The present disclosures provides isolated or purified compounds, each of which bind to a metal atom. Generally, the compounds are small in size (e.g, molecular weight of less than about 1 kDa) and peptidic in nature, inasmuch as the compounds comprise amino acids. In some embodiments, the compound comprises a structure of Formula I:M1-P1-M2-P2 wherein each of P1 and P2 is a peptide comprising at least two amino acids, M1 is a first metal binding moiety comprising a substituted imidazolone ring, M2 is a second metal binding moiety comprising a substituted oxazolone ring, and wherein M1 and M2 bind to a single metal atom. Also provided are related complexes, conjugates, cells which synthesize the compounds of the present disclosures, substantially homogenous cultures thereof, kits and compositions, and methods of making or using the materials of the present disclosures.