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Theoretical analysis on geometries and electronic structures of antiaromatic pentalene and its N‐substituted derivatives: monomer, oligomers and polymer
Author(s) -
Liu Binyao,
Shen Wei,
Xie Xiaohua,
Deng Lidan,
Li Ming
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1907
Subject(s) - pentalene , antiaromaticity , diradical , chemistry , singlet state , delocalized electron , molecule , computational chemistry , density functional theory , pyrrole , bond length , electronic structure , crystallography , aromaticity , atomic physics , organic chemistry , excited state , physics
The antiaromatic compounds have received a great deal of attention for several decades because of their unusual electronic structures. The electronic structures and properties of antiaromatic pentalene and its six nitrogen heterocyclic derivatives were systematically studied by the density functional theory at the Becke, three‐parameter, Lee–Yang–Parr level with 6‐31G* basis set. The results indicated that all the monomers have stable singlet states and remarkable bond‐length alternations. From the dimer to polymer in those molecules, pentalene(P), cyclopenta[ b ]pyrrole(CPP), cyclopenta[ d ]imidazole(CPI), pyrrolo[2,3‐ b ]pyrrole(PP1) and pyrrolo[3,2‐ d ]imidazole(PI) are stable diradical structures; pyrrolo[3,2‐ b ]pyrrole (PP2) and imidazo[4,5‐ d ]imidazole(II) are stable singlet ground states. The electronic properties including bond length, bond‐length alternation, electron density at bond critical points, Wiberg bond index and nucleus‐independent chemical shift were analyzed. It was found that in diradical molecules the bond‐length alternations are diminished, the charge tends to equilibrate, the π‐electron delocalization and conjugation are strengthened. The electronic properties of singlet ground state molecules have nearly no variations from monomers to polymers. The band structure analysis shows that diradical structure molecules have small band gaps (<1.0 eV), wide bandwidth and small effective masses of holes and electrons which suggest that diradical structure molecules are very good candidates for conductive materials. Copyright © 2011 John Wiley & Sons, Ltd.