Table 3.

Calculated N–COO⁻ bond lengths r_N–C [Å], r_C1–O1/r_C1–O2 [Å] and ESP partial charge on both oxygen atoms for optimised geometries of the ⁺HHNR₁R₂NCOO⁻ and HNR₁R₂NCOO⁻ derivatives of the subset of diamines analysed.

Carbamate derivative	rN−C [Å]		rC–O1/rC–O2 [Å]		ESP charge on O1/O2
	B3LYP	MP2	B3LYP	MP2	B3LYP	MP2
H+-PZ-carbamate	1.513	1.507	1.247/1.247	1.256/1.256	−0.690/−0.690	−0.681/−0.681
PZ-carbamate	1.471	1.477	1.257/1.257	1.264/1.264	−0.743/−0.743	−0.739/−0.739
H+-2,6-DMPZ-carbamate[a]	1.508	1.505	1.248/1.249	1.256/1.256	−0.688/−0.689	−0.680/−0.680
2,6-DMPZ-carbamate[a]	1.469	1.477	1.258/1.258	1.264/1.264	−0.772/−0.772	−0.767/−0.767
H+-2,6-DMPZ-carbamate[b]	1.523	1.527	1.247/1.247	1.255/1.255	−0.691/−0.692	−0.699/−0.698
2,6-DMPZ-carbamate[b]	1.461	1.463	1.260/1.260	1.266/1.266	−0.753/−0.753	−0.749/−0.749
H+-2,5-DMPZ-carbamate[c]	1.505	1.503	1.249/1.247	1.259/1.253	−0.699/−0.665	−0.702/−0.656
2,5-DMPZ-carbamate[c]	1.465	1.470	1.259/1.258	1.266/1.264	−0.750/−7.35	−0.746/−0.731
H+-HHPY-carbamate	1.507	1.503	1.227/1.277[d]	1.235/1.284[d]	−0.641/−0.735[d]	−0.625/−0.736[d]
HHPY-carbamate	1.475	1.478	1.257/1.259	1.263/1.267	−0.762/−0.767	−0.744/−0.751
H+- MHHPY-carbamate	1.417	1.417	1.211/1.354[d]	1.211/1.354[d]	−0.650/−0.772[d]	−0.640/−0.782[d]
MHHPY-carbamate	1.463	1.469	1.258/1.260	1.264/1.266	−0.753/−0.770	−0.746/−0.759
H+-DMHHPY-carbamate	1.555	1.550	1.235/1.244	1.243/1.253	−0.653/−0.699	−0.648/−0.702
DMHHPY-carbamate	1.501	1.500	1.252/1.261	1.258/1.268	−0.758/−0.819	−0.743/−0.816
H+-HHPZ-carbamate	1.390	1.396	1.215/1.350[d]	1.221/1.353[d]	−0.575/−0.660[d]	−0.566/−0.670[d]
HHPZ-carbamate	1.460	1.470	1.254/1.263	1.260/1.267	−0.741/−0.759	−0.736/−0.758

^[a]Isomer 1: R₂=R₃=CH₃ and R₁=R₄=H (Figure 12).

^[b]Isomer 2: R₁=R₄=CH₃ and R₂=R₃=H (Figure 12).

^[c]R₂=R₄=CH₃ and R₁=R₃=H (Figure 12).

^[d]Hydrogen bonding between O2 of the carbamate moiety and a proton of the NH₂⁺ group (Figure 12).