New crystalline complexes were obtained using strategy developed in
recent years, strategy based on acid-base interactions. In this
strategy, strong quadratic nonlinear coefficients of some organic
compounds, are associated with the mechanical and thermal stability of
mineral structures. Many crystals exhibit second harmonic generation of
light. SHG efficiencies were measured using powder Kurtz-Perry method.
Fortunately, for some complexes of melamine, fundamental condition for
SHG, that is the lack of inversion center, was fulfilled. For
centrosymmetric complexes of melamine, their potential ability to
nonlinear optical response was suppressed by the action of inversion
center. In each crystal, the intense hydrogen bond networks were found
and characterized structurally and spectroscopically. In several
crystals phase transitions were found.