Abstract: Langmuir Blodgett films are provided having second order molecular hyperpolarizability of at least 30.10.sup.-50 C.sup.3 m.sup.3 J.sup.-2. combined with chemical stability and a melting point of over 70.degree..They also have desirable pyroelectric properties shown by a static pyroelectric coefficient of at least 0.0039 nCcm.sup.2 k.sup.-1. The films comprise compounds of the following formula: ##STR1## wherein M is ruthenium, iron or cobalt; R.sup.1 is cyclopentadienyl, methylcyclopentadienyl, pentamethylcyclopentadienyl or indenyl;A.sup.1 is (R.sup.2).sub.3 Z or carbonyl;Q.sup.2 is (R.sup.2).sub.3 Z or carbonyl;Z is phosphorus or arsenic;R.sup.2 is an aryl of alkyl radical;A is ##STR2## Y is a straight chain alkyl or alkoxy radical comprising from 3 to 17 carbon atoms, or, when A is ##STR3## N(R.sup.3).sub.2 ; R.sup.3 is a lower alkyl radical comprising up to 5 carbon atoms; andX is PF.sub.6 or BF.sub.4.

Abstract: A barrier assembly for a Langmuir trough is arranged for a substrate to be carried automatically to-and-fro on a dipping head over a fixed barrier into monomolecular layers A, B on a common subphase so as to stack layers ABABAB . . . on the substrate. The layers A, B are confined by the barrier and two constant perimeter areas formed by a single flexible band passing over rollers. By adjusting the positions of bridges that carry some of the rollers, the confined areas can be contracted to compress the layers A, B. In an alternative mode the substrate receives a layer from layer A while a new layer B is being formed, the substrate then being transferred to layer B while a new layer A is being formed. This involves an oscillating rather than a rotating movement of the substrate.

Abstract: A method of preparing a thin film of a phthalocyanine compound on a substrate comprising forming a thin layer of the phthalocyanine compound on the surface of a suitable liquid and passing the substrate through the layer so that a film of the phthalocyanine is deposited upon the surface of the substrate. Very thin films are formed and the resulting composite articles are useful in the manufacture of electronic, electrical, electrochemical and photochemical devices of high sensitivity.