The formation and characterisation of a novel self-assembled monolayer him for gas sensing are reported, The phthalocyanine, 1.1',4.4',8,8'11,11',15.15,18,18,22,22'-tetradecakishexyl-25,25'-(3,3'-dithiodipropyl)diphthalocyanine, has been synthesised from its hydroxypropyl precursor, via a two-step reaction. The disulfide functionality of the molecule has been used to produce a self-assembled phthalocyanine monolayer on a gold substrate. The phthalocyanine monolayer has been characterised using reflection absorption infrared spectroscopy (RAIRS).