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Synthesis and characterization of some transition metals polymer complexes
Accepted Manuscript Synthesis and characterization of some transition metals polymer complexes Mamdouh S. Masoud, Azza E.H. Abdou, Wael M. Ahmed PII: DOI: Reference:
S0022-2860(15)00325-7 http://dx.doi.org/10.1016/j.molstruc.2015.04.007 MOLSTR 21461
To appear in:
Journal of Molecular Structure
Received Date: Revised Date: Accepted Date:
25 December 2014 4 April 2015 6 April 2015
Please cite this article as: M.S. Masoud, A.E.H. Abdou, W.M. Ahmed, Synthesis and characterization of some transition metals polymer complexes, Journal of Molecular Structure (2015), doi: http://dx.doi.org/10.1016/ j.molstruc.2015.04.007
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Synthesis and characterization of some transition metals polymer complexes Mamdouh S. Masouda, Azza E. H. Abdoua*& Wael M. Ahmeda a) Faculty of Science, Chemistry departement, Alexandria university
Abstract
Co2+, Ni2+, Cu2+, Cr3+, Mn2+and Fe3+complexes of Polyacrylamide are prepared and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggests octahedral geometry for all complexes. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ∆S# values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing 6(C2H5N) and 6(CO), the metal complexes are ended with metal as a final product. Viscosity and Shale instability using liner swell meter were carried out. Comparisons of the experimental and theoretical IR spectra were also carried out besides some other theoretical calculations. Keywords: Polyacrylamide, thermal analyses, spectra, elemental analyses, metal polymer complexes.
Introduction Study of the polymer-metal complexes has received increased interest in various branches of chemistry, chemical technology and biology and the subject has been reviewed periodically [1-4]. The chelating polymers find applications in collecting transition metal ions as well as alkali and alkaline earth metal ion separation [5] preconcentration and recovery of trace metal ions [6], catalysis [7,8] , organic synthesis[9,10], nuclear chemistry [11], water and waste water-treatment [12,13], pollution control [14], industrial processes[15], hydrometallurgy [16, 17] and polymer drug graft [18]. In addition polymer-metal complexes are also used as mechanochemical system and as models of bioinorganic systems [19, 20]
*) Auther for correspondence [email protected]
Polyacrylamides are a class of polymers formed from acrylamide alone or copolymerized with other monomers. Polyacrylamides have been used in a variety of applications, soil conditioning to reduce soil erosion, agriculture, oil recovery, biomedical applications and have been used in water treatment to improve the process of sludge thickening and dewatering as flocculants or coagulants in the highest volume among all the polymer types. In potable water treatment processes, polyacrylamides are often exposed to oxidants (e.g. chlorine and permanganate) and UV irradiation from sunlight or artificial sources. Other uses include mixing with pesticides as a thickening agent and as a medium for hydroponically grown crops, in sugar refining [21], and as a binder of bone cement [22]. Although there are numerous work on complexation of different polymers with transition metal [23, 24], only Ni2+ complex of polyacrylamide was prepared and characterized [25].
Experimental Preparation of metal complexes The complexation of the resins were investigated towards CoSO4, NiSO4, CuCl2, CrCl3, MnCl2 and FeCl3 at their neutral pH. In all the complexation studies, one gm of metals salt dissolved in 100 ml distilled water were added to one gm of polymeric ligand dissolved in 100 ml distilled water, the metal salt solution was mixed with the ligand solution, the reaction mixture was stirred for 2 hr. The complexed resins were collected by filtration, washed with distilled water and dried in a vacuum desiccators anhydrous CaCl2
instability was carried out using a Linear Swell Meter LSM 2000. Comparisons of the experimental and theoretical IR spectra were carried out besides some other theoretical calculations. Table (1): Analytical and physical properties of the ligand and its metal complexes *: Calculated / (Found ) % Sample
Color C%
H%
N%
M%
PACM
White
50.7 (50.4)
7.04 (7.0)
22.54 (22.2)
-
[Cu(ACM)6]n
Blue
45.23 (45.2)
3.77 (3.4)
17.59 (17.0)
13.31 (13.04)
[Cr(ACM)6]n
Green
46.35 (46.0)
3.86 (3.7)
18.03 (17.4)
11.16 (11.01)
[Co(ACM)6]n
Pink
45.67 (45.5)
3.81 (3.8)
17.76 (17.1)
12.46 (12.08)
[Fe(ACM)6]n
Reddish brown
45.97 (45.7)
3.83 (3.7)
17.88 (17.1)
11.89 (11.52)
[NI(ACM)6]n
Pale green
45.70 (45.7)
3.80 (3.7)
17.77 (17.0)
12.42 (12.22)
[Mn(ACM)6]n
Buff
46.06 (46.0)
3.84 (3.8)
17.91 (17.1)
11.72 (11.61)
Physical measurements Elemental analyses C, H, N contents of the synthesized complexes were analyzed by the usual method with the aid of CHN analyzer. Metal analysis for Co2+, Ni2+, Cu2+, Cr3+, Fe3+ were analyzed by Mn2+and complexometerically by EDTA titration [26]. Table 1 shows the analytical results for the polymer ligand itself and its complexes. The KBr IR spectra of ligand and the six complexes were recorded on a Perkin-Elmer spectrophotometer covering the frequency range 4,000–200 cm -1. X-band electron spin resonance spectra were recorded for Copper polymer complex only with a reflection spectrometer operating at (9.1-9.8) GHz in a cylindrical resonance cavity with 100 KHz modulation. The g-values were determined by comparison with DPPH (diphenyl picryl hydrazide) signal, the control field of the standard (DPPH) is 3300 G. The UV–Vis spectra of the solid complexes were measured in Nujol mull spectra [27]. Molar magnetic susceptibilities, corrected for diamagnetism using Pascal’s constants were determined at lab temperature (298oK). The instrument was calibrated with Hg[Co(SCN)]. The magnetic moment values were evaluatedat room temperature using a Sherwood scientific magnetic susceptibility balance. Differential thermal(DTA), differential scanning calorimetric (DSC) and thermogravimetry analysis (TG) of solid complexes were carried out using a shimadzu DTA/TG-50. The rate of heating was 10oC min-1. The cell used was platinum, and the atmospheric nitrogen rate flow was 20 mL min1 .The viscosity was carried out using a FANN VG meter Model 35 Viscometer and Brookfield HBDV-II+ PRO Digital Programmable Viscometer.Shale
*All the complexes are with melting point 0
however that of the ligand is 250 C
300 0C,
Results and discussion Infrared spectroscopy Table (2): Fundamental infrared bands (cm-1) of PACM and its complexes : ν(cm -1)
