-2-aminophenol, 5-vinylsalicylideneaniline and acrylonitrile with some transition metal salts. The stabilities of the polymer complexes of APATH increase in the order 9> 1 >8>7>2>3>4>5>6>homopolymer (see footnote of Table 1). The greater stabilities of the polymer complexes compared with homopolymer may be due to the formation of six-membered ring structures in the homopolymer complexes and the cross-linking indicated by the insolubility in common organic solvents. Thermogravimetric curves of compounds (1)-(9) (Figs 1 and 2) show three main decomposition steps characterizing the thermal behaviour of these compounds. Resolution can be improved by lower heating rates. Only slight differences could be observed in characteristic temperatures corresponding to the second and
"-¢x
a0
100 ~
80
60
~ \ ~ " ~ ....
o +
~
4o
..........
"7
'x \ " ' .
~__
z 9
---
20
0
I 100
I 200
I 300
Temperature
I 400
I 500
°C
Fig. 2. Thermogravimetric curves for PAPATH homopolymer and mixed ligand complexes, APATH-Py, APATH-ophen or APATH-DMF with RuC13.XH20: (+) PAPATH homopolymer; (7) [Ru(APAT)CI:(o-phen.)]H20; (8) [Ru(APAT)(H20)(Py)]CI.H20; (9) Ru(APAT)2C1.DMF.
third steps, which can be accounted for by the formation of a common decomposition product at the end of the first step. Quantitative examination of the TG curves confirmed the removal of a halogen and the heterocyclic base or DMF in the second step for all compounds. The first is probably due to the loss of water molecules in the coordinated structure. The TG studies showed that all the compounds decomposed at c. 135-340°C, losing the greater part of the ligand atoms. The straight chain in the homopolymer and polymer complexes gave higher values of weight loss during the first decomposition step. The weight of the final residues, which can be considered as metal oxides, are in good agreement with those calculated from the metal content. Determination o f activation energies
it
_'-,~" %%
it
. . . . .
2
......... 3
40 z
%.~,,/'-, ~?"~'~ " - -
4
.......
0
~ "~-~ " . . . . . . . N~',. "...~,~,~ .
5
20 -
o
._
I
I
I
I
I
100
200
300
400
500
Temperature
°C
Fig. 1. Thermogravimetric curves for PAPATH homopolymer and polymer complexes of APATH with RhC13.XH20 and RuCI3.XH20: (1) [Ru(APAT)2C1.H20]H20; (2) [Ru(APAT)(APATH)CI2]2H20; (3) [Ru(APAT)(APATH)C1212H20; (4) Ru(APATH)Cla; (5) Rua(APATH)2CI8; (6) Rh3(APATH)2CIs.
The activation energies of the thermal degradation of PAPATH homopolymer, polymer complexes and mixed ligand polymer complexes of APATH with RhCla.XHzO and RuCI3.XH20 were determined from the temperature dependence of the rate of chain rupture. The rate constant of the thermal degradation was plotted according to the Arrhenius relationship. Table 6 shows the activation energies of PAPATH homopolymer and of the polymer complexes. It is clear that the activation energy of the homopolymer is smaller than those for the polymer complexes. Therefore PAPATH should undergo decomposition more readily than the
Polymer complexes--Part XXVI1 Table 6. Activation energies for the thermal degradation of PAPATH homopolymer, polymer complexes of APATH with RuCI3.XH20 and RuCi3.XI-120, and mixed ligand APATHY (Y = Py, o-phen, or DMF) with RuCI3.XH20
Species"
Ea
(KJ mol- ~) PAPATHb (1) (2) (3) (4) (5)
10•2 19.4 20.2 26.9 50•0 50.4
(6)
75.0
(7) (8) (9)
63.0 71.0 60.0
a See footnote to Table 1. h Homopolymer.
polymer complexes and the mixed ligand polymer complexes. The D T A curves start with a narrow endotherm, immediately followed by an exotherm. Comparing the initial decomposition temperature of step two for the polymer complexes with one another, it is evident that the anion has a considerable influence. The halogen complexes are most stable. The reduced stability of complexes with polyatomic anions could be a consequence of stronger M - - S bonds with concomitant strengthening of the thioamide C - - N bonds (compare also the M - - S frequencies m " shift " -N--C~--S--> -~ "~- M • Table 2). The electronic would weaken the adjacent bonds. Finally, there are several ways in which solvated molecules can be incorporated into the crystal, e.g. linked via hydrogen bonds to counter anions, incorporated as lattice solvate or coordinated to the central metal atom. The first type was found in the crystal structure of the halogen complexes; the last is present in [Ru(APAT)2(H20)Py]C1H20. Dehydration of the [Ru(APAT)(H20)Py]CIH20 polymer complex occurs between 55 and 85°C in a single endothermic step ( A H = 54 KJ mol --~ per H20 released). The exothermic step with a peak at 145°C is interpreted as reorganization (partial substitution of the water molecules by chlorine ions) of the amorphous system into a crystalline phase.
39
The decrease in Tma x o n going from the chloro to the other complexes can be explained by the smaller ionic radius (and hence a higher electrostatic field) for the C1 anion, leading to stronger H O H . . . X bonds in the former compounds. The expected endothermic behaviour for these processes of dehydration was observed in the DSC curves in the same temperature range. The dehydration energy calculated for these effects varied between 42.0 and 30.0KJmo1-1. The anhydrous compounds were stable up to 230°C. This temperature is similar to that of the decomposition of the free ligand, suggesting that the decomposition of the anhydrous complexes begins with the pyrolysis of the ligand. Weight loss continued without interruption up to approximately 500°C, at which temperature the weight of the residue was in accordance with that calculated for the metal oxides, this being confirmed by IR spectroscopy.
P h y s i o l o g i c a l activity
The homopolymer ( P A P A T H ) and its metal chelates were screened (in the range 10500 ppm) in vitro for their fungistatic activities by adopting the agar plate technique with
Aspergillus niger• From the data, it has been observed that the ligand shows 8.6 and 74.6% inhibition at 10 and 500 ppm concentration levels, respectively, whereas the metal complexes at the same concentrations show 8.5-18-1 and 71.2-100% inhibition. This reveals that the complex formation markedly enhances the activity. The C--S, C - - O or C - - N groups in the ligand are free, and show higher toxicity as they can easily combine with the fungal cells to check growth. On the other hand, in metal complexes, they are not free to inhibit fungal growth, as they are involved in bond formation with the metal ions. Hence the toxicity of the complexes decreases. The free ligand is highly soluble in the medium and may be easily absorbed by the fungal hypose, but the complexes show less solubility and hence a difference in toxicity.
