Ruthenium(II) tetra-15-crown-5-phthalocyaninate with axially coordinated molecules of pyrazine [(15C5)4Pc]Ru(pyz)2 (1) was synthesized from carbonyl complex [(15C5)4Pc]Ru(CO)(MeOH) (2), and the structure of the solvate complex (1)·6CHCl3 was revealed by the single crystal X-ray diffraction method. Analysis of crystal packing shows the essential role of weak intermolecular interactions, such as CH…π, CH…N, CH…O and CH…Cl, in the formation of stable assemblies and their organization within the crystals. The interplay between the intramolecular axial coordinated pyrazine contacts and weak intermolecular interactions of solvate molecules with crown-ether fragments provides the basis for rationalizing the observed self-assembling of molecules in solutions of tetrachloroethane and polymeric composites with polyvinylcarbazole. The self-assembling was investigated by means of UV-Vis spectroscopy, dynamic light scattering measurements, AFM and TEM techniques. The formation of nanoparticles of complex (1) from a tetrachloroethane solution after three cycles of heating to 70°C/cooling to 5°C and 2-days storage was proved. Thin films (7 μm) of polymeric composites with polyvinylcarbazole prepared from solution containing nanoparticles exhibit nonlinear optical response measured by the Z-scan technique with application of femtosecond (1030 nm) and nanosecond (1064 nm) pulse lasers. The measured third-order susceptibility (χ(3)) of the polyvinylcarbazole composite with 4 wt% of complex (1) is equal to 1.94×10–10 esu, while the same composite prepared without the above-described special treatment has zero susceptibility. This result proves the essential role of self-assembling in further development of nonlinear optical materials.