The addition of dipyridylamine to bis(3-cyano-2,4-pentanedionato)copper(II) Cu(NC-acac)(2), induces changes in the mode of interaction and the conformation of the NC-acac(-) anion. The structure of the resulting binuclear compound was determined from a single microcrystal (monoclinic, space group P2(1), a = 7.894(7) Angstrom, b = 25.550(24) Angstrom, c = 11.661(13) Angstrom, beta = 106.10(8)degrees, Z = 2, R(1) = 0.0564, (w)R(2) = 0.1197). In the addition compound {[Cu(NC-acac)dipyamH](NC-acac)}2 when the NC-acac(-) acts as a chelating and bridging ligand, it assumes the commonly observed U(Z,Z) conformation, while behavior as weakly N-coordinated unidentate counteranion imposes the rarely encountered S(Z,E) conformation. In the [Cu(NC-acac)dipyamH] (NC-acac)] entities one of the copper(II) centers is a 4 + 2 Jahn-Teller complex while the other is a square-based pyramid.