Triptycene-Based Tripodal Molecular Platforms: A Comparative Study of Photoswitchable Langmuir-Blodgett Films on Metallic and Nonmetallic Surfaces.

Photoswitchable molecular systems confined at solid interfaces often exhibit altered photochemical behavior due to strong substrate coupling and restricted molecular motion. Here, we investigate whether a triptycene-based tripodal platform can effectively decouple photoactive units from metallic and nonmetallic surfaces in Langmuir-Blodgett (LB) films. Four structurally distinct photoswitches were incorporated into a common tripodal scaffold and assembled into organized monolayers at the air-water interface, followed by transfer onto quartz and gold substrates. Comprehensive characterization confirms the formation of homogeneous, monomolecular films with controlled thickness (∼2 nm) and reproducible surface coverage. UV-vis spectroscopy reveals that the photochemical response of surface-bound systems closely resembles that observed in solution, with comparable switching behavior and thermal kinetics on both substrates. Notably, no systematic differences are observed between metallic and nonmetallic surfaces, demonstrating effective electronic decoupling by the tripodal architecture. In contrast, the azobenzene-containing system exhibits asymmetric switching behavior governed by intermolecular packing within the monolayer, rather than substrate interactions. These findings establish tripodal molecular platforms as a robust strategy for preserving intrinsic photoswitch functionality in surface-confined environments and provide key design principles for photoswitchable interfaces.