crystal Structure and Electrospray Ionization Mass Spectrometry, Electron Paramagnetic Resonance, and Magnetic Susceptibility Study of [Cu2(ascidH2)(1,2-.mu.-CO3)(H2O)2].cntdot.2H2O, the Bis(copper(II)) Complex of Ascidiacyclamide (ascidH4), a Cyclic Peptide Isolated from the Ascidian Lissoclinum pa