Jackson Benjamin A, Miliordos Evangelos
Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849-5312, USA.
Phys Chem Chem Phys. 2020 Mar 28;22(12):6606-6618. doi: 10.1039/c9cp06050b. Epub 2020 Mar 11.
Zirconium monoxide, ZrO, was studied by multi-reference configuration interaction (MRCI) and coupled cluster methods using large basis sets in conjunction with effective core potentials. Complete potential energy curves were constructed and bonding patterns are proposed for several electronic states. Numerical results include accurate equilibrium bond lengths, harmonic vibrational frequencies, anharmonicities, excitation energies, dipole moments, and binding energies for both ground and excited states. The application of a ZrO unit as the catalytic center for methane activation is explored through the reaction ZrO + CH→ Zr + CHOH. Optimal density functional structures combined with single-point MRCI energy calculations are obtained for the complete reaction pathway. It is found that the lower energy singlet and triplet multiplicities (oxo states) favor the [2+2] mechanism and the higher energy quintets (oxyl states) favor the radical mechanism, which is overall more efficient in producing methanol. We finally suggest proper ligands that stabilize the oxyl states. These include halogens or other weak-field ligands, which finally convert the inert early transition metal oxide units to efficient methane-to-methanol catalysts.
使用大基组结合有效核势，通过多参考组态相互作用（MRCI）和耦合簇方法对一氧化锆（ZrO）进行了研究。构建了完整的势能曲线，并提出了几种电子态的成键模式。数值结果包括基态和激发态的精确平衡键长、谐振动频率、非谐性、激发能、偶极矩和结合能。通过反应ZrO + CH→Zr + CHOH探索了ZrO单元作为甲烷活化催化中心的应用。获得了完整反应路径的最佳密度泛函结构并结合单点MRCI能量计算。结果发现，较低能量的单重态和三重态多重度（氧代态）有利于[2+2]机理，而较高能量的五重态（氧基态）有利于自由基机理，总体而言，自由基机理在生成甲醇方面更有效。我们最终提出了稳定氧基态合适配体。这些配体包括卤素或其他弱场配体，它们最终将惰性早期过渡金属氧化物单元转化为高效的甲烷制甲醇催化剂。
