Preprint of "Hydrogen Atom Abstraction via Hydride-Coupled Electron Transfer and Its Origin"

S1 Supplementary Information Unveiling the shift from proton-coupled to hydride-coupled electron transfer and its origin Zuzanna Wojdyla,a Jishnu Sai Gopinatha and Martin Srneca,* aJ. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech Republic Corresponding Author *E-mail: m[email protected]s.cz S2 Table of Contents Computational Details ................................................................................................................................................................ S3 Thermodynamic and reactivity data for the substrates and Cu(III)-OH/ Cu(II)-OH complexes ................................................ S5 Oxidants and substrates used in the study ................................................................................................................................... S14 Performance of the three-component model applied to Cu(III)-OH/ Cu(II)-OH reactions ........................................................ S15 Analysis the reactions based on electronic-structure descriptors ............................................................................................... S17 Intrinsic bond orbital analysis for the reactions .......................................................................................................................... S19 S3 Computational Details The calculations were performed using the Gaussian 16 revision C.01 program[40] for the (L)CuIII−OH complex (L = N,N′-bis(2,6diisopropylphenyl)-2,6-pyridinedicarboxamide) as reported by Tolman[29] and for the one electron reduced variant of this complex. The B3LYP functional[41] with Grimme's D3 dispersion correction[42] and the def2-SVP basis set[43] was used. The solvation effects were described with the conductor-like polarizable continuum model (CPCM)[44] using 𝜀 = 7.4 (tetrahydrofuran). The Gibbs free energies for the optimized structures were calculated as the sum of potential electronic energies (Eel) calculated at the B3LYP-D3/def2-SVP level with CPCM and the thermal enthalpic and entropic contributions to the Gibbs free energy (at 298.15 K) obtained from frequency analysis performed at the same level of theory: 𝐺 = 𝐸𝑒𝑙 +[𝐸𝑍𝑃𝐸 +𝑝𝑉 +𝑅𝑇 ln 𝑄] , where Eel and Q are the zeropoint vibrational energy and the molecular partition function, respectively. To calculate species respective for the half-reaction thermodynamic cycles and the barriers for the reaction the ground states of the reactants the electronic ground states were used: singlet for CuIII−OH and doublet for CuII−OH. The Gibbs free energy barriers for the reactions were calculated as the difference between the Gibbs free energy of the transition state (TS) and the isolated reactants. A value of 1.9n kcal mol−1 has been applied to correct the computed values to the 1 mol L−1 standard state (a value of 1.9 kcal mol−1 corresponds to the conversion of a 1 bar standard state in the gas phase to 1 mol L−1 concentration in solution at 298 K; n is the change in the number of moles). To obtain the TS structures for the self-exchange reactions between the CuII–OH or CuIII–OH complex