Presentation on theme: "Oxygen Affinity of the Transition Metal Complexes Of Schiff Base Ligands متراكبات العناصر الإنتقالية لليجاندات قواعد شيف الحاملة للأكسجين الحاملة للأكسجين."— Presentation transcript:
Oxygen Affinity of the Transition Metal Complexes Of Schiff Base Ligands متراكبات العناصر الإنتقالية لليجاندات قواعد شيف الحاملة للأكسجين الحاملة للأكسجين Adel A.A. Emara Associate Prof. in Inorganic Chemistry University Collage in Mekkah Umm Al-Qura University
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1- Historical Background. 2- Natural Biological Oxygen Carrier Metal complexes. 3- Criteria for the Schiff base complexes to carry oxygen. 4- (a) Schiff base ligands, (b) metal complexes of the Schiff base ligands. 5- Characterization of the ligands and their metal complexes. 6- Study of the absorption and desorption of the metal complexes in strong and weak polar solvents. 7- Conclusions. Outlines
1- Historical Background In 1852: Fremy reported that the exposure of ammoniacal solutions of Co(II) salt to the atmosphere resulted in the formation of brown salts which he called oxo-cobalates. In 1898: Werner characterized the compounds as containing the diamagnetic cation [(H 3 N) 5 Co(O 2 )Co(NH 3 ) 5 ] 4+. In 1938: Tsumaki made the first report of a synthetic reversible cobalt-oxygen carrier. World War II: U.S. Navy used these complexes in the production of pure dioxygen in a destroyer tender for use in welding and cutting. Also, they used the complexes in the aircraft crew. In 1978: Floriani studied the behavior of derivatives of [Co(II)salen] in non aqueous media and found, in general, the ratio uptake of O 2 : Co(II) is 1 : 2. In 1985: When pyridine solutions of [Co(3-methoxy-salen)] were exposed to O 2 at 10°C, an O 2 uptake : Co(II) is 1 : 1 was observed. Heating the dioxygen adduct in vacuo regenerated the starting material.
2-Natural Biological Oxygen Carrier Metal complexes LocationSourceMetalProtein Corpuscles Mammals Birds Fish Insects Fe (heme) Hemoglobin (Hb) Muscle Mammals Other vertebrates Some invertebrates Fe (heme) Myoglobin (Mb) Plasma Snails Lugworm Earthworm Fe (heme) Erythrocruorin (Ery) PlasmaMarine wormsFe (heme) Chlorocruorin (Chl) CorpusclesMarine wormsFe (non-heme) Hemerythrin (Her) Plasma Mollusks Arthropodes Cu Hemocyanin (Hcy) CorpusclesAscidiansV Hemovanadin (Hv)
R = -CH=CH 2 : Protoporphyrin IX R = CHO : Chlorocruoroporphyrin Figure 1. Structures of natural and synthetic porphyrins. The numbers: methyl; vinyl; Propionic acid; ethyl or Phenyl substituents. α, β, γ and δ position have the same substituent.
3- Criteria for the Schiff base complexes to carry oxygen: i) The Schiff base complexes of the Co(II), Ni(II) and Mn(II) metal ions form: (a) square planar arrangement with tetradentate Schiff base ligands, or (b) square pyramid arrangement with pentadentate Schiff base ligands. ii) The complexes should be soluble in suitable non-aqueous solvent.
(a) Schiff Base Ligands The condensation reaction between aldehydes or ketenes with primary amines. 4- Synthesis of Schiff base ligands and their transition metal complexes
Aldehydes and ketones Amines
Figure 2. Representative structures of Schiff base ligands Ligand R 1 R 2 (D) H 2 Saldet H o-OHC 6 H 4 - (E) H 2 o-Hacdet CH 3 o-OHC 6 H 4 - (F) H 2 Acacdet CH 3 -CH=C(OH)CH 3 Tetradentate Ligands Pentadentate Ligands
B) Metal Complexes of the Schiff Base Ligands Abs. Ethanol M(II) salt + Schiff base ligands [ML] Complex Square planar or M(II) = Co(II), Ni(II) and Mn(II) Square pyramid
Adel A.A. Emara, A.M. Ali, E.M. Ragab and A.A. El-Asmy; J. Coord. Chem., 61, (2008).
Adel A.A. Emara, A.M. Ali, A.A. El-Asmy and E.M. Ragab; Brazilian Chemical Society, in press.
Figure 3. Glove bag flushed with dry nitrogen gas used for handling the starting materials and equipments.
