The electronic and electron spin resonance spectra of complexes of the copper(II) ion with di-(2-pyridyl)amine

New and more extensive spectroscopic data (electronic, e.s.r., and i.r.) for complexes CuL2XY and CuL2Z2[L = di-(2-pyridyl)amine; X–= I–, NCS–, and Y–= ClO4–; Z–= ClO4–, PF6–, Cl–, Br–, I–, NO2–, and NO3–) are evaluated in terms of recent advances made in the understanding of the relationship between spectra and structure for copper(II) complexes. CuL2(ClO4)2 is isomorphous with ZnL2(ClO4)2 and contains non-planar CuL22+ ions as does CuL2(PF6)2, whereas CuL2(NO3)2 and CuL2Br2 are tetragonal complexes with planar CuL22+ units. There is good evidence that [CuL2Cl]Cl is trigonal bipyramidal but the nature of CuL2I2 is less certain. The remaining complexes are believed to contain six-co-ordinate copper(II) with cis-bis(di-2-pyridylamine)copper(II) units. Evidence is presented to suggest that a novel dimeric complex is [(dipyam)2(HF2)Cu(dipyam)Cu(HF2)(dipyam)2]-(PF6)2 with one bridging di-(2-pyridyl)amine group.