Stepwise complexation of Ni(II) and Cu(II) ions by 6,6 '-C-spirobi(cyclam) (cyclam=1,4,8,11-tetraazacyclotetradecane), L-1. Syntheses and redox chemistry of [M(H2L1)]X-4 (M = Cu2+, Ni2+), [Cu-2(L-1)]X-4, and [CuNi(L-1)]X-4 (X = ClO4-) and the X-ray crystal structure of [Cu-2(L-1)](ClO4)(4)