ν(cm -1)
ν(cm -1)
ν(cm -1)
ν(cm -1)
NH2
CH2(s)
C=O
N-H
C-N
PACM
3440
2925
1642
---
1453
[Cu(ACM)6]n
3447
2925
1648
1326
1453
Compound
[Ni(ACM)6]n
3442
2926
1657
1323
1450
[Cr (ACM)6]n
3444
2927
1649
1326
1453
[Fe(ACM)6]n
3443
2927
1664
1325
1453
Structure (1): The proposed structure of polyacrylamide metal complexes where M = Co2+, Ni2+, Cu2+, Cr3+, Mn2+and Fe3+ According to Mukhles Sowwan et al Ni2+complex of polyacrylamide shows that polyacrylamide act as monodendate ligand through nitrogen atom of NH2 group [25] Theoretical vibrational analysis of PACM
[Co(ACM)6]n
3442
2926
1650
1326
1453
[Mn(ACM)6]n
3442
2927
1662
1324
1451
The ν CH2, ν NH and ν CN of the ligand are of minor importance for complexation. Meanwhile, the ν C=O is of major importance for complexation followed by ν NH2 to a less extent. The ν C=O band position of PACM ligand at 1642 cm-1 [28] is changed on complexation with Cu(II),Ni(II), Cr(III), Fe(III), Co(II) and Mn(II)polymer complexes indicating its participation in complex formation. The ν NH2 band position of PACM ligand at 3440 cm-1 [29] is changed on complexation with Cu(II),Ni(II), Cr(III), Fe(III), Co(II) and Mn(II) indicating its participation in complex formation [30-32]. As a result of IR and elemental analyses results, the structure of the complexes may have octahedral geometry containing the metal coordinated to both nitrogen and oxygen atoms via resonance, Structure (1):
PACM contains amide group (H2N-C=O) can exist as keto or enol form through tautomerism of mobil hydrogen atom depending on moving atom one site (N atom) to another (O atom) in order to acquire the spectroscopic nature of PACM molecule, the frequency calculation analysis [33, 34], was made for free polymer molecule consists of three monomer units for both keto and enol forms, while experimental spectrum was performed for solid sample. It seems that there are small differences between theoretical and experimental vibrational wave numbers [35], (Figure 1). The band appears at 3440cm-1 in the experimental IR does not appear in theoretical keto form but appear in the theoretical enol form at 3509 cm-1 confirming the existence of both keto and enol forms. The correlation graphic described harmony between the theoretical wave numbers (Figure 1). The relations between the calculated and experimental wave numbers are linear and described by the following equations: For the keto form υcal = 0.993υexp+ 12.47 with correlation coefficients (R2 = 0.997) For the enol form υcal = 1.035υexp+ 84.93 with correlation coefficients (R2 = 0.998)
Theoritical wave numbers (cm1)
4000 3000
Enol form
2000
Keto form Linear (Enol form) Linear (Keto form)
1000 0 0
2000
4000
Experimental wave numbers (cm-1) Figure (1): The linear regression between the experimental and theoretical frequencies of PACM (keto and enol form)
Electron spin resonance of copper complexes: The ESR spectrum of [Cu(ACM)6]n complex, showed an anisotropic spectrum. It gave two gvalues, g║ = 4.2, g┴ = 3.55, the g value is calculated from the relation [36, 37]. g = (g║ + 2 g┴ ) / 3 = 1.42. The deviation of the g value from that of the free electron (2.0023) is due to the covalence property and also can be explained due to the expected l,s coupling in g┴ indicats that the Cu2+ complexes. g║ ground state of this complex is dx2 – y2 rather than dz2 [38, 39]. The G-value was calculated from the relation G = g║-2 / g┴ -2 to be 3.76 ( 4), indicating the existence of polymeric nature of the complex. Magnetic susceptibility and Electronic spectra of metal complexes: The electronic absorption spectrum of iron polymer complex, shows two bands at 410 and 328 nm, assigned to the 6A1g → 4T2g (G) and 6 A1g→4T2g (D) transitions, respectively as expected for an octahedral geometry [40], with μeff value 5.91 B.M due to (d5, 5 unpaired electrons) supporting the proposed geometry [41], Table (3). However, The electronic absorption spectrum of cobalt polymer complex, shows two bands at 630 and 525 nm, assigned to 4T1g (F) → 4 A2g(F) (ν2) and 4T1g(F) → 4T1g (P) (ν3) transitions, respectively as expected for an octahedral geometry [42], and with μeff value 5.92 B.M due to (d7, 3 unpaired electrons) supporting the proposed geometry[41], Table(3). Nickel polymer complex, shows two bands at 648 and 407 nm, attributable to 3 A2g(F) → 3T1g(P) (ν2) and 3A2g(F) → 3T1g(F) (ν3) transitions, respectively as expected for an
octahedral geometry [43], and with μeff value 3.2 B.M due to (d8, 2 unpaired electrons) supporting the proposed geometry[41], Table (3). Also the electronic absorption spectrum of copper polymer complex, exhibits two bands at 530 nm assigned to 2Eg→2T2g and 360 nm which attributed to symmetry forbidden ligand → metal charge transfer transition as expected for an octahedral geometry [44], The μeff value 2.21 B.M due to (d9, 1 unpaired electron) supporting the proposed geometry[41], Table(3). However, The electronic absorption spectrum of chromium polymer complex, shows two bands at 580 and 420 nm corresponding to the 4A2g(F) → 4T2g (F) and 4A2g(F) → 4T1g(F) transitions, respectively as expected for an octahedral geometry [45], and with μeff value 3.95 B.M corresponds to (d3, 3 unpaired electron) supporting the proposed geometry [41], Table (3). Also the electronic absorption spectrum of manganese polymer complex, shows three bands in 505 and 395 nm assigned to 6 A1g → 4T1g(G) and 6A1g → 4T2g(G) transitions, respectively as expected for an octahedral geometry [46]. The thired band at 222 is expected to be ligand – metal charge transfer. The μeff value 3.82 B.M, Table (3), these are less than expected value for spin only magnetically diluted Mn2+ (5.92 B.M). The data are explained by magnetically concentrated substance due to interactions between the adjacent dipoles [47]. Table (3): Electronic absorption spectra and magnetic moment values of complexes at room temperature (298oK).
Complexes
µ eff. (298oK) B.M
[Cu(ACM)6]n
2.21
[Fe(ACM)6]n
5.91
[Mn(ACM)6]n
3.82
[NI(ACM)6]n
3.2
[Co(ACM)6]n
5.92
[Cr(ACM)6]n
3.95
Band position, (cm-1)
Assignment
18867
2
27777
Eg→2T2g LMCT
24390
6
30487
A1g → 4T2g (G) 6
A1g→4T2g (D
19801
6
A1g → 4T1g(G)
25316
6
A1g → 4T2g(G)
17241
3
A2g(F) → 3T1g(P)
23809
3
A2g(F) → 3T1g(F)
15873
4
19047
4
17241
4
A2g(F) → 4T2g (F)
23809
4
A2g(F) → 4T1g(F)
T1g (F) → 4A2g(F) T1g(F) → 4T1g (P)
Suggested geometry
octahedral octahedral octahedral octahedral octahedral octahedral
Where, ΔS# represents the entropies of activation, Z value of collision number, R molar gas constant, Ø rate of heating (Ks-1), k the Boltzmann constant and h the Planck's constant [52].
