Open Access Article
This Open Access Article is licensed under a Creative Commons Attribution 3.0 Unported Licence
Correction: Mixed azido/phenoxido bridged trinuclear Cu(II) complexes of Mannich bases: Synthesis, structures, magnetic properties and catalytic oxidase activities
Avijit
Das
a,
Kisholoy
Bhattacharya
ab,
Lakshmi Kanta
Das
c,
Sanjib
Giri
ad and
Ashutosh
Ghosh
*a
aDepartment of Chemistry, University College of Science, University of Calcutta, 92, A. P.C. Road, Kolkata 700009, India. E-mail: ghosh_59@yahoo.com
bDepartment of Chemistry, Adamas University, Barasat-Barrackpore Road, Barasat 700126, West Bengal, India
cDepartment of Chemistry, Government General Degree College at Kharagpur-II, Ambigeria, Madpur, Paschim Medinipur, 721149, West Bengal, India
dDepartment of Chemistry, Sri Ramkrishna Sarada Vidyamahapitha, Kamarpukur, West Bengal 712612, India
First published on 26th February 2020
Abstract
Correction for ‘Mixed azido/phenoxido bridged trinuclear Cu(II) complexes of Mannich bases: Synthesis, structures, magnetic properties and catalytic oxidase activities’ by A. Ghosh et al., Dalton Trans., 2018, 47, 9385–9399.
In response to the overestimation of kcat values for the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) and o-aminophenol (OAP) catalysed by the complexes reported in the paper (Dalton Trans., 2018, 47, 9385–9399) that has been pointed out by Laura Gasque et al.,1 we regret that there are some mistakes and these have been corrected below. These corrections do not affect the discussion or conclusions of the original article.
(1) We analyzed the kinetic data for oxidation of 3,5-DTBC to 3,5-DTBQ by the “integrated rate method” not by the “initial rate method”. Therefore, the sentence on page 9392, right column, last paragraph should be changed to “The kinetics of oxidation of 3,5-DTBC to 3,5-DTBQ by 1–3 were determined by the integrated rate method by monitoring the growth of the quinone band at 402 nm as a function of time”.
(2) To avoid any confusion for readers, the caption of Fig. 6 should be changed to “Increase of the 3,5-DTBQ band at around 401 nm after mixing of equal volumes of 3,5-DTBC (1 × 10−2 M) and a methanolic solution of complex 2 (1 × 10−4 M). The spectra were recorded at 5 min intervals for 60 min”.
(3) The calc. rate/“rate” factors calculated by Laura Gasque et al.1 for these complexes are incorrect, as the concentration of the catalyst and the concentration of the substrate are halved after mixing. This factor also depends upon the concentration of substrate. We have recalculated the calc. rate/“rate” factors for complexes 1–3 with the correct concentrations of catalyst and with different concentrations of substrate (Table 1). From these calculations, one can see that the calc. rate/“rate” factors do not exceed ∼5 for any of these compounds. They are close to ∼1 for lower concentrations of substrate as expected.
![[thin space (1/6-em)]](https://www.rsc.org/images/entities/char_2009.gif)
:[cat] = 100:1 and 10:1 for the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) and comparison of the calc. rate with the rate
| Complex | [S] (M)a | [Cat] (M)a | ΔAbsorbance for 5 mind | Rateb (M min−1) | V M (M min−1 ) | k cat (h−1) | K M (M) | Calc. rate (V0)c | V 0/rate |
|---|---|---|---|---|---|---|---|---|---|
a The effective concentrations of complex and substrate after mixing are halved with respect to their initial concentrations because both are mixed with equal volumes.
b Rate has been calculated using 1630 M−1 cm−1 as the molar absorptivity of the product.
c Calculated rate has been determined using the equation:  .
d ΔAbsorbance for time gaps of 5 min has been measured from 90 s to 390 s.
