Here we study this length effect systematically. We thus synthesized a series of hydrazone thiol (HAT) switches containing an alkyl thiolate linker allowing us to anchor these molecules onto a metal surface. To verify the effect of the distance between the photo-responsive functional group (C=N) and the metal surface on the isomerization of HAT, the number of carbon atoms (Cn) of the alkyl linker was designed to be 3, 8, 10, and 11, as shown in Scheme 1. We investigated the photoisomerization behavior of these hydrazone thiolate switches (Cn HAT, Figure ) in solution, in the solid state, and when assembled as a monolayer on a metal surface, after irradiating them at  = 415 nm or 340 nm. For this, different analytical techniques were employed, including NMR spectroscopy (solution phase), UV-vis spectroscopy (solution phase and at the monolayer level), confocal Raman spectroscopy (solid state), and TERS (at the monolayer level). Finally, TERS mapping was also used to monitor and quantify the photoisomerization of Cn HAT self-assembled monolayers (SAMs) on Au. The photoisomerization behavior of Cn HATs was comprehensively studied from various aspects, which shed light on the substrate-mediated photoisomerization mechanism for hydrazone switches on metal surfaces.