Table 2. Summary of EPR Parameters for the Hydrogen Bond to NH2Y731●a.
| NH2Y731• | Ax [MHz] | Ay [MHz] | Az [MHz] | α [°] | β [°] | γ [°] | Qx [MHz] | Qy [MHz] | Qz [MHz] |
|---|---|---|---|---|---|---|---|---|---|
| Simulation | |||||||||
| Y730-OD | 1.3 | –1.43 | –1.63 | –160 | 110 | 80 | |||
| 120 | 40 | 85 | –0.03 | –0.09 | 0.12 | ||||
| ND2 D(1) | –0.6 | –2.9 | –3.8 | –86 | 98 | 90 | |||
| –92 | 93 | –3 | –0.04 | –0.06 | 0.11 | ||||
| ND2 D(2) | 0.06 | –3.1 | –4.2 | –96 | 93 | –31 | |||
| –93 | 84 | –121 | –0.06 | –0.08 | 0.14 | ||||
| DFT (model 1) | |||||||||
| Y730-OD | 1.1 | –1.4 | –1.7 | –164 | 137 | 79 | |||
| 119 | 39 | 85 | –0.04 | –0.06 | 0.10 | ||||
| ND2 D(1) | –0.4 | –2.6 | –2.8 | –86 | 98 | 90 | |||
| –92 | 93 | –3 | –0.05 | –0.07 | 0.13 | ||||
| ND2 D(2) | 0.04 | –2.5 | –3.7 | –96 | 93 | –31 | |||
| –93 | 84 | –121 | –0.06 | –0.08 | 0.14 | ||||
| DFT (model 2) | |||||||||
| Y730-OD | 0.75 | –1.8 | –2.2 | –194 | 147 | 58 | |||
| –104 | 121 | –88 | –0.04 | –0.06 | 0.10 | ||||
| ND2 D(1) | 0.25 | –1.4 | –1.5 | –103 | 137 | 95 | |||
| –111 | 80 | 12 | –0.05 | –0.07 | 0.13 | ||||
| ND2 D(2) | 1.0 | –1.0 | –1.8 | –113 | 80 | –17 | |||
| –76 | 64 | –114 | –0.06 | –0.08 | 0.14 | ||||
| DFT (model 3) | |||||||||
| Y730-OD | 1.1 | –1.7 | –2.0 | –163 | 122 | 81 | |||
| 106 | 25 | 84 | –0.04 | –0.06 | 0.09 | ||||
| ND2 D(1) | 0.47 | –2.6 | –3.4 | –98 | 99 | 72 | |||
| –95 | 80 | –15 | –0.05 | –0.06 | 0.11 | ||||
| ND2 D(2) | 0.67 | –2.63 | –3.97 | –100 | 84 | –45 | |||
| –98 | 103 | 43 | –0.05 | –0.06 | 0.11 | ||||
Parameters were obtained from simulations of the orientation selective 94-GHz ENDOR spectra and comparison with the DFT models. The signs of the couplings from the simulation are only relative to each other within one tensor. The Euler angles (α, β, γ) are defined from the A or Q to the g tensor based on the y convention (positive sign for a rotation is counterclockwise, second rotation is around the y axis). The A and Q (quadrupole) tensor are chosen such that |Ax| < |Ay| < |Az|. Within this definition, for both the amino deuterons and the H bond deuteron the Ax direction results along the bond direction. Euler angles from DFT (in the ORCA output positive rotations are defined clockwise) were transformed into the magnetic resonance convention, for comparison. Uncertainty in the parameters from the DFT and ENDOR simulations is estimated up to about 20%.