CONCLUSIONS From the analysis of the experimental results it is clear that the behaviour of the homopolymer in
40
A. Z. El-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. A b d El-Moiz
all these p o l y m e r complexes is to act as a reducing agent toward r h o d i u m and r u t h e n i u m . As far as the structure of the synthesized p o l y m e r complexes is concerned, their insolubility in practically all the c o m m o n organic solvents prevents crystallization, and therefore also precludes the possibility of clearcut structural evidence. H y p o t h e s e s can, however, be put forward, starting f r o m the following evidence: (1) T h e insolubility suggests a polymeric or oligomeric structure. (2) T h e h o m o p o l y m e r acts in different ways according to the neutral or anionic state, i.e. as m o n o b a s i c bidentate. (3) T h e metal presents different coordination n u m b e r s in the same molecule. (4) In the spectra of the p o l y m e r and mixed ligand p o l y m e r complexes, there seems to be extensive mixing b e t w e e n the bands of the h o m o p o l y m e r and those of the bases, hence the characteristic N-heterocyclic frequencies did not occur at standard positions. In the v ( O - - H ) water region, the spectra of (7) and (8) show strong, sharp bands b e t w e e n 3440 and 3 2 5 0 c m -1, which can be attributed to the presence of c o o r d i n a t e d water. 4-7 In the spectra of (4), (5) and (9), there is a strong and broad absorption (c. 3500-3100 cm-1), which indicates that lattice water is present. 1-3 T h e s p e c t r u m of (7) exhibits, in addition to the bands of c o o r d i n a t e d water, a broad c o n t i n u o u s absorption at 3550-3100cm-1; this is apparently due to the presence of both c o o r d i n a t e d and crystal water in this c o m p o u n d . A c c o r d i n g to the electronic spectra and magnetic data, there is a c o n t i n u o u s transition b e t w e e n distorted octahedral and octahedral stereochemistry of the p o l y m e r complexes studied. ~r-electron acceptor mixed ligand (Py, o-phen.) stabilizes the polarizable ligand (Itelectron d o n o r ligand, e.g. halide ion) and prefers the octahedral structure, while the less polarizable ligand (o'-bonding ligand, e.g. H 2 0 ) leads to irregular d e f o r m e d coordination, suggesting that the b o n d i n g effect of the ligand in the axial position c a n n o t be ignored.
Cl
cl
o/l\c,/ Cl
Cl
Structure 1 REFERENCES
1. EI-Sonbati, A. Z., Transition Met. Chem., 16 (1991) 45. 2. EI-Sonbati, A. Z., Transition Met. Chem., 17 (1992) 19. 3. EI-Sonbati, A. Z., Synth. React. Inorg. Met. Org. Chem., 21 (1991) 203. 4. EI-Sonbati, A. Z., Synth. React. lnorg. Met. Org. Chem., 21 (1991) 977. 5. EI-Sonbati, A. Z. & Diab, M. A., Polym. Deg. Stab., 22 (1988) 295. 6. EI-Sonbati, A. Z., E1-Dissouky, A. & Diab, M. A., Acta Polymerica, 40 (1989) 112. 7. EI-Sonbati, A. Z. & Diab, M. A., Acta Polymerica, 39 (1988) 11. 8. E1-Sonbati, A. Z. & Hefni, M. A., Polym. Deg. Stab., 43 (1993) 33. 9. EI-Sonbati, A. Z., E1-Bindary, A. A., Diab, M. A. & Mazrouh, S. A., Monatschefte f~r Chemie, 124 (1993) 793. 10. EI-Sonbati, A. Z., EI-Bindary, A. A., Diab, M. A., EI-EIa, M. A. & Mazrouh, S. A., Polym. Paper, 35 (1993) 647. 11. E1-Sonbati, A. Z., E1-Bindary, A. A., Diab, M. A., E1-EIa, M. A. & Mazrouh, S. A., Polym. Deg. Stab., 42 (1993) 1. 12. Cleare, M. J., Coord. Chem. Rev., 12 (1974) 349. 13. van Gall, H. L. M. & Verlaak, J. M. J., Inorg. Chem. Acta., 23 (1977) 43. 14. Grant, D. M. & Grassie, N., Polym. Sci., 42 (1960) 587. 15. EI-Sonbati, A. Z., Hassanein, A. M. & Abd EI-Moiz, A. B., Synth. React. Inorg. Met. Org. Chem. (in press). 16. Haszeldine, R. N., J. Chem. Soc. (1954) 4145. 17. Billing, E., Shupack, S. I., Waters, J. H., Williams, R. & Gray, H. B., J. Am. Chem. Soc., 86 (1964) 926. 18. Ball Hausen, C. J., Introduction to Ligand Field Theory, McGraw Hill, New York, 1962, p. 276. 19. Sengupta, S. K., Sahni, S. K. & Kapoor, R. N., Polyhedron, 2 (1983) 317. 20. Livingston, S. E., Mayfield, J. H. & Moors, D. S., Aust. J. Chem., 28 (1975) 2531. 21. El.-Sonbati, A. Z., Hefni, M. A. & Abd EI-Moiz, A. B., Synth. React. Inorg. Met. Org. Chem. (in press). 22. Hudson, A. & Kenedy, M. J., J. Chem. Soc., A (1969) 1116. 23. Sakai, S., Yanase, Y., Hagiwara, N., Takeshita, T., Naganuma, H. & Onkuba, K., J. Phys. Chem., 86 (1982) 1038. 24. Diab, M. A., EI-Sonbati, A, Z., Hilali, A. S., Killa, H. M. & Ghoniem, M. M., Polym. Deg. Stab., 29 (1990) 165. 25. Diab, M. A., EI-Sonbati, A. Z., EI-Sanabari, A. A. & Taha, F. I., Polym. Deg. Stab., 24 (1989) 51.
~ ~ 7, ELSEVIER
Polymer complexes. Part XXVII. Novel mixed-valence-ligand poly(2-acryl-amido-1phenyl-2-aminothiourea) complexes A. Z. El-Sonbati,* A. M. Hassanein, M. T. Mohamed* Chemistry Departments, Faculties of Science, Mansoura and Tanta Universities, Egypt
& A. B. Abd EI-Moiz* Physics Department, Faculty of Science, Assiut University, Assiut, Egypt (Received 3 March 1994; accepted 19 March 1994)
Polymer complexes of homopolymer (APATH) with Rh (III) and Ru (III) have been prepared and characterized through chemical analyses, thermal, electronic and infrared spectral studies, and magnetic and conductance measurements. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes ((1) and (2) in the paper), and in the mononuclear polymer compound (3) it acts as a neutral bidentate ligand coordinating through the thiocarbonyl sulphur and carbonyl oxygen atoms, while in the mixed ligand paramagnetic poly-chelates, which are obtained from the reaction of A P A T H with RuC13.XH20 in the presence of N-heterocyclic bases consisting of polymer complexes (7) and (9), and in mononuclear compounds (6) and (8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds (4) and (5) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. Various ligand field parameters have been calculated and discussed. The poly-chelates are of 1 : 1, 1 : 2 and 3: 2 (metal: poly-Schiff base) stoichiometry and exhibit five and six coordination. Thermogravimetric studies indicate that these polymer complexes are stable up to -200°C and undergo complete decomposition in the range 200-570°C resulting in the formation of the stable metal oxides. The toxicity of the complexes and ligand have been demonstrated.
