Abstract
Relatively scarce literature data on BN/CC isosterism in 4nπ‐electronic systems have prompted us to investigate theoretically the influence of BN pair position within the central butadiene fragment of dibenzo[a,e]pentalene on two fundamental molecular properties: stability and (anti)aromaticity. It was found that stability and aromaticity follow the same trend only for BN‐orientational isomers. The source of different stability of other isomers was examined first by an analysis of bond types and their dissociation energies and then by isomerization energy decomposition analysis and was explained in terms of classical electrostatic interactions, quantum‐mechanical orbital interactions, structural changes and electronic changes (transition from charge‐separated π‐system to the neutral one). (Anti)aromaticity was investigated by using three kinds of indices, HOMA, FLUπ, and NICS(1)zz, which indicated that delocalization at the central pentalene motif is almost unaffected by various BN arrangements, molecular perimeter is slightly affected, while the most affected subunits are five‐membered rings and benzene‐fused five‐membered rings containing only one heteroatom.
Highlights
NICS(1)zz data are given inside the rings
HOMA and FLU data, which are shown below the structures, correspond to individual rings and to the central pentalene moiety and those which are given above the structures refer to the two benzene-fused five-membered rings and to the perimeter of a molecule
On the basis ofaromaticity analysis only antiaromaticity of borole moiety, weaker aromaticity of benzene fused to it and weaker delocalization at molecular perimeter can be used to explain lower stability of 1,4 relative to 2,1. This explanation does not seem to be enough to account for the large energy difference between the isomers (25.24 kcal/mol)
Summary
Experimental and calculated bond lengths and bond angles for. 117.58/118.17 a Experimental data are from X-ray analysis of compound II Section S1: Comparison of (anti)aromaticity of various isomers of BN-dibenzopentalenes.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: 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.
