Quadratic nonlinear optical properties of novel pyridinium salts

Abstract

A number of novel salts of dipolar cations containing dimethylamino electron donor and pyridinium electron acceptor groups have been prepared and studied by using various physical techniques including hyper-Rayleigh scattering and Stark (electroabsorption) spectroscopy. In addition to showing very large molecular static first hyperpolarizabilities, several of these salts exhibit pronounced bulk quadratic nonlinear optical effects. Related compounds in which the electron donor is a pyridyl-coordinated ruthenium(II) ammine centre have also been investigated, allowing interesting comparisons to be made between transition metal-containing and purely organic nonlinear optical chromophores.

Resolution of the First Nonracemic Diquats

“…[3] Diquats may also be used as structural templates for efficient supramolecular synthesis, [4] as electron acceptors in light-harvesting chromophore-quencher systems, [5] for the construction of ion-pair charge-transfer complexes, [6] and in nonlinear optics. [7] Diquat derivatives are also noteworthy for their (axial) chirality: the compounds exhibit P (or S a ) and M (or R a ) atropisomeric conformations owing to the noncoplanarity of the two linked pyridinium rings ( Figure 1). The enantiomers are exchangeable owing to rotation about the biaryl axis.…”

A New Nonlinear Optical Stilbazolium Family Crystal of (E)-1-Ethyl-2-(4-nitrostyryl) Pyridin-1-ium Iodide: Synthesis, Crystal Structure, and Its Third-Order Nonlinear Optical Properties

“…Some organic compounds that are considered nonlinear, such as D-π-A-type substituted stilbazolium derivatives, are very smart optical candidates for generating THz waves and for electro-optic and photonic applications, as they provide second- and third-order NLO responses. − Nonlinearity occurs due to strong Coulombic interactions, high chromophore density, orientation of long-term stability, and strength of donor and acceptor groups with delocalized π-electrons that can enhance asymmetric polarization. , Stilbazolium cations (chromophores) are a major source for nonlinearity, and the variation of the counterions of these salts proved to be an effective strategy for the development of materials with macroscopic high nonlinearity based on Coulomb interactions. − Using this approach, many stilbazolium derivatives with large optical nonlinearities have been extensively explored by many research teams, such as DAST (4- N , N -dimethylamino-4′- N ′-methyl-stilbazolium tosylate), DSNS (4- N , N -dimethylamino-4′- N ′-methyl-stilbazolium 2-naphthalenesulfonate), and so on. Moreover, in recent times, efficient third-order NLO efficiency of stilbazolium derivatives with increasing significance of ICT between the donor and acceptor has been engineered. − Therefore, new NLO materials are to be sought in the stilbazolium family so that they can be utilized effectively for optical applications.…”

“…13−19 Nonlinearity occurs due to strong Coulombic interactions, high chromophore density, orientation of long-term stability, and strength of donor and acceptor groups with delocalized π-electrons that can enhance asymmetric polarization. 20,21 Stilbazolium cations (chromophores) are a major source for nonlinearity, and the variation of the counterions of these salts proved to be an effective strategy for the development of materials with macroscopic high nonlinearity based on Coulomb interactions. 22−27 Using this approach, many stilbazolium derivatives with large optical nonlinearities have been extensively explored by many research teams, such as DAST (4-N,N-dimethylamino-4′-N′-methyl- stilbazolium tosylate), 26 DSNS (4-N,N-dimethylamino-4′-N′methyl-stilbazolium 2-naphthalenesulfonate), 27 and so on.…”

Pentacyanoiron(II) as an Electron Donor Group for Nonlinear Optics: Medium-Responsive Properties and Comparisons with Related Pentaammineruthenium(II) Complexes

“…Our previous contributions to the field of organotransition metal NLO compounds have focused primarily on the quadratic NLO properties of a range of ruthenium ammine complexes of pyridinium-substituted ligands. 2m,3a, Recently, we have also been extending our scope to include other types of complexes, and one promising, readily accessible, and suitably electron-rich metal center is {Fe II (CN) 5 } 3- . Many previous reports have described the syntheses and properties of complexes containing this moiety coordinated to a wide variety of ligands, including many discussions of MLCT spectroscopic properties, but no NLO studies with such complexes have hitherto been disclosed.…”