THERMAL ANALYSIS TG and mechanism of decomposition Fruitful conclusions for the mechanism of decomposition are given below: The TG of PACM showed that the decomposition of the ligand occurred by one step. Where the % loss of 99.8 % was attributed to the loss of the polyacrylamide. An inert residue of 0.2 % was left (Calc 0 %). The following scheme for the decomposition of this ligand is suggested:
The change of entropy values, ΔS#, for all complexes, are nearly of the same magnitude and lie within the range -0.293 to -0.284 kJ K-1 mol-1, all are with –ve signs, Table 4. So, the transition states are more ordered, i.e. in a less random molecular configuration, than the reacting complexes. The change in enthalpy (ΔH#) for any phase transformation [53, 54] taking place at any peak temperature, Tm, can be given by the following equation: ΔS# = ΔH#/Tm. All the ΔH# values are with -ve signs, Table 5.
-n (ACM) inert residue
(ACM) n 0
50 – 500 C The fragmentation by TG of [M(ACM)6]n occurred by two step mechanism, where the first % loss attributed to the loss of 6(C2H5N) and second % loss attributed to the loss of 6(CO). A residue was left as M. The following scheme for the decomposition of complexes are suggested: -6 (C2H5N) [M(ACM)6]n
[Co(ACM)6]n EXO
lnΔT
[Co(ACM)6]n ENDO
4
-6(CO) M(CO)6
data of DTA and TG of polyacrylamide (PACM) and its metal complexes are given in Tables (4, 5). Figure 2 shows the relation between the polymer ligand and its metals complexes
[Cr(ACM)6]n [Cu(ACM)6]n
M
[Fe(ACM)6]n
3
PACM
Differential thermal analysis (DTA):
[Mn(ACM)6]n
2
[Ni(ACM)6]n
The order of chemical reactions (n) was calculated via the peak symmetry method [48]. The reaction orders are 1 and 1.5. The fractions appeared in the calculated order of the thermal reactions, (n), Table 5, confirmed that the mechanisms proceeded in complicated mechanisms. The maximum and the minimum Tm values are 515.1 and 3780K, respectively. The values of the decomposed substance fraction, αm [49, 50] at the moment of maximum development of reaction (with T = Tm) are being of nearly the same magnitude and lies within the range 0.552– 0.675, Table 5. Based on least square calculations, the Ln ΔT versus 103/T plots for the complexes, for each DTA curve, gave straight lines from which the activation energies (Ea) were calculated [51]. The slope depicts Arrhenius type.
z=
⎛ E ⎞ kT ⎛ ΔS # ⎞ Ea ⎟⎟ φ exp⎜⎜ a 2 ⎟⎟ = m exp⎜⎜ RTm h ⎝ R ⎠ ⎝ RTm ⎠
1 0 1.3
1.4
1.5
-1 -2 Figure (2): lnΔT - 10^3/T relation between the parent PACM and [M(ACM)6]n]
1.6 10^3/T
Table (4): The TGA data of polyacrylamide (PACM) and its metals complexes: Wt loss %
Temp. TGA
Compound PACM [Cu(ACM)6]n [Co (ACM)6]n [Cr(ACM)6]n [Ni(ACM)6]n [Fe(ACM)6]n [Mn(ACM)6]n
Calc.
Assignment
Found
500
0
0.2
inert residue
450
53.36
52.79
- 6C2H5N
550
33.33
33.91
- 6CO
410
53.8
53.6
- 6C2H5N
510
33.74
34.5
- 6CO
552
88.84
88.9
-6(ACM)
457
54.0
53.6
- 6C2H5N
520
33.58
33.8
- 6CO
430
54.3
53.5
- 6C2H5N
510
33.81
34.3
- 6CO
295
54.3
53.9
- 6C2H5N
560
33.98
34.2
- 6CO
Table (5): The DTA data of polyacrylamide (PACM) and its metal complexes: Compound
type
slope
Tm °C
Ea KJmol-1
n
αm
ΔS KJK1mol-1
ΔH KJmol-1
Z Sec-1
PACM
Exo
-28.45
455.65
236.5
1.52
0.552
-0.290
-132.43
0.062
[Cu(ACM)6]n
Exo
-33.16
508.73
275.7
1.32
0.579
-0.291
-148.14
0.065
Exo
-27.04
513.0
224.8
0.98
0.637
-0.293
-150.33
0.053
Endo
-46.25
378
384.5
1.3
0.576
-0.284
-107.16
0.122
[Cr(ACM)6]n
Exo
-29.20
484.9
242.8
1.2
0.598
-0.291
-143.22
0.060
[Ni(ACM)6]n
Exo
-26.6
515.08
221.2
0.98
0.635
-0.293
-151.04
0.052
[Fe(ACM)6]n
Exo
-29.6
473.36
246.1
1.08
0.618
-0.290
-137.72
0.063
[Mn(ACM)6]n
Exo
-28.0
486
232.8
0.78
0.675
-0.291
-141.84
0.057
[Co (ACM)6]n
Differential Scanning Calorimetry The DSC curves are obtained for PACM and its complexes with Cu(II), Ni(II), Cr(III), Fe(III), Co(II) and Mn(II) are given in table (6), which are done under a flow of N2 at heating rate 10oC/min in the temperature range 0-400 oC. The glass transition temperature (Tg) does not appear for PACM and its complexes, where the melting temperature (Tm) for all are present in region 275 - 345 oC [55]. However, strong endothermic peak in the region 50 – 105 oC, is probable due to adsorbed water or there were impurities present in the sample.
Table (7): The variation of a, b, α and γfor PACM and its complexes according to Debye model: Cp = aT + b Compound PAMs [Cu(ACM)6]n [Cr(ACM)6]n [Co(ACM)6]n [Fe(ACM)6]n [Ni(ACM)6]n [Mn(ACM)6]n
a - 0.36 - 0.422 - 0.164 - 0.135 - 0.238 - 0.204 - 0.245
b 126.4 207.5 60.63 27.21 107.5 74.86 95.75
Cp/ T = α T2 + γ α x 10-7 - 5.0 - 5.0 - 2.0 - 0.7 - 2.0 - 2.0 - 2.0
γ 0.008 0.097 - 0.009 - 0.063 0.028 - 0.019 0.001
Table (6): Melting points of PACM and its complexes deduced from DSC: Sample PAMs [Cu(ACM)6]n [Cr(ACM)6]n [Co(ACM)6]n [Fe(ACM)6]n [Ni(ACM)6]n [Mn(ACM)6]n
Melting temperature 0 C 274 336 323 342 345 341 320
The Debye model [55] is applied to describe capacity change over a large temperature range, and Cp can be represented by the following empirical form: Cp = aT + b. By plotting Cp versus T, a straight line is obtained, thus, ‘‘a’’ and ‘‘b’’ parameters can be determined from the slope and intercept of the line, respectively, Figs. 3 (a) and (b) as representative examples. The applications based on Debye model on selected complexes are given from the scope of the following equations: Cp ؆ Cv = αT3 + γT Cp/ T = αT2 + γ where γ and α are the coefficients of electronic and lattice heat capacities, respectively. Cv is the heat capacity at constant volume which is assumed to be equal to Cp. Plots of Cp/T versus T2 should yield straight lines with slopes α and intercepts γ, Figs. 4 (a) and (b) as representative examples.