and its hydrogenated form (CuI–OH2 or CuII–OH2) the bulky 2,6-diisopropylphenyl groups were replaced by methyl groups. The TS structures S4 were approximated by constrained geometries that imposed symmetry between the two Cu complexes. Specifically, corresponding Cu– X distances (where X refers to the ligating N atoms or the O atom of the OH/OH₂ group) were constrained to be equal across the pair, without fixing their absolute values. Similarly, the distances between the transferring hydrogen atom and the donor and acceptor oxygen atoms were constrained to be equal, to obtain a symmetric hydrogen-sharing configuration. The atoms-in-molecules (AIM) approach implemented in the AIMAll program[25] was employed to assess the redistribution of electron density during the reaction in the investigated systems. The atomic charges were computed based on the electron densities calculated at the B3LYP-D3/def2-SVP level for the optimized structures of the transition states and reactant complexes. Densities were integrated using the Proaim method with a ‘very fine’ interatomic surface mesh and a basin outer angular quadrature of 14 400 grid points (using 15-point Gaussian quadrature GS15). The AIM properties of the atoms with a Lagrangian L(A) > 0.001 a.u. were recalculated with the Promega algorithm. The AIM charges and volumes (calculated for the isodensity surface of 0.002 a.u.) of the defined group of atoms, that is the transferred hydrogen atom, the H-atom donor and the acceptor – CuIII–OH or CuII–OH complex, were used to characterize the reaction. Intrinsic reaction coordinate (IRC) structures were derived from the corresponding TSs employing the same computational level as used for geometry optimization. To investigate the electron flow, we utilized IboView (iboexp=2)[26,27] to generate and analyze intrinsic bond orbitals based on the wavefunctions obtained from the IRC points. S5 Table S1. Gibbs free energies of investigated species obtained at the B3LYP-D3def2-SVP level of theory. The values are given in Ha. G(subH) G(catrad) G(anion) G(anionrad) G(cation) G(rad) cyclohexane -235.5870800 -235.3097579 -234.9897959 -235.5590716 -234.760616 -234.946117 cyclohexene -234.3882162 -234.1454694 -233.8301481 -234.3908542 -233.5763406 -233.7625748 DHA -540.2306420 -539.9973934 -539.712297 -540.2628994 -539.4399158 -539.614711 fluorene -500.9662308 -500.7425842 -500.4633711 -501.0156151 -500.1438169 -500.3425738 Ph2CH2 -502.1414053 -501.9012635 -501.6186285 -502.1728803 -501.3320865 -501.5153143 THF -232.2104178 -231.9502539 -231.62241 -232.177506 -231.4114686 -231.5665919 toluene -271.3042935 -271.0554534 -270.7553262 -271.3232365 -270.4655593 -270.6637219 2,7-di(NMe2) -fluorene -768.6103731 -768.4387445 -768.0929585 -768.6392553 -767.7973427 -767.9841398 oxetane -192.9099395 -192.6565777 -192.3316157 -192.8834777 -192.1085083 -192.264387 1,3-CHD -233.1824648 -232.9655494 -232.6477766 -233.2228734 -232.3938172 -232.571178 CHD -233.1691663 -232.9438527 -232.643756 -233.1813552 -232.3889642 -232.5578969 G(Cu(II)-OH2) G(Cu(III)-OH2) G(Cu(II)-OH) G(Cu(I)-OH2) G(Cu(IV)-OH) G(Cu(III)-OH) CuIII-OH -3233.659033 -3233.446508 -3233.186894 -3233.774325 -3232.795173 -3233.020498 G(Cu(I)-OH2) G(Cu(II)-OH2) G(Cu(I)-OH) G(Cu(0)-OH2) G(Cu(III)-OH) G(Cu(II)-OH) CuII-OH -3233.774325 -3233.659033 -3233.261305 -3233.825662 -3233.020498 -3233.186894 S6 Table S2. Thermodynamic data for the investigated substrates and H-atom acceptors. The values were obtained at the B3LYP(D3)/def2-SVP level, with implicit CPCM solvation in THF at 298 K. All energies are given in kcal mol-1. substrates ΔG0 (half-reaction) 𝜔𝐻+ 𝜇𝐻+ 𝜔𝐻− 𝜇𝐻− cyclohexane -402.21 141.97 -180.73 -354.29 379.14 cyclohexene -392.60 139.91 -199.88 -361.41 359.07 DHA -386.50 126.50 -213.10 -365.17 336.55 fluorene -391.35 123.89 -231.09 -386.83 343.01 Ph2CH2 -392.88 125.41 -217.09 -373.07 345.14 THF -404.01 145.47 -195.00 -339.90 369.11 toluene -401.97 133.17 -214.46 -380.57 363.75 2,7-di(NMe2)fluorene -392.97 153.43 -250.00 -373.57 347.95 oxetane -405.09 144.19 -203.85 -343.87 367.35 1,3-CHD -383.59 141.00 -208.98 -367.87 332.01 CHD -383.58 133.16 -209.35 -351.60 340.78 H-atom acceptors CuIII-OH -400.69 115.19 -262.86 -434.47 332.15 CuII-OH -368.62 176.48 -242.51 -357.26 311.71 S7 Table S3. Reactivity data for the Cu(III)-OH/substrate set (singlet). The values were obtained at the B3LYP(D3)/def2-SVP level, with implicit CPCM solvation in THF at 298 K. All energies are given in kcal mol-1. substrates ΔG0 ΔG≠ 𝜂𝐻+ 𝜎𝐻+ ∆𝐺𝑜𝑓𝑓𝑑𝑖𝑎𝑔 𝐻+ ∆𝐺𝑡ℎ𝑒𝑟𝑚𝑜 𝐻+ 𝜂𝐻− 𝜎𝐻− ∆𝐺𝑜𝑓𝑓𝑑𝑖𝑎𝑔 𝐻− ∆𝐺𝑡ℎ𝑒𝑟𝑚𝑜 𝐻− cyclohexane 1.52 15.30 -26.78 -82.13 13.84 14.60 80.18 46.99 -8.30 -7.54 cyclohexene -8.09 9.72 -24.72 -62.98 9.57 5.52 73.05 26.92 -11.53 -15.58 DHA -14.18 2.64 -11.31 -49.76 9.61 2.52 69.29 4.39 -16.23 -23.32 fluorene -9.34 7.15 -8.70 -31.77 5.77 1.10 47.63 10.85 -9.20 -13.86 Ph2CH2 -7.81 8.08 -10.21 -45.77 8.89 4.98 61.39 12.99 -12.10 -16.01 THF 3.32 12.31 -30.27 -67.86 9.40 11.06 94.56 36.96 -14.40 -12.74 toluene 1.28 16.24 -17.98 -48.40 7.60 8.24 53.90 31.60 -5.57 -4.94 S8 Table S4. Reactivity data for the Cu(II)-OH/substrate set (doublet). The values were obtained at the B3LYP(D3)/def2-SVP level, with implicit CPCM solvation in THF at 298 K. All energies are given in kcal mol -1. substrates ΔG0 ΔG≠ 𝜂𝐻+ 𝜎𝐻+ ∆𝐺𝑜𝑓𝑓𝑑𝑖𝑎𝑔 𝐻+ ∆𝐺𝑡ℎ𝑒𝑟𝑚𝑜 𝐻+ 𝜂𝐻− 𝜎𝐻− ∆𝐺𝑜𝑓𝑓𝑑𝑖𝑎𝑔 𝐻− ∆𝐺𝑡ℎ𝑒𝑟𝑚𝑜 𝐻− cyclohexane 33.59 36.69 34.51 -61.78 6.82 23.61 2.98 67.44 16.12 32.91 cyclohexene 23.98 25.45 36.57 -42.63 1.52 13.51 -4.15 47.37 10.80 22.80 DHA 17.88 10.62* 49.98 -29.41 -5.14 3.80 -7.91 24.84 4.23 13.17 fluorene 22.73 7.42 52.59 -11.42 -10.29 1.07 -29.57 31.30 0.43 11.80 Ph2CH2 24.26 51.07 -25.42 -6.41 5.72 -15.81 33.44 4.41 16.53 THF 35.39 34.88 31.01 -47.51 4.12 21.82 17.36 57.40 10.01 27.71 toluene 33.35 43.31 -28.05 -3.81 12.86 -23.30 52.05 7.19 23.86 2,7-di(NMe2)fluorene 24.35 9.95 23.05 7.49 -3.89 8.28 -16.31 36.23 4.98 17.16 oxetane 36.47 33.37 32.29 -38.66 1.59 19.83 13.40 55.64 10.56 28.80 1,3-CHD 14.97 18.63 35.48 -33.54 -0.49 7.00 -10.60 20.30 2.42 9.91 CHD 14.96 10.54 43.32 -33.16 -2.54 4.94 5.67 29.07 5.85 13.33 *an estimate based on unfinished TS optimisation S9 Table S5. Charges and volumes (at isodensity surface 0.002) of the H atom, H atom donor (substrate) and H atom acceptor for stationary points obtained for Cu(III)-OH reactions TS q V substrates H substrate H-atom acceptor H substrate H-atom acceptor