2 Methyl 4 nitroaniline , nonlinear

While gas phase work on the h5q5erpolarizability of small molecules has been relatively free of problems concerned with the definitions of measured quantities and their formal relationship to computed quantities, the same cannot be said about solution studies of rather larger organic species. It is the latter that possess the very large nonlinear response functions that are of greatest interest. The prototype system for such studies has been 4-nitroaniline (pNA) and this review is mainly concerned with the relation between the measurements, in vacuo and in solution, of the hyperpolarizabilities of pNA and the closely related molecule, MNA (2-methyl, 4-nitroaniline) to ab initio and DFT calculations of these quantities. 

Electronic and Nonlinear Optical Properties of 2-Methyl-4-Nitroaniline Clusters (M. Guillaume, B. Champagne, F. Castet L. Ducasse)... 

For these classes of conjugated molecular and polymer structures, the principal property is that their nonreson-ant, nonlinear optical responses are dominated by ultrafast, virtual excitations of the ir-electron states. This was directly demonstrated by MNA (2-methyl-4-nitroaniline) single crystal measurements of macroscopic second order susceptibilities at do (j 3) and optical frequencies (13-1 ) and combined second harmonic measurements and theo-... 

Chapter 2 Electronic and Nonlinear Optical Properties of 2-Methyl-4-Nitroaniline Clusters... 

The supennolecule approach is used to study the linear and second-order nonlinear susceptibilities of the 2-methyl-4-nitroaniline ciystal. The packing effects on these properties, evaluated at the time-dependent Hartree-Fock level with the AMI Hamiltonian, are assessed as a function of the size and shape of the clusters. A simple multiplicative scheme is demonstrated to be often reliable for estimating the properties of two- and three-dimensional clusters from the properties of their constitutive one-dimensional arrays. The electronic absorption spectra are simulated at the ZINDO level and used to rationalize the linear and nonlinear responses of the 2-methyl-4-nitroaniline clusters. Comparisons with experiment are also provided as well as a discussion about the reliability of the global approach. 

In this experiment, three nitroaniline derivatives, i.e. p-nitro -aniline (p-NA), 2-hydroxy-i -nitroaniline(HNA) and N-methyl-i -nitroaniline (NMNA), were chosen as guest molecules because of their large optical nonlinearity. As a host molecule, dimethyl /-cyclodextrin (dimethyl f -CD) was used. It is well known that dimethyl /-CD forms an inclusion complex with many kinds of aromatic derivatives. 

Nason et al. [20] reported that polycrystalline thin films (1-10 /am) of the nonlinear material 2-methyl-4-nitroaniline were deposited on Ag, Cu, and Si by conventional and ionized cluster beam deposition. The use of ions was found to promote a highly oriented film, with only a single x-ray diffraction orientation (112) being observed at reduced temperatures (-50 C). The effect of the ions on the physical microstructure of the films was to densify the film and reduce the size of the microcrystals. The films had powder-like optical properties and displayed a strong second harmonic from an N YAG laser. 

The most common nonlinear optical molecules, with a donor—Ji-system—acceptor structure are, as a rule, neutral in the ground state and become charged in the excited state by electron transfer, in contrast with 4 -[Methyl(diphenyl)phosphonio]biphenyl-4-yl triphenylborate (PBB), which has a high dipole moment in the ground state and a lower one in the excited state. The hyperpolarizability P of PBB is comparable to that of p-nitroaniline and fortunately PBB shows transparency above 400 nm. 

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