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A first principles calculations and experimental study of the ground- and excited-state properties of ladder oligo(p-aniline)s.
MedLine Citation:
PMID:  15839725     Owner:  NLM     Status:  PubMed-not-MEDLINE    
The molecular structure of three ladder oligo(p-aniline)s, 5,11-diethyl-6,12-dimethylindolo[3,2-b]carbazole (DIMER 2P), 14-ethyl-5,8-dihydro-diindolo[3,2-b:2',3'-h]carbazole (TRIMER 2P), and 5,8,14-triethyl-diindolo[3,2-b:2',3'-h]carbazole (TRIMER 3P) were investigated by first principles calculations at the Hartree-Fock (HF6-31G*) and density functional theory (DFTB3LYP6-31G*) levels. It is found that the agreement between theoretical and x-ray geometrical parameters is good and rather similar for both theoretical methods. The nature and the energy of the first two singlet-singlet electronic transitions have been obtained by Zerner intermediate neglect of differential overlap/spectroscopy semiempirical calculations performed on the HF6-31G* and DFTB3LYP6-31G* optimized geometries, as well as time-dependent density functional theory (TDDFT) calculations performed on the DFTB3LYP6-31G* optimized structures. For all the compounds and for all the theoretical approaches, it is observed that the S(1)<--S(0) electronic transition (pipi*) is weakly allowed and polarized along the short axis (y) of the molecule. On the other hand, the S(2)<--S(0) electronic transition of each oligomer possesses a much larger oscillator strength and is polarized along the long (x) molecular axis. It is found that TDDFT calculations provide the best overall agreement between the energies and the corresponding optical transitions obtained from the absorption bands (0-0 peaks) measured in dichloromethane as well as providing a good evaluation of the bathochromic shifts caused by the increase in the conjugation length or by the presence of extra alkyl chains on the nitrogen atoms in TRIMER 3P compared to TRIMER 2P.
Michel Belletête; Gilles Durocher; Sébastien Hamel; Michel Côte; Salem Wakim; Mario Leclerc
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of chemical physics     Volume:  122     ISSN:  0021-9606     ISO Abbreviation:  J Chem Phys     Publication Date:  2005 Mar 
Date Detail:
Created Date:  2005-04-20     Completed Date:  2006-04-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375360     Medline TA:  J Chem Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  104303     Citation Subset:  -    
Département de Chimie, Université de Montréal, Montréal, Quebec H3C 3J7, Canada.
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