Gaussian16 optimizations of triiminobutanenitrile isomers in water PCM model with adjusted epsilon of 144.8. 

Name code: _x_yz - x= 0 - imine groups on opposite sides. x=1 imino groups on the same side. 
y,z : directions of N-H bonds of imine groups. 1-points towards nitrile end, 0 points towards H end.

n4_0_111 is the most stable isomer
The most stable TS4 makes n4_0_000 which is 3.4 (4.3) kcal/mol higher in energy.

B3LYP: Optimizations at B3LYP-D3/6-31+G(d,p) level of theory 
PBE: Optimizations at PBE-D3/6-31G(d,p) level of theory 
