A DFT study on 1,4‐dihydro‐1,4‐azaborinine annulated linear polyacenes: Absorption spectra, singlet‐triplet energy gap, aromaticity, and HOMO–LUMO energy modulation

Abstract

Linear polyacene (LPA) mimics containing multiple heterocycles have been computationally designed by annulating 1,4-dihydro-1,4-azaborinine moieties to benzene (aB1 -aB5 ), naphthalene (aN1 -aN5 ), anthracene (aA1 -aA5 ), and tetracene (aT1 -aT5 ) cores. DFT studies conducted on them using M06L/6-311++G(d,p) method reveal a perfect planar structure for all and suggest the utilization of nitrogen lone pairs for aromatic π-electron delocalization. The computed values of aromaticity indices such as HOMA, NICS, and dehydrogenation energy (Edh ) of heterocycles support strong aromatic character for each six-membered ring in the LPA mimics. On the basis of the minimum value of the molecular electrostatic potential (Vmin ) observed on each LPA unit in the LPA mimics, the extended delocalization of π-electrons is verified. The energetic parameter Edh showed strong linear correlation with HOMA, NICS and Vmin parameters, which strongly supports the multidimensional character of aromaticity in LPA mimics. The electronic property modification is shown by the theoretical absorption spectra data and singlet-triplet energy gap (ΔEST ). The bandgap and ΔEST tunings are achieved for LPA mimics by selecting appropriate number of azaborinine type units and the size of LPA core used for annulation. © 2017 Wiley Periodicals, Inc.