A nitrogen complex of an inorganic phosphate comprising the anionic sub-structure (I)； whereby a nitrogen atom (N) of a complexing agent is complexed to an oxygen atom (O) of the inorganic phosphate； wherein the nitrogen atom is selected from the group consisting of a nitrogen atom of an amine group or a nitrogen atom of a N-heteroaromatic ring； and wherein A and A' are each independently selected from the group of constituents consisting of a hydroxyl group (-OH), an oxide group (-O<；SUP>；-<；/SUP>；), the group -OR where R is alkyl or substituted alkyl； an oxygen to which a nitrogen is complexed (-0<；-N) wherein the nitrogen atom is selected from the group consisting of a nitrogen atom of an amine group or a nitrogen atom of a N-heteroaromatic ring； and a phosphate of the form (i)； wherein each of A'' and A''' are selected independently from the same group of substituents as A and A'； wherein at least one of A, A', A'' and A''' is an oxide (-O<；SUP>；-<；/SUP>；) with the proviso that when A' and A''' are not present then at least one of A and A' is an oxide (-O<；SUP>；-<；/SUP>；).