INTRODUCTION
polymer and/or mixed-valence-ligand polymer complexes. Rhodium and Ruthenium complexes have received more attention in the last few years owing to their potential use as anticancer agents. 12 Paramagnetic complexes of R h o d i u m ( I I ) and R u t h e n i u m ( I I ) '3 and mixed valence complexes have been rare. Recently, we have reported the interaction of A P A T H with Rh (III) and R u ( I I I ) ions in the presence and absence of various N-heterocyclic bases. ~ As far as we know, this is the first attempt to prepare
Substantial work has been done by EI-Sonbati and his group 1-11 on polychelates derived from hydroxy-ketone, acryloyl chloride and various aliphatic and aromatic amines. However, no attempt seems to have been made to study the synthesis, characterization, coordination chemistry, thermal stability and biological function of some polymeric metal chelates of new homo* Present address: Sana'a University, Sana'a, PO Box 13492, Yemen. 31
32
A. Z. El-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. Abd EI-Moiz
and investigate the mixed-ligand-valence poly(2acrylamido- 1 - phenyl- 2- aminothiourea) complexes.
EXPERIMENTAL Experimental techniques previously) -1~
were
as
described
Materials Acryloyl chloride (Aldrich) was degassed, twice distilled on a vacuum line, stored over anhydrous Na2SO4 and kept below -18°C in a tightly stoppered flask. 1-Phenyl-2-aminothiourea (Merck) was used without further purification and 2,2'-azobisisobutyronitrile (AIBN) (Eastman Kodak) was purified by recrystallization from EtOH) 4 2-Acrylamido-l-phenyl-2-aminothiourea monomer (APATH) was prepared according to E1-Sonbati et aL 5-7 The infrared spectrum of the monomer shows the presence of a - N H absorption band in the 2950-3300cm -1 region and the 1HNMR spectrum of the monomer shows characteristic bands at 6 = 10.6-10-9 ppm due to NH groups.
Polymer synthesis PAPATH homopolymer was prepared by refluxing the monomer with dimethylformamide (DMF) as solvent and 0.1 w/v AIBN as initiator for 6 h. The polymer was precipitated by pouring into distilled water.
Preparation of the polymer complexes M3(APA TH)2CIs
M = Ru (III) or Rh (III) ((1) and (2)) An ethanolic solution of A P A T H was added slowly to a constantly stirred ethanolic solution of Rh(III) or Ru(III) chloride trihydrate with 0 . 1 w / v A I B N as initiator for 6 h at room temperature. The polymer complexes precipitated immediately and were refluxed for 1-5 h to complete the reaction. These were filtered,
washed several times with ethanol and ether and dried in a vacuum oven at 40°C for several days. R u ( A P A T H ) CI3 (3) Equimolar amounts of APATH and RuCI3.XH20 were dissolved in DMF with 0 - 1 w / v A I B N as initiator. The mixture was boiled under reflux for 6 h and the resulting polymer was precipitated by pouring into a large excess of distilled H20 containing dilute HC1 to remove the metal salt incorporated into the polymer complex. The polymer complex was filtered, washed with water and dried in a vacuum oven at 40°C for several days. [M(APAT)(APATH)CIJ2H20 ((4) and (5)) A hot solution of MCIa.XH20 (M = Rh (III) or Ru (III) (0.25 g, 1 mmol) in DMF (10cm 3) was added to a filtered solution of A P A T H (0.412 g, 2mmol) in DMF (25cm3). After adding 0.1 w/v AIBN the resulting solution was heated under reflux with constant stirring for 8 h. The solution was allowed to cool to room temperature. Addition of excess ammonia solution precipitated the polymer complexes, which were then centrifuged. The resulting polymer complexes were poured into a large excess of distilled H20 containing dilute HCI to remove the metal salt incorporated into them. The polymer complexes were finally filtered, washed with water, and dried in a vacuum oven at 40°C for several days. R u ( A P A T)2CI.D M F (6) A solution of RuCI3.XH20 (0.25 g, I mmol) in DMF (10 cm 3) was added to a filtered solution of A P A T H (0-206 g) in DMF (25 cm3). After adding 0.1 w / v A I B N as initiator the resulting solution was refluxed for 8 h. The solution was concentrated to about 5 cm 3 on a water bath and the resulting polymer complex was precipitated by pouring into a large excess of distilled H20 containing dilute HC1 to remove the incorporated metal salt. The polymer complex was finally filtered, washed with water and dried in a vacuum oven at 40°C for several days. [Ru(APA T)2CI(B)]H20 (B = 1120, Py or o-phen)
(7)-(9) A filtered alkaline solution (pH = 9-11) in DMF (25 cm 3) of A P A T H (2 mmol) was added to a solution of RuCI3.XH20 (0.26 g, I mmol) (50 cm 3 DMF) containing the appropriate heterocyclic base solution along with 0-1 w/v AIBN as
33
Polymer complexes--Part X X V I I initiator. T h e resulting solution was boiled u n d e r reflux for 12 h and the resulting p o l y m e r c o m p l e x was precipitated by adding the mixture to a large excess of distilled w a t e r containing a small a m o u n t of hydrochloric acid, the latter to r e m o v e any u n r e a c t e d metal salt. T h e p o l y m e r complex was filtered, w a s h e d with water, and dried in a v a c u u m oven at 40°C for several days. Measurements
Microanalysis of all the samples was carried out at Cairo University Analytical Centre, the metal contents of the p o l y m e r complexes being calculated by a standard technique (see Table 1). H1.15 1 H N M R spectra were o b t a i n e d with a Jeol F X 90 F o u r i e r transform s p e c t r o m e t e r with D M S O - d 6 as solvent and T M S as the internal standard. I R spectra were r e c o r d e d on a P e r k i n - E l m e r 1340 s p e c t r o p h o t o m e t e r , and U V visible spectra were m e a s u r e d (nujol mull) on a Pye U n i c a m 8800 s p e c t r o p h o t o m e t e r . Magnetic
