. "In formula (IV), M is hydrogen or a metal ion, such as sodium or potassium; X1 and X2 are independently selected from ammonia, amino, nitro, C1???C6 alkoxy, hydroxy, chloride, bromide, or iodide; Z1 is C(R1)R2, wherein R1 and R2 are independently hydrogen or C1???C6 straight chain or branched alkyl; Z2 is C(R3)R4, wherein R3 and R4 are independently hydrogen or C1???C6 straight chain or branched a" . . . .