Scheme 1. reaction steps for the synthesis of MNTzA and BADCh by FOX-7
Computational details
All geometric optimizations are performed at the density functional
theory (DFT) level by using hybrid B3LYP functionals [21-23] with
the basis set def2-TZVP [24,25]. The properties of the optimized
stationary points are characterized by the frequency calculations at the
same theoretical level, with no imaginary frequency for all reactant,
intermediate, and product configurations, and an imaginary frequency
mode for all transition states (TSs). Thermal correction of the electron
energy for the optimized geometry was estimated at an experimental
temperature of 373 K and 1 atmosphere, based on frequency calculations.
Water was used as the solvent, and PCM method [26] was used for SCRF
calculation to simulate the solvent effect. The intrinsic reaction
coordinates (IRC) [27] calculations from first-order saddle points
were performed to locate the local minimum of the reaction path, which
is represented by a solid line in the energy distribution. In order to
obtain more accurate electron energies and reaction barrier heights,
single-point calculations based on the optimized geometry is further
performed by using the B3LYP functional with a larger basis set
def2-QZVP [28]. Gaussian 16 program [29] is used for all DFT
calculations.