Electron acceptor compsns. on a supporting substrate having a surface film comprising a plurality of a complex of the formula (I):    -L-((Y1O3-Z-Y2O3)Me(y))k.k*p(X(q-)) (I)    where L = a linking means comprising an organic polymer having side chains substd. with phosphonate or arsonate gps.; Y1 and Y2 = phosphorus or arsenic; Z = a divalent gp. which reversibly forms a stable reduced form and contains two conjugated cationic centres together having a negative Eo red value; X = an anion; Me(y) = Me1nWn; Me1 = a divalent, trivalent, or tetravalent Gp.III, IVA, or IVB metal of at no. 21 or a lanthanide; W = an anion; n = 1-3; m = 0-4; k = 1-100; p = 0-3; q = the charge on X; Y1,Y2, Z and Me1 may be different for each successive k layer and each of complexes is bound to the substrate through L.    Also claimed are:    (A) a compsn. comprising a supporting substrate having a surface film of (i) two or more adjacent metal layers, (ii) organic pillars of formula (Y1O3-Z-Y2O3)-p(X(q-)) (II) covalently joined to two of the adjacent metal layers, (iii) linking means binding the substrate to the metal layer closest to the substrate. Each metal layer, comprises: (a) atoms of a trivalent or tetravalent metal of Gp. III, IVA, or IVB metal 21 or a lanthanide, forming a cohesive layer; and (b) anions bound to the metal atoms such that the metal ions have an effective valence of from 1-6.    (B) A derivatised polymer having a repeating unit of formula (IV); P = P or As; n = 0-10;    (C) a process for prepn. of the complexes;    (D) a catalytic process for prodn. of hydrogen peroxide from oxygen and hydrogen.    USE -   (I) are useful in solar energy conversion and storage, as they can produce a sustained photo-induced charge sepn. state. (I) can be formed on e. g. silicon wafers or vapour deposited gold substrates. (I) permit redn. of various metal ions to produce the zero-valence metal in colloidal form entrapped in the matrices of the compsns. and the resulting matrices can be used, e.g., in the decomposition of water to hydrogen gas; for sensing of oxygen; catalysis, e.g. for hydrogen peroxide prodn. and oligomerisation of methane or higher hydrocarbons, and for redn. of ketones to alcohols.    ADVANTAGE -   The polymer templates show good adhesion to the substrate surface and yield a highly porous structure. The films can be produced in crystalline or amorphous forms and can be given different properties by controlling the dimensions of the interstices, allowing, e.g. for selective redn. of acetophenone in a mixt. of acetophenone and 3,5-di-tert.-butylacetophenone.