m e a s u r e m e n t s were carried out at r o o m temperature using G o u y ' s m e t h o d , employing Hg[Co(SCN)4] for calibration purposes, and were corrected for diamagnetism by using Pascal's constant. E P R m e a s u r e m e n t s of p o w d e r samples were r e c o r d e d at r o o m t e m p e r a t u r e (Tanta University, Egypt) using X - b a n d m i c r o w a v e frequency, as the first derivative, on a J E O L J E S F E 2 X G s p e c t r o m e t e r using 100 K H z magnetic field modulation, with diphenyl picryl hydrazyl ( D P P H ) as reference material. Thermogravimetric analysis (TG) and differential thermal analysis ( D T A ) were perf o r m e d on a Mettler T A 2 instrument using Micro-PT-Cups. D T A peak areas were used to calculate enthalpies. The A H value was estimated via the relationship, A H = A Ka m 1, where A is the area, Ka is the calibration constant of the apparatus and m is the sample weight. The instrument was calibrated with standards in the conventional way, and the precision expected is
Table 1. Elemental analysis and magnetic data of the polymer complexes*
No species~
(1) Rh3(APATH)2CI8d (2) Ru3(APATH)2C18" (3) Ru(APATH)C13 (4) [Rh (APAT) (APATH)C12]2H20 (5) [Ru(APAT)(APATH)CI2]2H20 (6) Ru(APAT)2CI.DMF (7) [Ru(APAT)2(HzO)Py]XC1 (8) Ru(APAT)2CI(H~O)2 (9) [Ru(APAT)CI2(o-phen.)]H20
Found (calc.) %
/,-eft'
C
H
N
S
C1b
Metal
(BM)
23.9 (23.9) 24.0 (24.1) 29-0 (28.9) 38.6 (38.6) 38.8 (38.8) 45-7 (45.7) 46-6 (46.6) 41.2 (41.2) 45.9 (46.0)
2.0 (2.1) 2.0 (2-0) 2.4 (2.3) 3.1 (3.0) 3.1 (3.0) 4-0 (3.9) 3.6 (3.6) 3-4 (3.3) 3.0 (2.9)
5.6 (5.7) 5.6 (5.5) 6.8 (6.7) 9.0 (8-8) 9.1 (9.0) 9.3 (9-1) 10-9 (11.1) 9.6 (9.4) 9.7 (9.5)
6.4 (6.6) 6.4 (6.5) 7.7 (7.8) 10.4 (10.2) 10.4 (10.2) 10.6 (10.4) 10.0 (9-8) 11.0 (10.8) 5-6 (5.4)
28.3 (28.5) 28.4 (28.5) 25.8 (25-7) 11.5 (11.3) 11.5 (11-3) 5.9 (6.1) 5.5 (5.3) 6.1 (6.0) 12.4 (12-2)
30.7 (30.9) 30-3 (30.5) 24.4 (24.3) 16.6 (16-4) 16-3 (16-11 16-7 (16.3~ 15.7 (15.4) 17.4 (17.2) 17.6 (17-2)
1.52 1.64 1-35" dia/ dial 1.67 2.08 1.81 1.71
* Microanalytical data as well as sulphur, metal and chloride estimations are in good agreement with the stoichiometry of the proposed complexes. a Insoluble in water and common organic solvents but slightly soluble in coordinating solvents such as DMSO and DMF, except compounds (1) and (2), coloured, non-hygroscopic, air-stable at room temperature for long periods. These do not possess sharp melting points. The molar conductances of these polymeric complexes in DMF are in the range 13-21 fU 1cm2 tool 1, indicating the non-electrolytic nature of the complexes. b Estimated gravimetrically. " Per metal ion and measured at room temperature and uncorrected for diamagnetism. Magnetic moments of ruthenium polymer complexes lie in the range 1.6-2.1 BM corresponding to one unpaired electron. a The insolubility in water and common organic solvents and lack of sharp melting points support the trimeric nature of these complexes. e Lower than the value expected for the one unpaired electron. I dia. = diamagnetic.
A. Z. EI-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. A b d El-Moiz
34
around 5%. The area under a peak was traced on high quality tracing paper, cut out and weighed. The experimental conditions for the DTA runs were as follows: heating rate, 2°C/min; purge gas, dry nitrogen (100ml/min); sample weight, c. 10 mg. In the evaluation of antifungal activity, the ligand and metal complexes were incorporated in Czapeck's medium against Aspergillus nigor. Dimethylsulphoxide (DMSO) was used as a solvent for preparing different concentrations in the range 10-500 ppm of the chelating agent and metal complexes. The growth inhibition percentage was calculated on the basis of the average diameter of the fungal colony. Percentage inhibition = (C - T) x 100/C where C is the diameter of the fungus colony in the control plates after 8 days, T is the diameter of the fungus colony in treated plates after 8 days.
RESULTS AND DISCUSSION Characterization of the homopolymer N-Acryloyl-l-phenyl-2-aminothiourea (APATH) was prepared by the amidation reaction of acryloyl chloride with 1-phenyl-2-aminothiourea in presence of pyridine and hydroquinone under reflux in benzene. 1-6 The monomer APATH was characterized as in the experimental section. The monomer was then polymerized by radical polymerization initiated by 2,2-azoisobutyronitrile (AIBN). The homopolymer has been characterized by various techniques. 1-" Both IR and tH NMR spectroscopy were used to characterize the PAPATH homopolymer. The
IR spectrum of the new ligand (see Table 2) exhibits absorptions due to NH, CO, CS and the phenyl ring. T h e 1 H NMR spectrum of APATH homopolymer showed the expected peaks 6 (DMSO-d6) 10-6-10-9 (2H, 2NH), 2-89 (2H, CH2) and 9.08-7.64ppm (5H, C 6 H 5 ) protons, which are downfield from TMS. The first signal disappeared on adding D20, while the other signals were still observed. The NMR spectrum of APATH monomer showed the expected peaks and pattern of the vinylic group (CH2~---CH), i.e. 6 (DMSO-d6) 6.36 (dd, J = 17, 11 Hz) for the vinyl CH proton and 6 5.21 ppm (AM part of AMX system dd, J = 17, 1 Hz, and dd, J= 11, 1 Hz) for the vinyl CH2 protons, respectively. These peaks disappeared on polymerization while a triplet at 61-98 ( t , J = 7 H z ) and a doublet at 61.86ppm (d, J = 7Hz) appeared. This indicates that the polymerization of APATH monomer occurs on the vinyl group. It is worth noting that the rest of the proton spectrum of the monomer and polymer remain almost without change. The 13CNMR spectra of homopolymer and compound (3) have also been recorded. A considerable shift (Table 3) in the positions of carbons attached to the different participating groups clearly indicates the bonding of thione sulphur and carbonyl to the Ru atom. On the basis of the above spectral studies, octahedral geometry has been suggested for the Ru(APATH)CI3 type complex.
