Descrição
Quaternized pyridine derivatives have attracted interest for many years from various
perspectives, especially for potential applications in electronic/optical devices.1 Pyridinium
salts are readily synthesized, highly stable, and often combine intense visible absorptions with
reversible electrochemistry. Notable recently proposed applications of these compounds range
from advanced telecommunications to fluorescent probes for bioimaging.2 As part of an ongoing
program to develop strong charge transfer donor-acceptor thienylpyrrole systems with
enhanced nonlinear optical (NLO) properties3 we have explored the potential of pyrrole 4 and
thienylpyrrole-based chromophores 5-6 as efficient π-electron donor moieties functionalized
with N-methylpyridinium acceptor group substituted at thiophene or pyrrole rings (Figure).
Compounds 4-6 were prepared, in good yields, through Knoevenagel condensation of the
precursor pyrrole 1 or thienylpyrrole 2-34 aldehydes with 1-methylpyridinium salt. On the
other hand, formyl-pyrroles 1 were prepared through Paal-Knorr synthesis followed by
Vilsmeier formylation. The molecular structure, especially the degree of planarity and the
relative orientations of the auxiliary donor and acceptor entities, is found to strongly influence
their electrochemical and NLO properties. In this communication we report on the synthesis,
redox properties, thermal stability and first order nonlinear optical hyperpolarizabilities for
the novel cationic chomophores 4-6. These results indicate that these compounds have good
; Fonseca, A. Maurício C. 
