In depth investigation of the synthesis, structural, and spectroscopic characterization of a high pH binary Co(II)-N,N-bis(phosphonomethyl)glycine species. Association with aqueous speciation studies of binary Co(II)-(carboxy)phosphonate systems

► pH-specific synthesis affords new high pH structural variant in Co(II)-NTA2P system. ► (NH4)3[Co(C4H6O8NP2)(H2O)2]·4H2O can be precursor to new Co(II)-organophosphonates. ► Aqueous speciation reflects diversity of Co(II) species in Co(II):NTAxP systems. ► Structure-activity in Co(II)-NTA2P system link high and low pH structural variants. ► pH-dependent reactivity supports magnetostructural relations in Co(II)-NTA2P system.