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首页> 外文期刊>New Journal of Chemistry >Density functional theory calculations of catalytic mechanistic pathways for the formation of O2 involving triazolylidene iridium complexes
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Density functional theory calculations of catalytic mechanistic pathways for the formation of O2 involving triazolylidene iridium complexes

机译：涉及三唑基铱铱配合物的O2形成的催化机理的密度泛函理论计算

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We have studied lr(III)-catalysed water oxidation pathways at the CAM-B3LYP level of Density Functional Theory (DFT), involving a novel oxygen-evolving catalyst (OEC), for a low-concentration mechanism. Starting from the dichloride complex lr~(III)-Cl (lr = [lrCp*Cl(triazolylidene)], Cp~* = C5Me5~-), DFT predicts reaction with one water molecule and formation of a cationic solvento complex [lr~(III)-OH2]~+, followed by two proton-coupled electron transfer (PCET) steps; one involves an [lr~(III)-OH2]~+/[lr~(IV)-OH]~+ transition, whilst the other is an [lr~(III)-OH]+ to [lr~V=O]~+ transformation. The oxidation potentials and pKa values were calculated for the transformation of [lr~(III)-OH2]~+ to [lr~V=O]~+ for both sequential orders of H~+/e~- and e~-/H~+ transfer. Deproto-nation of [lr~(III)-OH2]~+ was found to be feasible even in acidic conditions (with a pK_a of 1.08), while the deprotonation of [lr~(IV)-OH]~+ is strongly disfavoured (pK_a = 10.33). The computed oxidation potentials are rather high (1.81 V and 2.01 V for [lr~(III)-OH2]+ and [lr~(VI)-OH]~+, respectively); however, subsequent proton dissociation is more favoured (with pK_ values for the oxidised intermediates of -16.1 and -8.1, respectively). This indicates the possibility of concerted, as opposed to stepwise, H~+/e~ transfer (PCET). Further, the [lr~V=O]~+ intermediate was found to react with two water molecules to release O2. This sequence involves O-O bond formation followed by one PCET step, while a further single electron transfer (oxidation) step generates an [lr~V-O-O]~+ species, which liberates O2 and regenerates the [lr~(III)-OH2]~+ complex.
机译：我们已经在密度泛函理论（DFT）的CAM-B3LYP水平上研究了lr（III）催化的水氧化途径，涉及一种新型的析氧催化剂（OEC），以实现低浓度的机理。 DFT从二氯化物络合物lr〜（III）-Cl（lr = [lrCp * Cl（三唑基）]，Cp〜* = C5Me5〜-）开始，预测与一个水分子的反应并形成阳离子溶剂络合物[lr〜 （III）-OH2] +，然后进行两个质子偶联电子转移（PCET）步骤;一个涉及[lr〜（III）-OH2]〜+ / [lr〜（IV）-OH]〜+的跃迁，另一个涉及从[lr〜（III）-OH] +到[lr〜V = O ]〜+转换。计算了H〜+ / e〜-和e〜-/的两个顺序从[lr〜（III）-OH2]〜+到[lr〜V = O]〜+的氧化电势和pKa值。 H〜+转移。发现即使在酸性条件下（pK_a为1.08），[lr〜（III）-OH2]〜+的去质子化也是可行的，而[lr〜（IV）-OH]〜+的去质子化是非常不利的。 （pK_a = 10.33）。计算出的氧化电位相当高（[lr〜（III）-OH2] +和[lr〜（VI）-OH]〜+分别为1.81 V和2.01 V）;然而，随后的质子解离更受青睐（氧化中间体的pK_值分别为-16.1和-8.1）。这表明有可能协调进行H〜+ / e〜传输（PCET），而不是逐步进行。此外，发现[lr〜V = O]〜+中间体与两个水分子反应释放出O2。该序列涉及OO键形成，随后是一个PCET步骤，而另一单电子转移（氧化）步骤产生了[lr〜VOO]〜+物种，该物种释放出O2并再生了[lr〜（III）-OH2]〜+复杂。

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