Figure 4. Purification of N 2 gas. (A) Pyrogallol in ethanol, (B) Sodium hydroxide pellets, (C) Silica gell, (D) solid calcium chloride and (E) to the glove bag.
Figure 5. Reaction vessels used in synthesis of square planar and square pyramide Schiff base metal(II) complexes.
5- Characterization of the Schiff base ligands and their Co(II), Ni(II) and Mn(II) complexes The used techniques are: Elemental (C, H and N) analyses. Elemental (C, H and N) analyses. Metal ions analyses using EDTA. Metal ions analyses using EDTA. 1 H-NMR spectra of the ligands. 1 H-NMR spectra of the ligands. Melting points. Melting points. Mass spectra. Mass spectra. Infrared spectra. Infrared spectra. Electronic spectra. Electronic spectra. Magnetic measurements. Magnetic measurements. Molar conductivity measurements. Molar conductivity measurements. Thermal gravimetric analysis (TGA). Thermal gravimetric analysis (TGA).
Table 1. Physical and analytical data of the synthesized ligands and Schiff base complexes under nitrogen atmosphere. Elemental analysis % Found/(Calcd)m.p., ( C) Yield, (%) ColorM.F.Formula Ligands and Complexes MNHC (12.38) 7.37 (7.42) (70.77) 10592Golden yellow C 20 H 25 N 3 O 2 [H 2 o-Hacdet] 85Reddish brown C 18 H 21 N 3 O 2 [H 2 Saldet] * (10.19) (12.16) 5.68 (5.42) (41.69) 23587Pale orange C 20 H 31 N 5 O 11 Ni[Ni(H 2 o-Hacdet) (NO 3 ) 2 ] (13.34) 9.63 (9.55) 5.97 (6.13) (49.12) 25077Orange440.12C 18 H 27 N 3 O 6 Ni[Ni(Saldet)] (13.39) 9.38 (9.54) 6.03 (6.13) (49.10) 29083Pale brown C 18 H 27 N 3 O 6 Co[Co(Saldet)] (12.11) 7.56 (12.36) 5.05 (4.96) (48.80) >30076Dark green C 18 H 22 N 4 O 6 Mn[Mn(HSaldet)(NO 3 ) 2 ] (11.64) 9.52 (9.06) 6.39 (6.68) (51.72) >30074Dark green C 20 H 31 N 3 O 6 Mn[Mn(o-Hacdet)] *. Oily product and the elemental analysis was not performed.
Table 2. Characteristic vibrational bands (cm -1 ) of the Schiff base, ligands and their Co(II), Mn(II) and Ni(II) pentadentate complexes under nitrogen atmosphere. ν(M-O)ν(M-N)ν(C-N)ν(C-O)ν(-C=N-)ν(CH 3 )ν(=C-H) Ligands and complexes 1338 m1278 vs1632 vs2846 s, br3056 m, br[H 2 Saldet] 1326 m1242 m1614 vs2914 w, br3058 w, br[H 2 o-Hacdet] 323 w475 w1384 vs1202 w1628 m [Co(Saldet)] 306 vw564 w1398 m1204 m1624 vs2924 m, br3040 m, br[Mn(HSaldet)(NO 3 )] 375 m446 vs1326 vs1236 vs1643 s2926 m, br3063 m, br[Mn(o-Hacdet)] 345 w454 vw1384 vs1240 m1610 m2866 m, br3040 w, br[Ni(H 2 o-Hacdet)(NO 3 ) 2 (H 2 O)] 305 vw433 w1384 vs1199 m1624 vs2938 m, br3052 m, br[Ni(Saldet)]
Table 3. Electronic spectral bands magnetic moments and molar conductivity of the prepared Schiff base metal complexes. Molar conductivity (c) Magnetic moment (B.M.) (b) Electronic Transitions (nm) d-d transitions (a) Complex (0.064) a [Ni(H 2 o-Hacdet)(NO 3 ) 2 ].2H 2 O (e) (0.015) a [Ni(Saldet)] (e) (0.04), 412 (0.26), 700 (0.36) [Co(Saldet)].4H 2 O (e) (0.06)[Mn(HSaldet)(NO 3 )] (d) (0.05)[Mn(o-Hacdet)] (e) (a) The type of transition was not assigned. (b) No values were obtained. (c) Values were measured in DMF solution. (d) Complexes prepare in air atmosphere. (e) Complexes prepared under dry nitrogen atmosphere.
t 2g egeg high spin tetrahedral high spin octahedral low spin octahedral low spin square pyramid low spin square planar t 2g egeg d x2-y2 d z2 d xy d xz d yz d x2-y2 d z2 d xy d xz d yz Figure 6. Energy level diagram of cobalt(II)(d 7 ) ion in high-spin tetrahedral, octahedral (high and low-spin), square pyramid (low spin) and low-spin square planar.
