The hexaaza macrocyclic ligand 3,6,9,16,19,22-hexaaza-27,28-dioxatricyclo[22.2.1.1(11,14)]octacosa-1(26),11,13,24-tetraene (BFBD), prepared via 2+2 condensation of 2,5-diformylfuran with diethylenetriamine, followed by reduction with NaBH4, forms a variety of cationic species including mono- through hexaprotonated forms of the macrocycle in aqueous solution. These cationic hosts recognize certain substrates such as oxalate, malonate, and pyrophosphate anions. Formation constants measuring this recognition are reported for all species found from the potentiometric studies and are compared with those of the analogous ligand 1,4,7,13,16,19-hexaaza-10,22-dioxacyclotetracosane (OBISDIEN). Two binary complexes (H6BFBD-C2O4)Cl-4 . 4H(2)O, 1, and (H5BFBD-H2P2O7)Cl-3 . 5H(2)O, 2, have been characterized by single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic system, space group P2(1)/n, with a = 6.2630(10) Angstrom, b = 19.682(3) Angstrom, c = 13.870(2) Angstrom, beta = 91.210(10)degrees, and Z = 2, and complex 2 crystallizes in the triclinic system, space group P (1) over bar, with a = 12.675(5) Angstrom, b = 12.792(5) Angstrom, c = 12.868(5) Angstrom, alpha = 97.44(3)degrees, beta = 115.03(3)degrees, gamma = 105.40(3)degrees, and Z = 2. The X-ray crystal structure results reveal that the binding of anionic substrates to protonated BFBD is through hydrogen bonds between negatively charged oxygens of the substrates and protonated, positively charged amino nitrogens of BFBD.