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Bis(1,3‐dithiole) Polymethine Dyes for Third‐Order Nonlinear Optics – Synthesis, Electronic Structure, Nonlinear Optical Properties, and Structure‐Property Relations
Author(s) -
Simonsen Klaus Bæk,
Geisler Tommy,
Petersen Jan Conrad,
Arentoft Jesper,
SommerLarsen Peter,
Greve Daniel Rodriguez,
Jakobsen Christian,
Becher Jan,
Malagoli Massimo,
Brédas Jean Luc,
Bjørnholm Thomas
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199812)1998:12<2747::aid-ejoc2747>3.0.co;2-n
Subject(s) - cyanine , hyperpolarizability , chemistry , chromophore , nonlinear optics , molecule , computational chemistry , molecular orbital , ab initio , atomic electron transition , ab initio quantum chemistry methods , absorption (acoustics) , nonlinear optical , electronic structure , photochemistry , nonlinear system , organic chemistry , fluorescence , optics , physics , quantum mechanics , astronomy , polarizability , spectral line
The synthesis of a series of new sulfur‐containing polymethine dyes is reported. The linear optical properties of these bis(1,3‐dithiole) (mono‐, tri‐, penta‐, and hepta‐)methine dyes show intense and narrow optical absorptions typical of cyanine dyes. The absorption maximum is increasingly red‐shifted from 489 nm for the monomethine dye to 911 nm for the heptamethine compound. Based on third‐harmonic generation measurements at fundamental wavelength between 1064 nm and 1907 nm, γ values were evaluated to lie in the range between 1·10 −33 e.s.u. and 14·10 −33 e.s.u. showing that the nonlinear response of the bis(1,3‐dithiole) polymethine dyes compare well with other organic π‐electron systems of similar size. Comparisons of the experimental values of γ to calculated static values obtained by ab initio and semiempirical calculations (AM1, PM3) have been made as well as comparisons to dynamic values estimated from a free‐electron model. The computed dynamic values can be described by a power law; γ ≈ L 5 where L denotes the length of the molecules. Our studies confirm the stabilizing effect of a carbocyclic ring in the cyanine backbone making the heptamethine dye an unusually stable and highly nonlinear polymethine chromophore possessing a strong NIR optical transition and very good transparency in the visible region.