Preparation and Third-Order Nonlinear Optical Properties of Novel Axial Fullerenol-Substituted Phthalocyanines

This research presents the optical limiting properties of a novel axially linked D-A type compound, LaPc-C60(OH)n, where lanthanide phthalocyanine serves as the donor and fullerenol as the acceptor. The incorporation of fullerenol expands the π-conjugated system, decreases the aggregation of the phthalocyanine, and significantly increases the solubility of the compound. The establishment of this D-A system promotes intramolecular electron transfer, effectively improving both the non-linear optical (NLO) response and optical limiting properties. In addition, homogeneous poly(methyl methacrylate) (PMMA) composite films (LaPc-C60(OH)n/PMMA) are prepared using a simple solution casting method. Compared to fullerenol or lanthanum phthalocyanine individually, LaPc-C60(OH)n exhibited a superior NLO response both in solution and in the solid composite film. In particular, LaPc-C60(OH)n/PMMA demonstrated an increase in the non-linear absorption coefficient (2050 cm GW⁻¹) and a larger third-order magnetization (1.84 × 10⁻⁸ esu). In addition to exhibiting an excellent NLO response at 532 nm, LaPc-C60(OH)n also shows significant NLO enhancement at 1064 nm, extending the limiting range into the near-infrared region. This behavior is attributed to different nonlinear absorption mechanisms and the synergistic effect that arise from the photo-induced electron transfer process between the fullerenol and LaPc.