Abstract
In contrast to typical borepins, which appear about 40.0 kcalmol−1 more stable than their corresponding tautomeric boranorcaradienes, we have found 2 species, which have reversed this trend and pushed the equilibrium in favor of their corresponding boranorcaradienes. They are namely 1a,9b-dihydro-1H-borireno[2,3-h]pyridazino[4,3-f]cinnoline and 1a,9b-dihydro-1H-borireno[2,3-h]pyrimido[5,4-f]quinazoline which stand up among 14 isomeric systems probed, at B3LYP/AUG-cc-pVTZ, M06-2X/AUG-cc-pVTZ, MP2/AUG-cc-pVTZ, and HF/AUG-cc-pVTZ. Energy barriers are calculated in gas-phase, where the possibility of a rapid interconversion of the isomers is ruled out. Generally, dibenzoboranorcaradienes assume Cs symmetry with planar geometry and dihedral angle of zero degree. In contrast, their corresponding borepins show a high tendency for puckering with dihedral angle of ~66°. The preference of the latter for puckered non-planar geometries is evidenced by natural bonding orbitals calculations and visually through their frontier molecular orbitals. Main interactions appear to be hyperconjugations of σ and π bonds across the rings. Position and number of nitrogen atoms on the fused rings seem to affect the energy gap, dipole moment, symmetry, dihedral angle, the chemical shift, NICS, bond lengths, and charge distribution.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.