Characterization of the polymer complexes The stoichiometries of the complexes have been deduced from their elemental analysis results.
Table 2. Infrared band assignments (cm-~)for homopolymerand its polymer complexes* Species
C--S
C-~-O
PAPATH (1) (2) (3) (4) (5) (6) (7) a (8)" (9)
1240, 765 1220, 750 1225,755 1215, 745 1230,740 1225,735 1230, 750 1225,755 1215,750 1220,740
1660 1605 1605 1600 1595 1590 -----
C~N ----1620 1630 1590 1610 1615 1630
C--O
C--N
M--S
M--C1
----1190 1180 1215 1125 1240 1245
1520 1530 1525 1540 1510 1515 1535 1540 1545 1540
-345 340 350 355 352 360 365 362 352
-350 355 365 345 350 340 -335 345
* F o r t h e structures, see T a b l e 1. " T h e 7r-HOH m o d e of c o o r d i n a t e d w a t e r is f o u n d in the r e g i o n 7 8 0 - 8 1 0 cm-~.
35
Polymer complexes--Part XXVII Table 3. ~sC NMR spectral data (fi, ppm) of homopolymer and compound (3) PAPATH (3)
1
2
3
4
5
6
7
8
9
10
147.81 145.80
123.09 122.20
119.98 119-87
135.49 134.56
146.39 146.08
148.48 147.07
177-09 170-71
172.82 183.87
32-1 33.4
16.22 18.21
These indicate that the Ru(III) and Rh (III) complexes fall into two distinct categories. The first is trinuclear while the second is a mononuclear polymer complex. The deprotonation is confirmed by the effervescence resulting from the formation of HC1 gas during complex formation, and has been assessed quantitatively by both pH measurement and a spot-test technique, as well as detection of a characteristic odour.S-1 l The infrared spectra of all the polymer complexes showed a number of differences from the spectrum of the homopolymer (see Table 2), principally in regions associated with the NH group, C = S , C = O groups and ring vibrations. The spectra of the polymer complexes in nujol or KBr pellets were compared with the spectrum of homopolymer in the solid state. The infrared spectrum of homopolymer showed four bands with N - - H stretching region. The presence of four bands in this region instead of the usual two implies the existence of various types of N - - H bands, which could result from intermolecular or intramolecular donor-acceptor interactions among the various coordination sites present in the homopolymer. These bands occur in the same region in the spectra of the polymer complexes, showing that the amine (NH) groups are not participating in coordination in compounds (1)-(9).
The strong band at 1660cm i is assigned to (CO). Homopolymer has a C~--~-S(thione) group with an adjacent proton, and this group is likely to undergo enolization. However, the absence of v ( S - - H ) (2570cm -1) indicates that the homopolymer exists predominantly in the thione form in the solid state. The presence of a strong band (v (C~-~-S)(1240 cm-t)) also supports this assumption. The bands 1450 (--N--C~--~-S), 1070 (NCN), 765 (NCO) and 700cm ~ (C---O out of plane bend) 1~ are also present. A strong band is observed at 1520 cm 1, which seems to arise from C - - N vibration of the thiocarbamides. On complexation of (1)-(3), the last two bands are shifted to a lower wave number showing that the thione sulphur and the carbonyl oxygen are coordinated to the metal ion. Thus homopolymer
acts as a bidentate neutral ligand coordinating via the CS and CO in both the thione and ketone groups forming a 6-membered ring. On examination of IR spectra of homopolymer and compounds (1)-(3), it is observed that there is no great change in N - - H stretching and bending vibrations, but there is a considerable decrease in the intensity and frequencies of C~---S (10-30 cm 1) and C - - O (50-75 cm 1) stretching bands. This indicates that coordinations are through thiocarbonyl sulphur and carbonyl oxygen in compounds (1)-(3). Furthermore, a slight increase in the C - - N stretching frequencies on coordination also supports these complexes. The Rh (III) and Ru (III) polymeric complexes show (Rh--C1) and (Ru--C1) frequencies that seem too low for terminal Rh--Cl and Ru--C1 bands and correspond to bridging chlorine (245-205 cm ~) groups. However, bands in the region 350-365cm-I may be attributed to terminal Rh--Cl and Ru--Cl groups, corresponding to which there are no ligand bands. Analytical data (Table 1) suggest the formulae Rh3(APAT)2CI~ and Ru3(APAT)2Cls. The /.~-eff value of polymeric compounds (1) and (2) assumes a trimeric structure. The paramagnetism of the compounds (1) and (2) indicates the presence of Rh (II) and Ru (II) in the polymeric compounds. ~6 PAPATH, being a good reducing agent, brings about the reduction of Rh (III) to Rh (II) or Ru (III) to Ru (II). From elemental analysis, magnetic susceptibility and IR spectra, a trimeric structure is tentatively proposed. In this structure, two six-coordinated Rh (III) or Ru (III)ions occupy the extreme positions while a four-coordinated Rh(II) or R u ( I I ) i o n occupies the middle position. The three metal ions are connected by dichloro-bridges. The four chlorine atoms surrounding the Rh(II) and Rh(III) or Ru(II) and Ru(III) are probably responsible for the lower magnetic moments shown by the polymeric complexes (1) and (2). In contrast, A P A T H reacts in the enol form by displacement of the (3200cm ~) N H - - group hydrogen atom adjacent to the C - - O group, to form a C - - O single bond. This phenomenon was
36
A. Z. EI-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. Abd El-Moiz