TGA analysis Figure 7. TGA and DrTGA of the [Mn (o-Hacdet) ].
Structure 3. Square planar Schiff base complexes; M = Co(II), Ni(II) or Mn(II).
Structure 4. Square pyramide of the [Co(saldet)] Structure 5. Square pyramid structure of the nitrato complexes [M = Ni(II) or Mn(II)].
n[ML] + O 2 [ML] n (O 2 ) where n = 1 or 2 In (a) suitable solvent and (b) controlled temperature. 6- The Oxygen Sorption Process of the Metal Complexes of the Schiff Base Ligands
Table 4. Solubility of Co(II), Ni(II) and Mn(II) pentadentate Schiff Base complexes in DMF and chloroform solvents at 25 °C. Solubility (M)Complex ChloroformDMF [Ni(Saldet)] [Co(Saldet)] [Mn(o-Hacdet)] It is important to know the maximum solubility of each complex, which is an important parameter. This solubility parameter could give us the highest capacity of each Schiff base complex solution to carry oxygen. Solubility in DMF and chloroform
Figure 8. Measurement system for the absorption and desorption of the Schiff base complexes with oxygen. (A) nickel-monel vacuum line, (B) gauge for measuring the absorption and desorption of oxygen, (C) the reactor, (D) solvent trap, (E) valve, (F) thermometer ( – 40 to 40 °C), (G) thermometer (0 to 120 °C), (H) water and (I) dissolved oxygen meter.
Table 5. Oxygen absorption capacity of cobalt(II) Schiff base oxygen carrier in 100 mL DMF from -5 ºC (absorption) to 100 ºC (desorption). Average carrier loading (%) Carrier loading (%) Oxygen capacity (x10 -4 g) Oxygen conc. (x M) Cycle number Axial base Conc. (×10 -2 M) Carrier conc. (×10 -2 M) Carrier None11.00 [Co(o-Hacen)] Pyridine [Co(o-Hacen)] None13.00 [Co(Acacen)] Pyridine [Co(Acacen)] None12.00 [Co(Salen)] Pyridine [Co(Salen)]
Table 6. Oxygen absorption capacity of cobalt(II), nickel(II) and manganese(II) pentadentate Schiff base oxygen carrier in 100 mL DMF and chloroform solvents from -5 ºC (absorption) to 100 ºC (desorption). Average carrier loading (%) Carrier loading (%) Oxygen capacity (x g) Oxygen conc. (x M) Cycle number SolventCarrier conc. (×10 -2 M) Carrier DMF15.00 [Co(Saldet)] Chloroform10.0 [Co(Saldet)] DMF11.0 [Ni(Saldet)] Chloroform10.0 [Ni(Saldet)] DMF9.00 [Mn(o-Hacdet)] Chloroform8.00 [Mn(o-Hacdet)]
Carrier loading % Carrier loading % [(Carrier complex)] + O 2 carried [(Carrier complex)O 2 ] Mole of O 2 carried Carrier loading % = x 100 Mole of [(Carrier complex)O 2 ] oxygen concentration: is considered the amount of oxygen measured by the dissolved oxygen (D.O.) meter, which indicate the molar ratio of the complex carrier to the oxygen carried in the complex. The oxygen capacity: is the weight of oxygen molecules carried by the carrier complex.
Average carrier loading (%) Carrier loading (%) Oxygen capacity (x10 -4 g) Oxygen conc. (x M) Cycle number Carrier conc. (×10 -2 M) Carrier [Co(Saldet)] [Co(Saldet)] [Co(Saldet)] [Co(Saldet)] Table 7. Oxygen absorption capacity of cobalt Schiff-Base complex, [Co(Saldet)], oxygen carrier in 100 mL DMF from -5 ºC (absorption) to 100 ºC (desorption) in different concentrations.
After the study of the absorption and desorption of the Co(II), Ni(II) and Mn(II) tetradentate and pentadentate Schiff base complexes. It is clear that: 1.Co(II) Schiff base complexes behave as good oxygen carriers than Ni(II) and Mn(II) Schiff base complexes. 2.Co(II) pentadentate Schiff base complexes is more effective as oxygen carriers than the Co(II) tetradentate Schiff base complexes. 3.This kind of materials can be used as catalysts in oxidative addition reactions in the organic chemistry and petrochemicals, which is reproducible and not polluted like other oxidants which is considered that this materials as friendly to the environmental.