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Tautomerization and Dimerization of 6,13‐Disubstituted Derivatives of Pentacene
Author(s) -
GarciaBorràs Marc,
Konishi Akihito,
Waterloo Andreas,
Liang Yong,
Cao Yang,
Hetzer Constantin,
Lehnherr Dan,
Hampel Frank,
Houk Kendall N.,
Tykwinski Rik R.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201604099
Subject(s) - tautomer , pentacene , chemistry , computational chemistry , combinatorial chemistry , stereochemistry , organic chemistry , layer (electronics) , thin film transistor
Two new 6,13‐disubstituted pentacene derivatives, 1 c and 1 d , with alkyl and triisopropylsilylethynyl substitution have been synthesized and characterized experimentally and computationally. The alkyl substituted 1 c and 1 d represent the first 6‐alkyl‐substituted pentacene derivative where the fully aromatic species dominates over the corresponding tautomer. Indeed, no tautomerization product is found for either 1 c or 1 d upon heating or in the presence of catalytic amounts of acid. On the other hand, an unexpected dimer ( 3 c ) is formed from 1 c . A plausible mechanism for this new dimerization process of the 6‐methyl‐substituted pentacene derivative 1 c is proposed, which involves first a bimolecular hydrogen atom transfer followed by an intramolecular [4+2] Diels–Alder cycloaddition. In the case of 6‐butyl substitution, neither tautomerization nor dimerization is observed. Computations support the proposed 1 c dehydrodimerization pathway, explain why 1 d does not dimerize, and show the importance of the nature of the group at C‐13 in controlling the relative stability of 6‐alkyl‐substituted pentacene tautomers.