observed for compounds (4)-(9) where the ligand is a bidentate monobasic SO donor. The IR band of the amide group (C---O) disappears from the spectra of the complexes (4)-(9) and a new band characteristic of (NCO-) appears as a distinct pair in the 1180-1245 cm -1 range (C--O) (enolic) mode in the complexes indicating the destruction of the carbonyl group due to enolization through the imidol oxygen. A strong band at 1615cm -~ is assigned to the v ( C = N ) . Coordination of the C~--~-S of the homopolymer moiety is indicated by a negative shift of 20-30cm -~, observed in the v(C~----S) mode of all the polymeric complexes compared with its position at 765cm-1 in the homopolymer.1~ Also, in compounds (7) and (9) a new band appears in the region 1615-1620 cm -1, attributable to coordinated pyridine.8 Thus, the nitrogen of the pyridine is coordinated to metal ions. In the spectrum of compound (6), the band associated with the carbonyl absorption v (C--O), which is at 1675 cm -1 in the spectrum of DMF, is shifted to lower frequency by 15 cm -1, indicating the coordination of DMF to the central ion. 16 Finally, the ligand may be a bidentate monobasic/neutral ligand, coordinating through the enolic, carbonyl oxygen atom, and thione sulphur atom. This behaviour is found in compounds (4) and (5). Steric factors prevent the coordination of all the donors to a single metal ion. This mode of complexation is confirmed by the following evidence: the appearance of new bands due to v ( C = N ) and v (C----O) 3'4 with respect to the other bands due to v (C---O) and v (C~--~S). The non-ligand bands appearing in the 490-330 and 370-320cm -~ regions may tentatively be assigned to v(M---O) and v (M--S) vibrations, respectively.~7
Magnetochemical and spectroscopic studies Magnetic susceptibility measurements at room temperature show that the magnetic moments of polymer complexes mostly lie in the range 1.52-2.08BM (Table 1), corresponding to one unpaired electron. The (4) and (5) polymer complexes were found to be diamagnetic. The insights into the structure and geometries of the polymeric metal complexes were further supported by electronic spectral data (Table 4). Bands I, II and III around 38460, 34482 and
32 786 cm -1 of PAPATH in DMF are assigned to the intraligand tr-tr* transitions mainly located on the N--C~--~--Sand the n-~r transition. Weak band III was shifted towards the higher energy region in the spectra of polymeric complexes (1) and (2). This band may be assigned to an n-zr transition and the shift may be due to coordination. The band observed at 24390cm -1 in the spectrum of compound (1) may be due to the 1mlg----)lT2g transition of Rh (111).TM The rhodium polymeric compound (3) shows only intraligand transitions. All other expected transitions 19were probably masked by intraligand bands. The electronic spectra of the Ru (III) polymer complexes show 15 625-15 267 (2T2g--->4Tlg), 18 867-17 857 (2T2g--*4T2g) and 23 80920 833 cm -~ (2T2g--,2Tlg) transitionsY 9 In the spectra of Ru (III) polymer complexes, some of these transitions could not be observed, probably because of masking by a strong charge-transfer (CT) and/or intraligand (IL) transition. A band or shoulder around 34 48232 786cm-~ is assigned to the intraligand transition. Another band at 30769cm -~ in the spectrum of [Ru(APAT)ECIPy]H20 may be assigned to M--~L or L---~M charge-transfer transitions. The electronic spectrum of [Rh(APAT)(APATH)C12]2H20 polymer complex and the ligand field parameters are given in Table 4. The values are comparable with those observed for other complexes of this metal ion with the same donor ligands. 15 The /3 value (40%) of the free ion suggests considerable orbital overlap with strong covalency bonding. E1-Sonbati et al. ~5 have demonstrated that a decrease in the values of/3 is associated with a reduction in the positive charge of the cation and a tendency towards reduction to the next lower oxidation state. The value of the room temperature magnetic moment of Ru3(APATH)2CI8 (1.64 BM) is lower than the predicted value (2.10 BM). The lowering of the /z-eft value may arise due to the presence of lower symmetry ligand fields, metal-metal interactions or extensive electron delocalization.2° Ruthenium (III) polymeric complex (Ru(APATH)CI3), is insoluble in almost all the common organic solvents and has /z-eft= 1.35 BM, which is considerably lower than the value expected for one unpaired electron. This
37
Polymer complexes--Part X X V I I
Table 4. Electronic spectral bands, assignments, ligand field parameters and proposed geometries for the polymer complexes (1)-(9)* Species
Band position A,.ax (cm ')
PAPATH ~
38 460 34 482 32 786 24 390 13 648 17 598 22 700 17 500 20 000 25 600 17 800 20 200 24 800 38 022 32 258 37 735 32 467 21 739 18 867 33 112 30 769 23 809 33 898 18 181 34 482 20 833
(1) (2) (3) (4)b (5) (6)
(7) (8) (9)"
Assignment 7r~ re* ~ ~ re* n --* Jr IAIg--+ IT2g 2 T 2 --* 4T2 2T2g----~ g 2A2gg , 2Tlg 2T2g--->2A2g, 2Tig
Geometry
Octahedral Octahedral Octahedral
CT or IL IA,. ~ 2T,. ,Alg-+ iTlg
Distorted octahedral
Alg-+ T2g IL IL or CT IL 2T2g-----~2AEg, 2Tlg 2T2g~ 4T2g
Distorted octahedral
IL CT 2T2g--+ 2A2g, 2Tlg IL 2T2g--->4T2g IL 2T2g--+ 2Tlg
Distorted octahedral
Distorted octahedral
Distorted octahedral Distorted octahedral
* For the structures, see Table 1. o Homopolymer and spectrum taken in DMF solvent. h Dq = 2125 cm-% B = 293 cm -t,/3 = 0.40, v2/v, = 1-12. ' o-Phenanthroline is known to behave as a n-bonding ligand and forms strong metal-ligand covalent bonds. might be either due to high values of s p i n - o r b i t coupling constants in the heavier transition elements which often lead to very low magnetic moments, or due to m e t a l - m e t a l interaction. T h e electronic spectrum of the p o l y m e r complex displays three bands: 1 7 0 0 0 c m ' (2T2g-->2Azg, 2T~g) (lowest spin allowed d - d transition) and 20 000-25 600 cm-1) (charge transfer or intraligand). '5 Since the h o m o p o l y m e r is bidentate in this p o l y m e r complex, coordination through C~--~S and C - - O , a chlorine-bridged structure, is c o m m e n s u r a t e .
Table 5. g-Values
of some of the Ru(lll) complexes
Species
(6) (7) (9)
polymer
EPR spectra g~
gy
g:
g"
2.72 2-31 2-22
2.23 2.14 2.22
1.78 2-00 1.94
2.28 2-15 2.13
"g = (1/3g~ + 1/3g~ + 1/3g~)m.
Electron paramagnetic resonance T o interpret the E P R data, we have used the m e t h o d described by Bleanery, O ' B r i e n and EI-Sonbati, which has b e e n successfully applied to m a n y complexes. 9a~-23 Thus the E P R study of c o m p o u n d s (6) and (7) indicates the rhombic distortion for these p o l y m e r complexes, and axial s y m m e t r y for c o m p o u n d (9) (Table 5). O n the basis of analytical, conductivity, magnetic, spectroscopic and E P R data, a distorted octahedral g e o m e t r y is assigned to R u (III) and R h (III) p o l y m e r complexes, assuming that the h o m o p o l y m e r is bidentate and coordinated through the carbonyl oxygen and sulphur of the thioamide group.