Figure (3): a. Dependence of Cp on T for [Cu(ACM)6]n b. Expanded Dependence of Cp in the range (-42.9: -47.8 JK-1 ) on T for[Cu(ACM)6]n
Table (8): Rheological parameter of 2ppb PACM at 298 OK.
600
rpm
After Mixing 60
300
rpm
40
200
rpm
35
100
rpm
25
6
rpm
15
rpm
13
MUD PARAMETER
3 PV YP
0
@ 120 F 0
@ 120 F
BROOKFIELD LVT VISCOMETER : LV3 SPINDLE @ 0.3 RPM , in thousands
UNIT
cP lb/100ft cP
20 2
20 62.0
YP = 20 lb/100ft2 and BROOKFIELD reading = 1600 cP implies that the fluid has ability to carry cuttings. Shale instability
Figure (4): a. DSC curve Cp/T versus T2for [Cu(ACM)6]n. b. Expanded DSC curve Cp/T versus T2 in temperature range (319 – 331 oC)for [Cu(ACM)6]n Application of polyacrylamide Viscosity The rheological parameter of 2 ppb PACM at 298 OK is shown in Table (8)
Shales make up over 75% of the drilled formations, and over 70% of the borehole problems are related to shale instability. The oil and gas industry still continues to fight borehole problems. The problems include hole collapse, tight hole, stuck pipe, poor hole cleaning, hole enlargement, plastic flow, fracturing, lost circulation, well control. Most of the drilling problems that drive up the drilling costs are related to wellbore stability [56-58]. LSM tests measure shale hydration or dehydration of reconstituted or intact shale core exposed to drilling fluid. The LSM software plots a graph of the percentage of swelling versus swelling time (minutes). The Linear Swell Meter data of 2 ppb PACM against water is shown in Fig (22)
Table (9): Net Mulliken atomic charges : a)
Keto form
Atom
Figure (5): Linear Swell Meter data of 2 ppb PACM against water
However, from Figure (5) PACM have lower shale swelling than water, indicating that PACM is effective in shale swelling reduction (shale stability).
C(1) O(2) N(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) O(13) N(14) C(15) O(16) N(17) H(18) H(19)
(a) Enol form
Atom H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) H(31) H(32) H(33) H(34) H(35) H(36) H(37) H(38)
Net atomic charge 0.193693 0.170487 0.192784 0.199964 0.197781 0.203545 0.209492 0.194658 0.223696 0.19368 0.194929 0.209912 0.188115 0.17417 0.196878 0.303726 0.332454 0.304003 0.322687
b) Enol form Atom
Molecular Modeling
Net atomic charge 0.721992 -0.533033 -0.754051 -0.560313 -0.342107 -0.357567 -0.295705 -0.341474 -0.284724 -0.349399 -0.506902 0.683941 -0.539126 -0.765577 0.670368 -0.514192 -0.773681 0.319619 0.315275
C(1) O(2) N(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) O(13) N(14) C(15) O(16) N(17) H(18) H(19)
Net atomic charge 0.590059 -0.58625 -0.65576 -0.57728 -0.52593 -0.30489 -0.44421 -0.29443 -0.54198 -0.25628 -0.55083 0.642094 -0.59322 -0.63799 0.571653 -0.61766 -0.69833 0.382665 0.267863
Atom H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) H(31) H(32) H(33) H(34) H(35) H(36) H(37) H(38)
Net atomic charge 0.217785 0.226416 0.182956 0.236293 0.226031 0.388263 0.200826 0.203944 0.28803 0.245267 0.211315 0.43519 0.218474 0.179689 0.179422 0.37285 0.239351 0.357813 0.220784
(b) Keto form
Mulliken population analysis
Figure (6): Modeling structure of PACM
The charge distribution calculation of the molecule depicts the charges of every atom in the molecule. In addition, the charge distribution on the molecule has an important influence on the vibrational spectra. Distribution of positive and negative charges is the vital to increasing or decreasing of bond length between the atoms. The survey of literature reveals that effective atomic calculations gave an important role in the application of chemical calculation to molecular system because of atomic charges,
0.6 0.4 0.2 0.0
-0.2 -0.4
C(6) C(7) C(8) C(9) C(12) O(13) N(14) H(26) H(27) H(28) H(35) H(36)
Mulliken atomic charge (electronic charge)
0.8
-0.6 -0.8 -1.0
Atom no.
Figure (7): Mulliken’s charge plot of PACM (keto form)
0.8 0.6 0.4 0.2 0.0 -0.2
C(6) C(7) C(8) C(9) C(12) O(13) N(14) H(26) H(27) H(28) H(35) H(36)
Mulliken atomic charge (electronic charge)
dipole moment, molecular polarizability, electronic structure, acidity-basicity behavior and many properties of molecular system [59-63]. Mulliken atomic charges calculated by DFT method is collected and shown by the corresponding Mulliken’s plots (Figures 7, 8). It is worth mentioning that C(12), H(26), H(27), H(28), H(35) and H(36) atoms of keto form exhibit positive charge and became more acidic, while C(6), C(7), C(8), C(9), O(13) and N(14) atoms exhibit negative charges. O(13) and N(14) have a maximum negative charges value about -0.5391 and -0.7656 respectively. The maximum positive atomic charge is obtained for C(12) which is carbon atom present in the functional group (C-N) and (C=0). For the enol form C(12), H(26), H(27), H(28), H(35) and H(36) atoms exhibits positive charge, while C(6), C(7), C(8), C(9), O(13) and N(14) atoms exhibit negative charges. O(13) and N(14) have a maximum negative charges value about - 0.5932 and - 0.638 respectively. The maximum positive charge is obtained for C(12) which is carbon atom present in the functional group (C-N) and (C=0).
-0.4 -0.6 -0.8
Atom no.
Figure (8): Mulliken’s charge plot of PACM (enol form)
Conclusions The preparation of polyacrylamide complexes with CoSO4, NiSO4, CuCl2, CrCl3, MnCl2 and FeCl3. The analytical data depict the formation of complexes with stoichiometry, (1:6) (Metal : monomer Ligand) and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggests octahedral geometry for all complexes. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ∆S# values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing 6(C2H5N) and 6(CO). The metal complexes are ended with metal as a final product. Viscosity and Shale instability using liner swell meter instrument. Comparisons of the experimental and theoretical IR spectra were carried out besides some other theoretical calculations.
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Graphical Abstract
Highlights • Co2+, Ni2+,Cu2+, Cr3+, Mn2+ and Fe3+
complexes of polyacrylamide were prepared.
