Complex formation between nickel(II) and 2-(2-aminoethyl) benzimidazole: A kinetic and equilibrium study |
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Authors: | Anadi C Dash Achyuta N Acharya Ramakanta Sahoo |
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Institution: | (1) Department of Chemistry, Utkal University, 751 004 Bhubaneswar, India;(2) Department of Chemistry, Institute of Textile Technology, 754 025 Choudwar, India;(3) Department of Chemistry, Panchayat College, 768 028 Baragarh, India |
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Abstract: | Summary The reversible complex formation between 2-(2-aminoethyl) benzimidazole (AEB) and nickel(II) was studied by stopped flow spectrophotometry at I = 0.30 mol dm–3. Both the neutral and monoprotonated form of AEB reacted to give the NiAEB2+ chelate. At 25 °C, the rates and activation parameters for the reactions NiII + AEB
NiAEB2+ and NiII + AEBH+
NiAEB2+ + H+ are k
f
L(dm–3 mol–1 s–1) = (2.17 ± 0.24) × 103, H
(kJ mol–1) = 40.0 ± 0.8, S
(JK–1 mol–1) = – 47 ± 3 and k
inff
pHL
(dm3 mol–1 s–1) = 33 ± 10, H
(kJ mol–1) = 42.0 ±2.7, S
(JK–1 mol–1) = – 72 ± 9. The dissociation of NiAEB2+ was acid catalysed and k
obs for this process increased linearly with H+] in the 0.01–0.15 mol dm–3 (10–30 °C) range with k
H(dm3 mol–1s–1) (25 °C) = 329 ± 6, H
(kJ mol–1) = 40 ± 2 and S
(JK–1 mol–1) = – 61 ± 8. The results also indicated that the formation of NiAEB2+ involves a chelation-controlled, rate-limiting process. Analysis of the S ° data for the acid ionisation of AEBH
inf2
p2+
and the formation of NiAEB2+ showed that the bulky AEBH+ ion has a solvent structure breaking effect as compared to AEB s
aqS ° (AEBH+) – s
aq ° (AEB) = 69 JK–1 mol–1], while AEBH
inf2
p2+
is a solvent ordering ion relative to NiAEB2+ s
aq° (NiAEB2+) – ovS
aq ° (AEBH
inf2
p2+
) = 11 JK–1 mol–1].Author to whom all correspondence should be directed. |
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Keywords: | |
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