Preparation, luminescence and photoelectric properties of Langmuir–Blodgett films of alkynylplatinum(II)–zinc(II) porphyrinate/heteropolyoxometalate hybrid composites

A new class of organometallic/inorganic hybrid Langmuir–Blodgett (LB) films, consisting of rigid-rod alkynylplatinum(II)–zinc(II) porphyrinate complex (OMA) as the π-conjugated donor–acceptor-type molecule and tungsto(molybdo)phosphoric heteropolyacids (HPA) (HPA = H3PMo12O40 and H3PW12O40, abbreviated as HPMo12 and HPW12, respectively) of the Keggin structure as the inorganic component, were prepared and characterized by π–A isotherms, UV–vis absorption and luminescence spectra, low-angle X-ray diffraction, scanning tunneling microscopy and surface photovoltage spectroscopy. Our experimental results indicate that stable, well-defined and well-organized Langmuir and LB films have been formed in pure water and heteropolyacid subphase. They typically have a highly organized lamellar structure in which a monolayer of HPA is most likely embedded inside the OMA molecular space formed by long chains of PBu3. Luminescence spectra of these hybrid LB films show that HPMo12 and HPW12 can enhance the emission of OMA to some extent. These LB composites show good photovoltage responses and a photovoltage of 79 μV can be obtained for the OMA/HPMo12 system when it is excited by light. The monolayer LB films on ITO wafer can also display interesting electrical conductivity.