Thermal methods o f analysis Thermogravimetry T h e synthesis of thermally stable polychelates is n o w a promising area in the chemistry of heat resistant polymers. Some of the polymers
38
A. Z. El-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. Abd El-Moiz
containing metal ions linked by chelate rings derived from organic groups show exceptional thermal stability. Aromatic backbone units are much more stable than aliphatic ones and they have significantly higher melting temperatures. Thermogravimetric curves for PAPATH homopolymer and polymer complexes of APATH with RhCI3.XH20 and RuCI3.XH20 are shown in Fig. 1, and for the mixed ligand with RuC13.XHaO in Fig. 2. The polymer complexes are more stable than PAPATH homopolymer. This is similar to the results obtained by E1-Sonbati L2,7 and his school 24,25 with polymer complexes of 5-vinylsalicylidene-2-aminophenol, 5-vinylsalicylideneaniline and acrylonitrile with some transition metal salts. The stabilities of the polymer complexes of APATH increase in the order 9> 1 >8>7>2>3>4>5>6>homopolymer (see footnote of Table 1). The greater stabilities of the polymer complexes compared with homopolymer may be due to the formation of six-membered ring structures in the homopolymer complexes and the cross-linking indicated by the insolubility in common organic solvents. Thermogravimetric curves of compounds (1)-(9) (Figs 1 and 2) show three main decomposition steps characterizing the thermal behaviour of these compounds. Resolution can be improved by lower heating rates. Only slight differences could be observed in characteristic temperatures corresponding to the second and
"-¢x
a0
100 ~
80
60
~ \ ~ " ~ ....
o +
~
4o
..........
"7
'x \ " ' .
~__
z 9
---
20
0
I 100
I 200
I 300
Temperature
I 400
I 500
°C
Fig. 2. Thermogravimetric curves for PAPATH homopolymer and mixed ligand complexes, APATH-Py, APATH-ophen or APATH-DMF with RuC13.XH20: (+) PAPATH homopolymer; (7) [Ru(APAT)CI:(o-phen.)]H20; (8) [Ru(APAT)(H20)(Py)]CI.H20; (9) Ru(APAT)2C1.DMF.
third steps, which can be accounted for by the formation of a common decomposition product at the end of the first step. Quantitative examination of the TG curves confirmed the removal of a halogen and the heterocyclic base or DMF in the second step for all compounds. The first is probably due to the loss of water molecules in the coordinated structure. The TG studies showed that all the compounds decomposed at c. 135-340°C, losing the greater part of the ligand atoms. The straight chain in the homopolymer and polymer complexes gave higher values of weight loss during the first decomposition step. The weight of the final residues, which can be considered as metal oxides, are in good agreement with those calculated from the metal content. Determination o f activation energies
it
_'-,~" %%
it
. . . . .
2
......... 3
40 z
%.~,,/'-, ~?"~'~ " - -
4
.......
0
~ "~-~ " . . . . . . . N~',. "...~,~,~ .
5
20 -
o
._
I
I
I
I
I
100
200
300
400
500
Temperature
°C
Fig. 1. Thermogravimetric curves for PAPATH homopolymer and polymer complexes of APATH with RhC13.XH20 and RuCI3.XH20: (1) [Ru(APAT)2C1.H20]H20; (2) [Ru(APAT)(APATH)CI2]2H20; (3) [Ru(APAT)(APATH)C1212H20; (4) Ru(APATH)Cla; (5) Rua(APATH)2CI8; (6) Rh3(APATH)2CIs.
The activation energies of the thermal degradation of PAPATH homopolymer, polymer complexes and mixed ligand polymer complexes of APATH with RhCla.XHzO and RuCI3.XH20 were determined from the temperature dependence of the rate of chain rupture. The rate constant of the thermal degradation was plotted according to the Arrhenius relationship. Table 6 shows the activation energies of PAPATH homopolymer and of the polymer complexes. It is clear that the activation energy of the homopolymer is smaller than those for the polymer complexes. Therefore PAPATH should undergo decomposition more readily than the
Polymer complexes--Part XXVI1 Table 6. Activation energies for the thermal degradation of PAPATH homopolymer, polymer complexes of APATH with RuCI3.XH20 and RuCi3.XI-120, and mixed ligand APATHY (Y = Py, o-phen, or DMF) with RuCI3.XH20
Species"
Ea
(KJ mol- ~) PAPATHb (1) (2) (3) (4) (5)
10•2 19.4 20.2 26.9 50•0 50.4
(6)
75.0
(7) (8) (9)
63.0 71.0 60.0
a See footnote to Table 1. h Homopolymer.
polymer complexes and the mixed ligand polymer complexes. The D T A curves start with a narrow endotherm, immediately followed by an exotherm. Comparing the initial decomposition temperature of step two for the polymer complexes with one another, it is evident that the anion has a considerable influence. The halogen complexes are most stable. The reduced stability of complexes with polyatomic anions could be a consequence of stronger M - - S bonds with concomitant strengthening of the thioamide C - - N bonds (compare also the M - - S frequencies m " shift " -N--C~--S--> -~ "~- M • Table 2). The electronic would weaken the adjacent bonds. Finally, there are several ways in which solvated molecules can be incorporated into the crystal, e.g. linked via hydrogen bonds to counter anions, incorporated as lattice solvate or coordinated to the central metal atom. The first type was found in the crystal structure of the halogen complexes; the last is present in [Ru(APAT)2(H20)Py]C1H20. Dehydration of the [Ru(APAT)(H20)Py]CIH20 polymer complex occurs between 55 and 85°C in a single endothermic step ( A H = 54 KJ mol --~ per H20 released). The exothermic step with a peak at 145°C is interpreted as reorganization (partial substitution of the water molecules by chlorine ions) of the amorphous system into a crystalline phase.
39
The decrease in Tma x o n going from the chloro to the other complexes can be explained by the smaller ionic radius (and hence a higher electrostatic field) for the C1 anion, leading to stronger H O H . . . X bonds in the former compounds. The expected endothermic behaviour for these processes of dehydration was observed in the DSC curves in the same temperature range. The dehydration energy calculated for these effects varied between 42.0 and 30.0KJmo1-1. The anhydrous compounds were stable up to 230°C. This temperature is similar to that of the decomposition of the free ligand, suggesting that the decomposition of the anhydrous complexes begins with the pyrolysis of the ligand. Weight loss continued without interruption up to approximately 500°C, at which temperature the weight of the residue was in accordance with that calculated for the metal oxides, this being confirmed by IR spectroscopy.