|
|||||||||
| 1 | 5 × 10−3 | 5 × 10−5 | 0.41 | 5.03 × 10−5 | 4.74 × 10−4 | 568.8 | 46.63 × 10−4 | 24.53 × 10−5 | 4.8 |
| 5 × 10−4 | 5 × 10−5 | 0.28 | 3.44 × 10−5 | 4.74 × 10−4 | 568.8 | 46.63 × 10−4 | 4.59 × 10−5 | 1.2 | |
| 2 | 5 × 10−3 | 5 × 10−5 | 0.37 | 4.54 × 10−5 | 4.52 × 10−4 | 542.1 | 47.96 × 10−4 | 23.04 × 10−5 | 5.2 |
| 5 × 10−4 | 5 × 10−5 | 0.25 | 2.57 × 10−5 | 4.52 × 10−4 | 542.1 | 47.96 × 10−4 | 4.26 × 10−5 | 1.3 | |
| 3 | 5 × 10−3 | 5 × 10−5 | 0.33 | 4.05 × 10−5 | 4.17 × 10−4 | 500.4 | 50.43 × 10−4 | 20.76 × 10−5 | 5.1 |
| 5 × 10−4 | 5 × 10−5 | 0.21 | 2.58 × 10−5 | 4.17 × 10−4 | 500.4 | 50.43 × 10−4 | 3.76 × 10−5 | 1.5 | |
(4) The kinetic parameters for the oxidation of o-aminophenol in the original paper were calculated by the “integrated rate method”. We agree that calculation of kcat for oxidation of o-aminophenol by the “integrated rate method” is a mistake considering the high ε value of APX. Moreover, we noticed that after about 2 hours of time the absorbance apparently becomes constant, and we used that incorrectly as Aα, but the constant absorbance is probably due to polymerization or formation of other compounds. Hence, in the original report, the catalytic activities were grossly overestimated and we obtained incongruous kcat values. We have now calculated the kcat values by the “initial rate method” considering the molar extinction coefficient of amino-phenoxazinone (APX) as 18300 M−1 cm−1. The corresponding rate vs. substrate concentration plots and Lineweaver–Burk plots for three complexes are shown in Fig. 1. The new kinetic parameters of complexes 1–3 are included in Table 2 and the results of these measurements are compared with the previously reported data in Table 3.
 | ||
| Fig. 1 Plots of rate vs. substrate concentration for complexes 1–3. Insets show the corresponding Lineweaver–Burk plots. | ||
| Complexes | [Cat] (M) | V max (M s−1) | K M (M) | k cat (h−1) |
|---|---|---|---|---|
| 1 | 5 × 10−5 | 3.45 × 10−8 | 2.32 × 10−3 | 2.5 |
| 2 | 5 × 10−5 | 3.37 × 10−8 | 2.80 × 10−3 | 2.4 |
| 3 | 5 × 10−5 | 3.05 × 10−8 | 2.46 × 10−3 | 2.2 |
| Complex | [S]a (M) | [Cat]a (M) | ΔAbsorbance for 5 min (0–5 min) | Rateb (M min−1) | V M (M min−1) | k cat (h−1) | K M (M) | Calc. rate (V0)c | V 0/rate |
|---|---|---|---|---|---|---|---|---|---|
a The effective concentrations of complex and substrate after mixing are halved with respect to their initial concentrations because both are mixed with equal volumes.
b Rate has been calculated using 18300 M−1 cm−1 as the molar absorptivity of the product.
c Calculated rate has been determined using the equation:  .
|
|||||||||
| Kinetic data calculated by the integrated rate method and reported in the original paper | |||||||||
| 1 | 5 × 10−3 | 5 × 10−5 | 0.110 | 1.20 × 10−6 | 1.05 × 10−4 | 125.8 | 48.92 × 10−4 | 5.33 × 10−5 | 44 |
| 2 | 5 × 10−3 | 5 × 10−5 | 0.105 | 1.09 × 10−6 | 9.91 × 10−5 | 118.9 | 44.00 × 10−4 | 5.27 × 10−5 | 48 |
| 3 | 5 × 10−3 | 5 × 10−5 | 0.095 | 1.04 × 10−6 | 9.56 × 10−5 | 114.7 | 38.12 × 10−4 | 5.24 × 10−5 | 50 |
| Kinetic data obtained by the initial rate method | |||||||||
| 1 | 5 × 10−3 | 5 × 10−5 | 0.110 | 1.20 × 10−6 | 2.07 × 10−6 | 2.5 | 2.32 × 10−3 | 1.41 × 10−6 | 1.20 |
| 2 | 5 × 10−3 | 5 × 10−5 | 0.105 | 1.09 × 10−6 | 2.02 × 10−6 | 2.4 | 2.80 × 10−3 | 1.29 × 10−6 | 1.18 |
| 3 | 5 × 10−3 | 5 × 10−5 | 0.095 | 1.04 × 10−6 | 1.83 × 10−6 | 2.2 | 2.46 × 10−3 | 1.23 × 10−6 | 1.18 |
(5) The caption of Fig. 9 should be corrected to “Increase of the APX band at around 430 nm after mixing of equal volumes of methanolic solutions of OAP (1 × 10−2 M) and complex 2 (1 × 10−4 M). The spectra were recorded at 5 min intervals for 75 min”.
The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
References
- L. Gasque, A. Mendieta and G. Ferrer-Sueta, Comment on “Mixed azido/phenoxido bridged trinuclear Cu(II) complexes of Mannich bases: Synthesis, structures, magnetic properties and catalytic oxidase activities”, Dalton Trans., 2018, 47, 9385–9399 and “Tri- and hexa-nuclear NiII–MnII complexes of a N2O2 donor unsymmetrical ligand: synthesis, structures, magnetic properties and catalytic oxidase activities”, Dalton Trans., 2018, 47, 13957–13971, Dalton Trans., 2020 10.1039/C9DT01498E.
| This journal is © The Royal Society of Chemistry 2020 |