• The six polymer complexes were characterized by different measurements.
• Some applications of polyacrylamide were done.
S0022-2860(15)00325-7 http://dx.doi.org/10.1016/j.molstruc.2015.04.007 MOLSTR 21461
To appear in:
Journal of Molecular Structure
Received Date: Revised Date: Accepted Date:
25 December 2014 4 April 2015 6 April 2015
Please cite this article as: M.S. Masoud, A.E.H. Abdou, W.M. Ahmed, Synthesis and characterization of some transition metals polymer complexes, Journal of Molecular Structure (2015), doi: http://dx.doi.org/10.1016/ j.molstruc.2015.04.007
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Synthesis and characterization of some transition metals polymer complexes Mamdouh S. Masouda, Azza E. H. Abdoua*& Wael M. Ahmeda a) Faculty of Science, Chemistry departement, Alexandria university
Abstract
Co2+, Ni2+, Cu2+, Cr3+, Mn2+and Fe3+complexes of Polyacrylamide are prepared and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggests octahedral geometry for all complexes. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ∆S# values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing 6(C2H5N) and 6(CO), the metal complexes are ended with metal as a final product. Viscosity and Shale instability using liner swell meter were carried out. Comparisons of the experimental and theoretical IR spectra were also carried out besides some other theoretical calculations. Keywords: Polyacrylamide, thermal analyses, spectra, elemental analyses, metal polymer complexes.
Introduction Study of the polymer-metal complexes has received increased interest in various branches of chemistry, chemical technology and biology and the subject has been reviewed periodically [1-4]. The chelating polymers find applications in collecting transition metal ions as well as alkali and alkaline earth metal ion separation [5] preconcentration and recovery of trace metal ions [6], catalysis [7,8] , organic synthesis[9,10], nuclear chemistry [11], water and waste water-treatment [12,13], pollution control [14], industrial processes[15], hydrometallurgy [16, 17] and polymer drug graft [18]. In addition polymer-metal complexes are also used as mechanochemical system and as models of bioinorganic systems [19, 20]
*) Auther for correspondence [email protected]
Polyacrylamides are a class of polymers formed from acrylamide alone or copolymerized with other monomers. Polyacrylamides have been used in a variety of applications, soil conditioning to reduce soil erosion, agriculture, oil recovery, biomedical applications and have been used in water treatment to improve the process of sludge thickening and dewatering as flocculants or coagulants in the highest volume among all the polymer types. In potable water treatment processes, polyacrylamides are often exposed to oxidants (e.g. chlorine and permanganate) and UV irradiation from sunlight or artificial sources. Other uses include mixing with pesticides as a thickening agent and as a medium for hydroponically grown crops, in sugar refining [21], and as a binder of bone cement [22]. Although there are numerous work on complexation of different polymers with transition metal [23, 24], only Ni2+ complex of polyacrylamide was prepared and characterized [25].
Experimental Preparation of metal complexes The complexation of the resins were investigated towards CoSO4, NiSO4, CuCl2, CrCl3, MnCl2 and FeCl3 at their neutral pH. In all the complexation studies, one gm of metals salt dissolved in 100 ml distilled water were added to one gm of polymeric ligand dissolved in 100 ml distilled water, the metal salt solution was mixed with the ligand solution, the reaction mixture was stirred for 2 hr. The complexed resins were collected by filtration, washed with distilled water and dried in a vacuum desiccators anhydrous CaCl2
instability was carried out using a Linear Swell Meter LSM 2000. Comparisons of the experimental and theoretical IR spectra were carried out besides some other theoretical calculations. Table (1): Analytical and physical properties of the ligand and its metal complexes *: Calculated / (Found ) % Sample
Color C%
H%
N%
M%
PACM
White
50.7 (50.4)
7.04 (7.0)
22.54 (22.2)
-
[Cu(ACM)6]n
Blue
45.23 (45.2)
3.77 (3.4)
17.59 (17.0)
13.31 (13.04)
[Cr(ACM)6]n
Green
46.35 (46.0)
3.86 (3.7)
18.03 (17.4)
11.16 (11.01)
[Co(ACM)6]n
Pink
45.67 (45.5)
3.81 (3.8)
17.76 (17.1)
12.46 (12.08)
[Fe(ACM)6]n
Reddish brown
45.97 (45.7)
3.83 (3.7)
17.88 (17.1)
11.89 (11.52)
[NI(ACM)6]n
Pale green
45.70 (45.7)
3.80 (3.7)
17.77 (17.0)
12.42 (12.22)
[Mn(ACM)6]n
Buff
46.06 (46.0)
3.84 (3.8)
17.91 (17.1)
11.72 (11.61)
Physical measurements Elemental analyses C, H, N contents of the synthesized complexes were analyzed by the usual method with the aid of CHN analyzer. Metal analysis for Co2+, Ni2+, Cu2+, Cr3+, Fe3+ were analyzed by Mn2+and complexometerically by EDTA titration [26]. Table 1 shows the analytical results for the polymer ligand itself and its complexes. The KBr IR spectra of ligand and the six complexes were recorded on a Perkin-Elmer spectrophotometer covering the frequency range 4,000–200 cm -1. X-band electron spin resonance spectra were recorded for Copper polymer complex only with a reflection spectrometer operating at (9.1-9.8) GHz in a cylindrical resonance cavity with 100 KHz modulation. The g-values were determined by comparison with DPPH (diphenyl picryl hydrazide) signal, the control field of the standard (DPPH) is 3300 G. The UV–Vis spectra of the solid complexes were measured in Nujol mull spectra [27]. Molar magnetic susceptibilities, corrected for diamagnetism using Pascal’s constants were determined at lab temperature (298oK). The instrument was calibrated with Hg[Co(SCN)]. The magnetic moment values were evaluatedat room temperature using a Sherwood scientific magnetic susceptibility balance. Differential thermal(DTA), differential scanning calorimetric (DSC) and thermogravimetry analysis (TG) of solid complexes were carried out using a shimadzu DTA/TG-50. The rate of heating was 10oC min-1. The cell used was platinum, and the atmospheric nitrogen rate flow was 20 mL min1 .The viscosity was carried out using a FANN VG meter Model 35 Viscometer and Brookfield HBDV-II+ PRO Digital Programmable Viscometer.Shale
*All the complexes are with melting point 0
however that of the ligand is 250 C
300 0C,
Results and discussion Infrared spectroscopy Table (2): Fundamental infrared bands (cm-1) of PACM and its complexes : ν(cm -1)
ν(cm -1)
ν(cm -1)
ν(cm -1)
ν(cm -1)
NH2
CH2(s)
C=O
N-H
C-N
PACM
3440