P h y s i o l o g i c a l activity
The homopolymer ( P A P A T H ) and its metal chelates were screened (in the range 10500 ppm) in vitro for their fungistatic activities by adopting the agar plate technique with
Aspergillus niger• From the data, it has been observed that the ligand shows 8.6 and 74.6% inhibition at 10 and 500 ppm concentration levels, respectively, whereas the metal complexes at the same concentrations show 8.5-18-1 and 71.2-100% inhibition. This reveals that the complex formation markedly enhances the activity. The C--S, C - - O or C - - N groups in the ligand are free, and show higher toxicity as they can easily combine with the fungal cells to check growth. On the other hand, in metal complexes, they are not free to inhibit fungal growth, as they are involved in bond formation with the metal ions. Hence the toxicity of the complexes decreases. The free ligand is highly soluble in the medium and may be easily absorbed by the fungal hypose, but the complexes show less solubility and hence a difference in toxicity.
CONCLUSIONS From the analysis of the experimental results it is clear that the behaviour of the homopolymer in
40
A. Z. El-Sonbati, A. M. Hassanein, M. T. Mohamed, A. B. A b d El-Moiz
all these p o l y m e r complexes is to act as a reducing agent toward r h o d i u m and r u t h e n i u m . As far as the structure of the synthesized p o l y m e r complexes is concerned, their insolubility in practically all the c o m m o n organic solvents prevents crystallization, and therefore also precludes the possibility of clearcut structural evidence. H y p o t h e s e s can, however, be put forward, starting f r o m the following evidence: (1) T h e insolubility suggests a polymeric or oligomeric structure. (2) T h e h o m o p o l y m e r acts in different ways according to the neutral or anionic state, i.e. as m o n o b a s i c bidentate. (3) T h e metal presents different coordination n u m b e r s in the same molecule. (4) In the spectra of the p o l y m e r and mixed ligand p o l y m e r complexes, there seems to be extensive mixing b e t w e e n the bands of the h o m o p o l y m e r and those of the bases, hence the characteristic N-heterocyclic frequencies did not occur at standard positions. In the v ( O - - H ) water region, the spectra of (7) and (8) show strong, sharp bands b e t w e e n 3440 and 3 2 5 0 c m -1, which can be attributed to the presence of c o o r d i n a t e d water. 4-7 In the spectra of (4), (5) and (9), there is a strong and broad absorption (c. 3500-3100 cm-1), which indicates that lattice water is present. 1-3 T h e s p e c t r u m of (7) exhibits, in addition to the bands of c o o r d i n a t e d water, a broad c o n t i n u o u s absorption at 3550-3100cm-1; this is apparently due to the presence of both c o o r d i n a t e d and crystal water in this c o m p o u n d . A c c o r d i n g to the electronic spectra and magnetic data, there is a c o n t i n u o u s transition b e t w e e n distorted octahedral and octahedral stereochemistry of the p o l y m e r complexes studied. ~r-electron acceptor mixed ligand (Py, o-phen.) stabilizes the polarizable ligand (Itelectron d o n o r ligand, e.g. halide ion) and prefers the octahedral structure, while the less polarizable ligand (o'-bonding ligand, e.g. H 2 0 ) leads to irregular d e f o r m e d coordination, suggesting that the b o n d i n g effect of the ligand in the axial position c a n n o t be ignored.
Cl
cl
o/l\c,/ Cl
Cl
Structure 1 REFERENCES
1. EI-Sonbati, A. Z., Transition Met. Chem., 16 (1991) 45. 2. EI-Sonbati, A. Z., Transition Met. Chem., 17 (1992) 19. 3. EI-Sonbati, A. Z., Synth. React. Inorg. Met. Org. Chem., 21 (1991) 203. 4. EI-Sonbati, A. Z., Synth. React. lnorg. Met. Org. Chem., 21 (1991) 977. 5. EI-Sonbati, A. Z. & Diab, M. A., Polym. Deg. Stab., 22 (1988) 295. 6. EI-Sonbati, A. Z., E1-Dissouky, A. & Diab, M. A., Acta Polymerica, 40 (1989) 112. 7. EI-Sonbati, A. Z. & Diab, M. A., Acta Polymerica, 39 (1988) 11. 8. E1-Sonbati, A. Z. & Hefni, M. A., Polym. Deg. Stab., 43 (1993) 33. 9. EI-Sonbati, A. Z., E1-Bindary, A. A., Diab, M. A. & Mazrouh, S. A., Monatschefte f~r Chemie, 124 (1993) 793. 10. EI-Sonbati, A. Z., EI-Bindary, A. A., Diab, M. A., EI-EIa, M. A. & Mazrouh, S. A., Polym. Paper, 35 (1993) 647. 11. E1-Sonbati, A. Z., E1-Bindary, A. A., Diab, M. A., E1-EIa, M. A. & Mazrouh, S. A., Polym. Deg. Stab., 42 (1993) 1. 12. Cleare, M. J., Coord. Chem. Rev., 12 (1974) 349. 13. van Gall, H. L. M. & Verlaak, J. M. J., Inorg. Chem. Acta., 23 (1977) 43. 14. Grant, D. M. & Grassie, N., Polym. Sci., 42 (1960) 587. 15. EI-Sonbati, A. Z., Hassanein, A. M. & Abd EI-Moiz, A. B., Synth. React. Inorg. Met. Org. Chem. (in press). 16. Haszeldine, R. N., J. Chem. Soc. (1954) 4145. 17. Billing, E., Shupack, S. I., Waters, J. H., Williams, R. & Gray, H. B., J. Am. Chem. Soc., 86 (1964) 926. 18. Ball Hausen, C. J., Introduction to Ligand Field Theory, McGraw Hill, New York, 1962, p. 276. 19. Sengupta, S. K., Sahni, S. K. & Kapoor, R. N., Polyhedron, 2 (1983) 317. 20. Livingston, S. E., Mayfield, J. H. & Moors, D. S., Aust. J. Chem., 28 (1975) 2531. 21. El.-Sonbati, A. Z., Hefni, M. A. & Abd EI-Moiz, A. B., Synth. React. Inorg. Met. Org. Chem. (in press). 22. Hudson, A. & Kenedy, M. J., J. Chem. Soc., A (1969) 1116. 23. Sakai, S., Yanase, Y., Hagiwara, N., Takeshita, T., Naganuma, H. & Onkuba, K., J. Phys. Chem., 86 (1982) 1038. 24. Diab, M. A., EI-Sonbati, A, Z., Hilali, A. S., Killa, H. M. & Ghoniem, M. M., Polym. Deg. Stab., 29 (1990) 165. 25. Diab, M. A., EI-Sonbati, A. Z., EI-Sanabari, A. A. & Taha, F. I., Polym. Deg. Stab., 24 (1989) 51.