Ultrathin Langmuir–Schaefer films of slipped-cofacial J-type phthalocyanine dimer: Supramolecular organization, UV/Vis/NIR study and nonlinear absorbance of femtosecond laser radiation

Highlights: • Stable phthalocyanine J-type dimers are capable of forming low-defect thin films. • Thin films of dimeric J-type Zn complex demonstrate ordered H-aggregation. • A simple way of calculating the parameters of optical limiting has been developed. Based on a comprehensive theoretical and experimental approach, a low-defect thin film of stable dimeric phthalocyanine zinc complex (bis-[2-hydroxy-9(10),16(17), 23(24)-tri-tert-butylphthalocyanine]zinc – J-[^OHPc^tZn]₂) was prepared. It is shown that the dye forms stable amorphous edge-on monolayers at the air/water interface with an insignificant content of cylindrical 3D aggregates. These floating layers keep their structure when transferred by the Langmuir-Schaefer method onto a solid substrate, demonstrating a tendency towards ordered H-aggregation with preserving their linear molecular properties. Mixed two- and three-photon absorption of femtosecond laser pulses (280 fs) was firstly detected on this sample, as well as the ability of a material to the nonlinear attenuation of the intense irradiation, which is important for optical limiting.