2925
1642
---
1453
[Cu(ACM)6]n
3447
2925
1648
1326
1453
Compound
[Ni(ACM)6]n
3442
2926
1657
1323
1450
[Cr (ACM)6]n
3444
2927
1649
1326
1453
[Fe(ACM)6]n
3443
2927
1664
1325
1453
Structure (1): The proposed structure of polyacrylamide metal complexes where M = Co2+, Ni2+, Cu2+, Cr3+, Mn2+and Fe3+ According to Mukhles Sowwan et al Ni2+complex of polyacrylamide shows that polyacrylamide act as monodendate ligand through nitrogen atom of NH2 group [25] Theoretical vibrational analysis of PACM
[Co(ACM)6]n
3442
2926
1650
1326
1453
[Mn(ACM)6]n
3442
2927
1662
1324
1451
The ν CH2, ν NH and ν CN of the ligand are of minor importance for complexation. Meanwhile, the ν C=O is of major importance for complexation followed by ν NH2 to a less extent. The ν C=O band position of PACM ligand at 1642 cm-1 [28] is changed on complexation with Cu(II),Ni(II), Cr(III), Fe(III), Co(II) and Mn(II)polymer complexes indicating its participation in complex formation. The ν NH2 band position of PACM ligand at 3440 cm-1 [29] is changed on complexation with Cu(II),Ni(II), Cr(III), Fe(III), Co(II) and Mn(II) indicating its participation in complex formation [30-32]. As a result of IR and elemental analyses results, the structure of the complexes may have octahedral geometry containing the metal coordinated to both nitrogen and oxygen atoms via resonance, Structure (1):
PACM contains amide group (H2N-C=O) can exist as keto or enol form through tautomerism of mobil hydrogen atom depending on moving atom one site (N atom) to another (O atom) in order to acquire the spectroscopic nature of PACM molecule, the frequency calculation analysis [33, 34], was made for free polymer molecule consists of three monomer units for both keto and enol forms, while experimental spectrum was performed for solid sample. It seems that there are small differences between theoretical and experimental vibrational wave numbers [35], (Figure 1). The band appears at 3440cm-1 in the experimental IR does not appear in theoretical keto form but appear in the theoretical enol form at 3509 cm-1 confirming the existence of both keto and enol forms. The correlation graphic described harmony between the theoretical wave numbers (Figure 1). The relations between the calculated and experimental wave numbers are linear and described by the following equations: For the keto form υcal = 0.993υexp+ 12.47 with correlation coefficients (R2 = 0.997) For the enol form υcal = 1.035υexp+ 84.93 with correlation coefficients (R2 = 0.998)
Theoritical wave numbers (cm1)
4000 3000
Enol form
2000
Keto form Linear (Enol form) Linear (Keto form)
1000 0 0
2000
4000
Experimental wave numbers (cm-1) Figure (1): The linear regression between the experimental and theoretical frequencies of PACM (keto and enol form)
Electron spin resonance of copper complexes: The ESR spectrum of [Cu(ACM)6]n complex, showed an anisotropic spectrum. It gave two gvalues, g║ = 4.2, g┴ = 3.55, the g value is calculated from the relation [36, 37]. g = (g║ + 2 g┴ ) / 3 = 1.42. The deviation of the g value from that of the free electron (2.0023) is due to the covalence property and also can be explained due to the expected l,s coupling in g┴ indicats that the Cu2+ complexes. g║ ground state of this complex is dx2 – y2 rather than dz2 [38, 39]. The G-value was calculated from the relation G = g║-2 / g┴ -2 to be 3.76 ( 4), indicating the existence of polymeric nature of the complex. Magnetic susceptibility and Electronic spectra of metal complexes: The electronic absorption spectrum of iron polymer complex, shows two bands at 410 and 328 nm, assigned to the 6A1g → 4T2g (G) and 6 A1g→4T2g (D) transitions, respectively as expected for an octahedral geometry [40], with μeff value 5.91 B.M due to (d5, 5 unpaired electrons) supporting the proposed geometry [41], Table (3). However, The electronic absorption spectrum of cobalt polymer complex, shows two bands at 630 and 525 nm, assigned to 4T1g (F) → 4 A2g(F) (ν2) and 4T1g(F) → 4T1g (P) (ν3) transitions, respectively as expected for an octahedral geometry [42], and with μeff value 5.92 B.M due to (d7, 3 unpaired electrons) supporting the proposed geometry[41], Table(3). Nickel polymer complex, shows two bands at 648 and 407 nm, attributable to 3 A2g(F) → 3T1g(P) (ν2) and 3A2g(F) → 3T1g(F) (ν3) transitions, respectively as expected for an
octahedral geometry [43], and with μeff value 3.2 B.M due to (d8, 2 unpaired electrons) supporting the proposed geometry[41], Table (3). Also the electronic absorption spectrum of copper polymer complex, exhibits two bands at 530 nm assigned to 2Eg→2T2g and 360 nm which attributed to symmetry forbidden ligand → metal charge transfer transition as expected for an octahedral geometry [44], The μeff value 2.21 B.M due to (d9, 1 unpaired electron) supporting the proposed geometry[41], Table(3). However, The electronic absorption spectrum of chromium polymer complex, shows two bands at 580 and 420 nm corresponding to the 4A2g(F) → 4T2g (F) and 4A2g(F) → 4T1g(F) transitions, respectively as expected for an octahedral geometry [45], and with μeff value 3.95 B.M corresponds to (d3, 3 unpaired electron) supporting the proposed geometry [41], Table (3). Also the electronic absorption spectrum of manganese polymer complex, shows three bands in 505 and 395 nm assigned to 6 A1g → 4T1g(G) and 6A1g → 4T2g(G) transitions, respectively as expected for an octahedral geometry [46]. The thired band at 222 is expected to be ligand – metal charge transfer. The μeff value 3.82 B.M, Table (3), these are less than expected value for spin only magnetically diluted Mn2+ (5.92 B.M). The data are explained by magnetically concentrated substance due to interactions between the adjacent dipoles [47]. Table (3): Electronic absorption spectra and magnetic moment values of complexes at room temperature (298oK).
Complexes
µ eff. (298oK) B.M
[Cu(ACM)6]n
2.21
[Fe(ACM)6]n
5.91
[Mn(ACM)6]n
3.82
[NI(ACM)6]n
3.2
[Co(ACM)6]n
5.92
[Cr(ACM)6]n
3.95
Band position, (cm-1)
Assignment
18867
2
27777
Eg→2T2g LMCT
24390
6
30487
A1g → 4T2g (G) 6
A1g→4T2g (D
19801
6
A1g → 4T1g(G)
25316
6
A1g → 4T2g(G)
17241
3
A2g(F) → 3T1g(P)
23809
3
A2g(F) → 3T1g(F)
15873
4
19047
4
17241
4
A2g(F) → 4T2g (F)
23809
4
A2g(F) → 4T1g(F)
T1g (F) → 4A2g(F) T1g(F) → 4T1g (P)
Suggested geometry
octahedral octahedral octahedral octahedral octahedral octahedral
Where, ΔS# represents the entropies of activation, Z value of collision number, R molar gas constant, Ø rate of heating (Ks-1), k the Boltzmann constant and h the Planck's constant [52].
