QUATERTHIOPHENEDIPHOSPHONIC ACID (QDP) - A RIGID, ELECTRON-RICH BUILDING BLOCK FOR ZIRCONIUM-BASED MULTILAYERS

The title compound, synthesized in three steps from 2,2'-bithiophene, was deposited alternately with tetravalent zirconium as a multilayer on phosphorylated substrates. This is the first example of zirconium phosphonate multilayer formation with either a nonaliphatic or a rigid diphosphonic acid. Procedures were devised for (3-aminopropyl)silylating, phosphorylating, and zirconating silicon oxide surfaces. Deposition of QDP onto these surfaces proceeded best from DMSO solution at 80-degrees-C. Ellipsometry, UV absorbance, and X-ray fluorescence were consistent with formation of densely packed films. The films were insulating and were unresponsive to I2 vapor, whereas Br2 caused reversible surface doping. We hope to employ QDP as an electron-donating element in heterogeneous multilayers based on the zirconium phosphonate deposition strategy.