**1. Introduction**

Presently, one can remark a continuous increase of the need for new technologies adjusted to the market request. This involves obtaining new high-performance materials and new microelectronic, optical devices, whence appearing these requests. Because we begin will be habitually with these advantages, our expectations demand a higher efficiency, faster and more reliable materials answers, safe environmentally technologies.

Optical nonlinearity (NLO) is not an exotic phenomenon. Indeed, all materials are optically nonlinear if light is sufficiently intense.

The last decade of past century was marked by a revolution in the field of materials synthesis for optical and photonic applications. It is noteworthy major dispute regarding the origin of these materials: inorganic or organic, natural or synthetic, hybrid or pure?

Thus, the fundamental problem in the development of this class of materials still remains the formulation of a theoretical model, which generalizes the particularities of interaction of the stimulating electromagnetic field with the specific micromolecular constituents for each class of compounds.

In this regard, perhaps the greatest challenge is (outside the design synthesis, characterization and understanding of novel molecular and macromolecular assemblies with applicability in non-linear optical fields) the interfacing nature of research, which brings together specialists in chemistry, physics and materials science. Initially, a test stone for chemists, photonics materials require the rational construction of supramolecular assemblies characterized by preordained collective phenomena consequence of intermolecular interactions and their spatial relationships.

It is classic that the high values of the electronic polarization are characteristic for π-conjugated molecules. This justifies the many generalizing predictions that material systems with extended π- conjugation will be characterized by high values of hyperpolarizabilities.
