Kcal/mol and 27.4 Kcal/mol for 5 CN and 5 tBu respectively. This is very interesting because the highest activation energy is only 27.4 kcal/mol which implies that these carbenes are able to activate N 2 at room temperature. This result is also inspiring because the change in the carbene frame through the addition of one C = O group is found effective for lowering the activation energy. The high activity of carbene due to the presence of the C = O group in the carbene frame and the CN functional group connected to the heteroatom of the carbene frame support our conclusion regarding the binding nature discussed earlier. Unfortunately, the free energy change of this process is still positive for all of the substituents. The stability order of the diazo derivative is CN > CF 3 > P h > M e > H > tBu > OM e. The most stable diazo derivative is for the 5 CN (free energy change is 13.5 kcal/mol). At present, there is no clue to find a better carbene that would be effective for N 2 activation at room temperature and produce a thermodynamically stable diazo derivative.