Abstract The new heptazine based compounds Sr [H 2 C 6 N 7 O 3] 2· 4H 2 O and Sr [HC 6 N 7 (NCN) 3]· 7H 2 O have been synthesized by metathesis reactions in aqueous solution. Crystal structures were studied by single-crystal X-ray diffraction and Rietveld refinement. Strontium cyamelurate tetrahydrate exhibits distorted zigzag strands embedding Sr 2+ ions surrounded by crystal water molecules (Fdd2, a= 1194.0 (17), b= 6358.14 (97), c= 602.73 ...