Professor David Allen is Emeritus professor of chemistry at the Sheffield Hallam University, UK. His main research interests are in phosphonium salts and related compounds. Current interests include the preparation of phosphonioalkyl derivatives of biologically active molecules, the phosphonioalkyl group facilitating the passage of the biologically active agent through cell membranes, and studies of the formation of biologically active surface-functionalised gold nanoparticles.

• Phosphines: preparation, reactivity and applications;Phosphine chalcogenides;Tervalent phosphorus acid derivatives;Phosphonium salts and P-Ylides;Quinquevalent phosphorus acids;Pentacoordinated and Hexacoordinated Compounds;Phosphazenes;Green synthetic approaches in organophosphorus chemistry: recent developments