Title

Electronic Transitions In A Series Of 2-Azaazulene Polymethine Dyes With Different Π-Conjugation Lengths

Keywords

π-Conjugated chain; 2-Azaazulenes; Bond length alternation; Localized and delocalized molecular orbitals; Polymethine; Quantum chemical calculations; Symmetry breaking; Terminal groups; Wave of charge

Abstract

A comprehensive quantum chemical analysis along with spectral-luminescence measurements has been performed for a new series of 2-azaazulene dyes with different conjugation lengths (n) to better understand the nature of their electronic transitions. The remarkably large red shift of their main absorption bands at relatively small n is connected with the existence of totally delocalized HOMO and LUMO. Symmetry breaking is observed experimentally at n = 3 in polar solvents and theoretically at n = 5 in vacuum. Analysis shows the existence of two types of molecular orbitals (MOs): local with the charge mainly localized within the terminal groups, and delocalized with the charge distributed throughout the molecule. Correspondingly, three types of electronic transitions are present: between delocalized MOs; between one local and one delocalized MO, and between local MOs only, which is important for predicting the positions of electronic transitions to the chain length. © 2012 Elsevier B.V. All rights reserved.

Publication Date

1-16-2013

Publication Title

Chemical Physics

Volume

411

Number of Pages

17-25

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.chemphys.2012.11.017

Socpus ID

84872961555 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84872961555

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