Correction: Tri- and hexa-nuclear Ni II – Mn II complexes of a N 2 O 2 donor unsymmetrical ligand: synthesis, structures, magnetic properties and catalytic oxidase activities

Correction for ‘ Tri- and hexa-nuclear Ni II – Mn II complexes of a N 2 O 2 donor unsymmetrical ligand: syn-thesis, structures, magnetic properties and catalytic oxidase activities ’ by A. Ghosh Dalton Trans.

In response to the overestimation of k cat 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, 13957-13971) 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" which was not mentioned in the text. Therefore, the sentence on page 13964, right column should be changed to "The kinetic studies of catecholase-like activity were performed using methanolic solutions of complexes 3 and 4 under aerobic conditions by the integrated rate method".
(2) To avoid any confusion for readers, the caption of Fig. 7 should be changed to "Increase in the 3,5-DTBQ band at around 400 nm after mixing of equal volumes of methanolic solutions of 3,5-DTBC (1 × 10 −2 M) and complex 3 (5 × 10 −5 M) (left) and a plot of the rate vs. substrate concentration (right). The inset shows the corresponding Lineweaver-Burk plot of 3. The UV-spectra were recorded at 5 min intervals".
(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. Therefore, we have recalculated the Calc. rate/"rate" factors for complexes 3 and 4 with the correct concentration 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 ∼2 for any of these compounds. They are close to ∼1 for lower concentrations of substrate as expected. Table 1 Spectral and kinetic parameters of complexes for different substrate concentrations 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 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 The rate has been calculated using 1630 M −1 cm −1 as the molar absorptivity of the product. c The calculated rate has been determined using the equation: V 0 ¼ VM½S ½SþKM . d For these compounds the absorbance increases slowly at the beginning of the reaction, then rapidly, and then slowly again at the end of the reaction. Hence, for the rate calculation we took ΔAbsorbance for the 5 min time gap at 15-20 min of reaction when the rate appeared to be a maximum. Therefore, we have repeated the experiments for the phenoxazinone synthase-like activity of both complexes 3 and 4 with different concentrations of substrate and catalyst, and the k cat values have been calculated by the "initial rate method" considering the molar extinction coefficient of amino-phenoxazinone (APX) as 18 300 M −1 cm −1 . We obtained nearly linear fits for both compounds with the new data. The plots in Fig. 1A show the increase in the absorbance band at around 425 nm with time due to the formation of amino-phenoxazinone for complexes 3 and 4 with the catalyst concentrations used for determination of the kinetic parameters. The corresponding rate vs. substrate concentration plots and Lineweaver-Burk plots for complexes 3 and 4 are shown in Fig. 1B and C, respectively. The new kinetic parameters are included in Table 2 and are compared with the previously reported data.
(5) The caption of Fig. 8 should be corrected to "Increase in the amino phenoxazinone band at around 425 nm after mixing of equal volumes of methanolic solutions of o-aminophenol (1 × 10 −2 M) and complex 3 (5 × 10 −5 M) (left) and plot of the rate vs. substrate concentration (right). The inset shows the corresponding Lineweaver-Burk plot of 3. The UV-vis spectra were recorded at 5 min intervals".
The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.  ΔAbsorbance for 6 min (0-6 min)