THERMAL ANALYSIS TG and mechanism of decomposition Fruitful conclusions for the mechanism of decomposition are given below: The TG of PACM showed that the decomposition of the ligand occurred by one step. Where the % loss of 99.8 % was attributed to the loss of the polyacrylamide. An inert residue of 0.2 % was left (Calc 0 %). The following scheme for the decomposition of this ligand is suggested:
The change of entropy values, ΔS#, for all complexes, are nearly of the same magnitude and lie within the range -0.293 to -0.284 kJ K-1 mol-1, all are with –ve signs, Table 4. So, the transition states are more ordered, i.e. in a less random molecular configuration, than the reacting complexes. The change in enthalpy (ΔH#) for any phase transformation [53, 54] taking place at any peak temperature, Tm, can be given by the following equation: ΔS# = ΔH#/Tm. All the ΔH# values are with -ve signs, Table 5.
-n (ACM) inert residue
(ACM) n 0
50 – 500 C The fragmentation by TG of [M(ACM)6]n occurred by two step mechanism, where the first % loss attributed to the loss of 6(C2H5N) and second % loss attributed to the loss of 6(CO). A residue was left as M. The following scheme for the decomposition of complexes are suggested: -6 (C2H5N) [M(ACM)6]n
[Co(ACM)6]n EXO
lnΔT
[Co(ACM)6]n ENDO
4
-6(CO) M(CO)6
data of DTA and TG of polyacrylamide (PACM) and its metal complexes are given in Tables (4, 5). Figure 2 shows the relation between the polymer ligand and its metals complexes
[Cr(ACM)6]n [Cu(ACM)6]n
M
[Fe(ACM)6]n
3
PACM
Differential thermal analysis (DTA):
[Mn(ACM)6]n
2
[Ni(ACM)6]n
The order of chemical reactions (n) was calculated via the peak symmetry method [48]. The reaction orders are 1 and 1.5. The fractions appeared in the calculated order of the thermal reactions, (n), Table 5, confirmed that the mechanisms proceeded in complicated mechanisms. The maximum and the minimum Tm values are 515.1 and 3780K, respectively. The values of the decomposed substance fraction, αm [49, 50] at the moment of maximum development of reaction (with T = Tm) are being of nearly the same magnitude and lies within the range 0.552– 0.675, Table 5. Based on least square calculations, the Ln ΔT versus 103/T plots for the complexes, for each DTA curve, gave straight lines from which the activation energies (Ea) were calculated [51]. The slope depicts Arrhenius type.
z=
⎛ E ⎞ kT ⎛ ΔS # ⎞ Ea ⎟⎟ φ exp⎜⎜ a 2 ⎟⎟ = m exp⎜⎜ RTm h ⎝ R ⎠ ⎝ RTm ⎠
1 0 1.3
1.4
1.5
-1 -2 Figure (2): lnΔT - 10^3/T relation between the parent PACM and [M(ACM)6]n]
1.6 10^3/T
Table (4): The TGA data of polyacrylamide (PACM) and its metals complexes: Wt loss %
Temp. TGA
Compound PACM [Cu(ACM)6]n [Co (ACM)6]n [Cr(ACM)6]n [Ni(ACM)6]n [Fe(ACM)6]n [Mn(ACM)6]n
Calc.
Assignment
Found
500
0
0.2
inert residue
450
53.36
52.79
- 6C2H5N
550
33.33
33.91
- 6CO
410
53.8
53.6
- 6C2H5N
510
33.74
34.5
- 6CO
552
88.84
88.9
-6(ACM)
457
54.0
53.6
- 6C2H5N
520
33.58
33.8
- 6CO
430
54.3
53.5
- 6C2H5N
510
33.81
34.3
- 6CO
295
54.3
53.9
- 6C2H5N
560
33.98
34.2
- 6CO
Table (5): The DTA data of polyacrylamide (PACM) and its metal complexes: Compound
type
slope
Tm °C
Ea KJmol-1
n
αm
ΔS KJK1mol-1
ΔH KJmol-1
Z Sec-1
PACM
Exo
-28.45
455.65
236.5
1.52
0.552
-0.290
-132.43
0.062
[Cu(ACM)6]n
Exo
-33.16
508.73
275.7
1.32
0.579
-0.291
-148.14
0.065
Exo
-27.04
513.0
224.8
0.98
0.637
-0.293
-150.33
0.053
Endo
-46.25
378
384.5
1.3
0.576
-0.284
-107.16
0.122
[Cr(ACM)6]n
Exo
-29.20
484.9
242.8
1.2
0.598
-0.291
-143.22
0.060
[Ni(ACM)6]n
Exo
-26.6
515.08
221.2
0.98
0.635
-0.293
-151.04
0.052
[Fe(ACM)6]n
Exo
-29.6
473.36
246.1
1.08
0.618
-0.290
-137.72
0.063
[Mn(ACM)6]n
Exo
-28.0
486
232.8
0.78
0.675
-0.291
-141.84
0.057
[Co (ACM)6]n
Differential Scanning Calorimetry The DSC curves are obtained for PACM and its complexes with Cu(II), Ni(II), Cr(III), Fe(III), Co(II) and Mn(II) are given in table (6), which are done under a flow of N2 at heating rate 10oC/min in the temperature range 0-400 oC. The glass transition temperature (Tg) does not appear for PACM and its complexes, where the melting temperature (Tm) for all are present in region 275 - 345 oC [55]. However, strong endothermic peak in the region 50 – 105 oC, is probable due to adsorbed water or there were impurities present in the sample.
Table (7): The variation of a, b, α and γfor PACM and its complexes according to Debye model: Cp = aT + b Compound PAMs [Cu(ACM)6]n [Cr(ACM)6]n [Co(ACM)6]n [Fe(ACM)6]n [Ni(ACM)6]n [Mn(ACM)6]n
a - 0.36 - 0.422 - 0.164 - 0.135 - 0.238 - 0.204 - 0.245
b 126.4 207.5 60.63 27.21 107.5 74.86 95.75
Cp/ T = α T2 + γ α x 10-7 - 5.0 - 5.0 - 2.0 - 0.7 - 2.0 - 2.0 - 2.0
γ 0.008 0.097 - 0.009 - 0.063 0.028 - 0.019 0.001
Table (6): Melting points of PACM and its complexes deduced from DSC: Sample PAMs [Cu(ACM)6]n [Cr(ACM)6]n [Co(ACM)6]n [Fe(ACM)6]n [Ni(ACM)6]n [Mn(ACM)6]n
Melting temperature 0 C 274 336 323 342 345 341 320
The Debye model [55] is applied to describe capacity change over a large temperature range, and Cp can be represented by the following empirical form: Cp = aT + b. By plotting Cp versus T, a straight line is obtained, thus, ‘‘a’’ and ‘‘b’’ parameters can be determined from the slope and intercept of the line, respectively, Figs. 3 (a) and (b) as representative examples. The applications based on Debye model on selected complexes are given from the scope of the following equations: Cp ؆ Cv = αT3 + γT Cp/ T = αT2 + γ where γ and α are the coefficients of electronic and lattice heat capacities, respectively. Cv is the heat capacity at constant volume which is assumed to be equal to Cp. Plots of Cp/T versus T2 should yield straight lines with slopes α and intercepts γ, Figs. 4 (a) and (b) as representative examples.
