Does the Intramolecular Hydrogen Bond Affect the Spectroscopic Properties of Bicyclic Diazole Heterocycles?

Table 3

Occupancy of natural orbitals (NBO), corresponding to the C-H^…O intramolecular contacts, obtained at B3LYP/aug-cc-pVDZ; E⁽²⁾ means energy of hyperconjugative interactions; E_i-E_j is energy difference between donor and acceptor NBO orbitals. Designation of species according to Scheme 1.

Compound		Acceptor (A); C-H		Donor (B); C=O			E^(2)AB; (kcal/mol)	Ei-Ej; (a.u.)
		Type	Occupancy	Type	Occupancy	Hybrid (O)
2	R2 = CH3, R3 = H	BD	0.00944	LP(2)	1.85498	s (0.00%), p 1.00 (99.67%), and d 0.00 (0.33%)	1.32	0.67
3	R2 = CH2Cl, R3 = H	BD	0.01785	LP(2)	1.85014	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	1.37	0.65
4	R2 = CHCl2, R3 = H	BD	0.03173	LP(2)	1.84338	s (0.01%), p 1.00 (99.65%), and d 0.00 (0.34%)	2.87	0.67
5	R2 = CH3, R3 = Cl	BD	0.01231	LP(2)	1.84837	s (0.01%), p 1.00 (99.66%), and d 0.00 (0.33%)	1.63	0.68
6	R2 = CH2Cl, R3 = Cl	BD	0.01943	LP(2)	1.84368	s (0.01%), p 1.00 (99.64%), and d 0.00 (0.34%)	1.71	0.66
7	R2 = CHCl2, R3 = Cl	BD	0.03248	LP(2)	1.84651	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	2.65	0.67
8	R2 = CH3, R3 = NH2	BD	0.01129	LP(2)	1.85463	s (0.00%), p 1.00 (99.67%), and d 0.00 (0.33%)	1.48	0.68
9	R2 = CH2Cl, R3 = NH2	BD	0.01876	LP(2)	1.85009	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	1.56	0.66
10	R2 = CHCl2, R3 = NH2	BD	0.03187	LP(2)	1.84175	s (0.01%), p 1.00 (99.65%), and d 0.00 (0.34%)	1.57	0.64
11	R2 = CH3, R3 = CH3	BD	0.01110	LP(2)	1.85514	s (0.00%), p 1.00 (99.67%), and d 0.00 (0.33%)	1.74	0.68
12	R2 = CH2Cl, R3 = CH3	BD	0.01830	LP(2)	1.85056	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	1.19	0.66
13	R2 = CHCl2, R3 = CH3	BD	0.03176	LP(2)	1.84328	s (0.01%), p 1.00 (99.65%), and d 0.00 (0.34%)	1.41	0.64
14	R2 = CH3, R3 = CH2CH2CH2Cl	BD	0.01154	LP(2)	1.85466	s (0.00%), p 1.00 (99.67%), and d 0.00 (0.32%)	1.77	0.68
15	R2 = CH2Cl, R3 = CH2CH2CH2Cl	BD	0.01891	LP(2)	1.85004	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	1.86	0.66
16	R2 = CHCl2, R3 = CH2CH2CH2Cl	BD	0.03221	LP(2)	1.85237	s (0.01%), p 1.00 (99.66%), and d 0.00 (0.33%)	1.89	0.65
17	R2 = CH3, R3 = CH2CH2CH2NH2	BD	0.01102	LP(2)	1.85699	s (0.00%), p 1.00 (99.67%), and d 0.00 (0.32%)	1.53	0.68
18	R2 = CH2Cl, R3 = CH2CH2CH2NH2	BD	0.01866	LP(2)	1.85040	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	1.62	0.66
19	R2 = CHCl2, R3 = CH2CH2CH2NH2	BD	0.03193	LP(2)	1.84319	s (0.01%), p 1.00 (99.65%), and d 0.00 (0.34%)	1.47	0.65
20	R2 = CH3, R3 = CH2CH2CH2NHC(NH)NH2	BD	0.01143	LP(2)	1.85483	s (0.00%), p 1.00 (99.67%), and d 0.00 (0.32%)	1.83	0.68
21	R2 = CH2Cl, R3 = CH2CH2CH2NHC(NH)NH2	BD	0.01838	LP(2)	1.85023	s (0.00%), p 1.00 (99.66%), and d 0.00 (0.34%)	1.92	0.66
22	R2 = CHCl2, R3 = CH2CH2CH2NHC(NH)NH2	BD	0.03209	LP(2)	1.84293	s (0.01%), p 1.00 (99.65%), and d 0.00 (0.34%)	1.95	0.65