the present invention relates to improved covalent coupling of two or more entities such as biomolecules , polymer compositions , organic / inorganic molecules / materials , and the like , including their combinations , through one or more novel reactive groups attached to linker groups of 2 - 1000 atoms length . the present invention also contemplates the use of bifunctional bridge molecules to link two or more entities , wherein the functional groups of the bridge molecules are the novel reactive groups of the present invention .