Figure (3): a. Dependence of Cp on T for [Cu(ACM)6]n b. Expanded Dependence of Cp in the range (-42.9: -47.8 JK-1 ) on T for[Cu(ACM)6]n
Table (8): Rheological parameter of 2ppb PACM at 298 OK.
600
rpm
After Mixing 60
300
rpm
40
200
rpm
35
100
rpm
25
6
rpm
15
rpm
13
MUD PARAMETER
3 PV YP
0
@ 120 F 0
@ 120 F
BROOKFIELD LVT VISCOMETER : LV3 SPINDLE @ 0.3 RPM , in thousands
UNIT
cP lb/100ft cP
20 2
20 62.0
YP = 20 lb/100ft2 and BROOKFIELD reading = 1600 cP implies that the fluid has ability to carry cuttings. Shale instability
Figure (4): a. DSC curve Cp/T versus T2for [Cu(ACM)6]n. b. Expanded DSC curve Cp/T versus T2 in temperature range (319 – 331 oC)for [Cu(ACM)6]n Application of polyacrylamide Viscosity The rheological parameter of 2 ppb PACM at 298 OK is shown in Table (8)
Shales make up over 75% of the drilled formations, and over 70% of the borehole problems are related to shale instability. The oil and gas industry still continues to fight borehole problems. The problems include hole collapse, tight hole, stuck pipe, poor hole cleaning, hole enlargement, plastic flow, fracturing, lost circulation, well control. Most of the drilling problems that drive up the drilling costs are related to wellbore stability [56-58]. LSM tests measure shale hydration or dehydration of reconstituted or intact shale core exposed to drilling fluid. The LSM software plots a graph of the percentage of swelling versus swelling time (minutes). The Linear Swell Meter data of 2 ppb PACM against water is shown in Fig (22)
Table (9): Net Mulliken atomic charges : a)
Keto form
Atom
Figure (5): Linear Swell Meter data of 2 ppb PACM against water
However, from Figure (5) PACM have lower shale swelling than water, indicating that PACM is effective in shale swelling reduction (shale stability).
C(1) O(2) N(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) O(13) N(14) C(15) O(16) N(17) H(18) H(19)
(a) Enol form
Atom H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) H(31) H(32) H(33) H(34) H(35) H(36) H(37) H(38)
Net atomic charge 0.193693 0.170487 0.192784 0.199964 0.197781 0.203545 0.209492 0.194658 0.223696 0.19368 0.194929 0.209912 0.188115 0.17417 0.196878 0.303726 0.332454 0.304003 0.322687
b) Enol form Atom
Molecular Modeling
Net atomic charge 0.721992 -0.533033 -0.754051 -0.560313 -0.342107 -0.357567 -0.295705 -0.341474 -0.284724 -0.349399 -0.506902 0.683941 -0.539126 -0.765577 0.670368 -0.514192 -0.773681 0.319619 0.315275
C(1) O(2) N(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) O(13) N(14) C(15) O(16) N(17) H(18) H(19)
Net atomic charge 0.590059 -0.58625 -0.65576 -0.57728 -0.52593 -0.30489 -0.44421 -0.29443 -0.54198 -0.25628 -0.55083 0.642094 -0.59322 -0.63799 0.571653 -0.61766 -0.69833 0.382665 0.267863
Atom H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) H(31) H(32) H(33) H(34) H(35) H(36) H(37) H(38)
Net atomic charge 0.217785 0.226416 0.182956 0.236293 0.226031 0.388263 0.200826 0.203944 0.28803 0.245267 0.211315 0.43519 0.218474 0.179689 0.179422 0.37285 0.239351 0.357813 0.220784
(b) Keto form
Mulliken population analysis
Figure (6): Modeling structure of PACM
The charge distribution calculation of the molecule depicts the charges of every atom in the molecule. In addition, the charge distribution on the molecule has an important influence on the vibrational spectra. Distribution of positive and negative charges is the vital to increasing or decreasing of bond length between the atoms. The survey of literature reveals that effective atomic calculations gave an important role in the application of chemical calculation to molecular system because of atomic charges,
0.6 0.4 0.2 0.0
-0.2 -0.4
C(6) C(7) C(8) C(9) C(12) O(13) N(14) H(26) H(27) H(28) H(35) H(36)
Mulliken atomic charge (electronic charge)
0.8
-0.6 -0.8 -1.0
Atom no.
Figure (7): Mulliken’s charge plot of PACM (keto form)
0.8 0.6 0.4 0.2 0.0 -0.2
C(6) C(7) C(8) C(9) C(12) O(13) N(14) H(26) H(27) H(28) H(35) H(36)
Mulliken atomic charge (electronic charge)
dipole moment, molecular polarizability, electronic structure, acidity-basicity behavior and many properties of molecular system [59-63]. Mulliken atomic charges calculated by DFT method is collected and shown by the corresponding Mulliken’s plots (Figures 7, 8). It is worth mentioning that C(12), H(26), H(27), H(28), H(35) and H(36) atoms of keto form exhibit positive charge and became more acidic, while C(6), C(7), C(8), C(9), O(13) and N(14) atoms exhibit negative charges. O(13) and N(14) have a maximum negative charges value about -0.5391 and -0.7656 respectively. The maximum positive atomic charge is obtained for C(12) which is carbon atom present in the functional group (C-N) and (C=0). For the enol form C(12), H(26), H(27), H(28), H(35) and H(36) atoms exhibits positive charge, while C(6), C(7), C(8), C(9), O(13) and N(14) atoms exhibit negative charges. O(13) and N(14) have a maximum negative charges value about - 0.5932 and - 0.638 respectively. The maximum positive charge is obtained for C(12) which is carbon atom present in the functional group (C-N) and (C=0).
-0.4 -0.6 -0.8
Atom no.
Figure (8): Mulliken’s charge plot of PACM (enol form)
Conclusions The preparation of polyacrylamide complexes with CoSO4, NiSO4, CuCl2, CrCl3, MnCl2 and FeCl3. The analytical data depict the formation of complexes with stoichiometry, (1:6) (Metal : monomer Ligand) and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggests octahedral geometry for all complexes. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ∆S# values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing 6(C2H5N) and 6(CO). The metal complexes are ended with metal as a final product. Viscosity and Shale instability using liner swell meter instrument. Comparisons of the experimental and theoretical IR spectra were carried out besides some other theoretical calculations.
References 1.
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Graphical Abstract
Highlights • Co2+, Ni2+,Cu2+, Cr3+, Mn2+ and Fe3+
complexes of polyacrylamide were prepared.
• The six polymer complexes were characterized by different measurements.
• Some applications of polyacrylamide were done.