cyclohexane 0.295 0.062 -0.360 19.4 761.0 3879.6 cyclohexene 0.288 0.075 -0.366 20.6 713.8 3890.3 DHA 0.303 -0.018 -0.326 20.0 1354.3 3894.8 fluorene 0.363 -0.086 -0.279 18.0 1236.1 3895.6 Ph2CH2 0.322 0.010 -0.335 19.0 1307.1 3888.7 THF 0.279 0.110 -0.392 20.5 561.2 3890.1 toluene 0.343 0.024 -0.369 18.9 753.4 3891.5 RC H substrate H-atom acceptor H substrate H-atom acceptor cyclohexane -0.037 0.018 0.018 42.4 759.9 3887.1 cyclohexene 0.008 -0.020 0.010 38.8 717.0 3881.3 DHA 0.047 -0.056 0.008 35.2 1355.6 3889.7 fluorene 0.033 -0.016 -0.018 39.1 1231.4 3898.6 Ph2CH2 0.037 -0.047 0.006 36.3 1318.3 3886.7 THF 0.039 -0.052 0.012 36.7 563.5 3867.7 toluene 0.014 -0.006 -0.009 40.4 756.0 3891.8 S16 Figure S2. Three-component thermodynamics model applied to the Cu(III)−OH-based set of reactions, ∆G≠ vs: linear free energy relationship LFER (left); LFER with the effect of asynchronicity (middle); LFER together with the complete off-diagonal term (right) using the descriptors derived based on the [𝐻→ +𝑒→ − ⁄ ] cycle (top, mismatched model featuring high off-diagonal contributions) and [𝐻→ −𝑒← − ⁄ ] cycle (bottom, model featuring lower off-diagonal contributions). The quality of correlations is assessed by the squared Pearson’s coefficient (R2). S17 Figure S3. Three-component thermodynamics model applied to the Cu(II)−OH-based set of reactions, ∆G≠ vs: linear free energy relationship LFER (left); LFER with the effect of asynchronicity (middle); LFER together with the complete off-diagonal term (right) using the descriptors derived based on the [𝐻→ +𝑒→ − ⁄ ] cycle (top, model featuring lower off-diagonal contributions) and [𝐻→ −𝑒← − ⁄ ]cycle (bottom, mismatched model featuring high off-diagonal contributions). The quality of correlations is assessed by the squared Pearson’s coefficient (R2). S18 Figure S4. Volume and charge of the transferred H moiety at the TS relative to the volume and charge at RC. The points are colored and shaded from dark blue (favored [𝐻→ −𝑒← − ⁄ ]) to dark red (favored [𝐻→ +𝑒→ − ⁄ ]) to reflect the difference in off-diagonal thermodynamic contributions to the barrier, which originates from the two different [𝐻→ −𝑒← − ⁄ ] and [𝐻→ +𝑒→ − ⁄ ]cycles presented in Figure 1 in the main text. S19 Figure S5. Correlations between η obtained from the nonoperative (left) and the operative thermodynamic cycle (right) and the change of charge on the transferred H atom at the TS calculated with respect to: the average of self-exchange reactions (top) or the RC (bottom). The points are colored to reflect the preference towards one of the thermodynamic cycles (as measured by the ∆𝐺𝑜𝑓𝑓𝑑𝑖𝑎𝑔 ≠ originating from the [𝐻→ −𝑒← − ⁄ ] and [𝐻→ +𝑒→ − ⁄ ] cycles) - in blue (favored [𝐻→ −𝑒← − ⁄ ], Cu(III)−OH-set) and red (favored [𝐻→ +𝑒→ − ⁄ ], Cu(II)−OH-set). S20 (a) (b) Figure S6. The IBO changes of the C−H bond along the IRC for (a) Cu(III)−OH with cyclohexane and (b) Cu(II)−OH with cyclohexane. S21 (a) S22 (b) S23 (c) S24 (d) Figure S7. The intrinsic reaction coordinates and the important IBOs of Cu(III)−OH-based set of reactions. (a) Cyclohexane (b) Cyclohexene (c) DHA and (d) Toluene. For Toluene and DHA the reciprocal transfer occur before TS. S25 (a)