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 and related C-P bonded compounds;Tervalent phosphorus acid derivatives;Phosphine chalcogenides;Phosphonium salts and P-ylides;Nucleotides and nucleic acids: mononucleotides;Quinquevalent phosphorus acids;Pentacoordinated and hexacoordinated compounds;Phosphazenes;Green synthetic approaches in organophosphorus chemistry: recent developments