The nonmetal borate [H3N(CH2)(7)NH3][B7O9(OH)(5)]center dot H2O (1) was prepared via a neat reaction of 1,7-diaminoheptane with excess boric acid under mild nonhydrothermal conditions. Single-crystal X-ray characterization of 1 revealed a new isomer of the heptaborate anion, B7O9(OH)(5)(2-). The heptaborate anion in 1 is comprised of four fused (BO)(3) rings sharing three four-coordinate boron atoms and a single three-coordinate oxygen atom. This anion is a structural isomer of another recently described heptaborate anion, consisting of a chain of three (BO)(3) rings. Compound 1 crystallized in the triclinic space group P (1) over tilde with a = 9.3266(17) angstrom, b = 10.1222(19) angstrom, c = 10.847(2) angstrom, alpha = 89.422(2)degrees, beta = 82.349(2)degrees, gamma = 75.158(2)degrees, V = 980.7(3) angstrom(3), and Z = 2.