The syntheses and crystal structures of the first copper(I) phosphonate, Cu-2(H3L)(bipy)(2).2H(2)O 1 (H5L = C4HO3N(CH2PO3H2)2), which is also the first example of metal phosphonates formed by a type of organic reaction, and a novel luminescent Mn(II) squarate diphosphonate, {Mn[NH(CH2PO3H)(2)](H2O)(2)}(2){Mn(C4O4)(H2O)(4)}.(C4H2O4) 2, have been reported. The structure of 1 features a layer architecture in which the Cu(I) centers are three coordinated, and the newly formed ligand acts as a bidentate metal linker. Compound 2 is composed of 1D chains of Mn[NH(CH2PO3H)(2)](H2O)(2), 1D chains of {Mn(C4O4)(H2O)(4)}, as well as the neutral squaric acid molecules. These three types of building units are interconnected via hydrogen bonding.